エポキシドからレニウム触媒によるO原子移転の運動学とメカニズム
1Department of Chemistry, Oregon State University, Corvallis, Oregon 97331-4003, USA. gablek@chem.orst.edu
Journal of the American Chemical Society
|September 4, 2003
まとめ
Tp'ReO(3) によって触媒されるエポキシド酸素原子のトリフェニルフォスフィンへの移転には,複雑なメカニズムが含まれています. 孤立したレニウムの種も,現地で生成されたレニウムの種も,高い触媒効率を示し,直接の原子移転とエポキシードリングの膨張を含む二重経路を明らかにします.
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
- 反応メカニズム 反応メカニズム
背景:
- レニウム-オクソ複合体は,酸素原子移転反応の効果的な触媒である.
- これらの触媒プロセスの複雑なメカニズムを理解することは,それらの効率を最適化するために不可欠です.
研究 の 目的:
- Tp'ReOによって触媒化されたエポキシドからトリフェニルフォスフィンへの酸素原子移転の複雑な反応機構を解明する.
- 触媒サイクルに関与する主要な中間物質を特定し,特徴づけること.
- 異なる反応経路間の競争を調査する.
主な方法:
- 反応中介物質を特定するための光譜分析 (NMR,IR).
- 反応の順序と速度を決定するための運動学的研究.
- レーニウムを含有する種の分離と特徴付け.
- 提案された経路を区別するための競争実験.
主要な成果:
- Tp'ReO(3) の還元により,反応性のある種,おそらくTp'ReO(2) が生成され,迅速に分離可能なTp'Re(O) ((OH) ((2) (1) またはTp'Re(O) ((OEt) ((OH) (3) を形成する.
- 触媒1と3は,純化されていない混合物と同等の効率を示し,複雑な動力学で,最初の爆発に次いで擬似ゼロ順序の行動を示す.
- syn-Tp'Re ((O) ((diolate) 複合体が観察されているが,そのサイクル逆転だけでは,回転頻度を説明できず,調整されたエポキシド中間物質を示唆している.
- 競争実験では,直接の原子移転と環の膨張の間の分割が二酸化塩酸のサイクル逆転に続くことを示しています.
結論:
- 触媒的酸素原子移転は,直接の原子移転とエポキシードリングの膨張経路の複雑な相互作用を経由して行われます.
- コーディネートされたエポキシド中間物質は,これらの競合する経路を分割して,重要な役割を果たします.
- ディオラート複合体を含む,特定されたレニウム種は,触媒システムの重要な構成要素である.
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