Metal−Metal Quintuple and Sextuple Bonding in Bent Dimetallocenes of the Third Row Transition Metals
ABSTRACT Theoretical studies on the dimetallocenes Cp2M2 (M = Os, Re, W, Ta) predict bent structures with short metal−metal distances suggesting high-order metal−metal multiple bonds. Analysis of the frontier bonding molecular orbitals indicates a formal Os−Os quintuple bond (σ + 2π + 2δ) in singlet Cp2Os2 and a formal Re−Re sextuple bond (2σ + 2π + 2δ) in singlet Cp2Re2, thereby giving the metals in both molecules the favored 18-electron metal configurations. Predicted low-energy triplet structures for Cp2M2 (M = Os, Re) have formal quintuple bonds but with only two δ one-electron “half” bonds (M = Os) or a single δ two-electron bond (M = Re) and a second σ component derived from overlap of the d(z2) orbitals. A quintuple bond similar to that found in triplet Cp2Re2 is found in singlet Cp2W2, giving both tungsten atoms a 16-electron configuration. The formal Ta−Ta quadruple bond in the lowest energy singlet Cp2Ta2 structure is different from that in the original Re2Cl82− in that it is a 2σ + 2π bond with no δ components but only σ and π components.
- SourceAvailable from: unige.chAngewandte Chemie International Edition 05/2006; 45(23):3804 - 3807. · 11.34 Impact Factor
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ABSTRACT: Twenty-three density functional theory (DFT) methods, including the second- and the third-generation functionals, are tested in conjunction with two basis sets (LANL2DZ and SDD) for studying the properties of neutral and ionic silver clusters. We find that DFT methods incorporating the uniform electron gas limit in the correlation functional, namely, those with Perdew's correlation functionals (PW91, PBE, P86, and TPSS), Becke's B95, and the Van Voorhis-Scuseria functional VSXC, generally perform better than the other group of functionals, e.g., those incorporating the LYP correlation functional and variations of the B97 functional. Strikingly, these two groups of functionals can produce qualitatively different results for the Ag3 and Ag4 clusters. The energetic properties and vibrational frequencies of Ag(n) are also evaluated by the different functionals. The present study shows that the choice of DFT methods for heavy metals may be critical. It is found that the exact-exchange-incorporated PBE functional (PBE1PBE) is among the best for predicting the range of properties.The Journal of Chemical Physics 06/2006; 124(18):184102. · 3.12 Impact Factor
- Angewandte Chemie 01/2007; 119(9):1491 - 1494.