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 NO ₂ ^- as a terminal ligand [Ru ₃O(CH ₃CO ₂) ₆(NCS)(L) ₂] {L = 4-dimethylaminopyridine (dmap) (1); L = pyridine (py) (2)}, [PPh ₄] ₂[Ru ₃O(CH ₃CO ₂) ₆(NCS) ₃] (3), [PPh ₄] ₂[Ru ₃O(CH ₃CO ₂) ₆(CO)(NCS) ₂] (4), and [Ru ₃O(CH ₃CO ₂) ₆(NO ₂)(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. Crystal structures of [Ru ₃O(CH ₃CO ₂) ₆(NCS)(C ₅H ₅N) ₂] ·2CH ₂Cl ₂ were determined by X-ray crystallography. Although the complex has mixed terminal ligand, the Ru ₃O core is almost equilateral.