Synthesis of Bicyclic P,S-Heterocycles via the Addition of Thioketones to a Phosphorus-Centered Open-Shell Singlet Biradical

• Published in: Inorganic chemistry Vol. 61; no. 4; pp. 2031 - 2038
• Main Authors: Beer, Henrik, Linke, Alexander, Bresien, Jonas, Mlostoń, Grzegorz, Celeda, Małgorzata, Villinger, Alexander, Schulz, Axel
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 31.01.2022
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.1c03207

Formal addition reactions between the open-shell singlet biradical [P­(μ-NTer)]2 (1Ter) and xanthione, thioxanthione, as well as ferrocenyl naphthyl thioketone were studied in detail. Reactions were performed at room temperature and led to the formation of strained [2.1.1]-cage P,S-heterocycles (3). All addition products were isolated and fully characterized by spectroscopic methods. Furthermore, reversible cleavage of the xanthenthione-biradical addition product into the parent compounds (biradical and thioketone) could be demonstrated by 31P­{1H} NMR spectroscopy. The thermodynamic stability of all cyclization products with respect to the elimination of thioketone was studied by quantum-chemical computations including solvent effects. Regarding the dissociation of addition products 3 into the fragment molecules 1Ter and ketone/thioketone, calculations prove that a significantly larger distortion energy in ketones compared with thioketones causes lower thermodynamic stability of the ketone adducts.