Aufbau und Abbau von (NH4)[BF4] und H3N-BF3Professor Dieter Naumann zum 60. Geburtstag gewidmet
作者:Dirk Göbbels、Gerd Meyer
DOI:10.1002/1521-3749(200208)628:8<1799::aid-zaac1799>3.0.co;2-l
日期:2002.8
(NH4)[BF4] is produced as single crystals during the reaction of elemental boron and NH4HF2 (B : NH4HF2 = 1 : 2) and NH4F (B : NH4F = 1 : 4), respectively, in sealed copper ampoules at 300 degreesC. The crystal structure (baryte type, orthorhombic, Puma, Z = 4) was redetermined at ambient temperature (a = 909.73(18), b = 569.77(10), c = 729.47(11) pm, R-all = 0.0361) and at 140 K (a = 887.3(2), b = 574.59(12), c = 717.10(12) pm, R-all = 0.0321). Isolated (NH4)(+) and [BF4](-) tetrahedra are the important building units. The thermal behaviour of (NH4)[BF4] was investigated under inert (Ar, N-2) and reactive conditions (NH3) with the aid of DTA/TG and DSC measurements and with in-situ X-ray powder diffraction as well. Finally, (NH4)[BF4] is decomposed yielding NH3 and BF3, BN is not produced under the current conditions. Colourless single crystals of H3N-BF3 were prepared directly from the components NH3 and BF3. The crystal structure was determined anew at 293 and 170 K (orthorhombic, Pbca, Z = 8, a = 815.12(10), b = 805.91(14), c = 929.03(12) pm, R-all = 0.0367; a = 807.26(13), b = 800.48(10), c = 924.31 (11) pm, R-all = 0.0292, T = 170 K). The crystal structure contains isolated molecules H3N-BF3 in staggered conformation with a B-N distance of 158 pm. The thermal behaviour of H3N-BF3 was studied likewise.