Silica-Supported Vanadium-oxo-alkylidene for Self-Metathesis of Propene

Olefin metathesis is a widely used catalytic process for the construction of C═C bonds. This study describes the grafting of [V(═CHSi(CH3)3)(═O)(OC(CF3)2Mes)(IMes)] (1) onto the surface of partially dehydroxylated silica using surface organometallic chemistry, yielding [(≡SiO)V(═CHSi(CH3)3)(═O)(IMes)] (V/SiO2). The surface species is fully characterized by infrared spectroscopy, elemental analysis, and solid-state NMR spectroscopy. In contrast to its molecular analogue, which shows minimal activity in ring-closing metathesis, V/SiO2 is a productive catalyst in this transformation with a maximum TON of 94 for the ring-closing of (H5C3)2N-Ts (Ts = p-tolylsulfonyl). We also demonstrate that V/SiO2 is an active catalyst for the self-metathesis of propene under flow conditions, achieving a TON of 930. This is the first report of a V-alkylidene being active for the self-metathesis of propene with activity being an order of magnitude greater than other V-based catalysts reported for the self-metathesis of olefins.