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  • 1
    ISSN: 0044-2313
    Keywords: Phosphorane iminato complex of tantalum ; synthesis ; IR spectrum ; crystal structure ; ab initio calculation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Tetrakis(triphenylphosphane-iminato)tantalonium hexachlorotantalate, [Ta(NPPh3)4]TaCl6. Synthesis, IR Spectrum, Crystal Structure, and ab initio Calculations of the [Ta(NPH3)4]+ IonThe title compound has been prepared by the reaction of tantalum pentachloride with Me3SiNPPh3 in acetonitrile, forming colourless moisture sensitive crystals, which were characterized by IR spectroscopy and by an X-ray structure determination (Space group P1, Z = 4, 6479 observed unique reflections, R = 0.053. Lattice dimensions at 20°C: a = 1268.4(3), b = 2361.0(6), c = 2400.0(6) pm, α = 85.81(2)°, β = 87.47(3)°, γ = 87.27(3)°). The compound consists of two symmetry-independent cations [Ta(NPPh3)4]+ and anions TaCl6-, respectively. In the cations the tantalum atoms are surrounded in a distorted tetrahedral fashion by the four nitrogen atoms of the phosphane-iminato ligands. The TaN and PN bond lengths in both individuals correspond well with double bonds. According to twisting phenomena of the phenyl rings the TaNP bond angles are different in the two cation species. The investigation is supplemented by ab initio calculations of the [Ta(NPH3)4]+ ion.
    Notes: Die Titelverbindung entsteht aus Tantalpentachlorid und Me3SiNPPh3 in Acetonitril in Form farbloser, feuchtigkeitsempfindlicher Kristalle, die durch das IR-Spektrum und eine röntgenographische Strukturanalyse charakterisiert werden (Raumgruppe P1, Z = 4, 6479 beobachtete unabhängige Reflexe, R = 5,3%. Gitterkonstanten bei 20°C: a = 1268,4(3); b = 2361,0(6); c = 2400,0(6) pm, α = 85,81(2)°; β = 87,47(3)°; γ = 87,27(3)°). Die Verbindung besteht aus je zwei symmetrieunabhängigen Kationen [Ta(NPPh3)4]+ und Anionen TaCl6-. In den Kationen sind die Tantalatome verzerrt tetraedrisch von den N-Atomen der Triphenylphosphaniminatoliganden umgeben. Die TaN- und die PN-Abstände entsprechen in beiden Individuen recht gut Doppelbindungen. Als Folge von Verdrillungseffekten der Phenylringe unterscheiden sich die TaNP-Bindungswinkel in den beiden Kationen erheblich. Die Untersuchungen werden durch Ab-initio-Rechnungen am [Ta(NPH3)4]+-Ion ergänzt.
    Additional Material: 4 Ill.
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  • 2
    ISSN: 0044-2313
    Keywords: Phosphorane iminato complex of niobium ; synthesis ; IR spectrum ; crystal structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Bis(triphenylphosphorane-iminato)niobium Trichloride, [NbCl3(NPPh3)2], a Complex with Coordination Number Five at the Niobium AtomThe title compound has been prepared from niobium pentachloride with Me3SiNPPh3 in acetonitrile solution, forming colourless, moisture sensitive crystals. They were characterized by IR spectroscopy and by an X-ray structure determination. [NbCl3(NPPh3)2] crystallizes monoclinically in the space group Cc with four formula units per unit cell, 3682 observed, unique reflections, R = 0.042%. Lattice dimensions at 20°C: a = 1025.1(2); b = 1870.6(6); c = 1832.5(5) pm, β = 91.83(2)°. The niobium atom of the complex is coordinated in a distorted trigonal bipyramidal fashion, while the nitrogen atoms of the two phosphorane iminato ligands are in equatorial position along with one chlorine atom. NbN and PN distances accord with double bonds; with a mean value of 242.0 pm the Nb—Cl distances are remarkably long.
    Notes: Die Titelverbindung entsteht in Form farbloser, feuchtigkeitsempfindlicher Kristalle bei der Reaktion von Niobpentachlorid mit Me3SiNPPh3 in Acetonitrillösung. Sie wird durch das IR-Spektrum und eine röntgenographische Strukturanalyse charakterisiert. [NbCl3(NPPh3)2] kristallisiert monoklin in der Raumgruppe Cc mit vier Formeleinheiten pro Elementarzelle, 3682 beobachtete unabhängige Reflexe, R = 4,2%. Gitterabmessungen bei 20°C: a = 1025,1(2); b = 1870,6(6); c = 1832,5(5) pm, β = 91,83(2)°. In dem Komplex ist das Niobatom verzerrt trigonal-bipyramidal koordiniert, wobei die N-Atome der beiden Phosphaniminatoliganden zusammen mit einem Chloratom äquatorial angeordnet sind. NbN- und PN-Abstände entsprechen Doppelbindungen; die Nb—Cl-Abstände sind mit dem Mittelwert von 242,0 pm auffällig lang.
    Additional Material: 2 Ill.
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