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Internal conrotation and disrotation in H 2 BCH 2 BH 2 and diborylmethane 1,3 H exchange
Author(s) -
Minyaev Ruslan M.,
Quapp Wolfgang,
Subramanian Govindan,
Schleyer Paul von R.,
Mo Yirong
Publication year - 1997
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/(sici)1096-987x(19971115)18:14<1792::aid-jcc8>3.0.co;2-f
Subject(s) - chemistry
The paths of correlated internal disrotation (barrier less than 0.4 kcal/mol) and conrotation (barrier around 1.9 kcal/mol) of the two BH 2 groups in H 2 BCH 2 BH 2 have been computed employing ab initio [MP2(full)/6–31G**] and density functional theory (Becke3LYP/6–311+G**) methods. Two B(SINGLE BOND)C(DOTTED BOND)B( p ) hyperconjugative interactions stabilize the C s symmetric H 2 BCH 2 BH 2 isomer ( 1 ). The B(SINGLE BOND)C(DOTTED BOND)B( p ) hyperconjugative stabilization, evaluated by homodesmotic reactions and using the orbital deletion procedure (which “deactivates” the “vacant” born p orbital), is less than 6 kcal/mol in diborylmethane. The B(SINGLE BOND)C(DOTTED BOND)B( p ) stabilization is shown to be remarkably large in C 4 B 6 H 10 ( Td ). At MP2(fu)/6–31G**, disproportionation into 1 and methane is only 5.6 kcal/mol exothermic. The 1,3 H exchange in diborylmethane is an asynchronous process and proceeds via a doubly bridged cyclic intermediate with 9.3 kcal/mol barrier. Structures with “planar tetracoordinate” carbon are stabilized considerably by BH 2 substituents, but they are still high in energy. © 1997 John Wiley & Sons, Inc. J Comput Chem 18 : 1792–1803, 1997