Détermination du champ de force de valence et des modes normaux de vibration des composés d'addition de l'acétone avec le trifluorure de bore

A valence force field for coordination compounds between acetone and boron trifluoride is computed: it is based upon vibrational spectra of six isotopic species and compared with the force field of free acetone and BF^?₄ ion. The formation of complex modifies the electronic state of the base and consequently the diagonal force constant of the CCO group and of the CH bonds. The force constant of the coordination bond (OB) is estimated as 2.10 mdyne Å^?1. Below 800 cm^?1 all modes involve motions of the acid and base; none corresponds to a stretching of the coordination bond.