Synthesis of Cyclometalated Palladium(II) and Platinum(II) Complexes Using 2-Substituted 8-Quinolinols Containing C-Donor Atoms and Steric Interaction between the Ligands

Abstract

Cyclometalated complexes of 2-substituted 8-quinolinols possessing two or three carbon side chains have been prepared in the presence of a second ligand. The 5,5- or 5,6-chelate ring system containing a Pd(II)- or Pt(II)-C(sp³) bond is very stable. There are notable steric interactions among three adjacent substituents. The X-ray structure analysis of the complex containing a bulky second ligand, such as PPh₃, reveals a remarkable distortion within the Pd-coordination plane. The steric repulsion was observed also in solution by ¹H-NMR spectroscopy. A novel cyclometalated palladium complex of 3′-azido-3′-deoxythymidine (AZT) was prepared and the steric interaction was investigated by H-H COSY analysis.