ダブルメタルカチオンを用いたアンミンボロヒドリドの脱水化チューニング
1Department of Materials Science, Fudan University, Shanghai 200433, China.
Journal of the American Chemical Society
|March 12, 2011
まとめ
研究者らは,効率的な水素放出のための新しい二重カタンアミンボロヒドリドを開発した. この材料は,高純度水素と120°C以下の好ましい運動性を提供し,水素貯蔵ソリューションを進めている.
科学分野:
- マテリアルサイエンス 材料科学
- 化学工学は化学工学というものです.
- 水素貯蔵庫は水素を貯蔵する場所です.
背景:
- アミンボロヒドリドは,水素貯蔵材料として有望である.
- 脱水素化の温度と純度を調節することは,実用的なアプリケーションにとって非常に重要です.
- 新しい複雑な構造を開発することは,材料の性能を改善するための鍵です.
研究 の 目的:
- ダブルカチオンを使用して,アンミンボロヒドリドの脱水化特性を調節するための新しい戦略について報告する.
- 最初の二重カタンアミンボロヒドリド,Li(2)Al(BH(4))(5) ·6NH(3) を合成し,特徴づけました.
- 水素の放出能力,運動,純度を評価するために.
主な方法:
- ダブルカタンアンミンボロヒドリドLi(2)Al(BH(4))(5) ·6NH(3) の合成について
- 複雑なイオンの秩序ある配置を確認するために,X線微分を用いた構造的特徴付け.
- 容量,温度,運動,純度を判断するための水素放出測定.
主要な成果:
- 最初のダブルカチオンアンミンボロヒドリド,Li(2)Al(BH(4))(5) ·6NH(3) が成功して合成されました.
- オーダーされたAl ((NH ((3)) ((6) ((3+)) とLi ((2) ((BH ((4)) ((5) ((3-)) イオンを持つ新しい結晶構造が特定されました.
- 物質は,120°C以下で10.0重量%以上の水素を放出し,好ましい運動性と>99%の純度を持つ.
結論:
- ダブルカチオン戦略は,脱水酸化温度と純度を効果的に調整します.
- Li ((2) Al (((BH ((4)) ((5) ·6NH ((3) は,実用的な用途のために優れた水素貯蔵性能を示しています.
- この研究は,先進的なアンミンボロヒドリド水素貯蔵材料の設計に新しい道を開きます.
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関連する概念動画
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...
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.
02:47Alkynes 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.
02:36Regioselectivity 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.
01:38Preparation of Amines: Reductive Amination of Aldehydes and Ketones
Carbonyl compounds and primary amines undergo reductive amination first to produce imines, followed by secondary amines in the same reaction mixture, using selective reducing agents like sodium cyanoborohydride or sodium triacetoxyborohydride. Reductive amination produces different degrees of substitution of amines depending on the starting amine substrate.
01:20Amides to Amines: LiAlH4 Reduction
Amide reduction with strong reducing agents like lithium aluminum hydride proceeds through a nucleophilic acyl substitution to form amines. Primary, secondary, and tertiary amides yield primary, secondary, and tertiary amines, respectively.
Amide reduction requires two equivalents of the reducing agent, acting as a source of hydride ions. As shown in the figure, the reaction is initiated with a nucleophilic attack by the hydride ion at the carbonyl carbon to form a tetrahedral intermediate.
Amide reduction requires two equivalents of the reducing agent, acting as a source of hydride ions. As shown in the figure, the reaction is initiated with a nucleophilic attack by the hydride ion at the carbonyl carbon to form a tetrahedral intermediate.