76173-91-6Relevant academic research and scientific papers
Tetrafluorophosphite, PF4-, anion
Christe, Karl O.,Dixon, David A.,Mercier, Hélène P. A.,Sanders, Jeremy C. P.,Schrobilgen, Gary J.,Wilson, William W.
, p. 2850 - 2858 (1994)
N(CH3)4+PF4-, the first example of a PF4- salt, has been prepared from N(CH3)4F and PF3 using either CH3CN, CHF3, or excess PF3 as a solvent. The salt is a white, crystalline solid which is thermally stable up to 150 °C where it decomposes to N(CH3)3, CH3F, and PF3. The structure of the PF4- anion was studied by variable temperature 31P and 19F NMR spectroscopy, infrared and Raman spectroscopy, SCF, MP2, local and nonlocal density functional calculations, a normal coordinate analysis, and single-crystal X-ray diffraction. The anion possesses a pseudo trigonal bipyramidal structure with two longer axial bonds and an equatorial plane containing two shorter equatorial bonds and a sterically active free valence electron pair. In solution, it undergoes an intramolecular exchange process by the way of a Berry pseudorotation mechanism. The vibrational frequencies observed for PF4- in solid N(CH3)4PF4 are in excellent agreement with those calculated for free gaseous PF4-. The X-ray diffraction study tetragonal, space group P4?21m, a = 8.465(3) A?, c = 5.674(2) A?, Z = 2, R = 0.0723 for 268 observed [F ≥ σ(F)] reflections suffers from a 3-fold disorder with unequal occupancy factors for the equatorial fluorine atoms of PF4- but confirms its pseudo trigonal bipyramidal structure and the axial P-F bond length calculated for the free ion.
