Electron spin resonance studies of ziegler-natta-type catalysts. The complex derived from dichlorobis (η-cyclopentadienyl) vanadium (Cp2VCl2) with ethylaluminium sesquichloride to polymerize ethylene

The reaction between Cp₂VCl₂ (Cp = η-cyclopentadienyl) in CH₂Cl₂ and Et₃Al₂Cl₃ or Et₂AlCl in η-heptane yields three paramagentic species giving the ESR parameters a_γ = 4.11 mT, g = 1.991 (I); a_γ = 7.46 mT, g = 1.982 (II); a_γ = 7.398 mT, g = 1.985 (III). Ethylene was polymerized using these catalysts; the solution was examined by the electron spin resonance technique before the polymerization and during the course of the reaction. The catalyst activity decayed quickly, and the mechanism of the reaction is discussed.