Aquachlorobis[4,4,5,5-tetramethyl-2-(2-pyridyl)-4,5-dihydro-1H-imidazol-1-oxyl 3-oxide-κ2O1,N2]nickel(II) nitrate methanol disolvate monohydrate

The title complex, [NiCl(C12H16N3O2)(2) (H2O)]NO3.2CH(4)O.-H2O, was obtained from a methanolic solution of Ni(NO3)(2).6H(2)O, 2-pyridyl nitronyl nitroxide (2-NITpy) and (NEt4)(2) [CoCl4]. The equatorial coordination sites of the octahedral Ni-II centre are occupied by two chelating radical ligands, with the axial positions occupied by the Cl- and water ligands. The H2O-Ni-Cl axis of the complex lies along a crystallographic twofold axis, so that only half the cation is present in the asymmetric unit. The Ni-Cl bond length [2.3614 (17) Angstrom] is significantly shorter than distances typical of octahedral Ni-II centres [2.441 (5) Angstrom]. However, with only one nitrate anion per formula unit, the oxidation state of the metal must be assigned as Ni-II. The 2-NITpy ligands bend away from the equatorial plane, forming a hydrophobic region around the Cl atoms. Conversely, the ligated water molecule forms moderately strong hydrogen bonds with the disordered methanol solvent molecules, which in turn form interactions with the water of crystallization and the disordered nitrate anion. These interactions combine to give hydrophilic regions throughout the crystal structure.