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

A high-yield synthesis of mixed-bridging-ligand Ru2 compounds, Ru2(D(3,5-Cl2Ph)F)(4-n)(OAc)nCl 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 Ru2(D(3,5-Cl2Ph)F)3(DMBA-I)Cl (3) and Ru2(D(3,5-Cl2Ph)F)2(DMBA-I)2Cl (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-Ru2(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 Ru2(D(3,5-Cl2Ph)F)(4-n)(DMBA-Ctriple bond]CSiMe3)nCl n = 1 (6) and 2 (8)] in excellent yields, which were converted to the corresponding bis(phenylacetylide) compounds Ru2(D(3,5-Cl2Ph)F)(4-n)(DMBA-Ctriple bond]CSiMe3)n(Ctriple bond]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.