強化されたC-H活性化のために,フォスフィノエタンリガンドの触媒調節
Thomas R Cundari1, J Oscar C Jimenez-Halla, Glenn R Morello
1Department of Chemistry and Center for Advanced Scientific Computing and Modeling, University of North Texas, P.O. Box 305070, Denton, Texas 76203-5070, USA. tomc@unt.edu
Journal of the American Chemical Society
|September 6, 2008
まとめ
この研究では,dfmpeのような酸化フォスフィンリガンドを含むニッケル・ナイトレン複合体は,金属・アミンの形成を安定させることで,C−H結合の触媒性アミネーションを大幅に改善することを発見した. これは,以前の dtbpe リガンドの限界を克服します.
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
- コンピューティング・ケミストリー
背景:
- C−H結合の触媒性アミネーションは,窒素を含む化合物の合成に不可欠である.
- 前回のニッケル基触媒では,ビス・ディ・テート・ブチル・フォスフィノ・エタン (dtbpe) リガンドを用いて,アミン形成の熱力学的限界を示した.
- dtbpe-ligatedシステムにおけるラジカルリバウンドの高いエンド熱性は,効率的な触媒サイクルを妨げました.
研究 の 目的:
- 触媒C-Hアミネーションを改善するために,ニッケル-ナイトレン複合体の新しいリガンド設計を調査する.
- ビス (di) トリフルオロメチル (phosphino) エタン (dfmpe) リガンドを使用する熱力学および運動的可行性を計算的に評価する.
- 効率的なC-Hアミネーションのための有望な前触媒候補を特定する.
主な方法:
- 密度関数理論 (DFT) の計算を用いて反応経路をモデル化しました.
- 水素原子の抽象化とラジカルリバウンドの熱力学パラメータ (エンタルピー変化) を計算した.
- 触媒サイクル再生を含む主要なステップの動的障壁を分析した.
主要な成果:
- dtbpeをdfmpeリガンドに置き換えることで,ラジカルリバウンドステップが劇的に改善され,高度に内熱から外熱 (ΔH = -7.8 kcal/mol) に変更されました.
- 酸化DFMPEリガンドは,金属-アミン結合の強さを高め,製品形成を促進します.
- 計算により,dfmpeを含むニッケル・ナイトレン複合体は,21,3 kcal/molの計算HAAバリアを持つ,触媒C-Hアミネーションにおいて有望であることが示された.
結論:
- 酸化フォスフィンリガンド,特にdfmpeによってサポートされるニッケル・ナイトレン複合体は,触媒C−Hアミネーションにおいて非常に有望である.
- dfmpe結合による金属アミンの中間物の安定性の向上は,以前の熱力学的障害を克服します.
- この研究は,効率的なC-H機能化のための次世代触媒の設計のためのコンピューティング基盤を提供します.
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