Synthesis and Characterization of Trinuclear [Ni2Ru] Complexes with Bridging Thiolate or Selenolate Donors for Electrocatalytic Proton Reduction

Abstract

Two new trinuclear compounds [{Ni(xbSmS)}2Ru(phen)2](PF6)2 (1) and [{Ni(xbSmSe)}2Ru(phen)2](PF6)2 (2) were synthesized by the reaction of [Ni(xbSmS)] and [Ni(xbSmSe)], respectively, with cis-[Ru(phen)2(Cl)2] [H2xbSmS = 1,2-bis(4-mercapto-3,3-dimethyl-2-thiabutyl)benzene; H2xbSmSe = 1,2-bis(2-thiabutyl-3,3-dimethyl-4-selenol)benzene; phen = phenanthroline]. The two [Ni2Ru] complexes were characterized by ESI-MS, NMR spectroscopy, elemental analysis, single-crystal X-ray crystallography, and electrochemical techniques. X-ray structure determinations showed that the trinuclear complex cations in 1 and 2 contain two square-planar nickel centers bound in cis positions to the octahedral ruthenium ion by a bridging thiolate or selenolate donor atom. Electrocatalytic proton reduction occurs for both complexes in acetonitrile with the addition of varying amounts of acetic acid at a potential of –2.1 V vs. Fc+/Fc with faradaic yields of around 65 %.