Regioselective formation of fluorinated metallacycles from fluoroalkenes and an electron-rich Ni(0) difluorocarbene

Abstract

The reactivity of an electron-rich Ni-difluorocarbene complex, Ni=CF2(dppe)[P(OMe)3] (1), with a variety of fluorinated alkenes was investigated (dppe = 1,2-bis(diphenylphosphino)ethane). Reactions of 1 with perfluoro(methyl vinyl ether) and chlorotrifluoroethylene (CTFE) give regiospecific formation of metallacyclobutanes, in which the carbene C attacks the most electron-rich carbon of the fluoroalkene. Further reaction of the CTFE-derived metallacycle in the presence of tetrahydrofuran affords a single isomer of NiCl(σ-CF2CF=CFH) (dppe), 8, proposed to be formed by Ni-mediated Cα-Cl activation followed by hydride abstraction and loss of HF. Although 1 also undergoes a cyclization reaction with trifluoroethylene (TrFE), instability of the presumed nickelacyclobutane affords the C3 fluoroalkene, F2C=CH(CF3), and subsequent formation of isomeric metallacyclopentanes from two additional TrFEs. Alternatively, reaction of 1 with hexafluoropropene forms an unexpected Ni–CF3 σ-perfluoroallyl complex.