Synthesis And Catalytic Activities Of ?-ketiminate Aluminum Complexes

Polycaprolactone(PCL) is gaining much attention due to the environmental pollution and the limited resources during the plastic production. Its compatibility and the degradability as well as potential availability from renewable resources make PCL ideal for use in numerous biomedical and pharmaceutical applications. Currently, PCL is mainly synthesized through ring-opening polymerization (ROP) of e-caprolactone by metal catalysts. Different ligands and metal centers can both affect the activity of the catalysts. However, for the time, some disadvantage of the metal catalysts emerged, for example, expensive price and high toxicitiy. Therefore, it makes sense to find catalytic systems with low toxicity and low cost which can result in polymer with good properties.Eight N-aliphatic-?-ketiminate aluminum complexes, nacacR AlMe2 (R = Bn,2a; CH2CH2Ph,2b; Cy.2c; ad,2d; Bu,2e; CHPh2,2f), nacacR AlEt2 (R = CHPh2.2g) and nacacR AlCl2 (R = Cy.2h), were prepared and further characterized by 1H NMR, 13C NMR. HRMS spectra in this thesis. Meantime, complex 2f was also confirmed by X-ray structure determination. The experiments show that all these eight complexes can initiate the ring-opening polymerization (ROP) of e-caprolactone. Among the examined complexes, N-benzhydryl-?-ketiminate aluminum alkyl complexes have better catalytic activities, especially complex 2g, which achieves 98% monomer conversion within 1.5 hours at 80? in toluene with a monomer to metal ratio of 100:1, and the molecular weight of the resulted polymer being 9.07x104 g mol-1. Under the same condition, complex 2g reaches 94% monomer conversion after 5 min for a monomer to metal ratio of 100:1 in the presence of 1 equivalent of benzyl alcohol, together with a narrower molecular weight distribution (PDI= 1.07) of the resulting polymer.