The Conditions of Formation of Heterometallic Complexes in the GeCl_4 (SnCl_4)-Citric Acid-M(CH_3COO)_2-H_2O Systems. The Crystal and Molecular Structures of [M(H_2O)_6][Ge(HCit)_2] 4H_2O (M = Mg, Mn, Co, Cu, Zn) and [M(H_2O)_6][Sn(HCit)_2] 4H_2O (M = Mg, Co, Ni)

摘要

Fourteen bis(citrato)germanates(IV) and bis(citrato)stannates(IV) were prepared, in particular, [M(H_2O)_6][Ge(HCit)_2] - 4H_2O (M = Mg (I), Mn (II), Fe (III), Co (IV), Ni (V), Cu (VI), Zn (VII)) and [M(H_2O)_6][Sn(HCit)_2] - nH_2O (M = Mg, n = 4 (VIII); Mn, n = 2 (IX); Fe, n = 4 (X); Co, n = 4 (XI); Ni, n = 4 (XII); Cu, n = 4 (XIII); Zn, n = 3 (XIV)) (H_4Cit is citric acid). The purity and the composition of the products were determined by a set of physicochemical methods including elemental analysis, thermogravim-etry, and IR spectroscopy. The structures of I, II, IV, VI, VII, VIII, XI, and XII were determined by X-ray diffractometry. All eight crystals composed of centrosymmetrical octahederal [M(H_2O)_6]~(2+) cations, [Ge(HCit)_2]~(2-) (or [Sn(HCit)_2]~(2-)) anions, and crystal water molecules are isostructural. The structural units in I, II, IV, VI, VII, VIII, XI, and XII are connected by systems of hydrogen bonds to form a three-dimensional framework.