C-13, F-19 and Se-77 NMR study of vicinal (E)-fluoro(organylseleno)olefinsand [(E)-fluoroalkenyl]diorganylselenonium salts

C-13, F-19 and Se-77 NMR spectra of the (E)-fluoro(organylseleno)olefins R- 1(F)C-alpha=CbetaR2(SeR3) and the [(E)-fluoroalkenyl]diorganylselenonium sa lts R-1(F)C-alpha=(CR2)-R-beta((Se+RR4)-R-3) X- were measured and assigned. The C-13, F-19 and Se-77 NMR chemical shifts, the (1)J(F,C) and (2)J(F,C-b eta) couplings, the vicinal (3)J(Se,F) couplings, some selected C-13, C-13 and Se-77, C-13 couplings and the F-19, C-13 couplings to the groups R-1-R- 4 are discussed in relation to the structure of the compounds investigated. (1)J(F,C) increases with deshielding of the C-13-alpha atoms of the fluoro (organylseleno)olefins and the fluoroalkenyldiorganylselenonium salts, i.e. both quantities are influenced by the same electronic effects. Linear Hamm ett correlations of para-substituted phenylseleno derivatives (R=MeO, Me, P h, H, Cl, COOH, COOEt, CN; R-1=R-2=Et) between delta(C-13-alpha), delta(C-1 3-beta), delta(F-19), delta(Se-77) and (3)J(Se,F), respectively, and sigma( p) values, and linear correlations between the experimental quantities delt a(Se-77)/delta(F-19), delta(Se-77)/(3)J(Se,F) and delta(F-19)/(3)J(Se,F) (e ach with a positive slope) show that close relations exist (i) between the NMR chemical Shifts within the FC=CSe moiety and (ii) between the NMR chemi cal shifts (Se-77, F-19) and the couplings (3)J(Se,F) by alteration of the electron density in this structural element. The vicinal (3)J(Se,F) couplin g constant across the C=C double bond (trans-coupling) is sensitive to stru ctural alterations (<1 to 68.5 Hz). In the case of 1,1-difluorovinylphenyl selenide, F2C=CHSePh, the (3)J(Se,F) coupling constants obey the relation ( 3)J(trans) > (3)J(cis) (40.8, 3.2 Hz). Copyright (C) 1999 John Wiley & Sons , Ltd.