Syntheses and properties of a series of oxo-centered triruthenium complexes with thiocyanate and nitrite as terminal ligand

Six new oxo-centered triruthenium complexes with NCS− or NO2− as a terminal ligand [Ru3O(CH3CO2)6(NCS)(L)2] {L = 4-dimethylaminopyridine (dmap) (1); L = pyridine (py) (2)}, [PPh4]2[Ru3O(CH3CO2)6(NCS)3] (3), [PPh4]2[Ru3O(CH3CO2)6(CO)(NCS)2] (4), and [Ru3O(CH3CO2)6(NO2)(L)2] {L = dmap (5); L = py (6)} were prepared. The thiocyanate is coordinated through N atom for all NCS− complexes. While dmap complex 5 was obtained as single isomer with N-coordinate nitrite, py complex 6 was obtained as a mixture of two isomers involving coordination mode of nitrite. The linkage isomerization is too fast to allow separation of these isomers and it was confirmed by saturation transfer technique on 1H NMR. These compounds show reversible redox behavior and the redox potentials suggest that these anionic ligands are slightly electron donating than pyridine derivatives. l structures of [Ru3O(CH3CO2)6(NCS)(C5H5N)2]·2CH2Cl2 were determined by X-ray crystallography. Although the complex has mixed terminal ligand, the Ru3O core is almost equilateral.