NMR-spektroskopische Untersuchungen an Chalkogenverbindungen, II [1]. 125Te-, 77Se-, 19F- und 13C-chemische Verschiebungen von CF3-substituierten Selen- und Tellurverbindungen [2] / NMR Spectroscopic Studies on Chalcogen Compounds, II [1]. 125Te-, 77Se-, 19F- and 13C Chemical Shifts of CF3 Substituted Selenium and Tellurium Compounds [2]

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Abstract
77Se chemical shifts of compounds CF3SeX exhibit an extraordinary good linear correlation with Huggins‘ electronegativities of χx. A range of 1051 ppm is covered for χx values between 1.9 and 3.15. Effective electronegativities are derived from the δ(77Se) values. For some compounds unexpected 77Se chemical shifts are found. This indicates an uncommon electronic constitution at selenium. Electron excitation energies are reported for some of the compounds and their importance for the paramagnetic shielding term is discussed. The relative shieldings of the tellurium compounds are analogous to those of the corresponding selenium compounds. In contrast to 77Se, the 19F shieldings of CF3EX compounds (E = chalcogen) depend inversely on the electronegativity of E and X. The 13C chemical shifts do not correlate with the χx values. NMR data of some CF3Se(IV) and CF3Te(IV) compounds are also reported for comparison