Synthesis And Catalytic Properties Of Mono-and Dinuclear Aluminum Complexes

Polycaprolactone (PCL) is a kind of biopolymer materials, mainly synthesized by ring-opening polymerizations (ROP) initiated by metal complexes. This polymer has been applied widely in biomedical and pharmaceutical industry, not only due to its good biocompatibility which results in that the cells can grow in the base frame, but also due to its permeable and biodegradable properties. In recent years, researchers have developed various kinds of metal complexes, while the catalytic systems which have high activity and can control well upon the polymerization are still rare. Some catalytic systems are toxic and expensive, which limit the application of polycaprolactone in biomedical and pharmaceutical fields. Therefore, the investigation of catalytic systems with low toxicity and good bio-compatibility have very important significance.This thesis reports the preparation of11new N-aliphatic-β-ketiminate and diketiminate aluminum complexes by using low-toxic and abundant aluminum metal, and the examination of their catalytic activities in the ROP of ε-caproolactone (ε-CL). The details are as follows:a series of N-aliphatic-β-ketiminate aluminum complexes NacacRAlEtCl (R=tBu,2a;iPr,2b; CH3,2c), N-aliphatic-β-ketiminate aluminum complexes NacnacRAlEtCl (R=tBu,3c;iPr,3d; Bn,3e), NacnacRAl(CH2SiMe3)Cl(R=tBu,4a;iPr,4b), and oxo-bridged dinuclear aluminum complexes [NacnacRAlEt]2(μ-O)(R=tBu,5a;iPr,5b),[NacnaciPrAlCl]2(μ-O)(5c) were prepared, these complexes have been characterized by1H NMR,13C NMR, EI-HR MS and complex5a has been confirmed by X-ray structure determination.The obtained thirteen aluminum complexes all can initiate the ROP of ε-CL. Among the examined complexes, complex4a shows the highest catalytic activity with98%conversion within10min at80℃, and the received polymer has a narrow distribution (PDI=1.06) and a high molecular weight (Mn=4.12×104).