Metal‐Free Ammonia–Borane Dehydrogenation Catalyzed by a Bis(borane) Lewis Acid

Lu, Zhenpin; Schweighauser, Luca; Hausmann, Heike; Wegner, Hermann A.

doi:10.1002/anie.201508360

Cited by 82 publications

(91 citation statements)

References 43 publications

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“…As a result of their peculiar structure, compounds 1 act as ditopic Lewis acids that are able to bind ditopic Lewis bases in a chelating manner . Taking advantage of this reactivity, 1 ‐containing compounds have been employed to catalyze inverse electron‐demand Diels–Alder reactions or the dehydrogenation of ammonia‐borane . 9,10‐Dihydro‐9,10‐diboraanthracenes also act as strong electron acceptors, and numerous derivatives undergo fully reversible, stepwise two‐electron reduction, which offers new opportunities for the reductive activation of H 2 and terminal alkynes .…”

Section: Introductionmentioning

confidence: 99%

How Boron Doping Shapes the Optoelectronic Properties of Canonical and Phenylene‐Containing Oligoacenes: A Combined Experimental and Theoretical Investigation

Kirschner

Mewes

Bolte

et al. 2017

Chemistry A European J

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Optimized syntheses of 6,13-dimesityl-6,13-dihydro-6,13-diborapentacene (DBP) and a related compound (DBI) featuring two biphenylene-2,3-diyl units in place of naphthalene-2,3-diyl moieties are reported. Striking differences between the optoelectronic properties of DBP and DBI have been experimentally observed, and explained by quantum chemical calculations. DBP is a member of the oligoacene family, DBI is a linear [N]phenylene derivative. The yellow DBP shows blue photoluminescence, the deep red DBI is nonfluorescent. Both compounds give rise to two reversible redox transitions at E1/2 =-2.03 V, -2.75 V (DBP) and -1.52 V, -2.30 V (DBI; THF, vs. FcH/FcH ). The higher electron affinity of DBI agrees with a lower calculated LUMO energy level [-0.57 eV for DBI with respect to DBP @HF//SCS-MP2/def2-TZVP] and a higher Lewis acidity of its boron centers, which is reflected in the trend of adduct formation with small Lewis bases (MeCN, F ). The thermochemistry underlying this trend, as well as the mechanism of fluorescence quenching in DBI, are revealed by state-of-the-art quantum chemical calculations. It is suggested that the nonradiative deactivation occurs via a low-lying, doubly excited state.

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Section: Introductionmentioning

confidence: 99%

How Boron Doping Shapes the Optoelectronic Properties of Canonical and Phenylene‐Containing Oligoacenes: A Combined Experimental and Theoretical Investigation

Kirschner

Mewes

Bolte

et al. 2017

Chemistry A European J

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“…Unfortunately, regeneration of AB from PAB is still a great challenge . Another class of catalysts can dehydrogenate AB to borazine ( BZ ) and/or polyborazylene ( PBZ ) releasing two or more than two equivalents of H 2 . Sutton et al.…”

Section: Introductionmentioning

confidence: 99%

Designing Metal‐Free Frustrated Lewis Pairs Catalyst for the Efficient Dehydrogenation of Ammonia Borane

Song

2018

Chemistry A European J

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Ammonia borane (AB) has been in the spotlight for the chemical storage of hydrogen over the past decade. However, the development of methods for efficient and controlled hydrogen release from AB under mild conditions is still underway. Herein, using density functional theory (DFT) computations, we designed a metal-free frustrated Lewis pair (FLP) catalyst o-(BPh )C H (NiPr ) (M1) that can efficiently dehydrogenate AB to release more than two equivalents of H under mild conditions. Catalyst M1 can dehydrogenate not only AB to H N=BH (AOB) and H , but also oligomers of AOB with rather low free-energy barriers. The high dehydrogenation activity of M1 is the key of new oligomerization routes to the efficient dehydrogenation of AB to borazine (BZ) or H B-(NH=BH) -NH (PIB) and finally to polyborazylene (PBZ) so that more than two equivalents of H can be released. A first-principle kinetic Monte Carlo (KMC) study reveals that the activity of our catalytic system can be tuned by varying the initial concentration of M1 and AB. This work can guide the design of catalyst for the highly efficient utilization of AB as a hydrogen storage material.

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“…Limited success has been achieved in the dehydrogenation of amine‐boranes with alkaline earth metals . Metal‐free catalysis is another emergent field, and synchronous efforts for the dehydrogenation of 1 are slowly trickling in . Incidentally, it has been suggested by topical theoretical studies that bifunctional non‐metal‐containing species may play a significant role in the dehydrogenation of 1 even in metal‐catalyzed reactions .…”

Section: Introductionmentioning

confidence: 99%

“…reported the formation of borazine after the dehydrocoupling of 1 by a FLP‐based agent on a dimethylxanthene backbone . So there are only two metal‐free catalysts, a FLP that consists of a dimethylxanthene backbone and a bis(borane), that are able to release up to 2 equivalents of H 2 from 1 . Among these, the bis(borane) system is a more robust and a simple catalyst.…”

Section: Introductionmentioning

confidence: 99%

Designing an Effective Metal‐Free Lewis Acid Catalyst for Ammonia‐Borane Dehydrogenation: A DFT Investigation on Triarylboranes

Bhunya

Paul

2017

ChemCatChem

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The catalytic dehydrogenation of ammonia‐borane (NH3BH3) is dominated largely by transition‐metal catalysts. Metal‐free catalysis for NH3BH3 dehydrogenation is a rarity. It is well known that mono‐boron‐based Lewis acids are largely ineffective to facilitate the catalytic dehydrogenation of NH3BH3. Herein, through theoretical investigations, we have identified the routes with catalytic potential for B(C6F5)3 and its congeners and also the factors that are likely to prevent effective catalysis for these systems. Our findings reveal for triarylboranes that potential catalytic dehydrogenation routes comprise of two main events: ion pair formation from NH3BH3 in the presence of a catalyst assisted by a nucleophile and subsequent H2 release from the ion pair. Donor solvents and the B−H hydride of NH3BH3 act as a nucleophile to facilitate ion‐pair formation from NH3BH3 and the Lewis acid catalyst in donor and nondonor solvents, respectively. A good nucleophilic solvent decreases the activation barrier of ion‐pair formation but it increases the activation barrier associated with the subsequent H2 release process. The reverse is true for nondonor solvents, in which case NH3BH3 acts as a nucleophile. Our studies reveal that by the careful tuning of the hydride affinity of the Lewis acid catalyst in combination with nondonor solvents, rate‐limiting barriers for dehydrogenation can be reduced to approximately 19–20 kcal mol−1, which would enable catalytic turnovers at room temperature.

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Metal‐Free Ammonia–Borane Dehydrogenation Catalyzed by a Bis(borane) Lewis Acid

Cited by 82 publications

References 43 publications

How Boron Doping Shapes the Optoelectronic Properties of Canonical and Phenylene‐Containing Oligoacenes: A Combined Experimental and Theoretical Investigation

How Boron Doping Shapes the Optoelectronic Properties of Canonical and Phenylene‐Containing Oligoacenes: A Combined Experimental and Theoretical Investigation

Designing Metal‐Free Frustrated Lewis Pairs Catalyst for the Efficient Dehydrogenation of Ammonia Borane

Designing an Effective Metal‐Free Lewis Acid Catalyst for Ammonia‐Borane Dehydrogenation: A DFT Investigation on Triarylboranes

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