Spectra and structure of phosphorous—boron compounds. XVII. Vibrational analysis of silylphosphine—borane

Abstract Infrared spectra of solid SiH 3 PH 2 BH 3 and SiH 3 PH 2 BD 3 have been recorded from 80 to 3800 cm −1 . The Raman spectra of liquid and solid SiH 3 PH 2 BH 3 and SiH 3 PH 2 BD 3 have been recorded to 4000 cm −1 . A complete vibrational assignment is proposed and a normal coordinate calculation utilizing a valence force field model has been carried out. The force constant of 2.10 mdyn/A determined for the P-B stretching mode is consistent with the relative dissociative stability of the silylphosphine—borane adduct. This constant is compared to the corresponding quantity for several other phosphine—borane compounds. The number of lattice modes observed in the spectrum of the annealed solid is consistent with at least two molecules per unit cell.