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

A new water-soluble beta-diketone azo derivative - 3-(5-chloro- 2-hydroxy-3-sulfophenylhydrazo)pentane-2,4-dione (H3L, 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)(H2O)]center dot 4H(2)O (3) and the zwitterionic [Cu(L)(Hen)(H2O)] (4)(r) with buffering properties, were prepared by reaction of cobalt(II) and copper(II) nitrates with the ethylenediammonium (H(2)en) salt of 1, (H(2)en)(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 beta-diketone. Complex 4 acts as catalyst precursor for the aerobic TEMPO-mediated selective oxidation of benzylic alcohols to the corresponding aldehydes in aqueous media.