C-H and C-F bond activation of fluorinated propenes at Rh: enabling cross-coupling reactions with outer-sphere C-C coupling.

The reaction of [Rh{()-CF[double bond, length as m-dash]CHCF}(PEt)] with Zn(CH) results in the methylation of the alkenyl ligand to give [Rh{(/)-C(CH)[double bond, length as m-dash]CHCF}(PEt)]. Variable temperature NMR studies allowed the identification of a heterobinuclear rhodium-zinc complex as an intermediate, for which the structure [Rh(CH)(ZnCH){()-C(CH)[double bond, length as m-dash]CHCF}(PEt)] is proposed. Based on these stoichiometric reactions, unique Negishi-type catalytic cross-coupling reactions of fluorinated propenes by consecutive C-H and C-F bond activation steps at room temperature were developed. The C-H bond activation steps provide a fluorinated ligand at Rh and deliver the fluorinated product, whereas the C-F bond activation and C-C coupling occur outer-sphere nucleophilic attack at the fluorinated alkenyl ligand.