The direct electrochemical synthesis of some metal derivatives of 3-hydroxy-2-methyl-4-pyrone

Abstract

The electrochemical oxidation of a metallic sacrificial anode (M = Zn, Cd, Sn, In, Cu) in a non-aqueous solution of 3-hydroxy-2-methyl-4-pyrone (= HL) yields the MLn complexes (M = Zn, Cd, Sn, Cu, n = 2; M = In, n = 3). Adducts of the type ML2•B (M = Zn, Cd, B = N,N,N′,N′-tetramethylethylenediamine (tmen); M = Cu, B = triphenylphosphine) were obtained by the reaction between the appropriate ligand (B) and the previously synthesized complexes (M = Zn, Cd), or by arranging for the initial electrolytic phase to include the base (M = Cu). The tin(II) compound shows the typical reactions of such low oxidation state species by reacting with iodine and ortho-quinones by oxidative addition. All compounds were characterized by elemental analysis and by IR, 1H and 13C nmr spectroscopy. The structure of CdL2•tmen was determined by X-ray crystallography, which identified the CdO4N2 kernel, and partial electron delocalization within the pyronate ring. Keywords: electrochemical synthesis, cadmium complexes, zinc complexes, tin(II) oxidation, 3-hydroxy-2-methyl-4-pyrone.