Spectra and structure of phosphorus–boron compounds. XXI. Microwave spectrum of ethylphosphine–borane
摘要:
The microwave spectra of CH3CH2PH2 11BH3, CH3CH2PH2 10BH3, and CH3CH2PH2 11BD3 have been recorded in the region 18.0–39.0 GHz and those of CH3CH2PD2 11BH3 and CH3CH2PD2 11BD3 in the range 26.5–39.0 GHz. a-type transitions were observed and R-branch assignments have been made for all isotopes in the ground vibrational state. From the relative intensities of the microwave transitions, the Stark effect, and the experimental rotational constants, it has been determined that the assigned spectra result from the trans conformer which is believed to be more stable than the gauche form at ambient temperature. The dipole moment components for trans-ethylphosphine–borane were determined from the Stark effect to be ‖μa‖ = 4.66±0.01, ‖μb‖ = 1.34±0.03, and ‖μt‖ = 4.85±0.02 D. With reasonable assumptions for the ethyl moiety, the following structural parameters for trans-ethylphosphine–borane were calculated: r(B–P) = 1.914±0.018 Å, r(B–H) = 1.205±0.013 Å, r(P–H) = 1.408±0.016 Å, r(P–C) = 1.823±0.016 Å, ∢BPC = 115.0°±1.1°, ∢PBH = 106.1°±3.4°, ∢CPH = 103.4°±3.7°, and ∢PCC = 115.1°±2.5°. These results are compared to similar quantities in some analogous molecules.
Infrared Spectrum of the Novel Electron-Deficient BH<sub>4</sub> Radical in Solid Neon
作者:Lester Andrews、Xuefeng Wang
DOI:10.1021/ja026572w
日期:2002.6.1
Laser-ablated boron reacts with hydrogen on condensation in excess neon to give BH4 radical, BH4- anion, and B2H6 as the major products. Identifications are based on 10B and D substitution, DFT frequency calculations, and comparison to previous spectra. Infrared spectra of BH4 support the C2v structure deduced from previous ESR spectra and theoretical calculations with two normal B-H bonds and two long B-H bonds for this novel electron-deficient radical. NBO analysis suggests that the two long B-H bonds and the H- -H bond are one-electron bonds.