van der Waals Complexes between Carbonyl Fluoride and Boron Trifluoride Observed in Liquefied Argon, Krypton, and Nitrogen:  A FTIR and ab Initio Study

The IR spectra (4000-400 cm-1) of COF2/BF3 mixtures, dissolved in liquefied argon (LAr), krypton (LKr), and nitrogen (LN2), have been examined. In all spectra evidence was found for the formation of a 1:1 van der Waals complex. Using spectra recorded at several temperatures between 81 and 172 K the...

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Bibliographic Details
Published in:Journal of the American Chemical Society 1998-07, Vol.120 (29), p.7310-7319
Main Authors: Stolov, A. A, Herrebout, W. A, van der Veken, B. J
Format: Article
Language:English
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Summary:The IR spectra (4000-400 cm-1) of COF2/BF3 mixtures, dissolved in liquefied argon (LAr), krypton (LKr), and nitrogen (LN2), have been examined. In all spectra evidence was found for the formation of a 1:1 van der Waals complex. Using spectra recorded at several temperatures between 81 and 172 K the complexation enthalpies ΔH° in LAr, LKr, and LN2 were determined to be −11.8(3), −10.6(3), and −7.8(3) kJ mol-1, respectively. A theoretical study, using both density functional theory at the B3LYP/6-311++G(d,p) level and ab initio at the MP2/aug-cc-pVTZ level, indicates that the complexation can occur either via the oxygen or via a fluorine atom of COF2. From a comparison of the experimental and calculated frequencies it was concluded that the observed complex bands are due to a species in which the boron atom coordinates with the oxygen lone pairs. The complexation energy Δc E is obtained from the ΔH° by correcting for solvent influences, and thermal contributions equals −15.0(6) kJ mol-1. This value agrees well with the MP2/aug-cc-pVTZ level result, −12.4 kJ mol-1. The complexation entropy ΔS° has been found to be influenced by the solvent and is correlated with ΔH°. This correlation reflects the existence of the compensation effect for the thermodynamics of van der Waals complexes.
ISSN:0002-7863
1520-5126
DOI:10.1021/ja980874+