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

Autor: Marcel Culcasi, Yves Berchadsky, Gerard Gronchi, Paul Tordo
Rok vydání: 1991
Předmět:
Zdroj: The Journal of Organic Chemistry. 56:3537-3542
ISSN: 1520-6904
0022-3263
DOI: 10.1021/jo00011a018
Popis: A large number of triarylphosphines exhibiting different steric hindrance has been prepared. The pyramidalization angle α of these compounds was calculated with use of the MM2 force field and was shown to depend almost exclusively on the number of ortho substituents on the phenyl rings. In a series of isoteric (same α) phosphines, the oxidation potential correlates with the sum of the σ + Hammett parameters of the phenyl substituents. In the absence of oxygen, anodic oxidation of all the triarylphosphines bearing two o-methyl substituents on each phenyl ring is reversible and yields very persistent phosphoniumyl radicals. These radicals are easily detected by ESR in liquid solution and were shown to retain a pyramidal geometry that is significantly flattened compared to that of the parent phosphine
Databáze: OpenAIRE