Aza and cyanobridged tripodal dinuclear copper(II) complexes: Electrochemical studies and structural evidence for an original azacyanocarbanion

Abstract : The reactivity of the mononuclear [Cu(TMPA)(L)] n+ complex (TMPA: tris(2-methylpyridine) amine, L: CH3CN, H2O) towards two different bridging species (tetracyanoethylene, 4,40-bipyridine) was investigated. The dinuclear complex [(mu-4,40-bipy)Cu-II(TMPA)(2)](CF3SO3)(4) (1) was synthesised and analysed by Xray diffraction (XRD). Magnetic studies revealed that this derivative displays very weak antiferromagnetic interactions between the two metal centres (2J = -0.69 cm(-1)). Solution studies (EPR spectroscopy and voltammetry) evidenced the lability of the bridged neutral bipyridine ligand in acetonitrile. The reaction of TCNE (TCNE: tetracyanoethylene) with the copper(I) complex [CuI(TMPA)(CH3CN)](PF6) afforded the salts [(mu-CN)Cu-II(TMPA)(2)](PF6)(C14N8) (2) and [(mu-CN)Cu(TMPA)(2)](PF6)(3) (3). Both compounds were characterised at solid state (XRD) and in solution. Compound (2) shows the presence of the organocyanide entity C14N82 corresponding to the new N-(tetracyanocyclopentadienyl)-3-aza-1,1,2-tricyanoprop- 1-enide ion. (C) 2013 Elsevier B. V. All rights reserved.