Metal matters: How vanadium and molybdenum rewrite hydrazone-based oxidation catalysis

Title : Metal matters: How vanadium and molybdenum rewrite hydrazone-based oxidation catalysis

Abstract:

The development of efficient and sustainable catalysts for benzylic oxidation remains an important challenge in modern oxidation chemistry, particularly in the context of greener routes. Although the conventional Co/Mn/Br catalytic system used for xylene oxidation is effective, its corrosive and environmentally demanding nature motivates the search for halogen-free alternatives. Transition-metal complexes capable of promoting selective oxidations under mild conditions therefore continue to attract considerable attention.

In this work, we report a new family of vanadium catalysts supported by hydrazone ligands derived from 5-methoxy-salycylaldehyde and salycylaldehyde. Hydrazone-based frameworks provide a versatile platform for tuning electronic and steric environments around redox-active metal centers, offering opportunities for improved catalytic performance. Despite vanadium’s recognized role in certain oxidative transformations, its application to the oxidation of xylenes is limited. Here, we explore these vanadium–hydrazone complexes as catalysts for the aerobic oxidation of xylene, as well as for the oxidation of benzyl alcohol, as a complementary model substrate commonly used to probe benzylic oxidation pathways. Our research group has previously investigated the oxidation of benzyl alcohol and its chloro-, nitro-, and methyl-substituted derivatives, providing a valuable reference point for evaluating the reactivity of the new catalysts.

To explore the influence of the metal center, the vanadium complexes were directly compared with their molybdenum analogues constructed from the same 5-methoxy-salycylaldehyde and salycylaldehyde ligand scaffold. Comprehensive structural and catalytic studies highlight how differences in electronic structure and coordination chemistry translate into distinct oxidative behaviors.

Overall, this comparative investigation expands the chemistry of hydrazone-based vanadium and molybdenum complexes and offers new insights into the design of sustainable oxidation catalysts for both industrial and model benzylic substrates.

Biography:

Dr. Jana Pisk is an Associate Professor of Chemistry at the University of Zagreb, Faculty of Science, where she has been a member of the Department of Chemistry since 2007. She earned her Ph.D. in 2012 and has conducted extended research in catalysis at the Laboratoire de Chimie de Coordination in Toulouse, France. Her scientific work centers on the coordination chemistry of molybdenum and vanadium compounds, with a strong focus on their catalytic applications in oxidation processes. Dr. Pisk has authored more than fifty publications and is actively engaged in advancing sustainable catalytic methodologies and functional inorganic materials.