Dramatic improvements of well-defined silica supported mo-based olefin metathesis catalysts by tuning the N-containing ligands

Grafting [Mo(NAr)(CHCMe2R1)(NR2)(2)] on SiO2-(700) gives [(SiO)Mo(NAr)(CHCMe2R1)(NR2)] as a major surface species along with [(SiO)Mo(NAr)(CH2CMe2R1)(NR2)(2)] according to mass balance analysis, IR and NMR spectroscopies. The replacement of one amido group by a siloxy group from the surface of silica dramatically increased the activity of the Mo complex in olefin metathesis, and tuning the imido ligands allows the reactivity to be increased by at least one order of magnitude so that an overall turnover of 231 000 can be achieved in the metathesis of propene. Additionally, ethyl oleate can also be converted into a thermodynamic equilibrated mixture in 8 h with only 0.02% of catalyst.