CALCULATION OF F-19 AND PT-195 NMR SHIFTS OF FLUORO-CHLORO-BROMO-PLATINATES(IV)

By reaction of [PtBr4](2-) with XeF2 in dichloromethane product mixtur es containing nine fluoro- chloro-, four fluoro-bromo- and 15 fluoro-c hloro-bromo-platinates(IV) are formed. All complexes are detectable by in situ F-19 NMR measurements. Due to the increasing trans influence F < Cl < Br, the signals delta(F-19) of symmetric F-Pt-F axes observed at highest field are shifted downfield on the average by 93 ppm as co mpared with delta(F-19(.)) of F-.-Pt-Cl' axes, and further to lower fi eld by 40 ppm for delta(F-..) of F-..-Pt-Br '' axes. For the same reas on the coupling constant (1)J((FPt)-Pt-..) approximate to 1099 Hz is b y 13.3% smaller than (1)J((FPt)-Pt-.) approximate to 1268 Hz, which is by 32.3% smaller than (1)J(FPt) approximate to 1873 Hz. Based on the axis method, and taking into account characteristic increments of chem ical shifts depending on cis influences, the calculation of the Pt-195 NMR signals of 27 observed species of the system [PtFnCl6-n-mBrm](2-) n, m = 0-6, has been successful. The Pt-195 NMR shifts of further 29 so far not detected complexes are predicted. Using parameters dependin g on the geometry of the complex, the F-19 NMR shifts of 28 F-containi ng platinates(IV) have been calculated in good agreement with the expe rimental data. F-19 resonances are predicted for 19 so far missing com plexes.