IR 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 deriv. (9,9-bis(1,1-dideutero-methoxymethyl)-fluorene), in the solid state, complexed with TiCl4 and MgCl2 and in the catalyst precursor. The exptl. spectra have been interpreted by means of spectroscopic correlations and theor. results from quantum chem. calcns. on selected mol. models. From exptl. and theor. 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 approx. 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 mols. 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 mols. complexed along the [110] lateral cut is proposed.

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

BRAMBILLA, LUIGI;ZERBI, GIUSEPPE;
2010-01-01

Abstract

IR 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 deriv. (9,9-bis(1,1-dideutero-methoxymethyl)-fluorene), in the solid state, complexed with TiCl4 and MgCl2 and in the catalyst precursor. The exptl. spectra have been interpreted by means of spectroscopic correlations and theor. results from quantum chem. calcns. on selected mol. models. From exptl. and theor. 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 approx. 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 mols. 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 mols. complexed along the [110] lateral cut is proposed.
2010
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11311/579260
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