Thiocarbamoylbenzimidoyl chlorides, PhC(Cl)=N-(C=S)-(NRR2)-R-1, react with 2-(iminodiacetic acid)benzylamine under formation of the potentially pentadentate ligands H3L (R-1, R-2 = Et) and H3L-COOEt (R-1 = Me, R-2 = C6H4-4-COOEt) in high yields. Hydrolysis of H3L-COOEt in NaOH/MeOH gives quantitatively another benzamidine ligand H3L-COOH. The novel ligands readily react with (NBu4)[MOCl4] (M = Re, Tc) under formation of stable complexes with the general composition [MOM], in which they are triply deprotonated and fully occupy the remaining five coordination positions of the {MO}(3+) cores. In a "proof-of-principle" reaction for possible bioconjugations, the complex [ReO(L-COOH)] has been labeled with triglycine ethyl ester in high yields.