Using single-crystal to single-crystal solid/gas reactivity the gold(I) acetylene complex [Au(L1)(η2-HC≡CH)][BArF 4] is cleanly synthesized by addition of acetylene gas to single crystals of [Au(L1)(CO)][BArF 4] [L1=tris-2-(4,4'-di-tert-butylbiphenyl)phosphine, ArF=3,5-(CF3)2C6H3]. This simplest gold-alkyne complex has been characterized by single crystal X-ray diffraction, solution and solid-state NMR spectroscopy and periodic DFT. Bonding of HC≡CH with [Au(L1)]+ comprises both σ-donation and π-backdonation with additional dispersion interactions within the cavity-shaped phosphine., This work was supported by the European Research Council (ERC Starting Grant, CoopCat, Project 756575) and the Spanish Ministry of Science and Innovation (PID2022-139782NB-I00). M. N. acknowledges the Spanish Ministry of Science and Innovation and Junta de Andalucía for postdoctoral programs (FJC2018-035514-I and DOC_00149). Leverhulme Trust (RPG-2020-184; MRG, CLJ) and the Wild Overseas Scholar's Fund (CLJ); the University of St. Andrews (DJS) and EPSRC (EP/W015498/1, MAS; UK Catalysis Hub, EP/R026815/1, MRG). Dr A. Whitwood (York) for helpul discussions and Dr V. Annis (York) for technical assistance with 13C-acetylene experiments. This work used the ARCHER2 UK National Supercomputing Service (https://www.archer2.ac.uk)., Peer reviewed

This work explores the combination of sterically crowded low-valent germanium compounds bearing one or two terphenyl (C6H3-2,6-Ar2) substituents with gold fragments, the latter stabilized by crowded phosphines also containing a terphenyl moiety. The steric protection of these motifs has allowed to examine a series of unusual gold-germylene compounds featuring small hydride and methyl substituents at the germanium site. A gold-germylene dicationic structure is also reported. The bonding in this series is investigated by computational means, providing understanding for the two-way transfer of electrons from germanium to gold and vice versa., This work was supported by the European Research Council (ERC Starting Grant, CoopCat, Project 756575) and the Spanish Ministry of Science and Innovation (Projects PID2019-110856GA-I00 and PID2022-139782NB-I00). SB thanks European Commission for a MSCA fellowship (101023461). J.L.-S. thankfully acknowledges the use of computational facilities of the Centro de Supercomputación of the Universidad de Granada, cluster Albaicin., Peer reviewed

Chemicals and CAS Registry Numbers
carbene 2465-56-7
nickel 7440-02-0, Tetranuclear cores (M-E)2 of transition metals (M) and tetrylenes (EII=Si, Ge, Sn) are key motifs in homogeneous and heterogeneous catalysis. They exhibit a continuum of M-M and E-E bonding within the inorganic core that leads to a variety of structures for which there are no specific synthetic methods. Herein, we report a series of highly reduced [Ni0GeII]2 squares solely stabilized by bulky terphenyl (C6H3-2,6-Ar2) ligands, for which we provide complementary and high-yielding syntheses. Reactivity studies with common Lewis bases (carbene and CO) evince that the structure of the (M-E)2 core can be transformed. We have investigated this core modification by computational means, offering a rationale to better understand the continuum of bonding across these clusters., This work has been supported by the European Research Council (ERC Starting Grant, CoopCat, 756575), MCIN/AEI/10.13039/501100011033 (PID2019-110856GA-I00) and PID2022-139782NB-I00/AEI/10.13039/501100011033/FEDER, UE. SB thanks European Commission for a MSCA fellowship (101023461)., Peer reviewed

Chemicals and CAS Registry Numbers
acetylene 74-86-2
ammonia 14798-03-9, 51847-23-5, 7664-41-7
benzyl bromide 100-39-0
bromide 24959-67-9
chloride 16887-00-6
ethylbenzene 100-41-4
ethylene 74-85-1
germanium 7440-56-4
iodide 20461-54-5
methanol 67-56-1
phenylacetylene 536-74-3
phosphine 7803-51-2
platinum 7440-06-4
water 7732-18-5, Pairing transition metals and heavier tetrylenes (Si, Ge, Sn, Pb) holds great potential for cooperative bond activation and catalysis. In this work, we investigate the reactivity of a low-coordinate Pt(0)/Ge(II) system that emerges from the reaction between the monoligated platinum(0) precursor [(PMe2ArDipp2)Pt(olefin)] with germylene dimer [ArDipp2GeCl]2 (where ArDipp2 = C6H3-2,6-(C6H3-2,6-iPr2)2). The resulting complex reveals ability for cooperative bond activation. Stoichiometric reactions with dihydrogen, water, methanol, ammonia and alkynes unveil the formation of Pt(II)-germyl compounds, characterized by distinct isomeric forms, whose flexibility derives from the particularly low-coordination. We explore its catalytic potential in the hydrodehalogenation of aliphatic, aromatic and main-group halides under dihydrogen atmosphere using both thermal and photochemical conditions, demonstrating promising conversions even for more challenging alkyl chlorides., This work has been supported by the European Research Council (ERC Starting Grant, CoopCat, 756575; JC), the Spanish Ministry of Science and Innovation (PID2022-139782NB-I00; JC, and TED2021-132225B-I00; JC) and Junta de Andalucia (P18-FR-4688; JC). We also acknowledge the European Commission for a MSCA fellowship (101023461; SB), and the use of computational resources of the CSIRC of the Universidad de Granada -cluster Albaicín-. We thank Lamin Keita for his assistance on ligand and precursor synthesis., Peer reviewed

Chemicals and CAS Registry Numbers
gold 7440-57-5
phosphine 7803-51-2
trometamol 1185-53-1, 77-86-1, [(L1)Au(μ-H)2MCp2][BF4] complexes (M = Mo and W) featuring cavity-shaped tris-2-(4,4'-di-tert-butylbi-phenylyl)phosphine (L1) have been isolated. The tungsten derivative showed a remarkably fast reactivity in photolytic hydride transfer to generate the mononuclear gold hydride (L1)AuH. Both bimetallic adducts trap Ag+ cations, forming unprecedented {Au(μ-H)M(μ-H)Ag} trimetallic assemblies with destabilized Au-M interactions., L. R. acknowledges the financial support from the University
of Perugia (Fondo Ricerca di Base di Ateneo 2022), the Royal
Society of Chemistry (R21-1292108967), and the European
Union–NextGenerationEU under the Italian Ministry of
University and Research (MUR) National Innovation Ecosystem
grant ECS00000041-VITALITY. J. C. acknowledges the
European Research Council (ERC Starting Grant, CoopCat,
Project 756575) and the Spanish Ministry of Science and
Innovation (PID2022-139782NB-I00). M. N. acknowledges
Junta de Andalucía for the post-doctoral program
(DOC_00149), Peer reviewed

Redox-active ligands provide alternative reaction pathways by facilitating redox events. Among these, tridentate bis(piridylimino)isoindole (BPI) fragments offer great potential, though their redox-active behaviour remains largely underdeveloped. We describe herein a family of BPI germanium(II) complexes and the study of their redox properties. Amido complexes (RBPI)Ge[N(SiMe3)2] 1-R (R = H, Me, Et) showing a κ2-Npy,Niso coordination to the germanium(II) centre were prepared. In contrast, chloride derivatives (RBPI)GeCl, 2-R, display dynamic κ3-Npy,Niso,Npy coordination to the metal centre. The addition of silver bis(trifluoromethane)sulfonimide to compound 1-H generates a dinuclear complex, 3, where the silver atoms are bound to the germanium and one of the imine nitrogen atoms of another BPI fragment. The reduction of 2-R with KC8 generates dinuclear complexes (4-R) characterized by the formation of new C-C bonds between the isoindoline five-membered rings of two different BPI ligands via a radical mechanism, a transformation that does not take place in the absence of germanium. Interestingly, computational and spectroscopic studies support that the reduction takes place exclusively over the RBPI ligand. Strikingly, the newly formed C-C bond is also readily cleaved. Thus, subsequent reduction of 4-R (R = H, Me) using additional KC8 affords dinuclear species 5-R, with polymeric structures between potassium atoms and the corresponding dinuclear Ge2(RBPI2) fragments., This work has been supported by the Spanish Ministry of Science and Innovation (PID2022-139782NB-I00 and TED2021-132225B-I00) and Junta de Andalucia (P18-FR-4688). JLS acknowledges the use of computational resources of the CSIRC of the Universidad de Granada – cluster Albaicín. The use of computational resources of the Galicia Supercomputing Centre is also acknowledged. Dr Nadir Jori is gratefully acknowledged for his contributions for the electrochemical studies., Peer reviewed

Fluorinated borates have been widely used as innocent and weakly coordinating counteranions. Among those, [BArF4]− ([B(C6H3-3,5-(CF3)2)4]−) occupies a prominent position due to the robustness of its B-C carbon bonds. Herein, we investigate C-B bond cleavage in the [BArF4]− anion mediated by cationic gold fragments of type [Au(PMe2Ar′)]+, where Ar′ stands for bulky terphenyl (C6H3-2,6-Ar2) substituents. In addition, we have exploited the stoichiometric B-C bond cleavage to construct a catalytic cycle for the synthesis of boranes under acidic conditions., This work was supported by the Spanish Ministry of Science and Innovation (PID2022-139782NB-I00). M.N. acknowledges the Spanish Ministry of Science and Innovation and Junta de Andalucía for postdoctoral programs (FJC2018-035514-I and DOC_00149)., Peer reviewed

Chemicals and CAS Registry Numbers
platinum
7440-06-4, Open-shell systems based on first-row transition metals and their involvement in various catalytic processes are well explored. By comparison, mononuclear open-shell complexes of precious transition metals remain underdeveloped. This is particularly true for IrII complexes, as there is very limited information available regarding their application in catalysis. Here we show that a family of IrII metalloradicals, featuring a C6H3-2,6-(OP(tBu)2)2 (POCOP) pincer ligand, effectively catalyses olefin isomerization-a key step in alkane metathesis-exhibiting up to 20 times higher activity than their IrI counterparts. Computational studies reveal that the IrII/IrIV redox cycling enables faster kinetics than the traditional IrI/IrIII pathway owing to reduced barriers for the oxidative addition and reductive elimination steps. Thus, this study presents a redox catalyst involving an IrII/IrIV pair, highlighting the capabilites of precious-metal systems that extend beyond traditional redox cycles. These findings emphasize the need for expanding catalytic design principles, especially for platinum-group metals., The project that gave rise to these results received the support of a fellowship from ‘laCaixa’ Foundation (ID 100010434; fellowship code B005930; A.P.-M.). This work was also supported by the Spanish MCIN/AEI/10.13039/501100011033 (grants PID2022-139782NB-I00, J.C.; PID2022-139318NB-I00, I.F.; TED2021-132225B-I00, J.C. and RED2022-134287-T, J.C. and I.F.). We acknowledge support from the European Commission under Marie Skłodowska-Curie fellowships, project numbers 101067947 (TRUFA, J.J.M.) and 101109769 (READHY, N.H.). We acknowledge the use of CESGA computational facilities. T. J. Gerard and P. L. Holland are acknowledged for their help with EPR spectroscopy. E. Carmona is acknowledged for helpful discussions., Peer reviewed

Single-crystal to single-crystal solid/gas reactivity of [LAu(C2H4/CO)][BArF4] [L = tris-2-(4,4'-di-tert-butylbiphenyl)phosphine] with NH3 or 15NH3 gives the ammonia complexes [LAu(NH3/15NH3)][BArF4]. Solid-gas H/D exchange with D2O vapour gives the ND3 isotopologues, while reaction with HCl vapour affords [1-Cl]/[15NH4][BArF4], identifying a lattice encapsulated ammonium as a plausible intermediate species for H/D exchange with D2O by a proton rebound mechanism., The Leverhulme Trust (RPG-2020-184), EPSRC (EP/W015552/1) and the Wild Overseas Scholar's Fund. M. N. acknowledges the Junta de Andalucía for postdoctoral program (DOC_00149). MCIU/AEI/10.13039/501100011033 (PID2022-139782NB-I00). Marc Reid (Strathclyde), Guy Lloyd-Jones (Edinburgh) and John Hartwig (Berkley) are thanked for useful discussions., Peer reviewed

In the coordination chemistry of heavier tetrylenes (:ER2, where E = Si, Ge, Sn, Pb), chelating P,N-donor ligands occupy a privileged position, though phosphinoamido ligands, [R2P-NR']-, have been barely investigated. Herein, we report the synthesis and structural characterization of such complexes, whose structures drastically differ depending on the group 9 metal precursor used. Strained four-membered {P-N-Ge-M} metallacycles (M = Rh, Ir) are produced from the reaction of phosphinoamido germylenes with [MCl2Cp*]2 precursors (Cp* = η5-C5Me5). At variance, [MCl-(COD)]2 dimers are not broken apart; instead, they afford bimetallic species featuring bridging phosphinoamido-germyl and chloride ligands between the two metals. All new compounds were isolated on a preparative scale and spectroscopically characterized and their structures confirmed by X-ray diffraction. Computational studies support the σ-donor character of the Ge-M interaction and the absence of significant π-backbonding., This work was funded by the European Union (ERC Consolidator Grant, BiMetalGAS, 101169746) and the Spanish MCIU/AEI/10.13039/501100011033 (Grant PID2022-139782NB-I00). The use of computational facilities of the Galicia Supercomputing Centre (CESGA, Cluster Finisterrae-III) are thankfully acknowledged., Peer reviewed

Bimetallic complexes have demonstrated a great ability to enhance the activity of monometallic systems for bond activation and catalysis. In this work, we explore the opposite approach: using a second metal to passivate the activity of another by reversible bimetallic inhibition. To do so we have synthesized a family of nine electrophilic gold complexes of formula Au(PR3)(NTf2) ([NTf2]- = [N(SO2CF3)2]-) that can act as inhibitors in the semihydrogenation of terminal and internal alkynes catalyzed by the iconic iridium Vaska complex IrCl(CO)(PPh3)2. This behavior parallels the well-known passivation effect of lead over palladium in the heterogeneous Lindlard catalyst. Most gold fragments, except for the most hindered, form metal-only Lewis pairs upon combination with iridium, which have been fully characterized and exhibit distinct dative Ir → Au bonds. When applied to alkyne hydrogenation, these bimetallic structures have a clear tendency toward olefin formation, while the monometallic catalyst unselectively leads to overreduction products. Our computational studies not only provide a feasible mechanism for the Ir-only system, but also evince the active role of gold in passivating iridium by reversibly forming heterobimetallic structures that lead to enhanced selectivity., This work has been supported by the Spanish Ministry of Science and Innovation (PID2022-139782NB-I00 and TED2021-132225B-I00), including an FPI fellowship (PRE2020-094795) awarded to E. S. A. P. acknowledges support from “laCaixa” Foundation (100010434; fellowship B005930), J. R. G. from Consejo Nacional de Humanidades, Ciencias y Tecnologías (CONAHCyT) (doctoral fellowship, CVU 779436) and J.J.M. from the European Commission under a Marie Skłodowska-Curie fellowship (101067947, TRUFA)., Peer reviewed

A series of Mn(I) complexes bearing phosphine–phosphite ligands (P-OP) of formula [Mn(Br)(P-OP)(CO)3] (1) have been prepared and characterised. These compounds exist in solution as a mixture of fac and mer isomers with fac/mer ratios from 18 : 1 to 2 : 1. The relatively low donor ability of P-OP compared to bis(trialkylphosphines) or bis–NHC ligands, typically found in non-bifunctional Mn catalysts reported to date, is evinced in IR spectra. Compounds 1 provide efficient catalysts for the hydrogenation of carbonyl substrates using KOtBu as a base. Notably, these complexes constitute a set of modularly designed precatalysts and optimisation of the P-OP ligand provided appropriate catalysts for the reduction of a wide variety of aldehydes and ketones under mild reaction conditions (S/C = 250–500, 20 bar H2, RT to 40 °C). A mechanistic study combining spectroscopic and computational results provides support for a catalyst activation process based on the nucleophilic attack of the alkoxide on a coordinated CO in [Mn(OtBu)(P-OP)(CO)3], as well as a non-bifunctional inner-sphere hydrogenation pathway in the representative hydrogenation of benzophenone. The catalytic cycle is also characterised by a rather stable pentacoordinated alkoxide [Mn(k1-O–OCHPh2)(P-OP)(CO)2] which determines the energetic span of the reaction., We thank Ministerio de Ciencia, Innovación y Universidades from Spain (Grant PID2022-139782NB-I00/AEI/10.13039/501100011033/FEDER, UE) for financial support. The use of computational resources of the Centro Informático Científico de Andalucía (CICA, cluster Hércules) and the Galician Supercomputing Centre (CESGA) are also acknowledged., Peer reviewed

Triplet state tetrylenes posess significant potential for transforming chemically inert substrates, but their fleeting nature has limited their detection beyond low-temperature matrix environments, making the study of their physical and chemical properties challenging. This challenge is exacerbated in heavier tetrylenes, such as germylenes, due to their higher singlet-triplet (S1-T1) energy gaps. Here we report the photoinduced generation of a long-lived triplet germylene with a 14-hour half-life time at room temperature, achieved through an excited singlet–triplet trap stabilization strategy. The metastable nature of this excited state enabled its spectroscopic investigation and the study of its reactivity. Compared to the ground state, enhanced reactivity is observed, including the cleavage of N=N, C–Br, Si–H and even C–C bonds in a doubly reductive cleavage of benzene., This work has been funded by the European Union (ERC, BiMetalGAS, grant no. 101169746 to J.C.) and by MICIU/AEI/10.13039/501100011033 and ERDF/EU (grant nos. PID2022-139782NB-I00 to J.C. and PID2024-161708OB-I00 to G.L.) and MCIN/AEI/10.13039/501100011033 by European Union NextGeneration EU/PRTR under grant no. EUR2023-143467 (G.L.). European Comission is acknowledged for MSCA project (PhotoFLPs, grant no. 101109138 to F.L.). MCIN/AEI/10.13039/501100011033 is also acknowledged for the grant FPU23/01435 (to M.R.). I. García-Rubio is acknowledged for her assistance on EPR measurements., Peer reviewed