Crystal structures of isotypic ASb2F11 (A = Rb+, Tl+, O2+) and β-NH4Sb2F11, and the crystal structure of the low-temperature α-NH4Sb2F11

The crystal structures of RbSb2F11, TlSb2F11, O2Sb2F11 and beta-NH4Sb2F11 salts are isotypical and crystallize in the orthorhombic space group Cmc2(1) (No. 36). Crystal data of rubidium salt: a = 19.9981(3) angstrom, b = 11.5093(2) angstrom, c = 12.9623(2) angstrom, V = 2983.46(8) angstrom(3), and Z = 12 at 150 K. Unit cell parameters of corresponding thallium salt: a = 19.9876(5) angstrom, b = 11.5400(3) angstrom, c = 13.0267(3) angstrom, V = 3004.70(13) angstrom(3) and Z = 12 at 150 K. Reaction between NH4F and excess of SbF5 in anhydrous HF resulted in the single-crystal growth of beta-NH4Sb2F11: a = 20.0406(7) angstrom, b = 11.5534(4) angstrom, c = 13.0796(4) angstrom, V = 3028.42(18) angstrom(3), and Z = 12 at 296 K. The XRD experiments on NH4Sb2F11 at 240 and 150 K revealed another modification (alpha-NH4Sb2F11), which crystallizes in a (pseudo-hexagonal) monoclinic cell, space group P2(1), a = 11.5045(6) angstrom, b = 13.0437(3) angstrom, c = 11.5264(6) angstrom, beta = 119.818(7)degrees, V = 1500.67(15) angstrom(3), and Z = 6 at 240 K. Reaction between the O2SbF6 and SbF5 in anhydrous HF yielded O2Sb2F11 upon crystallization with a = 19.8472(5) angstrom, b = 11.1172(3) angstrom, c = 12.8259(3) degrees, V = 2829.97(12) angstrom(3), and Z = 12 at 150 K. The crystal structures of ASb(2)F(11) (A = Rb+, Tl+, O-2(+), NH4+) salts consist of dimeric Sb2F11- anions with partially disordered terminal fluorine atoms. Negative charge of the anions is compensated by single charged cations. Crystal structure of alpha-NH4Sb2F11 demonstrates similar motif as in beta-phase but with slightly re-arranged N-H center dot center dot center dot F hydrogen bonds. In the 100-296 K range, only rhombohedral phase was observed for NH4SbF6 (rhombohedral space group R (3) over bar, No. 148) with a = b = 7.5961(9) angstrom, c = 7.7176(9) angstrom, alpha = beta = 90 degrees, gamma = 120 degrees, V = 385.65(12) angstrom(3), and Z = 3 at 150 K).