Synthesis of Nickel(II) Complexes with 2,6-Dichlorophenyl-Substituted Pyridylpyrazole

The reaction of new 2-(2,6-dichlorophenyl)-5-(pyridin-2-yl)-2,4-dihydro-3H-pyrazol-3-one (L) with nickel(II) chloride resulted in the synthesis of the mononuclear nickel(II) complex [L₂Ni(CH₃OH)]Cl (I). The methanol solvate of complex I, [L₂Ni(CH₃OH)]Cl·3CH₃OH, and the free ligand L were characterized by X-ray diffraction (CCDC no. 2314989 (I), 2314988 (L)). It was shown that free L exists in solution in the pyrazolone form (according to the ¹H NMR data), while in crystalline complex I, L is in the pyrazolol form (X-ray diffraction data). Compound I is a rare example of a pyrazolol complex in which the oxygen atom is not involved in the coordination to the transition metal ion to give a coordination polymer.