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]ClO4, [PdL2]ClO4 and [PdL3]ClO4, 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.

Graphical abstractThe complexes [PdL1]ClO4, [PdL2]ClO4, [PdL3]ClO4 and [PtL2]ClO4, where, for example, L1 is N,N-di(2-picolyl)cyclopentylamine, were synthesised and characterised by X-ray crystallography. The coordination geometry around the Pd(II) and Pt(II) centres were almost square-planar and the catalytic activities of the Pd(II) complexes toward MMA polymerisation were moderate.Figure optionsDownload full-size imageDownload as PowerPoint slide