Oxidation of an o-Iminobenzosemiquinone Radical Ligand by Molecular Bromine: Structural, Spectroscopic, and Reactivity Studies of a Copper(II) o-Iminobenzoquinone Complex

详细信息    查看全文

• 作者：Chandan Mukherjee ; Thomas Weyhermü ; ller ; Eberhard Bothe ; Phalguni Chaudhuri
• 刊名：Inorganic Chemistry
• 出版年：2008
• 出版时间：April 7, 2008
• 年：2008
• 卷：47
• 期：7
• 页码：2740 - 2746
• 全文大小：1129K
• 年卷期：v.47,no.7(April 7, 2008)
• ISSN：1520-510X

文摘

The bis(o-iminobenzosemiquinonato)copper(II) complex 1, containing the radical form [L^•_SQ]¹⁻ arising from the aerial oxidation of the noninnocent ligand 2-anilino-4,6-di-tert-butylphenol, H₂L, is readily oxidized by molecular bromine to a bis(o-iminobenzoquinone)copper(II) complex, 2. Thus, a ligand-based oxidative addition is reported for complex 1 containing an electron-rich Cu^II d⁹ metal ion. The crystal structure of the synthesized hexacoordinated complex [Cu^II(L_BQ)₂Br₂] (2) has been determined by X-ray crystallography at 100 K. Variable-temperature (2−290 K) magnetic susceptibility measurements and an X-band electron paramagnetic resonance spectrum establish the spin state to be S_t = ¹/₂ because of localized spin moments mainly in the (d_x²–y²)¹ orbital of a Cu^II d⁹ ion, indicating clearly the presence of a neutral iminobenzoquinone form, [L_BQ]⁰, of the ligand in 2, as is found also in the X-ray structure. Electrochemical measurements (cyclic voltammograms and coulometry) indicate two successive one-electron reductions of the ligand. The reactivity of complex 2 as an oxidizing agent toward ethanol and triethylamine has been investigated.