Phosphines having a 2,3,4,5-tetraphenylphenyl moiety: Effective ligands in palladium-catalyzed transformations of aryl chlorides

Three new triarylphosphines were prepared that have a 2,3,4,5- tetraphenylphenyl (TPPh) moiety on one of the phenyl rings (at the ortho, meta, or para position) of triphenylphosphine. Among them, the ortho derivative is particularly effective to utilize unactivated aryl chlorides in three different palladiumcatalyzed reactions, i.e., Suzuki-Miyaura coupling, Mizoroki-Heck reaction, and silylation with Me₃SiSiMe₃. On the other hand, the corresponding meta and para derivatives are not effective as ligands at all in these catalytic reactions. X-ray crystal structures of Pd(0) complexes having the effective phosphines (ortho derivatives) as ligands show that η²-coordination on the TPPh moiety is general and operative to realize a highly active catalyst system.