(DMP)DAB–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.