NMR spectroscopic studies on chalcogen compounds. 4. Carbon-13 isotope effect on selenium-77 and tellurium-125 nuclear shielding and its correlation with carbon-selenium bond distances. Tellurium-123 isotope effect on tellurium-125 nuclear shielding

Abstract

Supplementary Material Available: Listings of observed and calculated structure factors for C13H22lN2PtBF4 (3) and positional and thermal parameters, bond distances, and bond angles for 3 (Table II) and an ortep drawing giving a stereoview of 3 (Figure 3) (29 pages). Ordering information is given on any current masthead page.

Isotopic Effect on X-Nuclei Screening and X–H(D) Scalar Spin-Spin Coupling in XH4 and XO4

“…An analogous dependence of the isotopic shift (5(77Se) due to the 12C -13C substitution on the 77Se -13C bond length has been reported in Ref. [4] for a number of organo-selenium com pounds: the longer is the Se -C bond the lesser is the magnitude of the isotopic upfield shift |<3(77Se)| in duced by the 12C -13C substitution.…”

“…The secondary isotopic effect is relevant to a change in the screening constant (the isotopic shift) of the X nuclei and in SSCC for different isotopom ers. A t present, there are num erous experim ental data on the correlation of isotopic shifts with the structure of molecules [1], the character of chemical bond [2,3], magnitudes of internuclear distances and am plitudes of nuclear vibrations [4,5]. An analysis of the ex perim ental data reveals a num ber of general trends in the behaviour of isotopic shifts [6,7]: i) injection of a heavier isotope results in the rise of the screen ing constant (the upfield shift), ii) the m agnitude of the isotopic shift increases with the atomic num ber of the element corresponding to the resonating nucleus.…”

29/28, 30/28Silicon, 34/32sulfur and 80/77selenium isotope‐induced fluorine chemical shifts through two bonds

“…4,5 The splitting is due in part to the shortening of the distance between the fluorine atom and the other atom; for this part there is a proportionality between the distance and the splitting. 6 Studies of isotope-induced chemical shifts n  19 F(X) (where n is the number of intervening bonds between fluorine and X the heteroatom) showed large differences for sulfur, 7 silicon 8 and selenium 9 in the case of n D 1. In a pioneering study, a very large 2  19 F 34/32 S effect was observed in the 2-fluorothiophene spectrum.…”

NMR-spektroskopische Untersuchungen an Chalkogenverbindungen, VI [1]. 34S-Isotopeneffekte auf 19F-NMR-Frequenzen und ihre Abhängigkeit von Bindungslängen / NMR Spectroscopic Studies on Chalcogen Compounds, VI [1] l4.34S Isotope Effects on 19F-NMR Frequencies and their Dependence on Bond Lengths

“…Beispielsweise wurden Sauerstoff-Austauschreaktionen mit Hilfe von 1816 0-Isotopenverschiebungen verfolgt [4], und es wurde über den Zusammenhang zwischen Isotopenverschiebung und Bindungslänge berichtet [5,6], Ziel der vorliegenden Arbeit war es, die Abhän-gigkeit der Isotopenverschiebung von der Bindungslänge in einer weiteren Verbindungsklasse zu über-prüfen. Für solche Untersuchungen sind SF 4 und seine Derivate besonders gut geeignet, da sie innerhalb desselben Moleküls längere axiale und kürzere äquatoriale S-F-Bindungen enthalten.…”

“…Für solche Untersuchungen sind SF 4 und seine Derivate besonders gut geeignet, da sie innerhalb desselben Moleküls längere axiale und kürzere äquatoriale S-F-Bindungen enthalten. Der 34 S-Isotopeneffekt über eine Bindung auf die 19 F-chemische Verschiebung ( 1 J 19 F( 34/32 S), Definition siehe [5]) wurde bereits an einigen wenigen Beispielen nachgewiesen [7]. In dieser Arbeit wird auch über den glei- [5].…”