Copper(II) Chelates of 2,4,6-Heptanetrione and Its Homologues

Abstract

Abstract Copper(II) chelates of heptane-2,4,6-trione as well as its methylated derivatives such as 3-methylheptane-2,-4,6-trione, 3,5-dimethylheptane-2,4,6-trione, and 2-methoxy-2-heptene-4,6-dione have been synthesized. All the ligands gave 1 : 2 (metal ion: ligand) chelates. The first two ligands gave in addition binuclear 2 : 2 chelates. The fact that a 1 : 2 chelate was relatively easily converted into a 2 : 2 chelate and the conversion occurred more easily with the chelate of the first ligand than with that of the second one was interpreted by the steric effect of the methyl group. The structures of the 1 : 2 and 2 : 2 chelates were discussed on the basis of spectroscopic and other data. Reversible addition of heterocyclic bases to the 2 : 2 copper chelates was observed, and the coordinating structure of pyridine adduct was found to be of a pentacoordinate square pyramid.