Molybdenum oxide anchored

The photoluminescence spectra of anchored molybdenum oxide/Si02 and molybdenum oxide/PVG catalyst recorded at 77 K decay as a single exponential, as evidenced by the straight line obtained in the logarithmic plots. The lifetime (i.e., t at 77 K) of the charge-transfer excited triplet state was determined to be 1.9 x 10 - s (33, 63, 126). 

PHOTOLlJMINnSCFNCr, ADSORPTION, AND (PIIOTO)CATALYSIS 195 2. Anchored Molybdenum Oxide... 

Fig. 26. Photoluminescence spectra of the molybdenum oxide catalyst anchored to Si02 (molybdenum oxide/Si02) at 77 K (a) and at 298 K (b) and their excitation spectrum. Excitation wavelength at 280 nm emission monitored at 520 nm [reproduced with permission from Anpo...

Immobilized complexes anchored to the surface of oxide supports may serve as active metathesis catalysts. In fact, Mo(CO)6 on alumina was reported in the first paper on metathesis by Banks and Bailey.1 Molybdenum and tungsten hexacarbo-nyls and alkylmolybdenum and alkyltungsten complexes have been studied most.6,24,26 Anchored organomolybdenum complexes are particularly effective catalysts, even at temperatures below 0°C however, they quickly lose activity.41-43... 

The implementation of enantioselectivity issues in heterogenized oxidation catalysts has been a key strategy for a number of years which has been successful only with certain classes of catalysts. For example, molybdenum and rhenium catalysts are among the most efficient in epoxidation reactions, however, attempts to modify them with chiral ligands in order to achieve enantioselective transformations, either in solution or anchoring the resulting species on solid supports such as the MCM family, has met with only moderate success. The activity is generally decreased and only poor to moderate enantioselectivities have been observed in some cases. This topic has been recently reviewed. ... 

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