On the synthesis and characterization of open-framework antimony(III) diphosphonates

Diphosphonates of antimony(III) were prepared by hydrothermal methods starting from Sb2O3 and the alkyldiphophonic acids, (H2O3P(CH2)(n)PO3H2), n = 1, 2 and 3, in the presence of HF. The methylenediphosphonic acid yields crystals of an oxydiphosphonate, Sb2O(O3PCH2PO3) (1): space group Pc, a = 4.6935(7), b = 7.2515(1), c = 11.1025(2) Angstrom, beta = 94.724(3)degrees, R-1(F) = 0.0397. Compound 1 is based upon a three-dimensional network of psi-trigonal bipyramidal [SbO4] units and (nearly) tetrahedral [(CH2)PO3] units. The three-dimensional framework of 1 features nine-rings formed by four Sb and five P atoms, forming narrow channels running parallel to the a axis. The ethylenediphosphonic acid gives crystals of Sb[O3P(CH2)(2)PO2(OH)] (2) space group Cc, a = 4.6707(2), b = 16.9992(6), c = 16.7699(6) Angstrom, beta = 98.00(1)degrees, R-1(F) = 0.0891, while the use of propylenediphosphonic acid produces Sb[O3P(CH2)(3)PO2(OH)] (3) space group P2(1)/c, a = 4.6635(6), b = 19.0545(2), c = 8.7608(1) Angstrom, beta = 103.87(4)degrees R-1(F) = 0.0352. The structures of 2 and 3 are closely related, both revealing open channels in three-dimensional framework architectures. (C) 2000 Editions scientifiques et medicales Elsevier SAS. All rights reserved.