A novel linkage isomeric pair of mixed ligand Ni(II) complexes with IM2py-κ²N,O and IM2py-κ²N,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-κ²N,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·PF ₆ has been synthesized by the direct reaction between [Ni(acac)(tmen)]PF₆ and IM2py. The X-ray analysis (monoclinic, P2₁lc, a = 15.378(2), b = 13.331(2), c= 16.560(2) Å, β= 116.377(6)°, Z = 4) demonstrated that the IM2py ligand is coordinated to Ni(II) as an unprecedent six-membered didentate chelate with the k ²N,O mode in 1. The corresponding linkage isomer, [Ni(acac)(tmen)(IM2py-κ²N,N)]PF₆ (2·PF ₆), 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·PF ₆ and an antiferromagentic one in 1·PF₆. These facts confirm a linkage isomeric pair of [Ni(acac)(tmen)(IM2py- κ²N,O)]⁺ (1) and [Ni(acac)(tmen)(IM2py- κ²N,N)]⁺ (2) with oxygen and nitrogen coordination, respectively, in the IM moiety.