Activation of Perfluoro(methyl vinyl ether) at Rh(I) Complexes: Metal-Centered Versus Phosphine-Mediated Decarbonylation

Abstract

This study investigates the reactivity of perfluoro(methyl vinyl ether) [PMVE, CF₂=CF(OCF₃)] towards rhodium(I) phosphine complexes. The reaction pathways are characterized by C-O and C-F bond cleavage reactions and decarbonylation steps. On using the complex [Rh(H)(PEt₃)₃] (1), unprecedented reactivity pathways were observed that distinguish of those found for previously studied fluoroolefins. Reactivity of an excess PMVE at Rh is initiated by coordination to the Rh center in 1, followed by its insertion into the Rh-H bond and a b-OCF₃ elimination. This process ultimately results in OCF₃ ligand transformation to give trans-[Rh(F)(CO)(PEt₃)₃] (4) and Et₃PF₂. Reactions of stoichiometric amounts of PMVE with [Rh(H)(PEt₃)₃] (1) or excess amount of it with [Rh(F)(PEt₃)₃] (6) led to olefin complex formation to yield trans-[Rh(F)(η²-CF₂CFH)(PEt₃)₂] (7) and trans-[Rh(F)(CF(OCF₃)CF₂)(PEt₃)₂] (8), respectively. In contrast, a remarkable insertion into the Rh-F bond at [Rh(F)(CO)(PEt₃)₂] (4) was observed leading to the formation of trans-[Rh(CO)(CF(OCF₃)CF₃)(PEt₃)₂] (5). Decarbonylation of PMVE proceeds not only at Rh, but also via a metal-free, phosphine-mediated process. The latter is characterized by oxidative addition of PMVE at PEt₃ to form the fluorophosphoranes E/Z-(F₃CO)CF=CF(PFEt₃), which subsequently convert into Et₃PF₂, CO and presumably tetrafluoroethene.