A new phosphorus bearing derivative of the methyl radical, CH2CP, studied by microwave spectroscopy and ab initio calculation

The microwave spectrum of the CH2CP radical in its B-2(1) ground electronic state was detected for the first time using a source-modulated microwave spectrometer. The radical was generated in the cell by a dc-glow discharge in a mixture of PH3 and C2H2. Fine structure was observed but no hyperfine structure pertaining to the phosphorus and hydrogen nuclei could be resolved. In total 110 spectral lines were measured for the K-structure and fine structure of eight rotational transitions in the 300-380 GHz region. The rotational, centrifugal distortion, and spin-rotation coupling constants were obtained by a least-squares analysis of the measured frequencies. On the basis of accompanying coupled cluster calculations an accurate equilibrium structure could be established; r(e)(CH) = 1.0816(5) Angstrom, alpha(e)(HCH) = 118.22(5)degrees, R-1e(CC) = 1.3418(10) Angstrom, and R-2e(CP) = 1.5889(10) Angstrom. The equilibrium dipole moment is predicted to be mu(e) = - 1.15 D, with the negative end at the phosphorus site. (C) 1998 American Institute of Physics.