Interactions Between MgCl2 and Lewis Bases

As previously mentioned, active MgCl2 can also be obtained by contacting MgCl2 with Lewis bases. 

A great deal of data are available for ethyl benzoate (EB), since this aromatic ester is the most widely used in patent and scientific literature dealing with high yield catalysts for propylene polymerization. 

By simply contacting MgCl2 with EB, complex formation takes place through an exothermic process which, according to Keszler39), occurs in two steps. First EB is quickly adsorbed on the MgCl2 surface, then there is the formation of the effective complex. 

Examining milled and unmilled materials, Sergeev41 found effects due to an increase of the EB concentration on pure MgCl2 crystallites (decreasing size) and on the new compound (increasing size) (Fig. 16). When EB/MgQ2 = 1.0 (molar ratio), no free MgCl2 was observable. 

Chien 42) realized that the surface area deduced from the crystallite size is higher than that experimentally found, and concluded that a certain degree of agglomeration must subsist due to the action of EB. 

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