Molecular structures and redox properties of oxorhenium(V) ‘3+1’ mixed ligand complexes with heterocyclic thiolates containing nitrogen

Reactions of chloro(3-thiapentane-1,5-dithiolato)oxorhenium(V) [ReO(SSS)Cl] with N-methyl-1H-imidazole-2-thiol (HL1) and 2-pyrimidinethiol (HL2) have been studied to form ‘3+1’ oxorhenium(V) complexes. In the absence of triethylamine, [Re(SSS)(HL1)]Cl (1a) was formed, while in the presence of triethylamine [Re(SSS)L1] (1b) and [Re(SSS)L2] (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/AgNO3, respectively, and are reduced to Re(IV) at −1.55 and −1.51 V with the dissociation of L1 or L2, followed by the quasi-reversible reductions to Re(III) at around −1.69 V, respectively.

Graphical abstractMolecular structures of [ReO(SSS)(HL1)]Cl and [ReO(SSS)(L2)] (SSS = 3-thiapentanedithiolate, HL1 = N-methyl-1H-imidazole-2-thiolate, L2 = 2-pyrimidinethiolate) have been studied and determined to be the distorted square pyramidal. The complexes [ReO(SSS)(L1)] and [ReO(SSS)(L2)] were found to be irreversibly oxidized to Re(VI) at around 0.8 and 1.0 V versus Ag/AgNO3, respectively. Moreover, it was clarified that these complexes are reduced to Re(IV) at around −1.5 V and further to Re(III) at around −1.7 V versus Ag/AgNO3. The following mechanism was proposed as the reduction process, i.e., the reduced Re(IV) complexes dissociate L1 or L2 to form ReO(SSS), which is reduced quasi-reversibly to Re(III).Figure optionsDownload full-size imageDownload as PowerPoint slide