Atom-Precise Ligated Copper and Copper-Rich Nanoclusters with Mixed-Valent Cu(I)/Cu(0) Character: Structure–Electron Count Relationships

International audienceCopper homometallic and copper-rich heterometallic nanoclusters with some Cu(0) character are reviewed. Their structure and stability are discussed in terms of their number of “free” electrons. In many aspects, this structural chemistry differs from that of their silver or copper homologs. Whereas the two-electron species are by far the most numerous, only one eight-electron species is known, but more electron-rich nanoclusters have also been reported. Owing to the relatively recent development of this chemistry, it is likely that more electron-rich species will be reported in the future

The Coordination Chemistry of Azulene: A Comprehensive DFT Investigation

International audienceDFT calculations with full geometry optimization have been carried out on a series of real and hypothetical compounds of the type LnMAz, MAz2, LnM2Az, and M2Az2 (Az = azulene). The analysis of their electronic and molecular structures in relation to their electron counts allows a comprehensive rationalization of the bonding within this very large family of compounds. A very rich coordination chemistry of azulene is apparent, even much richer than one could determine from the avalaible experimental data. The reason for this diversity comes in part from the marked dissymmetry of azulene, which is made up of two fused rings of very different sizes. It comes also in large part from the very large electronic and structural flexibility of azulene (in contrast to its isomer naphthalene), which is able to adapt to the electronic demand of the metal(s). Any of the fused C5 and C7 rings of azulene can be coordinated in various hapticities and symmetries, depending on the nature of the MLn moiety (or moieties) they are bonded to. This flexibility favors the possibility of existence of several isomers (sometimes enantiomers) of similar energy and of their interconversion in solution, in particular through haptotropic shifts. The azulene asymmetry causes dinuclear complexes to exhibit very different coordination environments (sometimes different oxidation states). In some of them, M−M bonding is preferred over M−azulene bonding. Most of the investigated complexes are expected to exhibit a rich fluxional behavior

A DFT investigation of the structure/electron count relationship in an electron-rich copper nanocluster with unprecedented Cu39 superatomic core

International audienceThis paper reports a DFT computational analysis of the richest in electron ever known thiolate-protected copper nanocluster that was recently reported by Liu, Huang and coworkers as being [Cu75(S-Adm)32]2+. Our calculations suggest that this compound is most likely the closed-shell trication [Cu75(S-Adm)32]3+ and that it is a 40-electron superatom with the 1S2 1P6 1D10 2S2 1F14 2P6 configuration. This electron count is associated with an unprecedented multishell [Cu39]- = Cu@Cu14(tetrakis hexahedron)@Cu24(truncated octahedron) superatomic core. This core is protected by 32 thiolate ligands and 36 Cu(I) metal centers which are coordinated to two or three sulfur lone pairs

On the Electronic Structure of Distorted Cubic Rhodium Cluster Complexes Containing Bridging Germanium or Phosphorus Ligands

International audienceDFT calculations show that the optimal metal valence electron (MVE) count of omnicapped cubic rhodium clusters containing more than eight terminal ligands, is 114. For such a count, a closed-shell configuration is computed with a substantial HOMO-LUMO gap. The presence of more than eight terminal ligands in the clusters favors highly distorted cubic architectures with capping ligands asymmetrically bound to the distorted metallic square faces. Removal of terminal ligands leads to the replacement of bonding M-L electron pairs by nonbonding electron pairs localized on the metal atoms, giving rise to unchanged MVE count

Ten-Electron Donor Indenyl Anion in Binuclear Transition-Metal Sandwich Complexes: Electronic Structure and Bonding Analysis

International audienceWhereas dinuclear sandwich complexes of pentalene, azulene and naphthalene are not uncommon, their bis-indenyl counterparts are scarce, with only two M2(indenyl)2 examples known so far. This paper investigates by the means of DFT calculations the possibility for such compounds to exist for the M=Sc−Ni and Y-(Re)-Pd series. Stable diamagnetic species are predicted for total valence electron counts (TNE) of 34 and 40. The most favored situation corresponds to TNE = 34. For this electron count, which exhibits full ligand hapticity, no formal metal-metal bond exists, but only weak non-bonding attraction. Adding supplementary electrons (TNE \textgreater 34) results in partial ligand decoordination. When TNE \textless 34, metal-metal bonding is predicted to compensate electron deficiency, with the largest formal bond order for TNE = 26. However, in the case of the series of the first-row metals, the metal-metal interaction is rather weak, thus favoring the existence of low-lying high-spin states. On the other hand, all the second-row (and Re) complexes are computed to be diamagnetic. It is concluded that there is no specific reason for M2(indenyl)2 complexes not being isolabl

Why is bis-indenylchromium a dimer? A DFT investigation

International audienceUnsubstituted 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

Carbonylmetallates as versatile 2-, 4- or 6-Electron Donor Metalloligands in Transition-Metal Complexes and Clusters: A Global Approach

International audienceCarbonylmetallates [m]-, such as [MoCp(CO)3]-, [Mn(CO)5]-, [Co(CO)4]-, have long been successfully used in the preparation of hundreds of metal carbonyl complexes and clusters, in particular of the heterometallic type. We focus here on situations where [m]- can be viewed as a terminal, doubly- or even triply-bridging metalloligand, developing metal-metal interactions with one, two or three metal centres M, respectively. With metals M from the groups 10-12, is not straightforward or even impossible to rationalize the structure of the resulting clusters by applying the well-known Wade-Mingos rules. A very simple but global approach is presented to rationalize structures not obeying usual electron-counting rules by considering the anionic building blocks [m]- as metalloligands behaving formally as potential 2, 4 or 6 electron donors, similarly to what is typically encountered with e.g. halido ligands. Qualitative and theoretical arguments using DFT calculations highlight similarities between seemingly unrelated metal complexes and clusters and also entails a predicting power with high synthetic potential

Electronic structure of bis-azepine transition-metal complexes: A DFT investigation

International audienceDFT calculations with full geometry optimizations have been carried out on a series of hypothetical compounds of M(C6NH7)2 (M = transition metal) type with an eclipsed and staggered conformations in order to understand their electronic structure. A rationalization of the bonding with respect to the electron count in all the investigated hypothetical complexes is provided. Depending on the electron count and the nature of the metal, the azepine ligands can bind to the metal through the (η7,η7), (η6,η6), (η7,η4), (η6,η4), (η4,η4), (η4,η2) and (η3,η3) coordination modes

The coordination of azepine to transition-metal complexes: A DFT analysis

International audienceDFT calculations with full geometry optimizations have been carried out on a series of real and hypothetical compounds of the CpM(C6NH7) and (CO)3M(C6NH7) (M = transition-metal) type. A rationalization of the bonding in all the known compounds and in hypothetical complexes is provided. Depending on the electron count and the nature of the metal, the azepine ligand can bind to the metal through the η1, η2, η4, η6, or η7 coordination mode