title: Interplay of Experiment and Theory in Elucidating Mechanisms of Oxidation Reactions by a Nonheme Ru(IV)O Complex.
abstract: A comprehensive experimental and theoretical study of the reactivity patterns and reaction mechanisms in alkane hydroxylation, olefin epoxidation, cyclohexene oxidation, and sulfoxidation reactions by a mononuclear nonheme ruthenium(IV)-oxo complex, [Ru(IV)(O)(terpy)(bpm)](2+) (1), has been conducted. In alkane hydroxylation (i.e., oxygen rebound vs oxygen non-rebound mechanisms), both the experimental and theoretical results show that the substrate radical formed via a rate-determining H atom abstraction of alkanes by 1 prefers dissociation over oxygen rebound and desaturation processes. In the oxidation of olefins by 1, the observations of a kinetic isotope effect (KIE) value of 1 and styrene oxide formation lead us to conclude that an epoxidation reaction via oxygen atom transfer (OAT) from the Ru(IV)O complex to the C═C double bond is the dominant pathway. Density functional theory (DFT) calculations show that the epoxidation reaction is a two-step, two-spin-state process. In contrast, the oxidation of cyclohexene by 1 affords products derived from allylic C-H bond oxidation, with a high KIE value of 38(3). The preference for H atom abstraction over C═C double bond epoxidation in the oxidation of cyclohexene by 1 is elucidated by DFT calculations, which show that the energy barrier for C-H activation is 4.5 kcal mol(-1) lower than the energy barrier for epoxidation. In the oxidation of sulfides, sulfoxidation by the electrophilic Ru-oxo group of 1 occurs via a direct OAT mechanism, and DFT calculations show that this is a two-spin-state reaction in which the transition state is the lowest in the S = 0 state.
authors.affiliation: †Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea.|‡Department of Chemistry, Goa University, Goa 403 206, India.
authors.forename: Sunder N
authors.initials: SN
authors.lastname: Dhuri
authors.affiliation: †Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea.
authors.forename: Kyung-Bin
authors.initials: KB
authors.lastname: Cho
authors.affiliation: †Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea.
authors.forename: Yong-Min
authors.initials: YM
authors.lastname: Lee
authors.affiliation: †Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea.
authors.forename: Sun Young
authors.initials: SY
authors.lastname: Shin
authors.affiliation: †Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea.
authors.forename: Jin Hwa
authors.initials: JH
authors.lastname: Kim
authors.affiliation: §Institute of Chemistry and the Lise Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel.
authors.forename: Debasish
authors.initials: D
authors.lastname: Mandal
authors.affiliation: §Institute of Chemistry and the Lise Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel.
authors.forename: Sason
authors.initials: S
authors.lastname: Shaik
authors.affiliation: †Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea.
authors.forename: Wonwoo
authors.initials: W
authors.lastname: Nam