It is well established that when (Tc-99m) pertechnetate (TcO4???) is reduced by a reducing agent, such as stannous chloride, in the presence of chelating ligands such as, but not restricted to, those containing N2S2, N2SO, N3S and NS3 moieties, complexes of (TcO)N2S2, (TcO)N2SO, (TcO)N3S and (TcO)NS3 are formed (Meegalla et al.