Carbonyltungsten(0) complexes of acryloylferrocene: Synthesis and characterization

Photolysis of hexacarbonyltungsten(0) in the presence of acryloylferrocene in n-hexane solution at 10 °C yields pentacarbonyl(η²-acryloylferrocene)tungsten(0) (1) as the only photo-substitution product, different from the general reaction pattern observed for the Group 6 metal carbonyls with other olefins. W(CO)₅(η²-acryloylferrocene) (1) decomposes in solution to the parent hexacarbonyltungsten(0) and free acryloylferrocene. Trimethylphosphite was introduced as ligand into the molecule to increase the stability. The photolysis of pentacarbonyl(trimethylphosphite)tungsten(0) in the presence of acryloylferrocene in n-hexane solution at 10 °C yields only cis-W(CO)₄[P(OCH₃)₃](η²-acryloylferrocene) (2) as the monosubstitution product. Both η²-acryloylferrocene complexes (1 and 2) could be isolated and characterized by MS, IR and NMR spectroscopy. The trimethylphosphite complex (2) is found to be even less stable than W(CO)₅(η²-acryloylferrocene) (1).     

Syntheses and structures of lithiated sulfones Li[CR(R′)SO2Ph] - C versus O bound lithium. [{Li{CH(Me)SO2Ph}(thf)}∞] - The structure of a C-bound derivative

Sulfones RCH(R′)SO₂Ph were reacted with n-BuLi in thf/n-hexane (R/R′ = H/Me, Me/Et, H/CH₂Ph) and toluene/n-hexane (R/R′ = Me/Ph) yielding under deprotonation Li[CR(R′)SO₂Ph] which reacted with Me₃SiCl and n-Bu₃SnCl forming the requisite trimethylsilyl and tri(n-butyl)tin substituted derivatives . Performing the reactions of RCH(R′)SO₂Ph with n-BuLi in n-hexane (instead of thf/n-hexane) and toluene/n-hexane, respectively, resulted in the precipitation of the organo lithium compounds Li[CR(R′)SO₂Ph] (1-4) which were isolated as strongly moisture-sensitive yellow powders in essentially quantitative yields. Their identities were confirmed by ¹H and ¹³C NMR spectroscopic measurements in thf-d₈. Solutions of each 1, 3, and 4 in thf/n-hexane and thf/n-pentane afforded crystals of each [{Li{CH(Me)SO₂Ph}(thf)}_∞] (1a), [{Li{CH(CH₂Ph)SO₂Ph}(thf)}_∞] (3a), and [{Li{CMe(Ph)SO₂Ph}(thf)₂}₂] (4a), respectively, whose structures were determined by single-crystal X-ray crystallography. The compounds 1a and 3a crystallize in 1D polymeric ladder-like structures. The strands of 1a are built-up by eight-membered Li₂C₂S₂O₂ rings having direct Li-C bonding interactions (Li-C 2.215(5) Å). The donor set of Li is completed by three oxygen atoms, one from the thf ligand and two from SO₂ groups of neighboring Li{CH(Me)SO₂Ph}(thf) entities. The strands of 3a are built-up of alternating Li₂S₂O₄ eight- and Li₂O₂ four-membered rings. Each lithium atom is coordinated to three oxygen atoms, two from O₂S(Ph)CHCH₂Ph groups and one from thf oxygen atom. There is no Li-C bonding. Compound 4a crystallizes in dimers consisting of eight-membered Li₂S₂O₄ rings in which the two lithium atoms are bridged by two O₂S(Ph)CHMePh groups. The coordination sphere of lithium is completed by two oxygen atoms of the thf ligands.     

The W2Cl4(NHCMe3)2(PR 3)2 molecules (R 3=Me3, Et3, Pr n 3, Me2Ph) I. Their isomeric forms,interconversion proeesses,crystalline forms,and detailed molecular structures

A thorough study of compounds with the formula W₂Cl₄(NHCMe₃)2(PR₃)₂, withR ₃=Me₃, Et₃, Prg ⁿ ₃ Me₂,Ph, is reported. In addition to the previously reported crystalline compounds, namely Ia,trans-W₂Cl₄(NHCMe₃)₂(PMe₃)₂ in space group Pmmn;3a,trans-W₂Cl₄(NHCM₃)₂(PEt₃)₂ in space group P2₁/^a (or P2₁/^c); and4,cis-W₂Cl₄(NHCMe₃)₂(PMe₂Ph)₂ in Pna2₁, we have obtained and structurally characterized the following new substances,1b,trans-W₂Cl₄,(NHCMe₃)₂(PMe₂)₂, space group P2₁/^c,a= 12.233 (4) Å,b= 12.872 (4) Å,c=17.095 (5) Å,=93.52 (2)°,Z=4,V=2687 (1) ų 2,cis-W₂Cl₄(NHCMe₃)₂(PMe₃)₂, P2₁/^c,a=9.673 (4) Å,b=17.249 (4) Å,c=16.244 (5) Å,=99.63 (3),Z = 4 ,V=2669 (1) Å.3b,trans-W₂Cl₄(NHCMe₃)₂(PEt₃)₂, Pl,a=16.850 (3) Å,b=17.797 (3) Å,c= 11.459 (2)Å,= 101.02 (1),= 103.13°, y=84.23 (1)°,Z=4,V= 3279 (1) Å5,trans-W₂Cl₄(NHCM₃)₂(PMe₂Ph)₂, Fdd2,a=39.563 (8) Å at 20°C; 39.325 (10) Å at -6O°C,b = 57.543 (17) Å at 20°C; 57.186 (16) Å at -60°C,c= 8.810 (1) Å at 20°C; 8.770 (1) Å at - 60°C ,Z=24,V=20057 (7) ų (20°C), 19723 (8) ų ( - 60°C) .6,trans-W₂Cl₄(NHCMe_{3 2}(PPrⁿ ₃)₂, Pl,a= 17.287 (2) Å (20°C); 17.077 (5) Å (-60°C),b= 19.119 (2) Å (20°C); 18.952 (6) Å (-60°C),c= 12.713 (1) Å (20°C); 12.668 (4) Å (-60°C),Z=4,V= 3980 (1) ų (20°C), 3898 (2) ,ų ( - 60°C). In addition, the structure of3a was re-determined and refined so that the disorder ratio was a refined parameter, leading to a value of 0.520:0.480 instead of being arbitrarily fixed at 0.50:0.50. In all of the structures the molecules are held in eclipsed (but very distorted) rotational conformations and the W-W distances are all within the range of 2.305-2.330 Å. As will be shown in a later paper, for all phosphines, thecis andtrans isomers are of similar stability and an equilibrium mixture exists in solution. It is also shown that1a and3a do not contain unexpectedly short W-N bonds as previously reported.     

Electronic and magnetic structure of the polymeric system di-imidazolato iron(II)

The polymeric system di-imidazolato iron(II) is synthesized from the reaction of either ferrocene or cyclopentadienyl-irondicarbonyl with imidazole. From Mössbauer measurements in the temperature range 4.2 KT448 K we find two different iron sites in the compound, denoted byA andB, respectively with ratio [A]/[B] = 1.79±0.03. From the isomer shift values we conclude that both Fe ^A and Fe ^B are in the ferrous high-spin state. Below 13.95±0.10 K both subspectra are considerably broadened due to magnetic ordering. From the analysis of the magnetic spectra we derive for the main componentV _zz of the electric field gradient tensorV _zz ^A >0 andV _zz ^B <0. Additionally, we investigate the thermal decomposition of the compound by thermogravimetry in the temperature range 20 °CT 750 °C and by Mössbauer spectroscopy in the temperature range 20 °CT505 °C. The decomposition takes place in four steps. The first step between 20 °C and 190 °C is due to the loss of imidazole nonbonded to iron(II). Comparing the amount of iron with that of pure imidazolato iron(II) we find the formula FeIz₂+0.70 (±0.02) IzH, with Iz standing for doubly deprotonated and IzH for deprotonated imidazole. Step 2 (193 °C<T<235 °C) and step 3 (400 °C<T<500 °C) are found from both methods. Step 4 is above 500 °C. Heat treatment and vacuum conditions affect the thermal decomposition products.Isomer shifts ^A and ^B , and temperature dependent quadrupole splittings E _Q ^A and E _Q ^B are explained using a simple ligand field picture for orbital splittings and occupancies of quasi-tetrahedrally (A) and quasi-octahedrally (B) coordinated ferrous high-spin compounds. Using finally the experimental ratio [A]/[B] = 1.79 we derive for the over-all chemical formula (1.79 Fe ^A Iz_4/2+Fe ^B Iz_4/2+2 IzH) _n = (FeIz₂+0.71 Iz) _–n in agreement with the result which we derived from investigating the thermal decomposition of our compound.Supported by Deutsche Forschungsgemeinschaft     

Cerium(III) Pivalate [Ce(Piv)3(HPiv)3]2: Synthesis, Crystal Structure, and Thermal Stability

The [Ce(Piv)₃(HPiv)₃]₂ complex was synthesized by reacting cerium(III) nitrate with NH₄(Piv) (1 : 4) (HPiv is pivalic acid) in an aqueous solution and by further recrystallization of the obtained precipitate from a 5% HPiv solution in n-hexane. The complex structure and unit cell parameters were determined by X-ray diffraction analysis: a = 16.586(8) Å, b = 12.313(5) Å, c = 20.765(10) Å, = 109.27(2)°, V = 4003(2) ų, Z = 4, R = 0.0546, R _w = 0.0836, space group P2₁/n. The crystal structure of [Ce(Piv)₃(HPiv)₃]₂ consists of centrosymmetric dimeric molecules with the Ce(III) atoms bound by four bridging pivalate ligands. Heating in an atmosphere of nitrogen is accompanied by the elimination of six HPiv molecules in the range of 90–190°C; the thermolysis of the obtained Ce(Piv)₃ occurs at 290–450°C. In addition to the thermal decomposition, the sublimation of Ce(Piv)₃ was also observed under reduced pressure (0.01 mmHg) in the temperature interval of 290–350°C.     

Ring opening of methylcyclopentane over Al2O3 and SiO2 supported Rh catalysts

Hydrogenolytic ring opening of methylcyclopentane (MCP) was investigated on Rh/Al₂O₃ and Rh/SiO₂ catalysts, prepared by the incipient wetness method. Strong dependence can be seen in the yield and distribution of ring opening products as a function of temperature and hydrogen pressure. They depended also on the support used. The ring opening reaction required high hydrogen coverage, and was not random (hindered in the vicinity of the methyl group), thus, mainly 2-methylpentane (2MP) and 3-methylpentane (3MP) were formed. The fragments consisted of C₁–C₅ alkanes, with methane andi-pentane as main fragments. This means the possibility of breaking two C−C bonds during one sojourn of the reactant on the catalyst, both taking place far from the substituent. The loose positive correlation between the ratios ofi-pentane/n-pentane and 3MP/n-hexane seems to support this conclusion. Dedicated to Professor Pál Tétényi on the occasion of his 70th birthday     

Copper(II)–Ammonia Complexation Equilibria in Aqueous Solutions at Temperatures from 30 to 250°C by Visible Spectroscopy

The spectra of copper(II)–ammonia solutions in 2 mol-kg^–1 NH₄NO₃(aq) were recorded as a function of pH with a new UV–visible flow cell, capable of operating at conditions up to 325°C and 300 bars. Equilibrium constants for the formation of copper(II)–ammonia complexes Cu(NH₃)_n ²⁺, 1 n 4, from 30 to 150°C were determined by evolving factor analysis and nonlinear least-squares regression. Measurements at higher temperatures were limited by thermal decomposition of NH₄NO₃(aq). The formation constants of Cu(NH₃)_n ²⁺ decrease with temperature, consistent with extrapolations of literature data from measurements below 100°C. Measurements above 150°C were carried out in 0.5 mol-kg^–1 CF₃SO₃H (aq), at the very high ammonia concentrations required to avoid the precipitation of CuO(s). The spectra are consistent with Cu(NH₃)₄ ²⁺ as the predominant species, based on extrapolations of peak maxima and molar absorptivities from lower temperatures. Shifts in the spectra of Cu²⁺ and the Cu(NH₃)_n ²⁺ species to higher wavelength and increases in molar absorbance with increasing temperature are discussed in terms of the structure of the complexes.     

Synthesis of di-Iron-Containing Inorganic Synzyme, γ-SiW10{Fe(OH2)}2O386?, and the Liquid-Phase Oxidation Catalysis

The Keggin-type di-iron-substituted silicotungstate, -SiW₁₀{Fe(OH₂)}₂O₃₈ ^6– (I), was synthesized by the reaction of the lacunary [-SiW₁₀O₃₆]^8– with Fe(NO₃)₃ in an acidic aqueous solution and isolated as the tetra-n-butylammonium salt (TBA-I). It was characterized by various analyses and the structure with the oxo-bridged di-iron site was clarified. TBA-I was stable and catalyzed selective oxidation of various alkanes and alkenes with hydrogen peroxide: cyclohexane, adamantane, n-hexane, and n-pentane were catalytically oxidized. Even lower alkanes such as methane, ethane, propane, and n-butane were catalytically oxidized. It was remarkable that the efficiency of hydrogen peroxide utilization to oxygenated products reached up to ca. 100% for the oxidation of cyclohexane and adamantane. Alkenes were mainly epoxidized with hydrogen peroxide. It was demonstrated that the TBA-I showed high turnover number of 135–147 for the oxidation of cyclohexane with 1 atm oxygen.     

Polymethylenebis(octylarsinic acids), [C8H17As(O)OH]2 (CH2)n,as reagents for the liquid-liquid extraction of cerium(III) and Europium(III)

Summary Cerium(III) and europium(III) are extracted at 50° C by [C₈H₁₇ As(O)OH]₂(CH₂) _n (n=6, 8, 12) inn-octanol from aqueous solutions containing NaCl and acetic acid/sodium acetate in the pH range 6.7–8.0. The extraction coefficient, , reached a maximum of: 10.0, 13.2 forn=6; 10.7, 20.0 forn=8; 4.68, 6.03 forn=12; at an aqueous equilibrium pH of: 7.65, 7.80 forn=6; 7.89, 7.95 forn=8; 7.81, 7.82 forn=12; corresponding to the extraction efficiency of: 91%, 93% forn=6; 92%, 95% forn=8; 80%, 83% forn=12; for cerium and europium, respectively.The log was found to be second power dependent for cerium and one and one-half power dependent for europium on the negative log of the aqueous equilibrium [H⁺] forn=6, 8, 12. The extractions were done at 50°C using organic reagent solutions (1.09×10^–3 M forn=12, 1.08 × 10^–3 M forn=8, 1.32×10^–3 M forn=6) and aqueous solutions of 1.0×10^–5 M for CeCl₃ and EuCl₃, having their Cl^– ionic strengths adjusted to 0.100 molar with NaCl. It was found that the slopes increase in the pH dependence studies in the seriesn=6, 8, and 12 for both cerium and europium metal ions. The reagent dependence studies were done at 50°C and pH: 7.00, 6.80 forn=6; 7.30, 7.20 forn=8; 7.45, 7.35 forn=12; for cerium and europium, respectively. The log was found to be first power dependent on the log of the uncomplexed reagent concentration at equilibrium. It is assumed that the complexes are hexacoordinated.

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Polymethylenebis-Oktylarsinsäuren als Reagenzien für die Flüssig-flüssig-Extraktion von Cer(III) und Europium(III)

Zusammenfassung Cer(III) und Europium(III) werden aus wäßrigen, Kochsalz und Essigsäure/Acetat enthaltenden Lösungen bei 50°C mit C₈H₁₇As(O)OH₂(CH₂)_n (_n=6, 8, 12) im pH-Gebiet 6,7–8,0 extrahiert. Der Extraktionskoeffizient erreicht ein Maximum von: 10,0, 13,2 für_n=6; 10,7, 20,0 fürn=8; 4,68, 6,03 fürn=12; bei einem wäßrigen Gleichgewicht-pH von: 7,65, 7,80 fürn=6; 7,89, 7,95 fürn=8; 7,81, 7,82 fürn=12, entsprechend dem Aus maß der Extraktion von: 91%, 93% fürn=6; 92%, 95% fürn=8; 80%, 83% fürn=12; für Ce bzw. Eu.Für Cer ist der log in zweiter Potenz, für Europium in erster und 1/2 Potenz abhängig vom negativen log des wäßrigen [H⁺]-Gleichgewichtes fürn=6, 8, 12. Die Extraktionen wurden bei 50°C mit organischen Reagens-lösungen (1,09×10^–3 M fürn=12, 1,08×10^–3 M fürn=8, 1,32×10^–3 M fürn=6) und mit wäßrigen Lösungen von 1,0×10^–5 M für CeCl₃ und EuCl₃ durchgeführt, deren lonenstärke für Cl^– mit NaCl auf 0,100M eingestellt wurde. Bei der Untersuchung der pH-Abhängigkeit bei den Reihenn=6, 8 und 12 ergab sich ein Anstieg sowohl für Ce wie für Eu. Die Reagens-Abhängigkeit wurde bei 50°C und bei pH 7,00, 6,80 fürn=6; 7,30, 7,20 fürn=8; 7,45, 7,35 fürn=12 für Cer bzw. Europium geprüft. Der log war einfach abhängig vom log der Konzentration des unkomplexierten Reagens beim Gleichgewicht. Es wird angenommen, daß die Komplexe hexakoordiniert sind.

     

Synthesis, characterization, and ethylene polymerization behavior of [(RR′-admpzp)2Ti(OPr)2] complexes (RR′-admpzp = 1-dialkylamino-3-(3,5-dimethyl-pyrazol-1-yl)-propan-2-olate)

[(RR′-admpzp)₂Ti(OPrⁱ)₂] complexes (2a-c), synthesized from reaction of Ti(OPrⁱ)₃Cl (0.5 equiv) with 1-dialkylamino-3-(3,5-dimethyl-pyrazol-1-yl)-propan-2-ol compounds in the presence of triethylamine (0.5 equiv), are pseudo-octahedral with each RR′-admpzp ligand κ²-O,N(pyrazolyl) coordinated to the titanium center. In solution, 2a-c adopt isomeric structures that are in dynamic equilibrium. At 23 °C, 2a-c/1000 MAO catalyst systems furnished high molecular weight polymers with narrow molecular weight distributions (M_w/M_n = 2.7-2.8). At 100 °C, 2a-c/MAO catalyst systems exhibited increased polymerization activity and 2c/1000 MAO system furnished high molecular weight polyethylene with a molecular weight distribution (M_w/M_n = 2.1) that is close to that found for single-site catalysts.     

Prediction of Stability Constants for Cr(III) and Cr(II) Complexes

Regression analysis was used to derive equations for estimaing thermodynamic stability constants for complexes of Cr²⁺ (log^° ₁[Cr²⁺L] = 0.53log^° _n [H _n L]) and Cr³⁺ (log^° ₁[Cr³⁺L] = 0.88log^° _n [H _n L]) from the known protonation constants of H _n L ligands and for determining stability constants of Cr²⁺ and Cr³⁺ complexes from the available stability constants of Cu²⁺ complexes (log^° ₁[Cr²⁺L] = 0.76log^° ₁[Cu²⁺L] and log^° ₁[Cr²⁺L] = 0.60log^° ₁[Cr³⁺L], respectively). Parameters of the Panteleon–Ecka equation for calculating stability constants of Cr²⁺ complexes ( = 0.57) and Cr³⁺ complexes ( = 0.69) with two and three bidentate ligands were also determined. The ratio of logarithmic stability constants for complexes with the same metals but with different metal ionic charges was found to be approximately equal to the ratio of charges on the central ions. The stability constant of Cr(II) sulfate complex was calculated.     

Silicon Carbide Modified Carbon Materials. Formation of Nanocrystalline SiC from Thermochemical Processes in the System Coal Tar Pitch/Poly(carbosilane)

Poly(carbosilane) or PCS, {–CH₂–SiH(CH₃)–} _n , is used as a Si-bearing precursor in combination with a coal tar pitch to study thermally induced transformations toward SiC-modified carbon composites. Following mixing of the components in the molten pitch at 160°C, the mixture is heated under argon atmosphere at 500°C yielding a solid carbonizate that is further subjected to separate pyrolysis experiments at 1300°C or 1650°C. At temperatures up to 500°C, the PCS reacts with suitable pitch components as well as undergoing decomposition reactions. At higher temperatures, clusters of prevailingly nanocrystalline -SiC are confirmed after the 1650°C pyrolysis step with indications that the formation of the compound starts at 1300°C. ²⁹Si MAS NMR, XRD, FT-IR, XPS, and elemental analysis are used to characterize each pyrolysis step, especially, from the viewpoint of transformation of silicon species to silicon carbide in the carbon matrix evolved from the pitch.     

Nonoxidative conversion of methane and <Emphasis Type="Italic">n</Emphasis>-pentane over a platinum/alumina catalyst

Methane adsorption on the Pt–H/Al₂O₃ and Pt/Al₂O₃ catalysts begins at Т = 475°C and is accompanied by the appearance of hydrogen in the reaction medium. At a higher temperature is raised to 550°C, the amount of adsorbed hydrogen increases to 1.1 and 0.8 mol/(mol Pt), respectively. According to the calculated degree of methane dehydrogenation on platinum sites at Т = 550°C, the Н/C ratio is 1.3 (at/at) for the Pt–H/Al₂O₃ catalyst and 1.5 (at/at) for the Pt/Al₂O₃ catalyst. The introduction of n-pentane into the reaction medium increases the yield of aromatic hydrocarbons (benzene and toluene) by a factor of 8.8 over the arene yield observed in individual n-pentane conversion. A mass spectrometric analysis of the arenes obtained with the Pt/Al₂O₃ catalyst has demonstrated that 37.5% of the adsorbed methane is involved in the methane–n-pentane coaromatization yielding benzene and toluene.     

Electrical properties of poly(bis(β-phenoxyethoxy)phosphazene) and its complexes

Electrical and dielectrical properties of poly(bis(-phenoxyethoxy)phosphazene) (I) and its complexes with various content ratios of AgSO₃CF₃ to monomeric unit (0.25/1 (II) and 0.5/1 (III) in molar ratio) were investigated.Dc conductivity of respective samples at 18 °C were 6.1×10^–12, 4.4×10^–9, and 7.1×10^–8 S/m.Dc conduction was considered to be due to ion hopping. Charge mobility ranged from 3×10^–12 to 6× 10^–11 m²/Vs depending on the applied field in sample II. In sample I, a tan peak was found which can be ascribed to molecular relaxation of main chains. The peak vanished upon introducing AgSO₃ CF₃. Temperature dependence of total conductivity ( _T ) measured byac method in the temperature range between –150 °C and 50 °C showed several peaks at the temperatures corresponding to the peak temperatures of tan. Total conductivities of respective samples at 100 kHz were 4.9×10^–7 (69 °C), 1.7×10^–4 (45 °C), and 1.5×10^–4(40°C)S/m.     

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.     

Effect of Thermal Activation of Supported Catalysts Pt/MeOx,Where MOx = Al2O3, CeO2, La2O3, and ZrO2, for Complete Oxidation

A sharp increase in the atomic catalytic activity (ACA) of supported platinum catalysts in the model reaction of n-pentane complete oxidation is found on going from the preliminary calcination temperature of 500–600°C to a temperature of 700°C. ACA increases by an order of magnitude for the Pt/-Al₂O₃ system, 3 times for Pt/ZrO₂, and 1.5 times for Pt/CeO₂. The per-gram activities of all catalysts decrease because of a decrease in the dispersion of supported platinum with an increase in the temperature of preliminary calcination.     

Isomerization of n-Hexane Over Platinum Ion-Exchanged Zeolite Beta

Zeolite Beta was synthesized from appropriate gels and crystallized under the controlled temperature and pressurized conditions. For isomerization of n-hexane, platinum ion-exchanged zeolite Beta exhibited high activity and selectivity for 2,2-dimethylbutane (2,2-DMB), 2,3-dimethylbutane (2,3-DMB), 2-methylpentane (2-MP) and 3-methylpentane (3-MP). As high as 72% of n-hexane conversion and 98% of product selectivity were obtained at 250°C, 1600 h^–1 for 20 min on stream. The influences of reaction temperature and space velocity were also studied. Pt/H-Beta zeolite was recommended as one of the promising catalyst for n-hexane isomerization due to its high activity and stability. The combined effect of the stronger acidity possessed by H-Beta and the dehydrogenation role played by Pt was believed to be responsible for the good catalytic performance of Pt/H-Beta.     

Bis(di-tert-butylcyclopentadienyl)ytterbium(ii). Synthesis and catalytic properties

Polymeric (Cp₂Yb·THF) _n (1), ionicate-complex Cp₃YbNa (2), and mono-adduct (Bu^t ₂C₅H₃)₂Yb·THF (3) were prepared through a reaction of CpNa (Cp = C₅H₅ or C₅H₃Bu^t ₂) with Ybl₂ in THF. Cooling complex (3) in THF at –100 °C gives a bis-adduct, which reversibly dissociates to give the mono-adduct, The (Bu^t ₂C H , Yb·THF complex shows catalytic activity in the homogeneous hydrogenation of hex-l-ene and in the polymerization of styrene.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No, 7, pp. 1833–1837, July, 1996.     

NOx-Sorbing Metal Oxides, MnOx–CeO2. Oxidative NO Adsorption and NOx–H2 Reaction

(n)MnO_x–(1–n)CeO₂ binary oxides have been studied for the sorptive NO removal and subsequent reduction of NO_x sorbed to N₂ at low temperatures (150 °C). The solid solution with a fluorite-type structure was found to be effective for oxidative NO adsorption, which yielded nitrate (NO^– ₃) and/or nitrite (NO^– ₂) species on the surface depending on temperature, O₂ concentration in the gas feed, and composition of the binary oxide (n). A surface reaction model was derived on the basis of XPS, TPD, and DRIFTS analyses. Redox of Mn accompanied by simultaneous oxygen equilibration between the surface and the gas phase promoted the oxidative NO adsorption. The reactivity of the adsorbed NO_x toward H₂ was examined for MnO_x–CeO₂ impregnated with Pd, which is known as a nonselective catalyst toward NO–H₂ reaction in the presence of excess oxygen. The Pd/MnO_x–CeO₂ catalyst after saturated by the NO uptake could be regenerated by micropulse injections of H₂ at 150 °C. Evidence was presented to show that the role of Pd is to generate reactive hydrogen atoms, which spillover onto the MnO_x–CeO₂ surface and reduce nitrite/nitrate adsorbing thereon. Because of the lower reducibility of nitrate and the competitive H₂–O₂ combustion, H₂–NO reaction was suppressed to a certain extent in the presence of O₂. Nevertheless, Pd/MnO_x–CeO₂ attained 65% NO-conversion in a steady stream of 0.08% NO, 2% H₂, and 6% O₂ in He at as low as 150 °C, compared to ca. 30% conversion for Pd/–Al₂O₃ at the same temperature. The combination of NO_x-sorbing materials and H₂-activation catalysts is expected to pave the way to development of novel NO_x-sorbing catalysts for selective deNO_x at very low temperatures.     

Synthesis and transformations of metallacycles. 23. Cp2TiCl2-Catalyzed cyclometallation of fullerene C60 with EtAlCl2

1-Ethyl-2,3-fullerenoaluminacyclopropanes (EtAl)_n(²-C₆₀) were synthesized by the reaction of fullerene C₆₀ with an excess of EtAlCl₂ in the presence of Mg and using Cp₂TiCl₂ as the catalyst in a THF--toluene solution at 20 °C. Deuterolysis of fullerenoaluminacyclopropanes afforded a mixture of deuteriofullerenes C₆₀D_m, where m = 6--12.