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The reactions of styrene and 1-hexene with zirconacyclopropane and the bimetallic five-membered Comparative analysis was carried out for the energy characteristics of alternative pathways in the reaction of styrene or 1-hexene with the intermediates, implying different orientations of the substrates towards the Zr-C bond. The obtained data were used to elucidate the reasons for the observed dependence of the reaction regioselectivity on the substrate structure and the minor by-products formation. The applicability of M06-2X/cc-pVTZ-PP//M06-2X/cc-pVDZ-PP and PBE/3ζ methods for the description of the available experimental data was shown.

1-Hexene transformations in the catalytic systems L2MCl2–XAlBui2 (L = Cp, M = Ti, Zr, Hf; L = Ind, rac-H4C2[THInd]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).

A mechanism of α-olefin cycloalumination by AlEt3 in the presence of Cp2ZrCl2 catalyst was proposed, based on theoretical estimation of the thermodynamic and activation parameters of the possible reaction pathways calculated at the DFT level using the PBE/3ζ and M06-2X/cc-pVDZ quantum chemical methods. The reaction steps to bimetallic Zr,Al- and Zr,Zr-complexes, [Cp2Zr­(μ-Cl)­CH2CH2­AlEt2], [Cp2Zr­(μ-H)­CH2CH2­AlEt2], and [Cp2Zr­(Cl)­CH2CH2­Zr­(Cl)­Cp2], observable on the NMR time scale were considered. Among the possible intermediates, zirconacyclopropane was proposed as the catalyst species most active toward the alkenes, whose formation goes via two-step ligand exchange between Cp2ZrCl2 and AlEt3, and subsequent ethane elimination from the Cp2ZrEt2. The reaction of zirconacyclopropane with the alkene gives the zirconacyclopentane intermediate, in which transmetalation by ClAlEt2 and AlEt3 gives 1-ethyl-3-alkyl­alumolanes via 2-substituted dialuminobutane.

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