Novel Pd(II) N,O-complexes: Structure and catalytic activity in Suzuki–Miyaura reactions

Two novel palladium(II) complexes, stable in air and moisture, were synthesized in high yields. Structural analysis revealed that the ligands coordinate to the palladium center in a bidentate N^O fashion, forming square-planar geometries. Their catalytic activity was evaluated under mild conditions in Suzuki–Miyaura cross-coupling reactions. Interestingly, although the complexes have slightly different bite angles, the one with a greater deviation from the ideal square-planar geometry exhibited lower catalytic activity but higher thermal stability. A comparative analysis of turnover frequencies (TOFs) at different catalyst loadings showed a decrease in TOF with increasing concentration, supporting a homogeneous catalytic pathway and suggesting possible aggregation or deactivation of the catalyst at higher loadings. These findings highlight the importance of subtle structural variations, electronic effects, and the in situ formation of reactive species in determining catalytic efficiency. This study provides valuable mechanistic and structural insights for the rational design of high-performance palladium catalysts.