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Boron trifluoride activated enaminocarbonyl compounds: the influence of intermolecular interactions on the ab initio determination of structures and vibrational spectra
Author(s) -
Nikolai Joachim,
Maas Gerhard,
Taubmann Gerhard
Publication year - 2005
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.839
Subject(s) - chemistry , intermolecular force , ab initio , hydrogen bond , crystallography , bond length , ab initio quantum chemistry methods , raman spectroscopy , molecule , boron trifluoride , computational chemistry , density functional theory , crystal structure , organic chemistry , physics , optics , catalysis
The structures of the BF 3 –enaminoaldehyde adducts 3a , b have been determined by quantum‐chemical calculations employing Hartree‐Fock, Møller‐Plesset and density functional methods. The length of the coordinative BO bond ranges between 1.59 and 1.62 Å. The BSSE‐free energy of the BO bond ranges between −14.7 and −16.9 kcal/mol. Taking into account hydrogen bonds and dispersion forces between two molecules of 3a , b in the dimeric structure 4 reduces the BO bond length significantly (BO: 1.52–1.57 Å) thereby reproducing the BO bond length found in the x‐ray structure of 1 (BO: 1.49 Å) with much better accuracy. Using the calculated IR and Raman spectra of the dimers 4 as reference, the BO band in the experimental spectra can be assigned. Our approach seems to be of value in discussions comparing structural features gained from gas phase ab initio calculations and solid state x‐ray structures involving strong dipolar structures which allow for various intermolecular interactions. Copyright © 2004 John Wiley & Sons, Ltd.