Hydrogen Activation by an Iridium(III) Complex Bearing a Bidentate Protic NH,NR-NHC^∧Phosphine Ligand

Benzimidazole 2 bearing an N1-(biscyclohexylphosphine)­ethyl tether cleaves [IrCp*Cl2]2 to yield the mononuclear phosphine complex [3]. Heating of [3] yields via a formal C/N tautomerization complex [4]Cl with a protic NHC. Complex [4]Cl can be N3-deprotonated to give its conjugate base [6]. Complex [6] is able to activate molecular hydrogen under mild conditions, leading to complex [5]­BF4. The molecular structures of complexes [3], [4]­Cl, [5]­Cl, and [5]­BF4 have been determined by X-ray diffraction studies.