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  • 1
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Crown Thioether Complexes of Cobalt(III): Ligand Structure and Redoxreactivity. Crystal Structure, Electrochemistry, and Kinetics of the Electron Transfer Exchange Reactions of [Co(tacn)(ttcn)] Br3 · 3 H2O (tacn = 1,4,7-Triazacyclonone, ttcn = 1,4,7-Trithiacyclononane)Synthesis, crystal structure and redoxreactivity of [Co(tacn)(ttcn)]Br3 · 3 H2O (tacn = 1,4,7-triazacyclononane, ttcn = 1,4,7-trithiacyclononane) are reported. Average Co—S and Co—N bond distances are 2.247 Å and 1.961 Å, respectively. Cyclic voltammetry revealed two reversible electron transfer waves at +0.01 V vs. NHE ([Co(tacn)(ttcn)]3+/2+) and at -1.15 V vs. NHE ([Co(tacn)(ttcn)]2+/1+) at 25°C, I = 0.1 M. Electron transfer self exchange rate constants, k11, M-1 s-1, have been determined for the couples [Co(tacn)(ttcn)]3+/2+, [Co(ttcn)2]3+/2+, and [Fe(tacn)2]3+/2+ to be 4.2 X 104 (25°C; I = 0,1 M); 1.6 X 105 M-1 s-1 (25°C; I = 0.2 M); 4.6 x 103 M-1s-1 (25°C, I = 0.05) M-1 s-1, respectively. k11 for [Co(ttcn)2]3+/2+ has been determined using 1H NMR line-broadening techniques; for [Co(tacn)(tten)]3+/2+ and [Fe(tacn)2]3+/2+ the kinetics of the cross-reactions ([Ru(NH3)6]2+, respectively) have been measured, and K11 was evaluated using the Marcus-cross-relationship.
    Notes: Synthese, Kristallstruktur und Redoxreaktivität von [Co(tacn)(ttcn)]Br3 · 3 H2O (tacn = 1,4,7-Triazacyclononan; ttcn = 1,4,7-Trithiacyclononan) werden beschrieben. Mittlere Co—S- und Co—N-Bindungsabstände werden zu 2,247 Å bzw. 1,961 Å bestimmt. Das Redoxpotential für [Co(tacn)(ttcn)]3+/2+ bei 25°C (I = 0,1 M) ist + 0,01, während es für das Paar [Co(tacn) (ttcn)]2+/1+ bei -1,15 V gegen NHE mittels der cyclischen Voltammetrie bestimmt wurde. Die Elektronenaustauschgeschwindigkeitskonstante, k11, M-1 s-1, für [Co(tacn)(ttcn)]3+/2+ wurde über die Messung der Kinetik der gekreuzten Redoxreaktionen zwischen [Co(tacn)(ttcn)]3+ und [[Ru(NH3)6]2+ mit Hilfe der Marcus-Gleichung bestimmt: 4,2 X 104 M-1 s-1 (25°C, I = 0,1 M). Für das analoge Komplexpaar [Co(ttcn)2]3+/2+ wurde diese Konstante durch 1H-NMR-Linienverbreiterungsmethoden direkt gemessen: k11 = 1,6 X 105 M-1 s-1 (25°C; I = 0,2 M). Für [Fe(tacn)2]3+/2+ wurde diese Konstante pulsradiolytisch bestimmt: 4,6 X 103 M-1 s-1 (25°C, I = 0,05M).
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Crown Thioether Complexes of Lead (II), Zinc(II), and Cadmium (II). Crystal Structures of [PbL2(ClO4)2] and [ZnL2](ClO4)2 · CH3CN (L = 1,4,7 - Trithiacyclononane)The reaction of 1,4,7-trithiacyclononane (L) with the perchlorate salts of lead(II) and zinc(II) in CH3CN (2:1) affords colorless crystals of [PbL2(ClO4)2] and [ZnL2](ClO4)2 · CH3CN, respectively, The crystal structures have been determined. The PbII centre is coordinated to six sulfur atoms (the average distance Pb—S is 3.076 Å) and two oxygen atoms, one of each ClO4- anion (monodentate ClO4-). A distorted square antiprismatic polyhedron is thus generated. In [ZnL2](ClO4)2 · CH3CN the zinc(II) centre is octahedrally surrounded by six sulphur atoms (average distance Zn—S = 2.494 Å); the ClO4- anions are not coordinated. For[CdL2](ClO4)2 · H2O an analogous structure is proposed.
    Notes: Die Umsetzung von 1,4,7-Trithiacyclononan (L) mit den Perchloratsalzen des Blei(II) und Zink(II) in CH3CN (2:1) führt zu den farblosen Salzen [PbL2(ClO4)2] und [ZnL2](ClO4)2 · CH3CN. Die Kristallstrukturen wurden bestimmt: Das PbII-Ion ist von 6 Thioether-schwefelatomen (mittlerer Abstand Pb—S 3,076 Å) sowie zwei O-Atomen von jeweils einem ClO4-Anion (einzähnig koordiniertes ClO4-) umgeben, wodurch ein verzerrt quadratisch antiprismatisches Koordinationspolyeder am PbII erzeugt wird.Im [ZnL2](ClO4)2 · CH3CN ist das ZnII oktaedrisch von sechs Schwefelatomen umgeben (mittlerer Abstand Zn—S = 2,494 Å); die ClO4--Anionen sind nicht koordiniert. Für [CdL2](ClO4)2 · H2O, das ebenfalls dargestellt wurde, wird eine analoge Struktur vorgeschlagen.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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