256394-28-2Relevant academic research and scientific papers
Structure-activity correlation in titanium single-site olefin polymerization catalysts containing mixed cyclopentadienyl/aryloxide ligation
Manz, Thomas A.,Phomphrai, Khamphee,Medvedev, Grigori,Krishnamurthy, Balachandra B.,Sharma, Shalini,Haq, Jesmin,Novstrup, Krista A.,Thomson, Kendall T.,Delgass, W. Nicholas,Caruthers, James M.,Abu-Omar, Mahdi M.
, p. 3776 - 3777 (2007/10/03)
In this work, we report the synthesis of eighteen titanium cyclopentadienyl aryloxide complexes and their propagation rate constants for 1-hexene polymerization. A correlation between kp values and the underlying catalyst structures is developed using DFT-computed ligand cone angles and ion pair separation energies as structural and electronic descriptors. The correlation takes the form of an Arrhenius-like relationship where the pre-exponential factor is correlated to the ligand cone angles and the activation energy term is correlated to the ion pair separation energies. This finding is consistent with the idea that the ability of the monomer to access the metal center is a key factor affecting the reaction rate. Copyright
Formation of neutral and cationic methyl derivatives of titanium containing cyclopentadienyl and aryloxide ancillary ligation
Fenwick, Andrew E.,Phomphrai, Khamphee,Thorn, Matthew G.,Vilardo, Jonathan S.,Trefun, Christine A.,Hanna, Brigitte,Fanwick, Phillip E.,Rothwell, Ian P.
, p. 2146 - 2156 (2008/10/09)
The formation of dimethyltitanium compounds [CpTi(OAr)Me2] containing cyclopentadienyl and aryloxide ancillary ligation was analyzed. The polymerization of ethylene and γ-olefins was achieved with mixed [Cp(ArO)TiCl2] precursors trea
Ancillary aryloxide ligands in ethylene polymerization catalyst precursors
Firth, Andrea V.,Stewart, Jeffrey C.,Hoskin, Aaron J.,Stephan, Douglas W.
, p. 185 - 193 (2007/10/03)
The compounds CpTiCl2(OC6H3-i-Pr2) (1), CpTiCl(OC6H3-i-Pr2)2 (2), CpTi(R)(OC6H3-i-Pr2)2 (R=t-Bu 3, s-Bu 4, n-Bu 5, Me 6) have been prepared and characterized. Compounds 1 or 2 in the presence of 500 equivalents of methylaluminoxane (MAO) act as catalyst precursors for ethylene polymerization. While the catalysts derived from the monocyclopentadienyl complexes are much less active that the metallocenes, there is a clear enhancement in the activity of about 40% as a result of the inclusion of a second aryloxide ligand. Reactions of 1 with AlMe3 revealed stepwise formation of CpTi(Me)Cl(OC6H3-i-Pr2) 7 and CpTi(Me)2(OC6H3-i-Pr2) 8, while subsequent addition of AlMe3 afforded complete conversion to 8, with formation of the aluminum species [AlMe2(OC6H3-i-Pr2)]n 9. In contrast, the catecholate complex CpTi(O2C6H4)Cl 10 reacts with AlMe3 yielding the paramagnetic species [CpTi(O2(C6H4))·AlClMe2] 2 11. Incorporation of aryloxide ligands in modified metallocenes was readily accomplished with the preparation of Cp2ZrCl(OC6H3-i-Pr2) 12, Cp2ZrCl(OC6H5) 13, Cp2ZrMe(OC6H5) 14 and Cp2TiCl(OC6H3-i-Pr2) 15. In combination with MAO, 12, 14 and 15 effect the polymerization of ethylene with an 11% increase in activity over the parent metallocenedichlorides. The implications of the increased activity are considered. Crystallographic data are reported for 2, 3, 6, 9, 11, 12 and 13.
