Coordination chemistry of thioether ligands

Abstract

A series of thiophene-containing thioethers (L1 = l,6-bis(2-thienyl)-2,5-dithiahexane; L2 = 1, 9-bis(2-thienyl)-2,5,8-trithianonane; L3 = 1, 9-bis(2-thienyl)-2,8-dithia-5-oxononane; L4 = 1, 7-bis(2-thienyl)-2,6-dithiaheptane) were prepared. Preparation of copper(II), copper(I), molybdenum (0), and tungsten(0) complexes with these ligands and L5 (L5= 2,5,7,10-tetrathia12 thiophenophane) are described. The complexes were studied by nmr, esr, ir, electronic spectroscopy and by magnetic, X-ray structural and electrochemical methods. The structure and properties of the copper complexes were studied in both the solid state and in solution and the structures were correlated with the spectroscopic characteristics. It has been shown that the structures of the copper-thioether complexes change when they dissolve and the extent of the change depends on the solvent and the solution concentrations. Variable temperature nmr studies have been used to examine the stereochemically non-rigid processes of molybdenum and tungsten carbonyl complexes of several of the ligands. At room temperature, all are undergoing rapid inversion of configuration at their metal-bound sulfurs by a solvent-independent process. No evidence of any 1,4-heteroatom fluxional processes was found at room temperature, but at elevated temperatures an unprecedented acyclic 1,4-heteroatom binding site fluxionality in Mo(CO)₄∙L2 has been observed. The molecular structures of CuCl₂∙2Ll, CuCl₂∙L3, CuBr∙L3, and W(CO)₄∙L5 have been determined by X-ray methods.