- Ligand exchange processes in zirconocene dichloride-trimethylaluminum bimetallic systems and their catalytic properties in reaction with alkenes
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Ligand exchange processes in the systems L2ZrCl2-AlMe3 (L2ZrCl2: Cp2ZrCl2, (CpMe)2ZrCl2, (C5Me5)2ZrCl2, Me2SiCp2ZrCl2, Me2Si(C5Me4)2ZrCl2, rac-Me2C(2-Me-4-But-Cp)2ZrCl2, meso-Me2C(2-Me-4-But-Cp)2ZrCl2, rac-Me2C(3-But-Cp)2ZrCl2, Ind2ZrCl2, rac-H2C(Ind)2ZrCl2, rac-Me2C(Ind)2ZrCl2, rac-Me2Si(Ind)2ZrCl2, rac-C2H4(Ind)2ZrCl2, rac-C2H4(THInd)2ZrCl2, rac-Me2Si(THInd)2ZrCl2) and Cp2ZrMeCl2-n-AlMe3 (n = 1, 2) were studied by NMR spectroscopy with the goal to establish the structures and dynamic features of probable intermediates in the zirconocene-catalyzed reactions of alkenes with AlMe3. The effect of solvent, the organoaluminum compound concentration and the addition of (ClAlMe2)2 on the activation parameters of the alkyl exchange in the trimethylaluminum dimer was studied as well. The constants and activation parameters of the methyl group exchange in the monoalkyl-substituted ansa-complexes L2ZrMeCl (L2 = rac-Me2C(2-Me-4-But-Cp)2, rac-Me2C(3-But-Cp)2, rac-H2CInd2, rac-Me2CInd2, rac-Me2SiInd2, rac-H4C2Ind2) were established for the first time. The catalytic activity and chemoselectivity of zirconocenes in the reaction of alkenes with AlMe3 were evaluated and compared with the exchange and equilibrium constants of ligand exchange processes. A mechanism of the reaction was proposed.
- Parfenova, Lyudmila V.,Kovyazin, Pavel V.,Gabdrakhmanov, Vener Z.,Istomina, Galina P.,Ivchenko, Pavel V.,Nifant'Ev, Ilya E.,Khalilov, Leonard M.,Dzhemilev, Usein M.
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p. 16918 - 16937
(2019/01/03)
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- Enantioselectivity of chiral zirconocenes as catalysts in alkene hydro-, carbo- and cycloalumination reactions
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The enantioselectivity of chiral Zr catalysts L1L2ZrCl2 [L1 = L2 = 1-neomenthylindenyl (Ind*), 1; L1 = Cp, L2 = Ind* 2; L1 = Cp, L2 = 1-neomenthylindenyl-4,5,6,7-tetrahydroindenyl (Cp*) 3] in the hydro-, carbo- and cycloalumination of alkenes by organoaluminium compounds (OAC) (AlMe3, AlEt3, HAlBu2i) has been studied. It was found that OAC exhibit the most effect on the reaction chemo- and enantioselectivity. The reaction chemo- and enantioselectivity depend on the catalyst structure and reaction conditions (solvent type, catalyst concentration, temperature) as well. It is shown that the lack of asymmetric induction in the reaction of α-methylstyrene hydroalumination by HAlBu2i, catalyzed with complexes 1 or 3, is the result of the formation of Zr hydride complexes of different structures as reaction intermediates. MTPA was used as a derivatization reagent for the enantiomeric excess estimation and absolute configuration assignment of β-chiral alcohols obtained after the oxidation and hydrolysis of the reaction products. The applicability of MTPA for the assignment of the absolute configuration of the stereogenic centre in β-ethyl substituted primary alcohols and β-alkyl-1,4-butanediols is shown.
- Parfenova, Lyudmila V.,Berestova, Tatyana V.,Tyumkina, Tatyana V.,Kovyazin, Pavel V.,Khalilov, Leonard M.,Whitby, Richard J.,Dzhemilev, Usein M.
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experimental part
p. 299 - 310
(2010/06/14)
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- On study of chemoselectivity of reaction of trialkylalanes with alkenes, catalyzed with Zr π-complexes
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The influence of the organoaluminium compound nature, Zr π-ligand environment, solvent type and reagent ratio on the chemoselectivity of reactions of trialkylalanes (AlMe3, AlEt3) with alkenes, catalyzed with L2ZrCl2
- Parfenova, Lyudmila V.,Gabdrakhmanov, Vener Z.,Khalilov, Leonard M.,Dzhemilev, Usein M.
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scheme or table
p. 3725 - 3731
(2009/12/31)
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