Formation of Irida-β-ketoimines and PCN-Ir(III) Complexes by Reacting Irida-β-diketones with Aliphatic Diamines: Catalytic Activity in Hydrogen Release by Methanolysis of HN-BH.

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