School of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
Department of Chemistry, COMSATS Institute of Information Technology, Abbottabad, 22060, Abbottabad, Pakistan.
Nat Commun. 2019 Feb 7;10(1):634. doi: 10.1038/s41467-019-08553-y.
FEUDAL (f's essentially unaffected, d's accommodate ligands) is a longstanding bonding model in actinide chemistry, in which metal-ligand binding uses 6d-orbitals, with the 5f remaining non-bonding. The inverse-trans-influence (ITI) is a case where the model may break down, and it has been suggested that ionic and covalent effects work synergistically in the ITI. Here, we report an experimentally grounded computational study that quantitatively explores the ITI, and in particular the structure-directing role of f-orbital covalency. Strong donor ligands generate a cis-ligand-directing electrostatic potential (ESP) at the metal centre. When f-orbital participation, via overlap-driven covalency, becomes dominant via short actinide-element distances, this ionic ESP effect is overcome, favouring a trans-ligand-directed geometry. This study contradicts the accepted ITI paradigm in that here ionic and covalent effects work against each other, and suggests a clearly non-FEUDAL, structure-directing role for the f-orbitals.
FEUDAL（f 的基本不受影响，d 的适应配体）是锕系元素化学中一种长期存在的键合模型，其中金属-配体结合使用 6d 轨道，而 5f 轨道保持非键合状态。反式影响（ITI）是模型可能失效的情况，有人提出离子和共价效应对 ITI 具有协同作用。在这里，我们报告了一项基于实验的计算研究，该研究定量探索了 ITI，特别是 f 轨道共价性的结构导向作用。强给体配体在金属中心产生顺式配体导向静电势（ESP）。当 f 轨道通过重叠驱动的共价性参与通过短的锕系元素距离变得占主导地位时，这种离子 ESP 效应被克服，有利于反式配体导向的几何形状。这项研究与公认的 ITI 范式相矛盾，因为这里离子和共价效应相互作用，并且表明 f 轨道具有明显的非 FEUDAL 结构导向作用。
