NMR-spektroskopische Untersuchungen an Chalkogenyerbindungen, III 77Se- und 18C-NMR-Daten von Verbindungen mit C=S- und C=Se-Doppelbindung / NMR Spectroscopic Studies on Chalcogen Compounds, III 77Se and 13C NMR Data of Compounds Containing C=S and C=Se Double Bonds

Abstract

Abstract 77Se and 13C chemical shifts of compounds of type E=C=E′(E,E′=O, S, Se), Se = CF2, Se=C(NH2)2, Se = C(t-Bu)2 and 1,1,3,3-tetramethyl-2-indanselon are reported. The shielding of both nuclei in the C=Se entity depends strongly on the lowest electron excitation energy. 77Se-13C spin-spin coupling constants for the C=Se double bond are presented for the first time. The values show a strong dependence on the s-character of the carbon atom. This indicates an important Fermi contact contribution. Furthermore the influence of halogens, CF3S and CF3SS groups on the 13C chemical shift in thiocarbonyl compounds of the type S=C(Y)SCF3 (Y=F, Cl, Br) and S=C(SSCF 3)2 is described.