Cammi Roberto, Gennari Marcello, Giannetto Marco, Lanfranchi Maurizio, Marchio Luciano, Mori Giovanni, Paiola Cristiano, Pellinghelli Maria Angela
Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica, Chimica Fisica, Parco area delle Scienze 17a, 43100 Parma, Italy.
Inorg Chem. 2005 Jun 13;44(12):4333-45. doi: 10.1021/ic048221j.
Dinuclear Cu(I) complexes with bifunctionalized homoscorpionate ligands, hydrotris(thioxotriazolyl)borato [Li(Tr(Me,o)(-)(Py)) (1) and Li(Tr(Mes,Me)) (2)], and the heteroscorpionate ligand hydro[bis(thioxotriazolyl)-3-(2-pyridyl)pyrazolyl]borato [K(Br(Mes)pz(o)(-)(Py))] (3) were synthesized and crystallographically characterized. The complexes Cu(Tr(Mes,Me)) (4) and Cu(Tr(Me,o)(-)(Py)) (5) exhibit a similar coordination geometry where every metal is surrounded by three thioxo groups in a trigonal arrangement. The presence of a [B-H...Cu] three-center-two-electron interaction in both compounds causes the overall coordination to become tetrahedrally distorted (S(3)H coordination for each metal). The complex Cu(Br(Mes)pz(o)(-)(Py)) (6) presents a trigonal geometry in which the metals interact with two thioxo groups and a bridging pyrazolyl nitrogen atom. A weak contact with a pyridine nitrogen atom completes the coordination of the metals (S(2)N,N' coordination for each metal). Cu(Tr(Mes,Me)), Cu(Tr(Me,o)(-)(Py)), and Cu(Br(Mes)pz(o)(-)(Py)) exhibit fluxional behavior in solution as evidenced by variable-temperature NMR spectroscopy, and for 5 and 6 two species in equilibrium [in the ratio 2/1 for 5 (CDCl(3)) and 3/2 for 6 (CD(2)Cl(2))] are distinguishable in the (1)H NMR spectra at 270 K. 2D-NOESY spectra recorded at 270 K assisted in the attribution of solution molecular geometries for each isomer of 5 and 6. The free energy of activation (DeltaG()(Tc)) was determined for both equilibria from the evaluation of the coalescence temperature. DFT calculations were performed to describe plausible molecular geometry for the minor isomer of 5 and 6 and to propose a possible mechanism of interconversion between major and minor isomers. Cyclic voltammograms were recorded in CH(2)Cl(2) (3 and 6) or CH(2)Cl(2)/CH(3)CN (1/1, v/v) (2, 4, and 5) solutions using 0.1 M TBAHFP or TBAOTf as supporting electrolytes. Cu(Tr(Mes,Me)), Cu(Tr(Me,o)(-)(Py)), and Cu(Br(Mes)pz(o)(-)(Py)) exhibit a quasi-reversible Cu(I)/Cu(II) redox behavior with E(pa) = +719 mV and E(pc) = +538 mV for 4, E(pa) = +636 mV and E(pc) = -316 mV for 5, and E(pa) = +418 mV and E(pc) = -319 mV for 6.
合成了具有双功能化同型蝎形配体（氢三（硫代三唑基）硼酸盐[Li(Tr(Me,o)(-)(Py)) (1) 和 Li(Tr(Mes,Me)) (2)]）以及异型蝎形配体氢[双（硫代三唑基）-3-（2-吡啶基）吡唑基]硼酸盐[K(Br(Mes)pz(o)(-)(Py))] (3) 的双核 Cu(I) 配合物，并通过晶体学对其进行了表征。配合物Cu(Tr(Mes,Me)) (4) 和Cu(Tr(Me,o)(-)(Py)) (5) 呈现出相似的配位几何结构，其中每个金属被三个硫羰基以三角排列方式包围。两种化合物中均存在[B-H...Cu]三中心两电子相互作用，导致整体配位变为四面体畸变（每个金属的 S(3)H 配位）。配合物Cu(Br(Mes)pz(o)(-)(Py)) (6) 呈现出三角几何结构，其中金属与两个硫羰基和一个桥连吡唑基氮原子相互作用。与吡啶氮原子的弱接触完成了金属的配位（每个金属的 S(2)N,N' 配位）。Cu(Tr(Mes,Me))、Cu(Tr(Me,o)(-)(Py)) 和Cu(Br(Mes)pz(o)(-)(Py)) 在溶液中表现出动态行为，变温核磁共振光谱证明了这一点，并且对于 5 和 6，在 270 K 时，两种处于平衡状态的物种[5 (CDCl(3)) 的比例为 2/1，6 (CD(2)Cl(2)) 的比例为 3/2]在 (1)H NMR 光谱中是可区分的。在 270 K 记录二维 NOESY 光谱有助于确定 5 和 6 每种异构体的溶液分子几何结构归属。通过对合并温度的评估确定了两种平衡状态的活化自由能（DeltaG()(Tc)）。进行了 DFT 计算以描述 5 和 6 的次要异构体的合理分子几何结构，并提出主要异构体和次要异构体之间可能的互变机制。使用 0.1 M TBAHFP 或 TBAOTf 作为支持电解质，在 CH(2)Cl(2)（3 和 6）或 CH(2)Cl(2)/CH(3)CN（1/1，v/v）（2、4 和 5）溶液中记录循环伏安图。Cu(Tr(Mes,Me))、Cu(Tr(Me,o)(-)(Py)) 和Cu(Br(Mes)pz(o)(-)(Py)) 表现出准可逆的 Cu(I)/Cu(II) 氧化还原行为，4 的 E(pa) = +719 mV 和 E(pc) = +538 mV，5 的 E(pa) = +636 mV 和 E(pc) = -316 mV，6 的 E(pa) = +418 mV 和 E(pc) = -319 mV。
