Rhodium and palladium complexes of a pyridyl-centred polyphenylene derivative

2-(2'-Pyridyl)-3,4,5,6-tetraphenylpyridine 2 (HL), a ligand with both N, N-bidentate and N, N, C-terdentate coordination potential, was prepared in excellent yield by the Diels-Alder [2+4] cycloaddition of 2-cyanopyridine and tetraphenylcyclopentadien-1-one. Monometallic Pd(II) and Rh(III) complexes were formed which exhibit both types of ligand coordination (trans-[RhCl2(L)(NCMe)] 3, cis-[RhCl(L)(NCMe)(2)] PF6 4, cis-[RhCl2(HL)(2)]PF6 6, [RhCl(L)(HL)]PF6 7, [Rh(L)(2)]PF6 8, [Pd(OAc)(L)] 9 and [Pd(eta(3)-methallyl)(HL)] PF6 10). The molecular structures of the ligand and six complexes, including the chloro-bridged dimer [RhCl(L)(mu-Cl)](2) 5, were obtained by single crystal X-ray diffraction.