Ziegler-Natta olefin oligomerization

Polymerization reactions of olefins and dienes cannot be treated here in detail. Knowledge of the early steps which occur on nickel, as in oligomerization reactions, help explain the course of polymerization reactions and particularly their stereospecific character, as in Ziegler-Natta polymerization. 

Under the reaction conditions employed, the oligomerization is living the aluminium is removed from the chain in a separate process step [2]. Further research on the Aufbau reaction led to the discovery of transition metal catalyzed olefin polymerization (Ziegler-Natta catalysis) [3]. 

Ziegler-Natta-Like Olefin Oligomerization by Alkylzirconocene... 

Over the last 50 years numerous reactions of organic compounds catalyzed by transition metal complexes have been developed (e. g., olefin oxidation -Wacker Process, hydroformylation, carbonylation, hydrogenation, metathesis, Ziegler-Natta polymerization and oligomerization of olefins) in which the reactivity of metal-carbon bonds in the active intermediate (organometallics) is crucial. 

Insertion reations of olefins into metal-carbon bonds are fundamental to catalytic oligomerization and polymerization (e.g., Ziegler-Natta systems). Furthermore, this reaction may provide a method for stereoselective formation of a carbon-carbon bond. 

In coordination polymerization, monomer forms an adduct with a transition-metal complex, and further monomer is then successively inserted between metal and carbon. Termination occurs when the metal complex splits off from the polymer or the chain is broken intentionally by hydrogenolysis. Since the initiator is restored to its original form, the process is catalytic. The most important industrial processes are Ziegler-Natta polymerizations of a-olefins and employ solid catalysts. Most catalysts for coordination polymerization are hydride complexes of transition metals. An important example is the Shell Higher Olefin Process (SHOP) for homogeneous oligomerization of ethene with a complex nickel catalyst. The molecular-weight distribution is a Schulz-Flory distribution. The rate is first order in the catalyst metal. 

On the technical scale, olefin polymerization is based on the activation of a suitable zirconocene precursor, typically Cp2ZrMe2 or Cp2ZrCl2, by a strong Lewis acid as co-catalyst. Mechanistic studies on Ziegler-Natta-like polymerization have long focused on the role of cationic alkylzirconocene species in the catalysis. There have been previous mass spectrometric studies of isolated metallocene ions in the gas phase, most notably by Richardson and co-workers. The failure to observe olefin oligomerization in this study was attributed to incomplete thermaliza-... 

Uses Catalyst component in Ziegler-Natta type systems for olefin and diene polymerizations in alkylation reactions as catalyst component in linear oligomerization and cyclization of unsat. hydrocarbons... 

Uses Catalyst component in Ziegler-Natta type systems for olefin and diene polymerizations in alkylation reactions as catalyst component in linear oligomerization and cyclization of unsat. hydrocarbons Manuf./Distrib. Akzo Nobel http //www.akzonobel.com Albemarle http //www.albemarie.com Aldrich http //www.sigma-aidrich. com... 

Oligomerization and polymerization of olefins are usually carried out in the presence of Ziegler-Natta catalysts which were discovered by Ziegler in 1953. 

---