bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Theoretical Study of Thionitrosyl Azide (N3NS), Thiazyl Azide (N3SN) and Nitrosyl Azide (N3NO)
Authors: Nguyen Minh Tho , Flammang Robert 
Published: July 2007

AbstractStimulated by the recent detection of nitrosyl azide (N3NO), we investigated the stability of the sulfur analogues thionitriosyl azide (N3NS) and thiazyl azide (N3SN) by using ab initio MO calculations up to the QCISD(T)/6‐311+G(d)//QCISD/6‐311G(d) + ZPE level. Both azides have a similar energy content. While thionitrosyl azide is not stable with respect to N2 elimination, thiazyl azide resists to this process by an energy barrier of about 110 kJ/mol. The NS and N3 fragments resulting from homolytic cleavage lie about 100 kJ/mol above the azides. The five‐membered ring is thermodynamically much more stable than both azides but kinetically unstable with respect to cheletropic decomposition yielding N2S + N2. Overall, trans‐thiazyl azide is the most likely candidate for experimental observation of, for example, the reaction of NS+ salts with the azide anion. IR wavenumbers of the azides were also predicted.
Preparation and Reactivity of Tris(trifluoromethylselanyl)carbenium [(CF3Se)3C+] and Trifluoromethylsulfanylacetic Acid Derivatives [(CF3S)3–nCXn(O)R]
Authors: Haas Alois , Möller Guido 
Published: July 2007

AbstractReaction pathways for the synthesis of the (CF3E)3C moieties (E = Se, S) are described. [(CF3Se)3C+][AsF] was found to be a suitable synthon for the preparation of (CF3Se)3C derivatives. It can be prepared either from (CF3Se)3C derivatives. It can be prepared either from (CF3Se)4C or (CF3Se)3CF and AsF5 in liquid SO2. Direct access to (CF3Se)3CF was realized by the reaction of FCBr3 with Hg(SeCF3)2. Treatment of [(CF3Se)3C+][AsF6‐] with potassium halides provided (CF3Se)3CX (X = F, Cl, Br). A different course took the reaction with KI, as CF3SeSeCF3 and (CF3Se)2C=C(SeCF3)2 were formed as main products. Minor amounts of (CF3Se)3CC(SeCF3)3 were formed which could be isolated and unambiguously characterized. Only two routes led to a threefold CF3S‐substituted acetic acid ester (CF3S)3CC(O)OR [R = CH3, (CH3)3C]: Metatheses between (CF3S)2CBrC(O)OCH3 and Hg(SCF3)2 and metalation of (CF3S)2CHC(O)OR [R = CH3, (CH3)3C] with NaH followed by reaction with CF3SCl. Other precursors such as (CF3S)2CXC(O)OR′ [X = H, Br; R′ = Me3Si, (n‐C4H9)3Sn] and (CF3S)2CBrC(O) Y (Y = Cl, Br) were synthesized but could not be converted to the corresponding (CF3S)3C derivatives. Attempts to hydrolyze (CF3S)3CC(O)OR to (CF3S)3CC(O)OH failed.
Preparation and X‐ray Crystal Structure of the First Trimeric Nickel Thiosemicarbazone Complex: The First Example of Oligomerization by both NiONi and NiSNi Bridging
Authors: Berkessel Albrecht , Hermann Gesine , Rauch Olga‐Tatjana , Büchner Michael , Jacobi Albrecht , Huttner Gottfried 
Published: July 2007

AbstractMonomeric nickel(II) thiosemicarbazone complexes are an attractive new class of homogeneous catalysts for the activation of silanes. However, their activity is limited by the formation of inactive oligo‐ and polymers. The pathway by which aggregation takes place was elucidated by the preparation and X‐ray structural analysis of the first trimeric nickel(II) thiosemicarbazone complex. Aggregation was shown to proceed via NiONi and NiSNi bridging, giving rise to both fourfold planar and pseudooctahedral coordination of the nickel ions.
Synthesis and Substituent Interactions of Tricarbonylchromium‐complexed Arylalkynylbenzenes — Novel Organometallic Push‐pull Chromophores
Authors: Müller Thomas J. J. , Ansorge Markus , Lindner Hans Jörg 
Published: July 2007

AbstractThe tricarbonylchromium complexes chlorobenzene 1 reacts with terminal alkynes 2 through a palladium‐copper‐catalyzed coupling to give a variety of Cr(CO)3‐complexed phenylethynyl arenes, heteroarenes and ferrocene 3 in good to excellent yield. Due to the electron‐withdrawing nature of the Cr(CO)3 group these novel complexes can be regarded as organometallic push‐pull chromophores. Analogously, the corresponding free ligands 4 (phenylethynyl arenes, heteroarenes and ferrocene) were synthesized by coupling iodobenzene and 2. The crystal structure analysis of the singly Cr(CO)3‐complexed tolane 3e reveals a strong deviation from coplanarity of both phenyl rings by an angle of 50.9(2)° presumably due to crystal packing. Correlations are established between selected substituent parameters (σP, σI, σR, σP+ and Δπ) and the carbonyl carbon resonances in the 13C‐NMR spectra for the complexes 3. The overall electronic substituent effect is transmitted to the carbonyl groups by both mesomeric and inductive mechanisms. The push‐pull complexes 3 display relatively small negative solvochromicities of longest wavelength absorption band (MLCT band).
Synthesis and Stereochemistry of the First Chiral (Imidazolinylidene)‐ and (Triazolinylidene)palladium(ii) Complexes
Authors: Enders Dieter , Gielen Heike , Raabe Gerhard , Runsink Jan , Teles J. Henrique 
Published: July 2007

AbstractThe reaction of three equiv. of a chiral imidazolium or triazolium perchlorate with one equiv. of Pd(OAc)2, an excess of NaI and a base leads to the corresponding chiral dicarbenediiodopalladium(II) complexes in chemical yields up to 98% and with the trans isomer as the major product (1, 2). If only one equiv. of the imidazolium or triazolium perchlorate is used, then dinuclear complexes with bridging iodine atoms are formed (3, 4, chemical yield 92—94%). The latter can add Lewis basic ligands, e.g. amines, phosphanes or other carbenes, to give mononuclear complexes with one carbene ligand coordinated to the PdI2 fragment (5, 6). Preliminary test experiments with these Pd(II) complexes as catalysts for an enantioselective Heck‐type reaction have been carried out.
The Interlocking of Salicylic Aldehydes and Ketones with a 2h‐1,2,4,3‐Triazaphosphole
Authors: Schmidpeter Alfred , Steinmüller Franz , Nöth Heinrich 
Published: July 2007

AbstractSalicylic aldehyde (2a) adds to 2‐methyl‐5‐phenyl‐2H‐1,2,4,3‐triazaphosphole (1) to yield the bicyclic phosphonic amide 3a. The OH group adds to the P=N bond, the carbon atom the carbonyl group is inserted into the other P—N bond, and the phosphorus atom is oxidized. In the crystal the compound forms dimers by a double hydrogen bond between two HN‐PO units. Substituted salicylic aldehydes as well as ortho‐hydroxyacetophenone and benzophenone react in the same way.
Phosphazenes with (2‐Pyridylmethylamino) Groups, I. Syntheses and Crystal Structures of Pentaphenoxy(2‐pyridylmethylamino)‐cyclotriphosphazene and Its Copper(II) Nitrate, Platinum (II) Chloride, and Cobalt(II) Nitrate Complexes
Authors: Diefenbach Ursula , Kretschmann Michael , Stromburg Brigitte 
Published: July 2007

AbstractThe reaction of the (2‐pyridylmethylamino)‐substituted cyclotriphosphazene N3P3(OC6H5)5(NHCH2(C5H4N)‐2) (1) with copper(II) nitrate, platinum(II) chloride, and cobalt(II) nitrate yields the stable complexes [Cu(NO3)2·(1)2] (1a), [PtCl2·(1)] (1b), [Co(NO3)2 · (1)] (1c). The X‐ray crystallographic studies of these metal complexes revealed the different coordination behavior of the multifunctional ligand.
Halogen/Metal vs. Hydrogen/Metal Exchange: General or Specific Site Selectivity as Exemplified in the Camphene Series
Authors: Garamszegi László , Schlosser Manfred 
Published: July 2007

Abstract(Z)‐(3,3‐Dimethylbicyclo[2.2.1]hept‐2‐ylidene)methyllithium can be readily generated by treatment of (Z)‐3‐bromomethylene‐2,2‐dimethylbicyclo[2.2.1]heptane with tert‐butyl‐lithium. At ‐75°C, the organometallic intermediate is configurationally stable and reacts with a variety of electrophiles under stereochemical retention.
Synthesis and Structure of Binuclear Single‐Bridged Bis[(phosphane)gold(I)]halogenonium Complexes
Authors: Bayler Angela , Bauer Andreas , Schmidbaur Hubert 
Published: July 2007

AbstractReactions of (R3P)AuX (X = Cl, Br, I) with [(R3P)Au]+ BF−4 obtained from (R3P)AuCl and AgBF4 in tetrahydrofuran, lead to cationic binuclear gold(I) complexes of the general formula ([(R3P)Au]2X}+ BF−4. A number of chloro‐ (R = Ph, o‐Tol, Mes, Bzl, Et), bromo‐ (R = Ph, o‐Tol, Mes) and iodo‐bridged (R = Ph, Mes) complexes of this type have been isolated and identified on the basis of their analytical and spectroscopic data. The crystal structure of bis[(triphenylphosphane)gold(I)]bromonium tetrafluoroborate was determined by single‐crystal X‐ray diffraction. The cations contain two‐coordinate bromine atoms with an Au‐Br‐Au angle of 96.83(3)°.
Chemie polyfunktioneller Moleküle, 125 Synthese und Kristallstruktur von N,N,N′,N”︁,N‐Pentamethyl‐diethylentriamin‐cokoordiniertem Kalium‐bis(diphenylphosphanyl)amid
Authors: Ellermann Jochen , Schütz Martin , Heinemann Frank W. , Moll Matthias , Bauer Walter 
Published: July 2007

AbstractThe metalation of bis(diphenylphosphanyl)amine [HN‐(PPh2)2,1 with KOtBu at 95°C in toluene affords a pale yellow precipitate of potassium bis(diphenylphosphanyl)amide (3a). On addition of liquid N,N,N′,N”︁,N”︁‐pentamethyldiethylenetriamine (PMDTA, 4) the precipitate dissolves in toluene at 115°C to give a yellow solution, from which yellow‐green blocks of [(Ph2P)2NK·PMDTA] (3b) are obtained. X‐ray analysis reveals that the coordination sphere of potassium consists of the chelating triamine ligand and [N(PPh2)2]− as N‐donor as well as η1 and η2 C‐donor with two phenyl fragments. No phosphorus coordination of [N(PPh2)2]− is observed.
Cobalt‐Catalyzed Selective Oxidation of the Tritertiary Phosphane Triphos with Molecular Oxygen
Authors: Heinze Katja , Huttner Gottfried , Zsolnai Laszlo 
Published: July 2007

AbstractThe reactivity of complexes of triphos [CH3C(CH2PPh2)3] and CoCl2 towards dioxygen has been investigated. Reaction of the pseudo‐tetrahedral complex (η2‐triphos)CoCl2 (1) with dioxygen yields after work‐up the mixed phosphane/phosphane oxide ligands triphosO and triphosO2. The novel ligand triphosO2 can be obtained in quantitative yield using catalytic amounts of 1. In order to gain some insight into the catalytic dioxygen activation reaction, experiments with various triphos/Co/Cl species, in different solvents and at several concentrations have been carried out. A mechanism involving two separate reaction pathways is proposed. Complexes of triphosO and triphosO2 with CoCl2, [η2‐(P, P)‐triphosO]CoCl2 (4), and [η2‐(P, O)‐triphosO2]CoCl2 (5), which are present as intermediates in the oxygenation reaction, have been isolated and fully characterized including X‐ray structural analyses.
Cyclic and Bicyclic Poly(phosphane)borane Cations
Authors: Sigl Mareus , Sehier Annette , Schmidbaur Hubert 
Published: July 2007

AbstractThe reactions of (Me2S)BH2Br and (Me2S)BHBr2 with equimolar quantities of 1,2‐bis(diphenylphosphanyl)ethene (1) or ‐benzene (2) lead to cyclic, cationic bis(phosphane)boranes [4[(1)BH2]+ Br−; 6: [(2)BH2]+ Br; 7: [(2)BHBr]+ Br−]. The Br counterions can be exchanged in metathesis reactions (e.g. with AgBF4 to afford 4a). The tritertiary phosphane bis[2‐(diphenylphosphanyl)phenyl]phenyl‐phosphane (3), reacts with (Me2S)BHBr2 to give bicyclic dicationic tris(phosphane)borane 8, [(3)BH]2+ Br−, which can be converted into the bis(hexafluorophosphate) 8a using NH4PF6. All compounds have been characterized by analytical and NMR‐spectroscopic data. The crystal and molecular structures of 5 ‐ 7 have been determined by single‐crystal X‐ray diffraction. The five‐membered rings C2P2B have an envelope conformation and show no sign of electron delocalization. Attempts to deprotonate the BH functions in 5 – 8 have not been successful. Clearly, the two (5 – 7) or three phosphonium centers (8) adjacent to the boron atom are not sufficient to induce an “umpolung” of the BH group
Structure and Reactivity of Sodium Phenoxide ‐ Following the Course of the Kolbe‐Schmitt Reaction
Authors: Kunert Michael , Dinjus Eckhard , Nauck Maria , Sieler Joachim 
Published: July 2007

AbstractSolvent‐free sodium phenoxide (NaOPh) crystallises as a polymer and forms a polymeric chain in the [0 0 1] direction. The low coordination of the sodium atoms, as evident in the crystal structure, is confirmed by the easy coordination of oxoligands (α‐donors). Hence, the four‐membered ring chain of the solvent‐free sodium phenoxide is separated by oxoligands, and forms partial structures as the polymer fragments. Thus, NaOPh crystallises in THF with the formation of an Na6O6 core, consisting of two face‐fused heterocubes, and in N, N, N′, N′‐tetramethyl urea (TMU) with the formation of a Na4O4 heterocubane. The solvent‐free NaOPh‐CO2 complex obtained from the addition of CO2 to a solution of sodium phenoxide is, when exposed to a temperature of 80°C, subject to an irreversible phase transition, as demonstrated by FT‐IR and DTA studies. The complex formed at 80°C is, apparently, another intermediate of the Kolbe‐Schmitt reaction.
P/O Ligand Systems: Facile Synthesis, Structure, and Catalytic Tests of 2′‐Phosphanyl‐1,1′ ‐phenyl‐2‐ols and 2′‐Phosphanyl‐1,1′‐binaphthyl‐2‐ols
Authors: Kadyrov Renat , Heinicke Joachim , Kindermann Markus K. , Heller Detlef , Fischer Christine , Selke Rüdiger , Fischer Axel K. , Jones Peter G. 
Published: July 2007

AbstractA facile synthesis of 2′‐phosphanyl‐1,1′‐biphenyl‐ and 2′‐phosphanyl‐1,1′ ‐binaphthyl‐2‐ols and their silyl ethers has been developed, consisting of electron‐transfer‐catalyzed ring‐opening of dibenzofuran and dinaphthofuran, respectively, subsequent reaction with chlorophosphanes, and work‐up with acetic acid or ClSiMe3. Studies of the molecular and crystal structures reveals the presence of P—H—O bridging bonds in the more basic tBuPhP derivative and a nearly perpendicular arrangement of the aryl planes in the biphenyl derivatives. The barrier to rotation of the aryl planes about the C–C axis was determined by NMR in the case of the P‐asymmetric derivative 3d, using the appearence of diastereoisomers by atropisomerism and P‐asymmetry. Comparative screening tests of the title compounds, phosphanyl phenols and phosphanylnaphthols in homogeneous Rh‐catalyzed reactions demonstrate catalytic activity in hydroformylation reactions and superior properties of the biphenyl‐ and binaphthyl‐2‐ol derivatives in relation to other P–O ligands.
Coordination Chemistry of Pentahalocyclopentadienyls
Authors: Sünkel Karlheinz 
Published: July 2007

AbstractThe coordination chemistry of perhalocyclopentadienyl ligands, first developed in the early 1970's as a part of a research program directed towards the synthesis of oxidation‐resistant fuel additives, has been revived in the last ten years. This renewed interest stems from the discovery that the coordinated cyclopentadienyl ligand allows multiple functionalizations. Thus, the high versatility of this important class of ligands can be broadened even further, which may be important with regard to industrial applications of metallocenes.
Compounds of Germanium and Tin, 22 – Reactions of a Silyene with a Germylene and a Stannylene: Formation of a Digermene with an Unusual Arrangement of the Substituents and of a Stannane
Authors: Schäfer Annemarie , Saak Wolfgang , Weidenbruch Manfred , Marsmann Heinrich , Henkel Gerald 
Published: July 2007

AbstractThe reaction of the diaminosilylene :Si(tBuNCH2CH2NtBu) (5) with the diaminogermylene :Ge(tBuNCH2CH2NtBu) is thought to proceed via a germasilene → silylgermylene rearrangement and dimerisation to furnish the (Z)−1,2‐diamino‐1,2‐disilyldigermene (Z)‐9. The X‐ray structure analysis of (Z)‐9 reveals a long GeGe bond length of 245 pm and a large trans‐bent angle of 42°. Air‐oxidation of (Z)‐9 takes place with retention of configuration at the germanium atoms to provide the corresponding substituted (Z)−2,4‐digerma‐1,3‐dioxetane (Z)‐10. Treatment of 5 with the stannylene :Sn[N(SiMe3)2)2 gives, as a final product, the hydridodisilylstannane 12. The structures of (Z)‐10 and 12 were also determined by X‐ray crystallography.
Betulin binds to melanocortin receptors and antagonizes α‐melanocyte stimulating hormone induced cAMP generation in mouse melanoma cells
Authors: Muceniece Ruta , Saleniece Kristine , Riekstina Una , Krigere Liga , Tirzitis Gunars , Ancans Janis 
Published: July 2007

AbstractBetulin is a principal component of birch bark and is known to possess a broad range of biological activities, including antiinflammatory, antiviral and anticancer actions. The present study was carried out in vitro to clarify the influence of betulin on melanocortin (MC) receptor‐ergic signalling by using COS‐7 cells transfected with corresponding human MC receptor DNA. The results showed that betulin binds to the human melanocortin MC1, three to five receptors with selectivity to the MC1 subtype (Ki value 1.022 ± 0.115 µM). Betulin binds to the MC receptors with the following potency order—MC > MC3 > MC5 > MC4. Betulin itself does not stimulate cAMP generation, however, it slightly antagonizes α‐melanocyte‐stimulating hormone (α‐MSH)‐induced cAMP accumulation in the mouse melanoma cell line B16‐F1. As a water‐insoluble substance, betulin was dissolved in DMSO therefore DMSO competition with the labelled ligand NDP‐MSH for the binding to the MC receptors was tested in the identical experimental set‐up. We found that DMSO competes for binding to all the MC receptor subtypes, at 20% concentration and above. Selectivity for one or another receptor subtype was not observed. We have demonstrated for the first time, the ability of the plant compound betulin to bind to the MC receptors. One may suggest MC receptor MC1 subtype as the essential target for the antimelanoma action of betulin and its structurally close molecules such as betulinic acid. Moreover, we have found a new non‐peptide small molecule MC mimetic, that is betulin. Thus, we report a new chemical motif for the binding to the MC receptors that could be used as a template for the search of more selective MC mimetics. Copyright © 2007 John Wiley & Sons, Ltd.
The Path Ahead for Ionic Liquids
Authors: Joglekar H. G. , Rahman I. , Kulkarni B. D. 
Published: July 2007

AbstractIonic liquids are designer molecules which can efficiently replace the conventional organic solvents used in chemical processes and operations. Although a number of such applications have been reported in the literature for almost a decade, very few have actually been commercialized. This paper details the different applications claimed and examines the issues and barriers which obstruct the rapid commercialization of ionic liquids. It identifies further courses of action required for the assessment and realization of the advantages of ionic liquids.
Adsorption of Pb2+ on Chitosan Cross‐Linked with Triethylene‐Tetramine
Authors: Tang X.‐H. , Zhang X.‐M. , Guo C.‐C. , Zhou A.‐L. 
Published: July 2007

AbstractA novel triethylene‐tetramine cross‐linked chitosan (CCTS) was synthesized via the cross‐linking of triethylene‐tetramine and epichlorohydrin activated chitosan. Its structure was characterized by elemental analysis, infrared spectroscopy and X‐ray diffraction analysis, and the surface topography was determined with ESEM. The results were in agreement with expectations. The capacity of CCTS to adsorb Pb2+ ions from aqueous solutions was examined, and equilibrium and kinetic investigations were undertaken. The adsorption isotherms were fitted well by the Langmuir equation (R > 0.999). The maximum adsorbed amount, at pH 5.5, with an initial concentration of 3 mmol/L (621 ppm), was 378.8 mg/g. The adsorption process could be best described by a second‐order equation (R = 1). This suggests that the rate‐limiting step may be the chemical adsorption (chemisorption) step and not the mass transport. The separation factor used was 0 < RL < 1. Therefore, it can be concluded that CCTS is an effective adsorbent for the collection of Pb2+.
CFD Simulation of Mass Transfer Efficiency and Pressure Drop in a Structured Packed Distillation Column
Authors: Haghshenas Fard M. , Zivdar M. , Rahimi R. , Nasr Esfahani M. , Afacan A. , Nandakumar K. , Chuang K. T. 
Published: July 2007

AbstractThe pressure drop and mass transfer efficiency for two‐phase flow in a structured packed column were simulated using a commercial CFD package, CFX version 10. The distillation of the methanol/isopropanol system was carried out in a 0.073 m diameter column, with an element composed of a ceramic structured packing and 0.053 m in height. The Height Equivalent to Theoretical Plate (HETP) value varied from 0.106–0.146 m. Pressure drop experiments were measured with an air/water system. The pressure drops at the flooding and loading points were ca. 173 and 580 Pa/m of packing, respectively. HETPs and pressure drops calculated from the Computational Fluid Dynamics (CFD) model were compared to their experimental counterparts. The average relative error between CFD predictions and the experimental data for the prediction of dry pressure drop, irrigated pressure drop and mass transfer efficiency are 20.3 %, 23 % and 9.15 %, respectively. In all cases, the CFD predictions show a good agreement with the experimental data, indicating that CFD is a reliable, cost saving and suitable technique for the design and optimization of separation processes.
Capillary Pressure Estimation Using Statistical Pore Size Functions
Authors: Ghazanfari M. H. , Rashtchian D. , Kharrat R. , Vossoughi S. 
Published: July 2007

AbstractCapillary pressure curves, which have been employed for a long period of time by researchers interested in pore size distribution, are commonly obtained from experimental measurements. The dynamic capillary pressure that influences the flow is affected by many factors including the pore size characteristics and pore scale dynamics. Hence, it is important to investigate the variation of the estimated pore size distribution with capillary number. In this study, a glass type micromodel is considered as the porous media sample. A parametric probability density function is proposed to express the pore size distribution of the porous model, which is also measured using an image analysis technique. The capillary pressure saturation mathematical model is developed by integrating the pore size distribution function. Model parameters with a physical significance are estimated by fitting the model to the measured capillary pressure data at different capillary numbers. The results of capillary pressure obtained are well matched to the measured values. The results show that the trends of the extracted pore size distribution curves have similar trends, but they are not exactly the same. Therefore, the dynamic capillary pressure data alone are not sufficient for estimation of the pore size distribution. As a related development, the prediction of the capillary pressure curves based on measured pore size distributions is also presented. The proposed probability distribution function has the flexibility of representing a wide variety of pore size distributions.
3‐D Simulations of an Internal Airlift Loop Reactor using a Steady Two‐Fluid Model
Authors: Huang Q.‐S. , Yang C. , Yu G.‐Z. , Mao Z.‐S. 
Published: July 2007

AbstractThree‐dimensional (3‐D) simulations of an internal airlift loop reactor in a cylindrical reference frame are presented, which are based on a two‐fluid model with a revised k‐ϵ turbulence model for two‐phase bubbly flow. A steady state formulation is used with the purpose of time saving for cases with superficial gas velocity values as high as 0.12 m/s. Special 3‐D treatment of the boundary conditions at the axis is undertaken to allow asymmetric gas‐liquid flow. The simulation results are compared to the experimental data on average gas holdup, average liquid velocity in the riser and the downcomer, and good agreement is observed. The turbulent dispersion in the present two‐fluid model has a strong effect on the gas holdup distribution and wall‐peaking behavior is predicted. The CFD code developed has the potential to be applied as a tool for scaling up loop reactors.