Cyclopropanation of alkenes with CH2I2/Et3Al by the phase-vanishing method based on fluorous phase screen

Phase-vanishing (PV) method using perfluorohexanes as a screen phase was applied to cyclopropanation reactions with CH₂I₂/Et₂Zn and CH₂I₂/Et₃Al. When Et₃Al was used as a carbenoid generator, the reaction proceeded smoothly and desired cyclopropane derivatives were obtained in high yield. The PV cyclopropanation took 2 or 3 days to complete, however, reduction of reaction time by a factor of 2-3 was also achieved by vigorous stirring after the bottom CH₂I₂ layer disappeared.     

RhCl3/amine-catalyzed [2+2+2] cyclization of alkynes

The RhCl₃·3H₂O/i-Pr₂NEt-catalyzed [2+2+2] cyclotrimerization of alkynes has been achieved. The reaction can be widely used for various alkynes and provides tri- or hexa-substituted benzenes regioselectively in high yields. The [2+2+2] cycloaddition of diynes and alkynes is also developed, and it affords benzene derivatives in moderate to high yields.     

Kinetics of the reactions of isopropoxy radicals with NO,NO2, and O2

A fluorescence excitation spectrum of (CH₃)₂CHO (isopropoxy radical) is reported following photolysis of isopropyl nitrite at 355 nm. Rate constants for the reaction of isopropoxy with NO, NO₂, and O₂ have been measured as a function of pressure (1–50 Torr) and temperature (25–110°C) by monitoring isopropoxy radical concentrations using laser-induced fluorescence. We have obtained the following Arrhenius expressions for the reaction of isopropoxy with NO and O₂ respectively: (1.22±0.28)×10^?11 exp[(+0.62±0.14 kcal)/RT]cm²/s and (1.51±0.70)×10^?14 exp[(?0.39±0.28)kcal/RT]cm³/s where the uncertainties represent 2σ. The results with NO₂ are more complex, but indicate that reaction with NO₂ proceeds more rapidly than with NO contrary to previous reports. The pressure dependence of the thermal decomposition of the isopropoxy radical was studied at 104 and 133°C over a 300 Torr range using nitrogen as a buffer gas. The reaction is in the fall-off region over the entire range. Upper limits for the reaction of isopropoxy with acetaldehyde, isobutane, ethylene, and trimethyl ethylene are reported.We have performed the first LIF study of the isopropoxy radical. Arrhenius parameters were measured for the reaction of i-PrO with O₂, NO, NO₂, using direct radical measurement techniques. All reactions are in their high-pressure limits at a few Torr of pressure. The rate constant for the reactions of i-PrO with NO and NO₂ reactions exhibit a small negative activation energy. Studies of the i-PrO + NO₂ reaction produce data which indicate that O(³P) reacts rapidly with i-PrO. Unimolecular decomposition studies of i-PrO indicate that the reaction is in the fall-off region between 1 and 300 Torr of N₂ and the high-pressure limit is above 1 atmosphere of N₂.     

Vibrational state analysis of unrelaxed BaI from the reactions Ba + CH3I and Ba + CH2I2

The reactions Ba + CH₃I → BaI + CH₃ and Ba + CH₂I₂ → BaI + CH₂I have been investigated by the method of laser-induced fluorescence. Excitation spectra are reported for BaI products formed under single-collision conditions in a “beam-gas” arrangement. The production of BaI for Ba + CH₂I₂ is found to be a major reaction pathway with a cross section about twice that for Ba + CH₃I. The relative vibrational populations show for both reactions bell-shaped distributions peaking close to υ = 21 for Ba + CH₃I and υ = 39 for Ba + CH₂I₂. The corresponding average fraction of the total reaction exoergicity that appears as BaI vibration is $\text{f}$_υ = 0.18 for Ba + CH₃I and $\text{f}$_υ = 0.29 for Ba + CH₂I₂. In the case of Ba + CH₃I, an estimate for the average relative translational energy of the products, obtained from the primitive angular distribution measurements of Lin, Mims and Herm, can be combined with the average vibrational excitation of BaI to provide evidence that the internal excitation of the methyl radical exceeds that of BaI. A model is discussed which postulates an electron jump in the exit valley of the Ba + CH₃I reaction to account for this feature of the reaction dynamics.     

New effective reagent [Cp2ZrH2 · ClAlEt2]2 for alkene hydrometallation

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 · ClAlBuⁱ₂]₂ (2), [Cp₂ZrH₂ · AlEt₃]₂ (3), [Cp₂ZrH₂ · AlBuⁱ₃]₂ (4) and [Cp₂ZrH₂ · HAlBuⁱ₂] (5) as well as organoaluminium compounds (OAC): ⁱBu₂AlH, ⁱBu₃Al and ⁱBu₂AlCl 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 < oct-1-ene < hept-1-ene. Hydrometallation of (1S)-β-pinene and its subsequent oxidation with I₂ run with high diastereoselectivity and yield trans-myrtanol. However, the diastereoselectivity of (+)-camphene hydrometallation is less than that for (1S)-β-pinene, and the reaction gives predominately endo-camphanol.     

Pd2dba3/P(i-BuNCH2CH2)3N: a highly efficient catalyst for the one-pot synthesis of trans-4-N,N-diarylaminostilbenes and N,N-diarylaminostyrenes

A Pd₂dba₃/P(i-BuNCH₂CH₂)₃N catalyzed one-pot synthesis of unsymmetrically substituted trans-4-N,N-diarylaminostilbenes and both symmetrically and unsymmetrically substituted N,N-diarylaminostyrene derivatives is reported. The procedure involves two or more palladium catalyzed sequential coupling reactions (an amination and an inter-molecular Heck reaction) in one-pot using the same catalyst system with two different aryl halides, including aryl chlorides and hetero aryl halides as the coupling partners.     

Reaction of 1,2-dibromoethane with primary amines: formation of N,N′-disubstituted ethylenediamines RNH-CH2CH2-NHR and homologous polyamines RNH-[CH2CH2NR]n-H

The reaction of primary amines RNH₂ (R: Me, Et, iPr, tBu and Ph) with 1,2-dibromoethane gave N,N′-disubstituted ethylenediamines R-NH-CH₂CH₂-NH-R (1) in yields ranging from 10% (1a; R=Me) to 70% (1d, R=tBu; 1e, R=Ph). Piperazines and N-substituted polyethyleneimines were identified (¹H NMR, ¹³C NMR and EI-MS) as side products of the reaction and isolated by fractional distillation. The piperazines 2 are formed in yields of 3-10% and can be separated from the diamines 1 in all cases, except for R=Me and Ph. The polyamine homologues RNH-[CH₂CH₂NR]_n-H (3-5) were isolated in yields ranging from 0.1% (n=4, R=iPr) to 14% (n=2, R=iPr). The yields of 1 increase with the size of the substituent R, no obvious trend exists for the yields of the side products.     

Synthesis and Characterization of a New Layered Aluminophosphate [Al3P4O16][(CH3)2NHCH2CH2NH(CH3)2][H3O]

A new layered aluminophosphate, denoted AlPO-CJ12, has been synthesized in the system Al(OPrⁱ)₃-H₃PO₄-tetramethylethylenediamine-triethyleneglycol and its structure solved by single-crystal X-ray diffraction analysis. It is further characterized by X-ray powder diffraction, ICP, TG, DTA, and elemental analyses. The compound has an empirical formula of [Al₃P₄O₁₆][(CH₃)₂NHCH₂CH₂NH(CH₃)₂][H₃O], and crystallizes in the triclinic space group P-1 (No. 2) with a=8.9907(6) Å b=9.8359(6) Å, c=14.5566(8) Å, α=75.872(3)°, β=88.616(3)°, γ=63.404(3)°, Z=2, R₁=0.0451, and wR₂=0.1094. The alternation of tetrahedral AlO₄ and PO₃ (=O) units forms a sheet structure with a 4×6×8 network. The inorganic layers stacked in an AAAA sequence are held together by the protonated organic amine and water molecules. The co-templating role of the water molecules is studied by the calculation of the nonbonding host-guest interaction energies through a computational simulation.     

Synthese und reaktivität des diphenylacetyleniridium-komplexes C5H5Ir(C2Ph2)PPr3i und bildung einer isomeren iridainden-verbindung

trans-[IrCl(C₂R₂)(PPr₃ⁱ)₂] complexes are prepared from [(C₈H₁₄)₂IrCl]₂, PPr₃ⁱ and C₂R₂ (R = H, Me, Ph) via the intermediate [IrCl(PPr₃ⁱ)₂]. With phenylacetylene, a mixture of two isomers, trans-[IrCl(PhC₂H)(PPr₃ⁱ)₂] and IrHCl(C₂Ph)(PPr₃ⁱ)₂ is formed which reacts with pyridine to give IrHCl(C₂Ph)(py)(PP₃ⁱ)₂. Reaction of trans-[IrCl(C₂Ph₂)(PPr₃ⁱ)₂] with NaC₅H₅ yields the compound C₅H₅Ir(C₂Ph₂)PPr₃ⁱ (VI) which is transformed via the vinyl complex C₅H₅Ir(CPhCHPh)(OCOCF₃)PPr₃ⁱ (VII) into the iridaindene derivative IX. Using VII as the starting material, C₅H₅Ir(OCOCF₃)₂PPr₃ⁱ, C₅H₅Ir(CPhCHPh)(I)PPr₃ⁱ and C₅H₅Ir(CPhCHPh)(CH₃)PPr₃ⁱ are also obtained. Treatment of VI with Br₂ and I₂ respectively yields the complexes C₅H₅IrX₂PPr₃ⁱ) (XII, X = Br; XIII, X = I), of which XIII reacts with CH₃MgI to give C₅H₅Ir(CH₃)₂PPr₃ⁱ.     

One-step synthesis of pentavalent triphenylantimony derivatives Ph3Sb(OSiR3)2, Ph3Sb(OCH2CH2)2NH and Ph3Sb(OCH2CH2NMe2)2: X-ray molecular structure of Ph3Sb(OSiMe3)2

Pentavalent bis(triorganosiloxy)triphenylantimony derivatives, Ph₃Sb(OSiR₃)₂ (R = Me, Ph), were synthesized by reaction of triphenylantimony with trimethyl- or triphenylsilanol in the presence of tert-butylhydroperoxide by the mild reaction conditions (0-5 °C, 2 h). The reaction of triphenylantimony with diethanolamine in the presence of tert-butylhydroperoxide gave the cyclic compound Ph₃Sb(OCH₂CH₂)₂NH. The mixture of Ph₃SbO and Ph₃Sb(OCH₂CH₂NMe₂)₂ was obtained by the reaction of triphenylantimony with 2-(N,N-dimethylamino)ethanol in the presence of tert-butylhydroperoxide.     

The reaction of the group-13 alkyls ER3 (E = Al, Ga, In; R = CH2t-Bu, CH2 SiMe3) with the platinum-complex [(dcpe)Pt(H)(CH2t-Bu)]

The reactions of the sterically demanding group-13 alkyls ER₃ (E = Al, Ga, In; R = CH₂t-Bu, CH₂SiMe₃) with the platinum-complex [(dcpe)Pt(H)(CH₂t-Bu)] were re-investigated. The bimetallic compounds [(dcpe)Pt(ER₂)(R)] (3: E = Ga, R = CH₂SiMe₃; 5: E = In, R = CH₂t-Bu; dcpe = bis(dicyclohexylphosphino)ethane) with direct σ(Pt-E) bonds were obtained by oxidative addition of an E-C bond to the coordinatively unsaturated fragment [(dcpe)Pt] produced in situ by thermolysis of the starting complex [(dcpe)Pt(CH₂t-Bu)(H)]. The single crystal structure determination reveals a Pt-Ga bond length of 2.376(2) Å and a Pt-In bond length of 2.608(1) Å. All new compounds were characterised by elemental analysis, ³¹P and ¹⁹⁵Pt NMR spectroscopy. Interestingly, the Pt-Ga compound 3 slowly transforms into the platinum alkyl/hydride isomer {(dcpe)Pt(μ₂-H)[CH₂Si(CH₃)₂ CH₂Ga(CH₂SiMe₃)₂]} (4) during crystallization from solution at room temperature. The X-ray single crystal structure analysis revealed both complexes 3 and 4 coexisting in the unit cell in a 1:1 relation. The inaccessibility of analytically pure samples of the Pt-Al complex {(dcpe)Pt[Al(CH₂t-Bu)₂](CH₂t-Bu)} (6), postulated as intermediate of the reaction of [(dcpe)Pt(H)(CH₂t-Bu)] with Al(CH₂t-Bu) on the basis of ³¹P and ¹⁹⁵Pt NMR data, is attributed to an enhanced tendency to isomerisation into the alkyl/hydride Pt/Al congener of 4. A brief DFT analysis of the bonding situation of the model complex [(dhpe)Pt(GaMe₂)(Me)] (1M) revealed, that the contribution of π(Pt-Ga) back-bonding is negligible.     

Unusual rearrangement in the reaction of cyclopropanated cyclopentadienes with Et3Al/CH2I2 in CH2Cl2

The reaction of Et₃Al/CH₂I₂ reagent with cyclopropanated spiro[2.4]hepta-4,6-diene and 6-substituted fulvenes in CH₂Cl₂ was found to lead to the selective formation of rearrangement products through sequential cyclopropyl-allyl rearrangement and cyclopropanation.     

The novel Cs4Nb6F8.5I3.5I6 octahedral niobium cluster fluoro-iodide: a step towards the Nb6F12 cluster core excision

The solid state synthesis of Cs₄Nb₆Fⁱ_8.5Iⁱ_3.5I^a₆ starting from Nb₆F₁₅ binary fluoride, as well as its crystal structure determined by X-ray single crystal diffraction, are presented in this work. This novel cluster compound is based on a Nb₆Iⁱ₃Fⁱ₆Lⁱ₃I^a₆ (L=F, I) discrete unit and crystallizes in the monoclinic system (space group C2/m; Z=4 ; a=10.4363(4) Å, b=18.1227(7) Å, c=19.5102(9) Å β=101.223(1)°, V=3619.5(3) Å³, R₁=0.057; wR₂=0.159). This halide is the first octahedral niobium cluster compound containing unshared terminal I^a ligands together with ordered μ₂-Iⁱ and μ₂-Fⁱ ligands on nine inner positions whilst the three last ones (Lⁱ) are slightly affected by a I/F random occupancy. The structural findings are discussed and compared with those of Nb₆F₁₅, Nb₆I₁₁, CsNb₆I₁₁ and the fluorochlorides and fluorobromides recently reported.     

A novel organically templated three-dimensional open framework vanadium tellurite: (NH3CH2CH2NH3)2V2Te6O18

A novel organically templated vanadium tellurite (NH₃CH₂CH₂NH₃)₂V₂Te₆O₁₈ (1) has been hydrothermally synthesized and characterized by elemental analyses, IR, thermal stability analysis, magnetic susceptibilities and single crystal X-ray diffraction. Compound 1 crystallizes in the monoclinic system, space group P2₁/n, , , , β=94.789(4)°, , Z=2, R₁[I>2σ(I)]=0.0187, wR₂[I>2σ(I)]=0.0482. Compound 1 exhibits a novel three-dimensional (3D) vanadium tellurite anion framework composed of vanadium, tellurium, and oxygen atoms through covalent bonds, with the [NH₃CH₂CH₂NH₃]²⁺ cations residing in the channels.     

Functionalized cyclodiphosphazanes cis-[BuNP(OR)]2 (R=C6H4OMe-o, CH2CH2OMe, CH2CH2SMe, CH2CH2NMe2) as neutral 2e, 4e or 8e donor ligands

Cyclodiphosphazanes having donor functionalities such as cis-[^tBuNP(OR)]₂ (R = C₆H₄OMe-o (2); R = CH₂CH₂OMe (3); R = CH₂CH₂SMe (4); R = CH₂CH₂NMe₂ (5)) were obtained in good yield by reacting cis-[^tBuNPCl]₂ (1) with corresponding nucleophiles. The reactions of 2-5 with [RuCl₂(η⁶-cymene)]₂, [MCl(COD)]₂ (M = Rh, Ir), [PdCl₂(PEt₃)]₂ and [MCl₂(COD)] (M=Pd, Pt) result in the formation of exclusively monocoordinated mononuclear complexes of the type cis-[{^tBuNP(OR)}₂ML_n-κP] irrespective of the reaction stoichiometry and the reaction conditions. In contrast, 2-5 react with [RhCl(CO)₂]₂, [PdCl(η³-C₃H₅)]₂, CuX (X=Cl, Br, I) to give homobinuclear complexes. Interestingly, CuX produces both mono and binuclear complexes depending on the stoichiometry of the reactants and the reaction conditions. The mononuclear complexes on treatment with appropriate metal reagents furnish heterometallic complexes.     

Complexes of neodymium and dysprosium triiodides with amines. Molecular structures of the {Dy[Me2N(CH2)3NH2]8}I3, NdI3(PriNH2)4, and NdI3(PriNH2)5 complexes

The dissolution of DyI₂ in diamine Me₂N(CH₂)₃NH₂ (DMDA) is accompanied by the disproportionation of the salt, hydrogen evolution, and oxidation of Dy^II to Dy^III. The [Dy(DMDA)₈]I₃ complex (1) was isolated from the solution. The neodymium amide amine complex (PrⁱNH)NdI₂(IPA)₄ was produced by the reaction of NdI₂ with isopropylamine (IPA). The recrystallization of this complex from IPA afforded the NdI₃(IPA)₄ complex (2). The recrystallization of (PrⁱNH)NdI₂(IPA)₄ from a toluene-IPA mixture gave the complex with five amine ligands, NdI₃(IPA)₅ (3). The structures of compounds 1, 2, and 3 were established by X-ray diffraction. Dedicated to Academician G. A. Abakumov on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1674–1679, September, 2007.     

Hydrothermal syntheses and structures of two novel vanadium selenites, {[VO(OH)(H2O)](SeO3)}4·2H2O and (H3NCH2CH2NH3)[(VO)(SeO3)2]

Two novel vanadium selenites {[VO(OH)(H₂O)](SeO₃)}₄·2H₂O 1 and (H₃NCH₂CH₂NH₃)[(VO)(SeO₃)₂] 2 were synthesized by hydrothermal method and their crystal structures were determined by single-crystal X-ray diffraction. It is characterized by inductively coupled plasma (ICP), thermogravimetric (TG) and elemental analyses. Compound 1 crystallizes in the monoclinic system, space group C2/c, a=21.2250(11) Å, b=12.6309(6) Å, c=17.0249(10) Å, β=96.830(3)°, V=4531.8(4) Å³ and Z=8, R₁ [I>2σ(I)]=0.0344, wR₂ [I>2σ(I)]=0.119; Compound 2 crystallizes in the monoclinic system, space group P2₁/c, a=9.6389(4) Å, b=6.9922(3) Å, c=15.0324(5) Å, β=102.297(2)°, V=989.90(7) Å³ and Z=4, R₁ [I>2σ(I)]=0.0452, wR₂ [I>2σ(I)]=0.117. {[VO(OH)(H₂O)](SeO₃)}₄·2H₂O has a 1D structure constructed from the {[VO(OH)(H₂O)](SeO₃)}_∞ chains. (H₃NCH₂CH₂NH₃)[(VO)(SeO₃)₂] has a layered structure composed of alternating VO₅ and SeO₃ units with protonated ethylenediamine as interlayer guest.     

Rhodium(I) carbonyl complexes of chalcogen functionalized tripodal phosphines, [CH3C(CH2P(X)Ph2)3] {X = O, S, Se} and their reactivity

The reaction of dimeric rhodium precursor [Rh(CO)₂Cl]₂ with two molar equivalent of 1,1,1-tris(diphenylphosphinomethyl)ethane trichalcogenide ligands, [CH₃C(CH₂P(X)Ph₂)₃](L), where X = O(a), S(b) and Se(c) affords the complexes of the type [Rh(CO)₂Cl(L)] (1a–1c). The complexes 1a–1c have been characterized by elemental analyses, mass spectrometry, IR and NMR (¹H, ³¹P and ¹³C) spectroscopy and the ligands a–c are structurally determined by single crystal X-ray diffraction. 1a–1c undergo oxidative addition (OA) reactions with different electrophiles such as CH₃I, C₂H₅I and C₆H₅CH₂Cl to give Rh(III) complexes of the types [Rh(CO)(COR)ClXL] {R = –CH₃ (2a–2c), –C₂H₅ (3a–3c); X = I and R = –CH₂C₆H₅ (4a–4c); X = Cl}. Kinetic data for the reaction of a–c with CH₃I indicate a first-order reaction. The catalytic activity of 1a–1c for the carbonylation of methanol to acetic acid and its ester is evaluated and a higher turn over number (TON = 1564–1723) is obtained compared to that of the well-known commercial species [Rh(CO)₂I₂]⁻ (TON = 1000) under the reaction conditions: temperature 130 ± 2 °C, pressure 30 ± 2 bar and time 1 h.     

Rotational and vibrational distributions of N2(C 3Πu) excited by state-selected Ar(3P2) and Ar(3P0) metastable atoms

The ESR method is used to study the oxidation kinetics of the CH₃, C₂H₅, n-C₄H₉, i-C₄H₉, s-C₄H₉, t-C₄H₉, n-C₆H₁₃, C₆H₁₁, C₆H₅CH₂, CH₃C₆H₄CH₂, and C₆H₅CH₂CH₂ radicals in methanol matrix at 87 K. The reaction kinetics are shown to be describable in terms of a time-dependent rate constant k(t). The contribution from the matrix relaxation to k(t) has been determined. The oxidation rate and the shape of the kinetic curve are independent of the type of the radical. Models interpreting the experimental data are discussed.     

Dimethylaluminum methide complex Tf2CHAlMe2: an effective catalyst for Diels-Alder reaction of α,β-unsaturated lactone derivatives with cyclopentadiene

Lewis acid derived by mixing Tf₂CH₂ and Me₃Al was found to be an effective catalyst system for the catalytic DA reaction of less reactive α,β-unsaturated lactone derivative with cyclopentadiene (CP). In this catalyst system, Tf₂CHAlMe₂ is an active species and an excess amount of Me₃Al plays an important role to lower the catalyst loading. Substituent effect of the lactone framework on π-facial selectivity was also examined. In the reactions of both γ-substituted 5-membered lactone derivatives and γ- or δ-methylated 6-membered lactone derivatives with CP, selective attack on the anti face of γ- or δ-substituent was observed. On the other hand, in the cases of γ- or ?-methylated 7-membered lactone derivatives, CP favorably attacked on the syn face.