[NO]- and [NN]-coordination mode rhodium complexes based on a flexible ligand: synthesis, reactivity and catalytic activity

A flexible [NON]-type ligand was prepared via a stepwise method. Air-and moisture-stable LL-(N, O-coordination mode) (1) and LX-type (N, N-coordination mode) (2) rhodium(I) complexes were synthesized based on this flexible ligand under different reaction conditions. The two rhodium complexes were isolated in good yields and characterized by elemental analysis and IR and NMR spectrometry. The molecular structures of complexes 1 and 2 were confirmed by single-crystal X-ray analysis. The cationic rhodium complex was shown to be a good catalyst for the hydrogenation of acetophenone derivatives without pre-dried solvents and reagents. Good efficiency was achieved for a series of substrates with either electron-donating or electron-withdrawing groups.