Bonding studies of dinuclear transition metal bis(mu-eta(2)-silane) complexes [LnM(mu-eta(2)-HSiR2)](2) by density functional theory

The bonding and structural features of a series of dinuclear transition met al bis(mu-eta(2)-silane) complexes [LnM(mu-eta(2)-HSiR2)](2) were studied u sing density functional theory calculations. These dinuclear complexes cons ist of two metal fragments doubly bridged by two (mu-eta(2)-HSi) units with a formal metal-metal bond. Each metal fragment conforms to either the 16- or 18-electron rule dependent on the spatial arrangement of ligands around each metal coordination sphere. These dinuclear silane complexes display no ticeably shorter Si ... H distances in the [M(mu-eta(2)-HSi)](2) units when compared with mononuclear eta(2)-silane complexes. The shorter Si ... H di stances in the metal-(eta(2)-silane) interactions suggest that these dinucl ear complexes are more non-classical than mononuclear ones. The more non-cl assical feature is a result of weaker metal(d) to Si-H(sigma*) back-donatio n interactions due to the presence of a metal substituent at silicon. (C) 2 000 Elsevier Science S.A. All rights reserved.