Boron Trifluoride: Application of the Keating Bendings to the Degenerate Vibrations

The harmonic force field of the E' species of BF₃ is studied. The Keating force field (KFF) is defined in analogy with the familiar VFF and CFF. In this connection three different coordinate sets are introduced. All of them contain bond stretchings. In addition, the valence coordinates include ordinary (Decius') bendings, the central coordinates nonbond stretchings, and Keating coordinates the Keating's bendings.

The experimental data of vibrational frequencies and Coriolis constants are reviewed extensively, as well as previous normal coordinate analyses. The different coordinate sets are tested for their usefulness as basis of force field approximations. For this purpose two different sets of experimental data are applied. The general conclusion goes in favour of the Keating coordinates.