鉄複合体触媒によるアンモニア-ボラン脱水化. 地球に豊富な金属触媒を用いたB-Nを含むポリマーモチーフへの潜在的な経路
R Tom Baker1, John C Gordon, Charles W Hamilton
1Department of Chemistry, University of Ottawa, Ottawa, Ontario, Canada.
Journal of the American Chemical Society
|March 21, 2012
まとめ
鉄複合体は,アンモニア-ボラン (NH 3 BH 3 AB) から水素の放出を触媒化し,新しいポリマーを形成します. 特定の鉄複合体は制御された合成とリサイクルを可能にし,先進的な材料のための経済的経路を提供します.
科学分野:
- カタリシス カタリシス カタリシス
- マテリアルサイエンス 材料科学
- 無機化学 無機化学とは
背景:
- アンモニアボラン (NH 3 B H 3 AB) は,高い水素含有量により有望な水素貯蔵材料です.
- ABの脱水化により,価値あるB-Nを含むポリマーが得られるが,その過程の制御は困難である.
- 貴金属の触媒は効果的ですが,コストが高く,土壌に豊富な金属はより経済的な代替品を提供します.
研究 の 目的:
- 鉄複合体をアミドおよびフォスフィンリガンドで合成および特徴づけること.
- 制御された水素放出とポリマー合成のためのアンモニア-ボランとこれらの鉄複合体の反応性を調査する.
- 触媒のリサイクルの可能性を調査し,反応経路に影響を与える要因を特定する.
主な方法:
- アミドとフォスフィンリガンドを含む4つの異なる鉄複合体の合成.
- 合成された鉄複合体の反応とアンモニア・ボランの反応.
- ガス水素の進化の分析と,生成されたB-Nを含むポリマー製品の特徴.
- 複雑な構造と鉄の酸化状態に基づいて,触媒のリサイクル可能性の評価と反応性の比較.
主要な成果:
- アミドとフォスフィンリガンドを含む鉄複合体が成功して合成されました.
- コンプレックス1とコンプレックス2は水素を放出し,混合 (NH) と (NHBH) ポリマーが形成されたが,リサイクルできませんでした.
- 鉄複合体4は,P-Nリガンドによって支えられ,同様のポリマーを作り出し,再利用可能であった.
- 複合体3は,対称なアナログであり,室温で選択的に生成された (NH2BH2) 素早く発生し,Fe2対Fe0の化学反応による可能性が高い.
結論:
- 地球に豊富な鉄複合体は,アンモニア-ボランから水素の放出を触媒化し,B-Nポリマーの合成を可能にします.
- 触媒の設計,特にリガンド環境と鉄酸化状態は,製品の選択性と再利用性に大きく影響します.
- 複合体3は,室温で効率的かつ選択的なポリマー形成を実証し,制御された材料合成のための有望な道を示しています.
関連する概念動画
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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.
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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.