Crystal structures of cobalt(II), nickel(II) and zinc(II) dichloro complexes bearing 2-pyridyl-substituted nitronyl nitroxide (NIT2py)

Abstract

The X-ray analysis of Co(II), Ni(II) and Zn(II) dichloro complexes containing 2-(2-pyridyl)-4,4,5,5-tetramethylimidazolin-1-oxyl 3-oxide (NIT2py) demonstrated that the Co(II) complex containing two dichloromethane solvate molecules, [CoCl 2(NIT2py) 2]·2CH 2Cl 2 ( 1), crystallizes in a space group P2 1/ c isomorphous to the corresponding Mn(II), Ni(II) ( 2) and Cu(II) complexes, and that the molecular structure of the complex having C i symmetry in 1 is isostructural to the above Mn(II), Ni(II) and Cu(II) complexes. A new Ni(II) complex having only one dichloromethane solvate molecule, [NiCl 2(NIT2py) 2]·CH 2Cl 2 ( 2′), could be crystallized from a mixture of dichloromethane, methanol and n-heptane. The ( OC-6-12)-[ trans(Cl)- trans(py)] geometrical structure of the Ni(II) complex in 2′ is identical to that in 2, but the puckered six-membered chelate rings formed via pyridyl-N and nitroxide-O atoms of NIT2py take the different conformations; i.e. the molecular symmetry is C 2 (racemate) with the λ, λ or δ, δ conformations in 2′ and C i (meso) with the δ, λ conformations in 2. In the case of Zn(II), a reaction of ZnCl 2 with NIT2py afforded purple crystals consisting of octahedral bis(NIT2py) and tetrahedral mono(NIT2py) complexes with hydration: [ZnCl 2(NIT2py) 2]·2[ZnCl 2(NIT2py)]·2/3H 2O ( 3). The geometrical structure of the octahedral Zn(II) complex in 3 was found to be ( OC-6-22)-[ cis(Cl)- trans(py)].