Use of crown ethers to isolate intermediates in ammonia-borane dehydrocoupling reactions

Less, Robert J.; García‐Rodríguez, Raúl; Simmonds, Hayley R.; Allen, Lucy K.; Bond, Andrew D.; Wright, Dominic S.

doi:10.1039/c6cc00088f

Cited by 12 publications

(8 citation statements)

References 29 publications

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“…Theoretical calculations and experimental results demonstrated that the reaction from AaDB to form ADB included three important intermediates: [H 2 B(NH 3 )(THF)] + [BH 4 ] − , [(THF)BH 2 NH 2 ]( η 2 ‐H 2 )BH 3 , and NH 2 BH 2 (Scheme ). The [H 2 B(NH 3 )(THF)] + cation was formed in a similar manner to the diammoniate of diborane ([H 2 B(NH 3 ) 2 ][BH 4 ], DADB) described in Section 2.3, which was confirmed by the reaction of AB and AlCl 3 . Hydrogen scrambling then took place through the DHB interaction between the hydridic H − of BH 4 − and an N−H unit of [H 2 B(NH 3 )(THF)] + , leading to the intermediate side‐on‐coordinated dihydrogen complex [(THF)BH 2 NH 2 ]( η 2 ‐H 2 )BH 3 .…”

Section: The Nucleophilicity Of the B−h Bonding Pair Electronsmentioning

confidence: 99%

A New Perspective on Borane Chemistry: The Nucleophilicity of the B−H Bonding Pair Electrons

et al. 2019

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A number of recently discovered nucleophilic boron compounds, such as boryl anions and borylenes, are breaking the rules regarding boron and boron‐containing compounds and their reputation as Lewis acids/electrophiles. In a similar fashion, the B−H bonding pair electrons in boranes also show nucleophilicity which is ascribed to the lower electronegativity of boron relative to that of hydrogen. However, this nucleophilicity of the B−H bond has received far less attention. Explorations of the nucleophilicity of the B−H bonding pair electrons have led to the formation of B−H−B bonded units and B−H⋅⋅⋅H−Y dihydrogen bonds, based on which new chemistry has been uncovered, including the elucidation of the mechanism of formation of aminodiborane (ADB), the diammoniate of diborane (DADB), and lithium or sodium salts of octahydrotriborates (B3H8−), as well as the development of more convenient and straightforward synthetic routes to these reagents. Moreover, the recognition of the nucleophilic properties of the B−H bonding pair electrons will also help to more deeply understand the different mechanisms operating in hydroboration reactions.

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Section: The Nucleophilicity Of the B−h Bonding Pair Electronsmentioning

confidence: 99%

A New Perspective on Borane Chemistry: The Nucleophilicity of the B−H Bonding Pair Electrons

et al. 2019

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“…It was found that these acids are not catalyzing the dehydrogenation of NH 3 ⋅BH 3 , but act as an initiator. The initiation step was proposed to go through either protonolysis of the B−H bond by a Brønsted acid or by hydride abstraction by a strong Lewis acid, forming borenium cation 31 (Scheme ) . Subsequently, the borenium intermediate 31 reacts with another equivalent of NH 3 ⋅BH 3 followed by elimination of dihydrogen and formation of 33 .…”

Section: Acid and Base‐initiated Dehydrogenationmentioning

confidence: 99%

Dehydrogenation of Amine–Boranes Using p‐Block Compounds

Boom

Jupp

Slootweg

2019

Chemistry A European J

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Amine–boranes have gained a lot of attention due to their potential as hydrogen storage materials and their capacity to act as precursors for transfer hydrogenation. Therefore, a lot of effort has gone into the development of suitable transition‐ and main‐group metal catalysts for the dehydrogenation of amine–boranes. During the past decade, new systems started to emerge solely based on p‐block elements that promote the dehydrogenation of amine–boranes through hydrogen‐transfer reactions, polymerization initiation, and main‐group catalysis. In this review, we highlight the development of these p‐block based systems for stoichiometric and catalytic amine–borane dehydrogenation and discuss the underlying mechanisms.

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“…The coordination between alkali metals and Me2NH•BH3 and/or their dehydrogenation products is well documented, typically relying on hydrogen bond-stabilised interactions with the highly polarised -NR2-BH3 moieties. 7,21,23 DOSY experiments suggest that this species is monomeric in solution (Table S2). Additional experiments evidenced only small changes in the diffusion coefficient during the catalytic process, ruling out the formation of aggregates or dimers in solution.…”

Section: Introductionmentioning

confidence: 99%