Synthesis and characterization of a dicationic dihydrogen complex of iridium with a bis-carbene ligand set

Reaction of [Cp*lr(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)C1]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)(H-2)](2+) (3). Complex 3 is identified as a dihydrogen complex based on T-1(min) = 37 ms for the hydride resonance (240 K, 750 MHz) and J(HD) = 23.5 Hz in the partially deuterated analogue.