Structure of Donor Molecule 9,9-Bis(Methoxymethyl)-Fluorene in Ziegler-Natta Catalyst by Infrared Spectroscopy and Quantum Chemical Calculation

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• 作者：Luigi Brambilla ; Giuseppe Zerbi ; Fabrizio Piemontesi ; Stefano Nascetti ; Giampiero Morini
• 刊名：Journal of Physical Chemistry C
• 出版年：2010
• 出版时间：July 8, 2010
• 年：2010
• 卷：114
• 期：26
• 页码：11475-11484
• 全文大小：314K
• 年卷期：v.114,no.26(July 8, 2010)
• ISSN：1932-7455

文摘

Infrared vibrational spectroscopy has been used to reveal the conformations of the Ziegler−Natta catalysts internal electron donor 9,9-bis(methoxymethyl)-fluorene and its selectively deuterated derivative (9,9-bis(1,1-dideutero-methoxymethyl)-fluorene), in the solid state, complexed with TiCl₄ and MgCl₂ and in the catalyst precursor. The experimental spectra have been interpreted by means of spectroscopic correlations and theoretical results from quantum chemical calculations on selected molecular models. From experimental and theoretical data two chelating geometries of the donors with both oxygen directly interacting with Ti or Mg atoms turn out to be favorable. They can be identified by the four dihedral angles along the CH₃−(O−CH₂−R−CH₂−O)−CH₃ residue that take on conformations of approximately trans (T), gauche⁺ (G), or gauche⁻ (G′), namely, TGGT and TGG′T. We propose the TGGT conformations for the crystal phase of the donor, the TGG′T when it is complexed with TiCl₄, and both TGGT and TGG′T when complexed with MgCl₂ along the [110] lateral cut. In the precatalysts, donors molecules are complexed along the [110] MgCl₂ lateral cut and likewise the MgCl₂ complex. A model for the catalytic sites consisting of TiCl₄ species and donor molecules complexed along the [110] lateral cut is proposed.