Unsymmetrical N,C,Se-Pincer Palladium(II) Complexes Bearing Pyrimidine-Selenoether-Functionalized N -Heterocyclic Carbenes: Synthesis, Characterization, and Photocatalytic Amidation

This study reports the design and synthesis of novel unsymmetrical N,C,Se-pincer Pd(II) complexes supported by pyrimidine-selenoether-functionalized N-heterocyclic carbenes (NHCs), fully characterized by NMR spectroscopy, high-resolution mass spectrometry (HR-MS), and single-crystal X-ray diffraction (SC-XRD). These complexes function as highly effective single-component photocatalysts for the direct oxidative amidation of aldehydes with amines under visible-light irradiation in air at ambient temperature. Using 1.0 mol % catalyst loading, the protocol achieves excellent yields (up to 96%) with broad substrate scope, tolerating diverse electronic and steric properties in both aromatic aldehydes and secondary amines. This work establishes a practical and sustainable strategy for amide bond formation, highlighting the potential of selenium-integrated pincer NHCs in photoredox catalysis.