engleski

Tetranuclear molybdenum(vi) hydrazonato epoxidation (pre)catalysts: Is water always the best choice?

Metallosupramolecular chemistry area has grown exponentially with a key role of multinuclear metal complexes (MMC) [1, 2].The most interesting and challenging MMS are metal-organic frameworks (MOF) and self-assembled supramolecular coordination complexes (SCC), applied for sensing and molecular recognition. SSC are very interesting for their catalytic performance. Single- or mixed-linker tetrahedral coordination cages (Mn, Cr, Fe) with Mn(salen) and Cr(salen) moieties catalysed sequential asymmetric epoxidation/epoxide ring-opening reaction [3], while trinuclear Zr catalyst was active for ethylene polymerization. Inspired by the latter, we tested tetranuclear molybdenum(VI) aroylhydrazonato compounds, [MoO4L], as cyclooctene and cyclohexene epoxidation (pre)catalysts, with tert-butyl hydroperoxide available in water or decane. No organic solvent was added, following the green quote: The best solvent is no solvent. With cyclooctene, catalysts showed very good activity and selectivity towards epoxide with both oxidants. In cyclohexene (ep)oxidation, with TBHP in decane, catalytic activity was moderate with good selectivity towards epoxide, while with TBHPaq catalytic results were interesting in terms of diol formation, furtherly employed for adipic acid production. DFT calculations were used to support and explain experimental catalytic result for tetranuclear self-assembled systems.

molybdenum(VI) complexes ; hydrazone ; catalysis ; epoxidation

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