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Abstract: Transmetallation leading to formation of n-Pr–Al bond in the Cp2Zr(n-Pr)Cl–XAlBu i 2 (X = H, Cl, Bu i ) couple was studied using PBEPBE/3ζ and RI-MP2/Λ2//PBEPBE/3ζ approaches. Calculation results were corrected by taking into account of nonspecific solvent effect (toluene). Depending on the nature of organoaluminum compound, either decomposition of alkylalane self-associates (HAlBu i 2 and ClAlBu i 2 cases) or alkyl group transfer reaction from Zr to Al atom (AlBu i 3 case) could be a rate-determining step of the process. The modeling of kinetics with calculated Gibbs free energies for elementary steps of the process shows that transmetallation rates decrease in the following order: ClAlBu i 2 > HAlBu i 2 >> AlBu i 3. [Copyright &y& Elsevier]

Abstract: The reaction of mono- and disubstituted alkynes with CH2I2-R3Al (R = Me, Et, i-Bu) was studied. It was found that the reaction of alkynes with CH2I2 in the presence of Me3Al gives β-iodoethyl-substituted cyclopropanes. The use of Et3Al or i-Bu3Al affords exclusively cyclopropylic organoaluminum compounds. [Copyright &y& Elsevier]

Abstract: The stereoselective carbomagnesiation reaction of bicyclo[2.2.1]hept-2-ene, endo-tricyclo[5.2.1.02,6]deca-3,8-diene, and exo–endo-5-methylbicyclo[2.1.1]hept-2-ene with EtMgX, where X = Cl or Et, occurs in the presence of catalytic amounts of TaCl5 to give chloro- and ethyl[2-exo-(2′-norbornylethyl)]magnesiums in high yields. The multistep reaction mechanism involving norbornene and ethylene through tantalacyclopentanes as key intermediates is also postulated. DFT calculations confirm the thermodynamic preference for the resulting exo product. [Copyright &y& Elsevier]

Abstract: The monoalkylation of mixed-ring complex η 5-cyclopentadienyl-η 5-(1-neomenthyl-4,5,6,7-tetrahydroindenyl)zirconium dichloride (CpCp′ZrCl2) by lithium, magnesium and aluminum alkyls has been studied by the means of NMR spectroscopy. It is shown the reaction of CpCp′ZrCl2 with 1 eq. of RLi (R = Et, nBu) at −78 °C in toluene gives the chiral-at-zirconium complexes CpCp′ZrRCl with epimer ratio 12:1. The use of Grignard reagent (EtMgBr) reduces the epimer ratio to 3:1. The reaction of CpCp′ZrCl2 with AlEt3 in the same conditions yields two diastereomers of complex [CpCp′ZrEt(μ-Cl)·AlEt3] in a ratio 1.6:1, followed by five-membered bimetallic hydride complex [CpCp′Zr(μ-H)(CH2CH2AlEt2] with diastereomeric ratio 10:1. Cyclohexyl isocyanide (CyNC) insertion into the Zr-R bond of CpCp′ZrRCl provides the corresponding η 2-iminoacyl complexes CpCp′ZrC(R) = N(Cy)(Cl) (R = Et, nBu), which were characterized by NMR, IR spectroscopy and mass-spectrometry (MALDI/TOF). [Copyright &y& Elsevier]

Abstract: Tantalum-catalyzed reaction of organomagnesium compounds (OMCs), bearing normal alkyl radicals, with 1-alkenes to afford novel iso-alkylmagnesiums has been systematically studied for the first time. The probable mechanism of the reaction implying the intermediate formation of β,β′-dialkyl substituted tantalacyclopentanes is discussed. [Copyright &y& Elsevier]

Abstract: The paper is devoted to a study of the reaction of terminal alkene cycloalumination by AlEt3 catalyzed with neomenthylindenyl zirconium complexes (p-S)(p-S)-bis[η 5 -[1-[(1S,2S,5R)-2-isopropyl-5-methylcycloh-exyl]indenyl]]zirconium dichloride (1) or (p-S)-(η 5 -cyclopentadienyl)[η 5 -[1-[(1S,2S,5R)-2-isopropyl-5-methylcyclohexyl]indenyl]]zirconium dichloride (2). It was shown that alkene and catalyst structures, as well as solvent, affect the overall yield and enantiomeric excess of the reaction product - 3-alkylsubstituted aluminacyclopentanes. The reaction of terminal alkenes with AlEt3, catalyzed by complex 1, in hydrocarbon solvents gives predominantly S-enantiomers of cyclic organoaluminum compounds with enantiomeric excess up to 37%. Complex 2 shows smaller stereoinduction effect and provides R-enantiomers of aluminacyclopentanes with 6–26%ee. The effectiveness of selenium-containing derivatizing reagent (R)-2-phenylselenopropanoic acid for the enantiomeric excess estimation in β-alkyl-1,4-butanediols obtained from cyclic organoaluminum compounds was shown. [Copyright &y& Elsevier]

Abstract: New bimetallic complex [Cp2ZrH2 ·ClAlEt2]2 (1) was synthesized, and its reactivity in hydrometallation reaction with the following alkenes was studied: hept-1-ene, okt-1-ene, α-methylstyrene, (1S)-β-pinene, (+)-camphene. Complex 1 shows the highest reactivity among the other known Al,Zr-bimetallic complexes: [Cp2ZrH2 ·ClAlBu i 2]2 (2), [Cp2ZrH2 ·AlEt3]2 (3), [Cp2ZrH2 ·AlBu i 3]2 (4) and [Cp2ZrH2 ·HAlBu i 2] (5) as well as organoaluminium compounds (OAC): i Bu2AlH, i Bu3Al and i Bu2AlCl in presence of Zr catalysts. Chlorine containing complexes 1 and 2 appear to be more effective in alkene hydrometallation, and relative hydrometallation rates are (1S)-β-pinene⩽(+)-camphene<α-methylstyrene