Synthesis and characterization of cobalt(II) and manganese(II) xylaratogermanates: The molecular and crystal structures of the [M(H2O)6][Ge(μ3-L)2{M(H2O)2}2] · 4H2O · nCH3CN Complexes (M = Co, n = 0; M = Mn, n = 1)

Abstract

A synthetic procedure was developed, and heteropolynuclear coordination compounds—the products of the interaction of germanium tetrachloride with xylaric (trihydroxyglutaric) acid HOOC-CH(OH)-CH(OH)-CH(OH)-COOH (H5L) and the acetates of the 3d metals Mn(II) and Co(II)—were prepared. The compounds were characterized by elemental analysis, thermogravimetry, and IR spectroscopy. The X-ray diffraction analysis of the [M(H2O)6][Ge(μ3-L)2{M(H2O)2}2] · 4H2O · nCH3CN complexes, where M = Co, n = 0 (I) and M = Mn, n = 1 (II), was performed. The crystals of I are monoclinic, a = 10.752(2) A, b = 11.830(2) A, and c = 10.772(2) A, β = 94.741(3)°, V = 1365.4(5) A3, Z = 2, space group P21/n, R1 = 0.0309 for 3200 reflections with I > 2σ(I). The crystals of II are triclinic, a = 9.5330(17) A, b = 9.7415(17) A, and c = 10.3935(18) A, α = 115.024(2)°, β = 97.580(3)°, γ = 111.535(3)°, V = 764.9(2)A3, Z = 1, space group $$P\bar 1$$ , R1 = 0.0621 for 3028 reflections with I > 2σ(I). The bimetallic anions [Ge(μ3-L)2{M(H2O)2}2]2−, the cations [M(H2O)6]2+, and crystal water molecules form the basis of compounds I and II (the acetonitrile molecule is also a constituent of compound II). In the centrally symmetrical trinuclear complex anion, the Ge(1) atom is bound to two M(1) atoms through two completely deprotonated bridging ligands. The Ge(1) atom is coordinated to the six alcohol oxygen atoms of two ligands L5− at the apexes of a distorted octahedron (the average Ge(1)-O distances in I and II are 1.8858(14) and 1.892(3)A, respectively). The coordination polyhedron of the M(1) atom in the complex anion is a strongly distorted octahedron. The base of the coordination polyhedron is formed by the two bridging alcohol oxygen atoms (the average M(1)-O distances in I and II are 2.1756(14) and 2.255(3) A, respectively) of two L5− ligands and by the oxygen atoms of two water molecules (the average M(1)-O distances in I and II are 2.0693(17) and 2.175(4) A, respectively). In the centrally symmetrical complex cation, the coordination polyhedron of the M(2) atom is a somewhat distorted octahedron. The M(2)-O(H2O) bond lengths in I and II vary in the ranges of 2.0137(17)-2.1555(17) and 2.140(5)-2.172(4) A, respectively (the average lengths are 2.0375(17) and 2.166(4) A, respectively). The cations and anions are joined by a branched system of hydrogen bonds.