N,O versus O,O coordination in β-imino diketonato complexes: Role of the metal center and of the imino substituent

Abstract

β-Imino carbonyl enolato metal(II) complexes of general formula [M((RCO)(R′CO)CC(R″)NH) 2] (M = Mn, Fe, Co, Ni, Cu, Zn, Pd, R = R′ = Me, R″ = CCl 3; M = Cu, Pd, R = R′ = Me, R″ = PhCO; R = Me, R′ = Ph, R″ = PhCO; R = R′ = Ph, R″ = PhCO) are easily synthesized by the reaction of metal(II) acetates with the proper β-enaminodiones in 1/2 molar ratio in ethanol at room temperature. In all the cases the trifunctional NOO β-imino carbonyl enolate ligand acts as bidentate to give ML 2 complexes, whose structure depends on the metal center and on the nature of the substituent R″ at the imino carbon. With R″ = CCl 3 an O,O coordination is observed for all the metal centers but one, in fact palladium(II) exhibits an N,O coordination through the imino nitrogen and one keto oxygen. By contrast with R″ = PhCO the ligand is always coordinated through the imino nitrogen and one keto oxygen atom.