Institut für Chemie, Technische Universität Berlin, 10623 Berlin, Germany.
Institut für Chemie, Technische Universität Berlin, 10623 Berlin, Germany;
Proc Natl Acad Sci U S A. 2019 Oct 22;116(43):21416-21420. doi: 10.1073/pnas.1913664116. Epub 2019 Oct 7.
An unprecedented, spontaneous, and complete cleavage of the triple bond of N in the thermal reaction of N with TaN was observed experimentally by Fourier transform ion cyclotron resonance mass spectrometry; mechanistic aspects of the degenerate ligand exchange were addressed by high-level quantum chemical calculations. The "hidden" dis- and reassembly of N, mediated by TaN, constitutes a full catalytic cycle. A frontier orbital analysis reveals that the scission of the N triple bond is essentially governed by the donation of d-electrons from the 2 metal centers into antibonding π*-orbitals of N and by the concurrent migration of electrons from bonding π- and σ-orbitals of N into empty d-orbitals of the metals. This work may contribute to a rational design of catalysts in order to reduce the still enormous energy demand required for an artificial dinitrogen activation.
实验中通过傅里叶变换离子回旋共振质谱法观察到 N 与 TaN 的热反应中 N 键三重键的空前、自发和完全断裂；通过高水平量子化学计算研究了退化配体交换的反应机理。由 TaN 介导的“隐藏”的 N 的离解和再组装构成了完整的催化循环。前线轨道分析表明，N 键三重键的断裂主要由来自 2 个金属中心的 d 电子向 N 的反键 π*-轨道的捐赠以及 N 的成键 π-和 σ-轨道中的电子向金属的空 d 轨道的同时迁移来控制。这项工作可能有助于合理设计催化剂，以减少人工氮活化仍然需要的巨大能量需求。
