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

Abstract

Abstract A new water‐soluble β‐diketone azo derivative ― 3‐(5‐chloro‐2‐hydroxy‐3‐sulfophenylhydrazo)pentane‐2,4‐dione(H 3 L, 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 2 O)] · 4H 2 O ( 3 ) and the zwitterionic [Cu(L)(Hen)(H 2 O)] ( 4 ), 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 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.