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(AlOC6X4OH)(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(AlOC6X4O-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.