Synthesis, structure and some reactions of (C5Me4hex)2Ru2(CO)4

The synthesis of the new cyclopentadiene, C₅Me₄(hex)H is described and its reaction with Ru₃(CO)₁₂ to yield (C₅Me₄hex)₂Ru₂(CO)₄ (hex = n-hexyl) is reported. The X-ray crystal structure of the dimer confirms the structure with bridging and terminal CO groups. Reactions of the dimer to yield (C₅Me₄hex)Ru(CO)₂X (X = Cl, Br, I) are reported. IR, NMR and mass spectra are reported for all new compounds. The solubility of the dimer is found to be 10 times greater than that for (C₅Me₅)₂Ru₂(CO)₄.     

C3 epimerization and selective C2C3 bond fission of alkyl chrysanthemate

Treatment of alkyl chrysanthemate with Lewis acid leads to C₃ epimerization, while protonic acid treatment gives rise to selective C₂C₃ bond cleavage. The latter method is successfully applied to the synthesis of optically active tetrahydrolavandulol.     

Synthesis of chiral vicinal C2 symmetric and unsymmetric bis(sulfonamide) ligands based on trans-1,2-cyclohexanediamine by aminolysis of N-tosylaziridines

The ring opening of N-tosylaziridines with aliphatic amines can be efficiently catalyzed by lithium perchlorate to provide derivatives of the trans-1,2-diamine in high yields. The reaction was used in desymmetrization of several cyclic N-tosylaziridines using chiral amines. Using this strategy, an efficient synthesis of chiral vicinal C₂ symmetric bis(sulfonamide) and unsymmetrical bis(sulfonamide) ligands based on trans-1,2-cyclohexanediamine was developed.     

Perfluororganozink-verbindungen: darstellung und eigenschaften von (Rf)2Zn-komplexen (Rf = CF3, C2F5, C3F7, C6F5) [1]

A new method for the preparation of bis(perfluoroorgano) zinc compounds is described: CF₃I and C₆F₅I react with dialkylzinc in the presence of a Lewis base quantitatively to give (CF₃)₂Zn and (C₆F₅)₂Zn complexes, while the analogous reactions with C₂F₅I and iC₃F₇I do not yield the pure compounds. ¹H, ¹⁹F n.m.r, i.r. and Raman spectra are presented.     

Reactivity of [HC{(C(Me)N(Dipp))}2Ca{N(SiMe3)2}(THF)] (Dipp = C6H3Pr2-2,6) with C-H acids: Synthesis of heteroleptic calcium η-organometallics

A series of heteroleptic calcium η⁵-C₅R₅ cyclopentadienides supported by an N-Dipp (Dipp = 2,6-ⁱPr₂C₆H₃)-substituted β-diketiminate ligand have been synthesised by selective protonolysis of the readily available reagent [HC{(C(Me)N(Dipp))}₂Ca{N(SiMe₃)₂}(THF)] with tetramethylcyclopentadiene, fluorene, indene or cyclopentadiene. No reaction was observed with pentamethylcyclopentadiene, presumably for steric reasons. The tetramethylcyclopentadienyl, fluorenyl and indenyl compounds were characterised by variable temperature ¹H NMR and X-ray crystallography. Each complex was found to exist as a mononuclear species both in solution and in the solid state and to be highly sterically crowded, as evidenced by the variable temperature NMR studies. DFT (B3LYP/LANL2DZ) calculations on the model complexes [CaH(C₅Me₄H)], [CaH(C₁₃H₉)] and [CaH(C₉H₇)] indicate that the precise structures of such heteroleptic compounds are a result of both stereoelectronic and steric influences. Attempts to isolate the unsubstituted cyclopentadienyl were unsuccessful, but resulted in the crystallographic analysis of the dimeric calcium siloxide [HC{(C(Me)N(Dipp))}₂Ca(μ-OSiMe₃)]₂.     

The hydrogenolysis of C60 and C70

Temperature-programmed reaction (TPR) of C₆₀ and C₇₀ with H₂ was carried out on nickel in order to investigate the thermal stability of the fullerenes in the catalytic hydrogenation. The TPR profiles showed two methanation peaks and the corresponding weight decrease above 420°C, indicating the hydrogenolysis to CH₄. This revised version was published online in June 2006 with corrections to the Cover Date.     

Ab Initio calculation of molecular, thermodynamic, and kinetic parameters of CF, CF2, CF3, and C2F5 radicals and CF4, CF3I, C2F4, and C2F6 molecules in gas

Enthalpies of formation of ground states of the gaseous particles CF, CF₂, C₂F₅, CF₄, CF₃I, C₂F₄, and C₂F₆ were calculated by ab initio method in the CCSD(T) approximation with extrapolation to the full basis and regard to the correlation energy. Their equilibrium geometrics, frequencies of normal vibrations, and other values were found by the B3LYP/aug-cc-pvdz method, from which thermodynamic functions within the range of 0–6000 K were calculated. Equilibrium constants were calculated from these functions, and then the information on the rate constants in the limit of high pressures was obtained.     

Electrochemical conversions of pentaphenyl(methoxycarbonyl)cyclopentadiene derivatives

Redox processes of fluctuating pentaphenyl(methoxycarbonyl)cyclopentadiene derivatives on platinum electrode in acetonitrile are studied by cyclic voltammetry. The reduction of derivatives of pentaphenylcyclopentadiene C₅Ph₅M yields a radical anion which decomposes to anion M^- and stable radical C₅Ph ₅ ^• ; the latter reduces to C₅Ph₅. In the first stage of oxidation of these compounds, a stable radical cation forms, with substituent M intact. Reduction of derivatives of pentamethoxycarbonylcyclopentadiene [C₅(CO_2Me)₅]M yields a dianion. Such electrochemical behavior of fluctuating cyclopentadiene compounds reveals additional information on the mechanism of displacement of the element-centered substituents M in them     

Multiconfiguration self-consistent wavefunctions for CH4, C2H4 and C2H6

The results of several MC SCF calculations on CH₄, C₂H₄ and C₂H₆ with minimun bases of Slater type AO's are reported. The computing method is a quadratically convergent process. Better final energies are obtained if localized MO's are used.     

The reactions of 2-benzoylpyridine with [RuHCl(CO)(PPh3)3] and [(C6H6)RuCl2]2

The reactions of [RuHCl(CO)(PPh₃)₃] and [(C₆H₆)RuCl₂]₂ with 2-benzoylpyridine have been examined, and two novel ruthenium(II) complexes – [RuCl(CO)(PPh₃)₂(C₅H₄NCOO)] and [RuCl₂(C₁₂H₉NO)₂] – have been obtained. The compounds have been studied by IR and UV–Vis spectroscopy, and X-ray crystallography. The molecular orbital diagrams of the complexes have been calculated with the density functional theory (DFT) method. The spin-allowed singlet–singlet electronic transitions of the compounds have been calculated with the time-dependent DFT method, and the UV–Vis spectra of the compounds have been discussed on this basis.     

Analysis of C60 and C70 fullerenes using high-performance liquid chromatography–Fourier transform infrared spectroscopy

The performance of Fourier transform infrared spectroscopy (FT-IR) detection coupled to high-performance liquid chromatography for the analysis of C₆₀ and C₇₀ fullerenes was investigated. The isocratic separation method involved an octadecylsilane (ODS) column and an acetonitrile–toluene (1:1) mobile phase. The hyphenated system was designed with a split valve to control eluent volume leading to the FT-IR detector; this allowed for additional coupling of the liquid chromatograph to ultraviolet–visible detection. On-line FT-IR spectra of C₆₀ and C₇₀ were matched with standard off-line FT-IR spectra from the literature. In addition, with band chromatograms individual fullerenes can be identified using FT-IR active modes known specifically for each fullerene. Few changes to a pre-existing HPLC–UV method were necessary for the HPLC–FT-IR method, and there was no need for fraction collection to identify the fullerenes C₆₀ and C₇₀.     

The support and characterization of C60 and MoO3 on Al2O3

A new type of catalyst from supporting C₆₀ on MoO₃ and Al₂O₃ has been prepared. The effect of different order of impregnation and calcination atmosphere on catalyst are investigated by the solution test in toluene, UV-VIS spectroscopy and temperature programmed reduction (TPR). The results show that when the catalyst was prepared by supporting MoO₃ on C₆₀/Al₂O₃ and calcined in N₂, there is a stronger interaction between C₆₀, MoO₃ and Al₂O₃, but when supporting C₆₀ on MoO₃/Al₂O₃, the interaction is relatively weak. We consider that in the former method a new complex, Mo–C₆₀–O–Al, is formed.     

Synthesis of cis,cis,cis-1-alkylidene-2,3,4,5-tetrakis(diphenylphosphinomethyl)cyclopentanes

A new strategy to prepare tetradentate or pentadentate diphenylphosphine ligands has been explored from Diels-Alder adducts of fulvenes and maleic anhydride. A tetradentate phosphine ligand, bearing a side chain allowing the formation of a bond with polystyrene resin, has been prepared in seven steps from cyclopentadiene. The cis,cis,cis-1-cyclohexylidene-2,3,4,5-tetrakis(diphenylphosphinomethyl)cyclopentane (Cyclo-Tedicyp) in combination with [PdCl(C₃H₅)]₂ led to an efficient catalyst for the Heck, Suzuki and Sonogashira coupling reactions.     

C-Galactosylceramide diastereomers via Sharpless asymmetric epoxidation chemistry

C-Glycoside analogs of α-galactosylceramide (KRN7000) were synthesized in 19 linear steps with Sharpless asymmetric epoxidation as a key reaction. Opening of a hydroxy epoxide with sodium azide provided an anti vicinal azido diol with inversion of configuration at the azide-bearing carbon while opening with Ti(O-i-Pr)₂(N₃)₂ gave syn vicinal azido diol with retention. The latter, unusual outcome could be rationalized either by invoking Ti-catalyzed intramolecular double S_N2 inversion or by epoxide opening/intramolecular delivery of azide from the Ti complex.     

Synthesis and molecular structures of heptafluoroisopropylated fullerenes: C60(i-C3F7)8, C60(i-C3F7)6, and C60(CF3)2(i-C3F7)2

One isomer of C₆₀(i-C₃F₇)₈, three isomers of C₆₀(i-C₃F₇)₆, and the first mixed perfluoroalkylated fullerene, C₆₀(CF₃)₂(i-C₃F₇)₂, have been isolated by HPLC from a mixture prepared by reaction of C₆₀ with heptafluoroisopropyl iodide in a glass ampoule at 260-290 °C. The molecular structures of the four new compounds have been determined by means of X-ray single crystal diffraction partially also by use of synchrotron radiation. Theoretical calculations at the DFT level of theory have been employed to rationalize the energetics of isomers and of C₆₀-R_f binding.     

A direct stereospecific synthesis of 9,11-etheno- and 9,11-ethano-PGH1 derivatives

The reaction of methyl 10-oxodec-S-ynoate with cyclopentadiene is reported as the key step in the synthesis of 9,11-etheno- and 9,11-ethano-PGH₁ derivatives.     

Synthesis, crystal structure and thermoelectric properties of a new carbide Zr2[Al3.56Si0.44]C5

A new quaternary layered carbide, Zr₂[Al_3.56Si_0.44]C₅, has been synthesized and characterized by X-ray powder diffraction, transmission electron microscopy and thermopower and electrical conductivity measurements. The crystal structure was successfully determined using direct methods, and further refined by the Rietveld method. The crystal is trigonal (space group R3m, Z=3) with lattice dimensions of a=0.331059(5), c=4.09450(5) nm and V=0.38864(1) nm³. The final reliability indices calculated from the Rietveld refinement were R_wp=6.24%, R_p=4.21% and R_B=0.82%. The crystal structure is composed of electroconductive NaCl-type ZrC slabs separated by Al₄C₃-type [Al_3.56Si_0.44]C₃ layers. This material had thermoelectric properties superior to those of the ternary layered carbides Zr₂Al₃C₄ and Zr₃Al₃C₅, with the power factor reaching 7.6×10⁻⁵W m⁻¹ K⁻².     

Reactions of C2(a 3πu) with CH4, C2H2, C2H4, C2H6, and O2 using multiphoton UV excimer laser photolysis

C₂(a ³π_u) disappearance rate constants of 1.44, 0.96, 0.0296, 0.0130 and < 10^?6(x10^?10cm³s^?1) are reported for reactions with C₂H₄, C₂H₂, O₂, C₂H₆, and CH₄, respectively at 298 K. C₂(a ³π_u) fragments are generated by multiphoton ArF excimer laser photodissociation at C₂H₂, and monitored by dye laser induced fluorescence. Arguments are presented which favor chemical reactions over the C₂(a ³π_u) → (X ¹σ⁺_g) quenching channel. C₂ + C₂H₂ represents the one possible exception to the reactive channel.     

Electrorheological properties and structure of (BaTiO(C2O4)2/NH2CONH2)

The core-shell structural (BaTiO(C₂O₄)₂/NH₂CONH₂) samples of giant electrorheological (ER) activity have been synthesized by a sol-gel method and studied by TEM, X-ray diffraction and IR spectroscopy. From the analysis of the X-ray diffraction, it is found that the component of samples is (BaTiO(C₂O₄)₂/NH₂CONH₂) with a different content of urea. The observations of the TEM morphology show that (BaTiO(C₂O₄)₂/NH₂CONH₂) particles are spheral with a size of around 80 nm and a surface coating with 5-10 nm thickness consisting of urea. The samples show an increasing tend of ER effect as the addition of urea increasing. Moreover, by IR spectroscopy study, it is revealed that some peaks of CO band and C-O band vibrations of BaTiO(C₂O₄)₂ are split into two peaks after urea added. The extent of the splits increase with the increase of urea content, which is resulted by the interaction between the chemical bonds of urea and oxalate of BaTiO(C₂O₄)₂. It is evident that the giant ER activity of the sample has a close relationship with the interfacial polarization between the core and the shell of (BaTiO(C₂O₄)₂/NH₂CONH₂).