Iron complexes bearing iminopyridine and aminopyridine ligands as catalysts for atom transfer radical polymerisation

A series of iron(II) complexes bearing iminopyridine and aminopyridine ligands with N-alkyl and N-aryl substituents has been synthesised. X-Ray crystal structures of n-propyl- and 2,6-diisopropylphenyl-iminopyridine derivatives reveal dinuclear structures with halide bridges; a derivative carrying a cyclododecyl imine substituent and an (alpha)-methylpyridine unit is mononuclear. In studies of their atom transfer radical polymerisation behaviour, the mononuclear iminopyridine derivative is found to catalyse the polymerisation of styrene and methyl methacrylate while the dinuclear catalysts polymerise styrene only. The aminopyridine complexes are more efficient ATRP catalysts for styrene polymerisation than their unsaturated iminopyridine relatives.