Mankad Neal P, Antholine William E, Szilagyi Robert K, Peters Jonas C
Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
J Am Chem Soc. 2009 Mar 25;131(11):3878-80. doi: 10.1021/ja809834k.
A three-coordinate Cu-NR(2) system (R = p-tolyl) supported by the anionic bis(phosphino)borate ligand Ph(2)B(CH(2)P(t)Bu(2))(2) has been isolated and structurally characterized in both its anionic Cu(I) and neutral (formally) Cu(II) oxidation states. A large rate constant for the self-exchange electron-transfer reaction (k(S) >or= 10(7) M(-1) s(-1)) makes this system a functional model for the type-1 active sites in blue copper proteins. Multiedge X-ray absorption spectroscopy, multifrequency electron paramagnetic resonance, and density functional theory analyses collectively indicate that the oxidized form is best regarded as a Cu(I)-aminyl radical complex rather than a Cu(II)-amido species, with about 70% localization of the unpaired electron on the NR(2) unit. Hydrogen-atom transfer and C-C coupling reactions are presented as examples of chemical reactivity manifested by this unusual electronic structure.
一种由阴离子双（膦基）硼酸酯配体[Ph₂B(CH₂P(t)Bu₂)₂]⁻支撑的三配位Cu-NR₂体系（R = 对甲苯基）已被分离出来，并对其阴离子Cu(I)和中性（形式上的）Cu(II)氧化态进行了结构表征。自交换电子转移反应的大速率常数（k(S)≥10⁷ M⁻¹ s⁻¹）使该体系成为蓝铜蛋白中1型活性位点的功能模型。多边缘X射线吸收光谱、多频电子顺磁共振和密度泛函理论分析共同表明，氧化形式最好被视为Cu(I)-氨基自由基配合物，而不是Cu(II)-酰胺物种，未成对电子约70%定域在NR₂单元上。氢原子转移和C-C偶联反应作为这种不寻常电子结构表现出的化学反应性的例子被呈现出来。
