Investigations of the Mechanism of the Ethene Polymerization Catalyzed by the Cyclopentadienyl Chromium Complex by Density Functional Theory Methods
Abstract
The mechanism of ethene polymerization catalyzed by h5-CpCr (Cp-cyclopentadienyl) complex was studied by density functional theory (DFT) methods: LC-wPBE, M06L, MPW1K, and MPWB1K with the LANL2DZ basis set for Cr and 6-311+G(d,p) basis set for other atoms. The intermediates and transition states in the catalytic cycle concerning the trimerization and tetramerization were determined on the basis of the ground state multiplicity (quartet). Computational results show that the trimerization leading to the formation of 1-hexene encounters an average free Gibbs energy of -32.2 kJ/mol, which differs from the theoretical reference value of 88.0 kJ/mol, as well as an average activation energy of 67.2 kJ/mol, while the tetramerization encounters an average free Gibbs energy of 163.9 kJ/mol, so this polymerization is useless with the catalytic system.
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