Department of Chemistry, NIS Centre of Excellence and INSTM University of Torino, via Quarello 15, I-10135 Torino, Italy.
Dalton Trans. 2013 Sep 21;42(35):12706-13. doi: 10.1039/c3dt50603g.
The structural and electronic properties of silica-supported titanium chloride tetrahydrofuranates samples, obtained by impregnating a polymer-grade dehydroxylated silica with TiCl4(thf)2 and TiCl3(thf)3 complexes, precursors of Ziegler-Natta catalysts, are investigated by means of FT-IR, XAS, XES and diffuse reflectance UV-Vis spectroscopy, coupled with DFT calculations. The properties of the two silica-supported samples are very similar, irrespective of the starting precursor. In both cases, most of the chlorine ligands originally surrounding the Ti sites are substituted by oxygen ligands upon grafting on silica. As a consequence, the electronic properties of silica-supported Ti sites are largely different from those of the corresponding precursors, and in both cases most of the grafted Ti sites have a formal oxidation state of +4. The whole set of experimental data provide evidence that mono-nuclear Ti species are mainly present at the silica surface.
采用浸渍法将 Ziegler-Natta 催化剂的前体 TiCl4(thf)2 和 TiCl3(thf)3 配合物负载到脱羟的聚合物级硅胶上，制备了硅胶负载的四氢呋喃钛氯化物样品，通过傅里叶变换红外光谱（FT-IR）、X 射线吸收近边结构（XAS）、X 射线光电子能谱（XES）和漫反射紫外可见光谱（diffuse reflectance UV-Vis spectroscopy）以及密度泛函理论（DFT）计算对其结构和电子性质进行了研究。结果表明，无论使用哪种起始前体，两种硅胶负载样品的性质都非常相似。在这两种情况下，Ti 位周围的大部分氯配体在接枝到硅胶上时都被氧配体取代。因此，硅胶负载 Ti 位的电子性质与相应的前体有很大的不同，而且在这两种情况下，大多数接枝的 Ti 位的形式氧化态都为+4。所有的实验数据都表明单核 Ti 物种主要存在于硅胶表面。
