Aerial oxidation of primary alcohols and amines catalyzed by Cu(II) complexes of 2,2'-selenobis(4,6-di-tert-butylphenol) providing [O,Se,O]-donor atoms

Seven copper(II)-complexes 1-7 with the ligand 2,2'-selenobis(4,6-di-tert-butylphenol) providing [O,Se,O]-donor atoms have been isolated and characterized. Three of them 1, 2 and 3 are mononuclear, two 4 and 7 dinuclear and 5, 6 are trinuclear. The crystal structures of the complexes were determined by X-ray diffraction and the electronic structures were established by various physical methods including EPR and variable temperature (2-290 K) susceptibility measurements. The magnetic behaviour of the compounds 4-6 exhibits antiferromagnetic exchange coupling resulting in well-isolated S(t)= 1/2 ground state for 5 and 6 and a diamagnetic spin state for 4. Complexes 5 and 6 belong to the class of asymmetric trinuclear copper(II) complexes modelling the trinuclear copper site in multicopper oxidases. Complex 1 is a catalyst in the presence of a strong base for the aerial oxidation of primary alcohols to the corresponding aldehydes. A dinuclear complex, seemed to be 4, prepared in situ has been found to be a catalyst for the aerial oxidation of primary amines containing alpha-C-H atoms. Primary kinetic isotope effects show that H-abstraction from the alpha-carbon atom of a coordinated substrate (alcoholato or amine) is the rate-determining step in both cases. Two functional models for the metalloenzymes galactose oxidase and amine oxidases are thus described.