Infrared spectra of B(OMe)3, ClB(OMe)2 and Cl2BOMe species, isolated CH streching frequencies and bond strengths

Article abstract of DOI:10.1016/0584-8539(89)80036-4

Infrared spectra in the gas phase are reported over the range 3100-500 cm^-1 for species of B(OMe)3, ClB(OMe)2 and Cl2BOMe, with CH3, CD3 and CHD2 substitution.A detailed analysis of νCH and νCD data in all three species of Cl2BOMe yields strong evidence for the presence of three kinds of CH bond, two of them weak and one of them strong.The methyl group is then twisted, probably through 10-20 deg, out of the eclipsed or staggered conformation.The CHD2 spectra of the di and trimethoxy compounds are less susceptible to analysis, but suggest also the presence of two weak and strong bonds, the former increasing in weakness as the number of methoxy groups increases.This is as expected from the increased competition likely between the lone pair electrons for the empty boron orbital.The spectra of the CD3 species permit a clear assignment of νBO, δ_sCH3, δ_sCD3 and δ_asCD3 modes.In Cl(COCH3)2, ν_sBO lies at 1278 cm^-1.