Search

The development of transition metal clusters is an active area of research in inorganic chemistry, as they can be used as catalysts to perform chemically or biologically relevant reactions. Computational chemistry, employing density functional theory (DFT), plays a key role in rationalizing the electronic structure and properties of transition metal clusters. This article reviews recent quantum chemical studies of Mo3S4M clusters (M = Fe, Co, Ni), their CO- or N2-bound variants, and metal–hydride clusters. The ground state of the cluster systems was computed, and properties such as metal–metal bonding, orbital interactions, fluxional behavior of ligands, spectroscopy, and reaction mechanisms were rationalized and compared with available experimental results. Our research findings evidence that computational studies employing quantum chemical methods can guide experimental researchers to develop novel transition metal clusters for potential applications in catalysis. [ABSTRACT FROM AUTHOR] more...

Bimetallic CpMM'Nacnac molecules with group 2 and 12 metals (M=Be, Mg, Ca, Zn, Cd, Hg) that contain novel metal‐metal bonding have been investigated in a theoretical study of their molecular and electronic structure, thermodynamic stability, and metal‐metal bonding. In all cases the metal‐metal bonds are characterized as electron‐sharing covalent single bonds from natural bond orbital (NBO) and energy‐decomposition analysis with natural orbitals of chemical valence (EDA‐NOCV) analysis. The sum of [MM′] charges is relatively constant, with all complexes exhibiting a [MM′]2+ core. Quantum theory of atoms in molecules (QTAIM) analysis indicates the presence of non‐nuclear attractors (NNA) in the metal‐metal bonds of the BeBe, MgMg, and CaCa complexes. There is substantial electron density (0.75–1.33 e) associated with the NNAs, which indicates that these metal‐metal bonds, while classified as covalent electron‐sharing bonds, retain significant metallic character that can be associated with reducing reactivity of the complex. The predicted stability of these complexes, combined with their novel covalent metal‐metal bonding and potential as reducing agents, make them appealing targets for the synthesis of new metal‐metal bonds. [ABSTRACT FROM AUTHOR] more...

Attempts to create a novel Mg−Be bond by reaction of [(DIPePBDI*)MgNa]2 with Be[N(SiMe3)2]2 failed; DIPePBDI*=HC[(tBu)C=N(DIPeP)]2, DIPeP=2,6‐Et2C‐phenyl. Even at elevated temperatures, no conversion was observed. This is likely caused by strong steric shielding of the Be center. A similar reaction with the more open Cp*BeCl gave in quantitative yield (DIPePBDI*)MgBeCp* (1). The crystal structure shows a Mg−Be bond of 2.469(4) Å. Homolytic cleavage of the Mg−Be bond requires ΔH=69.6 kcal mol−1 (cf. CpBe−BeCp 69.0 kcal mol−1 and (DIPPBDI)Mg−Mg(DIPPBDI) 55.8 kcal mol−1). Natural‐Population‐Analysis (NPA) shows fragment charges: (DIPePBDI*)Mg +0.27/BeCp* −0.27. The very low NPA charge on Be (+0.62) compared to Mg (+1.21) and the strongly upfield 9Be NMR signal at −23.7 ppm are in line with considerable electron density on Be and the formal oxidation state assignment of MgII−Be0. Despite this Mgδ+−Beδ− polarity, 1 is extremely thermally stable and unreactive towards H2, CO, N2, cyclohexene and carbodiimide. It reacted with benzophenone, azobenzene, phenyl acetylene, CO2 and CS2. Reaction with 1‐adamantyl azide led to reductive coupling and formation of an N6‐chain. The azide reagent also inserted in the Cp*−Be bond. The inertness of 1 is likely due to bulky ligands protecting the Mg−Be unit. [ABSTRACT FROM AUTHOR] more...

The carbide ligand in the iron–molybdenum cofactor (FeMoco) in nitrogenase bridges iron atoms in different oxidation states, yet it is difficult to discern its ability to mediate magnetic exchange interactions due to the structural complexity of the cofactor. Here, we describe two mixed‐valent diiron complexes with C‐based ketenylidene bridging ligands, and compare the carbon bridges with the more familiar sulfur bridges. The ground state of the [Fe2(μ‐CCO)2]+ complex with two carbon bridges (4) is S=1/2 ${{ 1/2 }}$ , and it is valence delocalized on the Mössbauer timescale with a small thermal barrier for electron hopping that stems from the low Fe−C force constant. In contrast, one‐electron reduction of the [Fe2(μ‐CCO)] complex with one carbon bridge (2) affords a mixed‐valence species with a high‐spin ground state (S=7/2 ${ 7/2 }$), and the Fe−Fe distance contracts by 1 Å. Spectroscopic, magnetic, and computational studies of the latter reveal an Fe−Fe bonding interaction that leads to complete valence delocalization. Analysis of near‐IR intervalence charge transfer transitions in 5 indicates a very large double exchange constant (B) in the range of 780–965 cm−1. These results show that carbon bridges are extremely effective at stabilizing valence delocalized ground states in mixed‐valent iron dimers. [ABSTRACT FROM AUTHOR] more...

Metal‐metal bonds have rarely been explored as active elements in supramolecular assemblies despite their unique potential to introduce responsive behavior. In this report, a dynamic molecular container composed of two cyclometalated Pt units is constructed using Pt−Pt bonds. This molecule—the flytrap—has a flexible jaw composed of two [18]crown‐6 ethers that can adapt their shape to bind large inorganic cations with sub‐micromolar affinity. Along with the spectroscopic and crystallographic characterization of the flytrap, we report its photochemical assembly, which allows the capture of ions and their transport from solution to the solid state. In addition, we have been able to recycle the flytrap to regenerate its starting material due to the reversible nature of the Pt−Pt bond. We believe that other molecular containers and materials for harvesting valuable substrates from solution could be assembled using the advances presented here. [ABSTRACT FROM AUTHOR] more...

Inverse sandwich clusters composed of a monocyclic boron ring and two capping transition metal atoms are interesting alloy cluster systems, yet their chemical bonding nature has not been sufficiently elucidated to date. We report herein on the theoretical prediction of a new example of boron-based inverse sandwich alloy clusters, V2B7−, through computational global-minimum structure searches and quantum chemical calculations. This alloy cluster has a heptatomic boron ring as well as a perpendicular V2 dimer unit that penetrates through the ring. Chemical bonding analysis suggests that the inverse sandwich cluster is governed by globally delocalized 6π and 6σ frameworks, that is, double 6π/6σ aromaticity following the (4n + 2) Hückel rule. The skeleton B−B σ bonding in the cluster is shown not to be strictly Lewis-type two-center two-electron (2c-2e) σ bonds. Rather, these are quasi-Lewis-type, roof-like 4c-2e V−B2−V σ bonds, which amount to seven in total and cover the whole surface of inverse sandwich in a truly three-dimensional manner. Theoretical evidence is revealed for a 2c-2e Lewis σ single bond within the V2 dimer. Direct metal–metal bonding is scarce in inverse sandwich alloy clusters. The present inverse sandwich alloy cluster also offers a new type of electronic transmutation in physical chemistry, which helps establish an intriguing chemical analogy between inverse sandwich clusters and planar hypercoordinate molecular wheels. [ABSTRACT FROM AUTHOR] more...

The actinide-actinide bonding in tri-actinide clusters [An₃Cl₆] z (An=Ac-Pu, z=1-6) and [An₃Cl₆Cp₃] z (z=-2-+3; Cp=(η 5t> -C 5 H 5 )) is studied using density functional theory. We find 3-centre bonding similar to the tri-thorium cluster [{Th(η⁸-C₈H₈)(μ₃-Cl)₂}₃{K(THF)₂}₂] ∞ , as we previously reported (Nature 2021, 598, 72-75). The population of 3-centre molecular orbitals (3c-MOs) by zero, one or two electrons correlates with shortening of the An-An bond lengths, which also decrease with increasing actinide atomic number, consistent with the contraction of the actinide valence atomic orbitals. Mulliken analyses indicate that these 3c-MOs predominantly involve An 6d and 5 f orbitals. Various methods evidence the presence of An-An bonding in most systems with populated 3c-MOs, including bond orders (Mayer and Wiberg), quantum theory of atoms in molecules metrics (ρ, ∇ 2 ρ, -G/V, H, delocalization indices), electron localization function, and electron density assessments. Additionally, we explore the effect of Cp ligand substitution on uranium complexes, finding that bulkier Cp ligands can induce U-U bond distortions and result in slightly longer U-U bonds. Overall, this study advances our understanding of metal-metal bonding in tri-actinide clusters, highlighting its effects on geometric and electronic structures., (© 2024 The Authors. ChemPhysChem published by Wiley-VCH GmbH.) more...

Metal-metal bonding has played a pivotal role in advancing human technologies across various industrial sectors. As devices continue to miniaturize, there is an increasing need for efficient bonding techniques capable of achieving metal-metal bonds at smaller length scales. In this study, a facile but effective bonding technique is developed that enables the bonding of randomly oriented copper with copper nanomembranes under low temperatures and pressures. The fabricated copper nanomembranes, with a thickness of ≈50 nm and a width of 1 cm or above, exhibit a unique heterogeneous nanostructure, comprising copper nanocrystals along with nano-copper-oxide dispersions. Consequently, these copper nanomembranes display exceptional mechanical properties, including an ultra-low elastic modulus of ≈35 GPa, a remarkable yield strength of ≈1 GPa, and excellent ductility of ≈40%, overcoming the conventional strength-ductility trade-off observed in various copper alloys. Most importantly, these ultra-soft copper nanomembranes serve as metallic "glues", promoting grain growth across the bonding interface between randomly oriented copper surfaces. This process leads to an average interfacial shear strength of up to 73 MPa at room temperature, representing an approximate 35 times increase in bonding strength compared to direct copper-copper bonding achieved under identical temperature and pressure conditions., (© 2024 The Author(s). Advanced Science published by Wiley‐VCH GmbH.) more...

The field of platinum chemistry is ubiquitous in the research of anticancer drugs and new OLED materials. Within the vast library of existing compounds, the majority of work focuses on complexes in the +2 and +4 oxidation states, with comparatively few examples of Pt III complexes reported without bridging ligands. Pt III complexes with metal-metal bonding can be made by mild oxidation of Pt II complexes having bis(phenylpyridine) ligands. Here, we report the synthesis and characterization of two new Pt II complexes bearing tetradentate N-bridged bis(phenylpyridine) ligands with N^C*C^N and C^N*N^C coordinating atoms. Through chemical oxidation with PhICl 2 and N-chlorosuccinimide, we obtained four new complexes containing Pt IV and Pt III centres. The dynamics of the Pt III  complexes were explored by variable-temperature NMR studies and showed surprisingly free rotation of the appended N-aryl group. This work uncovers the importance of the destabilizing nature of the bulky N-aryl group on intermetallic bonds, and sheds light on how the molecular rotation observed in the Pt III compounds could inspire new molecular rotors driven by intermetallic bonds., (© 2025 Wiley-VCH GmbH.) more...

The potassium salt of an extremely bulky β-diketiminate, [K(Ar*Nacnac)] (Ar*Nacnac, [(Ar*NCMe)2CH]−; Ar*, C6H2Me{C(H)Ph2}2-4,2,6) was reacted with either CaI2 or YbI2(THF)2, which afforded [(Ar*Nacnac)MI] (M = Ca or Yb). These are the first examples of structurally characterised, donor solvent-free, N-arene substituted β-diketiminato calcium and ytterbium complexes that incorporate a terminal iodide ligand. Reduction of [(Ar*Nacnac)CaI] with sodium metal gave a complex product mixture, from which a few crystals of the β-diketiminate C–H activated product, [{Ca(μ-Ar*Nacnac-H)}2], were obtained and crystallographically characterised. In an attempt to form a terminal ytterbium hydride compound, treatment of [(Ar*Nacnac)YbI] with K[HBEt3] gave a good yield of the contact ion pair compound [(Ar*Nacnac)Yb(HBEt3)]. The extremely bulky β-diketiminato calcium(ii) and ytterbium(ii) iodide complexes [(Ar*Nacnac)MI] (M = Ca or Yb) have been prepared. The reduction of [(Ar*Nacnac)CaI] with sodium metal yielded a ligand C–H activated product, while reaction of [(Ar*Nacnac)YbI] with K[HBEt3] gave an ytterbium(ii) borate contact ion pair (e.g. see picture). [ABSTRACT FROM AUTHOR] more...

The potassium salt of an extremely bulky β-diketiminate, [K(Ar*Nacnac)] (Ar*Nacnac, [(Ar*NCMe)2CH]−ript>; Ar*, C6H2Me{C(H)Ph2}2-4,2,6) was reacted with either CaI2 or YbI2(THF)2, which afforded [(Ar*Nacnac)MI] (M = Ca or Yb). These are the first examples of structurally characterised, donor solvent-free, N-arene substituted β-diketiminato calcium and ytterbium complexes that incorporate a terminal iodide ligand. Reduction of [(Ar*Nacnac)CaI] with sodium metal gave a complex product mixture, from which a few crystals of the β-diketiminate C–H activated product, [{Ca(μ-Ar*Nacnac-H)}2], were obtained and crystallographically characterised. In an attempt to form a terminal ytterbium hydride compound, treatment of [(Ar*Nacnac)YbI] with K[HBEt3] gave a good yield of the contact ion pair compound [(Ar*Nacnac)Yb(HBEt3)]. The extremely bulky β-diketiminato calcium(ii) and ytterbium(ii) iodide complexes [(Ar*Nacnac)MI] (M = Ca or Yb) have been prepared. The reduction of [(Ar*Nacnac)CaI] with sodium metal yielded a ligand C–H activated product, while reaction of [(Ar*Nacnac)YbI] with K[HBEt3] gave an ytterbium(ii) borate contact ion pair (e.g. see picture). [ABSTRACT FROM AUTHOR] more...

Emphanisis, or the appearance out of nothing, has been used to describe the phenomena of spontaneous atom off‐centering and dipole formation at elevated temperatures in lead chalcogenides. Here, we provide spectroscopic evidence of spontaneous formation of metal‐metal bonds above T∼50 K in the layered metal KNi2Se2. These bonds form zig‐zag chains that lower the local symmetry from tetragonal to monoclinic. Energy‐resolved pair distribution function measurements exclude a pure phonon origin of our observations, and instead imply the existence of extra, slowly fluctuating, Ni−Ni bonds above T=50 K. Density functional theory calculations support this lower symmetry configuration as an instability of tetragonal KNi2Se2. We thus demonstrate that the phenomena of emphansis is not limited to local electric dipole formation, but can also be driven by the formation of metal‐metal bonds. [ABSTRACT FROM AUTHOR] more...

Emphanisis, or the appearance out of nothing, has been used to describe the phenomena of spontaneous atom off‐centering and dipole formation at elevated temperatures in lead chalcogenides. Here, we provide spectroscopic evidence of spontaneous formation of metal‐metal bonds above T∼50 K in the layered metal KNi2Se2. These bonds form zig‐zag chains that lower the local symmetry from tetragonal to monoclinic. Energy‐resolved pair distribution function measurements exclude a pure phonon origin of our observations, and instead imply the existence of extra, slowly fluctuating, Ni−Ni bonds above T=50 K. Density functional theory calculations support this lower symmetry configuration as an instability of tetragonal KNi2Se2. We thus demonstrate that the phenomena of emphansis is not limited to local electric dipole formation, but can also be driven by the formation of metal‐metal bonds. [ABSTRACT FROM AUTHOR] more...

The structures and energetics of the binuclear cyclobutadiene vanadium carbonyls (C4H4)2V2(CO)n (n = 8, 7, 6, 5, 4, 3, 2) have been investigated by density functional theory (DFT). The lowest energy (C4H4)2V2(CO)8 structure consists of two C4H4V(CO)4 units linked by a V-V single bond of length 3.4 Å. The two lowest energy (C4H4)2V2(CO)7 structures also have formal V-V single bonds. The "extra" two electrons to give each vanadium atom in these heptacarbonyls the favored 18-electron configuration can come from either an agostic C-H-V interaction activating a hydrogen atom from one of the cyclobutadiene rings or from a four-electron donor bridging η2-µ-CO group with a short V–O distance. The lowest energy (C4H4)2V2(CO)6 structure has a formal V≡V triple bond of length 2.52 Å similar to the V≡V triple bond of length 2.46 Å found in the experimentally known cyclopentadienyl derivative (η5-C5H5)2V2(CO)5. The lowest energy structures for the more highly unsaturated (C4H4)2V2(CO)n (n = 5, 4, 3, 2) have at least two four-electron donor bridging η2-µ-CO groups and a vanadium-vanadium bond order sufficient to give each vanadium atom at least a 16-electron configuration. The structures and energetics of the binuclear cyclobutadiene vanadium carbonyls (C4H4)2V2(CO)n (n = 8, 7, 6, 5, 4, 3, 2) have been investigated by density functional theory. The two lowest energy (C4H4)2V2(CO)7 structures include one with an agostic C-H-V interaction activating a hydrogen atom from one of the cyclobutadiene rings and another with a four-electron donor bridging η2-µ-CO group with a short V–O bonding distance. [ABSTRACT FROM AUTHOR] more...

Molybdenum alkylidyne complexes with a trisilanolate podand ligand framework ("canopy catalysts") are the arguably most selective catalysts for alkyne metathesis known to date. Among them, complex 1 a endowed with a fence of lateral methyl substituents on the silicon linkers is the most reactive, although fairly high loadings are required in certain applications. It is now shown that this catalyst decomposes readily via a bimolecular pathway that engages the Mo≡CR entities in a stoichiometric triple‐bond metathesis event to furnish RC≡CR and the corresponding dinuclear complex, 8, with a Mo≡Mo core. In addition to the regular analytical techniques, 95Mo NMR was used to confirm this unusual outcome. This rapid degradation mechanism is largely avoided by increasing the size of the peripheral substituents on silicon, without unduly compromising the activity of the resulting complexes. When chemically challenged, however, canopy catalysts can open the apparently somewhat strained tripodal ligand cages; this reorganization leads to the formation of cyclo‐tetrameric arrays composed of four metal alkylidyne units linked together via one silanol arm of the ligand backbone. The analogous tungsten alkylidyne complex 6, endowed with a tripodal tris‐alkoxide (rather than siloxide) ligand framework, is even more susceptible to such a controlled and reversible cyclo‐oligomerization. The structures of the resulting giant macrocyclic ensembles were established by single‐crystal X‐ray diffraction. [ABSTRACT FROM AUTHOR] more...

Low‐valent (MeBDI)Al and (MeBDI)Ga and highly Lewis acidic cations in [(tBuBDI)M+⋅C6H6][(B(C6F5)4−] (M=Mg or Zn, MeBDI=HC[C(Me)N‐DIPP]2, tBuBDI=HC[C(tBu)N‐DIPP]2, DIPP=2,6‐diisopropylphenyl) react to heterobimetallic cations [(tBuBDI)Mg–Al(MeBDI)+], [(tBuBDI)Mg–Ga(MeBDI)+] and [(tBuBDI)Zn–Ga(MeBDI)+]. These cations feature long Mg–Al (or Ga) bonds while the Zn–Ga bond is short. The [(tBuBDI)Zn–Al(MeBDI)+] cation was not formed. Combined AIM and charge calculations suggest that the metal–metal bonds to Zn are considerably more covalent, whereas those to Mg should be described as weak AlI(or GaI)→Mg2+ donor bonds. Failure to isolate the Zn–Al combination originates from cleavage of the C−F bond in the solvent fluorobenzene to give (tBuBDI)ZnPh and (MeBDI)AlF+ which is extremely Lewis acidic and was not observed, but (MeBDI)Al(F)‐(μ‐F)‐(F)Al(MeBDI)+ was verified by X‐ray diffraction. DFT calculations show that the remarkably facile C–F bond cleavage follows a dearomatization/rearomatization route. [ABSTRACT FROM AUTHOR] more...

Heteronuclear BeFe(CO)4− anion complex is generated in the gas phase, which is detected by mass‐selected infrared photodissociation spectroscopy in the carbonyl stretching frequency region. The complex is characterized to have a Be−Fe bonded Be−Fe(CO)4− structure with C3v symmetry and all of the four carbonyl ligands bonded on the iron center. Quantum chemical studies indicate that the complex has a quite short Be−Fe bond. Besides one electron‐sharing σ bond, there are two additional, albeit weak, Be ← Fe(CO)4− dative π bonding interactions. The findings imply that metal–metal bonding between s‐block and transition metals is viable under suitable coordination environment. [ABSTRACT FROM AUTHOR] more...

Platinum(II) complexes display versatile chromic behavior as a consequence of their square planar geometry, which enables intra‐ and intermolecular Pt⋅⋅⋅Pt interactions via open axial coordination sites. These metallophilic interactions are known to generate metal‐metal‐to‐ligand‐charge transfer (MMLCT) transitions, in addition to the ligand‐to‐ligand charge transfer (LLCT) and metal‐to‐ligand‐charge‐transfer (MLCT) transitions that are already present. The electronic properties of such complexes, and consequently the magnitude and intensity of these transitions, can be modulated by various functional groups as well as environmental factors, affording control over the color and luminescence. The responsive behavior of these complexes makes them attractive candidates for chromic devices with applications in memory, encryption, sensors, and optoelectronics. This Minireview summarizes the mechanisms and reversibility of optical chromism in platinum(II) complexes, with a focus on the recent developments in the literature. [ABSTRACT FROM AUTHOR] more...

The structures and energetics of the binuclear phospholyl vanadium carbonyls (C4H4P)2V2(CO)n (n = 7, 6, 5, 4, 3, 2, 1) have been investigated using density functional theory. The lowest energy heptacarbonyl (C4H4P)2V2(CO)7 structures resemble those of the dimanganese pentacarbonyl (C4H4P)2Mn2(CO)5 with one seven-electron donor bridging η5,η1-C4H4P ring and no direct vanadium–vanadium bond. Similarly, the lowest energy hexacarbonyl (C4H4P)2V2(CO)6 structure resembles that of the dimanganese tetracarbonyl (C4H4P)2Mn2(CO)4 with two seven-electron donor bridging η5,η1-C4H4P rings and no direct vanadium–vanadium bond. The lowest energy pentacarbonyl (C4H4P)2V2(CO)5 structure has terminal η5-C4H4P phospholyl rings and a formal V≡V triple bond of length ~ 2.45 Å similar to the experimentally known and structurally characterized cyclopentadienyl analogue (η5-C5H5)2V2(CO)5. Various combinations of V=V double bonds or V≡V triple bonds, four-electron donor bridging carbonyl groups and seven-electron donor bridging η5,η1-C4H4P rings are found in the more highly unsaturated derivatives (C4H4P)2V2(CO)n (n = 4, 3, 2) to give 17- and 18-electron vanadium configurations for triplet- and singlet-state structures, respectively. Formal V≣V quadruple bonds are found only in the highly unsaturated lowest energy singlet (C4H4P)2V2(CO)n (n = 2, 1) structures, which, however, lie at somewhat higher energies than isomeric triplet structures. [ABSTRACT FROM AUTHOR] more...

Double deprotonation of the diamine 1,1′‐(tBuCH2NH)‐ferrocene (1‐H2) by alkaline‐earth (Ae) or EuII metal reagents gave the complexes 1‐Ae (Ae=Mg, Ca, Sr, Ba) and 1‐Eu. 1‐Mg crystallized as a monomer while the heavier complexes crystallized as dimers. The Fe⋅⋅⋅Mg distance in 1‐Mg is too long for a bonding interaction, but short Fe⋅⋅⋅Ae distances in 1‐Ca, 1‐Sr, and 1‐Ba clearly support intramolecular Fe⋅⋅⋅Ae bonding. Further evidence for interactions is provided by a tilting of the Cp rings and the related 1H NMR chemical‐shift difference between the Cp α and β protons. While electrochemical studies are complicated by complex decomposition, UV/Vis spectral features of the complexes support Fe→Ae dative bonding. A comprehensive bonding analysis of all 1‐Ae complexes shows that the heavier species 1‐Ca, 1‐Sr, and 1‐Ba possess genuine Fe→Ae bonds which involve vacant d‐orbitals of the alkaline‐earth atoms and partially filled d‐orbitals on Fe. In 1‐Mg, a weak Fe→Mg donation into vacant p‐orbitals of the Mg atom is observed. [ABSTRACT FROM AUTHOR] more...

Two extremely bulky boryl/silyl‐substituted amide ligands, –N{B(DipNCH)2}(SiR3) (R = Me TBoL, R = Ph PhBoL; Dip = 2,6‐diisopropylphenyl) were used in the preparation of the group 12 metal halide complexes, PhBoLZnBr, {TBoLCd(μ‐I)}2, TBoLHgI, and PhBoLHgI. The reduction of these, and two previously reported compounds, PhBoLZnBr(THF) and {PhBoLCd(μ‐I)}2, using a magnesium(I) compound, {(MesNacnac)Mg}2 (MesNacnac = [(MesNCMe)2CH]–, Mes = mesityl), were carried out, leading to mixed results. In several cases these reactions led to decomposition, and deposition of the group 12 metal. However, in two instances the homobimetallic metal(I) complexes, TBoLM–MTBoL (M = Zn or Hg), were isolated and crystallographically characterized. The reduction of {PhBoLCd(μ‐I)}2 afforded the known cadmium(I) complex, PhBoLCd–CdPhBoL, but also gave a very low yield of the thermally unstable complex, PhBoLCd–Mg(THF)(MesNacnac). The X‐ray crystal structure of this compound reveals it to contain the first example of a Cd–Mg bond in a molecular compound. [ABSTRACT FROM AUTHOR] more...

Additions of beryllium–halide bonds in the simple beryllium dihalide adducts, [BeX2(tmeda)] (X=Br or I, tmeda=N,N,N′,N′‐tetramethylethylenediamine), across the metal center of a neutral aluminum(I) heterocycle, [:Al(DipNacnac)] (DipNacnac=[(DipNCMe)2CH]−, Dip=2,6‐diisopropylphenyl), have yielded the first examples of compounds with beryllium–aluminum bonds, [(DipNacnac)(X)Al‐Be(X)(tmeda)]. For sake of comparison, isostructural Mg–Al and Zn–Al analogues of these complexes, viz. [(DipNacnac)(X)Al‐M(X)(tmeda)] (M=Mg or Zn, X=I or Br) have been prepared and structurally characterized. DFT calculations reveal all compounds to have high s‐character metal–metal bonds, the polarity of which is consistent with the electronegativities of the metals involved. Preliminary reactivity studies of [(DipNacnac)(Br)Al‐Be(Br)(tmeda)] are reported. [ABSTRACT FROM AUTHOR] more...

• Low-energy (Me 2 C 2 N 2 P) 2 Ru 2 (CO) n (n = 4, 3) structures typically have dihapto bridging diazaphospholyl ligands. • Terminal η5-Me 2 C 2 N 2 P ligands or bridging η5,η1-Me 2 C 2 N 2 P ligands are found in some higher energy structures. • The (Me 2 C 2 N 2 P) 2 Fe 2 (CO) n (n = 4, 3) systems have complicated potential energy surfaces with higher spin state structures. The structures and energies of the (Me 2 C 2 N 2 P) 2 Ru 2 (CO) n (n = 4, 3) complexes of the four isomeric diazaphospholyl ligands have been studied by density functional theory. Most of the low-energy structures in these systems have one or both diazaphospholyl rings bridging a central Ru Ru bond through Ru N and/or Ru P bonds without involvement of the other three ring atoms. A few higher energy structures are found in these systems having either terminal pentahapto η5-Me 2 C 2 N 2 P ligands or bridging η5,η1-Me 2 C 2 N 2 P ligands bonded to one ruthenium atom as a pentahapto ligand and to the other ruthenium atom through a P → Ru or N → Ru dative bond. The potential surfaces of the analogous iron systems (Me 2 C 2 N 2 P) 2 Fe 2 (CO) n (n = 4, 3) are complicated considerably by other triplet and even quintet structures of comparable energies to structures analogous to the low-energy ruthenium structures. This relates to the lower ligand field strengths of iron complexes as compared with their ruthenium analogues. [Display omitted] [ABSTRACT FROM AUTHOR] more...

This review introduces our study on the development of Cu-based nanoparticles suitable as fillers in the metal–metal bonding process. Colloid solutions of various nanoparticles such as cuprous iodide, cupric oxide (CuO), CuO mixed with silver oxide (Ag2O/CuO), cuprous-oxide (Cu2O), metallic Cu, plolypyrrole-coated metallic Cu, and metallic Cu containing metallic Ag (Ag/Cu) were prepared by liquid phase processes such as reduction and a salt–base reaction. Metal–metal bonding properties of their powders were evaluated by sandwiching the particle powder between metallic discs, annealing them at a pressure of 1.2 MPa, and measuring the shear strength required for separating the bonded discs. Various particles (above-mentioned), various metallic discs (Cu, Ag, and Ni), various bonding temperatures (250–400 °C), and different atmospheres in bonding (H2 and N2) were examined to find nanoparticle filler suitable for metal–metal bonding. As a result, it was confirmed that the metallic Cu, the CuO, the Ag2O/CuO, and the Ag/Cu particles were suitable for CuCu bonding in H2, low-temperature CuCu bonding in H2, AgAg bonding in H2, and CuCu bonding in N2, respectively. The metallic Cu particles also had functions of AgAg and NiNi bondings in H2. These results were explained with the particle size, the amount of impurity, and the d-value. more...

Graphical abstract The lowest energy structures for the tetracarbonyl (C 4 H 4 BH) 2 Co 2 (CO) 4 are doubly bridged structures similar to (C 4 H 4 BCH 3) 2 Co 2 (CO) 4. The lowest energy structures for the unsaturated derivatives (C 4 H 4 BH) 2 Co 2 (CO) n (n = 3, 2, 1) have bridging borole ligands with agostic hydrogen atoms from their B–H groups to a cobalt atom. Highlights • The (C 4 H 4 BH) 2 Co 2 (CO) n (n = 4, 3, 2, 1) systems have been examined by density functional theory. • Low-energy doubly bridged (C 4 H 4 BH) 2 Co 2 (CO) 2 (µ-CO) 2 structures are found similar to (C 4 H 4 BCH 3)Co 2 (CO) 2 (µ-CO) 2. • The lowest energy structures for (C 4 H 4 BH) 2 Co 2 (CO) n (n = 3, 2, 1) have agostic B–H hydrogens from bridging borole ligands. Abstract The (C 4 H 4 BH) 2 Co 2 (CO) n (n = 4, 3, 2, 1) systems have been examined by density functional theory for comparison with the analogous (C 4 H 4 BCH 3) 2 Co 2 (CO) n systems. For the tetracarbonyl (C 4 H 4 BH) 2 Co 2 (CO) 4 a higher energy unbridged structure is found at ∼7 kcal/mol above the lowest energy doubly bridged structure similar to (C 4 H 4 BCH 3) 2 Co 2 (CO) 4. The lowest energy structures for the unsaturated derivatives (C 4 H 4 BH) 2 Co 2 (CO) n (n = 3, 2, 1) have bridging borole ligands with agostic hydrogen atoms from their B–H groups to a cobalt atom. Structures without agostic hydrogens analogous to the low-energy structures for the corresponding methylborole derivatives (C 4 H 4 BCH 3) 2 Co 2 (CO) n are higher energy (C 4 H 4 BH) 2 Co 2 (CO) n structures. [ABSTRACT FROM AUTHOR] more...

The supramolecular architectures of pyrazole ligands with polynuclear metal centers have established a wide variety of constructing motifs. This review focuses on the metal‐metal bonding and Supra‐Metal‐Metal Bonding directed self‐assembly of supramolecular architectures of pyrazole ligands ranging from simple mono‐pyrazoles and derivatives to bipyrazoles and polypyrazoles with group 10 and 11 elements. The utility of the constructing motifs (μ‐pyrazolato‐N,N′)2 doubly‐bridged dimetal corners in the metal‐metal‐bonding directed self‐assembly approaches with spontaneous deprotonation from bipyrazole to tripyrazole and tetrapyrazolyl calix[4]arene ligands, metallomacrocyclic and cage‐like complexes have been synthesized. The proton switching programmable self‐assembly strategy using pyrazole‐based bifunctional ligands has been developed by Yu. They have obtained organic homo‐ or hetero‐metallic supramolecular complexes from macrocycles, cages, to one dimensional polymers. [ABSTRACT FROM AUTHOR] more...

The steric bulk of the well‐known DIPPBDI ligand (CH[C(CH3)N‐DIPP]2, DIPP=2,6‐diisopropylphenyl) was increased by replacing isopropyl for isopentyl groups. This very bulky DIPePBDI ligand could not stabilize the radical species (DIPePBDI)Mg.: reduction of (DIPePBDI)MgI with Na gave (DIPePBDI)2Mg2 with a rather long Mg‐Mg bond of 3.0513(8) Å. Addition of TMEDA prior to reduction gave complex (DIPePBDI)2Mg2(C6H6), which could also be obtained as its THF adduct. It is speculated that combination of a bulky spectator ligand and TMEDA prevents dimerization of the intermediate MgI radical, which then reacts with the benzene solvent. Complex (DIPePBDI)2Mg2(C6H6), which formally contains the anti‐aromatic anion C6H62−, reacted with tBuOH as a Brønsted base to 1,3‐ and 1,4‐cyclohexadiene and with H2 as a two electron donor to (DIPePBDI)2Mg2H2 and C6H6. It also reductively cleaved the C−F bond in fluorobenzene and gave (DIPePBDI)MgPh, (DIPePBDI)MgF, and C6H6. Pepping up chemistry with DIPeP: Replacing the isopropyl groups in a commonly used β‐diketiminate ligand for isopentyl substituents gives the super bulky DIPePBDI ligand. Its dinuclear MgI complex, (DIPePBDI)2Mg2, features a strongly elongated Mg−Mg bond. Attempted isolation of the radical (DIPePBDI)Mg. gave (DIPePBDI)2Mg2(C6H6) in which the formally reduced benzene, C6H62−, is a very strong reductant. [ABSTRACT FROM AUTHOR] more...

Graphical abstract Highlights • Photoelectron spectroscopy and theoretical investigations are conducted on the structures and bonding of a series of di-niobium gold clusters, Nb 2 Au x − (x = 2–5). • Well-resolved spectral features are observed for the Nb 2 Au x − clusters at different photon energies. • Global minimum searches coupled with density functional calculations are performed to find the low-lying structures of the bimetallic clusters. • Vertical detachment energies are calculated and compared with the experimental spectra to determine the global minimum structures. • The Nb 2 Au x − (x = 2–5) clusters are found to feature a multiply-bonded Nb 2 dimer coordinated equatorially by the Au atoms with D xh symmetries for x = 2–5, respectively. • Each Au atom interacts with the Nb 2 dimer via a 3-center delocalized σ bond, while there are no Au...Au interactions. • The Nb Nb bond length is found to increase as the number of gold atoms increases in the Nb 2 Au x − (x = 2–5) clusters, as a result of the decrease of the bond order for the Nb 2 moiety from x = 2 to 5. Abstract We report a joint experimental and theoretical investigation on the structures and bonding of a series of di-niobium gold clusters, Nb 2 Au x − (x = 2–5), using photoelectron spectroscopy and density functional calculations. Well-resolved spectral features are observed for the Nb 2 Au x − clusters at different photon energies. Global minimum searches coupled with density functional calculations are performed to find the low-lying structures of the bimetallic clusters. Vertical detachment energies are calculated and compared with the experimental spectra to determine the global minimum structures. The Nb 2 Au x − (x = 2–5) clusters are found to feature a multiply-bonded Nb 2 dimer coordinated equatorially by the Au atoms with D xh symmetries for x = 2–5, respectively. Each Au atom interacts with the Nb 2 dimer via a 3-center delocalized σ bond, while there are no Au...Au interactions. The Nb Nb bond length is found to increase as the number of gold atoms increases in the Nb 2 Au x − (x = 2–5) clusters, as a result of the decrease of the bond order for the Nb 2 moiety from x = 2 to 5. [ABSTRACT FROM AUTHOR] more...

Geometry optimizations have been performed on the M4(COT)2 (M = Cr-Ni, Pd and COT = C8H8) complexes by means of DFT method using BP86-D functional combined to the TZP basis set. The M4 moiety encapsulated between two COT ligands tends to establish M-L and M-M bonding in relationship with the metal nature and the spin state. In accordance with the coordination modes, the COT behaves as neutral or dianionic ligand. The calculations showed that the various complexes are found to have a low, intermediate, or high-spin ground state. The multiple metal-metal bonding is identified by exploring the bond distances, MO plots, and Wiberg bond index, which vary according to the valence electron count of the M4 core.The Ziegler-Rauk energy decomposition analysis scheme was employed to characterize the geometry distortion and steric interaction (electrostatic and Pauli) and orbital interaction terms in the total bonding energy. The results showed that the interaction terms in all studied complexes are governed by one third covalent and two third ionic characters, in agreement with the ΔEelstat (electrostatic) and ΔEorb (orbital) contributions, respectively, into the total attractive interaction (ΔEelstat + ΔEorb). [ABSTRACT FROM AUTHOR] more...

DFT/BP86 calculations have been carried out on a series of hypothetical binuclear compounds of general formula (L3M)2(C12N2H8) (M = Sc-Ni, L3 = (CO)3, (PH3)3 and Cp−, and C12N2H8 = phenazine ligand-denoted Phn). The various structures with syn and anti configurations have been investigated, in order to determine the phenazine’s coordination to first-row transition metals of various spin states with syn and anti conformations. The lowest energy structures depend on the nature of the metal, the spin state, and the molecular symmetry. This study has shown that the electronic communication between the metal centers depends on their oxidation state and the attached ligands. The tricarbonyl and the triphosphine ligands gave rise to comparable results in terms of stability order of isomers, metal-metal bond distances, and the coordination modes. Metal-metal multiple bonding has been evidenced for Sc, Ti, and V complexes to compensate the electronic deficiency. The Cr, Mn, Fe, Co, and Ni-rich metals prefer the anti conformation due to the enhancement of the metal valence electron count. The spin density values calculated for the triplet and quintet spin structures point out that the unpaired electrons are localized generally on the metal centers. The Wiberg bond indices are used to evaluate the metal-metal bonding. Furthermore, calculations using the BP86-D functional which take into account the attractive part of the van der Waals type interaction potential between atoms and molecules that are not directly connected to each other gave comparable results to those obtained by BP86 functional in terms of coordination modes, HOMO-LUMO gaps, metal-metal bond orders, and the stability order between isomers, but with slight deviation of M-C, M-N, and M-M bond distances not exceeding 3%. [ABSTRACT FROM AUTHOR] more...

Reaction of [U{C(SiMe3)(PPh2)}(BIPM)(m-Cl)Li-(TMEDA)(m-TMEDA)0.5]2 (BIPM=C(PPh2NSiMe3)2; TMEDA=Me2NCH2CH2NMe2) with [Rh(m-Cl)(COD)]2 (COD=cyclooctadiene) affords the heterotrimetallic UIV@ Rh2I complex [U(Cl)2{C(PPh2NSiMe3)(PPh[C6H4]NSiMe3)}-{Rh(COD)}{Rh(CH(SiMe3)(PPh2)}]. This complex has a very short uranium-rhodium distance, the shortest uranium-rhodium bond on record and the shortest actinide-transition metal bond in terms of formal shortness ratio. Quantum-chemical calculations reveal a remarkable RhI⇉UIV net double dative bond interaction, involving RhI 4dz2- and 4dxy/xz-type donation into vacant UIV 5f orbitals, resulting in a Wiberg/Nalewajski-Mrozek U-Rh bond order of 1.30/1.44, respectively. Despite being, formally, purely dative, the uranium-rhodium bonding interaction is the most substantial actinide-metal multiple bond yet prepared under conventional experimental conditions, as confirmed by structural, magnetic, and computational analyses. [ABSTRACT FROM AUTHOR] more...

The skeletal bonding topology as well as the Re=Re distances and Wiberg bond indices in the experimentally known oblatocloso dirhenaboranes Cp*2Re2Bn-2Hn-2 (Cp*=η5Me5C5, n=8-12) suggest formal Re=Re double bonds through the center of a flattened Re2Bn-2 deltahedron. Removal of a boron vertex from these oblatocloso structures leads to oblatonido structures such as Cp2W2B5H9 and Cp2W2B6H10. Similar removal of two boron vertices from the Cp2Re2Bn-2Hn-2 (n=8-12) structures generates oblatoarachno structures such as Cp2Re2B4H8 and Cp2Re2B7H11. Higher energy Cp2Re2Bn-2Hn-2 (Cp=η5-C5H5, n=8-12) structures exhibit closo deltahedral structures similar to the deltahedral borane dianions BnHn2-. The rhenium atoms in these structures are located at adjacent vertices with ultrashort Re≣Re distances similar to the formal quadruple bond found in Re2Cl82- by X-ray crystallography. Such surface Re≣Re quadruple bonds are found in the lowest energy PnRe2Bn-2Hn-2 structures (Pn=η5,η5-pentalene) in which the pentalene ligand forces the rhenium atoms to occupy adjacent deltahedral vertices. The low-energy structures of the tritungstaboranes Cp3W3(H)Bn-3Hn-3 (n=5-12), related to the experimentally known Cp*3W3(H)B8H8, have central W3Bn-3 deltahedra with imbedded bonded W3 triangles. Similar structures are found for the isoelectronic trirhenaboranes Cp3Re3Bn-3Hn-3. The metal atoms are located at degree 6 and 7 vertices in regions of relatively low surface curvature whereas the boron atoms are located at degree 3-5 vertices in regions of relatively high surface curvature. The five lowest-energy structures for the 11-vertex tritungstaborane Cp3W3(H)B8H8 all have the same central W3B8 deltahedron and differ only by the location of the "extra" hydrogen atom. The isosceles W3 triangles in these sW-W edge of ~2.7 to ~2.8 Å corresponding to a surface deltahedral edge. [ABSTRACT FROM AUTHOR] more...

Metal–metal bonding was performed using metallic Cu nanoparticles fabricated from CuO nanoparticles. Colloid solutions of CuO nanoparticles were prepared by the reaction of Cu(NO3)2 and NaOH in aqueous solution at reaction temperatures (TCuOs) of 20, 40, 60 and 80 °C. CuO single crystallites with a size of ca. 10 nm were produced, and they formed leaf-like aggregates. The longitudinal and lateral sizes of the aggregates decreased from 522 to 84 nm and from 406 to 23 nm, respectively, with an increase in TCuO. Colloid solutions of metallic Cu nanoparticles were prepared by reducing the CuO nanoparticles with hydrazine in the presence of cetyltrimethylammonium bromide. The size of the metallic Cu nanoparticles decreased from 92 to 73 nm with increasing TCuO. Metallic copper discs were bonded with the metallic Cu nanoparticles by annealing at 400 °C and 1.2 MPa for 5 min in H2 gas. The shear strength required to separate the bonded discs increased with increasing TCuO. A maximum shear strength of 39.2 MPa was recorded for a TCuO of 80 °C. more...

The heterometallic chromium-manganese carbonyl nitrosyls CrMn(NO)(CO)n (n = 9, 8) have been investigated by density functional theory. The lowest energy CrMn(NO)(CO)9 structures have unbridged staggered conformations with a ~2.99 Å Cr−Mn single bond similar to the experimental and lowest energy structures of the isoelectronic Mn2(CO)10 and Cr2(NO)2(CO)8. A significantly higher energy CrMn(NO)(CO)9 isomer has a nearly symmetrical bridging nitrosyl group and a very weakly semibridging carbonyl group. The two lowest energy structures of the unsaturated CrMn(NO)(CO)8 have a five-electron donor bridging η2-µ-NO nitrosyl group or a four-electron donor bridging η2-µ-CO group, as well as a Cr−Mn single bond of length ~2.94 Å. The next higher energy CrMn(NO)(CO)8 structure has exclusively terminal CO and NO ligands and a shorter Cr−Mn single bond of ~2.85 Å, suggesting an 18-electron configuration for the manganese atom and a 16-electron configuration for the chromium atom indicated by a vacant coordination site nearly perpendicular to the Cr−Mn bond. more...

Unsubstituted bis-indenylchromium has been shown to be a dimer, Cr 2 (Ind) 4 , whereas the monomeric sandwich-type structure, Cr(Ind) 2 , has been only observed for substituted relatives. DFT calculations indicate that dimerization allows the building of a quadruple Cr-Cr bond whereas it can still participate in five formal 2-electron metal-ligand bonds. Despite of this apparently favorable situation with respect to dimer stability, the energetic balance in favor of the dimer is computed not to be very large. Calculations on a series of related Cr, Mn, Fe and Co relatives indicate that Cr 2 (Ind) 4 appears unique in terms of its stability relatively to its monomer. However, dimeric species such as Cr 2 (Cp) 2 (Ind) 2 , Cr 2 (Cp) 4 or Mn 2 (Ind) 4 appear to be not that much unstable relatively to their monomer for being observed under some specific circumstances. [ABSTRACT FROM AUTHOR] more...

Binuclear transition metal carbonyl clusters serve as the simplest models in understanding metal-metal and ligand bonding that are important organometallic chemistry catalysis. Binuclear first row transition metal carbonyl ions are produced via a pulsed laser vaporization/supersonic expansion cluster ion source in the gas phase. These ions are studied by mass-selected infrared photodissociation spectroscopy in the carbonyl stretching frequency region. Density functional theory calculations have been performed on the geometric structures and vibrational spectra of the carbonyl ions. Their geometric and electronic structures are determined by comparison of the experimental IR spectra with the simulated spectra. The structure and the metal-metal and metal-CO bonding of both saturated and unsaturated homonuclear as well as heteronuclear carbonyl cluster cations and anions are discussed. [ABSTRACT FROM AUTHOR] more...

As the tenth year that follows the premature passing of the inorganic chemistry legend F. Albert (Al) Cotton comes to a close, we provide some soul food that we believe Al would have enjoyed as he looks down upon two generations of disciples, a grandchild and two great grandchildren, in his scientific family tree. This article also represents a new tradition by which the editors of Comments on Inorganic Chemistry wish to lead by example, whereby we start publishing original research content that nonetheless preserves the journal’s identity as a niche for “critical discussion of the current literature” of inorganic chemistry. Thus, we show novel demonstrations of a posteriori validation and a priori prediction of possible counterintuitive covalent M-M’ bonds—after and before synthesis, respectively—contrasted with non-covalent M···M interactions of the metallophilic type in bridge-dimeric systems of d10 metal centers. Mixing of (n + 1)s0/p0 orbitals with (n)d10 orbitals in the former heterobimetallics case—and lack thereof in the latter homobimetallics case—is hypothesized to be responsible for the presence or absence of covalency, respectively. However, we also demonstrate that the consequent d-s’ and/or d-p’ orbital mixing/hybridization can occur even in homobimetallic complexes that contain asymmetric bridging ligands (e.g., with -S^C- donor atoms that lead to orbital interactions between M-S and M-C fragments). Hence, the “control” metallophilic case for the hypothesized d10-d10 polar-covalent bonding herein is best manifest by M2(P^P)2 homobimetallics vis-à-vis M2(S^C)2 embodiments. Finally, we also offer a point/counterpoint commentary to the readers to contrast factors that argue for covalency vs metallophilicity and forewarn against exaggerating the extent of covalent bonding in such d10-d10 species. Thus, scrutinizing the various theoretical parameters has pointed to M-M’ and M-M partially bonded S^C-bridge dinuclear d10 complexes vis-à-vis the classic Cotton-type multiple metal-metal bond description in d0 more...

Detailed knowledge of the electronic structure of vanadium oxide clusters provides the basis for understanding and tuning their significant catalytic properties. However, already for the simple four-atom V2O2 molecule, there are contradictory reports in the literature regarding the electronic ground state and a possible vanadium-vanadium bond. We herein show through a combination of experimental (matrix isolation) studies and theoretical results that there is a multiple vanadium-vanadium bond in this benchmark vanadium oxide molecule. [ABSTRACT FROM AUTHOR] more...

Detailed knowledge of the electronic structure of vanadium oxide clusters provides the basis for understanding and tuning their significant catalytic properties. However, already for the simple four-atom V2O2 molecule, there are contradictory reports in the literature regarding the electronic ground state and a possible vanadium-vanadium bond. We herein show through a combination of experimental (matrix isolation) studies and theoretical results that there is a multiple vanadium-vanadium bond in this benchmark vanadium oxide molecule. [ABSTRACT FROM AUTHOR] more...

A metal–metal bonding technique is described that uses nanoparticles composed of silver and copper. Colloid solutions of nanoparticles with an Ag content of 0–100 mol% were prepared by simultaneous reduction of Ag+ and Cu2+ using hydrazine with polyvinylpyrrolidone and citric acid as stabilisers. The nanoparticles ranged in size from 34 to 149 nm depending on the Ag content. Copper discs were strongly bonded at 400°C for 5 min under 1.2 MPa pressure in hydrogen gas; the maximum shear strength was as high as 23.9 MPa. The dependence of shear strength on the Ag content was explained by a mismatch between the d-spacings of Cu metal and Ag metal. [ABSTRACT FROM AUTHOR] more...