对于{(5-C5Me4H) 2Zr]2(mu2,eta2,eta2-N2) 和{[PhP(CH2SiMe2NSiMe2CH2) PPh]Zr}2(mu2,eta2,eta2-N2) 复合物来说,二二化是否遵循不同的机制?
Petia Bobadova-Parvanova1, Qingfang Wang, David Quinonero-Santiago
1Cherry L. Emerson Center for Scientific Computation and Department of Chemistry, Emory University, Atlanta, Georgia 30322, USA.
Journal of the American Chemical Society
|August 31, 2006
概括
密度函数理论计算揭示了连接体刚性决定了二化. 奇里克型复合体中的刚性连接体环境有助于多重H(2) 添加,与灵活的Fryzuk型复合体不同.
科学领域:
- 有机金属化学 有机金属化学
- 催化剂是一种催化剂.
- 计算化学计算化学
背景情况:
- 二 (N2) 化对于氨合成至关重要.
- 复合体为N2激活提供了有希望的催化途径.
- 了解N2化中的机械差异是催化剂设计的关键.
研究的目的:
- 为了比较两个不同的二基复合物的二化机制.
- 阐明连接体环境刚度在催化反应中的作用.
- 确定控制成功化N2的关键因素.
主要方法:
- 使用密度函数理论 (DFT) 的计算.
- 对奇里克型和弗里祖克型复合物的反应途径进行比较.
- 分析中间体,能源障碍和电子结构.
主要成果:
- 连接物刚性显著影响N2化机制.
- 基里克型复合物与刚性连接体形成非H桥接中间体,使进一步的H2添加成为可能.
- 具有柔性连接体的Fryzuk型复合物形成H桥介质,阻碍了随后的H2添加.
- 在环丁联体上的甲基替代模式并没有从根本上改变化机制.
结论:
- 催化剂的配体环境的不灵活性对于高效的二化是至关重要的.
- 非H桥接中间体的形成受到刚性连接体的支持,降低多次H2添加的激活能量.
- DFT为设计有效的N2减排催化剂提供了有价值的见解.
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