The vibrational spectra of the boron halides and their molecular complexes. Part 12: The complexes of boron trifluoride with methyl fluoride and methyl chloride. An ab initio study

The properties of the molecular complexes formed between boron trifluoride and the methyl halides, CH3F and CH3Cl, have been computed by means of a series of ab initio calculations, at the second order level of Møller-Plesset perturbation theory, using a triple-zeta Gaussian basis set with polarization and diffuse functions on all atoms. We have determined the structures and interaction energies of these two adducts, and compared the results with earlier calculations on analogous complexes of boron trifluoride with water, hydrogen sulphide, ammonia and phosphine and their partially- and fully-methylated derivatives, and with hydrogen fluoride and hydrogen chloride. The results show a strong correlation with the basic properties of the partner molecules. The vibrational spectra of the complexes have also been determined, and similar correlations have been found between the perturbations of the BF3 spectra in the complexes and the inter-monomer stretching force constants, and the interaction energies.