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1994 (1)
1Author    Dieter Sellmann+, Helge Friedrich, Falk Knoch, Matthias MollRequires cookie*
 Title    Übergangsmetallkomplexe mit Schwefelliganden, C*. Unerwartet einfache Bildung von Diazen-Komplexen und ein neuer Typ von Diastereomerie: [/#-N2H2{Fe(PPr3)('S4')}2] und analoge Komplexe mit [FeS]-Zentren. ( 'S /2-= l,2-Bis(2-mercaptophenylthio)ethan(2-)) Transition Metal Complexes with Sulfur Ligands, C*. Unexpectedly Facile Formation of Diazene Complexes and a New Type of Diastereomerism: [a-N2H2{Fe(PPr3)('S4')}2] and Analogous Complexes with [FeS]-Centers. ('S4'2~ = l,2-Bis(2-mercaptophenylthio)ethane(2-))  
 Abstract    Single pot reactions of FeCl2-4H20 with the tetradentate thioether-thiol 'S4-H 2' = 1,2-bis(2-mercaptophenylthio)ethane, phosphines such as PEt3, PPr3 or PBu3, and a ca. 40-fold excess of N2H4-H20 yield, in the presence of air, diazene complexes of the general formula [M-N2H2{Fe(PR3)('S4')}2]. In contrast to previous syntheses of diazene complexes, the yields can excel 80%, and the syntheses can be carried out on a 10 g scale. [M-N2H2{Fe(PPr3)('S4')}2], 1 and [M-N2H2{Fe(PEt3)('buS4')}2], 2 were characterized by X-ray structure analysis. 2 contains 'buS4'2-= l,2-bis(3,5-ditertiarybutyl-2-mercaptophenylthio)-ethane(2-), which is the tertiary-butyl derivative of 'S4'2-. 1 and 2 contain fram-HN=NH which bridges enantiomeric [Fe(PPr3)('S4')] or [Fe(PEt3)('buS4')] fragments. HN=NH is stabilized by 4c -6 e~-jr bonds, strong tricentric N -H — (S)2 bridges, and steric shielding. NMR studies show that centrosymmetric 1 isomerizes in solution at temperatures around 0 °C in order to give a diastereomerie diazene complex which is also centrosymmetric. The diastereomerism is traced back to bridging the chiral [Fe(PPr3)('S4')] fragments by frara-HN=NH in a differ­ ent way. The two different bridging modes are verified by X-ray structure analyses of analo­ gous ruthenium complexes. Because this new type of diastereomerism is basically caused by a different position only of the N -H — (S)2 bridges, it is termed hydrogen bridge diastereo­ merism. A mechanism for the isomerization is suggested. 1 exhibits three anodic waves in the cyclovoltammogram. The second wave indicates formation of the dication [1]2+, which is a redox isomer of the diprotonated (and as yet hypothetical) dinitrogen complex [a-N2{Fe(PPr3)('S4')}2]. The significance of [1]2+ and of its Lewis basic thiolate donors with respect to electrochemical reduction of molecular dinitrogen under mild conditions is dis­ cussed. 
  Reference    (Z. Naturforsch. 49b, 76—88 [1994]; eingegangen am 9. Juli 1993) 
  Published    1994 
  Keywords    Diazene, Iron Sulfur Complexes, Synthesis, X-Ray 
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 TEI-XML for    default:Reihe_B/49/ZNB-1994-49b-0076.pdf 
 Identifier    ZNB-1994-49b-0076 
 Volume    49