Synthesis
and Structural Analysis of (Imido)Vanadium(V) Complexes Containing
Chelate (Anilido)Methyl-imine Ligands: Ligand Effect in Ethylene Dimerization
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Abstract
A series
of (imido)vanadium dichlorido complexes containing chelate anionic
donor ligands of the type, VCl<sub>2</sub>(L)(NR) [R = 1-adamantyl
(Ad), L = 2-(2,6-Me<sub>2</sub>C<sub>6</sub>H<sub>3</sub>)NCH<sub>2</sub>(C<sub>9</sub>H<sub>6</sub>N) (<b>2</b>), 8-(2,6-Me<sub>2</sub>C<sub>6</sub>H<sub>3</sub>)NCH<sub>2</sub>(C<sub>9</sub>H<sub>6</sub>N) (<b>3</b>); L = 2-(2,6-R′<sub>2</sub>C<sub>6</sub>H<sub>3</sub>)NCH<sub>2</sub>(C<sub>5</sub>H<sub>4</sub>N),
R = 2-MeC<sub>6</sub>H<sub>4</sub>, R′ = Me (<b>4a</b>), <sup><i>i</i></sup>Pr (<b>4b</b>); L = 2-(2,6-Me<sub>2</sub>C<sub>6</sub>H<sub>3</sub>)NCH<sub>2</sub>(C<sub>5</sub>H<sub>4</sub>N), R = 4-MeC<sub>6</sub>H<sub>4</sub> (<b>5</b>), 3,5-Me<sub>2</sub>C<sub>6</sub>H<sub>3</sub> (<b>6</b>)], have been prepared
and identified. The reactions with ethylene by <b>2</b>,<b>3</b> in the presence of methylaluminoxane (MAO) afforded a mixture
of high molecular weight polyethylene and oligomers. Reactions with
ethylene by VCl<sub>2</sub>[2-(2,6-R′<sub>2</sub>C<sub>6</sub>H<sub>3</sub>)NCH<sub>2</sub>(C<sub>5</sub>H<sub>4</sub>N)](NAd)
(<b>1a,b</b>), <b>4</b>–<b>6</b> afforded
1-butene with high selectivities (>92%), and the activities by <b>4a</b>,<b>b</b> are at the same level as those in <b>1a</b>,<b>b</b>. The activities by <b>5</b>,<b>6</b> were lower than <b>4a</b>,<b>b</b> and were
at the same level of that by VCl<sub>2</sub>[2-(2,6-Me<sub>2</sub>C<sub>6</sub>H<sub>3</sub>)NCH<sub>2</sub>(C<sub>5</sub>H<sub>4</sub>N)](NPh). These results thus suggest that both the chelate anionic
donor and the imido ligands play a role for both the activity and
the selectivity
