Water-soluble cobalt(II) and copper(II) complexes of 3-(5-chloro-2-hydroxy- 3-sulfophenylhydrazo)pentane-2,4-dione as building blocks for 3D supramolecular networks and catalysts for TEMPO-mediated aerobic oxidation of benzylic alcohols

摘要

A new water-soluble β-diketone azo derivative 3-(5-chloro-2-hydroxy-3- sulfophenylhydrazo)pentane-2,4-dione(H_3L, 1) was synthesized and found to be stable in DMSO solution and in the solid state in the hydrazo tautomeric form. Its water-soluble complexes [Co(HL)(en)(H_2O)] ·4H_2O (3) and the zwitterionic [Cu(L)(Hen)(H_2O)] (4), with buffering properties, were prepared by reaction of cobalt(II) and copper(II) nitrates with the ethylenediammonium (H_2en) salt of 1, (H_2en)(HL) (2). In the formation of 3 and 4, 1 is a chelating ligand, and a crucial synthetic and structural role is played by en, allowing the organization of water-soluble assemblies and influencing the overall 3D supramolecular arrangement. Compound 3 is the first cobalt complex with an azo derivative of a β-diketone. Complex 4 acts as catalyst precursor for the aerobic TEMPO-mediated selective oxidation of benzylic alcohols to the corresponding aldehydes in aqueous media.