VIBRATIONAL SPECTRA AND STRUCTURE OF ORGANOPHOSPHORUS COMPOUNDS .8. TETRAMETHYLBIPHOSPHINE

The infrared spectra of gaseous, liquid, and solid tetramethylbiphosphine have been recorded from 4000 to 33 cm-1. The Raman spectra of the liquid and the solid have also been recorded and depolarization values have been measured. A comparison of the Raman spectra of the liquid and the solid indicates that the liquid consists of a mixture of trans and gauche conformers with the gauche structure slightly predominant. A similar comparison of the infrared and Raman bands of solid tetramethylbiphosphine below 750 cm-1 shows the mutual exclusion principle is operative, and it is concluded from this alternate forbidden ess that the trans-P2(CH3)4 isomer of C2h symmetry gives rise to these mutually exclusive bands. Assignments of the observed frequencies based on depolarization values, band positions, and relative intensities are presented for the molecule in both the C2 and C2h configurations. It is also shown that the two isomers may differ little in energy in the liquid state. © 1969, American Chemical Society. All rights reserved.