Microwave spectra and structure of hydrogen cyanide-boron trifluoride: an almost weakly bound complex

Abstract

Rotational spectra of the complex HCN-BF3 have been observed using pulsed-nozzle Fourier transform microwave spectroscopy. Spectra have been observed for the l l B and loB species with both HC14N and HCISN, and the hyperfine structure has been analyzed. The complex has the expected C3" structure, with the nitrogen end of the H C N toward the boron, but the observed BN bond length of 2.473(29) A is notably shorter than that in the related weakly bound systems NGN-BF~ and NGC-CEN-BF~.The out-of-plane distortion of the BF3 cannot be determined accurately but is probably less than 3 O . We compare the structure, force constants, quadrupole coupling constants, and binding energy of the complex with those of other species formed from BF3 and a variety of nitrogen donors. Despite the rather short B-N bond length, the force constant for the intermolecular bond, as well as the boron and nitrogen nuclear quadrupole coupling constants, is comparable to those of a truly weakly bound system.

Effective utilization of noncovalent interaction descriptor in BX3–Lewis base complexes: A determination of adduct/van der Waals complexes and reassessment of the BX3 acid strength order

“…The calculated distances are reasonable and in agreement with reported data [28][29][30][31][32][33][34][35][36][37][38][39].…”

Structure Correlation and Chemistry

“…The relationships used in this and the preceding sections to compare molecular structures in different environments and to connect static crystal structures with the dynamics of chemical reactions have been judged`quite archaic by modern standards', i.e. in comparison to the sophisticated results obtainable from quantum chemistry (Reeve et al, 1993). We agree, the picture is oversimpli®ed.…”

Structures of the van der Waals Isomers of Halosulfuric Acids: Microwave Spectra of HX–SO3(X= F, Cl, Br)

“…Thus, it appears that the intermolecular B-F bond in HF-BF 3 is much like a dative bond in its earliest stages of development. This situation is reminiscent of other systems that we have investigated involving both BF 3 (10,11) and the closely related Lewis acid SO 3 (12,13). For this reason, we have become interested in the hydrogen halide complexes of SO 3 as well and in this paper we report a microwave investigation of HX-SO 3 (X ϭ F, Cl, Br).…”