The nature of metal-metal bond of the dimetallocene complexes [M2(η5-C5R5)2] (M = Zn, Cd, Hg; R = H, Me): An energy decomposition analysis

The nature of the metal-metal chemical bond in the dimetallocene sandwich complexes M2(η5-C5Me5)2 (M = Zn, Cd, Hg) and their parent molecules M2(η5-C5H5)2 have been investigated using an energy decomposition analysis (EDA) at BP86/TZ2P level. Quantitative bonding analysis results show that both the bond dissociation energy (BDE) and ΔEint values follow the same trend for the metals Zn > Hg > Cd. The metal-metal bonds have slightly more attractive contributions from classical electrostatic interactions than the attractive orbital interactions. The covalent bonding in metal-metal is mainly from a1(σ) orbital interactions. Hg-Hg bond is slightly shorter than Cd-Cd bond, as a result of a remarkable difference of orbital interactions ΔEorb. The results give a deep and unambiguous insight into the nature of the chemical interactions in transition metals nonpolar bonding dimetallocene complexes.