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

Abstract

New chiral 1,3-bis(4 R-phenyl-2-oxazolinyl)propane ( Probox Ph ) and achiral 1,3-bis(4,4-dimethyl-2-oxazolinyl)propane ( Probox Me2 ) ligands have been prepared by Cd(OAc) 2-catalyzed condensation reactions. These ligands, and the known isopropyl derivative Probox i Pr, react with [PdCl 2(NCPh) 2] and [RhCl(η 2-C 8H 14) 2] 2 to form 16-membered bimetallic macrocycles. Additionally, Probox Me2 and RhCl 3 react to form a new monoanionic NCN-type pincer complex (κ 3- N, C, N-Probox Me2)RhCl 2. 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 (κ 3- N, C, N-Probox Me2)RhCl 2 gives a six-coordinate compound with a mer-Probox configuration, whereas PMe 3 coordination provides a single fac coordinated Probox isomer.