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 .

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 .