Effect of Synthesis Conditions on the Composition and Structure of Chromium(III) Complexes with Cyclobutane-1,1-Dicarboxylic Acid Anions

The reaction of Cr(NO3)3·9H2O with potassium cyclobutane-1,1-dicarboxylate (K2(Cbdc)) in 1 : 3 ratio was studied. It was shown that, depending on the reaction conditions and the solvents used for synthesis and crystallization, compounds of various compositions and structures can be isolated from the reaction system. Conducting the reaction in water followed by recrystallization from ethanol and methanol results in isolation of 2D polymeric complexes [KCr(Cbdc)2(H2O)2]n (I) and {[K4Cr2(OMe)2(Cbdc)4(MeOH)6]· MeOH}n (II), respectively. The addition of excess KOH to the same reaction mixture and recrystallization from alcohols gives rise to the crystals of 3D polymeric compound [K3Cr(Cbdc)3(H2O)2]n (III). Conducting the reaction in methanol followed by slow diffusion of diethyl ether affords complex [K3Cr(Cbdc)3(MeOH)2(H2O)2]n (IV) with a 2D polymeric structure. The crystal structures of compounds I–IV were determined by X-ray diffraction (CIF files CCDC nos. 2006090 (I), 2006109 (II), 2006116 (III), and 2 006 117 (IV)).