Polymerisations of ɛ-caprolactone and β-butyrolactone with Zn-, Al- and Mg-based organometallic complexes

The reaction of EtAlCl2 with 1,2-{LiN(PMes2)}2C6H4 (Mes = 2,4,6-Me3C6H2) and of butyloctylmagnesium with 1,2-{NH(PPh2)}2C6H4 gave [AlEt(1,2-{N(PMes2)}2C6H4-κ2N,N′)(THF)] (1) and [Mg(1,2-{N(PPh2)}2C6H4-κ2N,N′)(THF)2] (2), respectively. Complexes 1 and 2 were fully characterised by NMR (1H, 13C, 31P) and IR spectroscopy and mass spectrometry. Complexes 1 and 2 were employed as catalysts in the polymerisation of ɛ-caprolactone, which produced polymers with a narrow molecular weight distribution. For comparison the polymerisations of ɛ-caprolactone and β-butyrolactone were carried out with the Zn complex [ZnPr{1-N(PMes2)-2-N(PHMes2)C6H4-κ2N,N′}] (3) as catalyst, which produced polymers with narrow molecular weight distributions and high molecular weights.