Photochemically Induced Silicon−Carbon Bond Cleavage in a Dimethylsilyl-Bridged Dicyclopentadienyl Diruthenium Complex

Abstract

The synthesis and X-ray crystal structure of the novel permethylated dimethylsilyl-bridged diruthenium complex Me2Si[(C5Me4)Ru(CO)2]2 (1) is reported. The molecular structure displays a metal−metal bond of 2.7121(4) Å, which is supported by two symmetrical μ-bridging CO groups and, in addition, two terminal carbonyl ligands. In solution, exchange of these carbonyl groups is observed, as shown by 13C NMR EXSY and VT IR-measurements. It is suggested that the exchange process proceeds via the energetically disfavoured intermediate 1a, which displays four terminal CO ligands. This view is supported by density functional calculations, which indicate a C2-symmetrical structure for 1a. Photochemically induced cleavage of the silicon−carbon and Ru−Ru bonds in 1 results in complex 3, which is thermodynamically uphill from 1 according to our DFT calculations. The molecular structure of complex 3 was unambiguously confirmed by X-ray crystallography.