摘要
通过(CF_3CO_2)_3Ln(Ln=Nd、Y和Eu)和R^1AlR_2(R^1=H,R=i-C_4H_9;R^1=R=C_2H_5),反应首次合成和培养出Nd-Al、Y-Al和Eu-Al三种新的双金属稀土配合物和晶体,并用X射线衍射法测定出它们的晶体结构,然后再用二维波谱技术,进一步证实和完善了晶体结构中的价态和非共面现象.由此确定这三种稀土配合物分子式的通式为:[(μ-CF_3CO_2)_2Ln(μ-CF_3CHO_2)AlR_2·2THF]_2.根据实验结果还提出了通过烷基化、β-消除(或氢化)、氢转移、键合及缔合等五个步骤生成这些配合物的反应机理.这些配合物单独可使MMA和ECH催化聚合,前者可获得主要以间同结构聚合物,后者聚合催化活性较高,在极少量的ECH存在下,还可使THF开环聚合,并通过PTHF端基分析,提出了(钅羊)离子聚合反应机理.
Three new bimetallic complexes were synthesized and crystalized by reactions of (CF3CO2)3Ln with R1 AlR2(Ln = Nd and Y, R1 = H, R = i-C4H9; Ln = Eu, R = R1 = C2H5) in tetrahydrofuran solution, and their crystal structures were determined using a X-ray diffraction method. The structures and the questions on valence state and noncoplanarity in the structures were confirmed and cracked by means of 1H NMR and 13C NMR spectra, especially by 13C-1H COSY 2D NMR technique. A general formula of molecules of the three rare earth complexes was defined as follows:[(μ-CF3CO2)2Ln(μ-CF3CHO2)AlR2 · 2THF]2A mechanism on the formation of the new complexes was also proposed through the following five steps: alkylating, β-elimination (or hydrogenation), hydrogen transfer, linkage and association.Both Y-A1 and Eu-Al complexes function as a catalyst in polymerization of MMA and ECH. The polymer obtained from the first monomer is mainly syndiotactic chain structure and the polymerization of the last monomer shows higher catalytic activity. The Y-Al complex also capable of ring-opening polymerization of THF in case of adding vary small amount of ECH and a oxonium ion mechanism of THF polymerization was suggested from the analysis of THF polymer terminal.
出处
《化学学报》
SCIE
CAS
CSCD
北大核心
1995年第7期702-709,共8页
Acta Chimica Sinica
基金
国家自然科学基金
燕山石化公司联合资助的项目
