A Persistent Phosphanyl‐Substituted Thioketyl Radical Anion

Alkali metal salts, M(+)[Ter(iPr)P−C(=S)−P(iPr)(2)S](.−) (M=Na, K; 2_M; Ter=2,6‐bis‐(2,4,6‐trimethylphenyl)phenyl) 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.