Reactions of radical anions. Part XVII. The reactions of triphenylphosphine oxide with alkali metals in ethereal solvents

Abstract

The reactions of alkali metals with dilute solutions (⩽10^–3M) of triphenylphosphine oxide in dimethoxyethane (DME), tetrahydrofuran (THF), and 2-methyltetrahydrofuran (MTHF) have been studied. In DME and THF, reaction with potassium or rubidium, produces paramagnetic products with well-defined e.s.r. spectra. The structure and formation of these radical anions are consistent with the following mechanism: Ph₃PO + 2M → M⁺Ph₂O + PhM, M + Ph₂O + M → M⁺(M⁺Ph₂O)[graphic omitted](M = K or Rb) Only one alkali-metal splitting-constant was observed and this is attributed to the alkali metal attached to the phosphorus atom. The alkali-metal splitting-constant is consistent with an ionic MP bond. When M = Na. the behaviour was found to be anomalous. In MTHF no radical anions could be found for any of the alkali metals.

Variation of the temperature, solvent, or alkali metal results in a change in the phosphorus coupling constants when K⁺ and Rb⁺ are the gegenions.