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: (DMP)DAB-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. (DMP)DAB-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 (DMP)DAB-Pd-MAH alongside other common Pd(0) and Pd(II) sources in microscale reaction screens reveals that (DMP)DAB-Pd-MAH is superior at identifying hits across six different C-N, C-C, and C-O coupling reactions. (DMP)DAB-Pd-MAH, and the phosphine precatalysts derived therefrom, are also effective in preparative-scale cross-couplings at low Pd loadings.

Automated summary

The study introduces an easily prepared and stable mononuclear Pd(0) source that is effective for catalytic reactions and has good solubility properties.