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 (H 2 L 1 ) and bidentate N , N ‐dialkyl‐ N ′‐benzoylthiourea (HL 2 ) ligands were formed in high yields when (NBu 4 )[MOCl 4 ] (M = Tc or Re) or [ReOCl 3 (PPh 3 ) 2 ] was treated with mixtures of the proligands. Other approaches for the synthesis of the products are reactions of [MOCl(L 1 )] complexes with HL 2 or compounds of the composition [ReOCl 2 (PPh 3 )(L 2 )] with H 2 L 1 . The resulting air‐stable [MO(L 1 )(L 2 )] complexes possess potential for the development of metal‐based radiopharmaceuticals. [TcO(L 1 )(L 2 )] complexes are readily reduced by PPh 3 with formation of [Tc(L 1 )(L 2 )(PPh 3 )]. The resulting Tc III complexes undergo two almost‐reversible oxidation steps corresponding to one‐electron transfer processes.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)