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

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

Abstract:

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.S ingle- 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.

Audience take-away:

• Tetranuclear complexes are the area of rapidly growing metallosupramolecular chemistry.
• Catalysis under environmentally friendlier conditions with the use of TBHP in decane and TBHP in water.
• Green metrics parameters discussed and explained in details. 
• This is research that other faculty could use to expand their research or teaching. Furthermore, it provides a practical solution to a problem and gives insight in a detailed calculation of green metrics of the process on a lab-scale.
   

Biography:

J. Pisk got a Ph.D. in Chemistry in 2012. In 2010 she spent one year at LCC Toulouse and IUT P. Sabatier Toulouse III, France, where she learned the basics of catalysis. She was Marie Curie Cofund's fellow and did postdoctoral research at the LCC, Toulouse (Project “Diligent search for chemical bio-sources: Solvent-free homogeneous and heterogeneous oxidation processes catalyzed by polyoxometalates”). She was an Assistant Professor at the Faculty of Science, Zagreb, in 2018, and from 2023 she is an Associate Professor. Her major interest is the coordination chemistry of molybdenum and vanadium and the investigation of catalytic properties of the obtained materials.