New cesium hydrogen selenate phosphates: Synthesis and crystal structures

Three new compounds, Cs-4(SeO4)(HSeO4)(2)(H3PO4) (I), Cs-3(HSeO4)(2)(H2PO4) (II), and Cs-5(HSeO4)(3)(H2PO4)(2) (III), were synthesized from water solu tions of CsHSeO4/CsH2PO4. According to X-ray single-crystal analysis, the c ompounds have the following crystal data: I, monoclinic, space group P2(1), a 5.915(1) Angstrom, b = 13.797(3) Angstrom, c = 11.828(2) Angstrom, beta = 95.11(3)degrees, V = 961.4 Angstrom(3), Z = 2, R-1 = 0.0384; II, monoclin ic, space group P2(1)/n, a = 20.281(8) Angstrom, b = 8.039(4) Angstrom, c = 9.160(4) Angstrom, beta = 99.96(4)degrees, V = 1470.9 Angstrom(3), Z = 4, R-1 = 0.0580; III, monoclinic, space group C2/c, a = 33.855(8) Angstrom, b = 7.978(2) Angstrom, c = 9.217(2) Angstrom, beta = 101.00(2)degrees, V = 24 43.7 Angstrom(3), Z = 4, R-1 = 0.0519. All three compounds have in common a coordination number of cesium of 10 or 10+1, with Cs-O distances from 2.9 to 3.8 Angstrom. P and Se atoms form the individual tetrahedra with differe nt I-I-bonding connectivity in structures I-III. PO4-SeO4 layers with attac hed SeO4 groups are present in I. Structure II contains a three-dimensional hydrogen bonding network, whereas structure III is characterized by PO4-Se O4 bands to which additional SeO4 tetrahedra are attached. (C) 1998 Academi c Press.