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Theoretical Studies of Simple Organoboron Compounds: Structures and Stabilities of BC 2 H 4 Isomers
Author(s) -
Largo Antonio,
Barrientos Carmen
Publication year - 1996
Publication title -
applied organometallic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.53
H-Index - 71
eISSN - 1099-0739
pISSN - 0268-2605
DOI - 10.1002/(sici)1099-0739(199604)10:3/4<283::aid-aoc458>3.0.co;2-3
Subject(s) - chemistry , ethylene , boron , ab initio , molecular geometry , computational chemistry , ab initio quantum chemistry methods , moiety , ground state , bond length , crystallography , molecule , stereochemistry , crystal structure , organic chemistry , atomic physics , catalysis , physics
An ab initio study of the BC 2 H 4 has been carried out. Several isomers have been studied: boron–ethylene complexes resulting from perpendicular and σ interactions, boron–methylcarbene type structures, open and cyclic insertion products with a B–H bond, and isomers with two B–H bonds. Geometries at the second‐order Møller–Plesset level have been obtained for ten species, and their characteristics have been tested through computation of vibrational frequencies. Special attention has been paid to their molecular structure, trying to rationalize the bonding in these species, particularly in the case of cyclic isomers. Electronic energies have been computed at the fourth‐order Møller–Plesset level. Our theoretical calculations predict that the global minimum is the H 2 BCCH 2 isomer ( 2 B 2 electronic state), with the HBH plane perpendicular to the CCH 2 moiety, and that it lies about 66 kcal mol −1 (276 kJ mol −1 ) below ground‐state boron+ethylene. Nevertheless there are other isomers which are also quite stable and might be accessible to experimental detection, such as HBCHCH 2 and H 2 BCHCH (both with 2 A′ electronic states) which lie 8 (33.5) and 13 kcal mol −1 (54.4 kJ mol −1 ), respectively, above the global minimum, as well as two cyclic structures, the insertion product HBC 2 H 3 ( 2 A″) and the boron–ethylene π‐complex BC 2 H 4 ( 2 A 1 ), which are relatively stable since they lie 12 (50) and 22 kcal mol −1 (92 kJ mol −1 ), respectively, higher than H 2 BCCH 2 .