近日，南方科技大学刘柳团队报道了一种中性σ⁰π²碳烯能通过σ-面途径活化氢。2026年5月11日，《自然-化学》杂志发表了这一成果。

基态σ⁰π²卡宾是探索最少、理解最浅的低价碳物种之一。已知可分离的σ⁰π²卡宾实例仍主要局限于阳离子化合物。

研究组报道了一种中性σ⁰π²卡宾——即具有平面RhP₂C环的铑二膦卡宾的合成。与传统σ⁰π²卡宾的小分子活化过程（通常遵循轨道对称性约束所决定的亲核驱动、π面进攻、非最小运动路径）形成鲜明对比，这种中性σ⁰π²卡宾在环境条件下通过σ面途径裂解H₂。

计算表明，该反应存在一个亲电驱动、卡宾骨架重排极小的早期过渡态，并通过协同但不同步的H-H键断裂形成两个C-H键。这些发现表明，稳定的卡宾能够通过σ面途径实现小分子活化，并深化了人们对低价碳化学中电子结构与反应活性之间关联的理解。

附：英文原文

Title: A neutral σ0π2 carbene enabling hydrogen activation via a σ-face pathway

Author: Fan, Fei, Nong, Haoxiang, Zhou, Miaomiao, Liu, Liu Leo

Issue&Volume: 2026-05-11

Abstract: Ground-state σ0π2 carbenes are among the least explored and least understood classes of low-valent carbon. Known examples of isolable σ0π2 carbenes remain largely limited to cationic compounds. Here we report the synthesis of a neutral σ0π2 carbene, namely a rhodadiphosphinocarbene featuring a planar RhP2C ring. In sharp contrast to small-molecule activation by conventional σ2π0 carbenes, which typically proceeds via nucleophilicity-driven, π-face, non-least-motion trajectories mandated by orbital-symmetry constraints, this neutral σ0π2 carbene cleaves H2 under ambient conditions via a σ-face pathway. Computations reveal an electrophilicity-driven early transition state characterized by minimal reorganization of the carbene framework and a concerted yet asynchronous H–H scission to form two C–H bonds. These findings show that a stable carbene can enable small-molecule activation through a σ-face pathway and deepen our understanding of electronic structure–reactivity correlations in low-valent carbon chemistry.

DOI: 10.1038/s41557-026-02147-0

Source: https://www.nature.com/articles/s41557-026-02147-0