Reactions of chloro(3-thiapentane-1,5-dithiolato) oxorhenium(V) [ReO(SSS)Cl] with N-methyl-1H-imidazole-2-thiol (HL(1)) and 2pyrimidinethiol (HL(2)) have been studied to form '3+1' oxorhenium(V) complexes. In the absence of triethylamine, [Re(SSS)(HL(1))] Cl (1a) was formed, while in the presence of triethylamine [Re(SSS) L(1)] (1b) and [ Re( SSS) L 2] ( 2) were produced. Molecular structures of complexes 1a and 2 were determined to be distorted square pyramidal by single crystal X-ray analytical method. From cyclic voltammetric studies, furthermore, it was proposed that complexes 1b and 2 are irreversibly oxidized to Re( VI) at around 0.84 and 1.01 V versus Ag/AgNO(3), respectively, and are reduced to Re(IV) at -1.55 and -1.51 V with the dissociation of L 1 or L 2, followed by the quasi-reversible reductions to Re(III) at around -1.69 V, respectively. (c) 2007 Elsevier B. V. All rights reserved.