Mechanism of Cp<Subscript>2</Subscript>ZrCl<Subscript>2</Subscript>-catalyzed olefin hydroalumination by alkylalanes

The composition of intermediates of the Cp₂ZrCl₂-catalyzed hydroalumination of α-olefins by isobutylalanes (HAlBuⁱ ₂, AlBuⁱ ₃, ClAlBuⁱ ₂) was studied by dynamic ¹H and ¹³C NMR pectroscopy. The reaction of Cp₂ZrCl₂ with isobutylalanes affords the complex (Cp₂ZrHCl·HAlBuⁱ ₂)₂ responsible for α-olefin hydroalumination.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 311–322, February, 2005.     

Synthesis of 1,2,3,4-tetrasubstituted aluminacyclopent-2-enes using Cp<Subscript>2</Subscript>ZrCl<Subscript>2</Subscript> as catalyst

Efficient procedures have been developed for the synthesis of 1,2,3,4-tetrasubstituted aluminacyclopent-2-enes via intermolecular cycloalumination of terminal olefins and acetylenes with EtAlCl₂ or cycloalumination of acetylenes with higher trialkylalanes in the presence of Cp₂ZrCl₂ as catalyst.     

Cyclomagnesation of cyclonona-1,2-diene with EtMgR catalyzed by Cp<Subscript>2</Subscript>ZrCl<Subscript>2</Subscript>

Catalytic cyclomagnesation of cyclonona-1,2-diene with EtMgR (R = Et, Hlg) in the presence of catalyst Cp₂ZrCl₂ (5 mol%) was performed obtaining according to the reaction conditions either 10-magnesabicyclo-[7.3.0^1.9]dodec-8-ene or 3-ethylcyclonon-1-enyl-2-magnesiumethyl with a high regio-(>96%) and chemoselectivity (>75%).     

Joint cycloalumination of ethylene and other unsaturated compounds with EtAlCl<Subscript>2</Subscript> in the presence of Cp<Subscript>2</Subscript>ZrCl<Subscript>2</Subscript>. Synthesis of aluminacarbocycles

A procedure has been developed for the selective synthesis of five-membered aluminum-containing heterocycles, 2,3-dialkyl-1-ethylaluminacyclopent-2-enes, 3-alkyl-1-ethylaluminacyclopentanes, 2-alkylidene-1-ethylaluminacyclopentanes, and 3-alkyl-1-ethyl-2-methylidenealuminacyclopentanes, via joint cycloalumination of ethylene and other unsaturated compounds (acetylenes, olefins, and allenes) with EtAlCl₂ in the presence of Cp₂ZrCl₂ as catalyst.     

Cp<Subscript>2</Subscript>ZrCl<Subscript>2</Subscript>-Catalyzed cycloalumination of acetylenic alcohols and propargylamines by Et<Subscript>3</Subscript>Al

The Cp₂ZrCl₂-catalyzed cycloalumination of acetylenic alcohols and propargylamines by Et₃Al was studied. The process affords 2,3-disubstituted alumacyclopent-2-enes, which were identified by the analysis of the products of their deuterolysis and hydrolysis. The cycloalumination of alkyl- and phenyl-substituted propargylamines proceeds with high regio- and stereoselectivity to give the corresponding allylamine derivatives in high yield. Unlike the phenyl derivatives, the cycloalumination of alkyl-substituted acetylenic alcohols (propargyl, homopropargyl, and bishomopropargyl alcohols) is not regioselective.     

Cycloalumination of allylbenzenes with triethylaluminum in the presence of Cp<Subscript>2</Subscript>ZrCl<Subscript>2</Subscript>. One-pot synthesis of 2-benzylbutane-1,4-diols as precursors of dibenzylbutane lignans

One-pot synthesis of 2-[(hydroxy- and methoxyphenyl)methyl]butane-1,4-diols in an overall yield of 60–65% by cycloalumination of allylbenzenes (4-allyl-1-methoxybenzene, 4-allyl-1,2-dimethoxybenzene, 5-allyl-2-methoxyphenol, and 5-allyl-1,2,3-trimethoxybenzene) with triethylaluminum in the presence of Cp₂ZrCl₂ is reported for the first time. The developed procedure opens a new synthetic route to practically important β-substituted butane-1,4-diols that are precursors to dibenzylbutane lignans.     

Synthesis and transformations of metallacycles 33. The first example of cycloalumination of cyclonona-1,2-diene with Et<Subscript>3</Subscript>Al and EtAlCl<Subscript>2</Subscript> in the presence of Cp<Subscript>2</Subscript>ZrCl<Subscript>2</Subscript>

Catalytic cycloalumination of cyclonona-1,2-diene upon treatment with Et₃Al and EtAlCl₂ in the presence of Cp₂ZrCl₂, leading to 10-ethyl-10-aluminabicyclo[7.3.0^1,9]dodec-8-ene (1) and 11-ethyl-11-aluminatricyclo[10.7.0^1,12.0^2,10]nonadeca-9,12-diene, respectively, was accomplished in high yields. A possibility for the selective transformation of compound 1 to 1-allyl-9-(pent-4-enyl)cyclonon-1-ene and 10-hydroxybicyclo[7.3.0^1,9]dodec-8-ene in one preparative step was demonstrated. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2156–2159, November, 2007.     

Synthesis and transformations of metallacycles 37. Cp<Subscript>2</Subscript>ZrCl<Subscript>2</Subscript>-Catalyzed cycloalumination of substituted methylidenecyclopropane with Et<Subscript>3</Subscript>Al

Cycloalumination of substituted methylidenecyclopropanes with Et₃Al catalyzed by Cp₂ZrCl₂ affords alumaspiro[2.4]heptanes in 64–92% yields.     

Synthesis and transformations of metallacycles 36. Cycloalumination of macrocyclic diacetylenes with Et<Subscript>3</Subscript>Al catalyzed by Cp<Subscript>2</Subscript>ZrCl<Subscript>2</Subscript>

Cycloalumination of macrocyclic diynes with Et₃Al catalyzed by Cp₂ZrCl₂ resulted in unsaturated bi- and tricyclic mono- and dialuminacarbocycles in 76–91% yields.     

Synthesis and transformations of metallacycles 44. Cycloalumination of methylenecyclobutane terpene derivatives with Et3Al catalyzed by Cp<Subscript>2</Subscript>ZrCl<Subscript>2</Subscript>

Cycloalumination of methylenecyclobutane terpene derivatives (d(+)-camphor, (+)-camphene, β-pinene, and l(–)-menthol) with Et₃Al catalyzed by Cp₂ZrCl₂ produced novel spirofused organoaluminum compounds in high yields. The synthesized compounds were in situ transformed into the corresponding spiro tetrahydroselenophenes and spiro phospholanes.     

Cyclomagnesiation of nitrogen-containing 1,2-dienes with grignard compounds catalyzed by Cp<Subscript>2</Subscript>TiCl<Subscript>2</Subscript>

Cyclomagnesiation of nitrogen-containing 1,2-dienes with Grignard compounds in the presence of activated magnesium and Cp₂TiCl₂ as catalyst afforded 2,5-bis(aminoalkylidene)magnesacyclopentanes in high yield.     

Kinetics and mechanism of carbon monoxide oxidation on the supported metal complex catalyst PdCl<Subscript>2</Subscript>-CuCl<Subscript>2</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript>

The kinetics of carbon monoxide oxidation with atmospheric oxygen on a PdCl₂-CuCl₂/γ-Al₂O₃ catalyst was studied at T = 27°C and an N₂-O₂-CO mixture pressure of 1 atm. The catalyst was prepared by cold impregnation. Three groups of mechanistic hypotheses are considered, and two of them are demonstrated to be consistent with kinetic data, although they differ in the roles of water and oxygen in carbon monoxide oxidation.     

Quantum-chemical study of ytterbium fluorides and of complex F<Subscript>2</Subscript>YbF<Subscript>2</Subscript>CeF<Subscript>2</Subscript>

The structural parameters of the (²Σ⁺//C_∞v)-YbF, (¹A₁//C_2v)-YbF2, (²A₂^′//D_3h)-YbF₃, (¹Ag//D_2h)-YbF₂Yb, (¹Ag//C_2h)-FYbF₂YbF, (¹A₁//C_2v)-FYbF₂YbF, (¹A₁//C_2v)-YbF₂YbF₂, (³B_3u//D_2h)-F₂YbF₂YbF₂, (²A′//C_s)-FYbF₂YbF₂, and (³B₂//С_2v)-F₂YbF₂CeF₂ molecules have been determined. Disproportionation of ytterbium monofluoride (2YbF → YbF₂ + Yb + 0.46 eV) is less exothermic than dimerization (2YbF → YbF₂Yb + 2.10 eV). The bond energy of the ytterbium difluoride molecules in the trans dimer (2.93 eV) exceeds those in the cis dimer (2.86 eV) and the coaxial dimer (1.66 eV). Ytterbium trifluoride dimerizes exothermically (2.95 eV) without spin pairing. The dipole and quadrupole moments of the molecules as well as the charges and spin populations of the atoms and the valence electron configurations of the lanthanides have been calculated.     

Quantum-chemical study of organoxenon molecules Xe(CF<Subscript>3</Subscript>)<Subscript>2</Subscript> and FXeCF<Subscript>3</Subscript>

Charges on the atoms and structural parameters of the Xe(CF₃)₂, FXeCF₃, and XeF₂ molecules were calculated by the MP2(full)/MIDI(d₆)&6-311G(d ₆) quantum-chemical methods. The calculated energy of Xe(CF₃)₂ is greater by 113 kcal/mol than the overall energy of C₂F₆ and Xe, and the energy of FXeCF₃ is greater by 108 kcal/mol than the overall energy of CF₄ and Xe, the barrier to the decomposition being estimated at 40 kcal/mol. Both Xe(CF₃)₂ and FXeCF₃ molecules are stable with respect to spontaneous decomposition with elimination of difluorocarbene.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 40, No. 12, 2004, pp. 1808–1810.Original Russian Text Copyright © 2004 by Semenov, Sigolaev.     

Nitrosonium nitrite isomer of N<Subscript>2</Subscript>O<Subscript>3</Subscript>: Quantum-chemical data

The geometrical, electronic, and thermodynamic parameters of three known isomers of dinitrogen trioxide N₂O₃ were calculated by the density functional theory DFT/B3LYP method using the 6-311++G(3df) basis. The structure of the new isomer, NONO₂, was calculated. From the calculation of vibrational frequencies it follows that the structure of NONO₂ has a local potential energy minimum and corresponds to the stationary state of the N₂O₃ isomer. The molecular structure of NONO₂ is characterized by a substantial negative charge on the NO₂ fragment and positive charge on the NO fragment. The electronic structure of the NO⁺NO ₂ ^? isomer can be characterized as nitrosonium nitrite, which can be oxidized to nitrite and participate in nitrosylation in accordance with the biogenic characteristics of the NO _x intermediate, assumed to be formed in biological systems during the oxidation of NO.     

Quantum-chemical modeling of endohedral derivatives of buckminsterfullerenes Gd@C<Subscript>60</Subscript>(CHR)<Subscript>2</Subscript> and Gd@C<Subscript>80</Subscript>(CHR)<Subscript>2</Subscript>

The structural energies of the endohedral derivatives of buckminsterfullerenes Gd@C₆₀(CHR)₂ and Gd@C₈₀(CHR)₂ were calculated by quantum-chemical methods – semiempirical PM3 and nonempirical RHF SCF MO LCAO with the S. Huzinaga MINI minimum basis set and GAMESS software.     

Quantum-chemical modelling of nanotubes of titanium silicocarbides Ti<Subscript>2</Subscript>SiC,Ti<Subscript>3</Subscript>SiC<Subscript>2</Subscript>, and Ti<Subscript>4</Subscript>SiC<Subscript>3</Subscript>

Atomic models are proposed for nanotubes of the titanium silicocarbides Ti₂SiC, Ti₃SiC₂, and Ti₄SiC₃, and their electronic structure and interatomic interactions are investigated by the density functional tight-binding method (DFTB) in comparison with the corresponding crystalline phases. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 45, No. 2, pp. 88-92, March-April, 2009.     

Quantum-chemical study of adsorption of Ag<Subscript>2</Subscript>, Ag<Subscript>4</Subscript>, and Ag<Subscript>8</Subscript> on different parts of the TiO<Subscript>2</Subscript> surface

Quantum-chemical study of the adsorption of two-, four- and eight-atomic silver clusters on stoichiometric and partially reduced rutile (110) surface, and of silver tetramer on the surface of anatase (101) was carried out in the framework of periodic DFT model. The most energetically favorable positions of clusters on the surface of TiO₂ and the mechanism of binding the clusters with the substrate were revealed. According to the calculations, the adsorption of silver clusters on the surface of stoichiometric rutile (110) is more preferable than on the partially reduced one. The mechanism of binding the clusters with the surface of anatase and rutile is shown to be similar.