Mechanochemical synthesis of half-sandwich iridium/rhodium complexes with 8-hydroxyquinoline derivatives ligands

Mechanochemistry provides a rapid, efficient route to half-sandwich iridium and rhodium complexes from [MCp*(mu-Cl)Cl](2) (M = Ir, Rh) and 8-hydroxyquinoline-2-carbaldehyde without the need for Schlenk manipulation, inert gas protection, or dry solvents. Furthermore, post-synthetic modification of the half-sandwich metal complexes has been carried out via a mechanochemical Wittig reaction between half-sandwich metal complex and phosphorus ylide. All complexes were fully characterized by H-1 and C-13 NMR spectra, infrared spectroscopy, mass spectrometry, and single-crystal X-ray diffraction method. The half-sandwich rhodium complexes exhibited high catalytic activity towards the amide synthesis between aldehyde and hydroxylamine hydrochloride (NH2OH center dot HCl) with a broad functional group tolerance.