Co-ordination chemistry of 2-phenyl-6-(2-thienyl)pyridine and 2,6-bis(2-thienyl)pyridine; new ambidentate ligands

Abstract

The new ligands 2-phenyl-6-(2-thienyl)pyridine (H₂pthpy) and 2,6-bis(2-thienyl)pyridine (H₂bthpy) exhibit a variety of reactivities with d⁸ transition-metal complexes. Reaction of H₂bthpy with platinum(II) gives complexes in which the ligand adopts Hbthpy-C,N and bthpy-CNC bonding modes, whereas gold(III) converts the ligand into the dimer 5,5′-bis[6-(2-thienyl)-2-pyridyl]-2,2′-bithiophene. Palladium(II) gives mixtures of cyclometallated complexes and dimerised ligand. In contrast, H₂pthpy reacts with platinum(II) to give metallated complexes in which the site of metallation is the phenyl rather than the thienyl ring. The reaction of H₂pthpy with gold(III) results in clean conversion into the dimer 5,5′-bis(6-phenyl-2-pyridyl)-2,2′-bithiophene and a chlorinated derivative 2-(5-chloro-2-thienyl)-6-phenylpyridine. Once again mixtures of metallated product and ligand reaction products are obtained with palladium(II).