Preparation and characterization of metallacalixarenes anchored to a mesoporous silica SBA-15 LP as potential catalysts

• Calixarene [[4H]-(OH)3(H)] was used as a spacer between the SBA-15 surface and grafted complexes.
• Al(iBu)3·(Et2O) was used as a linker between the SBA-15 surface and calixarene [[4H]-(OH)3(H)].
• Zr(∗CH2Ph)4 and W(CtBu(CH2tBu)3) complexes could react with the OH of grafted calixarene.
• Grafted Zr and W species were freed from interactions with the support.

The calixarene [[4H]-(OH)3(H)] was used as a linker between a mesoporous silica SBA-15 LP (large pore) modified with Al(iBu)3·(Et2O) and organometallic complexes Zr(∗CH2Ph)4 or W(CtBu(CH2tBu)3) to avoid steric and electronic interactions of the metallic centers with the oxide surface, and insure a better controlled coordination sphere. Hence, materials M1, [(SiO)2AliBu·(Et2O), Si-iBu]SBA-15 LP-(700) and M2, [(SiO)2Al-[O-[4H]-(OH)2(H)], Si-iBu]SBA-15 LP-(700) were successively prepared by reaction of Al(i-Bu)3·(Et2O) with the OH groups of SBA-15 LP treated at 700 °C under vacuum, then with the calixarene [[4H]-(OH)3(H)] at 25 °C with a yield of 70%. M2 could then react with Zr(∗CH2Ph)4 at 25 °C and W(CtBu(CH2tBu)3) at 65 °C to form the corresponding bipodal surface complexes on materials M3, [(SiO)2Al-[O-[4H]-(H)(O)2Zr(∗CH2Ph)2], Si-iBu]SBA-15 LP-(700) and M4, [(SiO)2Al-[O-[4H]-(H)(O)2W(CtBu(CH2tBu))], Si-iBu]SBA-15 LP-(700) respectively. M4 proved to catalyze the propene metathesis with a high initial activity.

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