ダイナミックメカニズムは,アルカンとアレンにおける高酸化状態のIr (V) -H中間および調整複合体を,カチオン性Ir (III) フォスフィンのC-H活性化から回避する
Ryan Carlsen1, Nathan Wohlgemuth1, Lily Carlson1
1Department of Chemistry and Biochemistry , Brigham Young University , Provo , Utah 84602 , United States.
Journal of the American Chemical Society
|August 2, 2018
まとめ
密度関数理論は,有機金属反応のダイナミクスを完全に捉えることができない. ダイレクトダイナミクスシミュレーションでは 介在物質はC-H活性化でバイパスされ 機械的経路が曖昧になる
科学分野:
- 有機金属化学
- コンピュータ化学
- 反応ダイナミクス
背景:
- 密度関数理論 (DFT) は,最小エネルギー経路が反応ダイナミクスを正確に表現すると仮定して,有機金属反応機構をモデル化するために一般的に使用されます.
- 標準の2段階の酸化加減除去機構は,C−H活性化反応のためにしばしば用いられる.
研究 の 目的:
- メタンとベンゼンのC−H活性化による詳細な反応ダイナミクスを調査する.
- IrV-Hのような中間物質が反応中に一時的に形成されるか,またはバイパスされるかを決定する.
- 協調したプロセスと段階的なプロセスを区別して,機械的経路を解明する.
主な方法:
- 準古典的なダイナミックシミュレーションが反応軌道をモデル化するために使用されました.
- シミュレーションは,酸化加算移行状態の振動平均速度分布から開始された.
- 分析は,中間物質の運命と製品形成の性質に焦点を当てた.
主要な成果:
- 生産的な反応軌道の重要な部分は,提案されたIrV-H中間物質を回避した.
- 観測されたダイナミクスは,酸化加減エネルギー表面で発生するシグマ結合転移経路に似ています.
- イリジウム中心からのアルカンおよびアレン産物の完全な解離は,弱調整複合体を回避して,還元性除去移行状態を横切ったときに観察された.
結論:
- この研究は,DFTによる最小エネルギー経路が有機金属反応のダイナミクスを完全に説明するという仮定に異議を唱える.
- この発見は,C-H活性化における2段階と1段階のメカニズムの境界が曖昧であることを示唆している.
- 還元後の除去で観察された弱C-H協調複合体は,真の反応中間物ではなく,溶媒ケージの人工物である可能性があります.
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