Investigation of mixed divalent cation monophosphates: Synthesis, crystal structure, and vibrational study of CdBa2(HPO4)(2)(H2PO4)(2)

Chemical preparation, single-crystal X-ray structure, and infrared and pola rized Raman spectra of a new cadmium dibarium. bis(monohydrogen monophospha te) bis(dihydrogen monophosphate) are presented. The atomic arrangement con sists of anionic layers formed by HPO42- and H2PO4- groups connected to eac h other through strong hydrogen bonds, resulting in a two-dimensional netwo rk. These sheets are held together by six oxygen-coordinated Cd2+ and nine oxygen-coordinated Ba2+ Ions to build a three-dimensional framework, An ass ignment of lattice and internal vibrations in terms of symmetry species and approximate type of motion is given. A comparison with the vibrational fun damentals of the PO43- ion in the isostructural CaBa2(HPO4)(2)(H2PO4)(2) (C aBa2) is also discussed. Band positions are found to be largely independent of the positive ion. Crystal data for CdBa2(HPO4)(2)(H2PO4)(2) (CdBa2): M = 773.08 g mol(-1), monoclinic, space group P2(1)/c (No. 14), a = 5.434(4) Angstrom, b = 10.140(2) Angstrom, c = 12.298(2) Angstrom, beta = 100.43(3)d egrees, Z = 2, R-1/wR(2) = 0.024/0.066 [1858 observed reflections with I > 6 sigma (I)]. (C) 2001 Academic Press.