電子と媒体の影響は,カチオンのIr (III) 複合体によるアレンC[bond]H活性化の速度に影響する
David M Tellers1, Cathleen M Yung, Bruce A Arndtsen
1Division of Chemical Sciences, Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720, USA.
Journal of the American Chemical Society
|February 14, 2002
まとめ
この研究では,イリジウム複合体は,イオンペアメカニズムを通じてアレン内のC-H結合を活性化させ,トリフラート解離が活性化に先行することを明らかにしました. 反応性は,イリジウム複合体とアレン基板の両方の電子ドナー置換物によって強化されます.
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
- 反応メカニズム 反応メカニズム
背景:
- アレネC-H活性化は,有機金属化学における重要な変換である.
- 機械的な経路を理解することは,効率的な触媒の設計の鍵です.
研究 の 目的:
- ディクロロメタン溶液中のCp(L) IrMe(X) 複合体によるアレンC-H活性化の詳細なメカニズムを調査する.
- 触媒サイクルにおけるイオン対形成とリガンド解離の役割を明らかにする.
主な方法:
- 様々なリガンド (L) とカウンターイオン (X) を含むCp(L) IrMe(X) コンプレックスを用いた詳細なメカニズム研究.
- CH(2)Cl(2) 溶液における運動分析,イオン対相互作用を調査するために塩を加えた研究を含む.
- 密度関数理論 (DFT) の計算は,機械的解釈をサポートする.
主要な成果:
- トリファレットのCp(L) IrMe(OTf) から離子ペアを形成する解離はC-H活性化に先行する.
- 反応性は媒介に依存しており,BAr (f) のような弱調整アニオンを用いた"特殊塩効果"によって著しく強化することができる.
- アレンの電子ドナー置換物質はC-H活性化率を高め,フォスフィンリガンドの電子効果は主に平衡前リガンド解離に影響する.
結論:
- C-H活性化メカニズムは,最初のトリフラート解離により,カチオンイリジウム中間物質を形成します.
- 整体反応速度は,イリジウム複合体とアレン基板の両方の電子提供グループによって最適化されます.
- DFTの計算は,提案されたメカニズムモデルを支持し,リガンド可変性およびイオンペアリングの重要性を強調しています.
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