Metal-organic layers as reusable solid fluorination reagents and heterogeneous catalysts for aromatic fluorination

Abstract

Reusable solid fluorination reagents and heterogeneous catalysts are ideally suited for late-stage fluorination with fast and clean conversion and simplified work-up. Here we report Pd-functionalized two-dimensional metal-organic layers (MOLs) as solid reagents and heterogeneous catalysts to efficiently fluorinate a broad scope of aromatic compounds. Site isolation in the MOLs provides a unique opportunity to stabilize highly active F-containing species for the chemical conversion. A terpyridine (TPY)- based ligand on the MOL, together with a 2-chloro-1,10-phenanthroline (phenCl) as a co-ligand, chelates PdII to form a reactive center. After treatment with Selectfluor/H2O, an (N-fluoroxy)-(2-chloro)-phenanthrolinium [N-(FO)-phenCl+] moiety is produced from the co-ligand on the Pd center. This active species serves as a stochiometric solid fluorination reagent, which shows different regioselectivities and reactivities as compared to homogeneous catalysts that involves PdIII/IV-F intermediates in catalytic cycles. The MOLs can also be used as heterogeneous catalysts for fluorination using Selectfluor. This work highlights opportunities in using MOLs to stabilize unique active sites for late-stage fluorination.