Electrophilic cleavage reations of carbonsilicon bonds in neutral hexacoordinate silicon compounds: diorgano(phthalocyaninato)silicon

Abstract Preparations of diorgano(phthalocyaninato)silicon [(Pc)Si(R 1 )(R 2 )] and their reactions with N -bromosuccinimide (NBS), halogens, copper(II) halides, and 3-chloroperbenzoic acid (MCPBA) are reported. The alkylsilicon bonds are readily cleaved by NBS, halogens, and CuX 2 to give the corresponding alkyl halides. The reactivity of arylsilicon bonds toward NBS and halogen depends greatly on the electronic effect of the substituent on the benzene ring, but these bonds are almost inert to CuX 2 . The reactivity of the carbonsilicon bond towards NBS cleavage decreases in the order 4-MeOC 6 H 4 > n-C 8 H 17 > 4-MeC 6 H 4 > Ph ⪢ 3-CF 3 C 6 H 4 . Cleavage of alkylsilicon bonds may involve one-electron transfer from substrate to reagent and alkyl radical intermediates, while the electrophilic aromatic substitution mechanism may operate in the cleavage of arylsilicon bonds. [(Pc)SiR 2 ] are stable to MCPBA.