Synthesis and Complexes of Heterocyclic Ligands.

The coordination chemistry of twenty chelating heterocyclic ligands, seven of which are new, is described. These ligands all contain heterocyclic ring systems that have previously received little attention in the literature. The specific ring systems involved are benzoxazoles, benzisoxazoles, benzothiazoles, benzotriazoles, 1,2,4- and 1,2,5- heterodiazoles, and the 1,4,2,5-dioxadiazene systems. Many of the complexes synthesised are of ruthenium(II). These include monoruthenium complexes of the type [Ru(bpy)2(L)] 2+, homodinuclear complexes {[(bpy)2Ru(µ-BL)Ru(bpy2)4+ with µ-BL representing a doubly bidentate bridging ligand} as well as heterodinuclear ruthenium/palladium and ruthenium/platinum {[(bpy)2Ru(µ-BL)MCl2]2+ with M = Pd/Pt} complexes. Also investigated are the coordination and supramolecular chemistry of many of the ligands with palladium(II), silver(I) and copper(II) metal ions. The X-ray crystal structures of five ligands and twenty complexes are described. An unexpected, previously unreported, heterocyclic transformation mediated by the Ru(bpy)22+ cation is also reported. A combination of multinuclear NMR, UV-visible spectroscopy, cyclic voltammetry and X-ray crystallography has been used to study the nature of the metal-ligand and metal-metal interactions in the complexes produced