É. I. Fedin

Effect of substituents on the tautomeric equilibrium of 1(3)-(4-fluorophenyl)-3(1)-aryltriazenes in THF and pyridine

Conclusions1.The location of the tautomeric equilibrium of 1(3)-(4-fluorophenyl)-3(1)-aryltrizenes in THF and pyridine depends mainly on the resonance effects of the substituents.2.The chemical shifts of fluorine in the individual tautomers are linearly related to the Hammett σ constants of the substituents, and the effect of the substituents in the aryl radical on them is additive.

19F-NMR investigation of the comparative transmission capability of Hg-N bonds and the influence of the nature of the solvent on it

SummaryThe transmission of electronic effects of substituents in a number of arylmercury derivatives of 4-fluorobenzenesulfonanilides in inert and coordinating solvents has been studied by the19F NMR method. The binuclear bridge grouping Hg-N transmits electronic effects of substituents more strongly than an Hg bridge atom. The coordination interactions with the solvent substantially lower the transmission capacity of both mononuclear and binuclear organomercury systems, the quenching effect on the transmission of electronic effects of the substituents being considerably greater in the first case.

p-Fluorphenyl group as an indicator of charge on the carbon atom in aromatic compounds

A linear equation is presented for determining, from the chemical shift of19F in a p-fluorophenyl group, the effective charge of that CH fragment of the original aromatic molecule the carbon atom of which is bonded to the fluorophenyl indicator group. It has been shown that for a cyclic aromatic 6π-electron system determination of the effective charges of the CH fragments by quantum-chemical calculations and the evaluation of this charge from the19F chemical shift of the corresponding p-fluorophenyl substituents lead to coincident results.

19F NMR study of relative polarities and reactivities of N-H, N-Hg, and N-Au bonds in 2-(4-fluorophenyl)benzimidazole and its PhHg and Ph3PAu derivatives in intermolecular exchange

It has been shown by the19F NMR method that the relative polarities of nitrogenelement bonds in 2-(4-fluorophenyl)benzimidazole and its PhHg and PPh3Au derivatives increase in the order N-H<N-Hg<N-Au. Intermolecular exchange reactions of hydrogen-mercury, hydrogen-gold, and mercury-gold types in binary mixtures of these compounds have been studied by dynamic19F NMR. It has been found that these reactions occur by a bimolecular associative mechanism and that the N-H bond is substantially less reactive than the N-Hg and N-Au bonds, which have identical reactivities within the limits of sensitivity of the method used.

19F NMR study ofcis- andtrans- effects of substituted triphenylphosphine ligands intrans-(4-fluorophenyl)triarylphosphine-tri(4-fluorophenyl)phosphineplatinum 4-fluorothiophenoxides

A number of compounds of the type oftrans-4-FC6H4Pt(PAr3)2SC6H4F-4, where Ar is a substituted phenyl group, have been prepared starting from the corresponding chlorides. By exchange reactions oftrans-4-FC6H4Pt[P(C6H4F-4)3]2SC6H4F-4 with the above-mentioned compounds or Ar3P,trans-4-FC6H4Pt[P(C6H4F-4)3][PAr3]SC6H4F-4 have been generated in solution. For the latter compounds, the effect of Ar3P oncis- andtrans-ligands has been studied by the19F NMR technique. It has been shown that thecis- andtrans-effects of Ar3P run parallel and are well described by pKa values and ionization potentials of the unshared electron pair in Ar3P, as well as by σ0 constants of the aryl groups.

Investigation of transmitting ability of Sn-O binuclear bridge grouping by means of19F NMR

Conclusions1.On the basis of an investigation of19F-{1H} NMR spectra of a series of 4-fluororphenolates of triaryltins, Ar3SnOC6H4F-4, it has been established that the transmission ability (TA) of the SN-O binuclear bridge grouping differs slightly from that of the Sn bridge atom and the CH2O group.2.In contrast to the weak proton-donor solvent CHCl3, aprotic polar solvents — either noncoordinating or coordinating — reduce the electron conductivity of Ar3SnOC6H4F-4.

19F NMR Study of the transmission capacity of binuclear-N(X)SO2-bridging groups

Conclusions1.A comparative19F NMR study of a series of model ArN(X)SO2C6H4F-4 compounds (X=H, HgPh, and Na) showed that the mechanism for the transmission of the substituent electronic effects in these compounds depends on the polarity of the Nδ−-Xδ+ bond. An increase in this polarity leads to an increase in the relative contribution of direct polar conjugation.2.The specific solvation of the mercury atom in the binuclear bridging N(HgPh)SO2 group has only a slight effect on its transmission capacity.

Influence of intramolecular coordination on the transmissability of a bridging Hg-N group

ConclusionsOn investigation the19F-{1H} NMR spectra of two series of model compounds of type ArQN(SO2Ph)C6H3Br-2-F-4 (Q=Hg, CH2) it was established that participation of the Hg bridging atom in intramolecular coordination interactions with the ortho Br atom led to a reduction in the transmissability of the binuclear Hg-N bridging groupings.

19F and199Hg NMR spectra of certain fluorine-containing arylmercury derivatives of acetylenes

Conclusions19F and199Hg NMR have been used to investigate the comparative influence of electronic effects of the substituents on the shielding of19F and199Hg nuclei in ArHgC-CC6H4F-4 and 4-FC6H4HgC=CR. It has been found that the shielding of the fluorine decreases and the shielding of the mercury increases with increasing electron-acceptor properties of the Ar or R, or when the change is made from toluene to pyridine. The19F and199Hg chemical shifts correlate well with the σ and σ0 Hammett constants.

19F-(1H) NMR investigation of exchange equilibria of the mercury proton type with the participation of monosubstituted acetylenes and their cyclohexylmercury derivatives

Conclusions1.Exchange equilibrium constants of the mercury-proton type in mixtures containing HC≡CC6H4F-4, HC≡CR, and their cyclohexylmercury derivatives depend appreciably on the nature of R.2.An increase in the electron-accepting ability of R led to a large destabilization of the less polar C-H bond compared with the more polar C-Hg bond.