近日，美国宾夕法尼亚大学Schelter, Eric J.课题组发现4f轨道共价性实现CeIV–环丙烯基配合物的单晶到单晶环开环异构化。该研究于2025年4月23日发表在《自然-化学》杂志上。

f元素化合物的金属-配体键合相互作用通常是高度极化的，只有轻微的共价性质。尽管已知5d/6d轨道在化学上可用于配位键，但最近的量子化学和光谱分析表明，某些金属-配体键中存在明显的4f/5f轨道。然而，通过严格的比较研究和机理研究，4f轨道共价性与不同的化学反应模式之间并没有令人信服的联系。

研究组描述了一系列MIV-环丙烯基配合物（M=Ti、Zr、Ce、Hf、Th），其中铈同系物表现出4f共价Ce=Cα相互作用，通过单晶到单晶的转变引起开环异构化反应。这些结果通过证明4f轨道共价性在四价d和f嵌段金属配合物同构系列中f元素配合物的反应性中的表达，为4f轨道的共价性提供了证据。它们还为研究分子化合物在固态化学转化中的轨道共价效应提供了新的方向。

附：英文原文

Title: 4f-orbital covalency enables a single-crystal-to-single-crystal ring-opening isomerization in a CeIV–cyclopropenyl complex

Author: Vincenzini, Brett D., Yu, Xiaojuan, Paloc, Sbastien, Smith, Patrick W., Gupta, Himanshu, Pandey, Pragati, Kent, Greggory T., Ordonez, Osvaldo, Keller, Taylor, Gau, Michael R., Bacon, Alexandra M., Minasian, Stefan G., Hayton, Trevor W., Autschbach, Jochen, Schelter, Eric J.

Issue&Volume: 2025-04-23

Abstract: Metal–ligand bonding interactions for f-element compounds are typically highly polarized with only minor covalent character. Whereas the 5d/6d orbitals are known to be chemically accessible for dative bonding, recent quantum chemical and spectroscopic analyses have indicated appreciable 4f/5f-orbital involvement in certain metal–ligand bonds. However, 4f-orbital covalency has not been compellingly linked to distinctive modes of chemical reactivity via rigorous comparative study and mechanistic investigation. Here a series of MIV–cyclopropenyl complexes (M=Ti, Zr, Ce, Hf, Th) are described, wherein the cerium congener exhibits a 4f-covalent Ce=Cα interaction, causing a ring-opening isomerization reaction through a single-crystal-to-single-crystal transformation. The results provide evidence for 4f-orbital covalency by demonstrating its expression in the reactivity of an f-element complex within an isostructural series of tetravalent d- and f-block metal complexes. They also provide new directions for the study of orbital covalency effects of molecular compounds in solid-state chemical transformations.

DOI: 10.1038/s41557-025-01791-2

Source: https://www.nature.com/articles/s41557-025-01791-2