Synthesis and Characterization of a Dicationic Dihydrogen Complex of Iridium with a Bis-carbene Ligand Set

Reaction of [Cp*Ir(CH3CN)3][PF6]2 with methylenebis(N-methylimidazolium) iodide in the
presence of Et3N affords [Cp*Ir(C−C)I]PF6 (1) (C−C = bis-carbene). The structure of complex
1 was confirmed by X-ray crystallography. The chloride analogue [Cp*Ir(C−C)Cl]X (2) was
similarly prepared from [Cp*Ir(CH3CN)3][PF6]2 (X = PF6) or [Cp*IrCl2]2 (X = Cl) and
methylenebis(N-methylimidazolium) chloride. Reaction of 2 (X = Cl) with Et3SiB(C6F5)4 under
hydrogen gas gives the dicationic dihydrogen complex [Cp*Ir(C−C)(H2)]2+ (3). Complex 3 is
identified as a dihydrogen complex based on T1(min) = 37 ms for the hydride resonance (240
K, 750 MHz) and JHD = 23.5 Hz in the partially deuterated analogue.