Sergentu Dumitru-Claudiu, Gendron Frédéric, Autschbach Jochen
Department of Chemistry , University at Buffalo , State University of New York , Buffalo , NY 14260-3000 , USA . Email:
Chem Sci. 2018 Jun 11;9(29):6292-6306. doi: 10.1039/c7sc05373h. eCollection 2018 Aug 7.
U(CH) is a fascinating 5f complex whose metal-ligand bonding was assigned in the literature as being very similar to 3d cobaltocene, based on a crystal-field theoretical interpretation of the experimental magnetic resonance data. The present work provides an in-depth theoretical study of the electronic structure, bonding, and magnetic properties of the 5f U(CH) 3d metallocenes with V, Co, and Ni, performed with relativistic wavefunction and density functional methods. The ligand to metal donation bonding in U(CH) is strong and in fact similar to that in vanadocene, in the sense that the highest occupied arene orbitals donate electron density into empty metal orbitals of the same symmetry with respect to the rotational axis (3d for V, 5f for U), but selectively with α spin (↑). For Co and Ni, the dative bonding from the ligands is β spin (↓) selective into partially filled 3d orbitals. In all systems, this spin delocalization triggers spin polarization in the arene σ bonding framework, causing proton spin densities opposite to those of the carbons. As a consequence, the proton spin densities and hyperfine coupling constants are negative for the Co and Ni complex, but positive for vanadocene. The of U(CH) is negative and similar to that of cobaltocene, but only because of the strong spin-orbit coupling in the actinocene, which causes to be opposite to the sign of the proton spin density. The study contributes to a better understanding of actinide 5f transition metal 3d covalency, and highlights potential pitfalls when interpreting experimental magnetic resonance data in terms of covalent bonding for actinide complexes.
U(CH)₃是一种迷人的5f配合物，基于对实验磁共振数据的晶体场理论解释，其金属 - 配体键合在文献中被认为与3d茂钴非常相似。本工作采用相对论波函数和密度泛函方法，对含V、Co和Ni的5f U(CH)₃ - 3d金属茂的电子结构、键合和磁性进行了深入的理论研究。U(CH)₃中配体到金属的给予键很强，实际上与茂钒中的键相似，即最高占据的芳烃轨道将电子密度给予相对于旋转轴具有相同对称性的空金属轨道（V为3d，U为5f），但选择性地为α自旋(↑)。对于Co和Ni，配体的配位键是β自旋(↓)选择性地进入部分填充的3d轨道。在所有体系中，这种自旋离域在芳烃σ键框架中引发自旋极化，导致质子自旋密度与碳的自旋密度相反。因此，Co和Ni配合物的质子自旋密度和超精细耦合常数为负，而茂钒的为正。U(CH)₃的[此处可能有缺失内容]为负，与茂钴的相似，但这仅仅是由于锕系金属茂中强烈的自旋 - 轨道耦合，这使得[此处可能有缺失内容]与质子自旋密度的符号相反。该研究有助于更好地理解锕系元素5f - 过渡金属3dcovalency（此处可能有拼写错误，推测为“共价性”），并突出了在根据锕系配合物的共价键合解释实验磁共振数据时潜在的陷阱。
