A theoretical investigation of HCNBF3 and HCNBCl3 was undertaken with the aim of understanding the coordination effect of nitriles as the ligand in the CN bond stretching fundamental vibrations. The evaluated CN bond potential parameters given by the MNDO method suggest that the quadratic and cubic force constants are responsible for the characteristic high wavenumber shift of the CN stretching fundamentals and the apparent increase in the harmonic CN stretching force constant derived from the normal coordinate calculations. © 1987.151C223226Coever, Curran, Infrared Absorption by the C'N Bond in Addition Compounds of Nitriles with Some Inorganic Halides1 (1958) Journal of the American Chemical Society, 80, p. 3522Brown, Kubota, (1961) J. Am. Chem. Soc., 83, p. 4175Beattie, Gilson, 430. A normal co-ordinate analysis of MeCN, BX3, and its relevance to the thermodynamic stability of co-ordination compounds (1964) Journal of the Chemical Society (Resumed), p. 2292Walton, (1965) Q. Rev., 19, p. 126Purcell, Drago, (1966) J. Am. Chem. Soc., 88, p. 919Kawai, Kanesaka, (1969) Spectrochim. Acta, 25, p. 1265. , Part AKanesaka, Hase, Kawai, The Infrared Spectra of Addition Compounds of Hydrogen and Deuterium Cyanides with Boron Tribromide (1972) Bulletin of the Chemical Society of Japan, 45, p. 1595Dewar, Thiel, (1977) J. Am. Chem. Soc., 99, p. 4899Dewar, McKee, Rzepa, (1978) J. Am. Chem. Soc., 100, p. 3607Dewar, Rzepa, Ground states of molecules. 53.MNDO calculations for molecules containing chlorine (1983) Journal of Computational Chemistry, 4, p. 158Thiel, (1978) Quantum Chemistry Program Exchange, , Indiana University, Bloomington, IN, Program No. 353Wiberg, (1968) Tetrahedron, 24, p. 1083Suzuki, Pariseau, Overend, (1966) J. Chem. Phys., 44, p. 3561Nakagawa, Morino, Anharmonic Potential Constants and Vibrational and Rotational Parameters for Hydrogen Cyanide (1969) Bulletin of the Chemical Society of Japan, 42, p. 2212Strey, Mills, The anharmonic force field and equilibrium structure of HCN and HCP (1973) Molecular Physics, 26, p. 129Steele, Person, Brown, (1981) J. Phys. Chem., 85, p. 2007Allinger, Yuh, (1978) Quantum Chemistry Program Exchange, , Indiana University, Bloomington, IN, Program No. 395