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

Abstract

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 [V^IV (PS3")(PS2"S^H )]^- (2) (PS2"S^H =[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, [V^IV (PS3")(PS2"S^CH3 )]^- (PS2"S^CH3 =[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.

Keywords: density functional calculations; methanol activation; radical reactions; thiyl radical; vanadium; water activation.