Post-synthetic modification of crystal-like periodic mesoporous phenylene-silica with ferrocenyl groups

• 35% of phenylene groups in a periodic mesoporous organosilica (PMO) were aminated.
• Reaction of PMO-NH2 with acetylferrocene gave anchored ferrocenylimine moieties.
• The ferrocene-PMO hybrid was examined as a catalyst for the oxidation of styrene.

Amination of crystal-like 1,4-phenylene-bridged periodic mesoporous organosilica (Ph-PMO) was achieved with about 35% conversion of phenylene groups. Ferrocenylimine groups were subsequently anchored onto this material by condensation of acetylferrocene with amino groups. Elemental analysis indicated that about 15% of amino groups in PMO-NH2 were derivatized, resulting in an iron loading of 0.21 mmol g−1. Evidence for the presence of ferrocenylimine groups in the derivatized material (PMO-Fc) was obtained from 13C cross-polarization (CP) magic-angle spinning (MAS) NMR and FT-IR spectroscopies. PMO-Fc was further characterized by 29Si MAS NMR spectroscopy, powder X-ray diffraction (XRD), N2 adsorption–desorption, and thermogravimetric analysis (TGA). Powder XRD and N2 adsorption–desorption data for PMO-NH2 and PMO-Fc indicated that the mesoporous structure and molecular-scale periodicity in PMO-NH2 were largely retained upon treatment with acetylferrocene. The material PMO-Fc was examined as a catalyst for the oxidation of styrene at 55 °C using hydroperoxides as oxidants. The reaction products were benzaldehyde (major) and styrene oxide (minor), with the aldehyde being formed in yields of 25–27% at 24 h. Recycling experiments indicated that the material was susceptible to leaching of catalytically active species into the liquid phase due to the pronounced water sensitivity of the azomethine linkage.

Ferrocenylimine groups were anchored onto crystal-like 1,4-phenylene-bridged periodic mesoporous organosilica (Ph-PMO) by condensation of acetylferrocene with amino groups in aminated Ph-PMO (PMO-NH2). The ferrocene-PMO hybrid was characterized by various techniques in the solid state and examined as a catalyst for the oxidation of styrene using hydroperoxides as oxidants.Figure optionsDownload as PowerPoint slide