На сайте журнала Applied Organometallic Chemistry   (IF=4,015) опубликована статья  с участием сотрудников Института д.х.н. И.И. Олейника (в.н.с, ЛЭАСМ) и  к.х.н. И.В. Олейник (с.н.с, ЛЭАСМ) 

Boosting activity, thermostability, and lifetime of iron ethylene polymerization catalysts through gem-dimethyl substitution and incorporation of ortho-cycloalkyl substituents

Randi Zhang, Mingyang Han, Irina V. Oleynik, Gregory A. Solan, Ivan I. Oleynik, Yanping Ma, Tongling Liang, Wen-Hua Sun

Applied Organometallic Chemistry,  
Online Version of Record before inclusion in an issue, e6376

Abstract

Six types of ferrous chloride complex, [2-(ArN=CMe)-8-(ArN)-7,7-Me₂C₉H₆N]FeCl₂ (Ar=2-(C₅H₉)-6-MeC₆H₃ Fe1, 2-(C₆H₁₁)-6-MeC₆H₃ Fe2, 2-(C₈H₁₅)-6-MeC₆H₃ Fe3, 2-(C₅H₉)-4,6-Me₂C₆H₂ Fe4, 2-(C₆H₁₁)-4,6-Me₂C₆H₂ Fe5, 2-(C₈H₁₅)-4,6-Me₂C₆H₂ Fe6), each bearing a gem-dimethyl-substituted N,N,N-chelating ligand that differs in the ortho-cycloalkyl ring size and para-substituent of the N-aryl groups, are disclosed. All complexes have been prepared by a straightforward one-flask route and characterized by FT-IR spectroscopy and elemental analysis. In the case of Fe1, oxidation to form the oxo-bridged diferric species [2-(2-(C₅H₉)-6-MeC₆H₃N=CMe)-8-(2-(C₅H₉)-6-MeC₆H₃N)-7,7-Me₂C₉H₆N]FeCl(μ-O)FeCl₃ (Fe1') has been demonstrated and its structural identity confirmed by single crystal X-ray diffraction. Following treatment with either methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), Fe1–Fe6 exhibited optimal catalytic activities at 60°C for ethylene polymerization [up to 2.35 × 10⁷ g of PE (mol of Fe)⁻¹ h⁻¹ for Fe1/MMAO] producing linear polyethylene; even over prolonged run times, high activities were maintained. Moreover, this family of iron catalysts exhibited remarkable thermostability by displaying appreciable activity at temperatures as high as 100°C [activity up to 7.8 × 10⁶ g of PE (mol of Fe)⁻¹ h⁻¹]. By varying the ring size of the ortho-cycloalkyl and para-R² group (R² = H, Me), excellent control over molecular weight of the polyethylenes could be achieved with values in the range 1.4–67.8 kg mol⁻¹ obtainable. In addition, end-group analysis of the polymers generated with Fe/MAO or Fe/MMAO revealed that both β-H elimination and chain transfer to aluminum are competitive processes during chain termination.

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