Spectra and structure of phosphorus-boron compounds. X* Microwave, infrared, and Raman spectra and structure of dimethylphosphineborane

The infrared (33–4000 cm−1) and Raman (0–3500 cm−1) spectra of (CH3)2HPBH3, (CH3)2DPBH3, and (CH3)2HPBD3 have been recorded for the solid state at low temperature. The Raman spectra and polarization have been measured for the liquid state. The spectra have been interpreted in detail on the basis of Cs molecular symmetry. The barrier to internal rotation of the CH3 group in the solid state was found to be 3.8 kcal/mole. The microwave spectrum of (CH3)2HP11BH3, (CH3)2HP10BH3, (CH3)2DP11BH3, (CH3)2DP10BH3, (CH3)2HP11BD2H, and (CH3)2HP11BD3 was recorded from 18.0 to 40.0 GHz. An rs structure was determined for the BH3 group and an r0 structure was obtained from a least squares fit for the remainder of the structural parameters. The following molecular parameters were determined: r(BHs) = 1.212±0.005 Å, r(B–Ha) = 1.216±0.005 Å, r(P–B) = 1.898±0.010 Å, r(P–C) = 1.813±0.010 Å, r(P–H) = 1.414±0.009 Å, CPB = 114.6±1.0°, CPC = 105.4±1.0°, PBHs = 104.91±0.4°, PBHa = 104.81±0.4°, and BPH = 118.1±4.0°. The r(C–H) distance (1.093 Å) and the PCH angle (110.15°) were assumed. A dipole moment of |μa| = 4.77±0.02 D, |μc| = 0.90±0.05 D, and |μt| = 4.85±0.06 D were determined from the Stark effect.