Synthesis and characterisation of titanium silasesquioxane complexes: soluble models for the active site in titanium silicate epoxidation catalysts †

Ti-bridged silsesquioxanes as precursors of silica-supported titanium oxide catalysts for the epoxidation of cyclooctene

“…Other Ti-containing POSS, 1b and 2 (see Scheme 2), showed similar activities (entries 3 and 4). The activities of Ti-containing POSS as homogeneous catalysts for the epoxidation by organic peroxides have been previously reported [16][17][18][19][20][21][22][23]. Silica-tethered 1a showed a catalytic activity similar to that of 1a, indicating that 1a was tethered without a loss of activity (entry 5).…”

“…In particular, the catalytic activities of Ti-containing POSS for the epoxidation of alkenes have been examined [16][17][18][19][20][21][22][23]. In addition to their activities as homogeneous catalysts, their application to heterogeneous catalysis using metal-containing POSS as precursors has been examined [10,13,15,[24][25][26][27][28][29][30][31].…”

Grafting of [Mn(CH2tBu)2(tmeda)] on Silica and Comparison with Its Reaction with a Silsesquioxane

“…Physical techniques, such as EXAFS, and solid-state NMR and IR spectroscopy are useful for addressing the coordination geometry and structure of the grafted compounds. An additional strategy has been to compare the physical and chemical properties (vibrational frequencies, [2][3][4] NMR chemical shifts [5,6] and elementary steps involved in the grafting reaction of the organometallic precursor on a surface) [5] of the grafted compounds with those of simpler model compounds [7][8][9][10][11][12] that are obtained by homogeneous methodologies.…”

“…(2 a; tmeda = tetramethylethylendiamine), while a mixture of 2 a and [(SiO) 2 Mn-(tmeda)] (2 b) is obtained by using SiO 2/200 , SiO 2/300 , or SiO 2/500 as evidenced by mass balance analysis, and IR and EPR spectroscopy. The reaction of 1 and (c-C 5 H 9 ) 7 2 ], in a quantitative yield; compound 4 was characterized by single-crystal X-ray diffraction.…”

Molybdenum containing surface complex for olefin epoxidation

“…Surface Organo-Metallic Chemistry (SOMC) can provide in principle an opportunity to construct a uniform distribution of active sites on the surface of the support, and thus help in getting the required structure/activity relationship. 8 This approach has already been used to study, understand and improve the Shell catalyst, 9 and also to design an efficient heterogeneous Sharpless epoxidation catalyst. 10 A crucial point in generating a well-defined system is to use a monomeric precusor and try to graft it via one or several covalent bonds.…”