NDLI: Vanadyl cationic complexes as catalysts in olefin oxidation

Content Provider	World Health Organization (WHO)-Global Index Medicus
Author	Veiros, Luis F. Moniz, Tânia Mourato, Ana C. Calhorda, Maria José Nunes, Carla D. Rangel, Maria Vaz, Pedro D. Félix, Vítor Realista, Sara
Description	Author Affiliation: Nunes CD ( Centro de Química e Bioquímica, DQB, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal. mjc@ciencias.ulisboa.pt.)
Abstract	Three new mononuclear oxovanadium(IV) complexes [VO(acac)(R-BIAN)]Cl (BIAN = 1,2-bis{(R-phenyl)imino}acenaphthene, R = H, 1; $CH_{3},$ 2; Cl, 3) were prepared and characterized. They promoted the catalytic oxidation of olefins such as cyclohexene, cis-cyclooctene, and styrene with both tbhp (tert-butylhydroperoxide) and $H_{2}O_{2},$ and of enantiopure olefins (S(−)- and R(+)-pinene, and S(−)- and R(+)-limonene) selectively to their epoxides, with tbhp as the oxidant. The TOFs for styrene epoxidation promoted by complex 3 with $H_{2}O_{2}$ (290 mol $mol^{−1}_{V}$ $h^{−1})$ and for cis-cyclooctene epoxidation by 2 with tbhp (248 mol $mol^{−1}_{V}$ $h^{−1})$ are particularly good. Conversions reached 90% for several systems with tbhp, and were lower with $H_{2}O_{2}.$ A preference for the internal C=C bond, rather than the terminal one, was found for limonene. Kinetic data indicate an associative process as the first step of the reaction and complex $[VO(acac)(H-BIAN)]^{+}$ $(1^{+})$ was isolated in an FTICR cell after adding tbhp to 1. EPR studies provide evidence for the presence of a V(IV) species in solution, until at least 48 hours after the addition of tbhp and cis-cyclooctene, and cyclic voltammetry studies revealed an oxidation potential above 1 V for complex 1. DFT calculations suggest that a $[VO(H-BIAN)(MeOO)]^{+}$ complex is the likely active V(IV) species in the catalytic cycle from which two competitive mechanisms for the reaction proceed, an outer sphere path with an external attack of the olefin at the coordinated peroxide, and an inner sphere mechanism starting with a complex with the olefin coordinated to vanadium.
ISSN	14779226
Issue Number	11
Volume Number	44
e-ISSN	13645447
Journal	Dalton Trans.
Language	English
Publisher	Royal Society of Chemistry
Publisher Date	2015-03-21
Publisher Place	Great Britain (UK)
Access Restriction	Subscribed
Subject Keyword	Alkenes Chemistry Organometallic Compounds Vanadium Catalysis Electrochemistry Kinetics Models, Molecular Molecular Conformation Oxidation-Reduction Quantum Theory Stereoisomerism Journal Article Research Support, Non-U.S. Gov't
Content Type	Text
Resource Type	Article
Subject	Inorganic Chemistry

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