Oxotechnetium(V) Complexes with a Novel Class of Tridentate Thiosemicarbazide Ligands

A novel tridentate thiosemicarbazide-type ligand class with an SNS donor set, H2L1, was prepared by reactions of N-[N′,N′-dialkylamino(thiocarbonyl)]benzimidoyl chlorides with thiosemicarbazides. H2L1 ligands readily react with (NBu4)[TcOCl4] in MeOH under the formation of red oxotechnetium(V) complexes of composition [TcOCl(L1)]. The monomeric, five-coordinate compounds are air-stable and bind (L1)2− tridentate in the equatorial coordination sphere. The compounds represent the first examples of oxotechnetium(V) complexes with NS chelate-bonded thiosemicarbazones.