Anodic behavior of crowded triarylphosphines. ESR study of triarylphosphoniumyl radicals, Ar3P.bul.+

摘要: A large number of triarylphosphines exhibiting different steric hindrance has been prepared. The pyramidalization angle α these compounds was calculated with use the MM2 force field and shown to depend almost exclusively on ortho substituents phenyl rings. In a series isoteric (same α) phosphines, oxidation potential correlates sum σ + Hammett parameters substituents. absence oxygen, anodic all bearing two o-methyl each ring is reversible yields very persistent phosphoniumyl radicals. These radicals are easily detected by ESR in liquid solution were retain pyramidal geometry that significantly flattened compared parent phosphine