Thiopyrylium and Dithiolium Ions

Thiopyrylium and Dithiolium Ions. Nothing has been published on the electronic structure of thiins (85) (for the calculated inversion barrier, though, see ref. 28) although the isO -Tr-electronic tropylium ions thiopyrylium (86), 1,2-dithiolium (87), and 1,3-dithiolium (88) have been considered in several papers. 

Non-empirical calculations for (86)—(88) by Palmer and Findlay have revealed that d-orbitals participate only to a trivial extent. The charge distributions obtained from non-empirical calculations differ considerably from those from all-valence-electron treatments. Nevertheless some semi-empirical calculations gave results in good agreement with experimental data. Some arguments for the importance of the S 3d-orbitals in (86) have come from an EHT interpretation of the H chemical shifts against 

Fabian, K. Fabian, and H. Hartmann, Theor. Chim. Acta, 1968, 12, 319 Z. Yoshida, H. Sugimoto, and S. Yoneda, Tetrahedron, 1972, 28, 5873. 

Skoupy,and R. Zahradnik, Coll. Czech. Chem. Comm., 1972, 37, 1520 A. Mistr and R. Zahradnik, ibid., 1973, 38, 1668. 

Kataoka, Y. Asahi, and E. Mizuta, Chem. and Pharm. Bull. (Japan), 1973, 21, 1415. 

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