コバルトにおけるボリル媒介の可逆H2活性化:触媒性水素化,脱水素化,移転水素化
1Division of Chemistry and Chemical Engineering, California Institute of Technology , Pasadena, California 91125, United States.
Journal of the American Chemical Society
|October 2, 2013
まとめ
新しいコバルト (I) -N2複合体とビスフォスフィノボリルリガンドは,可逆的な二水素活性化を可能にします. このシステムは,触媒的なオレフィン水素化およびアミン-ボラン脱水素化の可能性を示しています.
科学分野:
- 有機金属化学 有機金属化学
- カタリシス カタリシス カタリシス
- 無機合成の無機合成とは
背景:
- コバルト複合体は,触媒的な用途のために研究されています.
- リガンドの設計は,チューニング反応性にとって極めて重要です.
- を含むリガンドは,ユニークな電子的および構造的特性を有しています.
研究 の 目的:
- メリディナルビスフォスフィノボリル (PBP) リガンドで支えられているコバルト (I) -N2複合体を合成し,特徴づけること.
- 二水素とアミン-ボランとのコバルト複合体の反応性を調査する.
- ボリル・コバルトシステムの水素化および脱水化反応における触媒的可能性を調査する.
主な方法:
- PBPリガンドを用いたコバルト (I) -N2複合体の合成.
- コバルト複合体が二水素と反応して二水素種を形成する.
- スペクトロスコピ的方法を用いた中介物質および製品の特徴づけ.
- オレフィン水素化およびアミン-ボラン脱水酸化における触媒活性評価.
主要な成果:
- 安定したコバルト (((I) -N2複合体 (2) が合成されました.
- 複合体2は二水素と逆向き反応し,二水素ボラトコバルト二水素 (3) を形成する.
- ボリル・コバルト系は,オレフィン水素化およびアミン・ボラン脱水化/トランスファー水素化における触媒活性を示した.
結論:
- ビスフォスフィノボリルリガンドは,コバルトによる可逆二水素活性化を促進する.
- ボリル・コバルト系は,触媒性水素化および脱水素化反応のための有望なプラットフォームです.
- この研究は,金属の反応性を制御するためのリガンドフレームワークにボールを組み込むことの有用性を強調しています.
関連する概念動画
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.
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...
02:13Reduction of Alkenes: Catalytic Hydrogenation
Alkenes undergo reduction by the addition of molecular hydrogen to give alkanes. Because the process generally occurs in the presence of a transition-metal catalyst, the reaction is called catalytic hydrogenation.
Metals like palladium, platinum, and nickel are commonly used in their solid forms — fine powder on an inert surface. As these catalysts remain insoluble in the reaction mixture, they are referred to as heterogeneous catalysts.
The hydrogenation process takes place on the surface of...
Metals like palladium, platinum, and nickel are commonly used in their solid forms — fine powder on an inert surface. As these catalysts remain insoluble in the reaction mixture, they are referred to as heterogeneous catalysts.
The hydrogenation process takes place on the surface of...
02:24Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation
Introduction
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
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.