DMPDAB–Pd–MAH: A Versatile Pd(0) Source for Precatalyst Formation, Reaction Screening, and Preparative-Scale Synthesis

We report an easily prepared and bench-stable mononuclear Pd(0) source stabilized by a chelating N,N′-diaryldiazabutadiene ligand and maleic anhydride: DMPDAB–Pd–MAH. Phosphine ligands of all types, including bidentate phosphines and large-cone-angle biarylphosphines, rapidly and completely displace the diazabutadiene ligand at room temperature to give air-stable Pd(0) phosphine complexes. DMPDAB–Pd–MAH itself is readily soluble and stable in several organic solvents, making it an ideal Pd source for in situ catalyst preparation during reaction screening as well as solution-dispensing to plate-based reaction arrays for high-throughput experimentation. Evaluation of DMPDAB–Pd–MAH alongside other common Pd(0) and Pd­(II) sources in microscale reaction screens reveals that DMPDAB–Pd–MAH is superior at identifying hits across six different C–N, C–C, and C–O coupling reactions. DMPDAB–Pd–MAH, and the phosphine precatalysts derived therefrom, are also effective in preparative-scale cross-couplings at low Pd loadings.