Brønsted acid-promoted C–F bond activation in [P,S]-ligated neutral and anionic perfluoronickelacyclopentanes

Abstract

Treatment of L₂Ni(CF₂)₄4a–c (L = PPh₃, PPh₂Me, pyridine) with an external Lewis acid (trimethylsilyl triflate) gives new L-functionalized fluoronickelacyclopentanes 5a–c. Complexes L₂Ni(CF₂)₄4a,b react with the thiol form of the bidentate ligand 1,2,4-(HS)(Ph₂P)Me(C₆H₃) [P,SH] through a unique Brønsted acid-promoted C_α–F bond activation mechanism, affording phosphine-functionalized nickelacycles bearing a phosphinothiolate ligand 6a–b. Furthermore, substituting monodentate ligands in L₂Ni(CF₂)₄4a–c with the deprotonated form of the bidentate ligand [P,S⁻] leads to the first anionic perfluoronickelacycle 7. The anionic metallacyle reacts with phosphonium salts [PHPh₃](Br) and [PHPh₂Me](Br) to yield HF and phosphine-functionalized nickelacycles 6a,b that still contain the terminal thiolate moiety.