Syntheses and electronic structures of one-electron-oxidized group 10 metal(II)-(disalicylidene)diamine complexes (Metal = Ni, Pd, Pt)
Syntheses and electronic structures of one-electron-oxidized group 10 metal(II)-(disalicylidene)diamine complexes (Metal = Ni, Pd, Pt)
复制标题
DOI：
10.1021/ja067022r
复制
发表时间：
2007-03-07
影响因子：
15
通讯作者：
Yamauchi, Osamu
中科院分区：
文献类型：
--
作者：
Shimazaki, Yuichi;Yajima, Tatsuo;Yamauchi, Osamu
H（2）tbu-salen的第10族金属（II）配合物（H（2）tbu-salen = N，N '-bis（3 ′，5 ′-二叔丁基亚水杨基）乙二胺）和H（2）tbu-salcn（H（2）tbu-salcn = N，N ′-双（3 '，5'-二叔丁基亚水杨基）-1，2-环己二胺）（叔丁基）苯酚部分，[Ni（tbu-salen）]（1a），[Ni（tbu-salcn）]（1b），[Pd（tbu-salen）]（2a），[Pd（tbu-salcn）]（2b），和[Pt [（tbu-salen）]（3）的制备和结构表征通过X射线衍射，并通过光谱和电化学方法确定了它们的单电子氧化物种的电子结构。所有的配合物具有单核结构，两个酚氧在一个非常相似的正方形平面几何协调。这些配合物在CH 2Cl 2中表现出相似的吸收光谱，表明它们在溶液中具有相似的结构。配合物的循环伏安图显示在E-1/2 = 0.82-1.05 V（vsAg/AgCl）处的准可逆氧化还原波，对应于相对稳定的单电子氧化物种的形成。1a、2a和3的电化学氧化或Ce（IV）氧化物质显示出一级衰变，在-20 ℃下的半衰期分别为83、20和148 min。Ni（II）配合物1a和1b在高于-80 ℃的CH 2Cl 2中单电子氧化时转化为苯氧基自由基，在低于-120 ℃时转化为Ni（III）-酚盐物种。的温度依赖性的转换是可逆的Ni（III）-酚盐基态，并被发现是由溶剂的价互变异构。单电子氧化的1b被分离为具有Ni（II）-苯氧基自由基基态的[Ni（tbu-salcn）]NO3（4）。Pd（II）配合物2a和2b的单电子氧化物种与Ni（II）配合物的不同，Pd（II）-苯氧基自由基物种在5-300 K范围内在CH_2Cl_2中为基态。2b的单电子氧化形式[Pd（tbu-salcn）]NO3（5）被分离为深绿色粉末，被发现是Pd（II）-苯氧基自由基络合物。另一方面，Pt（II）配合物3的单电子氧化物种的ESR光谱在低于-80 ° C的CH 2Cl 2中表现出与温度无关的大g各向异性，而其在-60 ° C的共振拉曼光谱在1600 cm（-1）处显示苯氧基自由基带的nu（8 α）。这些结果表明，Pt（II）-苯氧基自由基物种的基态具有大的自由基电子自旋分布在Pt中心。3的单电子氧化得到固体[Pt（tbu-salen）]NO3（6），其中Pt中心的氧化态被确定为ca。来自XPS和XANES测量的+2.5。
Group 10 metal(II) complexes of H(2)tbu-salen (H(2)tbu-salen = N,N'-bis(3',5'-di-tert-butylsalicylidene)ethylenediamine) and H(2)tbu-salcn (H(2)tbu-salcn = N,N'-bis(3',5'-di-tert-butylsalicylidene)-1,2-cyclohexanediamine) containing two 2,4-di(tert-butyl)phenol moieties, [Ni(tbu-salen)] (1a), [Ni(tbu-salcn)] (1b), [Pd(tbu-salen)] (2a), [Pd(tbu-salcn)] (2b), and [Pt(tbu-salen)] (3), were prepared and structurally characterized by X-ray diffraction, and the electronic structures of their one-electron-oxidized species were established by spectroscopic and electrochemical methods. All the complexes have a mononuclear structure with two phenolate oxygens coordinated in a very similar square-planar geometry. These complexes exhibited similar absorption spectra in CH2Cl2, indicating that they all have a similar structure in solution. Cyclic voltammograms of the complexes showed a quasi-reversible redox wave at E-1/2 = 0.82-1.05 V (vs Ag/AgCl), corresponding to formation of the relatively stable one-electron-oxidized species. The electrochemically oxidized or Ce(IV)-oxidized species of 1a, 2a, and 3 displayed a first-order decay with a half-life of 83, 20, and 148 min at -20 degrees C, respectively. Ni(II) complexes 1a and 1b were converted to the phenoxyl radicals upon one-electron oxidation in CH2Cl2 above -80 degrees C and to the Ni(III)-phenolate species below -120 degrees C. The temperature-dependent conversion was reversible with the Ni(III)-phenolate ground state and was found to be a valence tautomerism governed by the solvent. One-electron-oxidized 1b was isolated as [Ni(tbu-salcn)]NO3 (4) having the Ni(II)-phenoxyl radical ground state. One-electron-oxidized species of the Pd(II) complexes 2a and 2b were different from those of the Ni(II) complexes, the Pd(II)-phenoxyl radical species being the ground state in CH2Cl2 in the range 5-300 K. The one-electron-oxidized form of 2b, [Pd(tbu-salcn)]NO3 (5), which was isolated as a dark green powder, was found to be a Pd(II)-phenoxyl radical complex. On the other hand, the ESR spectrum of the one-electron-oxidized species of Pt(II) complex 3 exhibited a temperature-independent large g anisotropy in CH2Cl2 below -80 degrees C, while its resonance Raman spectrum at -60 degrees C displayed nu(8a) of the phenoxyl radical band at 1600 cm(-1). These results indicated that the ground state of the Pt(II)-phenoxyl radical species has a large distribution of the radical electron spin at the Pt center. One-electron oxidation of 3 gave [Pt(tbu-salen)]NO3 (6) as a solid, where the oxidation state of the Pt center was determined to be ca. +2.5 from the XPS and XANES measurements.