Synthesis, structure, and reactivity of a bis(silylene)carbonylruthenium complex and a novel addition reaction of photochemically generated dimethylsilylene to bis(silylene) complexes Cp(OC)M{SiMe₂⋯O(Me)⋯SiMe₂} (M = Ru, Fe)

Photolysis of CpRu(CO)₂SiMe₂SiMe₃ (1a) with a low- or medium-pressure Hg lamp for a long time caused the loss of a SiMe₂ moiety to give CpRu(CO)₂SiMe₃ (2), perhaps through the photochemical dissociation of a CO ligand. This mechanism was supported by the quantitative formation of the bis(silylene)ruthenium complex Cp(OC)Ru{SiMe₂⋯O(Me)⋯ SiMe₂} (3a) by photolysis of the (methoxydisilanyl)ruthenium complex CpRu(CO)₂SiMe₂-SiMe₂OMe (1b). The X-ray crystal structure analysis of 3a revealed that 3a has an almost planar Ru-Si-O-Si four-membered chelate ring with short Ru-Si bonds (2.316(3) and 2.311(3) Å) and long Si⋯O bonds (1.801(7) and 1.793(7) Å). 3a reacts with MeOH instantaneously to give Cp(OC)Ru(H)(SiMe₂OMe)₂ (4) quantitatively. Photolysis of CpM-(CO)₂SiMe₂SiMe₂OMe (1b, M = Ru; 1c, M = Fe) or Cp(OC)M{SiMe₂⋯O(Me)⋯SiMe₂} (3a, M = Ru; 3b, M = Fe) with the photochemical silylene precursor (SiMe₂)₆ by means of a low-pressure Hg lamp afforded a mixture of 3a or 3b, disilanyl-silylene complexes Cp-(OC)M{=SiMe₂←O(Me)SiMe₂SiMe₂} (5a, M = Ru; 5b, M = Fe), and (SiMe₂)₅. Two possible mechanisms for the addition of dimethylsilylene to 3 to give 5 were proposed.