Homochiral metal complexes for biodegradable polymer synthesis
Chapter One introduces the principle of alkoxide and phosphine oxide as ligands for lanthanides and electropositive metals, ligand self-recognition, stereoselective polymerisation of lactide, fixation of CO2 and finally copolymerisation of CO2 and epoxide. Chapter Two shows the synthesis of the proligands rac-HLR (a racemic phosphine oxide-alkoxide, A, where R = tBu, Ph or C6H3-Me-3,5) and explores the resolution into diastereomeric RRR- and SSS-M(LR)3 to afford C3–symmetric M(LR)3 complexes, B (where M = Sc, Lu, Y, In, Bi or La). It also demonstrates that the process is under thermodynamic control and driven by ligand self-recognition via the synthesis of bis(LR) adducts (LR)2MX, C, (where M = Y or In and X = N(SiMe3)2 or OC6H3-tBu2-2,6) and mono(LR) adducts (LR)MX2, D (where M = Al or In and X = N(SiMe3)2, CH2SiMe3 or Me). Finally, it outlines the fixation of CO2 into an indiumamide bond. Chapter Three contains a detailed investigation of the potential of the MIII complexes as initiators for the stereoselective polymerisation of lactide, - caprolactone, glycolide and copolymerisation of lactide and -caprolactone, lactide and glycolide and CO2 and epoxide. Chapter Four investigates the use of rac-HLtBu in the resolution into diastereomeric RR- and SS-M(LtBu)2 complexes, E (where M = Ca, Zn or Sn), and of rac-HLPh into [M(LR)2]2 complexes, F (where M = Mg, Co or Sn and R = Ph or C6H3-Me-3,5) and mono-(LtBu) adducts (LtBu)MgX, G (X = N(SiMe3)2 or OC6H3-tBu2-2,6). It also describes the synthesis of protonated MII complexes (HLR)MCl2, H (where M = Mg, Zn or Sn and R = tBu or Ph). Finally, it details the polymerisation of lactide and its copolymerisation with glycolide using MII complexes as initiators. Chapter Five gives full experimental details and analytical data for the herein described novel compounds.