Decomposition of [γ-(SiO4)W10O28(OH)4]4- as a pathway to an active catalyst in peroxide based homogeneous epoxidations

INOR 697

Daniel Hillesheim, dhilles@emory.edu1, Yurii V. Geletti, iguelet@emory.edu2, Craig L. Hill, chill@emory.edu2, Keiji Morokuma, morokuma@emory.edu3, and Djamaladdin G. Musaev, musaev@euch4e.chem.emory.edu3. (1) Department of Chemistry, Emory University, 1515 Dickey Drive, Atlanta, GA 30322, (2) Department of Chemistry, Emory University, Atlanta, 1515 Dickey Drive, Atlanta, GA 30322, (3) Cherry L. Emerson Center for Scientific Computation and Department of Chemistry, Emory University, 1515 Dickey Drive, Atlanta, GA 30322
The selective, green, catalytic epoxidation of alkenes is highly desirable because epoxides are key for manufacture of resins, adhesives, coatings, and pharmaceutical intermediates. The organic solvent soluble tetra-n-butylammonium (TBA) salt of [γ-(SiO4)W10O28(OH)4]4- (1) was shown to be the precursor of an active species that catalyzes oxygen transfer from aqueous peroxide to olefins. Complex 1 is transformed under reaction conditions to a stable diperoxo species [γ-(SiO4)W10O28(O2)2]4- which has been isolated and shown to be catalytically inactive. As infrared spectroscopy was inconclusive in distinguishing the various POM species, UV-Visible spectroscopy was used to monitor changes in POM speciation. Based on kinetics and other experimental data, acid dependent “peroxydolysis” is believed to generate the active catalyst. A catalyst assembled in situ from monomeric components (TBA2WO4, HClO4, SiCl4) exhibits a similar rate but a slightly different epoxidation regioselectivity relative to 1.
 

Polyoxometalates and Related Clusters in Chemistry and Nanoscience
7:00 PM-10:00 PM, Tuesday, August 21, 2007 BCEC -- Exhibit Hall - B2, Poster

Division of Inorganic Chemistry

The 234th ACS National Meeting, Boston, MA, August 19-23, 2007