Ti Group Metallocene-Catalyzed Synthesis of 1-Hexene Dimers and Tetramers |
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| Authors: | Pavel V Kovyazin Almira Kh Bikmeeva Denis N Islamov Vasiliy M Yanybin Tatyana V Tyumkina Lyudmila V Parfenova |
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| Institution: | Institute of Petrochemistry and Catalysis of Russian Academy of Sciences, Prospekt Oktyabrya, 141, 450075 Ufa, Russia; (P.V.K.); (A.K.B.); (D.N.I.); (V.M.Y.); (T.V.T.) |
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| Abstract: | 1-Hexene transformations in the catalytic systems L2MCl2–XAlBui2 (L = Cp, M = Ti, Zr, Hf; L = Ind, rac-H4C2THInd]2, M = Zr; X = H, Bu i) and Cp2ZrH2]2-ClAlR2 activated by MMAO-12, B(C6F5)3, or (Ph3C)B(C6F5)4] in chlorinated solvents (CH2Cl2, CHCl3, o-Cl2C6H4, ClCH2CH2Cl) were studied. The systems Cp2ZrH2]2-MMAO-12, Cp2ZrH2]2-ClAlBui2-MMAO-12, or Cp2ZrCl2-HAlBui2-MMAO-12 (B(C6F5)3) in CH2Cl2 showed the highest activity and selectivity towards the formation of vinylidene head-to-tail alkene dimers. The use of chloroform as a solvent provides further in situ dimer dimerization to give a tetramer yield of up to 89%. A study of the reaction of Cp2ZrH2]2 or Cp2ZrCl2 with organoaluminum compounds and MMAO-12 by NMR spectroscopy confirmed the formation of Zr,Zr-hydride clusters as key intermediates of the alkene dimerization. The probable structure of the Zr,Zr-hydride clusters and ways of their generation in the catalytic systems were analyzed using a quantum chemical approach (DFT). |
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| Keywords: | metallocenes metal hydrides dimerization nuclear magnetic resonance density functional theory |
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