A warning on the use of radical traps as a test for radical mechanisms: they react with palladium hydrido complexes.
Typical radical traps (galvinoxyl, TEMPO, DPPH) react with palladium hydrides, sometimes at rates competitive with those of palladium hydride catalyzed reactions that follow an insertion mechanism (for example, alkene isomerization). Thus, positive results for radical reaction tests can be misleading. The complexes with more polarizable (neutral complexes rather than cationic) and more accessible hydrides, and the less sterically protected radical traps, react faster.
Albéniz
Ana C
AC
Departamento de Química Inorgánica, Facultad de Ciencias, Universidad de Valladolid, 47005 Valladolid, Spain.
Espinet
Pablo
P
López-Fernández
Raquel
R
Sen
Ayusman
A