Tetranuclear Nickel(II) and Cobalt(II) Complexes with 3,5-Dimethyl-1-pyrazolylmethanolato and Acetato Bridges Having a Cubane Core

Abstract

There have been considerable interest in the coordination chemistry of metal complexes with pyrazole and their derivatives owing to diverse coordination modes and relevance to a biological-active metal center with imidazole-like ligands.1–8 Recently, we studied metal complexes with a multidentate ligand, N,N,N¢,N¢-tetrakis(3,5-dimethyl-1-pyrazolyl)methyl-1,4phenylenediamine (tpmp), having the 1,4-phenylenediamine moiety, and isolated a dinuclear cobalt complex from a reaction of cobalt(II) chloride and tpmp consisting of two tetrahedral cobalt(II) atoms with two pyrazolato-nitrogen atoms of tpmp and two chloride atoms.6 In this study, we tried to extend this work to reactions with other metal salts, such as cobalt(II) acetate and nickel(II) acetate. We found totally different products with 3,5-dimethyl-1-pyrazolyl)methanolato (dmpm–), as shown in Fig. 1, [M4(dmpm)4(O2CCH3)4]·2CH3CN (M = Ni and Co). Here, we report on the crystal structures of these complexes. The ligand tpmp was synthesized by a method described in the literature.8 [Ni4(dmpm)4(O2CCH3)4]·2CH3CN To a solution of tpmp (54 mg, 0.1 mmol) in 10 cm3 of acetonitrile was added 25 mg (0.1 mmol) of nickel(II) acetate tetrahydrate. The reaction mixture was stirred overnight at room temperature. The resulting cleargreen solution was left for several days to yield green crystals. These crystals were collected, washed by acetonitrile, and dried under a vacuum. Yield, 35 mg. Anal. Found: C, 41.42; H, 5.27; N, 13.49%. Calcd for C36H54N10Ni4O12: C, 41.04; H, 5.17; N, Tetranuclear Nickel(II) and Cobalt(II) Complexes with 3,5-Dimethyl-1pyrazolylmethanolato and Acetato Bridges Having a Cubane Core