Rhodium and palladium complexes of a pyridyl-centred polyphenylene derivative

Abstract

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]PF₆4, cis-[RhCl₂(HL)₂]PF₆6, [RhCl(L)(HL)]PF₆7, [Rh(L)₂]PF₆8, [Pd(OAc)(L)] 9 and [Pd(η³-methallyl)(HL)]PF₆10). The molecular structures of the ligand and six complexes, including the chloro-bridged dimer [RhCl(L)(µ-Cl)]₂5, were obtained by single crystal X-ray diffraction.