Carbon Monoxide Coupling Reactions: A New Concept for the Formation of Hexahydroxybenzene. Issue 64 (18th September 2020)

• Record Type: Journal Article
• Authors: Rosenthal, Uwe
• Is Part Of: Chemistry. Volume 26:Issue 64(2020)
• Page Start: 14507
• Page End: 14511
• Publication Date: 2020-09-18
• Subjects: carbon monoxide -- coupling -- hetero-metallacyclopentynes -- mechanism -- unusual reactions; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.202001947
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: For linear and cyclic coupling reactions of CO, among other products, the formation of the hexapotassium salt of hexahydroxybenzene is of particular interesting. The interaction of metallic potassium and CO offers, via the assumed K[OC≡CO]K as the result of several carbon monoxide coupling reactions, the formation of C6 (OK)6 among other products. To date, only speculations exist about the reaction pathway for these products, which were first described by Liebig in 1834. A novel concept is suggested here, which consists of the single steps (i) reductive coupling of CO, (ii) formation of dihetero‐metallacyclopentynes ( cis ‐2, 5‐diheterobutatriene as formal ethylenedione O=C=C=O complexes), (iii) formation of its dinuclear 1‐metalla‐2, 5‐dioxo‐cyclopentyne complexes by external coordination of the triple bond, (iv) insertion of CO into the M−C bond of the formed metallacyclopropene, and (v) the reductive elimination of C6 (OK)6 . The novel aspect of this concept is the formation of dihetero‐metallacyclopentynes (in analogy to the well characterized all‐C‐metallacyclopentynes), which have not been considered in the mechanism of reductive CO coupling reactions. It is expected that the presence of transition‐metal impurities would promote the reaction. Abstract : A very old reaction in a new light : A very old reaction is the formation of the hexapotassium salt of hexahydroxybenzene C6 (OK)6 by the interaction of metallic K and CO. To date, only speculations exist about the reaction pathway for its formation. A novel concept is presented, based on metalla‐dioxo‐cyclobutadiynes ( cis ‐2, 5‐dioxo‐butatriene as formal ethylenedione O=C=C=O complexes) in analogy to the experience to the well characterized all‐C‐metallacyclopentynes.