碳离子从酸化合物分离:一个实验和计算的调查调查
Joseph G Cordaro1, Robert G Bergman
1Department of Chemistry, University of California, Berkeley, CA 94720, USA.
Journal of the American Chemical Society
|December 23, 2004
概括
加热一种复合物导致形成一种新的碳化合物和三甲. 这种反应通过三甲基离子离开组进行,由动力学和计算研究证实.
科学领域:
- 有机金属化学 有机金属化学
- 化学 的化学
- 反应机制 反应机制
背景情况:
- 含有乙联体的有机金属复合物在催化和合成中很重要.
- 在有机金属复合体中,醇基联体,特别是三甲基组的反应性具有显著的兴趣.
- 了解连接体解离路径对于设计新的催化过程至关重要.
研究的目的:
- 为了研究一种酸化复合物的热分解路径,Cp(PMe(3)) Ir(H) [C(O) CF(3) ].
- 阐明三甲基离子 (CF(3) ((-)) 从有机金属中心解离的机制.
- 探索不同基基组和辅助配体对反应结果的影响.
主要方法:
- 酸化物复合物的合成和表征.
- 动力学研究以确定不同条件下的反应速率.
- 同位素标记实验 (例如,使用CD(3)OD) 来追踪反应途径.
- 溶剂效应研究探讨溶剂的作用.
- 密度函数理论 (DFT) 计算,包括溶剂效应,以建模反应机制.
- 使用奇拉基底的立体化学研究来评估反应立体化学.
主要成果:
- 加热Cp(PMe(3)) Ir(H) [C(O) CF(3) ]在数量上产生Cp(PMe(3)) Ir(CO) 和三甲 (CF(3) H).
- 证据支持一种机制,涉及三甲基离子 (CF) 的初始解离,形成离子对中间体.
- 类似的甲基和化物复合物也会释放出CF(3)(-),产生化碳酸.
- 其他甲基乙基化物清除R (F) -H的速度比CF (H) 清除快.
- 立体化学研究表明,在碳离子电离和质子转移过程中,配置和反体纯度保持高.
结论:
- 三甲基离子 (CF(3)(-)) 在有机金属反应中可以作为可行的脱离组.
- 反应通过离子对机制进行,与简单的还原性消除或脱碳化不同.
- 醇基组的电子和固体性质显著影响了排泄速度.
- 观察到的立体化学保留突出显示了离子对形成和随后的质子化的受控性质.
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