A Well-Defined, Silica-Supported Tungsten Imido Alkylidene Olefin Metathesis Catalyst

The reaction of W( NAr)( CH t Bu)(CH 2 t Bu) 2 ( 1; Ar = 2,6- i PrC 6 H 3 ) with a silica partially dehydroxylated at 700 °C, SiO 2 - (700), gives syn- (⋮SiO)W( NAr)( CH t Bu)(CH 2 t Bu) ( 2 ) as a major surface species, which was fully characterized by mass balance analysis, IR, NMR, EXAFS, and DFT periodic calculations. Similarly, complex 1 reacts with ( c -C 5 H 9 ) 7 Si 7 O 12 SiOH to give (SiO)W( NAr)( CH t Bu)(CH 2 t Bu) ( 2m ), which shows similar spectroscopic properties. Surface complex 2 is a highly active propene metathesis catalyst, which can achieve a TON of 16 000 within 100 h, with only a slow deactivation.