Quinone reduction by organo-osmium half-sandwich transfer hydrogenation catalysts

DOI: 10.1021/acs.organomet.1c00358

Authors: Elizabeth M. Bolitho (University of Warwick) , Nathan G. Worby (University of Warwick) , James P. C. Coverdale (University of Warwick) , Juliusz A. Wolny (Technische Universität Kaiserslautern) , Volker Schünemann (echnische Universität Kaiserslautern) , Peter J. Sadler (University of Warwick)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Organometallics

State: Published (Approved)
Published: August 2021

Abstract: Organo-osmium(II) 16-electron complexes [OsII(η6-arene)(R-PhDPEN)] (where η6-arene = para-cymene or biphenyl) can catalyze the reduction of prochiral ketones to optically pure alcohols in the presence of a hydride source. Such complexes can achieve the conversion of pyruvate to unnatural d-lactate in cancer cells. To improve the catalytic performance of these osmium complexes, we have introduced electron-donor and electron-acceptor substituents (R) into the para (R1) or meta (R2) positions of the chiral R-phenyl-sulfonyl-diphenylethylenediamine (R-PhDPEN) ligands and explored the reduction of quinones, potential biological substrates, which play a major role in cellular electron transfer chains. We show that the series of [OsII(η6-arene)(R-PhDPEN)] derivatives exhibit high turnover frequencies, enantioselectivities (>92%), and conversions (>93%) for the asymmetric transfer hydrogenation (ATH) of acetophenone-derived substrates and reduce duroquinone and menadione to their di-alcohol derivatives. Modeling of the catalysis using density functional theory (DFT) calculations suggests a mechanism involving formic acid deprotonation assisted by the catalyst amine groups, phenyl-duroquinone stacking, hydride transfer to OsII, possible CO2 coordination, and tilting of the η6-arene ring, followed by hydride transfer to the quinone. These findings not only reveal subtle differences between Ru(II) and Os(II) catalysts, but also introduce potential biological applications.

Journal Keywords: Catalysts; Catalytic reactions; Redox reactions; Hydrocarbons; Quinones

Subject Areas: Chemistry


Technical Areas:

Added On: 25/08/2021 14:15

Documents:
acs.organomet.1c00358.pdf

Discipline Tags:

Physical Chemistry Catalysis Chemistry Organometallic Chemistry

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