ルテニウムラセミゼーション触媒のリガンド交換におけるCOアシスタンス:アシル中間物質の特定
Jenny B Aberg1, Jonas Nyhlén, Belén Martín-Matute
1Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden.
Journal of the American Chemical Society
|June 19, 2009
まとめ
研究者らは,タート-ブトオキシドを用いて,エタ(5) - (((Ph(5) Cp) Ru(CO) ((2) Clの活性化中に重要なアシル中間物質を特定した. この発見は,炭素一酸化物 (CO) の援助によってリガンド交換が起こり,COリガンドに対する核愛性の攻撃を含むことを確認しています.
科学分野:
- 有機金属化学 有機金属化学
- 反応メカニズム研究 反応メカニズム研究
- スペクトロスコーピーの分析
背景:
- 以前は,タート・ブトオキシド (t-BuOK) によるエタ ((5) - (((Ph ((5) Cp) Ru (((CO)) ((2) Clの活性化メカニズムは不明でした.
- リンガンド交換経路の理解は,新しい触媒プロセスを開発する上で極めて重要です.
研究 の 目的:
- t-BuOKによるeta(5)-((Ph(5)Cp) Ru(CO)(2) Cl活性化のメカニズムを解明する.
- 反応中間物質を特定し,特徴づけること.
- 活性化プロセスにおける一酸化炭素 (CO) 補助の役割を確認する.
主な方法:
- フーリエ変換赤外線 (FT-IR) 顕微鏡を用いて,反応をリアルタイムで監視する.
- 構造の解明のために,核磁共振 (NMR) スペクトロスコーピー (C-13 NMRを含む).
- 密度関数理論 (DFT) の計算は,NMRの割り当てとメカニズム的仮説をサポートします.
主要な成果:
- アシルの中間体である tert-butoxycarbonyl が成功裏に特定されました.
- FT-IRスペクトロスコピーは,COとCOOt-Bu群の特徴的な伸縮振動をそれぞれ1933cm(-1) と1596cm(-1) で明らかにした.
- C-13 NMRスペクトロスコーピーは,COとCOOt-Bu群のそれぞれ209.5ppmと208.7ppmで,DFT計算と一致する明確な信号を示しました.
結論:
- 実験的証拠は,初期活性化段階のCO支援を含むメカニズムを強く支持しています.
- アクティベーションは,COリガンドに対する tert-butoxide の核性攻撃によって発生し,識別されたアシル中間物質を形成します.
- COの補助は,アルコール-アルコキシドの交換にも提案されているが,この段階では中介物質は検出されなかった.
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