Co-ordination complexes of 2,2′-bi-2-thiazoline and 2,2′-bi-4,5-dihydrothiazine

Abstract

A number of complexes of 2,2′-bi-2-thiazoline. its 4,4′-dimethyl and 5,5′-dimethyl derivatives, and of 2,2′-bi-4,5- dihydrothiazine with Fe^II, Fe^III, Co^II, Ni^II, Cu^II, Zn^II, Hg^II, and Mo⁰ have been prepared. Structures ofthe complexes are deduced from infrared, electronic, ¹H n.m.r., and Mössbauer spectra, magnetic properties, and electrical conductances of solutions. The combined evidence afforded by these properties is consistent only with a co-ordination mode involving the α-di-imine group. Cyclic voltammctry of acetonitrile solutions of the tris-chelated iron(II) perchlorates shows two redox waves, one of which is ascribed to oxidation of the metal and the other to reduction of the co-ordinated ligand. The free-energy differences associated with these two couples correspond closely in magnitude to the energies of the metal-to-ligand charge-transfer bands occurring in the visible spectra. The properties of the complexes are compared with those of corresponding complexes of 2,2′-bipyridine and related ligands.