A cyclic thioketone as biradical heterocyclopentane-1,3-diyl: synthesis, structure and activation chemistry

• Published in: Inorganic chemistry frontiers 2022-05, Vol.9 (11), p.2659-2667
• Main Authors: Beer, Henrik, Linke, Alexander, Bresien, Jonas, Villinger, Alexander, Schulz, Axel
• Format: Article
• Language: English
• Subjects: Cage compounds; Chemical synthesis; Chlorine; Inorganic chemistry; Magnesium; Oxidation; Scavenging; Thiourea derivatives
• ISSN: 2052-1545; 2052-1553
• DOI: 10.1039/d2qi00482h

The reaction of the biradical [(μ-NTer)P·]2 with thiophosgene, SCCl2, leads to a cyclic phospha-aza thiourea derivative in very good yields. This synthetic approach represents a new possibility to prepare cyclic thioketones starting from four-membered cyclo-diphosphadiazanediyls by formal CS insertion with simultaneous oxidation of the two phosphorus atoms by the two chlorine atoms. When the phospha-aza thiourea derivative is reduced with magnesium chips, a deep blue, highly labile cyclic thioketone is formed, which can be regarded as a biradical heterocyclopentane-1,3-diyl. This new biradical can be converted to a housane species by light, which triggers transannular P–P bond formation. A thermal back-reaction was not observed, but scavenging reactions with CS2 or PhCHO clearly indicate the intermediate formation of the labile, biradical cyclic thioketone. Various intercepted products, such as [2.2.1]bicyclic cage compounds could be isolated and structurally characterized. Freshly in situ generated biradical thioketone can be utilized to activate small molecules.