Pd(η³-1-PhC₃H₄)(η⁵-C₅H₅) as a Catalyst Precursor for Buchwald–Hartwig Amination Reactions

The compound Pd(η3-1-Ph-C3H4)(η5-C5H5) (I) reacts cleanly with many tertiary phosphines L to undergo reductive elimination of PhC3H4-C5H5 and form palladium(0) species of the types PdLn (n = 2, 3), long believed to be exemplary catalysts for Suzuki–Miyaura, Heck–Mizoroki, and Sonogashira cross-coupling reactions. I has accordingly been shown to be generally much more effective for these catalytic processes than are conventional catalyst precursors such as Pd(PPh3)4, Pd2(dba)3, PdCl2, and Pd(OAc)2, in large part because I stands alone in this series for its ability to generate specifically and efficiently the desired species PdL2 in many cases. We have now investigated I as a precursor for prototypical Buchwald–Hartwig amination reactions of 4-bromo- and 4-chloroanisole with morpholine, making comparisons with Pd2(dba)3, Pd(OAc)2, and [Pd(η3-1-Ph-C3H4)Cl]2 (IV). In this work we have utilized PBut3 because of its general effectiveness, and we have also assessed XPhos and Mor-Dalphos, representatives of impo...