MICROWAVE SPECTRUM AND CONFORMATIONAL COMPOSITION OF ALLENYLPHOSPHINE, $H_{2}C=C=CHPH_{2}$

Abstract

The microwave spectrum allenylphosphine has been investigated in the 8-62 GHz spectral region. Two conformers exist for this compound. The lone electron pair is syn-periplanar with the C=C-P link of atoms in one conformer, and anticlinal in the other form. A full assignment of the microwave spectrum of the more stable syn-periplanar rotamer has now been achieved. Its dipole moment has been measured. The $high-K_{-1}$ transitions of the a-type R-branch lines of the less stable anti-clinal conformer has also been assigned. The MW work has been augmented by high-level quantum chemical calculations to determine the energies of the two conformers at the G3 level of theory. They were also useful for a first prediction of the rotational constants and the dipole moment components. Finally, the structure of both conformers has been determined.