Department of Inorganic, Physical and Materials Chemistry, NIS Centre of Excellence and INSTM Unità di Torino, University of Torino, Via Quarello 11, 10135 Torino, Italy.
Chemistry. 2011 Jul 25;17(31):8648-56. doi: 10.1002/chem.201100804. Epub 2011 Jun 16.
X-ray powder diffraction (XRPD), Infrared, Raman, and UV/Vis spectroscopy have been used to investigate the structural, vibrational, and optical properties of Ti and Mg chloride tetrahydrofuranates as precursors of heterogeneous Ziegler-Natta catalysts for polyethylene production; as well as their interaction compound (pro-catalyst) and the final catalyst obtained after interaction with the AlR(3) activator. Although the structure of the precursors and of the pro-catalyst were well known, that of the catalyst (obtained by reaction of the pro-catalyst with AlR(3)) was not easily obtainable from XRPD data. IR and Raman spectroscopy provided important information on tetrahydrofuran (thf) coordination and on the ν(M-Cl) region; whereas UV/Vis spectroscopy gave the direct proof on both the formal oxidation state and the coordination environment of the active Ti sites. Those presented herein are among the first direct experimental data on the structure of the active Ti sites in Ziegler-Natta catalysts, and can be used to validate the many computational studies that have been increasing exponentially in the last few decades.
X 射线粉末衍射（XRPD）、红外、拉曼和紫外/可见光谱已被用于研究 Ti 和 Mg 氯化四氢呋喃作为聚乙烯生产多相齐格勒-纳塔催化剂前体的结构、振动和光学性质；以及它们的相互作用化合物（前催化剂）和与 AlR(3)活化剂相互作用后得到的最终催化剂。尽管前体和前催化剂的结构是众所周知的，但催化剂（由前催化剂与 AlR(3)反应得到）的结构不容易从 XRPD 数据中获得。IR 和拉曼光谱提供了有关四氢呋喃（thf）配位和ν（M-Cl）区域的重要信息；而紫外/可见光谱则直接证明了活性 Ti 位的形式氧化态和配位环境。本文提供的是齐格勒-纳塔催化剂中活性 Ti 位结构的首批直接实验数据之一，可用于验证过去几十年中呈指数级增长的许多计算研究。
