Carboxylic Esters as Ligands. II. Transition metal complexes of Diethyl Acetonedicarboxylate, Ethyl Acetoacetate, and Diethyl oxaloacetate

Abstract

The preparation, infrared spectra, magnetic data, and reactions of a variety of transition metal complexes of diethyl acetonedicarboxylate are described. The infrared spectra indicate chelate ring formation with a metal-oxygen bond with the carbonyl group of the ester. Transesterification reactions with alcohols occur much less readily with these complexes than with the corresponding metal oxaloacetates. Bis(ethyl acetoacetato)copper(II) undergoes methanolysis rather than trans-esterification on refluxing with methanol to give a bright blue methoxy-bridged polymer with an abnormally low magnetic moment (μ_eff 1.14 B.M. at 17°), presumably indicating metal-metal interaction. The magnetic moments of various transition metal complexes of ethyl acetoacetate and diethyl oxaloacetate have also been determined. The β-keto esters have been condensed with 1,2-diaminoethane to give N,N?-bis Schiff bases which exist predominantly as the enamine tautomer in the solid state and in solution. Attempts to prepare copper(II) complexes of these Schiff bases in aqueous ethanol have been unsuccessful as the ligands rapidly hydrolyse in the presence of copper(II) ions.