Microwave Spectrum, Structure, and Dipole Moment of Cyclopropylphosphine

The microwave spectra of three isotopic species of cyclopropylphosphine have been analyzed. The conformation of the molecule is the symmetric one allowing maximum interaction of the lone pair electrons of phosphorus with the intra-annular orbitals of the cyclopropyl ring. A structure compatible with the observed moments of inertia yields, along with other parameters, a C–P bond distance of 1.834 Å, distinctly shorter than that observed in other organic phosphine derivatives. The dipole moment is found to be 1.16 D.