苏州大学谌宁团队报道了ThCTi@Cs(6)-C82——混合锕系过渡金属团簇中的Th═C双键。相关研究成果于2025年1月15日发表于国际一流学术期刊《美国化学会杂志》。

长期以来，在研究锕系配体多重键作为合成靶时，人们一直在寻找与理论共价双键半径之和相对应的钍-碳双键。然而，迄今为止，这种化学键的稳定仍然是一个巨大的挑战，部分原因是钍的5f-/6d轨道与碳的2s-/2p-前沿轨道之间的能量匹配相对较差。

该文中，研究人员报告了在碳桥锕系过渡金属簇中成功合成钍-碳双键，即[Th═C║Ti]，封装在C82的富勒烯笼中。ThCTi@Cs(6)-C82是通过改进的电弧放电方法成功合成的，并通过质谱、单晶X射线晶体学、各种光谱和理论计算进行了表征。X射线晶体学分析揭示了一个弯曲的μ₂脊碳化物团簇，Th-C键距离为2.123（18 ）Å，这是迄今为止在可分离化合物中报告的最短距离，与共价Th═C双键半径之和（2.10 Å）相当。

此外，ThC═Ti具有出乎意料的非线性结构，键角为133.0（10）°。综合实验和理论研究进一步揭示了Th═C的键合性质，Th║C向桥接碳极化，但共价性明显高于之前报道的有机金属化合物的Th–C键。此外，明显的笼状金属贡献似乎正在稳定包封的Th═C║Ti团簇。

该项工作加深了对钍键合行为的理解，并展示了富勒烯笼稳定含有不同类型金属-配体多重键的，键合基序的独特能力。

附：英文原文

Title: ThCTi@Cs(6)-C82: Th═C Double Bond in a Mixed Actinide-Transition Metal Cluster

Author: Zhengkai Cao, Xiaojuan Yu, Yang-Rong Yao, Jochen Autschbach, Ning Chen

Issue&Volume: January 15, 2025

Abstract: A thorium–carbon double bond that corresponds to the sum of theoretical covalent double bond radii has long been sought after in the study of actinide-ligand multiple bonding as a synthetic target. However, the stabilization of this chemical bond remains a great challenge to date, in part because of a relatively poor energetic matching between 5f-/6d- orbitals of thorium and the 2s-/2p- frontier orbitals of carbon. Herein, we report the successful synthesis of a thorium–carbon double bond in a carbon-bridged actinide-transition metal cluster, i.e., [Th═C═Ti], encapsulated inside a fullerene cage of C82. ThCTi@Cs(6)-C82 was successfully synthesized by a modified arc discharging method and characterized by mass spectrometry, single-crystal X-ray crystallography, various spectroscopy, and theoretical calculations. X-ray crystallographic analysis reveals a bent μ2-bridged carbide cluster with a Th–C distance of 2.123(18) , which is the shortest reported to date in an isolable compound and is comparable to the sum of the covalent Th═C double bond radii (2.10 ). In addition, Th═C═Ti takes an unexpected nonlinear configuration with a bond angle of 133.0(10)°. The combined experimental and theoretical investigation further revealed the bonding nature of Th═C, which is polarized toward the bridged carbon but has a notably higher covalency than the Th–C bonds reported previously for organometallic compounds. Moreover, pronounced cage-to-metal donation appears to be stabilizing the encapsulated Th═C═Ti cluster. This work offers a deeper understanding of the bonding behavior of thorium and features the unique ability of fullerene cages to stabilize bonding motifs containing different types of metal–ligand multiple bonds.

DOI: 10.1021/jacs.4c15253

Source: https://pubs.acs.org/doi/abs/10.1021/jacs.4c15253