Palladium(II) complexes containing N,N′-bidentate imine ligands derived from picolinaldehyde and substituted anilines: Synthesis, structure and polymerisation of methyl methacrylate

Palladium(II) complexes, L_nPdCl₂ (L_n = L_A–L_I), with N,N′-bidentate imine ligands derived from picolinaldehyde and substituted anilines have been synthesized and structurally characterized. Molecular structures revealed a distorted square plane geometry around Pd(II) centre in L_nPdCl₂ (L_n = L_A–L_C) obtained via coordination with pyridine and imine nitrogens and two chloro ligands. Pd(II) complexes L_nPdCl₂ (L_n = L_A–L_I) initiate polymerisation of methylmethacrylate (MMA) in the presence of modified methylaluminoxane (MMAO). The complex L_IPdCl₂ (of which the ligand was N-furfuryl substituted) showed the highest catalytic activity for the polymerisation of MMA with an activity of 7.08 × 10⁴ g PMMA/mol·Pd·h at 60 °C. All the complexes yielded syndio-rich poly(methyl methacrylate) (PMMA) ([rr] = 0.70). Notably, the substituents on the imine moiety of the iminopyridine fragments affects the activities towards MMA polymerization, whereas the stereoselectivities remained unchanged.