Modification of silica-supported tungsten neosilyl oxo precatalysts: impact of substituted phenol on activity and stability in olefin metathesis

Abstract

A novel strategy to access a large variety of tungsten oxo pre-catalysts for olefin metathesis involving post-treatment of [(SiO)W(O)(CH₂SiMe₃)₃], 1b, with the desired spectator ligands is presented. This method allowed establishing structure–reactivity relationships in propylene metathesis as a function of the spectator ligands of tungsten oxo species. Thus, the novel pre-catalysts [(SiO)W(O)R₂X], 2a–c (X = 2,6-dimethylphenoxide, 2-trifluoromethylphenoxide, pentafluorophenoxide), are obtained by modification of well-defined monopodal species 1b by substituted phenols along with TMS release. These were demonstrated by mass balance analysis, elemental analysis, IR, advanced solid-state NMR (1D and 2D ¹H, ¹³C and ¹⁹F) and EXAFS. The modified materials were proved to lead to stable and efficient supported tungsten oxo catalysts for propene metathesis under dynamic conditions at 80 °C.