C-13 AND F-19 NMR-STUDY OF ALPHA,BETA-DIFLUOROSTYRYL DERIVATIVES OF TRANSITION-METAL CARBONYLATES - A METHOD OF SIGNAL ASSIGNMENT BASED ON THE CARBON-FLUORINE SPIN-SPIN COUPLING-CONSTANTS

The C-13 and F-19 NMR spectra of Z- and E-isomers of beta-X-substitute d alpha,beta-difluorostyrenes (X = F, Cl, CpFe(CO)(2), Re(CO)(5), Re-2 (CO)(9)Na) were studied. Direct and long-range (across 1-5 bonds) spin -spin coupling constants and the (C-13-C-12) isotope shifts in the F-1 9 NMR spectra were determined. The study of the C-13 satellites in the F-19 NMR spectra of substituted difluorostyrenes permitted assignment of the C-13 NMR signals of the vinylic carbon atoms. Similarly, the s ignals in F-19 NMR spectra were assigned based on coupling constants o f fluorine with ipso-carbon. These assignments were found to be in goo d agreement with the data available from the literature (X = F, CI). T he developed approach was applied to the elucidation of the structure of Z-PhCF=CClFe(CO)(2)Cp.