Palladium-catalyzed cross coupling reactions have a major impact on the development of small molecules and materials. Over the years, various ligands have been researched with a focus on developing more active and cost-effective palladium catalyst systems. Trialkylphosphine ligands, such as tri-tert-butylphosphine, have provided effective catalysts for a variety of palladium-catalyzed cross-coupling reactions due to the steric bulk and sigma-donating properties of the alkyl substituents. Previous research within our group has focused on utilizing conformationally-flexible neopentylphosphine ligands, specifically di-(tert-butyl) neopentylphosphine (DTBNpP), tert-butyldineopentylphosphine (TBDNpP), and trineopentylphosphine (TNpP). These neopentylphosphines provide effective catalysts for cross-coupling reactions with low palladium loading and mild reaction conditions. Pre-formed palladium-ligand complexes have recently received significant attention as precatalysts. An air-stable precatalyst offers the advantage of carefully controlling the ligand to palladium/ratio, while avoiding handling air-sensitive phosphine or carbene ligands. Our group has prepared and characterized air-stable [(DTBNpP)PdCl2]2 and [(TNpP)PdCl2]2 complexes that contain the desired 1:1 Pd/L ratio for cross-coupling reactions. These novel Pd(II) dimer complexes have been applied as precatalysts for various cross-couplings of aryl halides including: Suzuki, Sonogashira, Heck,and Buchwald-Hartwig amination reactions.

Synthesis of air-stable monoligated palladium precatalysts and their applications in cross-coupling reactions

248th National Meeting (2014)

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