THE CRYSTAL-STRUCTURE OF TETRAMETHYLAMMONIUM TETRAFLUOROBORATE, (CH3)4NBF4, AND THE DISORDER OF THE BF4- ION

M(r) = 160.96, tetragonal, P4/nmm, a = 8.231(3), c = 5.889(3) angstrom, V = 399.0(3) angstrom3, Z = 2, D(m) = 1.344, D(x) = 1.340 g cm-3, lambda(MoKalpha) = 0.7107 angstrom, mu = 1.32 cm-1, F(000) = 168, R = 0.089 for 267 unique reflections with I > 2 sigma(I). The interaction compound is formed by the tetramethylammonium cation and the tetrafluoroborate anion. The peculiar feature, of this crystal structure, at 298 K, is the disordered distribution of the fluoroborate tetrahedra, which has been also confirmed by NMR measurements.