One-Pot, One-Step Mn-bis(imino)pyridine Complexes through Sonochemistry

Schiff base complexes of Mn have garnered significant attention as homogeneous catalysts. Among that class of compounds, bis(imino)pyridine-supported variants feature prominently. Synthesis of these species typically entails multistep, multiday processes and often under forcing conditions to drive condensation of less favorable nucleophiles. We report the multigram-scale one-pot, one-step synthesis of bis(imino)pyridine-Mn complexes using ultrasound-assisted synthesis, or sonochemistry, via acoustic cavitation. Complexes are assembled from their ligand components (diacetylpyridine, anilines, and MnCl2·(H2O)4), without the aid of an additional acid catalyst, using methanol as a solvent, and without any effort to remove H2O, in only 30 min of reaction time. The process is additionally amenable to electron-poor fluorinated anilines, giving rise to new complexes with novel steric and electronic environments around the Mn center.