C–F Bond Activation and C–H Bond Zincation of Fluoroarenes with Bis-Guanidinate Zinc Hydrides

We report C–F bond activation of pentafluoropyridine (C 5 F 5 N) using bis-guanidinate zinc hydride complexes under both uncatalyzed and palladium-catalyzed protocols. Treatment of pentafluoropyridine with the less sterically encumbered dimeric zinc complex ( Dep LZnH) 2 ( 1-H ) 2 (where L = {(ArHN)(ArN)–C═N–C═(NAr)(NHAr); Dep = Ar = 2,6-Et 2 -C 6 H 3 }) affords the corresponding dinuclear zinc fluoride ( Dep LZnF) 2 ( 1-F ) 2 . In contrast, the more sterically hindered monomeric analogue Dipp LZnH ( 2-H ) (Dipp = Ar = 2,6- i Pr 2 -C 6 H 3 ) remains unreactive under identical conditions; however, in the presence of a palladium catalyst, ( Dipp LZnF) 2 ( 2-F ) 2 is formed. Furthermore, ( 1-H ) 2 promotes catalyst-free C–H zincation of fluoroarenes, affording zinc aryl complexes ( 1-Ar 1 - 1-Ar 10 ) in moderate to excellent yields with high regioselectivity, while 2-H requires Pd catalysis to access analogous species ( 2-Ar 1 - 2-Ar 10 ). Selected organozinc complexes undergo Negishi cross-coupling to furnish biaryl products. β-Diketiminate (Nacnac)-supported zinc hydrides, ( Dep NacnacZnH) 2 and Dipp NacnacZnH [Nacnac = (ArNCMe) 2 CH], were also investigated. In both ligand systems, sterics govern C–F bond activation, while C–H zincation is influenced by steric effects, ligand basicity, metal Lewis acidity, and hydricity. Overall, bis-guanidinate-stabilized zinc hydrides exhibit superior reactivity compared to their Nacnac counterparts in uncatalyzed C–H zincation under identical conditions, establishing them as versatile reagents for the selective functionalization of fluoroarenes.