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 palladium-catalyzed 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.