Homolytic C-H Bond Activation by Phosphine-Quinone-Based Radical Ion Pairs.

Autor: Helling C; Van't Hoff Institute for Molecular Sciences, University of Amsterdam, PO Box 94157, 1090, GD Amsterdam, The Netherlands., van der Zee LJC; Van't Hoff Institute for Molecular Sciences, University of Amsterdam, PO Box 94157, 1090, GD Amsterdam, The Netherlands., Hofman J; Van't Hoff Institute for Molecular Sciences, University of Amsterdam, PO Box 94157, 1090, GD Amsterdam, The Netherlands., de Zwart FJ; Van't Hoff Institute for Molecular Sciences, University of Amsterdam, PO Box 94157, 1090, GD Amsterdam, The Netherlands., Mathew S; Van't Hoff Institute for Molecular Sciences, University of Amsterdam, PO Box 94157, 1090, GD Amsterdam, The Netherlands., Nieger M; Department of Chemistry, University of Helsinki, A. I. Virtasen aukio 1, P.O. Box 55, FIN-00014, Helsinki, Finland., Slootweg JC; Van't Hoff Institute for Molecular Sciences, University of Amsterdam, PO Box 94157, 1090, GD Amsterdam, The Netherlands.
Jazyk: angličtina
Zdroj: Angewandte Chemie (International ed. in English) [Angew Chem Int Ed Engl] 2023 Nov 27; Vol. 62 (48), pp. e202313397. Date of Electronic Publication: 2023 Oct 26.
DOI: 10.1002/anie.202313397
Abstrakt: Herein, we present the formation of transient radical ion pairs (RIPs) by single-electron transfer (SET) in phosphine-quinone systems and explore their potential for the activation of C-H bonds. PMes 3 (Mes=2,4,6-Me 3 C 6 H 2 ) reacts with DDQ (2,3-dichloro-5,6-dicyano-1,4-benzoquinone) with formation of the P-O bonded zwitterionic adduct Mes 3 P-DDQ (1), while the reaction with the sterically more crowded PTip 3 (Tip=2,4,6-iPr 3 C 6 H 2 ) afforded C-H bond activation product Tip 2 P(H)(2-[CMe 2 (DDQ)]-4,6-iPr 2 -C 6 H 2 ) (2). UV/Vis and EPR spectroscopic studies showed that the latter reaction proceeds via initial SET, forming RIP [PTip 3 ]⋅ + [DDQ]⋅ - , and subsequent homolytic C-H bond activation, which was supported by DFT calculations. The isolation of analogous products, Tip 2 P(H)(2-[CMe 2 {TCQ-B(C 6 F 5 ) 3 }]-4,6-iPr 2 -C 6 H 2 ) (4, TCQ=tetrachloro-1,4-benzoquinone) and Tip 2 P(H)(2-[CMe 2 {oQ tBu -B(C 6 F 5 ) 3 }]-4,6-iPr 2 -C 6 H 2 ) (8, oQ tBu =3,5-di-tert-butyl-1,2-benzoquinone), from reactions of PTip 3 with Lewis-acid activated quinones, TCQ-B(C 6 F 5 ) 3 and oQ tBu -B(C 6 F 5 ) 3 , respectively, further supports the proposed radical mechanism. As such, this study presents key mechanistic insights into the homolytic C-H bond activation by the synergistic action of radical ion pairs.
(© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)
Databáze: MEDLINE
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