Silica-immobilized N,O-prolinate ruthenium benzylidene complexes for catalytic applications

The immobilization of N,O-prolinate ruthenium benzylidene complexes as hybrid silicas is reported according to three routes: (i) co-condensation of a silylated precursor, 10, with TEOS via the sol–gel process (material M1); (ii) grafting of the same precursor on a preformed mesoporous silica M2 (material M3); entrapment of a parent non-silylated compound, 8, in the preformed mesoporous silica M2 (material M4). They have been characterized by several techniques. Solid state ²⁹Si NMR measurements ensure the anchorage of the Ru-complexed prolinate fragment in the silica matrix of M1 and M3 by the presence of T and Q sites, while only Q sites are observed as expected for M4. Elemental analyses provide the N/Si ratios and TGA experiments give the weight loss of the organics during decomposition and hence indicating the amount of organics inserted in the materials. Adsorption–desorption analyses show that these solids had surface areas ranging from 310 to 620 m²g⁻¹.These materials were tested as solid catalysts for two different reactions: ring-closing olefin metathesis and hydrosilylation of phenylacetylene with HSiEt₃. Their recyclability has also been investigated. While M1 is the less active for the first reaction giving low conversions and selectivity compared to M3 and M4, it is by far the most efficient catalyst for the second reaction.