Synthesis of Binuclear Bismacrocyclic Iron(￥±) Complex by the Aerobic Oxidation of Iron(￥±) Complex of 1,4,8,11-Tetraazacyclotetradecane

摘要

The aerobic oxidation of the Fe(ケ) 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(ゲ) species [Fe(cyclam)(CH3CN)2](ClO4)3. The Fe(ゲ) cyclam complex is further oxidized in the air in the presence of a trace of water to produce the deep green binuclear bismacrocyclic Fe(ケ) complex [Fe2(C20H36N8)(CH3CN)4](ClO4)4· 2CH3CN. The Fe(ケ) 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 with a= 13.099 (1) ∈, b= 10.930 (1) ∈, c= 17.859 (1) ∈, モ= 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 > 4ヲ (F) measured with Mo Kメ radiation on a CAD-4 diffractometer. The two macrocyclic units are coupled through the bridgehead carbons of モ -diimitie moieties by a double bond. The double bonds in each macrocycle unit are localized. The average bond distances of Fe(ケ)-Nimine, Fe(ケ )-Namine, and Fe(ケ)-NMeCN are 1.890 (5), 2.001 (5), and 1.925 (6) ∈, respectively. The complex is diamagnetic, containing two low spin Fe(ケ) ions in the molecule. The complex shows extremely intense charge transfer band in the near infrared at 868 nm with ュ= 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 ロCO value (2010 cm-1) indicates the ヰ-accepting property of the present bismacrocyclic ligand.