Relationship of catalyst composition to catalytic activity for the polymerization of α-olefins†

Heterogeneous olefin polymerization catalysts generally consist of a transition metal compound from groups IVB or VB in combination with an organometallic compound from groups I, II, and III of the periodic table of the elements, but in some instances may contain a third component possessing at least one strongly complexing ligand atom. The composition of a coordination catalyst of this type determines both the rate of polymerization of the α-olefin and the stereoregularity of the polymer produced. In order to predict activity and stereospecificity of catalysts for the polymerization of α-olefins, data from the polymerization of propylene using catalysts of the following types were correlated: (1) titanium(III) chloride catalysts in which the organometallic component was varied, (2) coordination catalysts containinig a ligand third component in which the ligand was varied, and (3) coordination catalysts in which the transition metal component was varied.

The electronegativity of an orgariometallic compound is known to be important in determining its reactivity with ethers, hydrogen, and other reagents. Both the ionic size and the electronegativity of the central atom appear to be important in determining the utility of both the organometallic and the transition metal compounds as components for coordination catalysts. In general, organometallic and transition metal compounds having small central atoms with similar electronegativities favor the formation of stereospecific catalysts.

The present correlation has made it possible to predict the activity and stereospecificity of coordination catalysts for olefin polymerization.