Unusually Mild and Selective Hydrocarbon C-H Bond Activation with Positively Charged Iridium(III) Complexes

Abstract

Certain transition metal complexes can react to break normally inert carbon-hydrogen (C-H) bonds, but these metal-based processes typically require photochemistry or elevated temperatures. In addition, most are unselective toward complicated functionalized substrates, which has limited their synthetic usefulness. The cationic iridium complex Cp*(P(CH 3 ) 3 )Ir(CH 3 )(ClCH 2 Cl) + BAr f − [Cp* = η 5 -C 5 (CH 3 ) 5 , BAr f = B(3,5-C 6 H 3 (CF 3 ) 2 ) 4 ] can thermally activate methane and terminal alkanes at unprecedentedly mild temperatures (10°C). This complex will also induce C-H activation reactions in various functionalized substrates at ambient temperatures. High steric and electronic selectivity is observed, leading invariably to only one reaction product; the initial C-H activation reaction is typically followed by rapid metal-based rearrangements (that is, functionalization).