AbstractThe examination of the reaction between [MgCl2(THF)2], TiCl4(3), AlCl3, AlEt3, AlEt2Cl and the synthesis and isolation of compounds as crystals and resolution of their structure by the X‐ray method were the subject of our study. It was expected that these investigations would help to understand the behaviour of MgCl2towards the transition metal and furnish useful relationships to the structure of catalyst active center and to the polymerization mechanism in TiCl4(3)/MgCl2/AlEt3system. Our studies have revealed that the main difference between the first and higher generations of Ziegler‐Natta catalysts is only the number of active cent