Hetero-hexanuclear ruthenium-nickel complexes containing 2,2'-biimidazolate dianion.Synthesis,ESI-MS and X-ray structure characterization

摘要

Efficient and direct synthesis of hexametallic complexes,[{(pap)_2Ru(biim)}_4M_2](ClO_4)_4(pap = 2-(phenylazo)pyridine,M = Ni [2a] and Cu [2b])based on the reaction of hydrated MCl_2 and [{(pap)_2Ru(biim)}_2Ag_2](ClO_4)_2 is elaborated.Synthesis of the 2,2'-bipyridine(bpy)analogue of [2a] is also described.Electrospray mass spectra of the complexes are analyzed which fully corroborate with their formulations.X-ray structure of a representative complex [{(bpy)_2Ru(biim)_2}_4Ni_2](ClO_4)_4,[3a] is reported.The structure consists of four octahedral [(bpy)_2Ru(biim)] units arranged around the Ni_2-moiety in a propeller type arrangement.The separation between the two nickel(II)ions in this complex is 2.803(7)A.The dependence of network topology on counteranions is also reported,which ultimately gives rise to a 2D sheet structure.The two nickel complexes [2a] and [3a] are diamagnetic and display resolved ~1H NMR spectra in dmso-d_6.These are intensely coloured and their visible range spectra are dominated by an intense transition(epsilon,37,000-38,000 M~(-1)cm~(-1))due to Ru d pi->pi*(ligand)transition.These complexes display multiple cyclic voltammetric responses,of which the responses at anodic potentials are ascribed to oxidations of the ruthenium centres.