Synthesis and Structure of New M(II)/Cr(III) Coordination Compounds (M = Fe, Ni, Zn, Cd) with Cyclobutane-1,1-dicarboxylate Anions and 1,10-Phenanthroline

The reactions of chromium(III) potassium sulfate with the potassium salt of cyclobutane-1,1-dicarboxylic acid (H2Cbdc), 1,10-phenanthroline (Phen), and d-metal (FeII, NiII, ZnII) sulfate yielded ionic compounds [MII(Phen)3][CrIII(Cbdc)2(H2O)2][CrIII(Cbdc)2(Phen)]·nH2O (I: M = Fe, n = 9.5; II: M = Ni, n = 10; III: M = Zn, n = 9.1). The structures of I–III are formed by isolated [MII(Phen)3]2+ cations containing a d-metal ion and chromium(III)-containing anions of two types, [CrIII(Cbdc)2(H2O)2]– and [CrIII(Cbdc)2(Phen)]–. A similar reaction with cadmium sulfate resulted in the formation of the trinuclear molecular complex [CdIICr $$_{2}^{{{\text{III}}}}$$ (Cbdc)4(Phen)4]·7.5H2O (IV), in which two heteroleptic {CrIII(Cbdc)2(Phen)} blocks are bound to {Cd(Phen)2} moiety by bridging carboxylate groups. The crystal structures of compounds I–IV were determined by single crystal X-ray diffraction (CCDC nos. 2478737 (I), 2478738 (II), 2478739 (III), 2478740 (IV)).