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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 14, Number 4
BKCSDE 14(4)
April 20, 1993 

Synthesis of Binuclear Bismacrocyclic Iron(Ⅱ) Complex by the Aerobic Oxidation of Iron(Ⅱ) Complex of 1,4,8,11-Tetraazacyclotetradecane
Myunghyun Paik Suh*, Gee-Yeon Kong, Il-Soon Kim
The aerobic oxidation of the Fe(Ⅱ) complex of 1,4,8,11-tetraazacyclotetradecane, [Fe(cyclam)(CH3CN)2](ClO4)2, in MeCN in the presence of a few drops of HClO4 leads to low spin Fe(Ⅲ) species [Fe(cyclam)(CH3CN)2](ClO4)3. The Fe(Ⅲ) cyclam complex is further oxidized in the air in the presence of a trace of water to produce the deep green binuclear bismacrocyclic Fe(Ⅱ) complex [Fe2(C20H36N8)(CH3CN)4](ClO4)4· 2CH3CN. The Fe(Ⅱ) ions of the complex are six-coordinated and the bismacrocyclic ligand is extensively unsaturated. [Fe2(C20H36N8)(CH3CN)4](ClO4)4·2CH3CN crystallizes in the monoclinic space group P21/n with a= 13.099 (1) Å, b= 10.930 (1) Å, c= 17.859 (1) Å, β= 95.315 (7)。, and Z= 2. The structure was solved by heavy atom methods and refined anisotropically to R values of R= 0.0633 and Rw= 0.0702 for 1819 observed reflections with F > 4σ (F) measured with Mo Kα radiation on a CAD-4 diffractometer. The two macrocyclic units are coupled through the bridgehead carbons of β -diimitie moieties by a double bond. The double bonds in each macrocycle unit are localized. The average bond distances of Fe(Ⅱ)-Nimine, Fe(Ⅱ )-Namine, and Fe(Ⅱ)-NMeCN are 1.890 (5), 2.001 (5), and 1.925 (6) Å, respectively. The complex is diamagnetic, containing two low spin Fe(Ⅱ) ions in the molecule. The complex shows extremely intense charge transfer band in the near infrared at 868 nm with ε= 25,000 M-1cm-1. The complex shows a one-electron oxidation wave at +0.83 volts and two one-electron reduction waves at -0.43 and-0.72 volts vs. Ag/AgCl reference electrode. The complex reacts with carbon monoxide in MeNO2 to form carbonyl adducts, whose νCO value (2010 cm-1) indicates the π-accepting property of the present bismacrocyclic ligand.
439 - 444
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