Mixed‐Ligand Complexes of Technetium and Rhenium with Tridentate Benzamidines and Bidentate Benzoylthioureas

Mixed‐ligand complexes of technetium(V) or rhenium(V) containing tridentate N‐[(dialkylamino)(thiocarbonyl)]benzamidine (H2L1) and bidentate N,N‐dialkyl‐N′‐benzoylthiourea (HL2) ligands were formed in high yields when (NBu4)[MOCl4] (M = Tc or Re) or [ReOCl3(PPh3)2] was treated with mixtures of the proligands. Other approaches for the synthesis of the products are reactions of [MOCl(L1)] complexes with HL2 or compounds of the composition [ReOCl2(PPh3)(L2)] with H2L1. The resulting air‐stable [MO(L1)(L2)] complexes possess potential for the development of metal‐based radiopharmaceuticals. [TcO(L1)(L2)] complexes are readily reduced by PPh3 with formation of [Tc(L1)(L2)(PPh3)]. The resulting TcIII complexes undergo two almost‐reversible oxidation steps corresponding to one‐electron transfer processes.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)