Ziegler-Natta catalyst - AbsoluteAstronomy.com

A Ziegler–Natta catalyst is a catalyst used in the synthesis of polymers of 1-alkenes (α-olefins). Three types of Ziegler–Natta catalysts are currently employed:

Solid and supported catalysts based on titanium compounds. They are used in polymerization reactions in combination with cocatalysts, organoaluminum
Organometallic chemistry
Organometallic chemistry is the study of chemical compounds containing bonds between carbon and a metal. Since many compounds without such bonds are chemically similar, an alternative may be compounds containing metal-element bonds of a largely covalent character...

compounds such as triethylaluminium
Triethylaluminium
Triethylaluminium is an organoaluminium compound. This volatile, colorless liquid is highly pyrophoric, igniting immediately upon exposure to air. It is normally stored in stainless steel containers either as a pure liquid or as a solution in hydrocarbon solvents such as hexane, heptane, or ...

, Al(C₂H₅)₃.
Metallocene catalysts, combination of various mono- and bis-metallocene, in particular ansa- (or bridged) metallocene
Ansa-metallocene
An ansa-metallocene is a type of organometallic compound containing two cyclopentadienyl ligands that are linked by a bridging group such that both cyclopentadienyl groups are bound to the same metal. The link prevents rotation of the cyclopentadienyl ligand and often modifies the structure and...

complexes of Ti, Zr or Hf.