Structure Forming Role of Alkaline Metal Cations in the Formation of Chromium(III) Complexes with Anions of Cyclopropane-1,1-Dicarboxylic Acid

The reactions of Cr(NO3)(3)center dot 9H(2)O with potassium, sodium, and lithium salts of cyclopropane-1,1-dicarboxylic acid (H(2)Cpdc) in a ratio of 1 : 3 are studied in order to elucidate the chemical assembling processes of the coordination polymers with Cr3+ and alkaline metal ions. The nature of the reacted alkaline metal cation affects the compositions and structures of the formed compounds. The reaction of Cr(NO3)(3)center dot 9H(2)O with K-2(Cpdc) affords the 3D polymeric complex [KCr(Cpdc)(2)(H2O)(2)](n) (I) formed by the bis-chelate anionic fragments [Cr(Cpdc)(2)(H2O)(2)](-). Under similar conditions, the use of Na-2(Cpdc) and Li-2(Cpdc) results in the formation of the 3D polymers [Na4Cr(Cpdc)(3)(H2O)(6)(NO3)](n) (II) and {[Li8Cr2(Cpdc)(8)(H2O)(5)]center dot H2O}(n) (III), respectively, containing the tris-chelate anionic fragments [Cr(Cpdc)(3)](3-). A distinctive feature of compound III is the presence in its structure of the {Li(Cpdc)}(-) fragments in which the Cpdc(2-) anion forms a six-membered chelate cycle with the Li+ ion. The crystal structures of compounds I-III are determined by X-ray diffraction (CIF files CCDC nos. 2031258 (I), 2031260 (II), and 2031261 (III)).