PHOTOCHEMICAL TREATMENT OF TRANSITION-METAL SUBSTITUTED DISILANES, (ETA-5-C5H5)FE(CO)2SI2ME4(C6H4X) (X = CL, CF3, NME2, OME, H), INCLUDING TRAPPING OF EXPELLED SILYLENE

A series of complexes (eta5-C5H5)Fe(CO)2Si2Me4Ar, FpSi2Me4Ar (Ar = C6H4X; X = H, p-Cl, m-CF3, o-Me, p-OMe, p-NMe2), have been synthesized and characterized. Photochemical treatment of the complexes in inert hydrocarbon solvents led to expulsion of the SiMe2 and/or SiMeAr fragments to yield FpSiMe3 and/or FpSiMe2Ar. The effects of the phenyl group substituents upon the product distribution indicate that in the intermediate silyl-silylene complexes (715-C5H5)Fe(CO) (=SiMe2)SiMe2Ar and (eta5-C5H5)Fe(CO)(=SiMeAr)SiMe3, the silylene portion is highly polar in the form Fe--Si+. Trapping experiments with Et3SiH during the photolysis of FpSiMe2SiMe3 yielded small but reproducible amounts of Et3SiSiMe2H, confirming the elimination of SiMe2. Significant amounts of siloxanes were also obtained from this photolysis. Photochemical generation of SiMe2 from (SiMe2)6 in the presence of FpSiMe3 resulted in a similar set of products, not the high yield of Et3SiSiMe2H obtained in the absence of FpSiMe3, indicating the great reactivity of SiMe2 with CO to form siloxane materials in the presence of metal complexes. GC/MS analysis of the reaction products from the photolyses of FpSiMe2SiMe2Ar also indicated some direct Si-Si bond cleavage to produce radicals that abstract H to form Me2ArSiH.