GENERATION AND CHARACTERIZATION OF DIPHOSPHENE AND TRIPHOSPHENE RADICAL ANIONS. COMPUTATIONAL STUDIES ON THE STRUCTURE AND STABILITY OF P3H3.

Complexation of the K+ ions of little soluble K2[tBuP]2·1/2THF (THF = tetrahydrofuran) with 18-crown-6 or [2.2.2]cryptand in THF leads to brown-red solutions which exhibit limited stability at room temperature. The 31P NMR spectrum consists of two singlets (1:1) which are assigned to the trans and gauche rotamers of the dianion [tBuP−PtBu]2-. That dianion undergoes a protonation by the solvent forming the monoanion [(tBu)(H)P−PtBu]-, which has been characterized by 31P NMR spectroscopy. In addition, the brown-red solutions contain a paramagnetic species, for which the EPR spectrum revealed a 1:2:1 triplet caused by the hitherto unknown diphosphene radical anion [tBuPPtBu]•- (giso = 2.0103). These reactions of the dianion [tBuP−PtBu]2- on complexation of the K+ ions occur also at −40 °C and can be attributed to a tendency to reduce the Coulombic repulsion between the adjacent negative charges. The homologous triphosphene radical anion [tBuP−(tBu)P−PtBu]•- could be generated by reduction of the cyclic triph...