Synthesis and characterization of CpMo(CO)3(CH2–pC6H4–CO2CH3) and its inclusion compounds with methylated cyclodextrins. Applications in olefin epoxidation catalysis

Abstract

The cyclopentadienyl molybdenum tricarbonyl complex CpMo(CO)3(CH2–pC6H4–CO2CH3) (1) (Cp = η5-C5H5) and its 1:1 inclusion complexes with heptakis(2,6-di-O-methyl)-β-cyclodextrin (1@DIMEB) and heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin (1@TRIMEB) were prepared and characterized by elemental and thermogravimetric analyses, powder X-ray diffraction, NMR, FT-IR and Raman spectroscopy. All three compounds were investigated as catalyst precursors for olefin epoxidation using cis-cyclooctene (Cy) as a model substrate, a reaction temperature of 55 °C, and different types of oxidants (tert-butylhydroperoxide in decane (TBHPdec) or in water (TBHPaq), and aqueous hydrogen peroxide). With the aim of facilitating recycling of the homogeneous catalytic systems, different solvent mixtures were tested: biphasic liquid–liquid solvent systems [(water, glycerol, ionic liquid)–(n-hexane, α,α,α-trifluorotoluene (TFT), iso-butyl methyl ketone)], and in some cases no cosolvent was added. Excellent epoxide selectivity (100%) was observed for all tested catalytic systems. An example of an interesting catalytic system is that of 1@TRIMEB/TBHPaq/TFT/H2O since the catalyst can be easily separated in the form of an aqueous solution, by decantation, from the organic phase containing the reaction products and recycled.