Photoinitiated Oxidative Addition of CF_3I to Gold(Ⅰ) and Facile Aryl-CF_3 Reductive Elimination

摘要

Herein we report the mechanism of oxidative addition of CF_3I to Au(Ⅰ), and remarkably fast C_(aryl)-CF_3 bond reductive elimination from Au(Ⅲ) cations. CF_3I undergoes a fast, formal oxidative addition to R_3PAuR' (R = Cy, R' = 3,5-F_2-C_6H_4, 4-F-C_6H_4, C_6H_5, 4-Me-QH_4, 4-MeO-C_6H_4, Me; R =Ph, R' = 4-F-C_6H_4, 4-Me-C_6H_4). When R' = aryl, complexes of the type R_3PAu(aryl)(CF_3)I can be isolated and characterized. Mechanistic studies suggest that near-ultraviolet light (λ_(max) =313 nm) photoinitiates a radical chain reaction by exciting CF_3I. Complexes supported by PPh_3 undergo reversible phosphine dissociation at 110℃ to generate a three-coordinate intermediate that undergoes slow reductive elimination. These processes are quantitative and heavily favor C_(aryl)-Ⅰ reductive elimination over C_(aryl)-CF_3 reductive elimination. Silver-mediated halide abstraction from all complexes of the type R_3PAu(aryl)(CF_3)I results in quantitative formation of Ar-CF_3 in less than 1 min at temperatures as low as -10℃.