A Series of monohapto pyrazolates of iridium(I) and iridium(III)

The reaction of trans-IrCl(CO)L₂ with pz^?1 gives trans-Ir(pz-N)(CO)L₂, where pzH is 3,5-dimethyl-, 3,5-dimethyl-4-nitro- or 3,5-bis(trifluoromethyl)-pyrazole, and L = PPh₃. The nitrogen atom not involved in coordination can be protonated with HBF₄ to give the corresponding [Ir(CO)L₂(pzH-N]⁺ cation. The iridium(I) pyrazolates undergo oxidative addition, yielding Ir(H)₂(pz-N)(CO)L₂ species, while gaseous HCl cleaves the IrN bond, affording IrH(Cl)₂(CO)L₂. The iridium(I) derivatives can be obtained in several solid-state forms, each characterized by a slightly different CO stretching frequency. The presence of a monodentate pyrazolato ligand in trans-Ir(3,5-(CF₃)₂pz-N)(CO)L₂, in the form with ν(CO) at 1975 cm^?1, is supported also by an X-ray crystal structure determination. The compound crystallizes in the monoclinic system, space group P2₁/n, with cell dimensions a = 21.106(6), b = 19.700(5), c = 9.437(2) Å, and β = 94.34(2)° and Z = 4.     

Hydroisomerization of n-heptane over bimetal-bearing H3PW12O40 catalysts supported on dealuminated USY zeolite

The bimetal-bearing (CePt or LaPt) 12-tungstophosphoric acid (H₃PW₁₂O₄₀ (PW)) catalysts supported on dealuminated USY zeolite (DUSY) were prepared by impregnation and characterized by XRD, BET, IR, and H₂-chemisorption. Their catalytic activities were tested in the hydroisomerization of n-heptane with a continuous atmospheric fixed-bed reactor. After the steam treatment combined with the acid leaching, as well as the supporting with PW and the bimetals, the DUSY support retains the Y zeolite porosity and the PW well keeps its Keggin structure in catalysts. The doping of Ce into the catalysts enhances the dispersion of Pt on the catalyst surface. The Pt-bearing PW catalysts doped with Ce or La, especially Ce, exhibit much higher catalytic activity and selectivity than the catalysts without dopants at lowered reaction temperatures. At the optimal reaction conditions, i.e., the reaction temperature of 250°C and WHSV of 1.4 h^?1, the catalyst with a Pt loading of 0.4%, PW loading of 10% and a molar ratio of Ce to Pt of 15:1 shows a conversion of n-heptane of 70.3% with a high selectivity for isomerization products of 94.1%.     

New Concepts for Designing d10‐M(L)n Catalysts: d Regime,s Regime and Intrinsic Bite‐Angle Flexibility

Our aim is to understand the electronic and steric factors that determine the activity and selectivity of transition‐metal catalysts for cross‐coupling reactions. To this end, we have used the activation strain model to quantum‐chemically analyze the activity of catalyst complexes d¹⁰‐M(L)_n toward methane C?H oxidative addition. We studied the effect of varying the metal center M along the nine d¹⁰ metal centers of Groups 9, 10, and 11 (M=Co^?, Rh^?, Ir^?, Ni, Pd, Pt, Cu⁺, Ag⁺, Au⁺), and, for completeness, included variation from uncoordinated to mono‐ to bisligated systems (n=0, 1, 2), for the ligands L=NH₃, PH₃, and CO. Three concepts emerge from our activation strain analyses: 1) bite‐angle flexibility, 2) d‐regime catalysts, and 3) s‐regime catalysts. These concepts reveal new ways of tuning a catalyst’s activity. Interestingly, the flexibility of a catalyst complex, that is, its ability to adopt a bent L‐M‐L geometry, is shown to be decisive for its activity, not the bite angle as such. Furthermore, the effect of ligands on the catalyst’s activity is totally different, sometimes even opposite, depending on the electronic regime (d or s) of the d¹⁰‐M(L)_n complex. Our findings therefore constitute new tools for a more rational design of catalysts.     

Cationic η-benzyl nickel compounds with diphosphine ligands as catalyst precursors for ethylene oligomerization/polymerization: influence of the diphosphine bite angle

The oligomerization and/or polymerization of ethylene catalyzed by the cationic η³-benzylcomplexes [Ni(η³-CH₂C₆H₄-p-CF₃)(P-P)]⁺ BPh₄⁻ (P-P=ⁱPr₂P(CH₂)_nPⁱPr₂, n=1-3) have been studied. The activity of these single component catalysts depends on the length of the (CH₂)_n bridge of the diphosphine ligand. Thus, the dippm derivative (n=1) displays higher activity than compounds of the dippe (n=2) or dippp (n=3) ligands. The molecular weight of the products is also a function of n, and varies in the order dippm > dippe > dippp, with the former two catalysts giving rise to low molecular weight polyethylenes and the latter to oligomers.     

Ethylene polymerization with FI complexes having novel phenoxy‐imine ligands: Effect of metal type and complex immobilization

A series of bis(phenoxy‐imine) vanadium and zirconium complexes with different types of R³ substituents at the nitrogen atom, where R³ = phenyl, naphthyl, or anthryl, was synthesized and investigated in ethylene polymerization. Moreover, the catalytic performance was verified for three supported catalysts, which had been obtained by immobilization of bis[N‐(salicylidene)‐1‐naphthylaminato]M(IV) dichloride complexes (M = V, Zr, or Ti) on the magnesium carrier MgCl₂(THF)₂/Et₂AlCl. Catalytic performance of both supported and homogeneous catalysts was verified in conjunction with methylaluminoxane (MAO) or with alkylaluminium compounds (Et_nAlCl_3?n, n = 1–3). The activity of FI vanadium and zirconium complexes was observed to decline for the growing size of R³, whereas the average molecular weight (MW) of the polymers was growing for larger substituent. Moreover, vanadium complexes exhibited the highest activity with EtAlCl₂, whereas zirconium ones showed the best activity with MAO. All immobilized systems were most active in conjunction with MAO, and their activities were higher than those for their homogeneous counterparts, and they gave polymers with higher average MWs. That effect was in particular evident for the titanium catalyst. The vanadium complex 3 was also a good precursor for ethylene/1‐octene copolymerization; however, its immobilization reduced its potential for incorporation of a comonomer into a polyethylene chain. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

State of iridium supported on SO4/ZrO2

The Ir/ZrO₂ and Ir/SO₄/ZrO₂ systems were studied by diffuse-reflectance IR spectroscopy using CO as a probe molecule. After reduction of 0.5% Ir/ZrO₂ in flowing hydrogen at 200°C, the state of iridium is essentially Ir⁰, as in the iridium systems supported on amphoteric oxide supports. For Ir/SO₄/ZrO₂, the stabilization of ionic forms of the metal, the formation of species with a partial positive charge, and an increase in the frequencies of CO adsorbed on Ir⁰ particles, as compared with systems without sulfur, are found. At a concentration as low as 0.1 wt.%, iridium exists substantially as Ir³⁺ ions or small Ir^?+ particles. An increase in the concentration of iridium to 0.5 wt.% leads to the formation of the bulk Ir _n ⁰ phase, whose fraction increases as the iridium content increases. This phase predominates in the samples with 2.5 wt.% iridium.     

AIB induced chemical reactions at surfaces detected by SIMS

Secondary ion mass spectrometry (SIMS) has been used to detect the reactions induced by active ion bombardment (AIB) of N⁺₂ on surfaces of pyrolytic graphite and a (100) Si crystal. The SIMS spectra exhibit ions of CN^?, HCN^?, H_nC₂N^?(n = 2, 3, 4), HN^?, and SiN^?, indicating that reactions take place with the graphite and silicon as well as adsorbed hydrogen on the surfaces.     

Second coordination sphere of aluminium and gallium hexacoordination complexes

It is shown by means of ¹⁹F NMR that the hexacoordinated solvates of aluminium and gallium in solutions of methyl, ethyl and n-propyl alcohols form outer-sphere complexes with the halide ions, F^?, Cl^? and Br^?, in which the acidoligands are situated in the second coordination sphere. The outer-sphere complexes are formed on the basis of purely alcoholic solvates, M(ROH)₆³⁺, as well as the complexes containing the mixed coordination sphere, M(ROH)_6?n(H₂O)_n³⁺, and Al(CH₃OH)_6?n(C₂H₅OH)_n²⁺.     

Gas-phase solvation of protonated aliphatic amines: methyl,ethyl, n-propyl,and iso-propylamine

The thermodynamic quantities K_{n?1 n}, ΔG⁰_{n?1, n} and ΔS⁰_n?1, n for the gas phase equilibrium reactions RNH⁺₃(RNH₂)_n?1 + RNH₂ = RNH⁺₃(RNH₂)_n, where n ? 3 and R indicates an alkyl group (CH₃, C₂H₅, n-C₃H₇ and iso-C₃H₇), have been determined.     

Metallic osmium and ruthenium nanoparticles for CO oxidation

Supported metallic catalysts were prepared from pyrolysis of the organometallic clusters RuOs₃(CO)₁₃(μ-H)₂, Os₃(CO)₁₀(μ-AuPPh₃)₂, Os₃(CO)₁₂, Ru₃(CO)₁₂ and [Ru(CO)₄]_n, on either silica or titania, and their catalytic performance for CO oxidation has been assessed against a supported catalyst prepared from RuCl₃. Ruthenium catalysts prepared from organometallic precursors were found to exhibit better activity, and that supported on TiO₂ exhibited activity at the lowest operating temperature.     

Catalytic Activity for Ammonia Synthesis of Iron Supported Catalysts Prepared from an Acid-modified λ-Al2O3 Method

Iron supported catalysts were prepared by impregnation of several acid-modified λ-Al₂O₃ samples with a K₄[Fe(CN)₆] aqueous solution. A concentration range between 0–20 mmole H⁺ added · g^?1λ-Al₂O₃ was used. The quantitative determination of the acid site and iron contents of the modified λ-Al₂O₃ samples was followed by UV spectrometry and F.A.A.S., respectively. An increasing final iron content of the catalysts with increasing acid site content of the support is observed. The catalytic activity for ammonia synthesis was followed at atmospheric pressure and 593 K (N₂/H₂ = 1/3). An increasing ammonia production per gram of catalyst with increasing protonation of the support was observed in the range 0–8 mmole H⁺ added · g^?1λ-Al₂O₃. The catalytic activity of iron supported catalysts prepared by this method was higher (up to twofold) that of a catalyst prepared by the incipient wetness method.     

Cu(II) and Co(II) complexes with 3,5-diphenyl-4-amino-1,2,4-triazole: Synthesis and study

The Cu(II) and Co(II) complexes with 3,5-diphenyl-4-amino-1,2,4-triazole (L) of the composition CuLA₂ · H₂O (A = Cl^?, Br^?), CuL₂A₂ (A = Cl^?, Br^?, NO ₃ ^? ), CoL₂A₂ · nH₂O (A = Cl^?, n = 1; A = NCS^?, n = 0) are synthesized. In these complexes, the ligand L is coordinated to a metal in monodentate mode through the heterocyclic N(1) atom. The Cu: L = 1: 1 complexes have binuclear structures with the anions acting as bridges, whereas the M: L = 1: 2 complexes are mononuclear. Both ferro-and antiferromagnetic exchange interactions are detected for the synthesized complexes.     

Microwave-assisted Ni–La/γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst for benzene hydrogenation

A series of Ni–La/γ-Al₂O₃ catalysts were prepared by adopting the methods of isometric impregnation and microwave impregnation. The catalysts were characterized with XRD, BET, and SEM, respectively. Inspecting the effects of adding La and the methods of impregnation on the hydrogenation activity of catalysts. The results show that adding a moderate amount of La promotes the dispersing of Ni on the carrier, the methods of microwave impregnation weaks the interaction between Ni and the carrier further, inhibits the formation of NiAl₂O₄, and the activity of catalyst prepared by the methods of microwave impregnation was significantly higher than that prepared by the methods of isometric impregnation. The hydrogenation activity of the Ni–La/γ-Al₂O₃ (WB) dipped with n(Ni): n(La) = 4: 1, microwave irradiation time 30 min with power 600W as well as calcined at 400°C exhibited the best performance. The conversion rate is 91.21% with reaction conditions: T = 160°C, p = 0.8 MPa, air speed 5 h^–1, n(H₂): n(benzene) = 2: 1.     

A flowing afterglow study of uranium tetraborohydride

Ionization-fragmentation of uranium(IV) tetraborohydride, U(BH₄)₄, by He⁺ and by N⁺/N₂⁺ yields, predominantly, U(BH₅)⁺ and U(B₂H₈)⁺, respectively. Attachment of thermal electrons yields U(BH₄)₄^? and ions of 1, 2, and 3 mass units less. Fluoride transfer with SF₆^?, BF₄^?, and UF_n^? (n = 5–7) and reactions with other small ions (O^?, O₂^?, NO₂^?, F^?, Cl^?, O₂⁺) are described.     

Rhodium and iridium complexes of N-heterocyclic carbenes: Structural investigations and their catalytic properties in the borylation reaction

Bridged and unbridged N-heterocyclic carbene (NHC) ligands are metalated with [Ir/Rh(COD)₂Cl]₂ to give rhodium(I/III) and iridium(I) mono- and biscarbene substituted complexes. All complexes were characterized by spectroscopy, in addition [Ir(COD)(NHC)₂][Cl,I] [COD = 1,5-cyclooctadiene, NHC =  1,3-dimethyl- or 1,3-dicyclohexylimidazolin-2-ylidene] (1, 4), and the biscarbene chelate complexes 12 [(η⁴-1,5-cyclooctadiene)(1,1′-di-n-butyl-3,3′-ethylene-diimidazolin-2,2′-diylidene)iridium(I) bromide] and 14 [(η⁴-1,5-cyclooctadiene)(1,1′-dimethyl-3,3′-o-xylylene-diimidazolin-2,2′-diylidene)iridium(I) bromide] were characterized by single crystal X-ray analysis. The relative σ-donor/π-acceptor qualities of various NHC ligands were examined and classified in monosubstituted NHC-Rh and NHC-Ir dicarbonyl complexes by means of IR spectroscopy. For the first time, bis(carbene) substituted iridium complexes were used as catalysts in the synthesis of arylboronic acids starting from pinacolborane and arene derivatives.     

Effect of inorganic oxide supports on the activity of chromium‐based catalysts in ethylene trimerization

Novel heterogeneous catalysts were prepared using immobilization of bis(2‐decylsulfanylethyl)amine–CrCl₃ (Cr‐SNS‐D) on various supports, namely commercial TiO₂, Al₂O₃ and magnetic Fe₃O₄@SiO₂ nanoparticles, to yield solid catalysts denoted as support@Cr‐SNS‐D. The structure of the catalysts was confirmed on the basis of spectroscopic analyses, N₂ adsorption–desorption and inductively coupled plasma (ICP) analysis. The surface areas of Al₂O₃@Cr‐SNS‐D, Fe₃O₄@SiO₂@Cr‐SNS‐D and TiO₂@Cr‐SNS‐D catalysts were determined to be 70, 23 and 41 m² g^?1, respectively. A decrease in surface area from that of the supports clearly establishes accurate immobilization of Cr‐SNS‐D catalyst on the surface of the parent carriers. The loading of Cr was determined to be 0.02, 0.16 and 0.11 mmol g^?1 for Cr‐SNS‐D supported on TiO₂, Al₂O₃ and Fe₃O₄@SiO₂, respectively, using ICP analysis. After preparation and full characterization of the catalysts, ethylene trimerization reaction was accomplished in 40 ml of dry toluene, at 80°C and 25 bar ethylene pressure and in the presence of methylaluminoxane (Al/Cr = 700) within 30 min. The supported chromium catalysts were found to be efficient and selective for the ethylene trimerization reaction. The highest activity (74 650 g_1‐hexene g_Cr^?1 h^?1), as well as no polyethylene formation during reaction processes, was observed when TiO₂ was used as the catalyst support.     

小麦粉衍生中孔氮掺杂颗粒炭负载金催化剂用于乙炔氢氯化反应（英文）

聚氯乙烯是五大工程塑料之一,在国民经济中占有重要的地位.基于中国富煤少油缺气的能源格局,我国主要采用基于煤化工的电石法氯乙烯生产工艺,但该工艺必须采用氯化汞催化剂,受到国际限汞公约的影响,无汞催化剂的开发迫在眉睫.其中炭负载金催化剂在该反应中活性最高,近几年来取得了较大进展,有望实现产业化.氮掺杂的炭材料在诸多反应中展现了较好的性能,其负载金属催化剂可以有效提高金属的分散度及稳定性,成为近几年多相催化领域的一个研究热点.最近我们课题组报道了一种氮掺杂中孔成型的制备方法:以小麦粉为原料,通过直接炭化法制备了氮掺杂中孔成型炭,这种氮掺杂中孔成型炭作为无汞催化剂在乙炔氢氯化反应中显示出了优异的催化性能.小麦粉衍生的氮掺杂中孔成型炭具有成型容易.原料价廉易得、易于放大生产等优点,是优选的工业化催化剂的载体.本文以这种氮掺杂的成型炭为载体制备了负载型金催化剂,研究其催化乙炔氢氯化性能.结果表明,氮的掺杂使得中孔炭负载金(Au/N-MC)催化剂上乙炔氢氯化活性明显提高.在氯化氢/乙炔比例1.1、反应温度180℃、乙炔空速600 h~(-1)的条件下,Au/N-MC上的乙炔转化率为50%,是Au/MC催化剂活性的2倍.通过对催化剂的表征发现,氮的掺杂能有效地锚定Au/N-MC催化剂中活性组分Au~(3+),抑制催化剂制备过程中Au~(3+)还原为Au~0,从而提高催化剂活性和稳定性.小麦粉衍生的氮掺杂中孔炭的原料廉价易得,生产工艺简单,易成型,也容易实现工业化生产,是负载型金属催化剂的优良载体,其负载的无汞催化剂性能优越,有望取代电石法氯乙烯产业的汞催化剂,成为新一代无汞催化剂.     

C3i‐Symmetric Octanuclear Cadmium Cages: Double‐Anion‐Templated Synthesis,Formation Mechanism,and Properties

A series of C_3i‐symmetric bicapped trigonal antiprismatic Cd₈ cages [2X@Cd₈L₆(H₂O)₆] ? n Y ? solvents (X=Cl^?, Y=NO₃^?, n=2: MOCC‐4 ; X=Br^?, Y=NO₃^?, n=2: MOCC‐5 ; X=NO₃^?, Y=NO₃^?, n=2: MOCC‐6 ; X=NO₃^?, Y=BF₄^?, n=2: MOCC‐7 ; X=NO₃^?, Y=ClO₄^?, n=2: MOCC‐8 ; X=CO₃^2?, n=0: MOCC‐9 ), doubly anion templated by different anions, were solvothermally synthesized by means of a flexible ligand. Interestingly, the CO₃^2? template for MOCC‐9 was generated in situ by two‐step decomposition of DMF solvent. For other MOCCs, spherical or trigonal monovalent anions could also play the role of template in their formation. The template abilities of these anions in the formation of the cages were experimentally studied and are discussed for the first time. Anion exchange of MOCC‐8 was carried out and showed anion‐size selectivity. All of the cage‐like compounds emit strong luminescence at room temperature.     

Polydentate phosphine oxides as external electron donors for titanium-magnesium catalysts for propylene polymerization

The possibility of using R _n P(O)(CH₂OR′)_3—n (R = alkyl, R′ = methyl or acyl, n = 0–2) polydentate phosphine oxides as external electron donors for the titanium-magnesium catalysts for isotactic polypropylene synthesis is demonstrated for the first time. The kinetics of propylene polymerization in liquid monomer at 70°C and the isotacticity and molecular-weight characteristics of the resulting polypropylene are studied as functions of the nature of the substituents at the phosphorus atoms in the external donor and the molar ratio of the cocatalyst AlEt₃ to the external electron donor. Among the compounds examined, isoamyldi(methoxymethyl)phosphine oxide (R = iso-Am, R′ = Me, n = 1) is the most efficient. The isotacticity index of the polypropylene (PP) synthesized on the titanium-magnesium catalyst with this external donor is as high as 94–95%, and the activity of the catalyst (Cat) in the absence of hydrogen is 5.0–6.5 (kg PP) (g Cat)^?1 h^?1. With the optimum combination, the activity of this catalyst is ≈5 (kg PP) (g Cat)^?1 h^?1 and the isotacticity index is 94%. These parameters are close to those obtained for propylene polymerization in the absence of hydrogen on the same titanium-magnesium catalyst with phenyltriethoxysilane (external donor used in the industrial synthesis of PP): the activity is 5.6 (kg PP) (g Cat)^?1 h^?1, and the isotacticity index is 95%. The introduction of hydrogen into the reaction zone makes it possible to efficiently control the molecular weight of PP, increases the catalyst activity by a factor of 1.5–2.5, and somewhat decreases the isotacticity index (from 94 to 91–92%).     

Purification, Characterization, and Specificity Determination of a New Serine Protease Secreted by Penicillium waksmanii

The purpose of this work was to purify a protease from Penicillium waksmanii and to determine its biochemical characteristics and specificity. The extracellular protease isolated that was produced by P. waksmanii is a serine protease that is essential for the reproduction and growth of the fungus. The protease isolated showed 32 kDa, and has optimal activity at pH 8.0 and 35 °C towards the substrate Abz-KLRSSKQ-EDDnp. The protease is active in the presence of CaCl₂, KCl, and BaCl, and partially inhibited by CuCl₂, CoCl₂ and totally inhibited by AlCl₃ and LiCl. In the presence of 1 M urea, the protease remains 50 % active. The activity of the protease increases 60 % when it is exposed to 0.4 % nonionic surfactant-Triton X-100 and loses 10 % activity in the presence of 0.4 % Tween-80. Using fluorescence resonance energy transfer analysis, the protease showed the most specificity for the peptide Abz-KIRSSKQ-EDDnp with k _cat/K _m of 10,666 mM^?1?s^?1, followed by the peptide Abz-GLRSSKQ-EDDnp with a k _cat/K _m of 7,500 mM^?1?s^?1. Basic and acidic side chain-containing amino acids performed best at subsite S₁. Subsites S₂, S₃, S^′ ₂, and S^′ ₁, S^′ ₃ showed a preference for binding for amino acids with hydrophobic and basic amino acid side chain, respectively. High values of k _cat/K _m were observed for the subsites S₂, S₃, and S^′ _2. The sequence of the N-terminus (ANVVQSNVPSWGLARLSSKKTGTTDYTYD) showed high similarity to the fungi Penicillium citrinum and Penicillium chrysogenum, with 89 % of identity at the amino acid level.