DFT studies of dehydrogenation of ammonia–borane catalyzed by [Ir(ItBu′)2]+: A proton transfer mechanism

Ai, Dong-Xia; Qi, Zheng‐Hang; Ruan, Gui-Yu; Zhang, Ye; Liu, Wei; Wang, Yong

doi:10.1016/j.comptc.2014.08.016

Cited by 11 publications

(12 citation statements)

References 95 publications

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“…Several triamidoamine-supported Zr complexes of general formula (κ 4 -NN 3 )ZrX {NN 3 = [N(CH 2 CH 2 NSiMe 3 ) 3 ] 3− ; X = NMe 2 (90), Cl (91), O t Bu (92)} have been exploited for amine−borane dehydrocoupling by Waterman and co-workers, in benzene or THF solutions at T = 65 °C. 105 The compounds are particularly active toward AB and DMAB, proceeding at moderate catalyst loading (between 0.5 and 1 mol %) and during short reaction times (typically 24 h).…”

Section: Group 3: Scandium and Yttriummentioning

confidence: 91%

“…The Nolan research group has used the NHC complex [IrH 2 (I t Bu) 2 ] + ( 64 ) [I t Bu = 1,3-bis( tert -butyl)imidazol-2-ylidene] in AB dehydrogenation in THF/H 2 O mixtures at T = 60 °C, using only 0.001 mol % catalyst. , Compound 64 proved to be extremely robust and active, liberating approximately 3 equiv of H 2 in ca. 29 min.…”

Section: Systematic Collection Of Examples Of Cmh-mediated Ab and Ami...mentioning

confidence: 99%

“…= 60 °C, using only 0.001 mol % catalyst. 90,91 Compound 64 proved to be extremely robust and active, liberating approximately 3 equiv of H 2 in ca. 29 min.…”

Section: Chemical Reviewsmentioning

confidence: 99%

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Ammonia–Borane and Amine–Borane Dehydrogenation Mediated by Complex Metal Hydrides

2016

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This review is a comprehensive survey of the last 10 years of research on ammonia-borane and amine-borane dehydrogenation mediated by complex metal hydrides (CMHs), within the broader context of chemical hydrogen storage. The review also collects those cases where CMHs are the catalyst spent form or its resting state. Highlights on the reaction mechanism (strictly dependent on the CMH of choice) and the catalysts efficiency (in terms of equivalents of H2 produced and relative reaction rates) are provided throughout the discussion.

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Section: Group 3: Scandium and Yttriummentioning

confidence: 91%

Section: Systematic Collection Of Examples Of Cmh-mediated Ab and Ami...mentioning

confidence: 99%

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Ammonia–Borane and Amine–Borane Dehydrogenation Mediated by Complex Metal Hydrides

2016

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“…Iridium-based homogeneous catalysts are particularly efficient in releasing H 2 from ammonia-borane. Since the discovery of ammonia-borane dehydrogenation using iridium PCP pincer complexes by Goldberg et al (1) [14], and the solvolysis of ammonia-borane using the air-and moisture-stable iridium PNP pincer complexes by Graham et al (2) [15], several efficient iridium complexes have been reported, which are [IrH 2 (η 2 -H 2 ) 2 (PCy 3 ) 2 ] + (3) [16,17], the [IrH 2 (I t Bu) 2 ] + [I t Bu = 1,3-bis(tert-butyl)imidazol-2-ylidene] (4) [18,19], the NHC-based Ir(IMes) 2 H 2 Cl (5) [20], the [Cp*Ir(6,6 -(OH) 2 -bpy)(OH 2 )] 2+ (6) [21], [Ir(dppm) 2 ] + (7) [22] and the IrHCl[(PPh 2 (o-C 6 H 4 CO)) 2 H] (8) [23], as shown in Figure 1. Among these, catalysts (2), ( 4), (6) and (8) are extremely air-and moisture-stable and are capable of releasing three, or almost three, equivalents of H 2 from ammonia-borane, under solvolytic and hydrolytic conditions.…”

Section: Introductionmentioning

confidence: 99%

Sustainable Option for Hydrogen Production: Mechanistic Study of the Interaction between Cobalt Pincer Complexes and Ammonia Borane

Tsang²,

Chan

et al. 2020

Catalysts

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The mechanism of the solvolysis/hydrolysis of ammonia borane by iridium (Ir), cobalt (Co), iron (Fe) and ruthenium (Ru) complexes with various PNP ligands has been revisited using density functional theory (DFT). The approach of ammonia borane (NH3BH3) to the metal center has been tested on three different possible mechanisms, namely, the stepwise, concerted and proton transfer mechanism. It was found that the theoretical analyses correlate with the experimental results very well, with the activities of the iridium complexes with different PNP ligands following the order: (tBu)2P > (iPr)2P > (Ph)2P through the concerted mechanism. The reaction barriers of the rate-determining steps for the dehydrogenation of ammonia borane catalyzed by the active species [(tBu)2PNP-IrH] (Complex I-8), are found to be 19.3 kcal/mol (stepwise), 15.2 kcal/mol (concerted) and 26.8 kcal/mol (proton transfer), respectively. Thus, the concerted mechanism is the more kinetically favorable pathway. It is interesting to find that stable (tBu)2PNP Co-H2O and (tBu)2PNP Co-NH3 chelation products exist, which could stabilize the active I-8 species during the hydrolysis reaction cycle. The use of more sterically hindered and electron-donating PNP ligands such as (adamantyl)2P- provides similar activity as the t-butyl analogue. This research provides insights into the design of efficient cobalt catalysts instead of using precious and noble metal, which could benefit the development of a more sustainable hydrogen economy.

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“…Computational studies based on density functional theory (DFT) can help to understand the details of the hydrogen release process at the atomic level. Unfortunately, most computational studies are based on gas-phase models, − which do not resemble the crystal structure all that closely. On the theoretical side, there are only a few investigations on the dehydrogenation mechanism of solid AB.…”

Section: Introductionmentioning

confidence: 99%

First-Principles Study of Intrinsic Defects in Ammonia Borane

2017

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Solid ammonia borane is a promising hydrogen storage material but suffers from a slow and ill-controlled dehydrogenation process. We studied intrinsic point defects that might play a role for hydrogen release by means of first-principles calculations augmented with van der Waals (vdW) corrections. The vdW corrections proved to be crucial for structural properties and also for energies in some cases. For vacancy and interstitial defects of single H as well as of molecular (NH3, BH3) type, we determined formation energies and local lattice structures of the defects in various charge states. Atomic H-related vacancies and interstitials exist predominantly in charged states in agreement with their chemical, i.e., protonic or hydridic, character. For molecular defects, some NH3- and BH3-related neutral defects have rather low formation energies, suggesting that the dehydrogenation of undoped ammonia borane is initiated by the cleavage of the B–N bond. The relaxation pictures associated with H-related defects can explain the observation of a variety of oligomeric products in experiment. Besides, some low-energy defects are found to form H2 molecules spontaneously and thus might catalyze the dehydrogenation reaction of doped ammonia borane.

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DFT studies of dehydrogenation of ammonia–borane catalyzed by [Ir(ItBu′)2]+: A proton transfer mechanism

Cited by 11 publications

References 95 publications

Ammonia–Borane and Amine–Borane Dehydrogenation Mediated by Complex Metal Hydrides

Ammonia–Borane and Amine–Borane Dehydrogenation Mediated by Complex Metal Hydrides

Sustainable Option for Hydrogen Production: Mechanistic Study of the Interaction between Cobalt Pincer Complexes and Ammonia Borane

First-Principles Study of Intrinsic Defects in Ammonia Borane

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