Synthesis and Structure Determination of Rb_2(HSO_4)(H_2PO_4) and Rb_4(HSO_4)_3 (H_2PO_4) by X-ray Single Crystal and Neutron Powder Diffraction

摘要

Two new compounds, Rb_2(HSO_4)(H_2PO_4) and Rb_4(HSO_4)_3 (H_2PO_4), were synthesized from aqueous solutions of RbHSO_4/RbH_2PO_4. The compounds were characterized by X-ray single crystal analysis and neutron powder diffraction. For Rb_2(HSO_4)(H_2PO_4), room temperature and a low temperature modification were found. Accordin to X-ray crystal structure analysis, the compounds have the following crystal data: Rb_2(HSO_4)(H_2PO_4)(T=298 K), monoclinic, space group P2_1, a=7.448(3) A, b=7.552(2) A, c=7.632(3) A, #beta#=100.47(3),V=422.1(3) A, Z=2, R_1=0.033; Rb_2(HSO_4)(H_2PO_4) (T=160K), monoclinic, space group P2_1/c, a=11.555(3) A, b=7.536(2) A, c=9.593(2) A, #beta#=91.56(2), V=853.0(4) A, Z=4, R_1=0.041; Rb_4(HSO_4)_3(H_2PO_4), orthorhombic, space group P2_12_12, a=7.612(6) A, b=14.795(9) A, c=7.446(4) A, V=838.6(9) A, Z=2, R_1=0.045. The compounds have different coordination numbers of rubidium, being 7,8,9, or 10 with Rb-O distances from 2.9 to 3.3 A. In all cases there were difficulties in the allocation of sulfur and phosphorus due to the small differences in their radii and scattering factors. All structures are characterized by HSO_4~- and H_2PO_4~-, or disordered H_xS/PO_4~- tetrahedra connected to zigzag chains via hydrogen bridges. These chains are linked by additional hydrogen bonds to a layer-like hydrogen bonding system.