Apolinar Omar, Struijs Job J C, Sarkar Debotra, Gouverneur Véronique, Aldridge Simon
Chemistry Research Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QR, UK.
Angew Chem Int Ed Engl. 2025 Jan 10;64(2):e202414790. doi: 10.1002/anie.202414790. Epub 2024 Nov 9.
The major source of fluoride, namely calcium difluoride (CaF), is derived from the mineral fluorspar. Recent advances in the activation of CaF via mechanochemical methods have inspired investigation of the fundamental properties of Ca-F bonds in molecular complexes. However, the paucity of well-defined molecular Ca-F-containing complexes undermines systematic understanding of the factors governing nucleophilic fluoride delivery. Here we report the use of a multidentate bis(phenoxide) ligand based on a 1,4,7-triazacyclononane (TACN) scaffold for the formation of well-defined Ca-F complexes and demonstrate their capabilities in fluoride delivery. Key to this synthesis is a desymmetrization step carried out on the TACN ligand within the Ca coordination sphere. A series of stable anionic dinuclear calcium fluoride complexes has then been accessed and characterized by NMR spectroscopy (critically by F NMR) and X-ray crystallography. Nucleophilic fluoride delivery can be used to generate C-F, Si-F and S-F bonds, with a notable advance over amide-derived ligand scaffolds being the reduced extent of side reactions derived from competing attack on the electrophile by the less nucleophilic O-donor anionic ligand set.
氟化物的主要来源，即二氟化钙（CaF₂），源自矿物萤石。通过机械化学方法活化CaF₂的最新进展激发了对分子络合物中Ca - F键基本性质的研究。然而，定义明确的含分子Ca - F络合物的匮乏阻碍了对亲核氟传递控制因素的系统理解。在此，我们报告了使用基于1,4,7 - 三氮杂环壬烷（TACN）支架的多齿双（酚盐）配体来形成定义明确的Ca - F络合物，并展示了它们在氟传递方面的能力。该合成的关键是在Ca配位球内对TACN配体进行去对称化步骤。随后获得了一系列稳定的阴离子双核氟化钙络合物，并通过核磁共振光谱（特别是¹⁹F NMR）和X射线晶体学对其进行了表征。亲核氟传递可用于生成C - F、Si - F和S - F键，与酰胺衍生的配体支架相比，一个显著的进步是源自亲核性较弱的O供体阴离子配体对亲电试剂的竞争性攻击所产生的副反应程度降低。
