Formation of Irida-β-ketoimines and PCN(amine)-Ir(III) Complexes by Reacting Irida-β-diketones with Aliphatic Diamines: Catalytic Activity in Hydrogen Release by Methanolysis of H(3)N–BH(3)

[Image: see text] Aliphatic diamines [(H(2)N(CH(2))(n)NHR) (a–d) n = 2: R = H (a), R = CH(3) (b), R = C(2)H(5) (c), n = 3, R = H (d) or rac-2-(aminomethyl)piperidine (e)] react with [IrH(Cl){(PPh(2)(o-C(6)H(4)CO))(2)H}] in THF to afford ketoimine complexes [IrH(Cl){(PPh(2)(o-C(6)H(4)CO))(PPh(2)(o-C(6)H(4)CN(CH(2))(n)NHR))H}] (2a–2d) or [IrH(Cl){(PPh(2)(o-C(6)H(4)CO))(PPh(2)(o-C(6)H(4)CNCH(2)(C(5)H(9)NH)))H}] (2e), containing a bridging N–H···O hydrogen bond and a dangling amine. Complex 2e consists of an almost equimolar mixture of two diastereomers. In protic solvents, the dangling amine in complexes 2 displaces chloride to afford cationic acyl-iminium compounds, [IrH(PPh(2)(o-C(6)H(4)CO))(PPh(2)(o-C(6)H(4)CNH(CH(2))(n)NHR))]X (3a–3d, X = Cl) or [IrH(PPh(2)(o-C(6)H(4)CO))(PPh(2)(o-C(6)H(4)CNHCH(2)(C(5)H(9)NH)))]Cl (3e) and (4a–4b, X = ClO(4)), with new hemilabile terdentate PCN(amine) ligands adopting a facial disposition. Complexes 3 contain the corresponding phosphorus atom trans to hydride and the amine fragment trans to acyl, while complexes 4 contain the amine trans to hydride. 3b and 4b consist of 80:20 and 95:5 mixtures of diastereomers, respectively, while 3e contains a 65:35 mixture. In the presence of KOH, intermediate cationic acyl-iminium complexes 3 transform into neutral acyl-imine [IrH(PPh(2)(o-C(6)H(4)CO))(PPh(2)(o-C(6)H(4)CN(CH(2))(n)NHR))] derivatives (5) with retention of the stereochemistry. Single-crystal X-ray diffraction analysis was performed on 2a, [3a]Cl, [3b]Cl, [4a]ClO(4), and 5b. Complexes 2, 3, and 5 catalyze the methanolysis of ammonia-borane under air to release hydrogen. The highest activity is observed for ketoimine complexes 2.