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

Science  22 Dec 1995:
Vol. 270, Issue 5244, pp. 1970-1973
DOI: 10.1126/science.270.5244.1970


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(CH3)3)Ir(CH3)(ClCH2Cl)+BArf [Cp* = η5-C5(CH3)5, BArf = B(3,5-C6H3(CF3)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).