Technetium and rhenium oxo-complexes of new tetradentate ligands withN2S2 and NS3 donorsets

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 NS 3 H 3 amido-proligands reacted rapidly with the technetium(V) precursor [TcOCl 4 ] - at reflux in methanol to give the technetium(IV) species [TcO(NS 3 )] - 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 [ReO 2 (py) 4 ]Cl (py = pyridine) or [ReOCl 3 (PPh 3 ) 2 ] at reflux in methanol, but only in the presence of a base. Stable neutral rhenium(V) complexes of the type [ReO(NS 3 )] were formed, and the crystal structures of two determined. A reduced amino version of the NS 3 H 3 proligand gave an analogous [ReO(NS 3 )] complex, and its crystal structure was determined.