Berechnung der 19F- und 195 Pt-NMR-Verschiebungen von FIuoro-Chloro-Bromo-Platinaten(IV) / Calculation of 19F and 195Pt NMR Shifts of Fluoro-Chloro-Brom o-Platinates(IV )

Abstract

By reaction of [PtBr4]2- with XeF2 in dichloromethane product mixtures containing nine fluoro-chloro-, four fluoro-bromo- and 15 fluoro-chloro-bromo-platinates(IV) are formed. All complexes are detectable by in situ l9F NMR measurements. Due to the increasing trans influence F < Cl < Br, the signals <5(19F) of symmetric F-Pt-F axes observed at highest field are shifted downfield on the average by 93 ppm as compared with δ(19F•) of F••Pt-Cl′ axes, and further to lower field by 40 ppm for <5(F••) of F••-Pt-Br″ axes. For the same reason the coupling constant 1J(F••Pt) ≈ 1099 Hz is by 13.3 % smaller than 1J(F•Pt) ≈ 1268 Hz, which is by 32.3 % smaller than δ(FPt) ≈ 1873 Hz. Based on the axis method, and taking into account characteristic increments of chemical shifts depending on cis influences, the calculation of the 195Pt NMR signals of 27 observed species of the system [PtFnCl6-n-mBrm]2- n, m = 0 - 6, has been successful. The 195Pt NMR shifts of further 29 so far not detected complexes are predicted. Using parameters depending on the geometry of the complex, the 19F NMR shifts of 28 F-containing platinates(IV) have been calculated in good agreement with the experimental data. 19F resonances are predicted for 19 so far missing complexes.