Functionalization of alkanes and cycloalkanes by superelectrophiles. 15. Carbonylation of cycloheptane,cyclooctane, and isomeric monoalkylcyclohexanes with CO in the presence of CBr4·2AlBr3 to form individual esters of tertiary carboxylic acids of the cyclohexane series

Cycloheptane, methylcyclohexane, cyclooctane, and ethylcyclohexane were selectively carbonylated with CO. The reactions of cycloalkanes with CO at –40 °C in the presence of the superelectrophilic system CBr₄·2AlBr₃ in CH₂Br₂ followed by treatment of the reaction mixtures with alcohols afforded esters of 1-methylcyclohexanecarboxylic acid (in the reactions of cycloheptane and methylcyclohexane) or esters of 1-ethylcyclohexanecarboxylic acid (in the reactions of cyclooctane and ethylcyclohexane) in 70—80% yields with respect to CBr₄·2AlBr₃. The reaction of 1,3-dimethylcyclohexane at –40 °C and the reactions of cyclooctane and ethylcyclohexane and at –20 °C proceeded nonselectively to form four isomeric esters C₈H₁₅COOR.     

Electronic structure,geometry, and stability of organic cations,dications, and donor-acceptor complexes

Geometric, electronic, and energy characteristics of the complexes formed in the CF₄ ·nAIF₃ (n = I or 2) and CBr₄ ·nAIBr₃ (n = 1, 2, or 4) systems have been determined by the semiempirical AM I method. Besides the donor-acceptor complexes, the CBr₃ ⁺...AIBr₄ ^–, CBr₃ ⁺...Al₂Br₇ ^–, CBr2²⁺...(AlBr₄ ^–)₂, and CBr₂ ²⁺...(Al₂Br₇ ^–)₂ ionic complexes can be formed in the CBr₄ ·nAlBr₃ systems. In the cations and dications of polyhalomethanes (when Hal = Cl, Br, or l) in both the free and bound (included in ionic complexes) states, carbon atoms carry negative charges, the C-Hal bonds are substantially shortened, and the positive charges are located on one-coordinate halogen atoms. These cations and dications can be considered as halenium ions that differ from halenium salts with dicoordinate halogen atoms. In the cationic and dicationic complexes of the CBr₄ ·nAlBr₃ systems, the maximum positive charges on the Br atoms are 0.39 and 0.94, respectively. Fluorine-containing cations and dications have structures similar to those of carbenium ions, whereas in the CF₄ ·nAIF₃ systems (n = l or 2), only donor-acceptor complexes are formed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya. No. 3, pp. 554–560, March, 1996.     

Oxidative transformations of cyclohexane,methylcyclopentane, and pentane on treatment with superelectrophiles based on polyhalomethane and aluminum halides

Cyclohexane and methylcyclopentane dimerize into dimethyldecalins on treatment with superelectrophilic systems containing polyhalomethanes (CBr₄, CCl₄, CHCl₃) and aluminum halides (AlBr₃, AlCl₃). At 20 °C, the yields of C₁₂H₂₂ hydrocarbons reach 140 mol.% based on the superelectrophile. Under the action of CBr₄·2AlBr₃ at 20 °C in CH₂Br₂ or without a solvent, n-pentane is converted predominantly into lower alkanes (mainly, isopentane). In addition, higher branched C₈--C₁₂ alkanes, small amounts of alkylated cyclohexanes, cycloalkenes, dienes, and alkylbenzenes are formed in a total yield of 20--23 % (w/w) based on pentane.     

Mechanisms of the reactions of propane with CBr3+ cation and superelectrophilic complex CBr4+·AlBr3- containing a bromine-centered cationic center: a theoretical study

Fragments of the potential energy surfaces (PES) of the systems [C₃H₈ + CBr₃ ⁺] and [C₃H₈ + Br₂CBr⁺·Br₂AlBr₂ ^–] were simulated by the MNDO/PM3 method. Energy minima corresponding to weakly bound adducts of propane molecule with the CBr₃ ⁺ cation or neutral complex CBr₃ ⁺·AlBr₄ ^– were found on the PES's of both systems. These are adducts with the coordination of a H atom of the methylene group of the propane molecule to the electrophile at the Br atom carrying the largest positive charge. As the fragments of the adducts are brought close together, the coordinated H atom migrates to the C atom of the CBr₃ ⁺ fragment. The potential barriers of these migrations were found to be low for both systems. The reactions proceed without formation of cyclic intermediates or transition states typical of the Olah mechanism.     

Water-vapor pressure and thermodynamics of the dehydration of manganese,nickel, cadmium,and lead perchlorate hydrates

The water-vapor pressure has been measured by a static method, the temperature limits for existence have been determined, and the parameters of the equation lgp [Torr]=b —a/T have been calculated for the following crystal hydrates: Mn(ClO₄)₂ · 2H₂O (90–130°C, a=3527.0,b=8.487), Ni(ClO₄)₂ · 4H₂O (60–100°C,a=3606.7,b=9.704), Ni(C1O₄)₂ · 2H₂O (110–160°C,a = 4261.7,b = 10.103), Cd(ClO₄)₂ · 6H₂O (25–58.2°C,a = 3143.7,b = 9.356), Cd(ClO₄)₂ · 2H₂O (90–144.8°C,a=3823.3,b = 9.472), Pb(ClO₄)₂ · 3H₂O (10–47°C,a = 2932.9,b = 9.391 and 47–81.5°C,a = 2448.1,b=7.877), Pb(ClO₄)₂ · H₂O (60–102.4°C,a=3610.2,b = 9.857). A hitherto unknown metastable hydrate Cd(ClO₄)₂ · 4H₂O with a phase transition at 30.9°C (20–30.9°C,a = 3669.5,b = 11.343 and 30.9–63.7°C,a=3058.6,b = 9.339) has been detected.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 466–470, March, 1993.     

Functionalization of saturated hydrocarbons by aprotic superacids 5. Regioselective carbonylation of propane in an organic solvent initiated by aprotic organic superacids CX4·nAlBr 3 (X = Br,Cl;n = 1 or 2)

Aprotic organic superacids CX₄ ·nAlBr₃ (X = Br, CI; n = 1 or 2) are effective initiators of carbonylation of propane with CO in an organic solvent at -10 to -20 °C.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1214–1216, May, 1996.     

Neutral molecule/crown ether interactions 5. Comparison of the C−H acidic interactions of nitromethane and acetonitrile with 18-crown-6 and dibenzo-18-crown-6. Crystal structures of dibenzo-18-crown-6·2 CH3NO2 and dibenzo-18-crown-6·2 CH3CN

Complete structural characterization of dibenzo-18-crown-6·2 CH₃NO₂ and dibenzo-18-crown-6·2 CH₃CN have been carried out, including location and refinement of the methyl hydrogen atoms. Dibenzo-18-crown-6·2 CH₃NO₂ is monoclinic,P2₁/c, with (at –150°C)a=9.573(2),b=14.636(2),c=33.471(7) Å, =93.77(2)°, andD _calc=1.37 g cm^–3 forZ=8. Interactions between the solvent methyl groups and the crown ethers and other solvent nitro groups associate the 1 : 2 complexes into polymeric chains alongb. The acetonitrile adduct exists as discreet 1 : 2 complexes in the solid state with C–H...O interactions exlusively to the ether. This complex is triclinic,P 1, with (at –150°C)a=9.458(6),b=9.570(5),c=14.404(5) Å, =73.18(4), =79.85(5), =66.82(6)°, andD _calc=1.28 g cm^–3 forZ=2. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82070 (22 pages).For part 4, see reference [1].     

Cationic polymerization of hydrocarbon monomers induced by complexes of acyl halides with Lewis acids 5. Polymerization of isobutylene in the presence of the complexes of benzoyl chloride with aluminum bromide

Polymerization of isobutylene inn-hexane at -78 °C in the presence of the complex of benzoyl chloride with AIBr₃ (1 : 2) was investigated. The results were compared to those obtained previously for the polymerization of this monomer induced by the complex of acetyl bromide with AlBr₃. Both complexes initiate the polymerization only by acyl cations. The number average molecular weight (M _n ) of the polymer linearly increases as the degree of isobutylene conversion increases. The polymerization restarts after repeated addition of the monomer, andM _n continues to increase linearly. The efficiency of the initiaton by the benzoyl chloride complex does not exceed 6.2 %; the reaction has the second order with respect to the initiator in the case of PhCOCI · A1₂Br₆; and the chain-propagation rate constant is 13.9 L mol^–1 s t. The use of PhCOCI Al₂Br₆ as the initator of the polymerization of isobutylene allows one to prepare macromolecules with very low contents of the terminal C=C double bonds and with narrow molecular weight distributions. Unlike the MeCOBr·AlBr₃ complex, PhCOCl · AlBr₃ does not initiate polymerization of isobutylene.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1175–1179, May, 1996.     

Crystal Structure of 4,7,13,16,21,24-Hexaoxa-1,10-diazoniabicyclo[8.8.8]hexacosane Semihydrate Oxonium Tribromide

The crystal structure of 4,7,13,16,21,24-hexaoxa-1,10-diazoniabicyclo-[8.8.8]hexacosane semihydrate oxonium tribromide, [H₂(2.2.2-Crypt)·0.55H₂O]²⁺·H₃O⁺·3Br⁻ (I) was determined by XRD analysis. The triclinic structure of I (space group P , a = 10.026 Å, b = 11.292 Å, c = 13.115 Å, α = 78.37°, β = 72.11°, γ = 77.50°, Z = 2) was solved by direct methods; full-matrix least-squares refinement in an anisotropic approximation converged to R = 0.055 for all 4057 independent reflections collected (CAD-4 automatic diffractometer, λCuK _α).Original Russian Text Copyright © 2004 by A. N. Chekhlov__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 6, pp. 1136–1141, November–December, 2004.     

Conductance of tris(hydroxymethyl)-aminomethane hydrochloride (Tris·HCl) in water at 25 and 37°C

The conductances of aqueous solutions of tris(hydroxymethyl)aminomethane hydrochloride (Tris·HCl) at 25°C and 37°C have been measured. The concentration of salt varied from 4×10^–4 to 1.6×10^–2 mole-dm^–3. The data were analyzed by the full Pitts equation which yielded the following parameters: at 25°C, ° = 106.07 S-cm²-mole^–1, K_A=1.01; at 37°C, ° = 106.07 S-cm²-mole^–1, K_A=0.99. These values suggest that Tris·HCl is essentially completely dissociated in water. The mobility of the Tris·H⁺ ion was found to be considerably smaller than that of the alkali metal cations. This result is consistent with abnormal liquid-junction potentials for Tris buffer solutions at 25 and 37°C.     

On the detection by EXAFS spectroscopy of multimeric species and of complex anions in diethylether and diethylcarbonate

EXAFS spectroscopy has been shown to be a reliable tool for detecting the formation in solutions of molecular associations (LiBr)_n where n is solvent dependent. The signal Br^*...Br observed at 3.8₇ Å confirms the formation of tetrameric species (n=4) in diethylether (Et₂O) but only of dimers (n=2) in diethylcarbonate. Another signal observed at 2.4₅ Å has·been attributed to the pair Br^*...Li. The study of Li₂MBr₄–Et₂O solutions (M=Co, Cu, Zn) also affords new evidence for the formation of complex anions MBr ₄ ^2– but the spectra obtained at the bromine or metalK-edges for LiZnBr₃–Et₂O solutions seems to indicate the formation of more complex aggregates (LiMBr₃)_q. While the signal of the shell Br^*...Br is found quite intense for the reference CBr₄–Et₂O system, it does not appear for the MBr ₄ ^2– complex except for CuBr ₄ ^2– where the Jahn-Teller effect might rigidify a distorted tetrahedral structure.Presented, in part, at the VIIth International Conference on Non-Aqueous Solutions, Regensburg, West Germany, Ausgust 1980.     

Preparation,spectroscopic and structural analysis of uranium-arabinose complexes

The reaction betweenL-arabinose and hydrated uranyl salts has been investigated in aqueous solution and the solid complexes of the type UO₂(L-arabinose)X ₂ · 2 H₂O, whereX=Cl^–, Br^–, and NO ₃ ^– , have been isolated and characterized. Due to the marked similarities with those of the structurally known Ca(L-arabinose)X ₂ · 4 H₂O and Mg(L-arabinose)X ₂ · 4 H₂O (X=Cl^– or Br^–) compounds, the UO ₂ ²⁺ ion binds obviously to twoL-arabinose moieties, through O1, O5 of the first and O3, O4 of the second molecule resulting into a six-coordinated geometry around the uranium ion with no direct U-X (X=Cl^–, Br^– or NO ₃ ^– ) interaction. The intermolecular hydrogen bonding network of the freeL-arabinose is rearranged upon uranium interaction. The -anomer configuration is predominant in the freeL-arabinose, whereas the -anomer conformation is preferred in the uranium complexes.

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Darstellung, spektroskopische und Strukturanalyse von Uran-Arabinose Komplexen

Zusammenfassung Es wurde die Reaktion zwischenL-Arabinose und hydratisierten Uranylsalzen in wäßriger Lösung untersucht und kristalline Komplexe des Typs UO₂(L-Arabinose)X ₂ · 2 H₂O mitX=Cl^–, Br^– und NO ₃ ^– isoliert und charakterisiert. Wie aus markanten Ähnlichkeiten der Komplexe mit den bekannten Verbindungen Ca(L-Arabinose)X ₂ · 4 H₂O und Mg(L-Arabinose)X ₂ · 4 H₂O (X=Cl^– oder Br^–) abzuleiten ist, bindet das UO ₂ ²⁺ -Ion mit zweiL-Arabinose Einheiten, wobei sich durch die O1,O5-Koordination des ersten und die O3,O4-Koordination des zweiten Moleküls eine sechs-koordinierte Geometrie um das Uranylion [ohne direkte U-X (X=Cl^–, Br^– oder NO ₃ ^– ) Wechselwirkung] ausbildet. Die intermolekularen Wasserstoffbrücken zeigen nach der Wechselwirkung mit dem Uranylion eine Umgruppierung. In der freienL-Arabinose ist das -Anomere vorherrschend, in den Urankomplexen hingegen das -Anomere.

     

Synthesis,characterisation and solid state thermal behaviour of nickel(II) diamine complexes

Summary [NiL₂X₂] (L =N,N-dimethyl-1,2-ethanediamine; X = Cl^–, CF₃CO ₂ ^– , CC1₃CO ₂ ^– and CBr₃CO ₂ ^– ), [NiL₂C₂O₄] · H₂O and [NiL₂X₂] · 2 H₂O (X = Br^–, 0.5 SO ₄ ^2– and 0.5 SeO ₄ ^– ) have been synthesised and their thermal studies carried out. Thermally induced phase transition phenomena are noticed in [NiL₂X₂] (X = CF₃CO ₂ ^– and CCl₃CO ₂ ^– ) and their probable mechanisms are described. [NiL₂X₂] (X = Br^–, 0.5 SO ₄ ^2– and 0.5 SeO ₄ ^2– ) and [NiLX₂] (X = Cl^–, 0.5 C₂O ₄ ^2– and 0.5 SO ₄ ^2– ) have been prepared by solid state pyrolysis from the respective parent diamine complexes. [NiL₂X₂] have been made in solid state by temperature arrest technique from [NiL₂(CX₃CO₂)₂] (X = Cl^– and Br^–).     

The preparation and characterisation of chromium(III) complexes of C-meso-5, 12-dimethyl-1, 4, 8, 11-tetraazacyclotetradecane (LM). Aquation and base hydrolysis kinetics ofcis- andtrans-[CrLMCl2]+

Summary The reaction of [CrCl₃(DMF)₃] with C-meso-5, 12-dimethyl-1, 4, 8, 11-tetra-azacyclotetradecane(L_M) in DMF gives a mixture ofcis-[CrL_MCl₂]Cl (ca. 90%) andtrans-[CrL_MCl₂]Cl (ca. 10%). These complexes are readily separated, as thecis-isomer is insoluble in warm methanol while thetrans-isomer is soluble. Using the dichlorocomplexes as precursors it has been possible to prepare a range ofcis-[CrL_MX₂]⁺ complexes (X=Br^–, NO ₃ ^– , N ₃ ^– , NCS^– and X₂=bidentate oxalate) and alsotrans-[CrL_MX₂]⁺ complexes (X=Br^–, H₂O or NCS^–). The spectroscopic properties and detailed stereochemistry of the complexes are discussed.The aquation and base hydrolysis kinetics ofcis- andtrans-[CrL_MCl₂]⁺ have been studied at 25° C. Base hydrolysis of thecis-complex is extremely rapid with K_OH =1.46×10⁵ dm³ mol^–1 at 25° C. This unusual reactivity appears to be associated with thetrans II stereochemistry of thesec-NH centres of the macrocycle. Base hydrolysis of thetrans complex with thetrans III chiral nitrogen stereochemistry is quite normal with k_OH =1.1 dm³ mol^–1 s^–1 at 25° C.     

Solubility of methane in aqueous solutions of triethylenediamine

The solubilities of methane were measured in water and aqueous solutions of triethylenediamine (TED), triethylenediamine hydrochloride (TED·HCl), and HCl at several concentrations up to 1M at 5° intervals from 5 to 25°C. Methane solubilities in solutions of TED·HCl and HCl are lower than those in water and decrease with increasing cosolute concentration. In contrast, the solubilities in TED solutions are greater than those in water and increase with increasing TED concentration. The order of methane solubilities at 25°C in water and in 0.5M aqueous solutions is TED>H₂O>HCl>TED·HCl with Ostwald coefficients of 3.57×10^–2, 3.44×10^–2, 3.26×10^–2, and 3.19×10^–2, respectively, and with an experimental precision of about ±0.2×10^–3. Thermodynamic functions for the transfer of methane from water to 0.25, 0.50, and 0.75M aqueous solutions have been calculated on the molar concentration scale. The free energies of transfer are compared with previous results for methane in aqueous solutions of tetraalkylammonium halides.     

Reaction of Tetraphenylantimony Bromide with o-Tolylbismuth Bis(2,5-dimethylbenzenesulfonate). The Formation of Tetranuclear Anion [Bi4Br16]4–

The [Ph₄Sb]₄[Bi₄Br₁₆] complex was synthesized via reaction of tetraphenylantimony bromide with o-tolylbismuth bis(2,5-dimethylbenzenesulfonate) and studied using X-ray diffraction analysis. This compound has ionic structure and consists of tetraphenylstibonium cations and a four-charge tetranuclear anion [Bi₄Br₁₆]^4– formed by two pairs of edge-sharing iBr₆ octahedra. The Sb–C bond lengths are equal to 2.05(1)–2.10(1) Å, the Bi–Br distances lie within the 2.649(2)–3.246(2) Å range, and the Sb(1)···Br(7) distance is equal to 3.934(2) Å.     

Cationic polymerization of hydrocarbon monomers under the action of acyl halide complexes with Lewis acids

Polymerization of isobutylene in hexane at –78 °C under the action of the complex AcBr · 2AlBr₃ (Ac-2) affords polyisobutylene having C=O groups at the head and C-Br or C=C groups at the tail of all the molecules. The presence of the latter indicates that there occurs proton elimination from the growing carbocation with the formation of a superacid HBr · 2AlBr₃ which is unable to initiate the polymerization repeatedly under given contitions. This makes it possible to consider proton elimination as the reaction of the decay of active centers with the rate constantk _d. This value has been calculated from the rate of accumulation of the polymeric molecules having terminal C=C bonds:k _d=3.5 · 10^–4 s^–1. The rate constant of chain growthk _g has been determined from polymerization kinetics and from the content of active centers:k _g=6.2 L mol^–1 s^–1.For part 3, see ref. 4.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 883–886, May, 1993.     

Study of complex formation between aluminum bromide and benzene by 27Al NMR spectroscopy

The reaction of aluminum bromide with benzene in n-hexane was studied by ²⁷Al NMR spectroscopy in the temperature range from –80 to +20 °C. The formation of C₆H₆·Al₂Br₆ (1 : 2) complexes is accompanied by broadening of the resonance line with 178. No peak splitting following a decrease in the temperature was observed but the temperature dependence of the line width passed through a maximum near –60 °C. A procedure for determination of the constant K for the formation of 1 : 2 complexes at –20, 0, and +20 °C based on the line broadening with an increase in the C₆H₆ : Al₂Br₆ molar ratio was proposed. The thermodynamic parameters of complex formation, G, H, and S, were calculated.     

Thermally induced isomerisation and decomposition of diethylenetriamine complexes of nickel(II) in the solid state

Summary Complexes [NiL₂]X₂·nH₂O (L=diethylenetriamine; n=O when X=CF₃CO₂ or CCl₃CO₂; n=1 when X=Cl or Br, and n=3 when X=0.5SO₄ or 0.5SeO₄) and NiLX₂·nH₂O (n=1 when X=Cl or Br; n=3 when X=0.5SO₄ or 0.5SeO₄) have been synthesised and investigated thermally in the solid state. NiLSO₄ was synthesised pyrolytically in the solid state from [NiL₂]SO₄·[NiL₂]X₂ (X=Cl or Br) undergo exothermic irreversible phase transitions (242–282° C and 207–228° C; H=–11.3 kJ mol^–1 and –1.9 kJ mol^–1 for [NiL₂]Cl₂ and [NiL₂]Br₂, respectively). [NiL₂]-phenomenon (158–185° C; H=2.0 kJ mol^–1). NiLX₂· nH₂O (n=1 or 3) undergo simultaneous deaquation-isomerisation upon heating. All the complexes possess octahedral geometry.     

Coordination behaviour of 2-guanidinobenzimidazole towards cobalt(II), nickel(II), copper(II) and zinc(II). An experimental and theoretical study

Summary The following coordination compounds derived from 2-guanidinobenzimidazole (2GB) (1); [Ni(2GB)₂]Cl₂· H₂O, (2); [Ni(2GB)₂]Br₂·3H₂O, (3); [Ni(2GB)₂-(NO₃)₂, (4); [Ni(2GB)₂](OAc)₂, (5); [Cu(2GB)Cl₂], (6); [Cu(2GB)Br₂], (7); [Cu(2GB)₂]Br₂·2H₂O, (8); [Cu(2GB)₂](NO₃)₂·H₂O, (9); [Cu(2GB)₂](OAc)₂· H₂O, (10); [Zn(2GB)Cl₂]·H₂O, (11); [Zn(2GB)Br₂]·H₂O, (12); [Co(2GB)Cl₂(H₂O)₂]·5H₂O, (13); [Co-(2GB)₂Cl₂]·3H₂O, (14); [Co(2GB)₂(H₂O)₂](NO₃)₂· 4H₂O, (15); and [Co(2GB)₂(H₂O)₂](OAc)₂, (16) have been synthesized and characterized by i.r. and electronic spectroscopy. In addition (6)–(10) were analysed by e.p.r. The X-ray diffraction structure of compound (4) was obtained. It crystallizes in the monoclinic system, C2/c (a = 22.511(7), b = 6.735(6) and c= 15.345(5)Å, =115.31(3)°, Z = 4, final R = 0.0360 and R _w = 0.0388 for 1167 observed independent reflections). The nickel(II) atom coordinates two ligands in a square-planar geometry through the imidazolic N(3) and the guanidino N(12).The probable ligand isomers involved in the coordination were determined by theoretical calculations, and the possible structures of the coordination compounds were investigated in order to verify that the experimentally proposed structures were stable. Two different types of coordination compounds were found. One, where the ligand is chelating through the imidazolic N(3) and the guanidino N(12), which is the case for most of the complexes [(2)–(13)]. With only one ligand in the coordination sphere, the structure was either tetrahedral (copper and zinc chloride and bromide complexes) or octahedral (cobalt). With two chelating 2GB units a square-planar geometry was stabilized [(2)–(5) and (8)–(10)]. The second type of coordination behaviour was observed in the cobalt compounds [(14)–(16)]. Here the ligand coordinates monodentate through the imidazolic N(3); the structure is tetrahedral.