Bis(citrato)germanates of bivalent 3d metals (Fe, Co, Ni, Cu, Zn): Crystal and molecular structure of [Fe(H2O)6][Ge(HCit) 2] • 4H2O

In continuation of a systematic study of bis(citrate)germanates, we synthesized a number of heterometallic germanium(IV) and 3d metal complexes based in citric acid (H4Cit) with the molecular formula [M(H2O)6][Ge(HCit)2] · nH2O, where M = Fe, n = 4 (I); Co, n = 2 (II); Ni, n = 2 (III); Cu, n = 1 (IV); Zn, n = 3 (V). The complexes were characterized by elemental analysis, X-ray diffraction, thermogravimetry, and IR spectroscopy. The X-ray diffraction analysis of compound I was performed. Crystals are monoclinic, a = 10.091(4) Å, b = 11.126(4) Å, c = 10.996(4) Å, β = 100.966(6)°, V = 1212.1(8) Å3, Z = 4, space group P21/n, R1 = 0.0561 for 2266 reflections with I > 2σ(I). Compound I is composed of centrosymmetric octahedral complexes-[Ge(HCit)2]2− anions and [Fe(H2O)6]2+ cations—and crystallization water molecules. Structural units in compound I are combined by a hydrogen bond system.