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.