Machine learning has become ubiquitous in materials modelling and now routinely enables large-scale atomistic simulations with quantum-mechanical accuracy. However, developing machine-learned interatomic potentials requires high-quality training data, and the manual generation and curation of such data can be a major bottleneck. Here, we introduce an automated framework for the exploration and fitting of potential-energy surfaces, implemented in an openly available software package that we call autoplex (`automatic potential-landscape explorer'). We discuss design choices, particularly the interoperability with existing software architectures, and the ability for the end user to easily use the computational workflows provided. We show wide-ranging capability demonstrations: for the titanium-oxygen system, SiO2, crystalline and liquid water, as well as phase-change memory materials. More generally, our study illustrates how automation can speed up atomistic machine learning -- with a long-term vision of making it a genuine mainstream tool in physics, chemistry, and materials science.

https://doi.org/10.48550/arXiv.2412.16736

The advancement of synthetic cells as drug delivery devices hinges on the development of targeting strategies, in particular the controlled synthesis of biomolecules in-situ using a deeply penetrative stimulus. To address this, we have designed spherical nucleic acids comprising DNA promoter sequences decorating magnetic nanoparticle cores. By harnessing the heat dissipated from magnetic hyperthermia (a clinically-approved anticancer therapy) we tightly controlled cell-free protein synthesis. We then deployed a tissue phantom that is impenetrable by current activation methods to demonstrate the potential of this technology for the remote control of synthetic cells using deeply tissue-penetrating magnetic fields. This paves the way for targeting and controlling the in-situ synthesis of biomolecules deep within the body.

https://doi.org/10.1101/2024.08.21.608917

The transition-metal dicyanides M(CN)2 (M = Zn, Cd) are amongst the most important negative thermal expansion (NTE) materials known, favoured for the magnitude, isotropy, and thermal persistence of the NTE behaviour they show. The conventional picture of the NTE mechanism in this family is one of correlated rotations and translations of M(C/N)4 polyhedra acting to draw the diamondoid network of M--CN--M linkages in on itself. An implication of this mechanism is increased transverse vibrational motion of C and N atoms relative to the isotropic displacements of M atoms, which act as anchors. Here, we use a combination of neutron total scattering measurements and \emph{ab initio} calculations to reassess the vibrational behaviour of the M(CN)2 family. We find that M, C, and N atoms all exhibit similar degrees of local thermal motion, such that the cyanide linkages behave as pseudo-springs connecting M…M pairs. This interpretation leads us to uncover a `hidden' dispersion in the M(CN)2 phonon dispersions, closely related to that of diamond and silicon themselves. By virtue of this mapping, a simple geometric model based on the competing energy scales of network stretching and flexing -- long applied to interpret NTE modes in C and Si -- turns out to capture the key NTE physics of M(CN)2, especially at low temperatures. Our study highlights the potential insight gained by coarse-graining the complex lattice dynamics of framework materials in terms of what we call `framework modes' -- the correlated distortions of the underlying network structure itself.

https://doi.org/10.48550/arXiv.2406.11381

Spontaneous redox shuttling at silicon is very rare, primarily reflecting the thermodynamic challenges associated with reduction processes for lighter p-block elements. Here we show that the reactions of boryl-substituted silylene {PhC(tBuN)2}Si{B(NDippCH)2} with an organo-azide proceed through a Si(IV)-Si(II)-Si(IV) series of redox processes involving both oxidative and reductive ligand migration steps. Each of the isomeric compounds related through this reaction manifold is isolable (and can be structurally characterized by X-ray crystallography), with the overall free energy profile being close to thermo-neutral. Broader studies within group 14 imply that this redox shuttling is unique to silicon, and that reductive ligand migration also plays a role in O-atom insertion chemistry.

https://doi.org/10.1002/anie.202505872

Binuclear lanthanide complexes bearing nitrophenol, azophenol and azide chromophores can be reduced to the amine, giving rise to dramatic changes in the luminescence behavior. Such reductions can be achieved using enzymes as well as by chemical means. The tunable redox response and imaging modalities of these versatile complexes have the potential to open up new approaches to redox sensing.

https://doi.org/10.1002/chem.202404748

A complete series of CsPb(ClxBr1−x)3 mixed-halide perovskites with x = 0–1 in small steps is reported, and their structural and optical properties characterised. A comparison of synthetic approaches shows that mechanosynthesis yields the most robust data across the compositions, avoiding solvent inclusion or miscibility gaps. The resulting data library, including some hitherto unreported compositions, can serve as a benchmark for future computational modelling.

https://doi.org/10.1039/D5CC00735F

An organometallic Al(III)K(I) catalyst shows exceptional control in the epoxide/anhydride ring opening copolymerization (ROCOP), producing high molecular weight polyesters (Mn ∼ 100 kg·mol−1). The catalysis is highly effective using cyclohexene oxide, cyclopentane oxide, substituted cyclohexene oxide, and butylene oxide, each combined with phthalic anhydride. The polyesters show entanglement molecular weights, determined by oscillatory shear rheology, from 13 to 50 kg·mol−1 with cyclopentene and substituted cyclohexene moieties being particularly effective (highly entangled). The lead polyesters show high glass transition temperatures (94 °C < Tg < 137 °C), high tensile strengths (40 MPa < σ < 47 MPa) and tensile modulii (0.6 GPa < Ey < 0.9 GPa); their properties are similar to polystyrene. The polyesters are all recyclable by repeated cycles of compression molding, and show equivalently high thermal-mechanical performances even over repeated recycles.

https://doi.org/10.1002/anie.202505070

Lanthanide complexes of DOTA monoesters bearing nitrobenzyl and nitroimidazole groups are shown to be converted to the corresponding DOTA complexes under chemical and enzymatic conditions, giving rise to favorable changes in the luminescence properties of the europium and terbium complexes and relaxometric properties of the gadolinium complexes. The nitroimidazole complexes are converted more rapidly than their nitrobenzyl and benzyl analogues. We propose that activation of these complexes may occur by ester cleavage rather than nitro reduction and fragmentation since complexes bearing a simple benzyl group may also be cleaved under the same conditions, albeit more slowly.

https://doi.org/10.1021/acs.inorgchem.5c00199

Known boron carbonyl complexes either exploit very high Lewis acidity or a low oxidation state boron centre in order to capture CO. By contrast, we report a carbonyl complex featuring a simple tri-coordinate borane, characterized by a Lewis acidity which is only marginally higher than B(NMe2)3. {(Ph2P)xanth}3B features a solid-state structure in which two of the three B-bound xanth(PPh2) units are projected above the BC3plane, generating an up,up,down conformation. Quantum chemical methods, however, reveal that the alternative up,up,up alignment, characterized by a cage-like geometry and enhanced intramolecular non-covalent interactions, is favoured significantly in silico (by ca. 33.0 kcal mol-1). While this conformation is optimal for binding polar C3-symmetric H-bond donors such as NH3 (and related guests such as H2O and MeNH2) the binding of essentially non-polar substrates such as CO would be expected to be weak at best. However, exposure of {(Ph2P)xanth}3B to CO under mild conditions (1 bar, 25°C) reversibly yields {(Ph2P)xanth}3B·CO, a tractable cage-like borane carbonyl adduct featuring a central BCO moiety shrouded by xanth(PPh2) moieties. Dispersion forces are critical to substrate binding: the two binding modes in which the B-bound CO guest is located inside/outside the host cage differ in energy by 59.5 kcal mol-1.

https://doi.org/10.1002/anie.202501774

The integration of an external magnetic field into electrocatalysis, termed magneto-electrocatalysis, can target efficiency challenges in the oxygen evolution reaction (OER). Reaction rates can be enhanced through improved mass transport of reactants and products, manipulation of spin states, and lowered resistance. The OER is a kinetic bottleneck in electrocatalytic water splitting for sustainable hydrogen fuel. Previous studies lack comprehensive analyses and consistent reporting of magnetic field effects, resulting in varied interpretations. To establish optimized and reliable systems at larger scales, significant research advancements are required. This perspective explores the complex impact of magnetic fields on OER, emphasizing the interplay between various mechanisms such as spin-polarization of oxygen intermediates, Lorentz force-induced magnetohydrodynamics, and magnetoresistance. Here, how experimental design – such as electrode magnetism, shape, positioning, and reactor setup – can significantly influence these mechanisms is highlighted. Through a comprehensive review of current studies, major knowledge gaps and propose methodologies are identified to improve experimental reproducibility and comparability. This article aims to guide researchers toward the development of more efficient, scalable systems that leverage magnetic fields to enhance water splitting to push forward commercial green hydrogen production.

https://doi.org/10.1002/smll.202500001

Cyclic anhydride and epoxide ring-opening copolymerization is a versatile and controlled route to make polyesters, gaining attention in different application sectors. But so far, the chemical recycling of these polyesters to cyclic monomers is under-explored. Here, the catalytic chemical recycling of aliphatic polyesters to selectively form 16- and 18-membered lactones is presented. The recycling reactions are catalyzed using commercial tin(II) octoate and conducted in the polymer melt (230 °C) resulting in high conversions to the macrolactones (>90%). The recycled macrolactones undergo catalyzed ring-opening polymerizations to produce polyesters with equivalent properties to the virgin materials.

https://doi.org/10.1002/anie.202423478

The homogeneous catalytic functionalization of methane is extremely challenging due to the relative nonpolarity and high C–H bond strength of this hydrocarbon. Here, using catalytic quantities (10 mol %) of CpMn(CO)3 or Cp*Re(CO)3, the conversion of methane and benzene C–H bonds to C–Be and H–Be bonds by CpBeBeCp has been achieved under photochemical conditions. Possible intermediates in the beryllation reactions─trans-bis(beryllyl)-manganese and -rhenium complexes─were also isolated. Quantum chemical calculations indicate that the inherent properties of the beryllyl ligands─which are powerfully σ-donating and feature highly Lewis acidic beryllium centers─are decisive in enabling methane functionalization by these systems.

https://doi.org/10.1021/jacs.5c02179

Reversible lithium intercalation into the van der Waals phase V2Te2O, forming new phases LixV2Te2O with x approaching 2, is reported using both chemical and electrochemical methods. The progress of each reaction was followed using powder X-ray diffraction and the crystal structure of the intercalated phase with x = 1, LiV2Te2O, was refined using powder neutron diffraction. The intercalated Li ions occupy vacant pseudo-octahedral sites and the unit cell expands on reduction with no change in symmetry. The lithium ions can be removed chemically or electrochemically, making this the first known oxytelluride to undergo reversible lithium intercalation.

https://doi.org/10.1039/D5DT00159E

The reactivity of an N-heterocyclic boryloxy (NHBO) ligated aluminyl compound has been harnessed for main-group-mediated dehydrogenative dual activation of ammonia. The Al(I) system K[{(HCDippN)2BO}2Al] reacts with excess NH3 to give the Al(III) bis(amide) K[{(HCDippN)2BO}2Al(NH2)2] and in the process generates H2. The initial stage of the reaction proceeds via formal N−H oxidative addition at Al(I) (via a coordination/proton shuttling sequence) to give an aluminium(III) primary amido hydride. Subsequent protonolysis of the strongly hydridic Al−H bond selectively yields the corresponding aluminium bis(amide) and H2. This step occurs without competing protolytic ligand loss – exploiting the limited basicity of the supporting [(boryl)O]− donors. In terms of amide transfer reactivity, the utility of K[{(HCDippN)2BO}2Al(NH2)2] in delivering one or both equivalents of [NH2]− to electrophilic substrates (HBpin, CO2 and Ph2CO) has been demonstrated.

https://doi.org/10.1002/anie.202502326

Combining experiment and theory, the mechanisms of H2 activation by the potassium-bridged aluminyl dimer K2[Al(NON)]2 (NON=4,5-bis(2,6-diisopropylanilido)-2,7-di-tertbutyl-9,9-dimethylxanthene) and its monomeric K+-sequestered counterpart have been investigated. These systems show diverging reactivity towards the activation of dihydrogen, with the dimeric species undergoing formal oxidative addition of H2 at each Al centre under ambient conditions, and the monomer proving to be inert to dihydrogen addition. Noting that this K+ dependence is inconsistent with classical models of single-centre reactivity for carbene-like Al(I) species, we rationalize these observations instead by a cooperative frustrated Lewis pair (FLP)-type mechanism (for the dimer) in which the aluminium centre acts as the Lewis base and the K+ centres as Lewis acids. In contrast to previous theoretical work on this precise system by Schaefer and co-workers, the potassium ions are shown to play explicit roles in stabilizing a nascent 2-bridging hydride, formed by heterolytic H−H bond cleavage (with accompanying protonation of the aluminium-centred lone pair). K-to-Al hydride “rebound” into the vacant aluminium-centred p-orbital then completes the net addition of H2 via sequential H+/H− transfer. The experimentally determined kinetic isotope effect (kH/kD=2.6) reflects a high degree of bond activation in the transition state (as predicted quantum chemically).

https://doi.org/10.1002/chem.202500095

The reactivity of group 13 anions of the form [(NON)E]− (NON=4,5-bis(2,6-diisopropylanilido)-2,7-di-tert-butyl-9,9-dimethyl-xanthene, E=Al, Ga, In) towards Fe(CO)5 has been investigated. In the case of the aluminyl system, both reaction outcome and product structure are highly sensitive to the availability of the potassium counterion; sequestration by 18-crown-6 is necessary to yield a species featuring a direct, unsupported Al−Fe bond. 2.2.2-Cryptand, by contrast, yields a species featuring bridging carbonyl ligands, while the use of no sequestering agent at all leads to isocarbonyl bridging to aluminium. Owing to their lower oxophilicity, the heavier congeners gallium and indium more straightforwardly deliver Fe−E bonded adducts (E=Ga, In). The series of trielyl iron complexes has been interrogated by structural and computational analyses, as well as by IR and Mössbauer spectroscopies, revealing a consistent shift in bond polarity and electron richness at iron as group 13 is descended. This in turn is consistent with the diminishing donor strength of the trielyl ligand with increasing atomic number.

https://doi.org/10.1002/chem.202404451

The diverse solid-state structures and solution-phase dynamics of both neutral and heterometallic s-block “ate” complexes of the heavier alkaline earth metals (Ae; Ca–Ba) supported by a chelating and flexible di(amido)siloxane ligand ([NON-DippL]2− = [O(SiMe2NDipp)2]2−) are described, enabling comparison with those of closely related di(amido) ligands based on either flexible aliphatic or rigid xanthene-based backbones. Three dimeric alkaline earth complexes [(NON-DippL)Ae]2 (Ae = Ca (2), Sr (3) and Ba (4)) which feature a κ3-N,O,N′-κ1-N′-tridentate coordination mode were prepared from protonolysis reactions between NON-DippLH2 with Image ID:d5dt00044k-t1.gif (Ae = Ca, Sr and Ba); N′′ = [N(SiMe3)2]−. In tetrahydrofuran, these complexes were readily converted into the monomeric adducts [(NON-DippL)Ae(thf)n] (n = 2, Ae = Ca (5); n = 3, Ae = Sr (6) and Ba (7)). Heterometallic Ae/K amide “ate” complexes were afforded through two routes: reaction of previously reported [(NON-DippL)Mg]2 (1) with two equivalents of KN′′ at elevated temperatures resulted in [(NNO-DippL)Mg(μ-N′′)K]n (8; NNO-DippL = [OSiMe2NDippSiMe2NDipp]2−), whereas the equimolar reaction of NON-DippLH2 with Image ID:d5dt00044k-t2.gif led to [(NON-DippL)Ae(μ-N′′)K]n (Ae = Ca (9), Sr (10) and Ba (11)). Complexes 8–11 exist as one-dimensional coordination polymers propagated by K+–aryl π-facial interactions in the solid-state. The mixed amide/siloxide “NNO” ligand in 8 results from a 1,3-silyl retro-Brook rearrangement of the original di(amido)siloxane ligand, while the larger Ae2+ congeners readily accommodate the coordination of KN′′ with the di(amido)siloxane ligand retaining a κ3-N,O,N′-tridentate motif in 9–11. Finally, the solution-phase behaviour of 8–11 in both toluene and thf were investigated indicating the reversible dissociation of KN′′ from 9–11 and the thermodynamic parameters of this process were elucidated.

https://doi.org/10.1039/D5DT00044K

Bimetallic 1,8-bis(silylamido)naphthalene alkaline earth complexes [(R3L)Ae]2 ([R3L]2– = [1,8-{(R3Si)N}2C10H6)]2–, where R3 = Ph2Me, Ae = Ca (1), Sr (2), and Ba (3); R3 = Ph3, Ae = Ca (4), Sr (5), and Ba (6) were prepared via protonolysis reactions of the phenyl-substituted proligands Ph3LH2 and Ph2MeLH2 with [AeN″2]2 (N″ = [N(SiMe3)2]−) in benzene. X-ray crystallographic analysis showed that 1, 2, and 4 crystallize as nitrogen-bridged dimers. Conversely, 5 and 6 display a naphthalene-bridged motif, while the structure of 3 is intermediate between the two distinct classes. NMR spectroscopic analysis of isolated samples of 1–6 in thf-d8 confirmed their conversion into the monomeric thf-d8 adducts [(R3L)Ae(thf-d8)n]; crystallographic verification of the structural motif was provided by the X-ray crystal structure of [(Ph3L)Sr(thf)3] (7). The structural range of dimers 1–6 was influenced by the electron-withdrawing nature of the phenyl substituents of the ligand and the ability to form “soft” multihaptic π-facial interactions with the metal ions, which was preferential for the larger Sr2+ and Ba2+ cations as well as the relative strength of the metal-N bonds. This has been rationalized through complementary computational studies. This work provides insight into the structure and bonding preferences of heavy alkaline earth complexes with rigid bis(amido) ligands.

https://doi/10.1021/acs.organomet.4c00479

In homogeneous catalysis, uncovering structure–activity relationships remains very rare but invaluable to understand and rationally improve performances. Here, generalizable structure–activity relationships apply to a series of heterodinuclear polymerization catalysts featuring Co(III) and s-block metals M(I/II) (M=Na(I), K(I), Ca(II), Sr(II), Ba(II)). These are shown to apply to polycarbonate production by the ring-opening copolymerizations (ROCOP) of cyclohexene oxide (CHO) and carbon dioxide (CO2), conducted at high (20 bar) and low (1 bar) CO2 pressures, and to polyester production by copolymerization of cyclohexene oxide and phthalic anhydride (PA). For the CHO/PA and high-pressure CHO/CO2 copolymerizations, activity increases exponentially with s-block metal acidity peaking at the Co(III)K(I) catalyst, whilst for the low-pressure CHO/CO2 copolymerization it increases linearly to the same metal combination. The polymerization kinetics fit second order rate laws and the correlations support dinuclear metallate mechanistic hypotheses. These relationships help understand and identify key metal complex structural features in synergic polymerization catalysis.

https://doi.org/10.1002/anie.202422497

The delocalization length of charge carriers in organic semiconductors influences their mobility and is an important factor in the design of functional materials. Here, we have studied the radical anions of a series of linear and cyclic butadiyne-linked porphyrin oligomers using CW-EPR, 1H Mims ENDOR and NIR/MIR spectroelectrochemistry together with DFT calculations and multiscale molecular modeling. Low-temperature hyperfine EPR spectroscopy and optical data show that polarons are delocalized nonuniformly over about four porphyrins with most of the spin density on just two units even in the cyclic structures, in which all porphyrin sites are identical. Room temperature CW-EPR spectra indicate a larger spatial distribution of spin density on the EPR time scale. We introduce a combined molecular dynamics simulations and DFT approach to demonstrate that dynamic migration of delocalized polarons can occur in porphyrin oligomers and that this fully accounts for the apparent spin density distribution at room temperature. This method is a powerful tool in both the study and development of molecular wires and molecular electronics.

https://doi.org/10.1021/jacs.4c14161

The reaction chemistry of an unprecedented ‘inorganic cumulene’ – featuring a five-atom BNBNB chain – towards C[double bond, length as m-dash]O (and related) multiple bonds is disclosed. In marked contrast to related all-carbon systems, the intrinsic polarity of the BNBNB chain (featuring electron-rich nitrogen and electron-deficient boron centres) enables metathesis chemistry with electrophilic heteroallenes such as CO2 and with organic carbonyl compounds. Transfer of the borylimide unit to [CO], [CS], [PP{(NDippCH2)2}] and [C(H)Ph] moieties generates (boryl)N[double bond, length as m-dash]C[double bond, length as m-dash]X systems (X = O, S, PP{(NDippCH2)2}, C(H)Ph), driven thermodynamically by B–O bond formation. Pairwise exchange of O and {(HCDippN)2}BN fragments occurs via consecutive [2+2] cyclo-addition/cyclo-reversion steps. An isolable complex of stoichiometry K[(boryl)NB(O)OC(H)Ph], formed via [2+2] cycloaddition to [(boryl)N[double bond, length as m-dash]B[double bond, length as m-dash]O]− can be shown to be an intermediate in the formation of (boryl)N[double bond, length as m-dash]C(H)Ph, and provides corroborating evidence for a DFT-calculated mechanism proceeding via a ‘bora-Wittig’ mechanism.

https://doi.org/10.1039/D4SC07487D

We describe two contrasting transmetallation reactions between the gold(I) cyaphide complex, Au(IDipp)(CP) (IDipp = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene), and low oxidation state main-group and transition-metal complexes. The reactivity observed highlights the pseudo-halide character of the cyaphide ion.

https://doi.org/10.1039/D4CC06131D

A dynamic zinc(II) metalloporphyrin axle-containing [2]rotaxane with a heteroditopic macrocycle component is shown to selectively recognise and optically sense lithium halide (LiX) ion-pair species. 1H NMR and UV-visible absorption experiments demonstrate a strong macrocycle pyridyl⋯Zn(II) metalloporphyrin axle interaction which results in a marked co-conformational bias in the free [2]rotaxane host system. Extensive 1H NMR cation, anion and ion-pair titration experiments demonstrate the binding of lithium halide ion-pairs disrupts the inter-component mechanical bond interaction, wherein dynamic macrocycle shuttling to an axle triazole station enables co-operative axle-separated LiX ion-pair recognition and the selective optical sensing of lithium halide salts.

https://doi.org/10.1039/D4DT03026E

High-valent nickel species are implicated as intermediates in industrially relevant chemical transformations and in the catalytic cycles of metalloenzymes. Although a small number of tetravalent NiX4 complexes have been crystallographically characterized, higher nickel valence states have not been identified. Here we report a stable, crystalline NiX6 complex, Ni(BeCp)6 (1; cyclopentadienyl anion (Cp)), formed by the insertion of zerovalent nickel into three Be–Be bonds. This 16-electron species features an inverted ligand field, is diamagnetic, and exhibits C3v symmetry, on account of the lifting of Ni 4p-orbital degeneracy in this molecular geometry. Single-crystal X-ray diffraction and quantum chemical calculations both reveal a toroidal band of electron density perpendicular to the C3 axis of the complex, which may be attributed to delocalized, multicenter aromatic NiBe6 bonding.

https://doi.org/10.1021/jacs.4c12125

Stimuli-responsive synthetic ionophores allow for spatial and temporal control over ion transport, with promise for applications in targeted therapy. Relay transporters have emerged as a new class of ion transporters - these are anchored carriers that sit in both leaflets of the bilayer and mediate transport across the membrane by passing ions between them. The relays are themselves membrane impermeable, and so must be incorporated into the membrane during vesicle preparation. Here we show that relay transporters can be delivered to both sides of the membrane of vesicles using a synthetic flippase. By incorporating an aryl azopyrazole photo-switch into the movable arm of the relay transporters the ion transport activity can be very efficiently and reversibly switched between off and on states. This control is achieved by extension and contraction of their movable arms via photo-isomerization of the central aryl azopyrazole moiety, hence modulating the ability of the relays to pass ions across the membrane.

https://doi.org/10.1002/anie.202421580

The ring-opening copolymerization (ROCOP) of epoxides with CO2 or anhydrides is a promising strategy to produce sustainable polycarbonates and polyesters. Currently, most catalysts are reliant on scarce and expensive cobalt as the active center, while more abundant aluminum and iron catalysts often suffer from lower activities. Here, two novel heterodinuclear catalysts, featuring abundant Al(III), Fe(III), and K(I) active centers, are synthesized, and their performance in the polymerization of four different monomer combinations is compared to that of their Co(III) analogue. The novel Al(III)K(I) catalyst exhibits outstanding activities in the cyclohexane oxide (CHO)/CO2 ROCOP, and at 1 bar CO2 pressure it is the fastest aluminum-based catalyst reported to date. The M(III) site electronics for all three catalysts, Al(III)K(I), Fe(III)K(I), and Co(III)K(I), are measured using IR and NMR spectroscopy, cyclic voltammetry, and single crystal X-ray diffraction. A correlation between M(III) electron density and catalytic activity is revealed and, based on the established structure–activity relationship, recommendations for the future catalyst design of abundant Al(III)- and Fe(III)-based catalysts are made. The catalytic performances of both Al(III)K(I) and Fe(III)K(I) are further contextualized against the relative elemental abundance and cost. On the balance of performance, abundance, and cost, the Al(III)K(I) complex is the better catalyst for the carbon dioxide/epoxide ROCOP, while Fe(III)K(I) is preferable for anhydride/epoxide ROCOP.

https://doi.org/10.1021/acs.inorgchem.4c04430

Reaction between Sr2Mn0.5Ir0.5O4 and CaH2 or LiH yields the iridium-containing oxyhydride phases Sr2Mn0.5Ir0.5O3.25H0.75 or Sr2Mn0.5Ir0.5O2.66H1.33, respectively. Analysis of Mn K-edge XANES data indicate the presence of Ir3+ centers in these oxyhydride phases, whose low-spin d6 configuration is consistent with the “covalent stabilization” of the metastable oxyhydride phases, as seen previously in analogous ruthenium and rhodium containing materials. Neutron powder diffraction data indicate the hydride ions are located exclusively within the “equatorial” anion sites of Sr2Mn0.5Ir0.5O3.25H0.75. In contrast, hydride ions are observed on both the equatorial and axial anion sites of Sr2Mn0.5Ir0.5O2.66H1.33. This highly unusual anion distribution is attributed to a combination of the strong trans-influence of Ir–H σ-bonds and the stabilization of fac-IrO3H3 centers by spin–orbit coupling effects. Magnetization data indicate that Sr2Mn0.5Ir0.5O4 and Sr2Mn0.5Ir0.5O3.25H0.75 adopt spin glass states at low temperature, behavior which is attributable to the cation disorder in Sr2Mn0.5Ir0.5O4 and the cation and anion disorder in Sr2Mn0.5Ir0.5O3.25H0.75. In contrast, magnetization data collected from Sr2Mn0.5Ir0.5O2.66H1.33 show no evidence of any magnetic phase transition down to 5 K, consistent with the dilution of the magnetic network by the introduction of diamagnetic Ir3+ on the formation of the oxyhydride phase.

https://doi.org/10.1021/acs.inorgchem.4c04057

We report a convenient synthesis of the zinc–boryl complex (NacnacMes)ZnBpin under mild conditions via formal disproportionation of bis(pinacolato)diboron(4), aided thermodynamically by B–O bond formation. This species can be isolated both base-free and as the DMAP adduct (NacnacMes)Zn(DMAP)Bpin and crystallographically characterised in the latter form. Onward reactivity of the base free zinc boryl complex with CO2 occurs reductively, yielding further B–O bonds as well as CO gas. The strength of this driving force can then be harnessed in the reaction between (NacnacMes)ZnBpin and a Zn–O bonded species (NacnacMes)ZnOB{(NDippCH)2}, which yields the metal–metal bonded dimer [(NacnacMes)Zn]2, the overall formation of which utilizes a diboron(4) species as the stoichiometric reductant of Zn(II) to Zn(I).

https://doi.org/10.1039/D4SC06389A

Molecular chains of two-coordinate carbon atoms (cumulenes) have long been targeted, due to interest in the electronic structure and applications of extended π-systems, and their relationship to the carbon allotrope, carbyne. While formal (isoelectronic) B═N for C═C substitution has been employed in two-dimensional (2-D) materials, unsaturated one-dimensional all-inorganic “molecular wires” are unknown. Here, we report high-yielding synthetic approaches to heterocumulenes containing a five-atom BNBNB chain, the geometric structure of which can be modified by choice of end group. The diamido-capped system is bent at the 2-/4-positions, and natural resonance theory calculations reveal significant contributions from B═N(:)–B≡N–B resonance forms featuring a lone pair at N (consistent with observed N-centered nucleophilicity). Molecular modification to generate a linear system best described by a B═N═B═N═B resonance structure involves chemical transformation of the capping groups (using B(C5F5)3) to enhance their π-acidity and conjugate the N-lone pairs.

https://doi.org/10.1021/jacs.4c13231

Complexation of the green bismuthinidene (RBi) with two equivalents of a highly fluorinated aryl iodide at low temperature allows the crystallographic identification of an unstable red species that can be regarded as an intermediate in an overall Bi(I) → Bi(III) oxidation process. Both C–I bonds are orientated toward the filled 6p orbital of bismuth (Bi–I distances 3.44–3.52 Å), leading to an elongation of the C–I bonds by 0.05 and 0.07 Å. Density functional theory (DFT) calculations confirm that the Bi(I) center is indeed acting as an electron donor, establishing two strong and directional halogen bonds. The color change from green to red upon halogen bond formation is a consequence of the energetic stabilization of a Bi(I) lone pair by interactions with the sigma-holes of the halogen bond donors. Overall, this study presents the first structural proof of bismuth, and more generally of heavy organopnictogen(I) compounds, acting as halogen bond acceptors.

https://doi.org/10.1021/jacs.4c11901

IThe development of efficient and cost-effective CO2 adsorbents is crucial for carbon capture from ultradilute conditions. Amine-grafted mesoporous materials prepared by silane chemical reactions are well-known CO2 adsorbents with high thermal stabilities, but their capacities for direct air capture (DAC) are usually restricted by low amine loadings and CO2 capture capacity. Herein, we present an in-situ amine grafting method that enables high amine loadings by in-situ grafting initial ultrathin LDHs nanosheets in an organic solvent. For in-situ triamine grafted Mg2Al-CO3 LDH (IN-TRI-LDH) amine loading is boosted to 5.91mmol N g−1 and ultimately achieving a remarkable adsorption capacity of 0.98 mmol g−1 at 25°C and 400 ppm CO2, nearly double that of the amine-LDHs grafted through a conventional two-step process. A further 22 % enhancement of the CO2 capacity is observed under 20 RH%. In addition, IN-TRI-LDH maintains a working capacity of 0.85 mmol g−1 at a low desorption temperature of 70 °C. A 50 adsorption–desorption cyclic test under simulated humid DAC conditions shows minimal performance degradation. Such a sufficient working capacity and low desorption temperature reduces the thermal energy consumption to 2.27 GJ t−1 at a desorption temperature of 40 °C.

https://doi.org/10.1016/j.cej.2024.156782

Iron cyanide compounds are among the oldest known synthetic coordination compounds, dating back to the early 18th century. By contrast, iron complexes of the cyaphide ion (C≡P–)─a heavy valence isoelectronic analog of the cyanide ion─are unknown. Herein we report the synthesis of highly stable mono- and bis-cyaphide complexes of iron(II), namely Fe(depe)2(Cl)(CP) and Fe(depe)2(CP)2 (depe = 1,2-bis(diethylphosphino)ethane). These iron(II) cyaphide complexes are capable of further coordination to iron(I) in a hitherto unknown linear coordination geometry, affording the conjugated multimetallic mixed-valence complexes [{Fe(depe)2}2(μ-CP)(N2)][BArF4]2 and [{Fe(depe)2}3(μ-CP)2][OTf]2.

https://doi.org/10.1021/jacs.4c11741

The major source of fluoride, namely calcium difluoride (CaF2), is derived from the mineral fluorspar. Recent advances in the activation of CaF2 via mechanochemical methods have inspired investigation of the fundamental properties of Ca–F bonds in molecular complexes. However, the paucity of well-defined molecular Ca–F-containing complexes undermines systematic understanding of the factors governing nucleophilic fluoride delivery. Here we report the use of a multidentate bis(phenoxide) ligand based on a 1,4,7-triazacyclononane (TACN) scaffold for the formation of well-defined Ca–F complexes and demonstrate their capabilities in fluoride delivery. Key to this synthesis is a desymmetrization step carried out on the TACN ligand within the Ca coordination sphere. A series of stable anionic dinuclear calcium fluoride complexes has then been accessed and characterized by NMR spectroscopy (critically by 19F NMR) and X-ray crystallography. Nucleophilic fluoride delivery can be used to generate C–F, Si–F and S–F bonds, with a notable advance over amide-derived ligand scaffolds being the reduced extent of side reactions derived from competing attack on the electrophile by the less nucleophilic O-donor anionic ligand set.

https://doi.org/10.1002/anie.202414790

Despite their potential relevance as molecular models for industrial and biological catalysis, well-defined mononuclear iron carbide complexes are unknown, in part due to the limited number of appropriate C1 synthons. Here, we show the ability of the cyaphide anion (C≡P–) to serve as a C1 source. The high spin (S = 2) cyaphide complex PhB(tBuIm)3Fe–C≡P (PhB(tBuIm)3– = phenyl(tris(3-tert-butylimidazol-2-ylidene)borate) is readily accessed using the new cyaphide transfer reagent [Mg(DippNacNac)(CP)]2 (DippNacNac = CH{C(CH3)N(Dipp)}2 and Dipp = 2,6-di(iso-propyl)phenyl). Phosphorus atom abstraction is effected by the three-coordinate Mo(III) complex Mo(NtBuAr)3 (Ar = 3,5-Me2C6H3), which produces the known phosphide (tBuArN)3Mo≡P along with a transient iron carbide complex PhB(tBuIm)3Fe≡C. Electronic structure calculations reveal that PhB(tBuIm)3Fe≡C adopts a doublet ground state with nonzero spin density on the carbide ligand. While isolation of this complex is thwarted by rapid dimerization to afford the corresponding diiron ethynediyl complex, the carbide can be intercepted by styrene to provide an iron alkylidene.

https://doi.org/10.1021/jacs.4c10704

A pillar[5]arene host, functionalised with halogen bonding (XB) recognition sites and BODIPY fluorophores, demonstrates strong binding and optical sensing of environmentally relevant dicarboxylates and a chemical warfare agent simulant, in organic and competitive aqueous-organic media – enabled by the unprecedented combination of fluorophore-conjugated XB interactions with the hydrophobic pillar[5]arene host cavity.

https://doi.org/10.1039/D4CC03748K

The synthesis of a series of isostructural organometallic complexes featuring Ae–Tr bonds (Ae = Be, Mg; Tr = Al, Ga, In) has been investigated, and their electronic structures probed by quantum chemical calculations. This systematic study allows for comparison, not only of the metal–metal bonding chemistries of the two lightest alkaline earth (Ae) elements, beryllium and magnesium, but also of the three triel (Tr) elements, aluminium, gallium, and indium. Computational analyses (NBO, QTAIM, EDA-NOCV) reveal that Be–Tr bonding is more covalent than Mg–Tr bonding. More strikingly, these calculations predict that the beryllium–indyl complex – featuring the first structurally characterised Be–In bond – should act as a source of nucleophilic beryllium. This has been confirmed experimentally by its reactivity towards methyl iodide, which yields the Be–Me functionality. By extension, the electrophilic character of the beryllium centre in the beryllium–gallyl complex contrasts with the umpoled, nucleophilic behaviour of the beryllium centre in both the -indyl and -aluminyl complexes.

https://doi.org/10.1039/D4SC03832K

Dinuclear polymerization catalysts can show high activity and control. Understanding how to design for synergy between the metals is important to improving catalytic performances. Three heterodinuclear Co(III)K(I) catalysts, featuring very similar coordination chemistries, are prepared with different intermetallic separations. The catalysts are compared for the ring-opening copolymerization (ROCOP) of propene oxide (PO) with CO₂ or with phthalic anhydride (PA). The catalyst with a fixed, wide intermetallic separation, L_wideCoK(OAc)₂ (Co–K = 8.06 Å), shows very high activity for PO/PA ROCOP, but is inactive for PO/CO₂ ROCOP. On the other hand, the catalyst with a fixed, narrow intermetallic separation, L_shortCoK(OAc)₂ (Co–K, 3.59 Å), shows high activity for PO/CO₂ ROCOP, but is much less active for PO/PA ROCOP. A bicomponent catalyst system, comprising a monometallic complex L_monoCoOAc used with an equivalent of KOAc[18-crown-6], shows high activity for both PO/CO₂ and PO/PA ROCOP, provided the catalyst concentration is sufficiently high, but underperforms at low catalyst loadings. It is proposed that the two lead catalysts, L_wideCoK(OAc)₂ and L_shortCoK(OAc)₂, operate by different mechanisms for PO/PA and PO/CO₂ ROCOP. The new wide separation catalyst, L_wideCoK(OAc)₂, shows some of the best performances yet reported for PO/PA ROCOP, and suggests other catalysts featuring larger intermetallic separations should be targeted for epoxide/anhydride copolymerizations.

https://doi.org/10.1021/jacs.4c07405

Long-range delocalization of unpaired electrons in organic π-conjugated oligomers is an important requirement to achieve high charge carrier mobilities in molecular transistors. We have investigated the polaron delocalization in the radical cations of a series of β,meso,β-edge-fused porphyrin oligomers consisting of up to 18 porphyrin units by a combination of cw-EPR, 1H, and 14N electron-nuclear double resonance (ENDOR), 14N hyperfine sublevel correlation (HYSCORE), and vis-NIR-MIR spectroscopy, supported by density functional theory (DFT) calculations and simulations. The results demonstrate coherent delocalization of the radical cation over more than 10 porphyrin units, which corresponds to an effective coherence length >8.5 nm. We discovered a remarkably non-uniform distribution of the radical spin density and an increase in phase memory time with increasing delocalization length (up to Tm ≈ 4 μs at 50 K). This study opens new avenues toward the design of molecular electronic and spintronic materials

https://doi.org/10.1016/j.chempr.2024.07.011

Aromatic molecules are like little loops of metal wire—when they are placed in magnetic fields, an electrical current flows around the circumference of the molecule, generating a magnetic dipole. This behavior is common in small π-conjugated rings but rare in molecules with diameters greater than 1 nm. Understanding how to create rings of molecular wire that exhibit ring currents over diameters of many nm will provide nanostructures with highly correlated electrons, resulting in remarkable electronic and magnetic properties. In this article, we present the template-directed synthesis of a macrocycle consisting of 12 porphyrin units, with the porphyrins connected as edge-fused dimers. This 12-porphyrin nanoring is strongly π-conjugated, as reflected by its optical absorption in the near-infrared. It exhibits global aromatic and antiaromatic ring currents over an exceptionally wide range of oxidation states (+8, +6, +4, +2, −2, −4, and −6) due to the efficient electronic delocalization.

https://doi.org/10.1016/j.chempr.2024.06.034

The dynamics of electron and spin transfer in the radical cation and photogenerated triplet states of a tetramethylbiphenyl-linked zinc-porphyrin dimer were investigated, so as to test the relevant parameters for the design of a single-molecule spin valve, and the creation of a novel platforms for the photogeneration of high-multiplicity spin states. We used a combination of multiple techniques, including variable-temperature continuous wave EPR, pulsed proton electron–nuclear double resonance (ENDOR), transient EPR, and optical spectroscopy. The conclusions are further supported by density functional theory (DFT) calculations, and comparison to reference compounds. The low-temperature cw-EPR and room-temperature near-IR spectra of the dimer monocation demonstrate that the radical cation is spatially localized on one side of the dimer at any point in time, while the EPR spectra at 298 K reveal rapid hopping of the radical spin density between both sites of the dimer via reversible intramolecular electron transfer. The hyperfine interactions are modulated by electron transfers and can be quantified using ENDOR spectroscopy. This allowed simulation of the variable- temperature cw-EPR spectra with a two-site exchange model and provided information on the temperature-dependence of the electron transfer rate. The electron-transfer rates range from about 10.0 MHz at 200 K to about 53.9 MHz at 298 K. The activation enthalpies ∆‡H of the electron transfer were determined as ∆‡H = 9.55 kJ mol−1 and ∆‡H = 5.67 kJ mol−1 in a 1:1:1 solvent mixture of CD2Cl2:toluene-d8:THF-d8 and in 2-methyltetrahydrofuran, respectively, consistent with a Robin–Day class II mixed-valence compound. Investigation of the spin-density distribution of the photogenerated triplet state of the Zn-porphyrin dimer reveals localization of the triplet-spin density on a nanosecond time scale on one half of the dimer at 20 K in 2-methyltetrahydrofuran and at 250 K in a polyvinylcarbazole film. We highlight how these results impact the design of single-molecule spintronic devices, quantifying fundamental parameters for relevant building blocks, and offer the first step towards a novel platforms for photogenerated high-multiplicity spin states.

https://pubs.acs.org/doi/10.1021/jacs.4c04186

An ion-responsive MRI contrast agent based on a POPC liposomal scaffold is generated that displays a large amplitude relaxivity switch. Entrapment of MR active Gd-DOTA within cholesterol-doped, i.e., membrane rigidified, liposomes dampens the MR response through diminished water exchange across the lipid bilayer. Relaxivity is re-established by integration of ion carriers in the liposome membrane to mediate solvated ion flux.

https://doi.org/10.1039/D3SC03466F

We have studied the nature of the silica-layered double hydroxide (LDH) interface in silica@ aluminum layered double hydroxide (silica@LDH) core–shell systems. This interface affects the composition of the LDH outer layer and the behavior upon calcination. By combining powder X-ray diffraction (XRD), thermal gravimetric analysis (TGA) and solid state magic-angle spinning nuclear magnetic resonance spectroscopy (ssMAS-NMR) we have demonstrated that the silica-LDH interface consists primarily of alumina. This interface is shown to require a consistent amount of aluminum which is removed from the outer LDH shell. By increasing the amount of aluminum used in the synthesis, Al-containing LDHs of desired M2+/Al3+ composition can be formed. However, upon calcination the composition further changes due to the irreversible migration of aluminum ions from the LDH platelets into the interface. This is in stark contrast to the reversible transitions observed when LDHs are calcined to their layered double oxides (LDOs) and then reconstructed back to LDHs.

https://pubs.acs.org/doi/10.1021/acs.jpcc.4c02999#

Reduction of [Mg(NON)]2 ([NON]2− = [O(SiMe2NDipp)2]2−, Dipp = 2,6-iPr2C6H3) affords Mg(I) species containing NON- and NNO-ligands ([NNO]2− = [N(Dipp)SiMe2N(Dipp)SiMe2O]2−). The products of reactions with iPrN[double bond, length as m-dash]C[double bond, length as m-dash]NiPr and CO are consistent with the presence of reducing Mg(I) centres. Extraction with THF affords [K(THF)2]2[(NNO)Mg–Mg(NNO)] with a structurally characterised Mg–Mg bond that was examined using density functional theory.

https://doi.org/10.1039/D4CC02594F

The thiol-ene based 3D printing of a low molar mass CO2- and bio-derived ABA triblock copolymer through digital light processing is reported. A series of sustainable elastomers are produced with varying thiol cross-linker lengths and poly(ethylene glycol) content to print complex geometries at high resolution. The materials display printing induced phase separation, tunable hydrophilicity, and complete hydrolytic degradation.

https://doi.org/10.1002/anie.202407794

The thiol-ene based 3D printing of a low molar mass CO2- and bio-derived ABA triblock copolymer through digital light processing is reported. A series of sustainable elastomers are produced with varying thiol cross-linker lengths and poly(ethylene glycol) content to print complex geometries at high resolution. The materials display printing induced phase separation, tunable hydrophilicity, and complete hydrolytic degradation.

https://doi.org/10.1039/D4CP02243B

The synthesis of a phosphanyl phosphagermene described. Two principal reactivity modes were observed for this novel compound. On the one hand, it reacts as a geminal frustrated Lewis pair towards CO₂ and nitriles. By contrast, with amines and metal complexes, the P=Ge double bond reacts in 1,2-addition reactions.

https://doi.org/10.1002/chem.202401736

Xanthene-backbone FLPs featuring secondary borane functions –B(ArX)H (where ArX = C6F5 (ArF) or C6Cl5 (ArCl)) have been targeted through reactions of the dihydroboranes Me2S·BArXH2 with [4,5-xanth(PR2)Li]2 (R = Ph, iPr), and investigated in the synthesis of related cationic systems via hydride abstraction. The reactivity of these systems (both cationic and charge neutral) with ammonia have been probed, with a view to probing the potential for proton shuttling via N–H bond ‘activation.’ We find that in the case of four-coordinate boron systems (cationic or change neutral), the N–H linkage remains intact, supported by a NH···P hydrogen bond which is worth up to 17 kcal mol-1 thermodynamically, and enabled by planarization of the flexible xanthene scaffold. For cationic three coordinate systems, N-to-P proton transfer is viable, driven by the ability of the boron centre to stabilise the [NH2]- conjugate base through N-to-B p bonding. This proton transfer can be shown to be reversible in the presence of excess ammonia, depending on the nature of the B-bound ArX group. It is viable in the case of C6F5 substituents, but is prevented by the more sterically encumbering and secondary donor-stabilising capabilities of the C6Cl5 substituent.

https://doi.org/10.1002/anie.202406440

We use a combination of X-ray pair distribution function (PDF) measurements, lattice dynamical calculations, and ab initio density functional theory (DFT) calculations to study the local structure and dynamics in various MPt(CN)6 Prussian blue analogues. In order to link directly the local distortions captured by the PDF with the lattice dynamics of this family, we develop and apply a new “interaction-space” PDF refinement approach. This approach yields effective harmonic force constants, from which the (experiment-derived) low-energy phonon dispersion relations can be approximated. Calculation of the corresponding Grüneisen parameters allows us to identify the key modes responsible for negative thermal expansion (NTE) as arising from correlated tilts of coordination octahedra. We compare our results against the phonon dispersion relations determined using DFT calculations, which identify the same NTE mechanism.

https://doi.org/10.1021/acs.chemmater.4c01013

By exploiting the electronic capabilities of the N-heterocyclic boryloxy (NHBO) ligand, we have synthesized ‘naked’ acyclic gallyl [Ga{OB(NDippCH)2}2]− and indyl [In{OB(NDippCH)2}2]− anions (as their [K(2.2.2-crypt)]+ salts) through K+ abstraction from [KGa{OB(NDippCH)2}2] and [KIn{OB(NDippCH)2}2] using 2.2.2-crypt. These systems represent the first O-ligated gallyl/indyl systems, are ultimately accessed from cyclopentadienyl GaI/InI precursors by substitution chemistry, and display nucleophilic reactivity which is strongly influenced by the presence (or otherwise) of the K+ counterion.

https://doi.org/10.1002/anie.202407427

Owing to its high toxicity, the chemistry of element number four, beryllium, is poorly understood. However, as the lightest elements provide the basis for fundamental models of chemical bonding, there is a need for greater insight into the properties of beryllium. In this context, the chemistry of the homo-elemental Be–Be bond is of fundamental interest. Here the ligand metathesis chemistry of diberyllocene (1; CpBeBeCp)—a stable complex with a Be–Be bond—has been investigated. These studies yield two complexes with Be–Be bonds: Cp*BeBeCp (2) and [K{(HCDippN)₂BO}₂]BeBeCp (3; Dipp = 2,6-diisopropylphenyl). Quantum chemical calculations indicate that the Be–Be bond in 3 is polarized to such an extent that the complex could be formulated as a mixed-oxidation state Be⁰/Be^II complex. Correspondingly, it is demonstrated that 3 can transfer the ‘beryllyl’ anion, [BeCp]^-, to an organic substrate, by analogy with the reactivity of sp²–sp³ diboranes. Indeed, this work reveals striking similarities between the homo-elemental bonding linkages of beryllium and boron, despite the respective metallic and non-metallic natures of these elements.

https://doi.org/10.1038/s41557-024-01534-9

Calcium fluoride is the ultimate source of all fluorochemicals. Current synthetic approaches rely on the use of HF, generated from naturally occurring fluorspar and sulfuric acid. Methods for constructing E–F bonds directly from CaF₂ have long been frustrated by its high lattice energy, low solubility and impaired fluoride ion nucleophilicity. Little fundamental understanding of the reactivity of Ca–F moieties is available to guide methodology development; well-defined molecular species containing Ca–F bonds are extremely rare, and existing examples are strongly aggregated and evidence no nucleophilic fluoride delivery. Here, by contrast, we show that by targeting anionic systems of the type [Ln(X)₂CaF]^-, monomeric calcium fluoride complexes containing single Ca–F bonds can be synthesized, including via routes involving fluoride abstraction from existing C–F bonds. Comparative structural and spectroscopic studies of mono- and dinuclear systems allow us to define structure–activity relationships for E–F bond formation from molecular calcium fluorides.

https://doi.org/10.1038/s41557-024-01524-x

Using CO₂ polycarbonates as engineering thermoplastics has been limited by their mechanical performances, particularly their brittleness. Poly(cyclohexene carbonate) (PCHC) has a high tensile strength (40 MPa) but is very brittle (elongation at break <3%), which limits both its processing and applications. Here, well-defined, high molar mass CO₂ terpolymers are prepared from cyclohexene oxide (CHO), cyclopentene oxide (CPO), and CO₂ by using a Zn(II)Mg(II) catalyst. In the catalysis, CHO and CPO show reactivity ratios of 1.53 and 0.08 with CO₂, respectively; as such, the terpolymers have gradient structures. The poly(cyclohexene carbonate)-grad-poly(cyclopentene carbonate) (PCHC-grad-PCPC) have high molar masses (86 < M_n < 164 kg mol^-1, Đ_M < 1.22) and good thermal stability (T_d > 250 °C). All the polymers are amorphous with a single, high glass transition temperature (96 < T_g < 108 °C). The polymer entanglement molar masses, determined using dynamic mechanical analyses, range from 4 < Me < 23 kg mol^-1 depending on the polymer composition (PCHC:PCPC). These polymers show superior mechanical performance to PCHC; specifically the lead material (PCHC_0.28-grad-PCPC_0.72) shows 25% greater tensile strength and 160% higher tensile toughness. These new plastics are recycled, using cycles of reprocessing by compression molding (150 °C, 1.2 ton m^-2, 60 min), four times without any loss in mechanical properties. They are also efficiently chemically recycled to selectively yield the two epoxide monomers, CHO and CPO, as well as carbon dioxide, with high activity (TOF = 270–1653 h^-1, 140 °C, 120 min). The isolated recycled monomers are repolymerized to form thermoplastic showing the same material properties. The findings highlight the benefits of the terpolymer strategy to deliver thermoplastics combining the beneficial low entanglement molar mass, high glass transition temperatures, and tensile strengths; PCHC properties are significantly improved by incorporating small quantities (23 mol %) of cyclopentene carbonate linkages. The general strategy of designing terpolymers to include chain segments of low entanglement molar mass may help to toughen other brittle and renewably sourced plastics.

https://doi.org/10.1021/acs.macromol.4c00455

Here we demonstrate the preparation of enzyme-metal biohybrids of NAD+ reductase with biocatalytically-synthesised small gold nanoparticles (NPs, <10 nm) and core-shell gold-platinum NPs for tandem catalysis. Despite the variety of methods available for NP synthesis, there remains a need for more sustainable strategies which also give precise control over the shape and size of the metal NPs for applications in catalysis, biomedical devices, and electronics. We demonstrate facile biosynthesis of spherical, highly uniform, gold NPs under mild conditions using an isolated enzyme moiety, an NAD+ reductase, to reduce metal salts while oxidising a nicotinamide-containing cofactor. By subsequently introducing platinum salts, we show that core-shell Au@Pt NPs can then be formed. Catalytic function of these enzyme-Au@Pt NP hybrids was demonstrated for H2-driven NADH recycling to support enantioselective ketone reduction by an NADH-dependent alcohol dehydrogenase.

https://doi.org/10.1002/anie.202404024

The large steric profile of the N-heterocyclic boryloxy ligand, –OB(NDippCH)₂, and its ability to stabilize the metal-centered HOMO, are exploited in the synthesis of the first example of a “naked” acyclic aluminyl complex, [K(2.2.2-crypt)][Al{OB(NDippCH)₂}₂]. This system, which is formed by substitution at Al^I (rather than reduction of Al^III), represents the first O-ligated aluminyl compound and is shown to be capable of hitherto unprecedented reversible single-site [4 + 1] cycloaddition of benzene. This chemistry and the unusual regioselectivity of the related cycloaddition of anthracene are shown to be highly dependent on the availability (or otherwise) of the K⁺ countercation.

https://doi.org/10.1021/jacs.4c00376

While outstanding catalysts are known for the ring-opening copolymerization (ROCOP) of CO₂ and propene oxide (PO), few are reported at low CO₂ pressure. Here, a new series of Co(III)M(I) heterodinuclear catalysts are compared. The Co(III)K(I) complex shows the best activity (TOF = 1728 h^-1) and selectivity (>90% polymer, >99% CO₂) and is highly effective at low pressures (<10 bar). CO₂ insertion is a prerate determining chemical equilibrium step. At low pressures, the concentration of the active catalyst depends on CO₂ pressure; above 12 bar, its concentration is saturated, and rates are independent of pressure, allowing the equilibrium constant to be quantified for the first time (Keq = 1.27 M^-1). A unified rate law, applicable under all operating conditions, is presented. As proof of potential, published data for leading literature catalysts are reinterpreted and the CO₂ equilibrium constants estimated, showing that this unified rate law applies to other systems.

https://doi.org/10.1021/jacs.3c13959

Bimetallic compounds containing direct metal-group 13 element bonds have been shown to display unprecedented patterns of cooperative reactivity towards small molecules, which can be influenced by the identity of the group 13 element. In this context, we present here a systematic appraisal of group 13 metallo-ligands of the type [(NON)E]- (NON = 4,5-bis(2,6-diisopropylanilido)-2,7-di-tert-butyl-9,9-dimethylxanthene) for E = Al, Ga and In, through a comparison of structural and spectroscopic parameters associated with the trans L or X ligands in linear d10 complexes of the types LM{E(NON)} and XM'{E(NON)}. These studies are facilitated by convenient syntheses (from the In(I) precursor, InCp) of the potassium indyl species [{K(NON)In}·KCp]n (1) and [(18-crown-6)₂K₂Cp] [(NON)In] (1'), and lead to the first structural characterisation of Ag–In and Hg–E (E = Al, In) covalent bonds. The resulting structural, spectroscopic and quantum chemical probes of Ag/Hg complexes are consistent with markedly stronger sigma-donor capabilities of the aluminyl ligand, [(NON)Al]-, over its gallium and indium counterparts.

https://doi.org/10.1002/anie.202404527

The homoleptic magnesium bis(aluminyl) compound Mg[Al(NON)]₂ (NON = 4,5-bis(2,6-diisopropylanilido)-2,7-di-tert-butyl -9,9-dimethylxanthene) can be accessed from K₂[Al(NON)]₂ and MgI₂ and shown to possess a non-linear geometry (ÐAl–Mg–Al = 164.8(1)°) primarily due to the influence of dispersion interactions. This compound acts a four-electron reservoir in the reductive de-fluorination of SF₆, and reacts thermally with polar substrates such as MeI via nucleophilic attack through aluminium, consistent with the QT-AIM charges calculated for the metal centres, and a formal description as a Al(I)–Mg(II)–Al(I) trimetallic. On the other hand, under photolytic activation, the reaction with 1,5-cyclooctadiene leads to the stereo-selective generation of transannular cycloaddition products consistent with radical based chemistry, emphasizing the covalent nature of the Mg–Al bonds and a description as a Al(II)–Mg(0)–Al(II) synthon. Consistently, photolysis of Mg[Al(NON)]₂ in hexane in the absence of COD generates [Al(NON)]₂ together with magnesium metal.

https://doi.org/10.1002/anie.202405053

The structure of amorphous silicon (a-Si) is widely thought of as a fourfold-connected random network, and yet it is defective atoms, with fewer or more than four bonds, that make it particularly interesting. Despite many attempts to explain such “dangling-bond” and “floating-bond” defects, respectively, a unified understanding is still missing. Here, we use advanced computational chemistry methods to reveal the complex structural and energetic landscape of defects in a-Si. We study an ultra-large-scale, quantum-accurate structural model containing a million atoms, and thousands of individual defects, allowing reliable defect-related statistics to be obtained. We combine structural descriptors and machinelearned atomic energies to develop a classification of the different types of defects in a-Si. The results suggest a revision of the established floating-bond model by showing that fivefold-bonded atoms in a-Si exhibit a wide range of local environments—analogous to fivefold centers in coordination chemistry. Furthermore, it is shown that fivefold (but not threefold) coordination defects tend to cluster together. Our study provides new insights into one of the most widely studied amorphous solids, and has general implications for understanding defects in disordered materials beyond silicon alone.

https://doi.org/10.1002/anie.202403842

TWhile the nucleophilic addition of ammonia to ketones is an archetypal reaction in classical organic chemistry, the reactivity of heavier group 14 carbonyl analogues (R₂E=O; E=Si, Ge, Sn, or Pb) with NH₃ remains sparsely investigated, primarily due to the synthetic difficulties in accessing heavier ketone congeners. Herein, we present a room-temperature stable boryl-substituted amidinato-silanone {(HCDippN)₂B}{PhC(tBuN)₂}Si=O (Dipp=2,6-iPr₂C₆H₃) (together with its germanone analogue), formed from the corresponding silylene under a N₂O atmosphere. This system reacts cleanly with ammonia in 1,2-fashion to give an isolable sila-hemiaminal complex {(HCDippN)₂B}{PhC(tBuN)₂}Si(OH)(NH₂). Quantum chemical calculations reveal that the formation of this sila-hemiaminal is crucially dependent on the nature of the ancillary ligand scaffold. It is facilitated thermodynamically by the hemi-lability of the amidinate ligand (which allows for the formation of an energetically critical intramolecular N⋅⋅⋅HO hydrogen bond within the product) and is enabled mech-anistically by a process in which the silanone initially acts in umpolung fashion as a base (rather than an acid), due to the strongly electron-releasing and sterically bulky nature of the ancillary boryl ligand.

https://doi.org/10.1002/anie.202402795

The electronic properties, coordination chemistry and reactivity of metal complexes of a planar (C_2v symmetric) acridane-derived geometrically constrained phosphine, P(NNN), are described. On complexation to metal centers, the phosphine was found to adopt a distorted trigonal pyramidal structure with a high barrier to pyramidal inversion (22.3 kcal/mol at 298 K for Au[P(NNN)]Cl). Spectroscopic data and theoretical calculations carried out at the density functional level of theory indicate that P(NNN) is a moderate σ-donor, with significant π-acceptor properties. Despite the distortion undergone by the phosphorus atom on coordination to metal centers, the P(NNN) ligand retains its ability to react with small molecule substrates with polar E−H bonds (MeOH, NH₂Ph, NH₃). It does so in a concerted fashion across one of the P−N bonds, and reversibly in the case of amine substrates. This cooperative bond activation chemistry may ultimately prove beneficial in catalysis.

https://doi.org/10.1002/chem.202400624

Low molar mass, hydroxyl end-capped polymers, often termed “polyols,” are widely used to make polyurethanes, resins, and coatings and as surfactants in liquid formulations. Epoxide/anhydride ring-opening copolymerization (ROCOP) is a controlled polymerization route to make them, and its viability depends upon catalyst selection. In the catalysis, the polyester polyol molar masses and end-groups are controlled by adding specific but excess quantities of diols (vs catalyst), known as the chain transfer agent (CTA), to the polymerizations, but many of the best current catalysts are inhibited or even deactivated by alcohols. Herein, a series of air-stable Al(III)/K(I) heterodinuclear polymerization catalysts show rates and selectivity at the upper end of the field. They also show remarkable increases in activity, with good selectivity and control, as quantities of diol are increased from 10–400 equiv. The reactions are accelerated by alcohols, and simultaneously, their use allows for the production of hydroxy telechelic poly/oligoesters (400 < M_n (g mol^–1) < 20,400, Đ < 1.19). For example, cyclohexene oxide (CHO)/phthalic anhydride (PA) ROCOP, using the best Al(III)/K(I) catalyst with 200 equiv of diol, shows a turnover frequency (TOF) of 1890 h^–1, which is 4.4× higher than equivalent reactions without any diol (Catalyst/Diol/PA/CHO = 1:10–400:400:2000, 100 °C). In all cases, the catalysis is well controlled and highly ester linkage selective (ester linkages >99%) and operates effectively using bicyclic and/or biobased anhydrides with bicyclic or flexible alkylene epoxides. These catalysts are recommended for future production and application development using polyester polyols.

https://doi.org/10.1021/acscatal.3c05712

The ubiquity of charged species in biological and industrial processes has resulted in ever-increasing interest in their selective recognition, detection, and environmental remediation. Building on the established coordination chemistry principles of the chelate and macrocyclic effects, and host preorganization, supramolecular chemists seek to construct specific 3D binding cavities reminiscent of biotic systems to enhance host-guest binding affinity and selectivity. Mechanically interlocked molecules (MIMs) present a wholly unique platform for synthetic host design, wherein topologies afforded by the mechanical bond enable the decoration of 3D cavities for non-covalent interactions with a range of target guest geometries. Notably, MIM host systems exhibit mechanical bond effect augmented affinities and selectivities for a variety of charged guest species, compared to non-interlocked acyclic and macrocycle host analogs. Furthermore, the modular nature of MIM synthesis facilitates incorporation of optical and electrochemical reporter groups, enabling fabrication of highly sensitive and specific molecular sensors. This review discusses the development of recognition and sensing MIMs, from the first reports in the late 20th century through to the present day, delineating how their topologically preorganized and dynamic host cavities enhance charged guest recognition and sensing, demonstrating the mechanical bond effect as a potent tool in future chemosensing materials.

https://doi.org/10.1002/adma.202309098

Optimising the composite cathode for next-generation, safe solid-state batteries with inorganic solid electrolytes remains a key challenge towards commercialisation and cell performance. Tackling this issue requires the design of suitable polymer binders for electrode processability and long-term solid–solid interfacial stability. Here, block-polyester/carbonates are systematically designed as Li-ion conducting, high-voltage stable binders for cathode composites comprising of single-crystal LiNi_0.8Mn_0.1Co_0.1O₂ cathodes, Li₆PS₅Cl solid electrolyte and carbon nanofibres. Compared to traditional fluorinated polymer binders, improved discharge capacities (186 mA h g^-1) and capacity retention (96.7% over 200 cycles) are achieved. The nature of the new binder electrolytes also enables its separation and complete recycling after use. ABA- and AB-polymeric architectures are compared where the A-blocks are mechanical modifiers, and the B-block facilitates Li-ion transport. This reveals that the conductivity and mechanical properties of the ABA-type are more suited for binder application. Further, catalysed switching between CO₂/epoxide A-polycarbonate (PC) synthesis and B-poly(carbonate-r-ester) formation employing caprolactone (CL) and trimethylene carbonate (TMC) identifies an optimal molar mass (50 kg mol^-1) and composition (w_PC 0.35). This polymer electrolyte binder shows impressive oxidative stability (5.2 V), suitable ionic conductivity (2.2 × 10^-4 S cm^-1 at 60 °C), and compliant viscoelastic properties for fabrication into high-performance solid composite cathodes. This work presents an attractive route to optimising polymer binder properties using controlled polymerisation strategies combining cyclic monomer (CL, TMC) ring-opening polymerisation and epoxide/CO₂ ring-opening copolymerisation. It should also prompt further examination of polycarbonate/ester-based materials with today's most relevant yet demanding high-voltage cathodes and sensitive sulfide-based solid electrolytes.

https://doi.org/10.1039/D3SC05105F

Polymer chemical recycling to monomers (CRM) is important to help achieve a circular plastic economy, but the “rules” governing catalyst design for such processes remain unclear. Here, carbon dioxide-derived polycarbonates undergo CRM to produce epoxides and carbon dioxide. A series of dinuclear catalysts, Mg(II)M(II) where M(II) = Mg, Mn, Fe, Co, Ni, Cu, and Zn, are compared for poly(cyclohexene carbonate) depolymerizations. The recycling is conducted in the solid state, at 140 °C monitored using thermal gravimetric analyses, or performed at larger-scale using laboratory glassware. The most active catalysts are, in order of decreasing rate, Mg(II)Co(II), Mg(II)Ni(II), and Mg(II)Zn(II), with the highest activity reaching 8100 h–1 and with >99% selectivity for cyclohexene oxide. Both the activity and selectivity values are the highest yet reported in this field, and the catalysts operate at low loadings and moderate temperatures (from 1:300 to 1:5000, 140 °C). For the best heterodinuclear catalysts, the depolymerization kinetics and activation barriers are determined. The rates in both reverse depolymerization and forward CHO/CO₂ polymerization catalysis show broadly similar trends, but the processes feature different intermediates; forward polymerization depends upon a metal–carbonate intermediate, while reverse depolymerization depends upon a metal-alkoxide intermediate. These dinuclear catalysts are attractive for the chemical recycling of carbon dioxide-derived plastics and should be prioritized for recycling of other oxygenated polymers and copolymers, including polyesters and polyethers. This work provides insights into the factors controlling depolymerization catalysis and steers future recycling catalyst design toward exploitation of lightweight and abundant s-block metals, such as Mg(II).

https://doi.org/10.1021/acscatal.3c04208#

Machine learning (ML) models for molecules and materials commonly rely on a decomposition of the global target quantity into local, atom-centered contributions. This approach is convenient from a computational perspective, enabling large-scale ML-driven simulations with a linear-scaling cost and also allows for the identification and posthoc interpretation of contributions from individual chemical environments and motifs to complicated macroscopic properties. However, even though practical justifications exist for the local decomposition, only the global quantity is rigorously defined. Thus, when the atom-centered contributions are used, their sensitivity to the training strategy or the model architecture should be carefully considered. To this end, we introduce a quantitative metric, which we call the local prediction rigidity (LPR), that allows one to assess how robust the locally decomposed predictions of ML models are. We investigate the dependence of the LPR on the aspects of model training, particularly the composition of training data set, for a range of different problems from simple toy models to real chemical systems. We present strategies to systematically enhance the LPR, which can be used to improve the robustness, interpretability, and transferability of atomistic ML models.

https://doi.org/10.1021/acs.jctc.3c00704

A tetraboryl digermene synthesized by the reaction between a dia- nionic digermanide nucleophile and a boron halide electrophile is dimeric both in the solid state and in hydrocarbon solution. It fea- tures both a planar ‘alkene-like’ geometry for the Ge2B4 core, and an exceptionally short GevGe double bond. These structural fea- tures are consistent with the known electronic properties of the boryl group, and with lowest energy (in silico) fragmentation into two triplet bis(boryl)germylene fragments.

https://doi.org/10.1039/D3DT03416J

We describe the facile synthesis of [(Me₃Si)₂CH]₂E=PMes* (E = Ge, Sn) from the reaction of the tetrylenes with the phospha-Wittig reagent, Me₃P–PMes*. Their reactivity towards a range of substrates with protic and hydridic E–H bonds (E = N, O, Si) is described. In addition to hydroelementation reactions of the E=P bonds, we show that these compounds, particularly [(Me₃Si)₂CH]₂Sn=PMes*, also act as base-stabilized phosphinidenes, allowing phosphinidene transfer to other nucleophiles.

https://doi.org/10.1002/chem.202301542

Understanding the chemistry underpinning intermetallic synergy and the discovery of generally applicable structure-performances relationships are major challenges in catalysis. Additionally, high-performance catalysts using earth-abundant, non-toxic and inexpensive elements must be prioritised. Here, a series of heterodinuclear catalysts of the form Co(III)M(I/II), where M(I/II) = Na(I), K(I), Ca(II), Sr(II), Ba(II) are evaluated for three different polymerizations, by assessment of rate constants, turn over frequencies, polymer selectivity and control. This allows for comparisons of performances both within and between catalysts containing Group I and II metals for CO₂/propene oxide ring-opening copolymerization (ROCOP), propene oxide/phthalic anhydride ROCOP and lactide ring-opening polymerization (ROP). The data reveal new structure-performance correlations that apply across all the different polymerizations: catalysts featuring s-block metals of lower Lewis acidity show higher rates and selectivity. The epoxide/heterocumulene ROCOPs both show exponential activity increases (vs. Lewis acidity, measured by the pKa of [M(OH₂)_m]ⁿ⁺), whilst the lactide ROP activity and CO₂/epoxide selectivity show linear increases. Such clear structure-activity/selectivity correlations are very unusual, yet are fully rationalised by the polymerization mechanisms and the chemistry of the catalytic intermediates. The general applicability across three different polymerizations is significant for future exploitation of catalytic synergy and provides a framework to improve other catalysts.

https://doi.org/10.1038/s41467-023-40284-z

Machine learning (ML) methods are of rapidly growing interest for materials modeling, and yet, the use of ML interatomic potentials for new systems is often more demanding than that of established density-functional theory (DFT) packages. Here, we describe computational methodology to combine the CASTEP first-principles simulation software with the on-the-fly fitting and evaluation of ML interatomic potential models. Our approach is based on regular checking against DFT reference data, which provides a direct measure of the accuracy of the evolving ML model. We discuss the general framework and the specific solutions implemented, and we present an example application to high-temperature molecular-dynamics simulations of carbon nanostructures. The code is freely available for academic research

https://doi.org/10.1063/5.0155621

All fluorochemicals—including elemental fluorine and nucleophilic, electrophilic, and radical fluorinating reagents—are prepared from hydrogen fluoride (HF). This highly toxic and corrosive gas is produced by the reaction of acid-grade fluorspar (>97% CaF₂) with sulfuric acid under harsh conditions. The use of fluorspar to produce fluorochemicals via a process that bypasses HF is highly desirable but remains an unsolved problem because of the prohibitive insolubility of CaF₂. Inspired by calcium phosphate biomineralization, we herein disclose a protocol of treating acid-grade fluorspar with dipotassium hydrogen phosphate (K₂HPO₄) under mechanochemical conditions. The process affords a solid composed of crystalline K₃(HPO₄)F and K_2-xCa_y(PO₃F)_a(PO₄)_b, which is found suitable for forging sulfur-fluorine and carbon-fluorine bonds.

https://doi.org/10.1126/science.adi1557

We describe a new synthetic methodology for the preparation of high quality, emission tuneable InP-based quantum dots (QDs) using a solid, air- and moisture-tolerant primary phosphine as a group-V precursor. This presents a significantly simpler synthetic pathway compared to the state-of-the-art precursors currently employed in phosphide quantum dot synthesis which are volatile, dangerous and air-sensitive, e.g. P(Si(CH₃)₃)₃.

https://doi.org/10.1039/D3NH00162H

We describe the use of the cyaphide-azide 1,3-dipolar cycloaddition reaction for the synthesis of a new class of inorganic rotaxanes containing gold(I) triazaphosphole stoppers. Electron-deficient bis-azides, which thread perethylated pillar[5]arene in aromatic solvents, readily react with two equivalents of Au(IDipp)(CP) (IDipp = 1,3-bis-(2,6-diisopropylphenyl)-imidazol-2-ylidene) to afford interlocked molecules via an inorganic click reaction. These transformations proceed in good yields (ca. 65%) and in the absence of a catalyst. The resulting organometallic rotaxanes are air- and moisture-stable and can be purified by column chromatography under aerobic conditions. The targeted rotaxanes were characterized by multi-element nuclear magnetic resonance (NMR) spectroscopy, mass-spectrometry, and single-crystal X-ray diffraction.

https://doi.org/10.1002/ange.202309211

The complex diberyllocene, CpBeBeCp (Cp, cyclopentadienyl anion), has been the subject of numerous chemical investigations over the past five decades yet has eluded experimental characterization. We report the preparation and isolation of the compound by the reduction of beryllocene (BeCp₂) with a dimeric magnesium(I) complex and determination of its structure in the solid state by means of x-ray crystallography. Diberyllocene acts as a reductant in reactions that form beryllium-aluminum and beryllium-zinc bonds. Quantum chemical calculations indicate parallels between the electronic structure of diberyllocene and the simple homodiatomic species diberyllium (Be₂).

https://doi.org/10.1002/chem.202301648

The complex diberyllocene, CpBeBeCp (Cp, cyclopentadienyl anion), has been the subject of numerous chemical investigations over the past five decades yet has eluded experimental characterization. We report the preparation and isolation of the compound by the reduction of beryllocene (BeCp₂) with a dimeric magnesium(I) complex and determination of its structure in the solid state by means of x-ray crystallography. Diberyllocene acts as a reductant in reactions that form beryllium-aluminum and beryllium-zinc bonds. Quantum chemical calculations indicate parallels between the electronic structure of diberyllocene and the simple homodiatomic species diberyllium (Be₂).

https://doi.org/10.1126/science.adh4419

Utilizing carbon dioxide (CO₂) to make polycarbonates through the ring-opening copolymerization (ROCOP) of CO₂ and epoxides valorizes and recycles CO₂ and reduces pollution in polymer manufacturing. Recent developments in catalysis provide access to polycarbonates with well-defined structures and allow for copolymerization with biomass-derived monomers; however, the resulting material properties are under-investigated. Here, new types of CO₂-derived thermoplastic elastomers (TPEs) are described together with a generally applicable method to augment tensile mechanical strength and Young's modulus without requiring material re-design. These TPEs combine high glass transition temperature (T_g) amorphous blocks comprising CO₂-derived poly(carbonates) (A-block), with low Tg poly(ε-decalactone), from castor oil, (B-block) in ABA structures. The poly(carbonate) blocks are selectively functionalized with metal-carboxylates, where the metals are Na(I), Mg(II), Ca(II), Zn(II) and Al(III). The colorless polymers, featuring <1 wt% metal, show tunable thermal (T_g), and mechanical (elongation at break, elasticity, creep-resistance) properties. The best elastomers show >50-fold higher Young's modulus and 21-times greater tensile strength, without compromise to elastic recovery, compared with the starting block polymers. They have wide operating temperatures (-20 to 200 ˚C), high creep-resistance and yet remain recyclable. In future, these materials could substitute high-volume petrochemical elastomers and be utilized in high-growth fields like medicine, robotics and electronics.

https://doi.org/10.1002/adma.202302825

The steric tuning of a tridentate acridane-derived NNN pincer ligand allows for the isolation of a strictly T-shaped phosphine that exhibits ambiphilic reactivity. Well-defined phosphorus-centered reactivity towards nucleophiles and electrophiles is reported, contrasting with prior reports on this class of compounds. Reactions towards oxidants are also described. The latter result in the two-electron oxidation of the phosphorus atom from +III to +V, and are accompanied by a strong geometric distortion of the NNN pincer ligand. By contrast, cooperative activation of E–H (HCl, HBcat, HOMe) bonds proceeds with retention of the phosphorus redox state. When using H₂O as a substrate, the reaction results in the full disassembly of H₂O to its constituent atoms, highlighting the potential of this platform for small molecule activation reactions.

https://doi.org/10.1002/chem.202300818

The synthesis of group 9 pyridine-diimine complexes M(^DippPDI)X and [M(^DippPDI)L]⁺ (M = Co, Rh; ^DippPDI = 1,1’-(pyridine-2,6-diyl)bis(N-(2,6-diisopropylphenyl)ethan-1-imine; X = CP^-, CCH^-; L = CO, ^tBuNC) bearing a series of strong-field ligands, including the cyaphide ion (C≡P^-), is reported. A combined experimental and computational comparative study of the group 9 PDI cyaphide complexes Co(^DippPDI)(CP) and Rh(^DippPDI)(CP), as well as the N-heterocyclic carbene (NHC) gold(I) cyaphide complex Au(IDipp)(CP) (IDipp = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene), reveals the σ-donor and π-acceptor properties of the κC-cyaphido ligand, and allow us to suggest a position for this ion in the spectrochemical series.

https://doi.org/10.1039/D3SC01126G

A series of dynamic metalloporphyrin [2]rotaxane molecular shuttles comprising of bis-functionalised Zn(II) porphyrin axle and pyridyl functionalised macrocycle components are prepared in high yield via active metal template synthetic methodology. Extensive variable temperature 1H NMR and quantitative UV-Vis spectroscopic titration studies demonstrate dynamic macrocycle translocation is governed by an inter-component co-ordination interaction between the macrocycle pyridyl and axle Zn(II) metalloporphyrin, which serves to bias a ‘resting state’ co-conformation. The dynamic shuttling behaviour of the interlocked structures is dramatically inhibited by the addition of a neutral Lewis base such as pyridine, but can also be tuned via post-synthetic rotaxane demetallation of the porphyrin axle core to give free-base, or upon subsequent metallation, Ni(II) [2]rotaxane analogues. Importantly, the Lewis acidic Zn(II) porphyrin axle component is also capable of coordinating anions which induces mechanical bond shuttling behaviour resulting in a novel optical sensing response.

https://doi.org/10.1002/chem.202300608

Machine learning (ML) approaches enable large-scale atomistic simulations with near-quantum-mechanical accuracy. With the growing availability of these methods there arises a need for careful validation, particularly for physically agnostic models – that is, for potentials which extract the nature of atomic interactions from reference data. Here, we review the basic principles behind ML potentials and their validation for atomic-scale materials modeling. We discuss best practice in defining error metrics based on numerical performance as well as physically guided validation. We give specific recommendations that we hope will be useful for the wider community, including those researchers who intend to use ML potentials for materials “off the shelf”.

https://doi.org/10.1063/5.0139611

The reactions of anionic aluminium or gallium nucleophiles {K[E(NON)]}₂ (E = Al, 1; Ga, 2; NON = 4,5-bis(2,6- diisopropylanilido)-2,7-ditert-butyl-9,9-dimethylxanthene) with beryllocene (BeCp₂) led to the displacement of one cyclopentadienyl ligand at beryllium and the formation of compounds containing Be−Al or Be−Ga bonds (NON)EBeCp (E = Al, 3; Ga, 4). The Be−Al bond in the beryllium−aluminyl complex [2.310(4) Å] is much shorter than that found in the small number of previous examples [2.368(2) to 2.432(6) Å], and quantum chemical calculations suggest the existence of a non-nuclear attractor (NNA) for the Be−Al interaction. This represents the first example of a NNA for a heteroatomic interaction in an isolated molecular complex. As a result of this unusual electronic structure and the similarity in the Pauling electronegativities of beryllium and aluminium, the charge at the beryllium center (+1.39) in 3 is calculated to be less positive than that of the aluminium center (+1.88). This calculated charge distribution suggests the possibility for nucleophilic behavior at beryllium and correlates with the observed reactivity of the beryllium−aluminyl complex with N,N′-diisopropylcarbodiimide − the electrophilic carbon center of the carbodiimide undergoes nucleophilic attack by beryllium, thereby yielding a beryllium−diaminocarbene complex.

https://doi.org/10.1021/jacs.3c00480

The cyaphide anion, CP^-, is shown to undergo three distinct oligomerization reactions in the coordination sphere of metals. Reductive coupling of Au(IDipp)(CP) (IDipp=1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) by Sm(Cp*)₂(OEt₂) (Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl), was found to afford a tetra-metallic complex containing a 2,3-diphosphabutadiene-1,1,4,4-tetraide fragment. By contrast, non-reductive dimerization of Ni(SIDipp)(Cp)(CP) (SIDipp=1,3-bis(2,6-diisopropylphenyl)-imidazolidin-2-ylidene; Cp = cyclopentadienyl), gives rise to an asymmetric bimetallic complex containing a 1,3-diphosphacyclobutadiene-2,4-diide moiety. Spontaneous trimerization of Sc(Cp*)₂(CP) results in the formation of a trimetallic complex containing a 1,3,5-triphosphabenzene-2,4,6-triide fragment. These transformations show that while cyaphido transition metal complexes can be readily accessed using metathesis reactions, many such species are unstable to further oligomerization processes.

https://doi.org/10.1002/anie.202218047

A review about the known chemistry of the cyaphide ion, (C≡P)⁻. This remarkable diatomic anion has been the subject of study since the late nineteenth century, however its isolation and characterization eluded chemists for almost a hundred years. In this mini-review, we explore the pioneering synthetic experiments that first allowed for its isolation, as well as more recent developments demonstrating that cyaphide transfer is viable in well-established salt-metathesis protocols. The physical properties of the cyaphide ion are also explored in depth, allowing us to compare and contrast the chemistry of this ion with that of its lighter congener cyanide (an archetypal strong field ligand and important organic functional group). Recent studies show that the cyaphide ion has the potential to be used as a versatile chemical regent for the synthesis of novel molecules and materials, hinting at many interesting future avenues of investigation.

https://doi.org/10.1002/anie.202217749

The reduction of the boryl-substituted SnII bromide {(HCDippN)₂B}Sn(IPrMe)Br with 1.5 equivalents of potassium graphite leads to the generation of the cyclic tetratin tetraboryl system K₂[Sn₄{B(NDippCH)₂}₄], a homo-metallic heavier analogue of the cyclobutadiene dianion. This system is non-aromatic as determined by Nucleus Independent Chemical Shift Calculations (NICS(0) = 0.28, NICS(1) = 3.17), with the primary contributing resonance structures shown by Natural Resonance Theory (NRT) to involve a Sn=Sn double bond and 1,2-localized negative charges. Abstraction of the K⁺ cations or oxidation leads to contraction or cleavage of the Sn4 unit, respectively, while protonation generates the neutral dihydride 1,2-Sn₄{B(NDippCH)₂}₄H₂ (a heavier homo- logue of cyclobutene) in a manner consistent with the predicted charge distribution in the [Sn₄{B(NDippCH)₂}₄]₂ dianion.

https://doi.org/10.1002/chem.202300006

Boryltin compounds featuring the metal in the + 1 or 0 oxidation states can be synthesized from the carbene- stabilized tin(II) bromide (boryl)Sn(NHC)Br (boryl = {B(NDippCH)₂}; NHC=C{(NiPrCMe)₂}) by the use of strong reducing agents. The formation of the mono-carbene stabilized distannyne and donor-free distannide systems (boryl)SnSn(IPrMe)(boryl) (2) and K₂[Sn₂(boryl)₂] (3), using Mg(I) and K reducing agents mirrors related germanium chemistry. In contrast to their lighter congeners, however, systems of the type [Sn(boryl)]n are unstable with respect to disproportionation. Carbene abstraction from 2 using BPh₃, and two-electron oxidation of 3 both result in the formation of a 2 : 1 mixture of the Sn(II) compound Sn(boryl)₂, and the hexatin cluster, Sn₆(boryl)₄ (4). A viable mechanism for this rearrangement is shown by quantum chemical studies to involve a vinylidene intermediate (analogous to the isolable germanium compound, (boryl)2Ge=Ge), which undergoes facile atom transfer to generate Sn(boryl)₂ and trinuclear [Sn₃(boryl)₂]. The latter then dimerizes to give the observed hexametallic product 4, with independent studies showing that similar trigermanium species aggregate in analogous fashion.

https://doi.org/10.1002/chem.202203395

The reaction of TaMe₃Cl₂ with the rigid acridane- derived trisamine H₃NNN yields the tantalum(V) complex [TaCl₂(NNN^cat)]. Subsequent reaction with dioxygen results in the full four-electron reduction of O₂ yielding the oxido- bridged bimetallic complex [{TaCl₂(NNN^sq)}₂O]. This dinuclear complex features an open-shell ground state due to partial ligand oxidation and was comprehensively characterized by single crystal X-ray diffraction, LIFDI mass spectrometry, NMR, EPR, IR and UV/VIS/NIR spectroscopy. The mechanism of O₂ activation was investigated by DFT calculations revealing initial binding of O₂ to the tantalum(V) center followed by complete O₂ scission to produce a terminal oxido-complex.

https://doi.org/10.1002/chem.202203266

A systematic study to access stable stannaimines is reported, by combining different heteroleptic stannylenes with a range of organic azides. The reactions of terphenyl-/hypersilyl- substituted stannylenes yield the putative tin nitrogen double bond, but is directly followed by 1,2-silyl migration to give Sn(II) systems featuring bulky silylamido ligands. By contrast, the transition from a two σ donor ligand set to a mixed σ-donor / π-donor scaffold allows access to three new stannaimines which can be handled at room temperature. The reactivity profile of these Sn=N bonded species is crucially dependent on the substituent at the nitrogen atom. As such, the Sn=NMes (Mes = 2,4,6-Me₃C₆H₂) system is capable of activating a broad range of substrates under ambient conditions via 1,2-addition reactions, [2+2] and [4+2] cycloaddition reactions. Most interestingly, very rare examples of main group multiple bond metathesis reactions are also found to be viable.

https://doi.org/10.1002/anie.202211616

The development of sustainable plastic materials is an essential target of chemistry in the 21st century. Key objectives toward this goal include utilizing sustainable monomers and the development of polymers that can be chemically recycled/degraded. Polycarbonates synthesized from the ring-opening copolymerization (ROCOP) of epoxides and CO₂, and polyesters synthesized from the ROCOP of epoxides and anhydrides, meet these criteria. Despite this, designing efficient catalysts for these processes remains challenging. Typical issues include the requirement for high catalyst loading; low catalytic activities in comparison with other commercialized polymerizations; and the requirement of costly, toxic cocatalysts. The development of efficient catalysts for both types of ROCOP is highly desirable. This Account details our work on the development of catalysts for these two related polymerizations and, in particular, focuses on dinuclear complexes, which are typically applied without any cocatalyst. We have developed mechanistic hypotheses in tandem with our catalysts, and throughout the Account, we describe the kinetic, computational, and structure–activity studies that underpin the performance of these catalysts. Our initial research on homodinuclear M(II)M(II) complexes for cyclohexene oxide (CHO)/CO₂ ROCOP provided data to support a chain shuttling catalytic mechanism, which implied different roles for the two metals in the catalysis. This mechanistic hypothesis inspired the development of mixed-metal, heterodinuclear catalysts. The first of this class of catalysts was a heterodinuclear Zn(II)Mg(II) complex, which showed higher rates than either of the homodinuclear [Zn(II)Zn(II) and Mg(II)Mg(II)] analogues for CHO/CO₂ ROCOP. Expanding on this finding, we subsequently developed a Co(II)Mg(II) complex that showed field leading rates for CHO/CO₂ ROCOP and allowed for unique insight into the role of the two metals in this complex, where it was established that the Mg(II) center reduced transition state entropy and the Co(II) center reduced transition state enthalpy. Following these discoveries, we subsequently developed a range of heterodinuclear M(III)M(I) catalysts that were capable of catalyzing a broad range of copolymerizations, including the ring-opening copolymerization of CHO/CO₂, propylene oxide (PO)/CO₂, and CHO/phthalic anhydride (PA). Catalysts featuring Co(III)K(I) and Al(III)K(I) were found to be exceptionally effective for PO/CO₂ and CHO/PA ROCOP, respectively. Such M(III)M(I) complexes operate through a dinuclear metalate mechanism, where the M(III) binds and activates monomers while the M(I) species binds the polymer change in close proximity to allow for insertion into the activated monomer. Our research illustrates how careful catalyst design can yield highly efficient systems and how the development of mechanistic understanding aids this process. Avenues of future research are also discussed, including the applicability of these heterodinuclear catalysts in the synthesis of sustainable materials.

https://doi.org/10.1021/acs.accounts.2c00197

Homologation of carbon monoxide is central to the heterogeneous Fischer Tropsch Process for the production of hydrocarbon fuels. C–C bond formation has been modelled by homogeneous systems, with [C_nO_n]^2- fragments (n = 2-6) formed by two-electron reduction being commonly encountered. Here we show that four- or six-electron reduction of CO can be accomplished by the use of anionic aluminium(I) ('aluminyl') compounds, to give both topologically linear and branched C4/C6 chains. We show that the mechanism for homologation relies on the highly electron-rich nature of the aluminyl reagent, and on an unusual mode of interaction of the CO molecule, which behaves primarily as a Z-type ligand in initial adduct formation. The formation of [C₆O₆]^4- from [C₄O₄]^4- shows a solution-phase CO homologation process that brings about chain branching via complete C-O bond cleavage, while comparison of the linear [C₄O₄]^4- system with the [C₄O₄]^6- congener formed under more reducing conditions, models the net conversion of C–O bonds to C–C bonds in the presence of additional reductant.

https://doi.org/10.1021/jacs.2c05228

We report on the insertion of alkynes into heterometallic M–M' bonds, producing (aluminylalkenyl)copper compounds which possess differential reactivity at the two derived M–C functions. Uniquely, this system is capable of controlling access to isolable syn or anti dimetallated alkenes, by employing either kinetic or thermodynamic control. Variation of reaction time also allows regiocontrol to be exerted over the insertion of unsymmetrical alkynes. Subsequent derivatization with CO is both stereoselective (to syn systems) and regioselective (to Cu–C bonds), leading to the formation of the first structurally characterized examples of copper acyl compounds - aided by the cooperative reactivity of the proximal aluminium centre.

https://doi.org/10.1039/D2CC02578G

The synthesis of heterometallic transition metal complexes featuring bridging cyaphide ions (C≡P⁻) is reported. These are synthesized from reactions of Au(IDipp)(CP) (IDipp = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) with electron-rich, nucleophilic transition metal reagents, affording Au(IDipp)(μ₂-C≡P)Ni(^MeIⁱPr)₂ (^MeIⁱPr = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) and Au(IDipp)(μ₂-C≡P)Rh(Cp*)(PMe₃). These studies reveal that, in contrast to the cyanide ion, bimetallic cyaphido complexes strongly favour a η¹:η² coordination mode that maximises the interaction of the second metal (Ni, Rh) with the π-manifold of the ion (and not the phosphorus atom lone pair). End-on bridging can be effectively unlocked by blocking the π-manifold, as demonstrated by reaction of Au(IDipp)(μ²-C≡P)Rh(Cp*)(PMe₃) with an electrophilic transition metal reagent, W(CO)₅(THF), which affords the heterotrimetallic compound Au(IDipp)(μ₃-C≡P)[Rh(Cp*)(PMe₃)][W(CO)₅].

https://doi.org/10.1002/anie.202206783

The reaction of amido-substituted stannylenes with phospha-Wittig reagents (Me₃PPR) results in release of hexamethyldisilazane and tethering of the resulting −CH₂PMe₂PR fragment to the tin center to give P-donor stabilized stannylenes featuring four-membered Sn,C,P,P heterocycles. Through systematic increases in steric loading, the structures of these systems in the solid state can be tuned, leading to successive P–P bond lengthening and Sn–P contraction and, in the most encumbered case, to complete P-to-Sn transfer of the phosphinidene fragment. The resulting stannaphosphene features a polar Sn=P double bond as determined by structural and computational studies. The reversibility of phosphinidene transfer can be established by solution phase measurements and reactivity studies.

https://doi.org/10.1021/jacs.2c03302

Machine learning (ML) based interatomic potentials are emerging tools for material simulations, but require a trade-off between accuracy and speed. Here, we show how one can use one ML potential model to train another: we use an accurate, but more computationally expensive model to generate reference data (locations and labels) for a series of much faster potentials. Without the need for quantum-mechanical reference computations at the secondary stage, extensive reference datasets can be easily generated, and we find that this improves the quality of fast potentials with less flexible functional forms. We apply the technique to disordered silicon, including a simulation of vitrification and polycrystalline grain formation under pressure with a system size of a million atoms. Our work provides conceptual insight into the ML of interatomic potential models and suggests a route toward accelerated simulations of condensed-phase systems.

https://doi.org/10.1063/5.0099929

The cyanide ion plays a key role in a number of industrially relevant chemical processes, such as the extraction of gold and silver from low grade ores. Metal cyanide compounds were arguably some of the earliest coordination complexes studied and can be traced back to the serendipitous discovery of Prussian blue by Diesbach in 1706. By contrast, heavier cyanide analogues, such as the cyaphide ion, C≡P–, are virtually unexplored despite the enormous potential of such ions as ligands in coordination compounds and extended solids. This is ultimately due to the lack of a suitable synthesis of cyaphide salts. Herein we report the synthesis and isolation of several magnesium–cyaphido complexes by reduction of iPr₃SiOCP with a magnesium(I) reagent. By analogy with Grignard reagents, these compounds can be used for the incorporation of the cyaphide ion into the coordination sphere of metals using a simple salt-metathesis protocol.

https://doi.org/10.1021/jacs.1c04417

Template-directed synthesis has been used to prepare a fully π-conjugated cyclic porphyrin octamer, composed of both β,meso,β-edge-fused porphyrin tape units and butadiyne-linked porphyrins. The UV–vis–NIR spectra of this partially fused nanoring show that π-conjugation extends around the whole macrocycle, and that it has a smaller HOMO–LUMO gap than its all-butadiyne-linked analogue, as predicted by TD-DFT calculations. The ¹H NMR shifts of the bound templates confirm the disrupted aromaticity of the edge-fused porphyrins in the neutral nanoring. NMR oxidation titrations reveal the presence of a global paratropic ring current in its 4+ and 8+ oxidation states and of a global diatropic ring current in the 6+ state of the partially fused ring. The paratropic ring current in the 4+ oxidation state is about four times stronger than that in the all-butadiyne-linked cyclic octamer complex, whereas the diatropic current in the 6+ state is about 40% weaker. Two isomeric K-shaped tetrapyridyl templates with trifluoromethyl substituents at different positions were used to probe the distribution of the ring current in the 4+, 6+, and 8+ oxidation states by ¹⁹F NMR, demonstrating that the ring currents are global and homogeneous.

https://doi.org/10.1021/jacs.0c09973