| Summary: | Homogeneous olefin polymerization catalysts are activated in situ with a co-catalyst ([PhN(Me)<sub>2</sub>-H]<sup>+</sup>[B(C<sub>6</sub>F<sub>5</sub>)<sub>4</sub>]<sup>−</sup> or [Ph<sub>3</sub>C]<sup>+</sup>[B(C<sub>6</sub>F<sub>5</sub>)<sub>4</sub>]<sup>−</sup>) in bulk polymerization media. These co-catalysts are insoluble in hydrocarbon solvents, requiring excess co-catalyst (>3 eq.). Feeding the activated species as a solution in an aliphatic hydrocarbon solvent may be advantageous over the in situ activation method. In this study, highly pure and soluble ammonium tetrakis(pentafluorophenyl)borates ([Me(C<sub>18</sub>H<sub>37</sub>)<sub>2</sub>N-H]<sup>+</sup>[B(C<sub>6</sub>F<sub>5</sub>)<sub>4</sub>]<sup>−</sup> and [(C<sub>18</sub>H<sub>37</sub>)<sub>2</sub>NH<sub>2</sub>]<sup>+</sup>[B(C<sub>6</sub>F<sub>5</sub>)<sub>4</sub>]<sup>−</sup>) containing neither water nor Cl<sup>−</sup> salt impurities were prepared easily via the acid–base reaction of [PhN(Me)<sub>2</sub>-H]<sup>+</sup>[B(C<sub>6</sub>F<sub>5</sub>)<sub>4</sub>]<sup>−</sup> and the corresponding amine. Using the prepared ammonium salts, the activation reactions of commercial-process-relevant metallocene (<i>rac</i>-[ethylenebis(tetrahydroindenyl)]Zr(Me)<sub>2</sub> (<b>1</b>-ZrMe<sub>2</sub>), [Ph<sub>2</sub>C(Cp)(3,6-<i><sup>t</sup></i>Bu<sub>2</sub>Flu)]Hf(Me)<sub>2</sub> (<b>3</b>-HfMe<sub>2</sub>), [Ph<sub>2</sub>C(Cp)(2,7-<i><sup>t</sup></i>Bu<sub>2</sub>Flu)]Hf(Me)<sub>2</sub> (<b>4</b>-HfMe<sub>2</sub>)) and half-metallocene complexes ([(η<sup>5</sup>-Me<sub>4</sub>C<sub>5</sub>)Si(Me)<sub>2</sub>(κ-N<i><sup>t</sup></i>Bu)]Ti(Me)<sub>2</sub> (<b>5</b>-TiMe<sub>2</sub>), [(η<sup>5</sup>-Me<sub>4</sub>C<sub>5</sub>)(C<sub>9</sub>H<sub>9</sub>(κ-N))]Ti(Me)<sub>2</sub> (<b>6</b>-TiMe<sub>2</sub>), and [(η<sup>5</sup>-Me<sub>3</sub>C<sub>7</sub>H<sub>1</sub>S)(C<sub>10</sub>H<sub>11</sub>(κ-N))]Ti(Me)<sub>2</sub> (<b>7</b>-TiMe<sub>2</sub>)) were monitored in C<sub>6</sub>D<sub>12</sub> with <sup>1</sup>H NMR spectroscopy. Stable [<b>L</b>-M(Me)(NMe(C<sub>18</sub>H<sub>37</sub>)<sub>2</sub>)]<sup>+</sup>[B(C<sub>6</sub>F<sub>5</sub>)<sub>4</sub>]<sup>−</sup> species were cleanly generated from <b>1</b>-ZrMe<sub>2</sub>, <b>3</b>-HfMe<sub>2</sub>, and <b>4</b>-HfMe<sub>2</sub>, while the species types generated from <b>5</b>-TiMe<sub>2</sub>, <b>6</b>-TiMe<sub>2</sub>, and <b>7</b>-TiMe<sub>2</sub> were unstable for subsequent transformation to other species (presumably, [<b>L</b>-Ti(CH<sub>2</sub>N(C<sub>18</sub>H<sub>37</sub>)<sub>2</sub>)]<sup>+</sup>[B(C<sub>6</sub>F<sub>5</sub>)<sub>4</sub>]<sup>−</sup>-type species). [<b>L</b>-TiCl(N(H)(C<sub>18</sub>H<sub>37</sub>)<sub>2</sub>)]<sup>+</sup>[B(C<sub>6</sub>F<sub>5</sub>)<sub>4</sub>]<sup>−</sup>-type species were also prepared from <b>5</b>-TiCl(Me) and <b>6</b>-TiCl(Me), which were newly prepared in this study. The prepared [<b>L</b>-M(Me)(NMe(C<sub>18</sub>H<sub>37</sub>)<sub>2</sub>)]<sup>+</sup>[B(C<sub>6</sub>F<sub>5</sub>)<sub>4</sub>]<sup>−</sup>-, [<b>L</b>-Ti(CH<sub>2</sub>N(C<sub>18</sub>H<sub>37</sub>)<sub>2</sub>)]<sup>+</sup>[B(C<sub>6</sub>F<sub>5</sub>)<sub>4</sub>]<sup>−</sup>-, and [<b>L</b>-TiCl(N(H)(C<sub>18</sub>H<sub>37</sub>)<sub>2</sub>)]<sup>+</sup>[B(C<sub>6</sub>F<sub>5</sub>)<sub>4</sub>]<sup>−</sup>-type species, which are soluble and stable in aliphatic hydrocarbon solvents, were highly active in ethylene/1-octene copolymerization performed in aliphatic hydrocarbon solvents.
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