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Structural and energetic properties of alkylfluoride–BF 3 complexes in the gas phase and condensed‐phase media: computations and matrix infrared spectroscopy
Author(s) -
Knauf Robin R.,
Helminiak Heather M.,
Wrass John P.,
Gallert Timothy M.,
Phillips James A.
Publication year - 2012
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.1944
Subject(s) - chemistry , neon , gas phase , phase (matter) , infrared spectroscopy , flattening , density functional theory , infrared , matrix isolation , computational chemistry , crystallography , molecular physics , argon , physics , organic chemistry , astronomy , optics
We have undertaken an experimental and computational study of the structural properties of a few alkylfluoride–BF 3 complexes (RF′–BF 3 ), which are proposed intermediates in a certain class of Friedel–Crafts reactions. Using density functional theory and second‐order Møller–Plesset calculations, we have obtained gas‐phase structures, frequencies, and B–F′ bond potentials for CH 3 F–BF 3 , (CH 3 ) 2 CHF–BF 3 , and (CH 3 ) 3 CF–BF 3 . All the complexes are weakly‐bonded in the gas phase, with B–F′ distances (X3LYP/aug‐cc‐pVTZ) of about 2.4 Å and binding energies (MP2/aug‐cc‐pVTZ) ranging from 5.4 and 6.7 kcal/mol. Accordingly, gas‐phase bond potentials are relatively shallow and flat for these complexes. However, even though the inner walls of the potentials are rather soft (the energies rise by only about 5 to 10 kcal/mol between 2.4 and 1.6 Å), we observe no global or local minima at short B–F′ distances. For the (CH 3 ) 2 CHF–BF 3 and (CH 3 ) 3 CF–BF 3 potentials in dielectric media, we do observe a distinct flattening along the inner wall, which results in shelf‐like region near 1.7 Å, but this feature is not a true local minimum. We have also obtained low‐temperature infrared spectra of the (CH 3 ) 2 CHF–BF 3 complex in solid neon, and the frequencies agree quite favorably with those obtained via computations, which validates the computational assessment of the gas‐phase complexes. Copyright © 2011 John Wiley & Sons, Ltd.