Molecular-beam mass-spectrometric investigation of ammonia borane and aminoborane vapors

Kuznesof, Paul M.; Shriver, Duward F.; Stafford, Fred E.

doi:10.1021/ja01012a020

Cited by 30 publications

(18 citation statements)

References 1 publication

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“…As pointed out earlier, the nitrogen lone pair can hyperconjugate with the nearby antibonding orbital p Ã BH 2 and stabilizes the staggered structure by 7.4±8.8 kcal/mol. However, the repulsion between the lone pair on the nitrogen atom and the two (1) a The number of imaginary frequencies is included in the parentheses 1 The HF/6-31G* energies for the plane and the staggered N 2 H 4 are A111.116482 a.u. and A111.151778 a.u., respectively.…”

Section: Aminoboranementioning

confidence: 99%

“…Among the aliphatic boron-nitrogen compounds, aminoborane (H 2 BNH 2 ), formed in the thermal decomposition of H 3 BNH 3 [1], has received extensive theoretical [2±23] and experimental [24±28] attention due to its importance as a building block for complex aminoboranes. All studies have con®rmed the planarity of H 2 BNH 2 and the existence of a BN partial double bond.…”

Section: Introductionmentioning

confidence: 99%

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Theoretical analysis of the internal rotation in aminoborane and borylphosphine

Peyerimhoff

1999

Theoretical Chemistry Accounts: Theory, Computation, and Modeli

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Using a recently proposed orbital deletion procedure and the block-localized wavefunction method, the rotational barriers in H 2 BNH 2 and H 2 BPH 2 are analyzed in terms of conjugation, hyperconjugation, steric eect and pyramidalization. With the zero-point energy corrections, the p-binding strengths in the planar H 2 BNH 2 and H 2 BPH 2 are both around 20 kcal/mol at the HF level using the 6-311+G** basis set. With the deactivation of the p atomic orbitals on the boron atom and the evolution from a planar structure to a 90°-twisted structure, the steric repulsion between the BeH bonds and the NeH or PeH bonds is relieved and moreover, the negative hyperconjugation from the lone electron pair or pairs on the nitrogen or phosphorus atoms to the antibonding orbital v* BH 2 of the BH 2 group stabilizes the twisted structure by 7.4(8.8) or 4.0(5.0) kcal/mol at the HF/6-31G*(6-311+G**) level. However, the repulsive interaction between the lone pair(s) and the two BH r bonds is so prominent that the overall steric eect contributes 20.3(22.9) and 19.3(19.8) kcal/ mol to the rotational barriers in H 2 BNH 2 and H 2 BPH 2 with the 6-31G*(6-311+G**) basis set. The present techniques and analyses may also give some clues to justify the parameterization in the empirical molecular mechanics methods.

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Section: Aminoboranementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Theoretical analysis of the internal rotation in aminoborane and borylphosphine

Peyerimhoff

1999

Theoretical Chemistry Accounts: Theory, Computation, and Modeli

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“…As the specimens were heated to temperatures over 150°C, new borazine species were detected at 200°C presumably because of thermal decomposition of poly(aminoborane) chains. The formation of borazine could be explained by hydrogen elimination that is expected to take place at such temperature [20]. The profile for the overall volatiles corresponded exactly to the sum of the two profiles in (a) and (b).…”

mentioning

confidence: 63%

Synthesis and characterization of poly(aminoborane) as a new boron nitride precursor

Kim

Moon

Kho

et al. 1999

Polym. Adv. Technol.

101

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During the solution reaction of NaBH4/(NH4)2SO4 in tetraglyme to form borazine, polymeric aminoborane (NH2BH2)x has been isolated as a white powder. The powder was characterized by thermal gravimetric analysis/differential scanning calorimetry, infrared and mass spectroscopies, and powder X‐ray diffraction. Solid‐state 15N and 11B nuclear magnetic resonance firmly proved that the chain‐like poly(aminoborane) evolved a partially condensed B3N3 ring structure by dehydrogenative condensation between chains at 200 °C. Pyrolysis of the polymer in a nitrogen stream up to 1400 °C led to a 75% yield of hexagonal boron nitride with an interlayer spacing of 3.37 Å. Copyright © 1999 John Wiley & Sons, Ltd.

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“…Besides being detected as product during the pyrolysis of solid AB, it was also found during the low-pressure pyrolysis of gaseous AB [46,77], during the gas-phase reaction between diborane and ammonia [78], and during the electric discharge in a borazine-containing gaseous atmosphere [79]. Besides being detected as product during the pyrolysis of solid AB, it was also found during the low-pressure pyrolysis of gaseous AB [46,77], during the gas-phase reaction between diborane and ammonia [78], and during the electric discharge in a borazine-containing gaseous atmosphere [79].…”

Section: Pyrolysismentioning

confidence: 99%

“…It is not completely clear though, whether or not in these cases BH 3 NH 3 exists in the gas phase in molecular form or in the form of its constituents (di)borane and ammonia. In spectroscopic measurements AB was detected in the gas phase but the amount of diborane exceeded the amount of AB significantly, which was explained by the instability of the AB molecule with respect to wall collisions [46]. The special meaning of DADB for the AB decomposition and generation will be discussed in later sections.…”

mentioning

confidence: 94%

Ammonia Borane and Related Compounds as Hydrogen Source Materials

Mertens

Wolf

Baitalow

2010

Handbook of Hydrogen Storage

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Mainly driven by the efforts of the automotive industry, a strong push towards new concepts to store hydrogen has occurred over recent years. Generally, in this framework, high hydrogen content materials have been of great interest for chemical storage concepts.From weight considerations, the most natural choice to develop hydrogen storage and source materials would be the use of first row element hydrides. Since a high valency allows more hydrogen to bond per atom, the mid-first row hydrides borane, methane, and ammonia with 21, 25, and 17.5 wt% are amongst the materials with the highest hydrogen contents. Although the thermodynamics is not favorable, due to the strong bond between carbon and hydrogen, the utilization of methane as a hydrogen source material has been widely investigated and small natural gas reformers for a fueling station to supply polymer electrolyte membrane (PEM) fuel cell vehicles with hydrogen have been developed [1].However, ammonia and boranes alone are also not very attractive as hydrogen source compounds because of thermodynamic considerations and the harm they potentially bring to fuel cell catalysts (PEM). The interesting fact that nitrogen and boron are on opposite sides of the electronegative-electropositive border line that runs through the periodic table, offers attractive new features to the ammonia borane adduct BH 3 NH 3 (AB). Especially, their ability to release hydrogen at low temperatures, combined with the very high hydrogen content, has brought these materials into the focus of recent research efforts.Besides the fact that the known world boron resources are insufficient to permanently fuel a significant portion of the world vehicle fleet, it is very clear from the energy expense needed for AB regeneration and the cost aspects that ammonia borane-based materials are not likely to become a means of mass hydrogen storage. These materials, however, can be of interest for small scale applications demanding very high hydrogen storage density, such as autonomously operated small electrical Handbook of Hydrogen Storage. Edited by Michael Hirscher j215 devices. Research efforts to put AB materials to use primarily encompass the control of the hydrogen release kinetics, the production of AB materials and the rehydrogenation of the spent materials.Since spent ammonia borane, or borazane as it is also called, and most of its derivatives are not easily rechargeable, for thermodynamic reasons, new recycling strategies need to be developed. An essential part of possible recycling schemes is the generation of hydridic, that is, negatively charged, hydrogen located at the boron centers. Because of the importance of borohydrides in organic synthesis and the recent developments in nonmetal-center-based hydrogen activation [2], the relevance of these research efforts is outside the area of hydrogen source and storage materials. Materials Description and Characterization

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Molecular-beam mass-spectrometric investigation of ammonia borane and aminoborane vapors

Cited by 30 publications

References 1 publication

Theoretical analysis of the internal rotation in aminoborane and borylphosphine

Theoretical analysis of the internal rotation in aminoborane and borylphosphine

Synthesis and characterization of poly(aminoborane) as a new boron nitride precursor

Ammonia Borane and Related Compounds as Hydrogen Source Materials

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