Pd(η³-1-PhC₃H₄)(η⁵-C₅H₅), an Unusually Effective Catalyst Precursor for Heck–Mizoroki and Sonogashira Cross-Coupling Reactions Catalyzed by Bis-Phosphine Palladium(0) Compounds

The compound Pd(η3-1-PhC3H4)(η5-C5H5) reacts essentially quantitatively with a variety of phosphines L to form cross-coupling catalysts of the type PdL2 and has recently been shown to be a much more effective catalyst precursor for Suzuki–Miyaura cross-coupling reactions in comparison to more commonly utilized precursors such as Pd(PPh3)4, Pd2(dba)3, and Pd(OAc)2, which do not effectively generate two-coordinate species PdL2. This advantage is expected to apply also to e.g. Heck-Mizoroki and Sonogashira cross-coupling reactions, both of which are generally believed to be catalyzed by species of the type PdL2. Therefore, comparisons of the efficacies of catalyst systems based on Pd(η3-1-PhC3H4)(η5-C5H5), Pd(PPh3)4, Pd2(dba)3, and Pd(OAc)2 are made utilizing the conventional coupling reactions of aryl halides with methyl acrylate and styrene for Heck–Mizoroki coupling and with phenylacetylene for Sonogashira coupling. As anticipated, catalyst systems based on Pd(η3-1-PhC3H4)(η5-C5H5) are found to be signifi...