Crystal structures of Ti(NH4)2P4O13 and Sn(NH4)2P4O13

The characteristics of crystal structures of the titanium(IV) diammonium (Ti(NH4)(2)P4O13) and tin(IV) diammonium (Sn(NH4)(2)P4O13) tetraphosphates, which are isostructural with similar silicon(IV) and germanium(IV) salts, have been obtained by the Rietveld method using X-ray powder diffraction data. The compounds crystallize in the triclinic system, space group P (1) over bar, Z = 2, a = 15.0291(7) angstrom, b = 7.9236(4) angstrom, c = 5.0754(3) angstrom, alpha = 99.168(3)degrees, beta = 97.059(3)degrees, gamma = 83.459(3)degrees for Ti(NH4)(2)P4O13 and a = 15.1454(7) angstrom, b = 8.0103(5) angstrom, c = 5.1053(3) angstrom, alpha = 99.898(6)degrees, beta = 96.806(3)degrees, gamma = 83.881(4)degrees for Sn(NH4)(2)P4O13. The structure is refined in the isotropic approximation using the pseudo-Voigt function: R (p) = 0.077, R-Bragg = 0.045, R-F = 0.057 for Ti(NH4)(2)P4O13; R (p) = 0.082, R-Bragg = 0.044, R-F = 0.046 for Sn(NH4)(2)P4O13. The hydrogen atoms of the ammonium cations are placed in the calculated positions. A comparative analysis of the structures of the compounds of the M-IV(NH4)(2)P4O13 (M-IV = Si, Ge, Ti, Sn) series has been carried out.