近日，中国科学院大连化学物理研究所叶生发团队研究了Cr（I）双氮配合物的三硅烷化反应。相关论文于2025年8月25日发表在《美国化学会志》上。

二氮（N₂）固定化学长期追求的目标是直接由N₂合成含氮化学物质。迄今为止，过渡金属二氮配合物的配体亲电攻击是构建氮元素键最直接的途径。虽然单二氮配合物的亲电官能化已经得到了充分的证明，但对于那些含有多个N₂基团的配合物，类似的反应总是导致N₂的萃取，最多只能衍生出一个N₂。

研究组描述了一个单核形式铬(I)由PCP钳形配体支撑的双二氮配合物。具体而言，用TMSCl（TMS=SiMe₃）处理会导致其两个N₂配体的甲硅烷基化，并在从Cr（II）双二叠氮基中间体开始的过程中，与1:1比例的Cr（IV）一酰肼物种一起，干净地形成带有二叠氮和肼基单元的Cr（Ⅳ）络合物。这是首次在一个金属中心上实现两个N₂配体的功能化。

相比之下，以TMSOTf代替TMSCl作为亲电试剂的反应产生了Cr（III）腙配合物。在详细分析三硅基化反应电子结构演化的基础上，采用基于高度相关波函数的从头算方法，确定了两种N₂配体官能化的必要条件，即双二氮配合物必须具有非竞争性的8电子M-(N₂)₂ π反给体。研究组讨论了为了满足这一要求，如何设计合适的二氮配合物来实现这一具有挑战性的转变。

附：英文原文

Title: Trisilylation of a Formal Cr(I) Bis-dinitrogen Complex

Author: Botao Wu, Wang Chen, Haihan Yan, Xinchao Zhang, Junnian Wei, Zhenfeng Xi, Gao-Xiang Wang, Shengfa Ye

Issue&Volume: August 25, 2025

Abstract: The long-sought goal of dinitrogen (N2) fixation chemistry is to effect facile synthesis of nitrogen-containing chemicals directly from N2. To date, electrophilic attack of coordinated N2 ligands of transition metal dinitrogen complexes represents the most straightforward route to construct nitrogen-element bonds. Although electrophilic functionalization of monodinitrogen complexes to furnish diazenido and hydrazido species has been well-documented, for those complexes containing multiple N2 moieties, analogous reactions invariably lead to N2 extrusion and at most one N2 can be derivatized. Herein, we describe electrophilic functionalization of a mononuclear formal chromium(I) bis-dinitrogen complex supported by a PCP-pincer ligand. Specifically, treatment with TMSCl (TMS = SiMe3) results in silylation of its two N2 ligands and clean formation of a Cr(IV) complex bearing a diazenido and a hydrazido unit en route from a Cr(II) bis-diazenido intermediate, alongside a Cr(IV) monohydrazido species in a 1:1 ratio. This is the first time that functionalization of two N2 ligands on a single metal center has been realized. In contrast, the reaction using TMSOTf instead of TMSCl as the electrophile generates a Cr(III) hydrazido complex. On the basis of detailed analyses of the electronic structure evolution during the trisilylation reaction using highly correlated wave function-based ab initio approaches, we identify a necessary condition for functionalization of two N2 ligands, viz., bis-dinitrogen complexes ought to feature noncompetitive eight-electron M-(N2)2 π-backdonation. To satisfy this requirement, how to design appropriate dinitrogen complexes to effect this challenging transformation is discussed.

DOI: 10.1021/jacs.5c05591

Source: https://pubs.acs.org/doi/abs/10.1021/jacs.5c05591