Ab initio electronic structure calculations of the C2H5B potential energy surface: The stability of borirane

Taylor, C. A.; Zerner, Michael C.; Ramsey, Brian G.

doi:10.1016/s0022-328x(00)99339-2

Cited by 26 publications

(32 citation statements)

References 18 publications

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“…Khafizova et al reported that the cycloboration of terminal olefins using BCl 3 •SMe 2 , BF 3 •THF in the presence of magnesium, and Cp 2 TiCl 2 catalyst gives 1-halo-2-alkyl-boriranes as adducts with the Lewis base as synthetic intermediates. 34 Most remarkably, catalyzed cycloboration of terminal olefins with dichlorophenylborane yields 1-phenyl-2-alkyl-boriranes that could be isolated in substance and characterized by NMR techniques according to Khafizova et al 35 Early 36,37 theoretical investigations have established that among C 2 H 5 B isomers vinylborane is more stable than borirane, 38,39 computational analyses. 40 Ring opening of borirane to 2borapropane-1,3-diyl was identified to be endergonic, in contrast to the strongly exothermic formation of the allyl cation from cyclopropyl cation.…”

Section: ■ Introductionmentioning

confidence: 99%

Computational Study of the Isomerization Reactions of Borirane

Krasowska

Bettinger

2018

J. Org. Chem.

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Borirane is isoelectronic to the cyclopropyl cation, but is stable toward electrocyclic ring opening to 2-bora-propa-1,3-diyl A, the boron analogue of the allyl cation. A computational investigation using density functional theory (B3LYP) in combination with highly correlated electronic structure theory methods of the coupled-cluster [CCSD(T)] and multireference configuration interaction (MRCI) type in conjunction with basis sets of up to quadruple-ζ quality reveal that formation of A is endothermic by roughly 15 kcal mol–1 and that A collapses almost without barrier (0.2 kcal mol–1) to borirane. The vinylborane isomer B is more stable than borirane and its formation is associated with a barrier of 36–38 kcal mol–1. Methyl methylideneborane E, only slightly less stable than B, can only be accessed by pathways involving barriers of at least 60 kcal mol–1.

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Section: ■ Introductionmentioning

confidence: 99%

Computational Study of the Isomerization Reactions of Borirane

Krasowska

Bettinger

2018

J. Org. Chem.

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“…[9] Systematic theoretical investigations on BC 2 H 2 , BC 2 H 4 , and BC 2 H 5 species, including vinylborane, have been also reported by different groups. [10][11][12][13][14][15] However, the information on anionic species is very scarce. The properties of [H 2 BC=CH 2 ] À and the rearrangements of [BH 2 CC] À have been described in two different theoretical papers.…”

Section: Introductionmentioning

confidence: 99%

Strong Dissimilarities Between the Gas‐Phase Acidities of Saturated and α,β‐Unsaturated Boranes and the Corresponding Alanes and Gallanes

Gámez

Guillemin

Mó

et al. 2008

Chemistry A European J

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The effect that unsaturation has on the intrinsic acidity of boranes, alanes, and gallanes, was analyzed by B3 LYP and CCSD(T)/6-311+G(3df,2p) calculations on methyl-, ethyl-, vinyl-, and ethynylboranes, -alanes and -gallanes, and on the corresponding hydrides XH3. Quite unexpectedly, methylborane, which behaves as a carbon acid, is predicted to have an intrinsic acidity almost 200 kJ mol(-1) stronger than BH3, reflecting the large reinforcement of the C--B bond, which upon deprotonation becomes a double bond through the donation of the lone pair created on the carbon atom into the empty p orbital of the boron. Also unexpectedly, and for the same reason, the saturated and alpha,beta-unsaturated boranes are much stronger acids than the corresponding hydrocarbons, in spite of being carbon acids as well. The Al derivatives also behave as carbon acids, but in this case the most favorable deprotonation process occurs at C beta, leading to the formation of rather stable three-membered rings, again through the donation of the C beta lone pair into the empty p orbital of Al. For Ga-containing compounds the deprotonation of the GaH2 group is the most favorable process. Therefore only Ga derivatives behave similarly to the analogues of Groups 14, 15, and 16 of the periodic table, and the saturated derivatives exhibit a weaker acidity than the unsaturated ones. Within Group 13, boranes are stronger acids than alanes and gallanes. For ethyl and vinyl derivatives, alanes are stronger acids than gallanes. We have shown, for the first time, that acidity enhancement for primary heterocompounds is not only dictated by the position of the heteroatom in the periodic table and the nature of the substituent, but also by the bonding rearrangements triggered by the deprotonation of the neutral acid.

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“…Boracyclopropanes are boron analogs of the cyclopropylcation, which is well known not to be a minimum on the potential energy surface of a C 3 H þ 5 ion. And although both semiempirical and ab initio calculations [13] do indicate that a boracyclopropane is an energy minimum, it may be overly optimistic to assume that they would survive in refluxing benzene.…”

Section: Introductionmentioning

confidence: 99%