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  • Inorganic Chemistry  (9)
  • ASTRONOMY  (2)
  • 1995-1999  (11)
  • 1955-1959
  • 1910-1914
  • 1995  (11)
  • 1
    Publication Date: 2011-08-24
    Description: We obtained the first high-dispersion IUE spectrum, and an additional low-dispersion spectrum of the very young planetary nebula He 3-1357 and its central star SDAO 244567. In 1988, it showed a very strong C IV lambda-1549 P Cygni profile which diminished and has disappeared by 1994, but C IV absorptions are seen in a high-resolution spectrum. The electron density from the C III F(lambda 1907)/F(lambda 1909) emission ratio is log N(sub e) = 4.1/cc. The older IUE data were reprocessed, and emission-line fluxes vary greatly for the period 1988-1994. The high-dispersion data show a rich Fe V and Fe VI absorption spectrum.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 443; 1; p. 245-248
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  • 2
    Publication Date: 2019-07-13
    Description: Low-ionization nuclear emission-line regions (LINERs), which exist in a large fraction of galaxies, may be the least luminous manifestation of quasar activity. As such, they may make possible the study of the active galactic nucleus (AGN) phenomenon in the nearest galaxies. The nature of LINERs has, however, remained controversial because an AGN-like nonstellar continuum source has not been directly observed in them. We report the detection of bright (greater than or approximately = 2 x 10(exp -16) ergs/s/sq cm/A), unresolved (full width at half maximum (FWHM) less than or approximately = 0.1 sec) point sources of UV (approximately 2300 A) emission in the nuclei of nine nearby galaxies. The galaxies were imaged using the Faint Object Camera (FOC) on the Hubble Space Telescope (HST), and seven of them are from a complete sample of 110 nearby galaxies that was observed with HST. Ground-based optical spectroscopy reveals that five of the nuclei are LINERs, three are starburst nuclei, and one is a Seyfert nucleus. The observed UV flux in each of the five LINERs implies an ionizing flux that is sufficient to account to the observed emission lines through photoionization. The detection of a strong UV continuum in the LINERs argues against shock excitation as the source of the observed emission lines, and supports the idea that photoionization excites the lines in at least some objects of this class. We have analyzed ground-based spectra for most of the northern-hemisphere galaxies in the HST sample and find that 26 of them are LINERs, among which only the above five LINERs have a detected nuclear UV source.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 440; 1; p. 91-99
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  • 3
    ISSN: 0009-2940
    Keywords: Manganese ; Cycloheptadienyl ; Alkyne ; [5+2],homo[5+2] Cycloadditions ; Tricyclo[5.3.1.04,10]undeca-2,5-dien-11-yl ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photochemical Reactions of Transition Metal Organyl Complexes with Olefins, 1312. Mitteilung: Lit. . - Photochemically Induced [5+2], homo[5+2] Cycloaddition of 3-Hexyne to Tricarbonyl(η 5-2,4-cycloheptadien-1-yl)manganeseTricarbonyl(η5-2,4-cycloheptadien-1-yl)manganese (1) reacts upon UV irradiation in hexane at 243 K with two equivalents of 3-hexyne (2) in successive [5+2],homo[5+2] cycloadditions to give tricarbonyl(η2:2:1-1,2,3,11-tetraethyltricyclo-[5.3.1.04,10]undeca-2,5-dien-11-yl)manganese (3). Its crystal and molecular structure was determined by an X-ray diffraction analysis, in solution it was studied also by IR and NMR spectroscopy.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 183-185 
    ISSN: 0009-2940
    Keywords: 1,4-Diboranaphthalines ; 2,7-Diboradodeca-1,3,9,11-tetraenes ; Cobalt complexes ; Rhodium complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Complexation of 1,4-Dimethyl-2,3-bis(isopropylidene)-1,4-diboratetraline1,4-Dimethyl-2,3-bis(isopropylidene)-1,4-diboratetraline (2) is obtained from o-dilithiumbenzene and 2,5-dimethyl-3,4-bis(chloromethylboryl)-2,4-hexadiene in 61% yield. Its complexation with cyclopentadienylbis(ethene)cobalt leads to the triple-decker bis(η5-cyclopentadienylcobalt)-μ-η6,η6-1,4-dimethyl-2-isopropenyl-3-isopropyl-1,4-dihydro-1,4-dibora-naphthaline (3) in low yield. However, the reaction of 2 with (C5H5)Rh(C2H4)2 and (C5Me5)Co(C2H4)2 originates complexes of a tricyclic ligand formed from 2 via conrotatoric [2 + 2] cycloaddition of the isopropylidene groups. (η5-Cyclo-pentadienylrhodium)-η6-tricyclo-[6.4.0.03,6]-2,4,4,5,5,7-hexamethyl-2,7-diboradodeca-1,3,9,11-tetraene (4), (η5-pentamethylcyclopentadienylcobalt)-η6-tricyclo-[6.4.0.03,6]-2,4,4,5,5,7-hexamethyl-2,7-diboradodeca-1,3,9,11-tetraene (5) and its related dinuclear complex 6 could be isolated in 29, 10, and 31%, respectively. Their constitutions are derived from spectroscopic data and proven by X-ray structure analysis of 4.
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  • 5
    ISSN: 0009-2940
    Keywords: Tripodal ligands, chiral ; Iron tris(acetonitrile) tripod complexes ; Chiral triphosphanes ; Conformational analysis ; Ligand exchange ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fe(NCMe)2+3 Complexes of Chiral Tripod Ligands Bearing three Different Donor Groups: Dynamics and StructureChiral tripod ligands [tripod = CH3C(CH2PR2)(CH2PR′2)(CH2-PR′′2), 1a-d] with three different donor groups react with Fe(NCMe)6(BF4)2 to yield the complexes tripodFe(NCMe)3(BF4)2 (2a-d). These complexes show an idealized octahedral coordination based on a facial coordination of the tripod ligand. The asymmetry of the chiral tripod ligands a-d induces a differentiation of the remaining coordination sites at iron. The structure and the dynamic behaviour of the compounds 2a, b is elucidated by X-ray structural analyses and 2D-NMR techniques.
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  • 6
    ISSN: 0009-2940
    Keywords: Amines, bis(dichlorosilyl) ; bis(dichlorosilyl)methyl- ; Gas-phase electron diffraction ; Calculations, ab initio ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The gas-phase molecular structures of bis(dichlorosilyl)-amine, (HSiCl22NH, and bis(dichlorosilyl)methylamine, (SiHCl2)2NMe, have been investigated by electron diffraction and ab initio calculations on a MP2/6-31G* level. Because the latter suggest the presence of a mixture of two conformers for each molecule, attempts were made to fit the electron diffraction data in each case by two different models, one assuming the presence of only one conformation, and another allowing for two different conformers. The principal parameters (ra) from electron diffraction for (HSiCl2)2NH are (the appropriate ab initio calculated values are given in brackets []): r(Si-N) 171.9(2) [172.7], r(Si-Cl) 204.1(1)[204.5] pm; Si-N-Si 126.5(8) [127.4] N-Si-Cl 107.3(5) [110.8] and Cl-Si-Cl 106.5(3) [107.5]°. For (SiHCl2)2NMe: r(Si-N) 171.1(3) [171.5], r(Si-Cl) 204.0(9) [205.2], r(N-C) 149.7(10) [148.3] pm; Si-N-Si 124.9(13) [123.4], N-Si-Cl 109.7(5) [110.7] and Cl-Si-Cl 107.1(3) [107.2]° [110.8] and Cl-Si-Cl 106.5(3) [107.5]°. For (SiHCl2)2NMe: r(Si-N) 171.1(3) [171.5], r(Si-Cl) 204.0(9) [205.2], r(N-C) 149.7(10) [148.3] pm; Si-N-Si 124.9(13) [123.4], N-Si-Cl 109.7(5) [110.7] and Cl-Si-Cl 107.1(3) [107.2]°. For (HSiCl2)2NH three different conformers were found to fit the experimental data with the single-conformation model. In two of the conformers, the dichlorosilyl groups are twisted by Θ1 = 146.0(10)/Θ2 = 155.2(20)° and Θ1= 101.1(49)/Θ2 = 196.8(12)°; respectively counterclockwise from the positions in which the Si-H bonds eclipse the N-H bond. Both of these lead to nearly ideally staggered conformations of the two SiHCl2 groups when viewed along the Si-Si axis. In contrast, the third conformation is nearly eclipsed, with torsion angles Θ1 = 131.4(15)/Θ2 = 80.4(26)°. Planarity of the Si2NH group was assumed as suggested by ab initio calculation. For (HSiCl2)2NMe the experimental data could be suitably fitted by two conformers, in which the dichlorosilyl groups are twisted by Θ1= 161.8(13)/Θ2 = 63.1(23)° and Θ1 = 156.1(9)/ Θ2 = 177.1(15)° from the positions in which the Si-H bonls eclipse the N-C bond. The first of these structures has an eclipsed Si(NSi)Cl conformation and an Si…Cl nonbonded distance close to distance clse to the sum of the appropriate van der waals radii. MP2/6-31G* calculations support the GED bond lengths and bond angles of both molecules, but indicate different conformations for the most stable equilibrium geometries: the computed twists are Θ1 = 180/Θ2 = 180° and Θ1 = 177.0/ Θ2 = 183.0° for (HSiCl2)2NH and (HSiCl2)2NMe, respectively. Rotation about the Si - N bonds is a very facile process, cf. the computed [MP2/6-31G*//MP2/6-31G* + ZPE(SCF/6-31G*)] rotational barrier of 2.9 kJ. mol-1 for (HSiCl2)2NH.
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  • 7
    ISSN: 0009-2940
    Keywords: Tripod ligand synthesis ; Tripod nickel chloro complexes ; Tripod iron tris(acetonitrile) complexes ; Tripod cobalt acetate complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Complex Chemistry of Functionalised Tripod Ligands RC(CH2PPh2)3Malonic ester 1 is alkylated and converted into the triols RC(CH2OH)3 (5). These are easily converted into the corresponding functionalised tripodal ligands RC(CH2PPh2)3 (7) with R = Bzl (a), n-C12H25 (b), (CH3)2CH(CH2)2 (c). Crystals suitable for X-ray crystallography have been obtained of the ligand 7a. In addition, the tripod ligands 7a and 7c have been further characterized by the syntheses and X-ray analyses of the nickel complex [(7a)NiCl] (8a), the iron complex [(7c)Fe(NCCH3)3](BF4)2 [9 · (BF4)2], and the cobalt complex [(7c)Co{O(O)CCH3}](BPh4) (10 · BF4).
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  • 8
    ISSN: 0044-2313
    Keywords: Gallium iridium boride ; crystal structure ; preparation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Ga8Ir4B - a Gallium Iridium Boride with isolated, nearly square planar Ir4B Groups in a Structure derived from the CaF2 TypeThe new compound Ga8Ir4B (tetragonal, I41/acd, a = 853.69(2) pm, c = 2 105.69(6) pm, Z = 8, 614 reflections, 31 parameters, R = 0.034) was prepared by reaction of the elements at 1 100°C. The structure is derived from the CaF2 type. It contains isolated Ir4B groups with boron in an unusual, nearly square planar coordination.
    Notes: Die neue Verbindung Ga8Ir4B (tetragonal, I41/acd, a = 853,69(2) pm, c = 2105,69(6) pm, Z = 8, 614 Reflexe, 31 Parameter, R = 0,034) wurde durch Reaktion der Elemente bei 1 100°C dargestellt. Die Struktur läßt sich vom CaF2-Typ ableiten. Sie enthält isolierte Ir4B-Gruppen mit Bor in einer ungewöhnlichen, nahezu quadratisch planaren Koordination.
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  • 9
    ISSN: 0044-2313
    Keywords: Cyclometallaphosphazenes, Platin, Iron ; crystal structures ; IR, Raman, NMR, mass spectra ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Chemistry of Polyfunctional Molecules. 118. Syntheses and Crystal Structures of Bicyclic Metallaphosphazenes with Four and Six Membered RingsAnhydrous MCl2 (M = Pt, Fe) react with LiN(PPh2)2 (1) in the molar ratio of 1:2 in boiling toluene within 25 hours under partially oxidative scrambling of the PNP chain in 1 yielding the bicyclic metallaphosphazenes 5 a, b. While compound 5 a can be isolated in substance, the intermediate 5 b proves to be highly reactive but can be stabilized in the presence of CO, forming the 18-valence-electron coordination compound as an isomeric trans(6 a)/cis(6 b) mixture in the molar ratio of 99:1. Also treatment of anhydrous PtCl4 with four equivalents of 1 in boiling toluene during 60 hours yields 5 a. Alkylation of 5 a with CH3I leads to the formation of the ionic species [Pt2+{Ph2P—N(CH3)—PPh2}(Ph2P—N = PPh2 = N—PPh2-)]I- (9). The X-ray crystal structures of 5 a × 1 CH2Cl2 and 6 a reveal, that the metal centres have a planar P-coordination polyhedron in the solid state. In the complex 9 × 2,5 CH2Cl2 however the torsion angle between the P—Pt—P planes of the four and six membered rings shows to be 15°. The six membered metallacycles in 5 a × 1 CH2Cl2, 6 a and 9 × 2,5 CH2Cl2 differ in their geometrical arrangement. All the new compounds have also been characterized by their 1H, 31P{1H}, 13C{1H} NMR, IR, Raman and mass spectra.
    Notes: Wasserfreies MCl2 (M = Pt, Fe) reagiert mit LiN(PPh2)2 (1) im Molverhältnis von 1:2 in siedendem Toluol während 25 Stunden unter teilweiser oxidativer Spaltung und Umgruppierung der PNP-Kette von 1 zu den bicyclischen Metallaphosphazenen 5 a, b. Während die Verbindung 5 a in Substanz isoliert werden kann, ist 5 b ein sehr reaktives Intermediat, das lediglich in Gegenwart von CO die 18-Elektronen-Verbindung bildet, die als trans(6 a)-/cis(6 b)-Isomerengemisch im Molverhältnis von etwa 99:1 anfällt. Die Umsetzung von wasserfreiem PtCl4 mit 1 im Molverhältnis 1:4 liefert nach 60-stündiger Reaktionszeit ebenfalls 5 a. Alkylierung von 5 a mit CH3l führt zum ionischen Komplex [Pt2+{Ph2P—N(CH3)—PPh2}(Ph2P—N = PPh2 = N—PPh2-)]I- (9). Kristallstrukturanalysen von 5 a × 1 CH2Cl2 und 6 a zeigen, daß die Metalle in ihnen quadratisch-planar durch die Phosphoratome koordiniert sind. Dagegen sind die (P—Pt—P)-Ebenen der Vier- und Sechsringe von 9 × 2,5 CH2Cl2 am metallischen Zentrum um 15° gegeneinander verdrillt. In 5 a × 1 CH2Cl2, 6 a und 9 × 2,5 CH2Cl2 besitzen die 6-gliedrigen Metallaphosphazenringe unterschiedliche Konformationen. Alle Verbindungen wurden außerdem durch 1H-, 31P{1H}-, 13C{1H}-NMR- sowie durch IR-, Raman- und Massenspektren charakterisiert.
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  • 10
    ISSN: 0044-2313
    Keywords: Ruthenium(II) Complexes ; Bis(diphenylphosphino)amine ; IR, Raman, NMR, UV/VIS spectra ; NMR Simulation ; Spin-Spin-Coupling-Constant-Assignments ; Crystal Structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Chemistry of Polyfunctional Molecules. 116 Hydrido-, Deuterido-, Thiolato-, and Chlororuthenium(II) Complexes of Bis(diphenylphosphino)amineBis(diphenylphosphino)amine, [(C6H5)2P]2NH (dppa, 1), reacts with [Ru(cod)(cot)] (cod = η-1,5-cyclooctadiene, cot = η-1,3,5-cyclooctatriene) (2) in a molar ratio of 2 : 1 both in a hydrogen or deuterium atmosphere at room temperature to yield cis-[Ru(H)2(dppa)2] (3) and cis-[Ru(D)2(dppa)2] (3 a), respectively. The dihydride complex 3 is very sensitive towards halogenated solvents: dissolution of 3 in CHCl3 or CH2Cl2 produces the monohydride compound trans-[RuCl(H)(dppa)2] (4). Treatment of 3 with a threefold excess of tert-butyl mercaptane, Me3CSH, at room temperature results in the formation of cis-[Ru(H)(SCMe3)(dppa)2] (5). Trans-[RuCl2(dppa)2] (7) can be synthesized by the interaction of [RuCl2(PPh3)3] (6) with one or two equivalents of 1 in CH2Cl2 solution. The NMR spectra of 3, 3 a, 4, 5 and 7 are discussed with respect to molecular stereochemistry and hydrogen-halogen exchange under simultaneous cis-trans rearrangement. In addition to 1H, 2H, 31P{1H}, and 31P NMR, the structures of the different complexes were also derived from 1R, Raman, and mass spectra. The NMR spectra simulation of 3 permits detailed assignments of spin-spin coupling constants. Crystals of cis-[Ru(H)(SCMe3)(dppa)2] (5) are monoclinic, space group P21/c, with a = 1 179.9(3), b = 2 228.0(4), c = 1 854.8(6) pm, β = 96.23(2)°, Z = 4, and Rw = 0.062. The structural analysis shows that ruthenium is coordinated by two bidentate organophosphine ligands and by one tert-butyl thiolate molecule. The metal bound hydrogen atom was not located. However, in agreement with 1H NMR, its position is trans to a phosphorus nucleus.
    Notes: Bis(diphenylphosphino)amin, [(C6H5)2P]2NH (dppa, 1) reagiert mit [Ru(cod)(cot)] (cod = η-1,5-Cyclooctadien, cot = η-1,3,5-Cyclooctatrien) (2) im Molverhältnis 2 : 1 in Toluol bei Raumtemperatur sowohl in einer Wasserstoff- als auch einer Deuteriumatmosphäre zu cis-[Ru(H)2(dppa)2] (3) und cis-[Ru(D)2(dppa)2] (3 a). In CHCl3 oder CH2Cl2 entsteht aus 3 die Monohydrido-chloro-Verbindung trans-[RuCl(H) · (dppa)2] (4). Mit überschüssigem tert-Butylmercaptan, Me3CSH, liefert 3 in THF lediglich cis-[Ru(H)(SCMe3)(dppa)2] (5). Die Dichloroverbindung trans-[RuCl2(dppa)2] (7) ist durch Umsetzung von [RuCl2(PPh3)3] (6) mit einem oder zwei Äquivalenten 1 in CH2Cl2 zugänglich. Die NMR-Spektren von 3, 3 a, 4, 5 und 7 werden in bezug auf Molekülsymmetrien und Wasserstoff-Halogen-Austausch unter gleichzeitiger cis-trans-Umlagerung diskutiert. Neben 1H-, 2H-, 31P{1H}- und 31P-NMR-Spektren werden alle Verbindungen auch durch IR-, teilweise Raman- und Massen-Spektren charakterisiert. Die NMR-Spektren-Simulation von 3 ermöglicht genaue Zuordnungen von Spin-Spin-Kopplungskonstanten. Kristalle von cis-[Ru(H) · (SCMe3)(dppa)2] sind monoklin und kristallisieren in der Raumgruppe P21/c mit den Zellparametern a = 1179,9(3), b = 2 228,0(4), c = 1 854,8(6) pm, β = 96,23(2)°, Z = 4 und Rw = 0,062. Die Röntgenstrukturanalyse zeigt, daß Ruthenium von zwei chelatisierend wirkenden dppa-Liganden und dem Schwefel eines tert-Butylthiolatanions koordiniert ist. Das am Metall gebundene Wasserstoffatom konnte nicht exakt lokalisiert werden, jedoch ist es, in Übereinstimmung mit 1H-NMR-Daten, trans-ständig zu einem P-Atom.
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