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)2SiMe2SiMe2OMe (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.

Photolysis of the 3-methoxytrisilanyl complex CpM(CO)2SiMe2SiMe2SiMe2OMe (1a, M = Ru; 1b, M = Fe) afforded the intramolecularly methoxy-stabilized disilanyl−silylene complex Cp(OC)M{SiMe2←O(Me)SiMe2SiMe2} (2a, M = Ru; 2b, M = Fe) as a primary product. Prolonged irradiation of the solution resulted in the decay of 2a,b with release of a dimethylsilylene moiety to give the methoxy-bridged bis(silylene) complex Cp(OC)M{SiMe2···O(Me)···SiMe2} (3a, M = Ru; 3b, M = Fe). The X-ray crystal structure analysis of 2a revealed that 2a has a five-membered chelate ring and the Ru−Si(silylene) bond (2.291(2) Å) is much shorter than the other Ru−Si bond (2.350(1) Å). It can be concluded from the bond lengths that the former possesses a partial double-bond character while the latter is a normal Ru−Si single bond. Photolysis of diisopropyl derivatives CpM(CO)2SiMe2Si i Pr2SiMe2OMe (4a, M = Ru; 4b, M = Fe) gave Cp(OC)M{SiMe2←O(Me)SiMe2Si i Pr2} (5a, M = Ru; 5b, M = Fe) exclusively, in which the positions of substituents on silicon atoms in 5a and 5b were determined by 29Si−1H COLOC and NOESY NMR spectra. A mechanism involving 1,2-migration of the methoxydisilanyl group to the metal center was suggested. Irradiation of the tetrasilanyl complex CpFe(CO)2SiMe2SiMe2SiMe2SiMe2OMe (6) caused a complicated reaction, giving at least five products having methoxy groups coordinated to silylene ligands.