Synthesis and characterisation of palladium(II) and platinum(II) complexes with N,N′,N-tridentate ligands based on N, N-di(2-picolyl) cycloalkylamine and polymerisation of methyl methacrylate

The reaction of Pd(CH₃CN)₂Cl2 and NaClO₄ with the ancillary ligands N, N-di(2-picolyl)cyclopentylamine (L1), N, N-di(2-picolyl)cyclohexylamine (L₂) and N, N-di(2-picolyl) cycloheptylamine (L₃) in ethanol yielded a new series of [(N,N′,N)-PdCl]ClO₄ complexes, i.e., [PdL₁]ClO ₄, [PdL₂]ClO₄ and [PdL₃]ClO ₄, respectively. The reaction of Pt(CH₃CN) ₂Cl₂ and NaClO₄ with the ancillary ligands L1-L3 gave only the stable [PtL₂]ClO₄ complex. The Pd and Pt atoms of all of the complexes had an almost square-planar geometry involving three nitrogen atoms and a chloro ligand. Moreover, the unit cell included a ClO4 anion as the counterion. The bond lengths between the metal and nitrogen atoms are a little affected by the substituted cycloalkyl group, however those between the metal and the chloro ligand are not affected. The catalytic activity of the Pd(II) and Pt(II) complexes toward the polymerisation of methyl methacrylate in the presence of modified methylaluminoxane resulted in a high molecular weight and a narrow polydispersity index; the highest activity was measured for [PdL₃]ClO₄ at 60 °C.