Effect of Terminal Aryloxo
Ligands in Ethylene Polymerization Using Titanatranes of the Type,
[Ti(OAr){(O-2,4‑R<sub>2</sub>C<sub>6</sub>H<sub>2</sub>)‑6-CH<sub>2</sub>}<sub>3</sub>N]: Synthesis and Structural Analysis of the
Heterobimetallic Complexes of Titanatranes with AlMe<sub>3</sub>
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Abstract
Effects of aryloxo terminal ligands and AlMe<sub>3</sub> in ethylene polymerization using a series of Ti(OAr)[{(O-2,4-R<sub>2</sub>C<sub>6</sub>H<sub>2</sub>)-6-CH<sub>2</sub>}<sub>3</sub>N]
[R = Me (<b>1</b>), <sup><i>t</i></sup>Bu (<b>2</b>); Ar = 2,6-Me<sub>2</sub>C<sub>6</sub>H<sub>3</sub> (<b>a</b>), 2,6-<sup><i>i</i></sup>Pr<sub>2</sub>C<sub>6</sub>H<sub>3</sub> (<b>b</b>), 2,6-Ph<sub>2</sub>C<sub>6</sub>H<sub>3</sub> (<b>c</b>), 2,6-F<sub>2</sub>C<sub>6</sub>H<sub>3</sub> (<b>d</b>), C<sub>6</sub>F<sub>5</sub> (<b>e</b>)] (<b>1a</b>–<b>1e</b>, <b>2d</b>,<b>2e</b>) in the
presence of methylaluminoxane (MAO) have been explored. Reactions
of <b>1b</b>,<b>1d</b>,<b>1e</b>, which showed an
increase in the activity upon addition of a small amount of AlMe<sub>3</sub>, with 1.0 equiv of AlMe<sub>3</sub> afforded heterobimetallic
Ti–Al complexes, TiMe(O-2,6-<sup><i>i</i></sup>Pr<sub>2</sub>C<sub>6</sub>H<sub>3</sub>)[(O-2,4-Me<sub>2</sub>C<sub>6</sub>H<sub>2</sub>-6-CH<sub>2</sub>)(μ<sub>2</sub>-O-2,4-Me<sub>2</sub>C<sub>6</sub>H<sub>2</sub>-6-CH<sub>2</sub>)(Me<sub>2</sub>Al-μ<sub>2</sub>-O-2,4-Me<sub>2</sub>C<sub>6</sub>H<sub>2</sub>-6-CH<sub>2</sub>)N] (<b>3b</b>) and [TiMe{(O-2,4-Me<sub>2</sub>C<sub>6</sub>H<sub>2</sub>-6-CH<sub>2</sub>)<sub>2</sub>(μ<sub>2</sub>-O-2,4-Me<sub>2</sub>C<sub>6</sub>H<sub>2</sub>-6-CH<sub>2</sub>)N}][Me<sub>2</sub>Al(μ<sub>2</sub>-OAr)] [Ar = 2,6-F<sub>2</sub>C<sub>6</sub>H<sub>3</sub> (<b>3d</b>), C<sub>6</sub>F<sub>5</sub> (<b>3e</b>)], in moderate yields, and their structures
were determined by X-ray crystallography. In contrast, the similar
reaction of <b>1a</b> (which showed a decrease in the activity
upon addition of AlMe<sub>3</sub>) yielded [Al(μ<sub>2</sub>-O-2,6-C<sub>6</sub>H<sub>3</sub>)Me<sub>2</sub>]<sub>2</sub> and
TiMe[{(O-2,4-Me<sub>2</sub>C<sub>6</sub>H<sub>2</sub>)-6-CH<sub>2</sub>}<sub>3</sub>N] as isolated forms: [Al(μ<sub>2</sub>-OC<sub>6</sub>F<sub>5</sub>)Me<sub>2</sub>]<sub>2</sub> was isolated from
the mixture in the reactions of <b>1c</b>,<b>2d</b>,<b>2e</b>. The isolated heterobimetallic complexes (<b>3b</b>,<b>3d</b>,<b>3e</b>) exhibited high catalytic activities
for ethylene polymerization in the presence of MAO, suggesting that
these bimetallic species play a role in this catalysis
