Imido titanium ethylene polymerization catalysts containing triazacyclic ligands

A comprehensive account of the synthesis, properties, and evaluation of a wide range of ethylene homopolymerization catalysts derived from imido titanium compounds supported by the triazacyclic ligands Me-3[9] aneN(3) and R-3[6]aneN(3) is described (Me-3[9]aneN(3) = 1,4,7-trimethyltriazacyclononane; R-3[6]aneN(3) = 1,3,5-trimethyl- or 1,3,5-tris(n-dodecyl) triazacyclohexane). Conventional preparative-scale reactions afforded the triazacycle-supported imido titanium compounds Ti(NR)(Me-3[9]aneN(3))Cl-2 (R = Bu-t (1), 2,6-C6H3Me2, 2,6-(C6H3Pr2)-Pr-i, Ph, C6F5, or CH2Ph (6)). Solid phase-supported analogues of 1 and 6 (linked by either the macrocycle or imido ligand to a 1% cross-linked polystyrene support) and representative Me3[ 6] aneN3 solution phase systems Ti(NR)(R-3[6]aneN(3))Cl-2(R = Me or n-dodecyl) were also synthesized. At ambient temperature, solution phase Me-3[9]aneN(3) catalyst systems were more active for ethylene polymerization (methyl aluminoxane (MAO) cocatalyst) than their solid phase-supported or Me-3[6]aneN(3) analogues. A library of 41 other triazacyclononane-supported catalysts was prepared by the semiautomated, sequential treatment of Ti(NMe2)(2)Cl-2 with RNH2 and Me-3[9]aneN(3). The ethylene polymerization capabilities of 46 compounds of the type Ti(NR)(Me-3[9]aneN(3)) Cl-2 were evaluated at 100 C ( MAO cocatalyst) and compared in representative cases to the corresponding productivities at ambient temperature. Whereas either bulky N-alkyl or N-aryl imido substituents in the compounds Ti(NR)(Me-3[9]aneN(3)) Cl-2 were sufficient to give highly active catalysts at ambient temperature, only those with bulky N-alkyl groups excelled at 100 C. Polymer end group analysis indicated that polymeryl chain transfer to both AlMe3 and ethylene monomer is an active mechanism in these systems. The use of MAO pretreated with BHT-H (BHT-H) 2,6-di-tert-butyl-4-methylphenol) led to higher productivites, increased polymer molecular weights, and more polymer chain unsaturations, but productivity decreased when a large excess of BHT-H was used. The reactions of the well-defined alkyl species Ti((NBu)-Bu-t)(Me-3[9]aneN(3))Me-2, [Ti(NtBu)(Me-3[9]aneN(3))-(mu-Me)(2)AlMe2](+), and [Ti((NBu)-Bu-t)(Me-3[9]aneN(3))Me](+) with BHT-H were examined, and the aryloxide compound [Ti((NBu)-Bu-t)(Me-3[9]aneN(3))(BHT)][BArF4] was isolated (Ar-F = C6F5). The X-ray structures of Ti(NR)(Me-3[9]aneN(3)) Cl-2 (R = Bu-t, 2,6-C6H3Me2, 2,6-(C6H3Pr2)-Pr-i, Ph, C6F5) and Ti(NR)(Me-3[6]aneN(3))Cl-2 (R) 2,6-(C6H3Pr2)-Pr-i, Ph, C6F5) are reported. The perfluorophenyl imido titanium compounds both exhibit well-defined supramolecular structures based on C center dot center dot center dot F intermolecular interactions.