β-Cyclodextrin and permethylated β-cyclodextrin inclusion compounds of a cyclopentadienyl molybdenum tricarbonyl complex and their use as cyclooctene epoxidation catalyst precursors

Abstract

The complex CpMo(CO) 3CH 2CONH 2 was immobilized in plain β-cyclodextrin (β-CD) and permethylated β-CD (TRIMEB), and the resultant inclusion compounds were characterized in the solid-state by powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), 13C{ 1H} CP/MAS NMR spectroscopy and FTIR spectroscopy. The non-included tricarbonyl complex can be used directly as a precursor to an active (TOF ca. 250 mol mol Mo - 1 h - 1 ) and selective homogeneous catalyst for the epoxidation of cyclooctene. Under the reaction conditions, rapid oxidative decarbonylation of the complex by the oxidant tert-butyl hydroperoxide ( t-BuOOH) takes place to give the active Mo VI catalyst. The cyclodextrin inclusion compounds were also tested as pre-catalysts for homogeneous or heterogeneous cyclooctene epoxidation. With no additional co-solvent, the TRIMEB inclusion compound was soluble under the reaction conditions and gave rise to catalytic activity similar to that observed for the pure non-included complex. The β-CD adduct was insoluble and exhibited comparatively lower activity, but could be recycled without loss of activity. The catalytic behavior of the two inclusion compounds was also tested in the presence of the ethanol, n-hexane and 1,2-dichloroethane solvents, as well as in a biphasic system comprising water and n-hexane.