A Persistent Phosphanyl-Substituted Thioketyl Radical Anion

Alkali metal salts, M+ [Ter(iPr)P-C(=S)-P(iPr)(2)S](center dot-) (M = Na, K; 2_M; Ter = 2,6-bis-(2,4,6-trimethylphenyl)plzenyl) containing a room-temperature-stable thioketyl radical anion were obtained by reduction of the thioketone precursor, Ter(iPr)P-C(=S)-P(iPr)(2)S (1), with alkali metals (Na, K). Single-crystal X-ray studies as well as EPR spectroscopy revealed the unequivocal existence of a thioketyl radical anion in the solid state and in solution, respectively. The computed Mulliken spin density within 2_M is mainly located at the sulfur (49%) and the carbonyl carbon (33 %) atoms. Upon adding [2.2.2/-cryptand to the radical species 2_K to minimize the interionic interaction, an activation reaction was observed, yielding a potassium salt with a phosphanyl thioether based anion, [K(crypt)(+) [Ter(iPr)P-C(-S-iPr)-P(iPr)(2)S](-) (3) as the product of an intermolecular shift of an iPr group from a second anion. The products were fully characterized and application of the radical anion as a reducing agent was demonstrated.

Automated summary

In this study, alkali metal salts containing stable thioketyl radical anions at room temperature were synthesized by reducing the precursors with alkali metals. The existences of thioketyl radical anions in solid and solution states were confirmed by single-crystal X-ray studies and EPR spectroscopy, respectively. An activation reaction was observed, resulting in the formation of a potassium salt with a phosphanyl thioether based anion.