Hemilabile Pincer-Type Hydride Complexes of Iridium

The ligand tBu2PC2H4NHC2H4NEt2 (PNHN) was synthesized starting from 2-(diethylamino)ethyl chloride hydrochloride and ethanolamine. Reaction of PNHN with [IrCl(COE)2]2 under H2 afforded the dihydride cis-IrH2Cl(κ3-PNHN) (1) in excellent yield. Treatment of 1 with tBuOK led to clean formation of the 16-electron amido complex IrH2(κ3-PNN) (2). Hydrogenation of 2 in toluene or ethyl acetate produced the trihydride mer-IrH3(κ3-PNHN) (3). This complex was unstable and dimerized to give [IrH2(κ2-PNHN)]2(μ-H)2 (4) with uncoordinated NEt2 groups. The structures of 1 and 4 were established by X-ray crystallography. Complex 2 demonstrated good catalytic activity for transfer hydrogenation of acetophenone, cyclohexanone, and butanone.