Gopal Mishra - CuII complexes bearing the 2,2,2-tris(1-pyrazolyl)ethanol or 2,2,2-tris(1-pyrazolyl)ethyl methanesulfonate scorpionates. X-Ray structural characterization and application in the mild catalytic peroxidative oxidation of cyclohexane

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      Abstract:

        A variety of newly synthesized and well characterized   alkoxysilane pentacoordinate Oxovanadium(IV) complexes,   VO[Sal(PMeOSi)DPTA] 3[a], VOICI-Sal(PMeOSi)DPTAI 3[b],   VO[Sal(PMeOSi)DETA] 6[a] and VO[Cl-Sal(PMeOSi)DETA] OA, (Sal =   salicylaldehyde, DPTA= bis(aminopropyl)amine, DETA =   diaminoethylamine), have been anchored by covalent bond into the   surface of SiO(2) and/or Al(2)O(3) via silicon-alkoxide route by   a condensation process as supported catalysts. These solid   supported catalysts (abbreviated as catalysts A to H) showed high   catalytic efficiency in the selective oxidation reaction of   cyclohexane using molecular oxygen under relatively mild   condition in a micro-batch reactor. The Catalyst C (SiO(2)/3[a]   complex) system exhibits best activity, overall yield 38.5%   (TONs, ca. 5.0 x 10(3)) as well as high selectivity 98%   (cyclohexanol 74%, cyclohexanone 24%). Notably, cyclohexane shows   significantly improved yield 44.0%, by the addition of   pyrazinecarboxylic acid as a co-catalyst. The TGA indicates these   catalysts are stable up to maximum reaction temperature, ca. 473   K and ICP analysis shows there is negligible vanadium loss from   the supported catalyst after the reaction, allowing further use   of the V-catalyst. The various factors influences (i.e.   temperature, O(2) pressure, reaction time, catalyst amount) were   also investigated in the systematic way, to optimize the reaction   processes. The impact of radical traps and detection of   intermediate peroxy radical were also investigated to establish a   radical mechanism.

      Address (URL): http://www.sciencedirect.com/science/article/pii/S0926860X10004357