Synthesis, structure, and reactivity of iridium(III) complexes containing a 4,6-dimethyl-1,3-benzenediphenylimine pincer ligand

A nonheterocyclic bis(imino)aryl ligand with blocking methyl substituents, 4,6-dimethyl-1,3-benzenediphenylimine (NCHN), has been synthesized. Metalation via oxidative addition proceeds under mild conditions with the Ir(I) reagent [Ir(CH2═CH2)2(Cl)]2 to produce the Ir(III) product (NCN)Ir(CH2CH3)(Cl). Neutral nucleophiles such as water or triphenylphosphine add readily to the vacant sixth coordination site. Protonation of the ethyl group results in loss of ethane and formation of a dicationic chloride-bridged (NCN)Ir dimer. Alternatively, the chloride ligand can be abstracted from (NCN)Ir(CH2CH3)(Cl) to provide access to various neutral and cationic species, including (NCN)Ir(CH2CH3)(OAc) (OAc = acetate), [(NCN)Ir(CH2CH3)(bpy)][BF4] (bpy = 4,4′-bipyridine), [(NCN)Ir(CH2CH3)(NCCH3)2][BF4], and [(NCN)Ir(CH2CH3)(OH2)2][BF4], which is water soluble.