Synthesis and characterization of binuclear μ-oxorhenium mixed ligand complexes containing tridentate (SNSEt) and monodentate (SR) ligands

Abstract

The simultaneous action of the tridentate ligand (SNSEt), HSCH 2CH 2NHCH 2CH 2SCH 2CH 3, and a monodentate coligand (SR) on ReOCl 3(PPh 3) 2 in a ratio 1/1/1, results in new binuclear μ-oxorhenium complexes of the general formula [ReO(SNSEt)(SR)] 2O where R=C 6H 5 in 1, R= p-CH 3C 6H 4 in 2, R= p-CH 3OC 6H 4O in 3 and R=C 6H 5CH 2 in 4. They were isolated as crystalline products. Compound 2 consists of centrosymmetric dimeric units, ReO(SNSEt)(SR). The dimer is formed due to the linear bridging of a divalent oxygen atom between the two metal ions. The coordination about rhenium is distorted octahedral with the SNS donor atoms of the tridentate ligand and the monodentate thiol in the equatorial plane while the terminal and the bridging oxo-groups occupy the apical positions. Rhenium lies 0.15 Å out of the equatorial plane toward the terminal oxo-group. When the tridentate ligand, HSCH 2CH 2NHCH 2CH 2SCH 2CH 3, is used in excess, in addition to the expected [ReO(SNSEt)(SR)] 2O complex, the new binuclear complex [ReO(SN) 2] 2O, 5, is formed. Being the only product in the absence of the monodentate ligand, complex 5 consists of two independent ReO(SN) 2 units bridged by an oxygen atom. In this case, the ligand HSCH 2CH 2NHCH 2CH 2SCH 2CH 3 acts as a bidentate ligand and coordinates to the metal through the sulfur of the thiol and the nitrogen of the secondary amine.