Diastereoselective synthesis of functionally substituted alkene dimers and oligomers, catalysed by chiral zirconocenes

Zirconocene dichlorides as catalysts in alkene carbo- and cyclometalation by AlEt3: intermediate structures and dynamics

A series of zirconocenes L₂ZrCl₂ (23 examples) were studied as catalysts in the reaction of alkenes with AlEt₃. The catalyst activity and reaction chemoselectivity were found to depend on the ligand structure in the complex and the nature of the solvent. The alkyl exchange in the triethylaluminum dimer was studied by NMR spectroscopy; a solvent effect on the alkyl exchange parameters was established. In the reaction between L₂ZrCl₂ and AlEt₃, the formation of intermediates L₂ZrEtCl, L₂Zr(μ-Cl)CH₂CH₂AlEt₂, L₂Zr(μ-H)CH₂CH₂AlEt₂, and L₂Zr(μ-Cl)CH₂CH(AlEt₂)₂ was shown; the ratio of the intermediates depends on the ligand structure in the initial complex and the solvent. The exchange in the ethanediyl bridge ZrCH₂CH₂Al, proceeding via zirconocenecyclopropane structures, was demonstrated for the first time for five-membered bimetallic complexes L₂Zr(μ-Cl)CH₂CH₂AlEt₂ with ansa-ligands (L₂ = Me₂SiCp₂, H₂CInd₂, Me₂CInd₂, Me₂SiInd₂, and C₂H₄Ind₂). Five-membered bimetallic complexes were shown to participate in the formation of cyclic organoaluminum products - 3-substituted alumolanes.

Conversion of fatty acid methyl esters into dibasic esters by metathesis and their lubricant properties

Monounsaturated dibasic esters were obtained by FAME metathesis and tested for viscosity, extreme temperature and other lubricant properties. Their 2EH derivatives can produce 100% bio-derived basestocks for widespread heavy duty hydraulic fluids.

Bimetallic Zr,Zr-Hydride Complexes in Zirconocene Catalyzed Alkene Dimerization

Being valuable precursors in the production of adhesives, lubricants, and other high-performance synthetic compounds, alkene dimers and oligomers can be obtained using homogeneous zirconocene catalytic systems. Further advances in such systems require precise control of their activity and chemoselectivity, increasing both the purity and yield of the products. This relies on the process mechanism usually built around the consideration of the hydride complexes as active intermediates in the alkene di- and oligomerization; however, the majority of studies lack the direct evidence of their involvement. Parallel studies on a well-known Cp2ZrCl2-AlR3 or HAlBui2 and a novel [Cp2ZrH2]2-ClAlR2 (R = Me, Et, Bui) systems activated by methylaluminoxane (MMAO-12) have shown a deep similarity both in the catalytic performance and intermediate composition. As a result of the NMR studies, among all the intermediates considered, we proved that new Zr,Zr- hydride complexes having the type x[Cp2ZrH2∙Cp2ZrHCl∙ClAlR2]∙yMAO appear to be specifically responsible for the alkene dimerization with high yield.