Copper(I) Nitro Complex with an Anionic [HB(3,5-Me2Pz)3]− Ligand: A Synthetic Model for the Copper Nitrite Reductase Active Site
收藏资源简介：
The new copper(I) nitro complex [(Ph3P)2N][Cu(HB(3,5-Me2Pz)3)(NO2)] (2), containing the anionic hydrotris(3,5-dimethylpyrazolyl)borate ligand, was synthesized, and its structural features were probed using X-ray crystallography. Complex 2 was found to cocrystallize with a water molecule, and X-ray crystallographic analysis showed that the resulting molecule had the structure [(Ph3P)2N][Cu(HB(3,5-Me2Pz)3)(NO2)]·H2O (3), containing a water hydrogen bonded to an oxygen of the nitrite moiety. This complex represents the first example in the solid state of an analogue of the nitrous acid intermediate (CuNO2H). A comparison of the nitrite reduction reactivity of the electron-rich ligand containing the CuNO2 complex 2 with that of the known neutral ligand containing the CuNO2 complex [Cu(HC(3,5-Me2Pz)3)(NO2)] (1) shows that reactivity is significantly influenced by the electron density around the copper and nitrite centers. The detailed mechanisms of nitrite reduction reactions of 1 and 2 with acetic acid were explored by using density functional theory calculations. Overall, the results of this effort show that synthetic models, based on neutral HC(3,5-Me2Pz)3 and anionic [HB(3,5-Me2Pz)3]− ligands, mimic the electronic influence of (His)3 ligands in the environment of the type II copper center of copper nitrite reductases (Cu-NIRs).
本研究成功合成了一种新型一价铜亚硝酸根配合物[(Ph₃P)₂N][Cu(HB(3,5-Me₂Pz)₃)(NO₂)]（化合物2），其配位使用了阴离子型氢三(3,5-二甲基吡唑基)硼酸根配体（hydrotris(3,5-dimethylpyrazolyl)borate ligand）；通过X射线晶体学（X-ray crystallography）对其结构特征进行了表征。研究发现化合物2可与1分子水共结晶，X射线晶体学分析表明，所得共晶产物的结构为[(Ph₃P)₂N][Cu(HB(3,5-Me₂Pz)₃)(NO₂)]·H₂O（化合物3），其中水分子的氢原子与亚硝酸根基团的一个氧原子形成氢键。该配合物是固态环境中首例亚硝酸中间体（CuNO₂H）的类似物。将搭载富电子配体的CuNO₂配合物2与已知的搭载中性配体的CuNO₂配合物[Cu(HC(3,5-Me₂Pz)₃)(NO₂)]（化合物1）的亚硝酸还原活性进行对比，结果表明，铜与亚硝酸根中心周围的电子密度会显著调控其反应活性。本研究借助密度泛函理论（Density Functional Theory）计算，对化合物1与化合物2分别与乙酸发生亚硝酸还原反应的详细机理进行了探究。综上，本研究结果显示，以中性HC(3,5-Me₂Pz)₃配体与阴离子型[HB(3,5-Me₂Pz)₃]⁻配体构建的合成模型，可模拟亚硝酸还原铜酶（copper nitrite reductases, Cu-NIRs）II型铜中心环境中三(组氨酸)配体（(His)₃ ligands）的电子调控效应。
