Synthesis and structure of acid transition metal sulfates - Ti(H5O2)(SO4)(2)(H2O)(2) and Zr(H3O)(2)(SO4)(3)

From the ternary system M(n)(SO4)(n/2)/SO3/H2O (M(n+) = Zr4+, Ti3+) two new acid metal sulfates, Ti(H5O2)(SO4)(2)(H2O)(2) and Zr(H3O)(2)(SO4)(3), have been synthesized and structurally characterized. Ti(H5O2)(SO4)(2)(H2O)(2) crystallizes in the orthorhombic space group Pnma with cell parameters a = 9.858(5), b = 18.32(2), c = 5.437(7)A (Z = 4); Zr(H3O)(2)(SO4)(3) crystallizes in the triclinic space group Pi with cell parameters a = 5.092(2), b = 8.533(3), c = 12.388(6)Angstrom, alpha = 92.95(3)degrees, beta = 90.89(3)degrees, gamma = 94.35(3)degrees (Z = 2). In the titanium compound there are slightly distorted TiO6 octahedra with Ti-O distances between 1.99 and 2.09 Angstrom which are sharing corners with SO4 tetrahedra. Through hydrogen bonds layers are formed perpendicular to the b-axis. These layers are connected by H3O+ ions only. The structure of Zr(H3O)(2)(SO4)(3) consists of three different SO4 tetrahedra and distorted ZrO7 polyhedra which are connected via common corners and edges to form columns parallel to the a-axis. The Zr-O distances vary from 2.13 to 2.18 Angstrom for equatorial positions, significantly longer than the axial Zr-O distances with 2.05 Angstrom.