Kinetics and mechanism of epoxidation of olefins by chiral tetrapyridyl oxoiron(IV) complex. (1st September 2018)

• Record Type: Journal Article
• Authors: Meena, Bashdar I.; Lakk-Bogáth, Dóra; Kripli, Balázs; Speier, Gábor; Kaizer, József
• Is Part Of: Polyhedron. Volume 151(2018)
• Page Start: 141
• Page End: 145
• Publication Date: 2018-09-01
• Subjects: Biomimetics -- Alkene epoxidation -- Iron(IV)-oxo complex -- Enantioselectivity -- Kinetics; Chemistry, Inorganic -- Periodicals; Chimie inorganique -- Périodiques; Organometaalverbindingen; Anorganische chemie; 546.05
• DOI: 10.1016/j.poly.2018.05.044
• Languages: English
• ISSNs: 0277-5387

Abstract

Graphical abstract: The reactivity of oxoiron(IV) complex, [Fe IV (asN4Py)(O)] 2+ with chiral pentadentate ligand, has been investigated in the oxidation reaction of various alkenes such as cis -cyclooctene and styrene derivatives. Abstract: The reactivity of the previously reported low-spin ( S = 1) oxoiron(IV) complex, [Fe IV (asN4Py)(O)] 2+ (2 ) with chiral pentadentate ligand, asN4Py (asN4Py = N, N -bis(2-pyridylmethyl)-1, 2-di(2-pyridyl)ethylamine), has been investigated in the oxidation reaction of various alkenes such as cis -cyclooctene and styrene derivatives. A linear free-energy relationship between the second-order rate constants ( k 2 ) for the para -substituted styrene oxidations and the total substituent effect (TE) parameters has been established: ρ TE = +0.19. A comparison of this correlation for the corresponding oxoruthenium(IV)-mediated epoxidation reactions has revealed that the oxidation of aromatic alkenes mediated by 2 proceeds via the rate-limiting formation of a benzylic radical intermediate in a nonconcerted process. Based on these results above, similar mechanism with radicaloid intermediates can be proposed for other cyclic and acyclic alkenes. The moderate enantioselectivities for the oxidation of styrene derivatives (8–12% ee) can be explained by the rotation/collapse processes through CC bond of the radicaloid species before the epoxide ring closure.