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2Â¥2009-06-30 14:38:55
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xi2004

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navypang(½ð±Ò+10,VIP+0):лл£¬xi2004£¬¸ÐлÄã¶à´ÎµÄ°ïÖú 6-30 15:03
paopaomeng(½ð±Ò+1,VIP+0):лл½»Á÷ 7-1 11:33
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Originally posted by navypang at 2009-6-30 14:38:
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xixi, À´×¬µãÇ®

Titre du document / Document title
Intramolecular C-H...Ccarbene hydrogen bonds and competing interactions in monoprotonated tripodal carbenes
Auteur(s) / Author(s)
HOWARD Sian T. ; ABERNETHY Colin D. ;
R¨¦sum¨¦ / Abstract
The anionic tripodal N-heterocyclic carbene (C3N2H3)3BH- first prepared by Fehlhammer, together with three neutral variants, (C3N2H3)3CH, (C3N2H3)3P, and (C3N2H3)3SiH, have been studied using quantum chemical methods. Isodesmic reactions are used to deduce that the phosphine-bridgehead species in particular has a large-resonance stabilization energy. All the podands undergo substantial conformational change on excitation to the lowest triplet electronic state, with effective localization of the excitation on one of the heterocyclic rings, dearomatizing it. On monoprotonation of the ground states, three of these species display intramolecular C-H...Ccarbene hydrogen bonding: The nature and strength of these interactions is explored using model (intermolecularly hydrogen-bonded) complexes, isodesmic reactions, and GIAO calculations of chemical shifts. One surprising result is that C-H...Ccarbenehydrogen bonds involving ethenic hydrogens can be almost as strong as those involving the imidazolium proton (first identified by Arduengo). The case of the monoprotonated carbon bridgehead species is in particular intriguing. It is stabilized by a competitive CcarbeneC...N interaction of sufficient strength to override the C-H...Ccarbenebonding motif observed in the other structures.
Revue / Journal Title
Journal of computational chemistry   ISSN 0192-8651   CODEN JCCHDD  
Source / Source
2004, vol. 25, no5, pp. 649-659 [11 page(s) (article)]
Langue / Language
Anglais

Editeur / Publisher
Wiley, New York, ETATS-UNIS  (1980) (Revue)

Localisation / Location
INIST-CNRS, Cote INIST : 18378, 35400011358406.0050
xi2004-emuch@163.com
3Â¥2009-06-30 14:55:16
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xi2004

ÖÁ×ðľ³æ (Ö°Òµ×÷¼Ò)

[quote]Originally posted by xi2004 at 2009-6-30 14:55:

xixi, À´×¬µãÇ®


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xi2004-emuch@163.com
4Â¥2009-06-30 14:56:41
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