Reactions of radical anions. Part XII. An electron spin resonance study of the radical anions of 1-phenyl-2-trimethylsilyl-, 1-phenyl-2-trimethylgermyl-, and 1-phenyl-2-t-butyl-acetylene in tetrahydrofuran including the assignment of the splitting constants of the phenyl group by deuterium substitution

Abstract

The e.s.r. spectra of the radical anions of 1-phenyl-2-trimethylsilylacetylene with Li⁺ and Rb⁺ as gegenions, 1-phenyl-2-trimethylgermylacetylene with Na⁺, K⁺, Rb⁺, and Cs⁺ as gegenions, and 1-phenyl-2-t-butylacetylene with Li⁺, Na⁺, K⁺, Rb⁺, and Cs⁺ as gegenions in tetrahydrofuran as solvent have been obtained and analysed. The splitting constants of the phenyl group have been unambiguously assigned in 1-phenyl-2-trimethylsilylacetylene using deuterium substitution. Except for the radical anion of 1-phenyl-2-trimethylgermylacetylene with lithium as gegenion, the radical anions were stable with time at –90°. On raising the temperature dimerisation occurred, and its rate in tetrahydrofuran was followed over a temperature range –90 to –40° using an e.s.r. spectrometer. Rate constants and thermodynamic constants of activation were calculated from these results.