Synthesis, crystal structure and thermal behaviour of fluoroaluminates of the composition (NH4)[M(H2O)(6)] (AlF6) (M = Zn, Ni), [Zn(H2O)(6)][AlF5(H2O)], and (PyH)(4)[Al2F10] center dot 4 H2O

Four new fluoroaluminates were obtained from fluoroacidic solutions of resp ective metal salts. The compounds of zinc (Ia: P2(1)/c, a = 12.688(3), b = 6.554(1), c = 12.697(3) Angstrom, beta = 95.21(3)degrees, V = 1051.5(4) Ang strom (3), Z = 4) and nickel (Ib: P2(1)/c; a=12.685(3), b=6.517(1), c=12.66 4(2)Angstrom, beta = 94.55(2)degrees, V = 1043.6(4) Angstrom (3), Z = 4) ar e isotypic and represent a new structure type consisting of two different c ations, NH4+ and [M(H2O)(6)](2+) and [AlF6](3-)-anions. [Zn(H2O)(6)] [AlF5( H2O)], (II: C2/m, a=10.769(2), b = 13.747(3), c=6.487(1)Angstrom, beta =100 .02(3)degrees, V=945.7(3) Angstrom (3), Z=4) is characterized by a H2O/F-di sorder in [AlF5(H2O)]-octahedra in two trans positions. (PyH)(4)[Al2F10]. 4 H(2)O (III: Cmc2(1), a=15.035(3), b = 20.098(4), c=12.750(4) Angstrom, V=53 63(2)Angstrom (3), Z=8), bioctahedral [Al2F10](4-) anions have been found f or the first time. The structures are described and discussed in comparison . The new compounds were used as precursors in order to obtain new AlF3-phase s. However, the thermal decomposition did not result in the formation of an y new metastable AlF3-phase. Instead, phase mixtures of either alpha -AlF3 and beta -AlF3 or AlF3 and MF2 were obtained.