Preparation and characterization of a family of Ru2 compounds bearing iodo/ethynyl substituents on the periphery

A high-yield synthesis of mixed-bridging-ligand Ru-2 compounds, Ru-2(D(3,5-Cl2Ph)F)(4-n)(OAc)(n)Cl [n = 1 (1) and 2 (2)] was developed, where D(3,5-Cl2Ph) F is bis(3,5-dichlorophenyl) formamidinate. The acetate ligands in 1 and 2 can be quantitatively displaced with DMBA-I to yield Ru-2(D(3,5-Cl2Ph)F)(3)(DMBA-I)Cl (3) and Ru-2(D(3,5-Cl2Ph)F)(2)-(DMBA-I)(2)Cl (4), respectively, where DMBA-I is N,N'-dimethyl-4-iodobenzamidinate. When compound 2 was treated with 1 equiv of HDMBA-I, a unique Ru2 compound containing three different types of bidentate bridging ligands, cis-Ru-2(D(3,5-Cl2Ph)F)(2)(DMBA-I)(OAc)Cl (5), was obtained. Subsequent reactions between 3/4 and (trimethylsilyl)acetylene under Sonogashira coupling conditions resulted in Ru-2(D(3,5-Cl2Ph)F)(4-n)(DMBA-C equivalent to CSiMe3)(n)Cl [n = 1 (6) and 2 (8)] in excellent yields, which were converted to the corresponding bis(phenylacetylide) compounds Ru-2(D(3,5-Cl2Ph)F)(4-n)(DMBA-CtCSiMe(3))(n)(C equivalent to CPh)(2) [n = 1 (7) and 2 (9)]. Structural studies of several compounds provided insights about the change in Ru2 coordination geometry upon the displacement of bridging and axial ligands. Voltammetric studies of these compounds revealed rich redox characteristics in all Ru2 compounds reported and a minimal electronic perturbation upon the peripheral Sonogashira modification.