Max-Planck-Institut für Kohlenforschung, 45470 Mülheim/Ruhr, Germany.
Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 1-5, 8093 Zürich, Switzerland.
J Am Chem Soc. 2020 Jun 24;142(25):11279-11294. doi: 10.1021/jacs.0c04742. Epub 2020 Jun 9.
A new family of structurally well-defined molybdenum alkylidyne catalysts for alkyne metathesis, which is distinguished by a tripodal trisilanolate ligand architecture, is presented. Complexes of type combine the virtues of previous generations of silanolate-based catalysts with a significantly improved functional group tolerance. They are easy to prepare on scale; the modularity of the ligand synthesis allows the steric and electronic properties to be fine-tuned and hence the application profile of the catalysts to be optimized. This opportunity is manifested in the development of catalyst , which is as reactive as the best ancestors but exhibits an unrivaled scope. The new catalysts work well in the presence of unprotected alcohols and various other protic groups. The chelate effect entails even a certain stability toward water, which marks a big leap forward in metal alkylidyne chemistry in general. At the same time, they tolerate many donor sites, including basic nitrogen and numerous heterocycles. This aspect is substantiated by applications to polyfunctional (natural) products. A combined spectroscopic, crystallographic, and computational study provides insights into structure and electronic character of complexes of type . Particularly informative are a density functional theory (DFT)-based chemical shift tensor analysis of the alkylidyne carbon atom and Mo NMR spectroscopy; this analytical tool had been rarely used in organometallic chemistry before but turns out to be a sensitive probe that deserves more attention. The data show that the podand ligands render a Mo-alkylidyne a priori more electrophilic than analogous monodentate triarylsilanols; proper ligand tuning, however, allows the Lewis acidity as well as the steric demand about the central atom to be adjusted to the point that excellent performance of the catalyst is ensured.
一种新的结构明确的钼烷基炔烃催化剂家族,用于炔烃复分解反应,其特点是具有三足三硅醇配体结构。 型配合物结合了以前几代硅醇盐基催化剂的优点,具有显著提高的官能团耐受性。 它们易于大规模制备; 配体合成的模块化允许微调立体和电子性质,从而优化催化剂的应用范围。 这种机会体现在催化剂 的开发中,它与最好的前体一样反应活性,但具有无与伦比的范围。 新的催化剂在存在未保护的醇和各种其他质子基团的情况下效果很好。 螯合效应甚至使它们对水具有一定的稳定性,这标志着金属烷基炔烃化学的总体上的一个重大飞跃。 同时,它们可以容忍许多供体位点,包括碱性氮和许多杂环。 通过对多功能(天然)产物的应用证明了这一点。 综合光谱、晶体学和计算研究提供了对 型配合物结构和电子性质的深入了解。 特别有启发性的是基于密度泛函理论(DFT)的炔碳原子和 Mo NMR 光谱的化学位移张量分析; 这种分析工具以前在有机金属化学中很少使用,但事实证明它是一种灵敏的探针,值得更多关注。 数据表明,与类似的单齿三芳基硅醇相比,三足配体使 Mo-烷基炔烃具有先验的更高亲电性; 然而,适当的配体调谐可以调整中心原子的路易斯酸度和空间需求,从而确保催化剂具有出色的性能。