title: Interaction of 1,2,5-chalcogenadiazole derivatives with thiophenolate: hypercoordination with formation of interchalcogen bond versus reduction to radical anion.
abstract: According to the DFT calculations, [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazole (4), [1,2,5]selenadiazolo[3,4-c][1,2,5]thiadiazole (5), 3,4-dicyano-1,2,5-thiadiazole (6), and 3,4-dicyano-1,2,5-selenadiazole (7) have nearly the same positive electron affinity (EA). Under the CV conditions they readily produce long-lived π-delocalized radical anions (π-RAs) characterized by EPR. Whereas 4 and 5 were chemically reduced into the π-RAs with thiophenolate (PhS(-)), 6 did not react and 7 formed a product of hypercoordination at the Se center (9) isolated in the form of the thermally stable salt [K(18-crown-6)][9] (10). The latter type of reactivity has never been observed previously for any 1,2,5-chalcogenadiazole derivatives. The X-ray structure of salt 10 revealed that the Se-S distance in the anion 9 (2.722 Å) is ca. 0.5 Å longer than the sum of the covalent radii of these atoms but ca. 1 Å shorter than the sum of their van der Waals radii. According to the QTAIM and NBO analysis, the Se-S bond in 9 can be considered a donor-acceptor bond whose formation leads to transfer of ca. 40% of negative charge from PhS(-) onto the heterocycle. For various PhS(-)/1,2,5-chalcogenadiazole reaction systems, thermodynamics and kinetics were theoretically studied to rationalize the interchalcogen hypercoordination vs reduction to π-RA dichotomy. It is predicted that interaction between PhS(-) and 3,4-dicyano-1,2,5-telluradiazole (12), whose EA slightly exceeds that of 6 and 7, will lead to hypercoordinate anion (17) with the interchalcogen Te-S bond being stronger than the Se-S bond observed in anion 9.
authors.affiliation: Institute of Chemical Kinetics and Combustion, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia.
authors.forename: Elizaveta A
authors.initials: EA
authors.lastname: Suturina
authors.forename: Nikolay A
authors.initials: NA
authors.lastname: Semenov
authors.forename: Anton V
authors.initials: AV
authors.lastname: Lonchakov
authors.forename: Irina Yu
authors.initials: IY
authors.lastname: Bagryanskaya
authors.forename: Yuri V
authors.initials: YV
authors.lastname: Gatilov
authors.forename: Irina G
authors.initials: IG
authors.lastname: Irtegova
authors.forename: Nadezhda V
authors.initials: NV
authors.lastname: Vasilieva
authors.forename: Enno
authors.initials: E
authors.lastname: Lork
authors.forename: Rüdiger
authors.initials: R
authors.lastname: Mews
authors.forename: Nina P
authors.initials: NP
authors.lastname: Gritsan
authors.forename: Andrey V
authors.initials: AV
authors.lastname: Zibarev
mesh_terms: D000838:Anions / Q000737:chemistry; D001393:Azoles / Q000737:chemistry*; D005609:Free Radicals / Q000737:chemistry; D007700:Kinetics; D015394:Molecular Structure; D011789:Quantum Theory; D018036:Selenium Compounds / Q000737:chemistry*; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D000838:Anions; D001393:Azoles; D005609:Free Radicals; D018036:Selenium Compounds; D013438:Sulfhydryl Compounds