PROPERTIES AND REACTIVITY OF ELECTROPHILIC OLEFINS AND QUINODIMETHANES.

Abstract

This work involves a three part study concerning the synthesis and reactivity of quinodimethanes, the determination of reduction potentials of electrophilic olefins, and the crystal structure determination of a new charge transfer complex. Treatment of p-xylylene dicyanide (10) with NaH and dimethyl carbonate in glyme yielded a,a'-bis(methoxycarbonyl)-p-xylylene dicyanide (11a), 82% yield. Oxidation of 11a with N-chlorosuccinimide and triethyl amine in acetonitrile at 0° gave 7,8-di(methoxycarbonyl)-7,8-dicyanoquinodimethane (12a), 64% yield, d. 268°. This quinodimethane homopolymerizes spontaneously and forms a Wurster complex with tetramethyl-p-phenylenediamine and a blue-black CT-complex with tetrathiafulvalene. Cyclic voltammetry reduction potentials (E^(Red)(,p)) UV absorptions and ¹H-NMR chemical shift data of 22 olefins compounds were measured. The sequence for the ability to stabilize the ethylenic radical anion was found to be (diagram omitted) > -CN >-CO₂CH₃ > Cl > Br > H as expected. An inverse relationship between chemical reactivity and reduction potential was found for tetramethyl ethylenetetracarboxylate (25) and the triester derivative (33). Although 25 has a lower E^(Red)(,p) (-1.30v) than 33, it is less reactive toward polymerization. A linear correlation of E^(Red)(,p) and Hammett substituent constants was seen for the substituted maleic anhydrides and cyanofumarates. No correlations were seen for sterically crowded derivatives of 33. The crystal structure of tetrathiafulvalinium dimethyl dicyanofumarate was determined from a single crystal X-ray study. The crystal belongs to the monoclinic space group P2₁/C with two complexes per unit cell with cell constants a = 11.075(2) Å, b = 11.615(3) Å, c = 6.623(4) Å, α = 95.7°(16), V = 847.6(9) ų. The structural parameters have been refined to convergence, R = 0.0492 and R(,w) = 0.0614.