Activation of O-H and C-O Bonds in Water and Methanol by a Vanadium-Bound Thiyl Radical.

The reaction of [V(PS3")]- (1) (PS3"=[P(C6 H3 -3-Me3 Si-2-S)3 ]3- ) with H2 O led to the formation of [VIV (PS3")(PS2"SH )]- (2) (PS2"SH =[P(C6 H3 -3-Me3 Si-2-S)2 (C6 H3 -3-Me3 Si-2-SH)]2- ), indicating a hydrogen atom transfer from H2 O to a bound thiolate in 1. Furthermore, the reaction of 1 with CH3 OH gave the generation of complexes 2 and 3, [VIV (PS3")(PS2"SCH3 )]- (PS2"SCH3 =[P(C6 H3 -3-Me3 Si-2-S)2 (C6 H3 -3-Me3 Si-2-SCH3 )]2- ), implying that C-O and O-H bonds are cleaved by 1. Quantum mechanical calculations were performed to provide the mechanistic understanding for the reactivity of 1 with water. A key transition state with a lower kinetic barrier is identified. It involves an O-H bond cleavage by a dissociated thiyl radical with an interaction between an OH group and a neighboring bound sulfur donor. To our knowledge, the reactivity of 1 represents a new mode for water activation conducted through cooperation between a metal-stabilized thiyl radical and a neighboring thiolato donor.