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(double bond; length as m-dashCHPh)(3-Br–C5H5N)(H2IMes) and Ru(C8H3F4O3)2XL, where X = C,N-(double bond; length as m-dashCHCH2CH2-2-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.