Transformations of Cobalt(II) Trifluoroacetates in 1,4-Dioxane: Solvent Effect on the Composition, Structure, and Crystal Packing of the Molecules

Abstract

The reaction of aqueous cobalt(II) acetate with trifluoroacetic acid in methanol affords complex [Co(OOCF3)2(OH2)4] (I). The same reaction in a methanol–benzene–dioxane mixture of solvents gives mononuclear complex [Co(OOCF3)2(OH2)6] ∙ O(CH2CH2)2O (II) in which the solvate dioxane molecule forms a single crystal by the formation of hydrogen bonds with coordinated water molecules. A similar reaction in pure dioxane affords trinuclear complex {Co3(OOСCF3)4(OH2)2(OOСCF3)2[O(CH2CH2)2O]2} ∙ 2HOOСCF3 ∙ 2O(CH2CH2)2O (III) containing both solvate and coordinated dioxane molecules. The crystallization of complex III from an isopropanol–dioxane mixture leads to complex [Co(OOСCF3)2(OH2)4] ∙ 2O(CH2CH2)2O (IV). The reaction of complex III with pyrazole (HРz) affords mononuclear complex [Co(OOСCF3)2(HРz)4] ∙ 2O(CH2CH2)2O (V). The reaction of complex I with HРz in methylene dichloride leads to mononuclear complex [Co(OOСCF3)2(HРz)4] (VI). The structures of coordination compounds I–VI are determined by X-ray diffraction analysis (СIF files CCDC nos. 1985667 (I), 1985666 (II), 1985671 (III), 1985670 (IV), 1985665 (V), and 1985669 (VI) at Т = 296(2) K and 1985668 (VI) at Т = 150(2) K).