Design and Application of a Hybrid Material Featuring Well-Defined, Tuneable Grafting Sites for Supported Catalysis

A new material based on amorphous silica, and featuring a well‐defined phenolic functionality was prepared in two simple steps by using commercially available, cheap reagents. Silica was first reacted with aluminum isobutyl etherate to yield an aluminum isobutyl site [(≡SiO)2Al(iBu)(Et2O)], which then selectively reacted with a hydroquinone spacer to yield [(≡SiO)2(AlOC6X4OH)(Et2O)] (X=H or F). This support material was then used to tether the organometallic tungstenocarbyne complex [W(≡CtBu)(CH2tBu)3] to yield the surface species [(≡SiO)2(AlOC6X4O‐W(≡CtBu)(CH2tBu)2(Et2O)] (X=H or F). Both H‐ and F‐containing species were fully characterized, and their activities in the self‐metathesis reaction of propene to ethylene and 2‐butenes were found to be two and three times higher, respectively, than the activity of the corresponding tungstenocarbyne complex directly grafted onto silica. To tether a tungsten: A hybrid material, featuring single‐site phenolic functionalities on a silica surface was developed and subsequently used to tether a tungstenocarbyne complex. Drastic improvements in terms of activity and stability in propene metathesis were observed with respect to the silica counterpart. Further tuning of the spacer moiety with fluorine atoms led to additional significant improvements in activity.