Pentamethyldisilyl Radical: Absolute Rate Constants for Its Formation and for Some Halogen Abstraction and Addition Reactions

Article abstract of DOI:10.1021/jo00363a010

Pentamethyldisilane is a better hydrogen donor than Et3SiH toward tert-butoxyl (k's for the overall reaction are 17 and 5.7 * 10⁶ M^-1 s^-1, respectively, at ca. 27 deg C) and toward primary alkyl radicals (k's for Si-H bond cleavage are ca. 10 and 1.0 * 10⁴ M^-1 s^-1, respectively, at 120 deg C).Absolute rate constants for various reactions of the Me3SiSiMe2<*> radical have been measured by laser flash photolysis at room temperature.In halogen atom abstractions, for example, the Me3SiSiMe2<*> radical is slightly less reactive than Et3Si<*>, but it is more reactive than n-Bu3Ge<*> and n-Bu3Sn<*>.Pentamethyldisilane would appear to offer an attractive alternative to n-Bu3SnH and n-Bu3GeH in radical chain reactions in which the desired product is formed by a hydrogen transfer not to the organic radical formed initially but to a second radical formed by a slow β-scission or rearrangement of the initial radical.