在过渡金属复合体中理解终端与桥接端N2协调
Lynn S Yamout1, Mohamad Ataya1, Faraj Hasanayn1
1Department of Chemistry, American University of Beirut, Beirut 1107 2020, Lebanon.
Journal of the American Chemical Society
|June 28, 2021
概括
这项研究揭示了 (N2) 如何与金属复合物结合,有利于终端或桥梁模式. 了解这些结合偏好对于开发新的氨合成和N2功能化催化剂至关重要.
科学领域:
- 无机化学
- 有机金属化学
- 催化剂
背景情况:
- (N2) 与过渡金属的协调可以在终端或桥梁模式中发生.
- 这些协调模式对于理解合成等过程中的N2激活至关重要.
- 预测特定的金属结合体系统的首选结合模式仍然是一个挑战.
研究的目的:
- 阐明对过渡金属复合物的终端与桥梁N2协调的基本因素.
- 为了确定给定金属连接体系统的最好结合方式.
- 为设计N2功能化和氨合成的改善催化剂提供见解.
主要方法:
- 使用了定量密度函数理论 (DFT) 的计算.
- 进行了定性分子轨道分析 (MO).
- 研究了金属和配体的系统变化,以研究N2协调的吉布斯自由能量.
主要成果:
- 用于将终端转换为桥梁N2复合物的吉布斯自由能量 (2ΔGeq°) 差异很大 (每M-N2键-24.0到+9.1 kcal/mol).
- 基于终端到过桥转换过程中的π-键顺序 (BOπ) 变化提出了一个模型.
- 当转换增加总π键次数 (ΔBOeqπ > 0) 时,通常是当金属为MNM核心的π-MOs贡献1-3个电子时.
结论:
- 根据金属对MNM π系统的电子贡献,可以预测最受欢迎的N2结合模式 (终端与桥接).
- 当金属为MNM π-MOs贡献4个电子时,平衡几乎是无效的,受到分散力的影响.
- 这项工作提供了对N2协调的基本理解,对于设计固催化剂至关重要.
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