A series of new tetradentate, nitrogen-sulfur donor proligands with amido or amino donor groups have been synthesized and their rhenium and technetium oxo-complexes prepared. The substitution pattern and length of the ligand backbone can be varied without affecting the co-ordination chemistry. The NS3H3 amido-proligands reacted rapidly with the technetium(V) precursor [TcOCl4]- at reflux in methanol to give the technetium(IV) species [TcO(NS3)]- in very high radiochemical purity (ca. 100%), but these complexes decompose over a period of hours or days. They also reacted with the rhenium(V) precursors [ReO2(py)4]Cl (py = pyridine) or [ReOCl3(PPh3)2] at reflux in methanol, but only in the presence of a base. Stable neutral rhenium(V) complexes of the type [ReO(NS3)] were formed, and the crystal structures of two determined. A reduced amino version of the NS3H3 proligand gave an analogous [ReO(NS3)] complex, and its crystal structure was determined.
