On the Lewis Acidity of LiF
Abstract
Based on the recently developed pF Lewis acidity scale,' free gaseous LiF is a surprisingly strong Lewis acid, comparable to SiF4. It was therefore of interest to study whether a strong Lewis base, such as CsF, could transfer a fluoride ion to LiF with formation of a LiF2 anion. Theoretical calculations were carried out for LiF2 and show that free gaseous LiF2 is a linear, vibrationally stable species. Furthermore, the phase-diagram of the LiF/CsF system shows a eutectic at a 1:1 mole ratio that gives a distinct X-ray powder diffraction pattern. We have prepared this eutectic by fusion of a 1:1 mixture of LiF and CsF in a platinum crucible. Single crystals were obtained by slow cooling of the melt in a dry nitrogen stream. The resulting product was characterized by vibrational spectroscopy, and its crystal structure was determined. It is shown that CsLiF2 does not contain isolated LiF2 anions, but exhibits an interesting three-dimensional network of alternating tetra-coordinated LiF4 and octa-coordinated CsF8 units.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 2000
- Accession Number
- ADA408369
Entities
People
- A. Vij
- F. Tham
- J. A. Boatz
- K. O. Christe
- V. Vij
Organizations
- Air Force Research Laboratory