Natural glycine unidentate on copper(II): a novel mode of bonding

Abstract

The compound of composition copper(II)–glycinate–picric acid–water (1/2/2/6) has been prepared and its crystal structure determined. It contains a centrosymmetric copper(II) ion, co-ordinated in a distorted octahedron by two water molecules in trans positions, two unidentate glycine moieties, linked to the metal in a trans arrangement via single carboxylate oxygens, and two more distant water molecules. The unidentate glycine species, probably zwitterions, represent an unexpected non-chelated form of the ligand. New similar compounds of (S)-alanine and (S)-lysine have also been prepared. The nature of the complexed ions in solution (‘speciation’) is considered.