Kersting Berthold, Siebert Dieter
Institut für Anorganische und Analytische Chemie and Institut für Physikalische Chemie, Universität Freiburg, Albertstrasse 21, D-79104 Freiburg, Germany.
Inorg Chem. 1998 Jul 27;37(15):3820-3828. doi: 10.1021/ic980131p.
A coordinatively unsaturated dinuclear Ni(II) complex of the tridentate ligand 2,6-di(aminomethyl)-4-tert-butyl-thiophenol (HL) has been synthesized and investigated in the context of ligand binding and oxidation state changes. The starting complex [L(2)Ni(2)]BPh(4) (1) is readily prepared from NaL, NiCl(2).6H(2)O, and NaBPh(4) in methanol. Compound 1.CH(3)CN.CH(3)OH crystallizes from an acetonitrile/methanol mixed-solvent system in monoclinic space group P2(1)/n with a = 21.940(4) Å, b = 13.901(3) Å, c = 23.918(5) Å, beta = 110.00(3) degrees, and Z = 4. The structure consists of dinuclear L(2)Ni(2) cations with two distorted planar cis-N(2)S(2)Ni coordination units joined by the thiophenolate sulfur atoms. The molecule has idealized C(2)(v)() symmetry. Complex 1 readily adds another 1 equiv of HL to afford the pale green complex [L(3)Ni(2)]Cl (2). The dinuclear structure and its formulation as a 3:2 complex (six-coordinate Ni ions) is derived from UV spectroscopy, cyclic voltammetry, and single-crystal X-ray diffraction of its oxidation product, L(3)Ni(2). The dication was prepared by chemical oxidation of 2 with iodine in DMF and isolated as the dark brown BPh(4)(-) salt, [L(3)Ni(2)]BPh(4).CH(3)OH (3), which crystallizes in monoclinic space group P2(1)/c with a = 23.678(5) Å, b = 20.090(4) Å, c = 16.797(3) Å, beta = 106.16(3) degrees, and Z = 4. Complex 3 is the first structurally characterized example that features a bioctahedral N(3)Ni(&mgr;(2)-SR)(3)NiN(3) core. Distortions from D(3)(h)() symmetry suggest that 3 is a trapped-valence Ni(II)Ni(III) compound. The Ni-S and Ni-N bond lengths vary from 2.2975(9) to 2.4486(12) Å and from 2.027(3) to 2.120(3) Å, respectively. On the CV time scale complex 2 undergoes two reversible electron-transfer reactions at E(1/2) = -0.02 and +0.44 V vs SCE, affording 3 and the transient dark green trication L(3)Ni(2) (tau(1/2) approximately 15 min at 295 K), respectively. While 2 is EPR silent, the EPR spectrum of a powdered sample of 3 reveals g( perpendicular) = 4.0 and g( parallel) = 2.09 at 77 K, consistent with an S = (3)/(2) spin state of the mixed-valent Ni(II)Ni(III) complex.
已合成了三齿配体2,6 - 二（氨甲基）-4 - 叔丁基苯硫酚（HL）的配位不饱和双核Ni（II）配合物，并在配体结合和氧化态变化的背景下进行了研究。起始配合物[L(2)Ni(2)]BPh(4)（1）很容易由NaL、NiCl(2)·6H(2)O和NaBPh(4)在甲醇中制备得到。化合物1·CH(3)CN·CH(3)OH从乙腈/甲醇混合溶剂体系中结晶，属于单斜晶系空间群P2(1)/n，a = 21.940(4) Å，b = 13.901(3) Å，c = 23.918(5) Å，β = 110.00(3)°，Z = 4。其结构由双核L(2)Ni(2)阳离子组成，两个扭曲的平面顺式-N(2)S(2)Ni配位单元通过苯硫酚盐硫原子相连。该分子具有理想的C(2)(v)对称性。配合物1很容易再加入1当量的HL，得到浅绿色配合物[L(3)Ni(2)]Cl（2）。双核结构及其作为3:2配合物（六配位Ni离子）的组成是通过其氧化产物L(3)Ni(2)的紫外光谱、循环伏安法和单晶X射线衍射推导出来的。二价阳离子是通过在DMF中用碘对2进行化学氧化制备的，并以深棕色BPh(4)(-)盐[L(3)Ni(2)]BPh(4)·CH(3)OH（3）分离出来，它在单斜晶系空间群P2(1)/c中结晶，a = 23.678(5) Å，b = 20.090(4) Å，c = 16.797(3) Å，β = 106.16(3)°，Z = 4。配合物3是第一个具有生物八面体N(3)Ni(μ(2)-SR)(3)NiN(3)核心且经结构表征的例子。与D(3)(h)对称性的偏差表明3是一种捕获价态的Ni（II）Ni（III）化合物。Ni - S和Ni - N键长分别在2.2975(9)至2.4486(12) Å和2.027(3)至2.120(3) Å之间变化。在循环伏安时间尺度上，配合物2在相对于SCE的E(1/2) = -0.02和 +0.44 V处经历两个可逆的电子转移反应，分别生成3和瞬态深绿色三价阳离子L(3)Ni(2)（在295 K时半衰期约为15分钟）。虽然2的电子顺磁共振（EPR）无信号，但3的粉末样品在77 K时的EPR光谱显示g(垂直) = 4.0和g(平行) = 2.09，这与混合价态Ni（II）Ni（III）配合物的S = (3)/(2)自旋态一致。
