Crystal Structure of cis-Dichlorobis(dimethylglyoxime)nickel(II)

Abstract

Dimethylglyoxime (H2dmg) has been used as an analytical precipitating and spectrophotometric reagent for nickel, and forms three types of mononuclear complex with nickel: [Ni(Hdmg)2] (1), [NiX2(H2dmg)2](X = Cl, Br), and M2[Ni(dmg)2](M = Li, Na, K).1 The crystal structure of 1 has already been reported, 2 but those of the two other types have not. In an aqueous solution, 1 is stable, while the two others decompose immediately upon the exposure to water. Because the lability of [NiCl2(H2dmg)2] (2) depends on its molecular structure, it is interesting to elucidate its lability by comparing the structure of 1 with that of 2. We report here on an X-ray single-crystal structure determination of 2.Nickel(II) chloride (1.3 g, 10 mmol) and H2dmg (1.0 g, 9 mmol) were added to acetone (100 ml). The suspension was heated at 50˚C, while stirring until the supernatant became blue. The hot suspension was filtered off, the filtrate was slowly evaporated at room temperature, and blue block single crystals were obtained.A blue block crystal having a size of 0.40 × 0.30 × 0.20 mm was used. The data were collected at 273 K with graphitemonochromatized Mo Kα radiation and corrected for Lorentz and polarization effects. An empirical absorption correction (µ (Mo Kα) = 17.6 cm -1 ) was applied, which resulted in transmission factors ranging from 0.516 to 0.703. The structure was solved by direct methods (SIR92). The non-hydrogen atoms were refined anisotropically. Coordinates of H atom bonded to each O atom were determined from a difference Fourier map and refined isotropically. Methyl H atoms were