Examples of cation exchange in new ionic oxovanadium(IV) complexes with anions of cyclobutane-1,1-dicarboxylic acid

The results on the synthesis and study of the crystal structures of compounds based on anionic fragments {VO(Cbdc)2}2– formed by oxovanadium(IV) (vanadyl, VO2+) and two chelate-bound anions of cyclobutane-1,1-dicarboxylic acid (H2Cbdc = C4H6(COOH)2) are presented. The use of ammonium cation NH4+ as a counterion in the synthesis leads to the formation of the mononuclear complex (NH4)2[VO(Сbdc)2(H2O)] · 2H2O (I). In the case of K+ cation, compound [K4(VO)2(Сbdc)4(H2O)4]n (II) with the 3D polymeric crystal structure is formed. The reaction of compound II with Mg(NO3)2 · 6H2O in an aqueous solution involves the partial substitution of K+ by Mg2+ cations to form 1D polymeric compound {[KMg0.5(VO)(Сbdc)2(H2O)6.5] · 3H2O}n (III), while a similar reaction of compound I does not afford the product of substitution of NH4+ by Mg2+ cations (CIF files CCDC 1551021–1551023 for compounds I–III, respectively).