Stadler Benedek, Gorgas Nikolaus, Elliott Stuart J, Crimmin Mark R
Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, Imperial College London, Shepherds Bush, 82 Wood Lane, W12 0BZ, London, U.K.
Institute of Applied Synthetic Chemistry, Vienna University of Technology, Getreidemarkt 9, 1060, Vienna, Austria.
Angew Chem Int Ed Engl. 2024 Oct 14;63(42):e202408257. doi: 10.1002/anie.202408257. Epub 2024 Sep 12.
Ligand exchange processes at metal complexes underpin their reactivity and catalytic applications. While mechanisms of ligand exchange at single site complexes are well established, occurring through textbook associative, dissociative and interchange mechanisms, those involving heterometallic complexes are less well developed. Here we report the reactions of a well-defined Fe-Al dihydride complex with exogenous ligands (CO and CNR, R=Me, Bu, Xyl=2,6-MeCH). Based on DFT calculations we suggest that these reactions occur through a dyotropic rearrangement, this involves initial coordination of the exogenous ligand at Al followed by migration to Fe, with simultaneous migration of a hydride ligand from Fe to Al. Such processes are rare for heterometallic complexes. We study the bonding and mechanism of the dyotropic rearrangement through in-depth computational analysis (NBO, IBOs, CLMO analysis, QTAIM, NCIplot, IGMH), shedding new light on how the electronic structure of the heterometallic core responds to the migration of ligands between metal sites. The dyotropic rearrangement fundamentally changes the nature of the hydride ligands, exposing new nucleophilic reactivity as evidenced by insertion reactions with CO, isocyanates, as well as isocyanides.
金属配合物中的配体交换过程是其反应活性和催化应用的基础。虽然单中心配合物的配体交换机制已得到充分确立，通过教科书式的缔合、解离和交换机制发生，但涉及异金属配合物的机制则研究较少。在此，我们报道了一种明确的铁 - 铝二氢化物配合物与外源性配体（CO和CNR，R = Me、Bu、Xyl = 2,6 - Me₂C₆H₃）的反应。基于密度泛函理论（DFT）计算，我们认为这些反应通过双同型重排发生，这涉及外源性配体首先在铝上配位，随后迁移至铁，同时氢化物配体从铁迁移至铝。这种过程在异金属配合物中很少见。我们通过深入的计算分析（自然键轨道（NBO）、定域分子轨道（IBO）、定域分子轨道（CLMO）分析、量子拓扑原子分子理论（QTAIM）、非共价相互作用（NCI）绘图、内禀生长率方法（IGMH））研究双同型重排的键合和机制，为异金属核心的电子结构如何响应配体在金属位点之间的迁移提供了新的见解。双同型重排从根本上改变了氢化物配体的性质，通过与CO、异氰酸酯以及异腈的插入反应证明了新的亲核反应活性。
