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, 4,4′-bipyridine) was investigated. The dinuclear complex [(μ-4,4′-bipy){CuII(TMPA)}2](CF3SO3)4 (1) was synthesised and analysed by X-ray diffraction (XRD). Magnetic studies revealed that this derivative displays very weak antiferromagnetic interactions between the two metal centres (2J=−0.69cm−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 [(μ-CN){CuII(TMPA)}2](PF6)(C14N8) (2) and [(μ-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.