Hydrogen-Substituted Osmium Silylene Complexes: Effect of Charge Localization on Catalytic Hydrosilation

摘要

Metal silylene complexes have been proposed as intermediates in numerous catalytic reactions.While several routes to M=Si complexes have been established,the direct generation of silylenes from silanes (by oxidative addition of Si-H,followed by 1,2-hydrogen migration to the metal) appears to be crucial to their involvement in catalytic reactions.We recently reported evidence for a new hydrosilation mechanism catalyzed by the cationic ruthenium silylene complex [Cp(iPr_3P)(H)_2Ru=SiHPh centre dot Et_2O][B(C_6F_5)_4].The proposed pathway involves activation of two Si-H bonds to form a hydrogen-substituted silylene complex,followed by direct addition of an sp~2 Si-H bond to the alkene,H-migration from the metal center,and finally,reductive elimination of the hydrosilation product.To further our mechanistic understanding of this catalysis,and to explore the influence of electronic charge on reactivity of the Si-H group,neutral osmium silylene complexes were targeted.