南方科技大学Liu Leo Liu团队开发出一种电子构型为σ⁰π²的稳定铑配位卡宾。相关论文于2024年1月5日发表在《科学》杂志上。

在该研究中，课题组人员得到了一种基态构型为σ⁰π²的铑配位阳离子环二膦卡宾。核磁共振波谱研究表明，卡宾碳的化学位移低于百万分之-30.0。X射线晶体学显示为平面RhP₂C结构。量子化学计算合理化了σ-电子离域/供给和π-电子负超共轭，如何共同稳定了碳烯中心形式空的σ轨道和填满的π轨道。

与传统的卡宾对应物不同，该卡宾可以与路易斯碱和银盐进行合成转化，分别生成路易斯酸/碱加合物和银π配合物。它具有两亲性，也可与异氰化物反应生成酮胺。

据介绍，可分离的单重态碳烯普遍采用σ²π⁰电子态，使其成为σ给体和π受体。

附：英文原文

Title: A stable rhodium-coordinated carbene with a σ0π2 electronic configuration

Author: Chaopeng Hu, Xin-Feng Wang, Jiancheng Li, Xiao-Yong Chang, Liu Leo Liu

Issue&Volume: 2024-01-05

Abstract: Isolable singlet carbenes have universally adopted a σ2π0 electronic state, making them σ-donors and π-acceptors. We present a rhodium-coordinated, cationic cyclic diphosphinocarbene with a σ0π2 ground state configuration. Nuclear magnetic resonance spectroscopy studies show a carbene carbon chemical shift below 30.0 parts per million. X-ray crystallography reveals a planar RhP2C configuration. Quantum chemical calculations rationalize how σ-electron delocalization/donation and π-electron negative hyperconjugation together stabilize the formally vacant σ orbital and the filled π orbital at the carbene center. In contrast to traditional carbene counterparts this carbene can undergo synthetic transformations with both a Lewis base and a silver salt, producing a Lewis acid/base adduct and a silver π-complex, respectively. Exhibiting ambiphilic reactivity, it can also form a ketenimine through reaction with an isocyanide.

DOI: adk6533

Source: https://www.science.org/doi/10.1126/science.adk6533