Latent ruthenium initiators containing fluoro aryloxide ligands

A new ligand, methyl 2,3,5,6-tetrafluoro-4-oxybenzoate (C₈H₃F₄O₃), combining an electron withdrawing group (C₆F₄) to tune the reactivity with an anchor group (CO₂Me) for immobilization on supports, was used to prepare four new ruthenium initiators, viz. Ru(C₈H₃F₄O₃)₂(CHPh)(3-Br-C₅H₅N)(H₂IMes) and Ru(C₈H₃F₄O₃)₂XL, where X = C,N-(CHCH₂CH₂-2-C₅H₄N) and L = PⁱPr₃, PCy₃ or H₂IMes. The new ligand greatly reduced the reactivity of the ruthenium centre at room temperature. The ¹H NMR and DSC investigation for the ROMP of norbornene dicarboximide monomers clearly demonstrated that the Ru(C₈H₃F₄O₃)₂XL initiators were inactive at room temperature and required elevated temperatures for their activation.