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Polymerization of higher α‐olefins using a Cs‐symmetry hafnium metallocene catalyst. Kinetics of the polymerization and microstructural analysis

“…The less aggregated the active centers the higher is the acceleration of the polymerization reaction. In polar solvents the enhanced ion separation reduces the degree of aggregation leading to higher polymerization activities 21, 26. The same effect can be observed using bulky monomers.…”

Synthesis, Structures, and Catalytic Reactions of Ring-Substituted Titanium(IV) Complexes

“…224,225 This very simple mechanism initially proposed in the early 1960s for the traditional Z-N system is still valid for almost all of the generations of catalyst systems discussed above. [226][227][228] Referring to Scheme 88, the treatment of a solution of Cp 2 TiCl 2 in a non-coordinating solvent such as toluene with MAO results in a fast ligand exchange producing the partially alkylated compound ) molecule produces an R-agostic π-complex, where it is coordinated by the insertion of its π-bond into the metal carbon σ-bond of the bound methyl group or growing polymer chain. Regio-(stereo)selectivity of R-olefin (co)polymerization occurs at this stage by either stereogenic site control or polymer chain-end control.…”

Highly Lewis Acidic Bifunctional Organoboranes

“…[56] A dynamic process in which this µ-F wags in and out of this plane could account for the observed temperature dependence of the chemical shift for this fluorine atom in the 19 F NMR spectrum. [40] Anions with cations more amenable to olefin polymerization applications can be straightforwardly prepared by reacting 7b with various trityl derivatives Ph 3 CϪX (X ϭ OH, OMe, [57] OC 6 F 5 , [57] N 3 , NMe 2 ); the fluoride derivative is generated upon treatment of 7b with [Ph 3 C] ϩ [BF 4 ] Ϫ [Equations (9) and (10)]. These reactions are generally rapid and quantitative by NMR spectroscopy and, with the exception of X ϭ NMe 2 , the resulting trityl salts, 9؊X, are stable in solution and the solid state.…”

“…[7] For example, the C 6 F 5 group has similar σ-electron-withdrawing powers to those of Cl and F but the BϪC aryl bonds in B(C 6 F 5 ) 3 are more kinetically inert in the presence of protic agents. [8] Therefore, although B(C 6 F 5 ) 3 loses some Lewis acidity due to the front strain associated with the bulkier C 6 F 5 substituents, [9] it is more easily handled and generally as effective as BX 3 Lewis acids in terms of strength, [9,10] without the problems inherent with reactive BϪX bonds.…”