在CpW(CO) 3*与易斯基的联体替代中的19电子中间体
James F Cahoon1, Matthias F Kling, Karma R Sawyer
1Department of Chemistry, University of California, Berkeley, California 94720, USA.
Journal of the American Chemical Society
|March 9, 2006
概括
光化学反应显示,19电子基是连接体替代中的稳定中间体. 这一发现为17电子有机金属基的关联替代机制提供了新的见解.
科学领域:
- 有机金属化学 有机金属化学
- 摄影化学的使用.
- 频谱学是一种光谱学.
背景情况:
- 了解有机金属基的反应性对于催化和合成至关重要.
- 过渡中间体,如19电子物种在反应机制中的作用仍然是一个活跃的研究领域.
研究的目的:
- 为了研究[CpW(CO) 3) 2与P(OMe) 3. 3的光化学反应.
- 在纳米秒和微秒时间尺度上阐明17电子和19电子基的反应路径和动力学.
- 为了确定19电子物种的性质,作为一个中间或过渡状态.
主要方法:
- 步骤扫描FTIR光谱学被用来研究纳秒和微秒时间尺度上的反应.
- 在532nm的光解被用来产生激进物种.
- 进行了动态分析,以确定反应障碍和反应途径.
主要成果:
- 光解产生了17电子基[CpW(CO) 3]*,与19电子基[CpW(CO) 3P(OMe) 3**形成了平衡.
- 这种19电子基的主要途径涉及碳酸的损失,形成[CpW(CO) 2P(OMe) 3* (屏障:7.6 ± 0.3 kcal/mol).
- 对于19电子基的一个小路径 (<20%) 是不成比例,产生[CpW(CO) 3P(OMe) 3+和[CpW(CO) 3--.
- 在微秒时间尺度上,17电子基[CpW(CO) 2P(OMe) 3*二聚变,形成[CpW(CO) 2P(OMe) 3]2.2.
结论:
- 这种19个电子的物种是稳定的中间体,而不是过渡状态,在连接体替代反应中.
- 这种反应模式很可能是经历关联置换的17电子有机金属基的特征.
- 这项研究提供了对19电子基中间体的直接观察和表征.
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