Wan Qingyun, Yang Jun, To Wai-Pong, Che Chi-Ming
State Key Laboratory of Synthetic Chemistry, Department of Chemistry, The University of Hong Kong, Hong Kong SAR 999077, China;
State Key Laboratory of Synthetic Chemistry, Department of Chemistry, The University of Hong Kong, Hong Kong SAR 999077, China.
Proc Natl Acad Sci U S A. 2021 Jan 5;118(1). doi: 10.1073/pnas.2019265118.
Metallophilicity is defined as the interaction among closed-shell metal centers, the origin of which remains controversial, particularly for the roles of spd orbital hybridization (mixing of the spd atomic orbitals of the metal atom in the molecular orbitals of metal complex) and the relativistic effect. Our studies reveal that at close M-M' distances in the X-ray crystal structures of d and d organometallic complexes, M-M' closed-shell interactions are repulsive in nature due to strong M-M' Pauli repulsion. The relativistic effect facilitates (n + 1)s-nd and (n + 1)p-nd orbital hybridization of the metal atom, where (n + 1)s-nd hybridization induces strong M-M' Pauli repulsion and repulsive M-M' orbital interaction, and (n + 1)p-nd hybridization suppresses M-M' Pauli repulsion. This model is validated by both DFT (density functional theory) and high-level coupled-cluster singles and doubles with perturbative triples computations and is used to account for the fact that the intermolecular or intramolecular Ag-Ag' distance is shorter than the Au-Au' distance, where a weaker Ag-Ag' Pauli repulsion plays an important role. The experimental studies verify the importance of ligands in intermolecular interactions. Although the M-M' interaction is repulsive in nature, the linear coordination geometry of the d metal complex suppresses the L-L' (ligand-ligand) Pauli repulsion while retaining the strength of the attractive L-L' dispersion, leading to a close unsupported M-M' distance that is shorter than the sum of the van der Waals radius (r) of the metal atoms.
亲金属性被定义为闭壳层金属中心之间的相互作用，其起源仍存在争议，特别是对于spd轨道杂化（金属原子的spd原子轨道在金属配合物分子轨道中的混合）和相对论效应所起的作用。我们的研究表明，在d和d有机金属配合物的X射线晶体结构中，当M-M'距离很近时，由于强烈的M-M'泡利排斥作用，M-M'闭壳层相互作用本质上是排斥性的。相对论效应促进了金属原子的(n + 1)s-nd和(n + 1)p-nd轨道杂化，其中(n + 1)s-nd杂化会引发强烈的M-M'泡利排斥和排斥性的M-M'轨道相互作用，而(n + 1)p-nd杂化则会抑制M-M'泡利排斥。该模型通过密度泛函理论（DFT）以及高水平的耦合簇单双激发并微扰三重激发计算得到了验证，并用于解释分子间或分子内Ag-Ag'距离比Au-Au'距离短这一事实，其中较弱的Ag-Ag'泡利排斥起到了重要作用。实验研究证实了配体在分子间相互作用中的重要性。尽管M-M'相互作用本质上是排斥性的，但d金属配合物的线性配位几何结构在保留吸引性L-L'色散强度的同时，抑制了L-L'（配体-配体）泡利排斥，从而导致未配位的M-M'近距离比金属原子范德华半径（r）之和还要短。
