Impact of Surface Modification on the Oxidation of Linear Aliphatic Alcohols by Vanadium Complexes Supported on Merrifield Resin with Mixed Functionality Ligands

• Published in: ChemistrySelect (Weinheim) 2024-09, Vol.9 (36), p.n/a
• Main Authors: Kachhap, Payal, Chaudhary, Nikita, Haldar, Chanchal
• Format: Article
• Language: English
• Subjects: Alcohol oxidation; Aliphatic alcohol; DFT calculations; Heterogeneous catalysis; Merrifield resin; Vanadium complexes
• ISSN: 2365-6549; 2365-6549
• DOI: 10.1002/slct.202402642

Two oxidovanadium(IV) complexes [VO(xbp‐sc)] (1) and [VO(xbp‐tc)] (2) were prepared using hydrazine‐ether mixed functionality ligands Hxbp‐sc (I) and Hxbp‐tc (II), respectively. Complexes 1 and 2 were carefully grafted separately into imidazole‐modified chloromethylated polystyrene (Ps−Im) and unmodified chloromethylated polystyrene (PS−Cl) beads. Successfully anchored vanadium complexes Ps−Im‐[VO(xbp‐sc)] (3), Ps−Im‐[VO(xbp‐tc)] (4), Ps‐[VO(xbp‐sc)] (5), and Ps‐[VO(xbp‐tc)] (6) were tested for their catalytic potential towards the oxidation of aliphatic alcohols in the presence of hydrogen peroxide. Polymer‐grafted catalysts display excellent substrate conversion compared to most recent reports and good recyclability up to three cycles without losing much reactivity. High TOF values in the range of 183–591 h−1 are observed for the supported catalysts 3–6. The highest substrate conversion is observed for ethanol (63–97 %) under the optimized reaction conditions. Mainly, better substrate conversion is obtained with imidazole‐modified polymer beads grafted catalysts 3 and 4 than those grafted on unmodified polymer beads (5 and 6). Moreover, catalysts with the semicarbazide group in their ligand framework (3 and 5) show better reactivity towards alcohol with fewer carbon atoms. On the contrary, alcohols with longer carbon chains oxidize more easily in the presence of the catalyst with thiosemicarbazide frameworks (4 and 6). Two vanadium complexes of hydrazone‐ether mixed functionality ligands were reported. Imidazole‐functionalized and pure Merrifield resin was used for the heterogenization. Imidazole functionalized polymer‐supported catalysts act better than the catalyst grafted on pure Merrifield resin. A maximum of 97 % conversion was recorded for ethanol oxidation. Alcohols with longer carbon chains exhibit lower reactivity than short‐chain alcohols.