1. Regioselective formation of fluorinated metallacycles from fluoroalkenes and an electron-rich Ni(0) difluorocarbene
- Author
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Rochon, Alexandra, Elsby, Matthew R., and R.Baker, Tom
- Subjects
Olefins -- Chemical properties ,Carbenes -- Chemical properties ,Fluorine compounds -- Chemical properties ,Nickel compounds -- Chemical properties ,Chemistry - Abstract
The reactivity of an electron-rich Ni-difluorocarbene complex, Ni=[CF.sub.2][(dppe)[P(OMe).sub.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(r-[CF.sub.2]CF=CFH) (dppe), 8, proposed to be formed by Ni-mediated [C.sub.a]-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, [F.sub.2]C=CH([CF.sub.3]), and subsequent formation of isomeric metallacyclopentanes from two additional TrFEs. Alternatively, reaction of 1 with hexafluoropropene forms an unexpected Ni--[CF.sub.3] r-perfluoroallyl complex. Key words: nickel difluorocarbene, fluoroalkene, cycloaddition, C--F bond activation. La reactivite d'un complexe de difluorocarbene-nickel riche en electrons, le Ni-[CF.sub.2](dppe)[P(OMe)] (1), avec une variete d'alcenes fluores a ete etudiee [dppe = 1,2-bis(diphenylphosphino)ethane]. Les reactions du complexe 1 avec le perfluoro(methylvinylether) et le chlorotrifluoroethylene (CTFE) donnent lieu a la formation regiospecifique de metallacyclobutanes, dans lesquels le C du carbene attaque le carbone le plus riche en electrons du fluoroalcene. La poursuite de la reaction du metallacycle derive du CTFE en presence de tetrahydrofurane produit un seul isomere de NiCl([sCF.sub.2]CF=CFH) (dppe), le complexe 8, dont la formation pourrait etre attribuable a l'activation de la liaison [C.sub.a]Cl catalysee par le Ni, suivie de l'abstraction de l'hydrure et de la perte d'une molecule de HF. Bien que le complexe 1 subisse egalement une reaction de cyclisation avec le trifluoroethylene (TrFE), l'instabilite du suppose nickelacyclobutane permettrait la formation du fluoroalcene en C3, le [F.sub.2]C=CH([CF.sub.3]), puis la formation subsequente de metallacyclopentanes isomeriques provenant de deux autres molecules de TrFE. Sinon, la reaction du complexe 1 avec l'hexafluoropropene forme un complexe inattendu de [CF.sub.3]sperfluoroallylNi. [Traduit par la Redaction] Mots-cles : difluorocarbene-nickel, fluoroalcene, cycloaddition, activation de liaisons C--F., Introduction Reactions involving metal alkylidenes and carbenes are some of the most valuable and desired catalytic transformations. (1-4) Although the reactivity of metal carbenes has been thoroughly studied and established, [...]
- Published
- 2021
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