Aluminium alkyl complexes supported by [OSSO] type bisphenolato ligands: synthesis, characterization and living polymerization of rac-lactide
作者:Haiyan Ma、Gianluca Melillo、Leone Oliva、Thomas P. Spaniol、Ulli Englert、Jun Okuda
DOI:10.1039/b416875e
日期:——
Aluminium alkyl complexes [(OSSO)AlR]
(1–3: R = Me, Et) were isolated in good yields from the protonolysis reaction of AlR3 with the corresponding tetradentate 1,ω-dithiaalkanediyl-bridged bisphenols (1,4-dithiabutanediyl-bis(6-tert-butyl-4-methylphenol), etbmpH2; ortho-xylylenedithio-bis(6-tert-butyl-4-methylphenol), xytbmpH2). The monomeric structures of all three complexes were confirmed by X-ray diffraction studies. Complexes 1 and 2 have an isotypic packing arrangement. The aluminium center is coordinated by the etbmp ligand and one alkyl group with distorted trigonal bipyramidal geometry. Complex 3 shows Cs symmetry with square pyramidal geometry around the metal center. Substitution reaction of complex 1 with trityl alcohol gave the monomeric alkoxide complex [(etbmp)Al(OCPh3)]
4, which has a similar trigonal bipyramidal geometry around the aluminium atom as complex 1. In the presence of isopropanol, complexes 1–3 initiated the living ring-opening polymerization of rac-lactide (PDI = 1.03–1.06, Mw/Mn). The ligand structure influenced the tacticity of the obtained polymer, with complex 3 giving heterotactic-enriched polylactides.
通过质子解反应,从AlR3与相应四齿1,ω-二硫代烷二基桥连双酚(1,4-二硫代丁二基-双(6-叔丁基-4-甲基苯酚),etbmpH2;邻二甲苯二硫代-双(6-叔丁基-4-甲基苯酚),xytbmpH2)反应中,得到了高产率的烷基铝配合物[(OSSO)AlR](1-3:R = Me,Et)。所有三种配合物的单体结构通过X射线衍射研究得到证实。配合物1和2具有同型堆积排列。铝中心与etbmp配体和一个烷基基团配位,具有扭曲的三方双锥几何形状。配合物3显示出Cs对称性,金属中心周围具有四方锥几何形状。配合物1与三苯甲醇的取代反应得到单体烷氧化物配合物[(etbmp)Al(OCPh3)] 4,其铝原子周围具有与配合物1相似的三方双锥几何形状。在异丙醇存在下,配合物1-3启动了外消旋-乳酸的内酯开环活性聚合(PDI = 1.03–1.06,Mw/Mn)。配体结构影响了所得聚合物的构型,配合物3给出了富含异手性的聚乳酸。