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(NO 3 ) 3 ·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 Cr 3+ 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(NO 3 ) 3 ·9H 2 O with K 2 (Cpdc) affords the 3D polymeric complex [KCr(Cpdc) 2 (H 2 O) 2 ] n ( I ) formed by the bis-chelate anionic fragments [Cr(Cpdc) 2 (H 2 O) 2 ] – . Under similar conditions, the use of Na 2 (Cpdc) and Li 2 (Cpdc) results in the formation of the 3D polymers [Na 4 Cr(Cpdc) 3 (H 2 O) 6 (NO 3 )] n ( II ) and {[Li 8 Cr 2 (Cpdc) 8 (H 2 O) 5 ]·H 2 O} 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 )).