The conditions of formation of heterometallic complexes in the GeCl4 (SnCl4)-citric acid-M(CH3COO)2-H2O systems. The crystal and molecular structures of [M(H2O)6][Ge(HCit)2] • 4H2O (M = Mg, Mn, Co, Cu, Zn) and [M(H2O)6][Sn(HCit)2] • 4H2O (M = Mg, Co, Ni)

Fourteen bis(citrato)germanates(IV) and bis(citrato)stannates(IV) were prepared, in particular, [M(H2O)(6)][Ge(HCit)(2)] center dot 4H(2)O (M = Mg (I), Mn (II), Fe (III), Co (IV), Ni (V), Cu (VI), Zn (VII)) and [M(H2O)(6)][Sn(HCit)(2)] center dot nH(2)O (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(4)Cit is citric acid). The purity and the composition of the products were determined by a set of physicochemical methods including elemental analysis, thermogravimetry, 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(H2O)(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.