Zinc(II) Homogeneous and Heterogeneous Species and Their Application for the Ring‐Opening Polymerisation of <i>rac</i>‐Lactide

Abstract

Abstract Schiff base ligands ( L1 H– L8 H) have been prepared and complexed to Zn II centres. All eight complexes have been characterised by single‐crystal X‐ray diffraction methods, multinuclear NMR spectroscopy and elemental analysis. It was shown that for L1 H and L2 H trimetallic complexes of the form Zn 3 (OAc) 4 ( L1 – 2 ) 2 were isolated. However, for L3 H to L7 H monometallic complexes were formed, Zn( L3 – 7 ) 2 . For L8 H a trimetallic complex was also isolated with the same stoichiometry as Zn 3 (OAc) 4 ( L1 – 2 ) 2 but a different coordination motif was detected. The Schiff base ligand L1 H was anchored to silica and treated with Zn(OAc) 2 · 2H 2 O to form the heterogeneous Zn II system. This was characterised by 13 C{ 1 H} CP/MAS NMR spectroscopy. All homogeneous and heterogeneous catalysts were assessed for the ring‐opening polymerisation of rac ‐lactide at 130 °C in the absence of solvent, using unsublimed monomer. All catalysts offered good conversions and a moderate degree of control.(© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2009)