Pd2(dba)3 as a Precursor of Soluble Metal Complexes and Nanoparticles: Determination of Palladium Active Species for Catalysis and Synthesis

Tris(dibenzylideneacetone)dipalladium (Pd2(dba)3) is ubiquitously used as a source of soluble Pd species for catalysis and as a precursor in the synthesis of more complex Pd structures. In spite of the massive usage of this convenient Pd complex, its nature in solution has not been revealed in detail and the applications rely on the assumed state and purity of the compound. In the present study we have developed a convenient NMR procedure to reveal the nature of Pd2(dba)3 and to determine the purity of the complex. Surprisingly, it was found that commercially available samples of Pd2(dba)3 may readily contain up to 40% of Pd nanoparticles in a wide range of sizes (10–200 nm). The study has shown that the routinely accepted practice of utilization of Pd2(dba)3 without analysis of the purity (both commercially available and prepared by common procedures) can introduce significant errors in the estimation of catalyst efficiency and lead to incorrect values of TON, TOF, and reported mol % values in the cataly...