C–H activation on a diphosphine and hydrido-bridged diiridium complex: generation and detection of an active IrII–IrII species [(Cp*Ir)2(μ-dmpm)(μ-H)]+

Abstract

Reaction of [Cp*Ir(μ-H)]₂ (5) (Cp* = η⁵-C₅Me₅) with bis(dimethylphosphino)methane (dmpm) gives a new neutral diiridium complex [(Cp*Ir)₂(μ-dmpm)(μ-H)₂] (3). Treatment of 3 with methyl triflate at −30 °C results in the formation of [(Cp*Ir)(H)(μ-dmpm)(μ-H)(Me)(IrCp*)][OTf] (6). Warming a solution of 6 above 0 °C brings about predominant generation of 32e⁻ Ir^II–Ir^II species [(Cp*Ir)(μ-dmpm)(μ-H)(IrCp*)][OTf] (7). Further heating of the solution of 7 up to 30 °C for 14 h leads to quantitative formation of a new complex [(Cp*Ir)(H)(μ-Me₂PCH₂PMeCH₂)(μ-H)(IrCp*)][OTf] (8), which is formed by intramolecular oxidative addition of the methyl C–H bond of the dmpm ligand. Intermolecular C–H bond activation reactions with 7 are also examined. Reactions of 7 with aromatic molecules (benzene, toluene, furan, and pyridine) at room temperature result in the smooth sp² C–H activation to give [(Cp*Ir)(H)(μ-dmpm)(μ-H)(Ar)(IrCp*)][OTf] (Ar = Ph (9); Ar = m-Tol (10a) or p-Tol (10b); Ar = 2-Fur (11)) and [(Cp*Ir)(H)(μ-dmpm)(μ-C₅H₄N)(H)(IrCp*)][OTf] (12), respectively. Complex 7 also reacts with cyclopentene at 0 °C to give [(Cp*Ir)(H)(μ-dmpm)(μ-H)(1-cyclopentenyl)(IrCp*)][OTf] (13). Structures of 3, 8 and 12 have been confirmed by X-ray analysis.