A novel linkage isomeric pair of mixed ligand Ni(II) complexes with IM2py-2N,O and IM2py2N,N modes in [Ni(acac)(tmen)(IM2py)]+; synthesis and X-ray structure

This is the first report of a Ni(II) complex with the six-membered IM2py chelate coordinating via oxygen, [Ni (acac)(tmen)(IM2py-2N,O)]PF6 (1·PF6) (acac = acetylacetonate; tmen =N,N,N,N-tetramethylethylenediamine; IM2py = 2-(2-(pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxy). This new complex 1·PF6 has been synthesized by the direct reaction between [Ni(acac)(tmen)]PF6 and IM2py. The X-ray analysis (monoclinic, P21/c, a= 15.378(2), b= 13.331(2), c= 16.560(2), = 116.377(6)°, Z= 4) demonstrated that the IM2py ligand is coordinated to Ni(II) as an unprecedent six-membered didentate chelate with the 2N,O mode in 1. The corresponding linkage isomer, [Ni(acac)(tmen)(IM2py-2N,N)]PF6 (2·PF6), was obtained from the deoxygenation reaction of [Ni(acac)(tmen)(NIT2py)]PF6 with NaNO2. Variable-temperature measurements of the magnetic susceptibility and UV-vis absorption bands indicated a ferromagnetic interaction in 2·PF6 and an antiferromagentic one in 1·PF6. These facts confirm a linkage isomeric pair of [Ni(acac)(tmen)(IM2py-2N,O)]+(1) and [Ni(acac)(tmen)(IM2py-2N,N)]+(2) with oxygen and nitrogen coordination, respectively, in the IM moiety.