Dioxidomolybdenum(VI) complexes bearing sterically constrained aroylazine ligands: Synthesis, structural investigation and catalytic evaluation

• Published in: Inorganica Chimica Acta Vol. 469; pp. 366 - 378
• Main Authors: Majumder, Sudarshana, Pasayat, Sagarika, Roy, Satabdi, Dash, Subhashree P., Dhaka, Sarita, Maurya, Mannar R., Reichelt, Martin, Reuter, Hans, Brzezinski, Krzysztof, Dinda, Rupam
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.01.2018; Elsevier Science Ltd
• Subjects: Aldehydes; Aroylazines; Benzaldehyde; Benzil; Benzoic acid; Benzoin; Bromination; Catalysis; Catalysts; Chemical synthesis; Conversion; Coordination compounds; Crystallography; Dioxidomolybdenum(VI); Hydrogen peroxide; Hydroxynaphthoic acid; Infrared spectroscopy; Ketones; Ligands; NMR spectroscopy; Oxidation; Oxidation of benzoin; Oxidative bromination of salicylaldehyde; X-ray crystallography; X-ray crystallography; Dioxidomolybdenum(VI); Aroylazines; Oxidation of benzoin; Oxidative bromination of salicylaldehyde
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/j.ica.2017.09.043

Synthesis, characterization and catalytic potential of dioxidomolybdenum(VI) complexes of aroylazines. [Display omitted] •Sterically constrained aroylazine ligands.•cis-Dioxidomolybdenum(VI) complexes.•X-ray crystallography.•Catalytic applications on oxidation of benzoin and oxidative bromination of salicylaldehyde. Seven new dioxidomolybdenum(VI) complexes [MoO2L1(X)].X (1) and [MoO2L2–7(X)] (2–7) [Where X=EtOH in case of 1 and 5 and X=DMSO in case of 2–4 and 6, 7] of aroylazines containing a bulky 3-hydroxy-2-naphthoic substituent, were isolated and structurally characterized. The aroylazine ligands H2L1–7 were derived from the condensation of 3-hydroxy-2-naphthoic acid hydrazide with several substituted aromatic aldehydes/ketones. All the synthesized ligands and metal complexes were successfully characterized by elemental analysis, IR, UV–Vis and NMR spectroscopy. X-ray structures of 1–6 revealed that the ligands coordinate to the metal center as a dibasic tridentate ligand. Cyclic voltammetry of the complexes shows two irreversible reductive responses within the potential window −0.50 to −1.36V, due to MoVI/MoV and MoV/MoIV processes. The synthesized complexes 1–7 were used as catalysts for the oxidation of benzoin, and for the oxidative bromination of salicylaldehyde, as a functional mimic of haloperoxidase. It was found that the percentage of conversion increased significantly in the presence of catalysts 1–7 which contained bulky substituents, and showed high percentage of conversion (>90%) with high turnover frequency (>1100h−1) than previously reported catalysts. Benzil, benzoic acid and benzaldehyde-dimethylacetal were formed selectively for the oxidation of benzoin. Formation of 5-bromosalicylaldehyde and 3,5-dibromosalicylaldehyde took place during the oxidative bromination of salicylaldehyde in presence of H2O2 asan oxidant and therefore 1–7 act as functional models of vanadium dependent haloperoxidases.