THE MERCURY-SENSITIZED PHOTOLYSIS OF PENTAMETHYLDISILANE

Two primary processes were observed in the Hg-sensitized photolysis of Me(5)Si(2)H: (I) hydrogen abstraction from the Si-H bond with a quant um yield of phi (I) = 0.85, (V) Si-Si bond breaking with phi (V) = 0.0 4. The hydrogen atoms formed in (I) undergo an H atom abstraction reac tion (k (3)), as well as substitution reactions at the Si centers resu lting in the formation of dimethylsilane and trimethylsilyl radical (k (4)) or trimethylsilane and dimethylsilyl radical (k(5)). The followin g branching ratios have been determined: k(3)/k(3) + k(4) + k(5) = 0.8 7, k(4)/k(3) + k(4) + k(5) = 0.096, k(5)/k(3) + k(4) + k(5) = 0.034. T he ratio of disproportionation (k (2)) to combination (k(1)) for the p entamethyldisilyl radical has been determined with MeOH as the scaveng er for 1-methyl-1-trimethylsilylsilene, 0.046 less than or equal to k( 2)/k(1) less than or equal to 0.071. A mechanism with pertinent rate c onstants has been proposed which accounts for the results.