Cyclic 2-Aminoethylborane (1,2-Azaboretidine), a Product from the Reaction between Aziridine and Sodium Borohydride.

Åkerfeldt, Stig; M, Hellström; Niinikoski, J.; Kulonen, E.; Brunvoll, J.; Bunnenberg, E.; Djerassi, Carl; Records, Ruth

doi:10.3891/acta.chem.scand.20-1418

Cited by 9 publications

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“…The dative N-B bond is calculated to be as short as 161.5 pm, approximately 5 pm shorter than the corresponding bond lengths in H 3 N-BH 3 7 and (CH 3 ) 3 N-BH 3 . 10 This difference is perhaps caused by a different hybridization of the nitrogen atom in aziridine-borane (sp 2 ) than what is the case in H 3 N-BH 3 and (CH 3 ) 3 N-BH 3 (sp 3 ). The dipole moment of 17.72(11) × 10 -30 C m in the gaseous state is significantly larger than the dipole moment measured in a benzene solution 3 (14.8(3) × 10 -30 C m).…”

Section: Discussionmentioning

confidence: 99%

“…In 1956, Burg and Good isolated a substance with a melting point of 40 °C from the reaction between diborane and aziridine, which they assumed to be the donor−acceptor complex between the Lewis base aziridine (C 2 H 5 N) and the Lewis acid BH 3 . Ten years later, Åkerfeldt and Hellström synthesized the C 2 H 5 N−BH 3 complex from sodium borohydride and aziridine. A modified synthetic procedure was later reported by Åkerfeldt et al, who also determined the dipole moment of this complex to be as large as 14.8(3) × 10 −30 C m [4.45(1) debye] in benzene.…”

Section: Introductionmentioning

confidence: 99%

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Microwave Spectrum, Structure, Barrier to Internal Rotation, and Dipole Moment of the Aziridine−Borane Complex (C₂H₅N−BH₃)

2009

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The microwave spectrum of the aziridine-borane complex (C(2)H(5)N-BH(3)) has been investigated by microwave spectroscopy in the 18-80 GHz spectral region. The spectra of the ground vibrational state and three vibrationally excited states have been assigned, and the vibrational frequencies of these states have been determined. The complex was found to have a symmetry plane (C(s) symmetry) formed by the N-B bond and the bisector of the aziridine ring. The dative N-B bond is found to be as short as 161.5 pm in MP2/aug-cc-pVTZ calculations. The MP2 structure of the aziridine ring of this complex is nearly the same as that in the substitution structure of aziridine. Complex formation therefore appears to have little influence on this moiety. The dipole moment was determined to be mu(a) = 17.72(11), mu(b) = 0.0 (by symmetry), mu(c) = 5.70(8), and mu(tot) = 18.62(11) x 10(-30) C m [5.581(34) D]. The barrier to internal rotation of the borane group was determined to be 12.1(3) kJ/mol using the microwave splitting method. The microwave investigation has been augmented by high-level quantum chemical calculations at the MP2/aug-cc-pVTZ and B3LYP/6-311++G** levels of theory. There is generally good agreement between the experimental results and quantum chemical predictions.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Microwave Spectrum, Structure, Barrier to Internal Rotation, and Dipole Moment of the Aziridine−Borane Complex (C₂H₅N−BH₃)

2009

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“…However, only nitrogen is capable of significantly modulating sp 2 – sp 3 rehybridization in this system, as suggested by conformational analysis. Indeed, experimental evidence for the ring closure in N has shown that such interaction is effective with the amino substituent [33] . In turn, phosphane derivatives react with organoboranes via 1,1‐organoboration to give ( Z )‐alkenes, thus indicating the ability of phosphorus to interact with boron [34] .…”

Section: Resultsmentioning

confidence: 99%

“…Indeed, experimental evidence for the ring closure in N has shown that such interaction is effective with the amino substituent. [33] In turn, phosphane derivatives react with organoboranes via 1,1organoboration to give (Z)-alkenes, thus indicating the ability of phosphorus to interact with boron. [34] However, considering the high energy associated with ring strain during formation of a four-membered ring, [35] a suitable rehybridization strategy could involve distancing of the interacting groups by elongating the carbon chain.…”

Section: Resultsmentioning

confidence: 99%

Conformational and Substituent Effects on The Rehybridization of Boron in β‐Substituted Ethylboranes

Martins

Freitas

2021

Asian J Org Chem

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The chemistry of boron-containing molecules pervades the study of biomolecules, new materials, organic synthesis, and beyond. In addition, the stereochemistry and rehybridization capability of boron in molecules influence the reactivity and selectivity of reactions. Therefore, conformational analysis and the study of substituent effects on the modulation of the sp 2 -sp 3 character of boron in β-substituted ethylboranes may be valuable for the rational design of compounds in which the empty p B orbital plays a central role in the reaction intermediate. Accordingly, we have quantumchemically studied the orbital interactions and bonding properties that govern the conformational behavior and boron hybridization in β-substituted ethylboranes (substituents, X = H, CH 3 , F, Cl, NH 2 , PH 2 , OH, and SH). Conformations with an anti arrangement along the BÀ CÀ CÀ X path are generally preferred over syn and/or gauche conformations, while a BÀ H bond tends to eclipse with the CÀ C bond rather than with a less sterically hindered CÀ H bond. However, the s character of boron relative to the CÀ B bond strongly decreases in the syn conformation, where X can participate as an electron donor to the empty p B orbital. Indeed, such interaction makes the syn conformation of 2-aminoethylborane the single stable conformer in the gas phase.

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“…[3][4][5][6][7] Although closelyrelated linear analogues, such as ammonia borane (NH3BH3) [8][9][10][11][12][13][14][15][16] and alkyl amine boranes, [17][18][19][20][21][22][23][24][25][26][27][28] are well characterised, very few CABs have been studied both in terms of their structure and chemical properties. The first CAB to be synthesised was the three-membered aziridine borane; [29][30][31] the crystal structure was determined subsequently, 32 and the complex was later characterised by NMR and IR techniques 33 as well as low-level ab initio and semi-empirical methods. 34 Microwave spectroscopy (MWS) was later employed to study the barrier to internal rotation and gas-phase structure.…”

Section: Introductionmentioning

confidence: 99%

Structural and thermochemical studies of pyrrolidine borane and piperidine borane by gas electron diffraction and quantum chemical calculations

et al. 2020

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The gaseous structures, thermochemical properties and dehydrogenation reaction energy profiles of the borane complexes of pyrrolidine and piperidine have been investigated using gas electron diffraction (GED) and state-of-the-art computational methods. These complexes are of interest because of their potential as hydrogen storage materials for future onboard transport applications. A comparative structural and thermochemical analysis revealed structures with a slight difference in the essential B-N bond length, with the piperidine borane having a longer bond even though it has a stronger B-N bond according to predicted bond dissociation energies, a trend common with amine boranes. To identify the most favourable dehydrogenation pathway, BH3-catalysed and uncatalysed dehydrogenation channels have been explored, where the former has been shown to be the favourable process for both complexes. The energy requirements for the hydrogen release reactions are expected to be minimal as evidenced from the calculated dehydrogenation reaction energies, implying their suitability for onboard chemical hydrogen storage.

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Cyclic 2-Aminoethylborane (1,2-Azaboretidine), a Product from the Reaction between Aziridine and Sodium Borohydride.

Cited by 9 publications

References 0 publications

Microwave Spectrum, Structure, Barrier to Internal Rotation, and Dipole Moment of the Aziridine−Borane Complex (C₂H₅N−BH₃)

Microwave Spectrum, Structure, Barrier to Internal Rotation, and Dipole Moment of the Aziridine−Borane Complex (C₂H₅N−BH₃)

Conformational and Substituent Effects on The Rehybridization of Boron in β‐Substituted Ethylboranes

Structural and thermochemical studies of pyrrolidine borane and piperidine borane by gas electron diffraction and quantum chemical calculations

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Cyclic 2-Aminoethylborane (1,2-Azaboretidine), a Product from the Reaction between Aziridine and Sodium Borohydride.

Cited by 9 publications

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Microwave Spectrum, Structure, Barrier to Internal Rotation, and Dipole Moment of the Aziridine−Borane Complex (C2H5N−BH3)

Microwave Spectrum, Structure, Barrier to Internal Rotation, and Dipole Moment of the Aziridine−Borane Complex (C2H5N−BH3)

Conformational and Substituent Effects on The Rehybridization of Boron in β‐Substituted Ethylboranes

Structural and thermochemical studies of pyrrolidine borane and piperidine borane by gas electron diffraction and quantum chemical calculations

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Microwave Spectrum, Structure, Barrier to Internal Rotation, and Dipole Moment of the Aziridine−Borane Complex (C₂H₅N−BH₃)

Microwave Spectrum, Structure, Barrier to Internal Rotation, and Dipole Moment of the Aziridine−Borane Complex (C₂H₅N−BH₃)