Arylruthenium(III) Porphyrin-Catalyzed C–H Oxidation and Epoxidation at Room Temperature and [RuV(Por)(O)(Ph)] Intermediate by Spectroscopic Analysis and Density Functional Theory Calculations
2018
Shing, Ka-Pan | Cao, Bei | Liu, Yungen | Lee, Hung Kay | Li, Ming-De | Phillips, David Lee | Chang, Xiao-Yong | Che, Chi-Ming
The development of highly active and selective metal catalysts for efficient oxidation of hydrocarbons and identification of the reactive intermediates in the oxidation catalysis are long-standing challenges. In the rapid hydrocarbon oxidation catalyzed by ruthenium(IV) and -(III) porphyrins, the putative Ru(V)-oxo intermediates remain elusive. Herein we report that arylruthenium(III) porphyrins are highly active catalysts for hydrocarbon oxidation. Using catalyst [Ruᴵᴵᴵ(TDCPP)(Ph)(OEt₂)] (H₂TDCPP = 5,10,15,20-tetrakis(2,6-dichlorophenyl)porphyrin), the oxidation of C–H bonds of various hydrocarbons with oxidant m-CPBA at room temperature gave alcohols/ketones in up to 99% yield within 1 h; use of [ⁿBu₄N]IO₄ as a mild alternative oxidant avoided formation of lactone from cyclic ketone in C–H oxidation, and the catalytic epoxidation with up to 99% yield and high selectivity (no aldehydes as side product) was accomplished within 5 min. UV–vis, electrospray ionization–mass spectrometry, resonance Raman, electron paramagnetic resonance, and kinetic measurements and density functional theory calculations lend evidence for the formation of Ru(V)-oxo intermediate [Ruⱽ(TDCPP)(O)(Ph)].
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