Related Experiment Video
Updated: Jun 4, 2026
08:40
Synthesis of Metal Nanoparticles Supported on Carbon Nanotube with Doped Co and N Atoms and its Catalytic Applications in Hydrogen Production
Published on: December 6, 2021
Transition metal catalysed ammonia-borane dehydrogenation in ionic liquids
William R H Wright1, Emily R Berkeley, L R Alden
1Department of Chemistry and Center for Catalysis Research and Innovation, University of Ottawa, Ottawa, ON, K1N 6N5 Canada.
Chemical Communications (Cambridge, England)
|February 2, 2011
Summary
Combining ionic liquids and transition metal catalysts enhances ammonia-borane (AB) dehydrogenation. A specific ruthenium catalyst in an ethylsulfate ionic liquid maximizes hydrogen release selectivity and extent.
Area of Science:
- Catalysis
- Materials Science
- Chemical Engineering
Background:
- Ammonia-borane (AB) is a promising hydrogen storage material.
- Efficient hydrogen release from AB is crucial for practical applications.
- Combining different catalytic pathways can improve dehydrogenation efficiency.
Purpose of the Study:
- To investigate the synergistic effects of ionic liquids (ILs) and transition metal catalysts on ammonia-borane (AB) dehydrogenation.
- To optimize the AB dehydrogenation process for maximum hydrogen yield and selectivity.
- To identify the optimal IL anion for enhanced catalytic activity.
Main Methods:
- Utilized a transition metal catalyst precursor, RuCl(2)(PMe(3))(4).
- Employed various ionic liquids (ILs) with different coordinating anions.
- Analyzed the hydrogen release pathways and quantified the extent and selectivity of AB dehydrogenation.
Main Results:
- The combination of ILs and the Ru-based catalyst significantly improved AB dehydrogenation.
- An IL featuring a moderately coordinating ethylsulfate anion demonstrated the highest performance.
- Maximized AB dehydrogenation selectivity and extent were achieved under optimized conditions.
Conclusions:
- Ionic liquids can effectively enhance transition metal-catalyzed ammonia-borane dehydrogenation.
- The choice of IL anion plays a critical role in optimizing catalytic efficiency.
- This approach offers a promising strategy for efficient hydrogen generation from ammonia-borane.
Related Concept Videos
02:10Reduction of Alkynes to trans-Alkenes: Sodium in Liquid Ammonia
Alkynes can be reduced to trans-alkenes using sodium or lithium in liquid ammonia. The reaction, known as dissolving metal reduction, proceeds with an anti addition of hydrogen across the carbon–carbon triple bond to form the trans product. Since ammonia exists as a gas (bp = −33°C) at room temperature, the reaction is carried out at low temperatures using a mixture of dry ice (sublimes at −78°C) and acetone.
When dissolved in liquid ammonia, an alkali metal, such as sodium, dissociates into a...
When dissolved in liquid ammonia, an alkali metal, such as sodium, dissociates into a...
03:08Hydroboration-Oxidation of Alkenes
In addition to the oxymercuration–demercuration method, which converts the alkenes to alcohols with Markovnikov orientation, a complementary hydroboration-oxidation method yields the anti-Markovnikov product. The hydroboration reaction, discovered in 1959 by H.C. Brown, involves the addition of a B–H bond of borane to an alkene giving an organoborane intermediate. The oxidation of this intermediate with basic hydrogen peroxide forms an alcohol.
02:23Alcohols from Carbonyl Compounds: Reduction
Reduction is a simple strategy to convert a carbonyl group to a hydroxyl group. The three major pathways to reduce carbonyls to alcohols are catalytic hydrogenation, hydride reduction, and borane reduction.
Catalytic hydrogenation is similar to the reduction of an alkene or alkyne by adding H2 across the pi bond in the presence of transition metal catalysts like Raney Ni, Pd–C, Pt, or Ru. Aldehydes and ketones can be reduced by this method, often under mild to moderate heat (25–100°C) and...
Catalytic hydrogenation is similar to the reduction of an alkene or alkyne by adding H2 across the pi bond in the presence of transition metal catalysts like Raney Ni, Pd–C, Pt, or Ru. Aldehydes and ketones can be reduced by this method, often under mild to moderate heat (25–100°C) and...
02:47Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
Introduction
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
02:17Reduction of Alkenes: Asymmetric Catalytic Hydrogenation
Catalytic hydrogenation of alkenes is a transition-metal catalyzed reduction of the double bond using molecular hydrogen to give alkanes. The mode of hydrogen addition follows syn stereochemistry.
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
02:36Regioselectivity and Stereochemistry of Hydroboration
A significant aspect of hydroboration–oxidation is the regio- and stereochemical outcome of the reaction.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.