## 2 Materials and Methods  
Titanium tetrachloride (TiCl\({}_{4}\)) was used without additional purification. The divalent titanium complex with the composition [n\({}^{6}\)-BenzeneTiCl\({}_{2}\):2 AlCl\({}_{3}\)] was synthesized according to the Fisher-Hafner method [20; 21] by the reduction of TiCl\({}_{4}\) with aluminum in the presence of AlCl\({}_{3}\) in a benzene medium. The obtained complex was made in a solution using a procedure reported in ref. [22]: 1 g of a solid titanium-benzene complex was dissolved in 100 mL of benzene containing AlEt\({}_{3}\) at a concentration of 1 mmol/L for 2 h at a temperature of 70 \({}^{\circ}\)C. ESR spectra of the initial complexes are characterized by the virtually complete absence of Ti(III) ions. The soluble TiCl\({}_{3}\):nDBE complex was synthesized according to [23] by the reduction of titanium tetrachloride with hydrogen at room temperature in a 1,2-dichloroethane medium in the presence of a carbon-supported palladium catalyst and dibutyl ether (DBE). The ESR spectrum of the obtained TiCl\({}_{3}\):nDBE complex contains the signal typical for Ti(III) ions. Therewith, the concentration of isolated paramagnetic ions was 12% of the total titanium amount. After the addition of pyridine (Py/Ti = 50 (mol)), which destructs the associates of titanium compounds with the formation of soluble TiCl\({}_{3}\):nPy adducts, an isotropic ESR signal from Ti(III) was observed. The intensity of this signal corresponded to the total content of titanium. The highly dispersed MgCl\({}_{2}\)-containing support was prepared according to ref. [24] via the interaction of the organomesium compound Mg\({}_{3}\)Ph\({}_{4}\)Cl\({}_{2}\).nDBE dissolved in chlorobenzene with a mixture of Si(OEt)\({}_{4}\) and PhSiCl\({}_{3}\), at the molar ratios of Si(OEt)\({}_{4}\)/Mg = 0.25 and PhSiCl\({}_{3}\)/Mg = 0.75. Dibutyl ether, which was used to synthesize the MgCl\({}_{2}\) support, was removed by treating the support with diethyl aluminum chloride (DEAC) at a molar ratio of Al/Mg = 1.5 and repeated washing of the support with heptane. The catalysts were synthesized by depositing the calculated amount of titanium compound (1.5 wt.% titanium of the support weight) on the MgCl\({}_{2}\) support in heptane at 20 \({}^{\circ}\)C.  
To synthesize the TMC-1 catalyst, a solution of the Ti(II) complex ([n\({}^{6}\)-BenzeneTiCl\({}_{2}\):2 AlCl\({}_{3}\)]) was used. The TMC-1-2 catalyst was obtained by treating the TMC-1 catalyst with chloropentafluorobenzene (C\({}_{6}\)F\({}_{5}\)Cl) in a toluene solution for a day at a molar ratio of C\({}_{6}\)F\({}_{5}\)Cl/Ti = 20 for the oxidation of Ti(II) to Ti(III). The catalyst was then washed with heptane to remove an excess of C\({}_{6}\)F\({}_{5}\)Cl. The interaction of TMC-1 with C\({}_{6}\)F\({}_{5}\)Cl leads to the oxidation of Ti(II) to Ti(III), which is indicated by the appearance of an intense signal in the ESR spectrum, which is typical of isolated paramagnetic Ti(III) ions. The concentration of Ti(III) ions in the produced TMC-1-2 catalyst corresponds to the titanium content in the initial TMC-1 catalyst. The TMC-2 catalyst was synthesized by depositing a solution of the TiCl\({}_{3}\) nDBE complex in 1,2-dichloroethane on the MgCl\({}_{2}\) support. The TMC-3 catalyst was obtained by treating the magnesium dichloride support with TiCl\({}_{4}\) in heptane at 20 \({}^{\circ}\)C.  
After holding the reaction mixture at 60 \({}^{\circ}\)C for 1 h, all the catalysts were washed with heptane three times. The polymerization of ethylene or copolymerization of ethylene with \(\alpha\)-olefin (1-hexene) was carried out in a 1 L stainless steel reactor. The reactor was equipped with a jacket to maintain the polymerization temperature. It was also equipped with a magnetically coupled stirrer with a controlled stirring speed. A constant ethylene pressure in the reactor was maintained using an automatic feeder of ethylene.