Synthesis and X-ray crystal structure of a Molybdenum(VI) Schiff base complex: Design of a new catalytic system for sustainable olefin epoxidation

Research Progress in Epoxidation of Light Small-Molecule Olefins

Light olefins, as important bulk raw materials in the petrochemical industry, play an irreplaceable role in the development of the manufacturing industry and the economy. The epoxides of light olefins are important intermediates for the synthesis of polymers, drugs, and fine chemicals, and their green, efficient, and safe synthesis has attracted much attention. This review focuses on the research progress of light olefin epoxidation and elucidates traditional epoxidation methods, such as the chlorohydrin method. Although these processes have mature processes, they have drawbacks, including equipment corrosion, environmental pollution, poor safety, and high waste emissions. Special emphasis is placed on catalytic epoxidation systems using oxygen or organic peroxides as oxygen sources. For homogeneous catalytic systems, certain metal complexes exhibit high activity and selectivity yet are difficult to separate and recycle. Moreover, heterogeneous catalytic systems have become a research hotspot due to their advantages of easy separation and reusability, with supported metal catalysts being a prime example. Meanwhile, the effects of reaction temperature, pressure, solvent, etc., on epoxidation are explored. The specific reaction mechanisms are also studied and analyzed. Current research challenges, including enhancing catalyst stability and reducing costs, are summarized. In the future, developing highly efficient, green, and economically viable epoxidation technologies for large-scale industrial applications represents an important research direction in this field.

Schiff Base-Based Molybdenum Complexes as Green Catalyst in the Epoxidation Reaction: A Minireview

Epoxides are class of cyclic ether and have been extensively used in petrochemicals and pharmaceuticals industries as raw materials. Due to this reasons, development of the synthetic strategy of epoxides are getting enormous interest among the research chemists. In terms of "development of the synthetic strategy", the use of a catalyst, especially, Schiff base-based complex is of potential interest due to alternative easy routes and significant advances in metal-mediated pathways giving rise to diverse degree of substrate-reagent interactions. In addition, the synthetic strategy that follows the 12 principles of green chemistry, particularly (i) reduce the use of organic solvent, especially toxic solvents, and (ii) increasing the use of catalysts to obtain selective and quick processes in terms of atom economy, are of great attention now a days. The present review encompasses the Schiff base-based molybdenum complexes as green catalyst in the epoxidation reaction. Molybdenum complexes have grown interest owing to lower cost, environmental protection and commercialization as well as its abundance in different metalloenzymes. On the other hand, molybdenum complexes speed up the O-O bond break of tert-butylhydroperoxide (TBHP); as a result, it accelerates the oxygen transfer process from TBHP to the olefin. This review mainly focused on the catalytic activity of molybdenum-based Schiff base complexes for the epoxidation reaction in water/solvent free condition.