Publication Type Journal Article
Title New (VO)-O-IV-complexes for oxidative desulfurization of refractory sulfur compounds in fuel: synthesis, structure, reactivity trend and mechanistic studies
Authors Tendai O. Dembaremba Isabel Correia Eric C. Hosten Maxim L. Kuznetsov Wilhelmus J. Gerber J.C. Pessoa Adeniyi S. Ogunlaja Zenixole R. Tshentu
Year 2019
Month November
Volume 48
Number 44
Pages 16687-16704
Abstract A series of 5-coordinate oxidovanadium(iv) complexes based on 2-(2 -hydroxyphenyl)imidazole (HPIMH), with substituent groups of different electronegativities on the phenolic para position (HPIMX; X = -H, -Br, -OMe and -NO2), were synthesized and characterized. Three of these complexes were characterized by single crystal X-ray diffraction, [(VO)-O-IV(PIMH)(2)], [(VO)-O-IV(PIMBr)(2)] and [(VO)-O-IV(PIMNO2)(2)], as well as a dioxidovanadium(v) compound ([(VO2)-O-V(PIMH)(PIMH2)]). The complexes were tested for their catalytic activities in the oxidation of dibenzothiophene (DBT), the major refractory organosulfur compound found in fuel. The nitro substituted compound [(VO)-O-IV(PIMNO2)(2)] had the highest catalytic oxidation activity followed by: [(VO)-O-IV(PIMH)(2)] > [(VO)-O-IV(PIMBr)(2)] > [(VO)-O-IV(PIMMeO)(2)]. The decrease in activity is attributed to the different electronegativities of the substituent groups, which influence the electron density on the metal center, the VO bond distances and infrared stretching bands. Geometry index (tau) values calculated from single crystal X-ray diffraction (SC-XRD) data and DFT studies provided further insights on the trend in activity observed. SC-XRD, EPR, V-51 NMR and UV-Vis spectroscopies, and DFT studies were instrumental in studying the mechanism of the catalyzed reaction and proposal of intermediate species. Both radical and non-radical pathways are plausible for the catalytic oxidation and participation of reactive oxygen species in both pathways is also postulated.
Book Title
ISSN 1477-9226
EISSN 1477-9234
Conference Name
Bibtex ID ISI:000496535000020
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