Synthesis of Novel Terminal Iridium Phosphinidene Complexes

Abstract

Stable, crystalline iridium-complexed phosphinidenes, Cp*(L)IrPR, are readily synthesized by (a) the reaction of Cp*(L)IrCl2 (2, L = PPh3) with LiPHMes* and (b) dehydrohalogenation of Cp*(PH2R)IrCl2 (5, R = Mes*, Is, Mes) with in situ capturing of transient Cp*Ir⋮PR (4) with phosphines, phosphites, arsines, isocyanides, and carbon monoxide (L). Cp*Ir⋮PR eluded direct detection. The X-ray crystal structures are reported for Cp*(PPh3)IrPMes* (3) and Cp*(CO)IrPMes* (15). The more congested 3 has an E configuration for its IrP bond, whereas 15 is obtained in its Z form. The 31P NMR chemical shifts and 2JPP coupling constants are diagnostic for the E and Z forms. More shielded phosphinidene resonances and larger coupling constants are typical for the E isomers. These iridium-complexed phosphinidenes react with gem-diiodides to form phosphaalkenes, but not with carbonyl groups.