COORDINATION CHEMISTRY OF 2-PHENYL-6-(2-THIENYL)PYRIDINE AND 2,6-BIS(2-THIENYL)PYRIDINE - NEW AMBIDENTATE LIGANDS

The new ligands 2-phenyl-6-(2-thienyl)pyridine (H-2pthpy) and 2,6-bis(2-thienyl)pyridine (H-2bthpy) exhibit a variety of reactivities with d8 transition-metal complexes. Reaction of H-2bthpy 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, H-2pthpy 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).