Heterogenization of Organometallic Molybdenum Complexes with Siloxane Functional Groups and their Catalytic Application

Abstract

Abstractη5‐CpMo(CO)3R complexes containing siloxane functional groups [(CH2)3Si(OMe)3 or (CH2)Si(OEt)3] attached to either the cyclopentadiene ligand or directly to Mo were grafted on the mesoporous materials MCM‐41 and MCM‐48 by reaction of the OR (R=Me, Et) moieties in the silane ligand and surface silanol groups (Si‐OH). For the sake of comparison mesoporous materials modified with silane groups were reacted with Na+[CpMo(CO)3]−. The XRD, N2 adsorption‐desorption, and TEM analyses provide strong evidence that the mesoporous structure of the supporting material retains its long‐range ordering throughout the grafting process, despite significant reductions in surface area, pore volume and pore size. The appearance of strong IR bands around 2016 and 1956 cm−1 on the grafted samples also shows that the η5‐CpMo(CO)3R complexes have been successfully grafted. Elemental analysis reveals that the grafted samples contain 0.3–3.5 wt % Mo. 29Si CP MAS‐NMR spectra give clear evidence for a reduction in the numbers of the Q3 and Q2 sites. The formation of new peaks around −49.8, −57.9, and −66.2 ppm (T1, T2, and T3) indicates esterification of silanol groups by the alkoxy groups of the silane ligand. Both the in situ and ex situ prepared samples show good catalytic activity for the epoxidation of cyclooctene.