Base Metal Catalyzed Dehydrogenation of Ammonia−Borane for Chemical Hydrogen Storage

Keaton, Richard J.; Blacquiere, Johanna M.; Baker, R. Tom

doi:10.1021/ja066860i

Cited by 643 publications

(491 citation statements)

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“…22 The major dehydrocoupling product was dimeric (Me 2 NBH 2 ) 2 , assigned by a diagnostic 11 The order of reagent addition is important in the dehydrocoupling reaction. If B(C 6 F 5 ) 3 and Me 2 NHÁBH 3 are dissolved 31 P NMR spectrum are consistent with this formulation. Apparently dehydrocoupling is more favorable than forming stable Lewis pairs, although in this case some of that competing pathway is observed.…”

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confidence: 61%

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Dehydrogenation of amine–boranes with a frustrated Lewis pair

Miller

Bercaw

2010

Chem. Commun.

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Bulky tertiary phosphine/borane Lewis pairs P t Bu 3 /B(C 6 F 5 ) 3 react with amine-boranes to afford dehydrocoupling products and phosphonium borohydride salts.Amine-boranes are the subject of intense interest due to their potential application in hydrogen storage schemes. 1,2 A number of fast and efficient transition metal dehydrocoupling catalysts have been discovered, 3-7 and various coordination compounds relevant to the catalytic pathways have been isolated. [8][9][10] Progress has also been made in the challenging area of regeneration of spent ammonia-borane fuel. [11][12][13] Theoretical studies 14,15 of one amine-borane dehydrocoupling system employing N-heterocyclic carbenes (NHCs) as ligands 3 suggested that the free NHC could heterolytically dehydrogenate NH 3 ÁBH 3 , yielding (NH 2 BH 2 ) n and NHC-H 2 , similar to the H 2 cleavage reactivity of Bertrand's carbenes. 16 Because the reactivity of these NHC species has been compared to that of bulky phosphine/borane ''frustrated Lewis pairs'' (FLPs), it occurred to us that FLPs might also be able to dehydrogenate amine-boranes.FLPs-combinations of particularly bulky Lewis acids and bases that are unable to form traditional Lewis acid/base pairs 17 -exhibit a number of unusual reactions, [18][19][20] in particular the heterolytic cleavage of H 2 , 21-23 which has been utilized for metal-free catalytic hydrogenation of bulky imines. 24,25 Amine activation reactions have also been reported. 26,27 To our knowledge, however, no dehydrogenation reactions have been reported using these systems, 28 although calculations suggest such reactions should be possible. 29 Herein we report that the simple frustrated Lewis pair P t Bu 3 /B(C 6 F 5 ) 3 rapidly and cleanly dehydrogenates amine-boranes at room temperature, with concomitant formation of the phosphonium borohydride salt [ t Bu 3 PH][HB(C 6 F 5 ) 3 ] (Scheme 1).Initial experiments were carried out with Me 2 NHÁBH 3 , a common model for NH 3 ÁBH 3 which has desirable solubility properties and generally releases only 1 equivalent of H 2 . The frustrated Lewis pair P t Bu 3 /B(C 6 F 5 ) 3 was formed according to literature procedures in C 6 D 5 Cl, 22 and no discernable reaction was observed by NMR. The pre-formed FLP was added to a C 6 D 5 Cl solution of Me 2 NHÁBH 3 at 25 1C, giving a clear colorless solution. 30 1 H, 31 P (Fig. 1), 19 F, and 11 B (Fig. 2) The order of reagent addition is important in the dehydrocoupling reaction. If B(C 6 F 5 ) 3 and Me 2 NHÁBH 3 are dissolved Scheme 1 Fig. 2 11 B NMR spectrum shortly after FLP-mediated dehydrocoupling of Me 2 NHÁBH 3 . The underlying broad feature arises from borosilicate glass in the probe construction.

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confidence: 61%

“…1), 19 F, and 11 B (Fig. 2) NMR experiments confirmed that 495% of the FLP-derived product was [ t Bu 3 PH][HB(C 6 F 5 ) 3 ]. 22 The major dehydrocoupling product was dimeric (Me 2 NBH 2 ) 2 , assigned by a diagnostic 11 The order of reagent addition is important in the dehydrocoupling reaction.…”

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confidence: 80%

Dehydrogenation of amine–boranes with a frustrated Lewis pair

Miller

Bercaw

2010

Chem. Commun.

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“…This of course suggested catalytic approaches that offer the opportunity to increase the rate and decrease the temperature of onset of hydrogen release. R&D performed by the CHSCoE (Baker, Sneddon, Heinekey, Goldberg, Burrell, and their colleagues [74][75][76][77][78][79][80][81][82][83][84][85][86][87] ) and by researchers outside of the Center resulted in the description of many different catalytic processes and catalysts for the dehydrogenation of ammonia borane (Figure 14). In order to perform the catalytic dehydrogenation of ammonia borane, it is necessary to make intimate contact of ammonia borane with the catalyst.…”

Section: Catalytic Release Of Hydrogen From Ammonia Boranementioning

confidence: 99%

Accelerating the Understanding and Development of Hydrogen Storage Materials: A Review of the Five-Year Efforts of the Three DOE Hydrogen Storage Materials Centers of Excellence

Klebanoff

Ott

Simpson

et al. 2014

Metallurgical and Materials Transactions E

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A technical review of the progress achieved in hydrogen storage materials development through the U.S. Department of Energy's (DOE) Fuel Cell Technologies Office and the three Hydrogen Storage Materials Centers of Excellence (CoEs), which ran from 2005 to 2010 is presented. The three CoEs were created to develop reversible metal hydrides, chemical hydrogen storage materials, and high-specific-surface-area (SSA) hydrogen sorbents. For each CoE, the approach taken is specified, key outcomes and accomplishments identified, and recommendations for future work are suggested. The Metal Hydride Center of Excellence addresses work on destabilized hydrides, including the LiBH/Mg 2 NiH 4 system, borohydrides, amides, and alanes; and compares the best materials to DOE targets. The Chemical Hydrogen Storage Center of Excellence discusses the classes of materials studied for chemical hydrogen storage, focusing on ammonia borane and examines the progress in developing efficient regeneration schemes. The Hydrogen Sorption Center of Excellence describes the progress in developing high-SSA sorbents and pathways for developing improved materials capable of achieving DOE targets. The phenomenon of spillover is also observed and its importance to ensuring improved measurements is discussed. Through the five-year effort of the Hydrogen Storage Materials Centers of Excellence, significant progress was achieved in developing and understanding hydrogen storage materials.

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“…The search for effective and safe hydrogen storage materials is one of the most difficult challenges for the development of a hydrogen society in the future [3][4][5]. Boron-nitrogen containing compounds are expected to find applications in hydrogen storage materials because of their high hydrogen density [6,7].…”

Section: Introductionmentioning

confidence: 99%

Influence of morphology of hollow silica–alumina composite spheres on their activity for hydrolytic dehydrogenation of ammonia borane

et al. 2017

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Hollow silica-alumina composite spheres were prepared by a polystyrene (PS) template method using various amounts of PS suspension. Homogeneous hollow spheres prepared using 40 g were found to be with a diameter of about 300 nm in scanning electron microscopy, and transmission electron microscopy demonstrated their hollow sphere morphology. From the nitrogen adsorption isotherm results, the homogeneous hollow spheres prepared using 40 g of the PS suspension were found to be an ordered pore structure. The activities of the hollow spheres prepared using various amounts of the PS suspension for hydrolytic dehydrogenation of ammonia borane were compared. The results showed that 10, 7, and 6 mL of hydrogen were evolved from the aqueous ammonia borane solution in about 40 min in the presence of the hollow spheres prepared using 40, 80, and 120 g of PS suspension, respectively. The homogeneous hollow spheres with an ordered pore structure showed the highest activity among all the hollow spheres. The amount of acid sites and the coordination number of aluminum active species were characterized using neutralization titration and solid-state 27 Al magic angle spinning nuclear magnetic resonance spectroscopy. The homogeneous hollow spheres with an ordered pore structure had high amount of acid sites and 4-coordinated aluminum species. The relative proportion of 4-coordinated aluminum species was related to the dispersion of aluminum species. These results indicate that the homogeneous hollow spheres with an ordered pore structure showed the high activity because of high amount of acid sites induced by the highly dispersed aluminum species.

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Base Metal Catalyzed Dehydrogenation of Ammonia−Borane for Chemical Hydrogen Storage

Cited by 643 publications

References 18 publications

Dehydrogenation of amine–boranes with a frustrated Lewis pair

Dehydrogenation of amine–boranes with a frustrated Lewis pair

Accelerating the Understanding and Development of Hydrogen Storage Materials: A Review of the Five-Year Efforts of the Three DOE Hydrogen Storage Materials Centers of Excellence

Influence of morphology of hollow silica–alumina composite spheres on their activity for hydrolytic dehydrogenation of ammonia borane

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