Palladium and rhodium complexes containing 1,3-bis(oxazolinyl)propyl (Probox) ligands: Macrocycles and pincer compounds

New chiral 1,3-bis(4R-phenyl-2-oxazolinyl)propane (ProboxPh) and achiral 1,3-bis(4,4-dimethyl-2-oxazolinyl)propane (ProboxMe2) ligands have been prepared by Cd(OAc)2-catalyzed condensation reactions. These ligands, and the known isopropyl derivative ProboxiPr, react with [PdCl2(NCPh)2] and [RhCl(η2-C8H14)2]2 to form 16-membered bimetallic macrocycles. Additionally, ProboxMe2 and RhCl3 react to form a new monoanionic NCN-type pincer complex (κ3-N,C,N-ProboxMe2)RhCl2. The structures of new palladium and rhodium macrocycles with the Probox ligands are confirmed by X-ray crystallography, and natural abundance 15N 2D NMR experiments prove oxazoline coordination to the metal centers in solution. Addition of a weakly donating water ligand to (κ3-N,C,N-ProboxMe2)RhCl2 gives a six-coordinate compound with a mer-Probox configuration, whereas PMe3 coordination provides a single fac coordinated Probox isomer.

Chiral and achiral 1,3-bis(oxazolinyl)propane (Probox) ligands react with [PdCl2(NCPh)2] and [RhCl(η2-C8H14)2]2 providing 16-membered macrocycles. These are the first Probox transition-metal compounds. Reaction of Probox and RhCl3 affords a new monoanionic NCN-type pincer complex. Natural abundance 15N NMR spectroscopy and X-ray crystallography provide solution and solid state structural characterization.Figure optionsDownload as PowerPoint slide