5 research outputs found
Ethylene Homopolymerization and Ethylene/1-Butene Copolymerization Catalyzed by a [1,8-C 10
M11 FUNCTIONAL ANALYSIS OF GENOME EDITED MICE MODELING DE NOVO MUTATIONS FOUND IN PATIENTS WITH BIPOLAR DISORDER
Zirconium and Hafnium Complexes with Cycloheptane- or Cyclononane-Fused [OSSO]-Type Bis(phenolato) Ligands: Synthesis, Structure, and Highly Active 1‑Hexene Polymerization and Ring-Size Effects of Fused Cycloalkanes on the Activity
Zirconium and hafnium
complexes bearing cycloheptane- or cyclononane-fused
[OSSO]-type bisÂ(phenolato) ligands ([C7] and [C9], respectively) were
prepared and subjected to the polymerization of 1-hexene as the precatalyst.
The polymerizations produced polyÂ(1-hexene)Âs with high activities
and high isospecificity, where complexes bearing [C9] were more reactive
than those bearing [C7]. Their activities were compared with those
of the corresponding complexes bearing cyclohexane- and cyclooctane-fused
ligands ([C6] and [C8], respectively), which we reported previously,
to show the order of activity [C8] > [C9] > [C7] > [C6].
The ring-size
effect on the activity was investigated with the help of DFT calculations
on active and dormant cationic zirconium species, π complexes
of the active species with propene, and transition states for propene
insertion into the Zr–CÂ(<i>i</i>Bu) bond. The order
of activity speculated from the activation energy, that is the energy
difference between the π complex and the corresponding transition
state, was [C8] > [C7] > [C9] ≈ [C6]. However, calculations
on active and dormant cationic zirconium complexes including [BÂ(C<sub>6</sub>F<sub>5</sub>)<sub>4</sub>]<sup>−</sup> as the counteranion
revealed that the active species are more stable than the dormant
species by 9.1 kcal mol<sup>–1</sup> for [C8] followed by 7.4
kcal mol<sup>–1</sup> for [C9] and 3.1 kcal mol<sup>–1</sup> for [C7] and, in contrast, that the active species with [C6] is
less stable by 1.0 kcal mol<sup>–1</sup> than the corresponding
dormant species. Thus, the abundances of active species bearing [C6]
and [C7] are reduced, which leads to the reversal of the order of
[C7] and [C9] on the basis of activation energy to reproduce the order
observed experimentally
Zirconium and Hafnium Complexes with Cycloheptane- or Cyclononane-Fused [OSSO]-Type Bis(phenolato) Ligands: Synthesis, Structure, and Highly Active 1‑Hexene Polymerization and Ring-Size Effects of Fused Cycloalkanes on the Activity
Zirconium and hafnium
complexes bearing cycloheptane- or cyclononane-fused
[OSSO]-type bisÂ(phenolato) ligands ([C7] and [C9], respectively) were
prepared and subjected to the polymerization of 1-hexene as the precatalyst.
The polymerizations produced polyÂ(1-hexene)Âs with high activities
and high isospecificity, where complexes bearing [C9] were more reactive
than those bearing [C7]. Their activities were compared with those
of the corresponding complexes bearing cyclohexane- and cyclooctane-fused
ligands ([C6] and [C8], respectively), which we reported previously,
to show the order of activity [C8] > [C9] > [C7] > [C6].
The ring-size
effect on the activity was investigated with the help of DFT calculations
on active and dormant cationic zirconium species, π complexes
of the active species with propene, and transition states for propene
insertion into the Zr–CÂ(<i>i</i>Bu) bond. The order
of activity speculated from the activation energy, that is the energy
difference between the π complex and the corresponding transition
state, was [C8] > [C7] > [C9] ≈ [C6]. However, calculations
on active and dormant cationic zirconium complexes including [BÂ(C<sub>6</sub>F<sub>5</sub>)<sub>4</sub>]<sup>−</sup> as the counteranion
revealed that the active species are more stable than the dormant
species by 9.1 kcal mol<sup>–1</sup> for [C8] followed by 7.4
kcal mol<sup>–1</sup> for [C9] and 3.1 kcal mol<sup>–1</sup> for [C7] and, in contrast, that the active species with [C6] is
less stable by 1.0 kcal mol<sup>–1</sup> than the corresponding
dormant species. Thus, the abundances of active species bearing [C6]
and [C7] are reduced, which leads to the reversal of the order of
[C7] and [C9] on the basis of activation energy to reproduce the order
observed experimentally