Chemistry of tetravalent nickel and related species. 4. The situation where nickel(III) is stabilized by amine-imine-oxime ligands and nickel(IV) is not formed
Chemistry of tetravalent nickel and related species. 4. The situation where nickel(III) is stabilized by amine-imine-oxime ligands and nickel(IV) is not formed
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DOI：
10.1002/chin.198028281
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发表时间：
1980-04
期刊：
影响因子：
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通讯作者：
A. Singh;A. Chakravorty
中科院分区：
文献类型：
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作者：
A. Singh;A. Chakravorty
异亚硝基酮与四亚乙基五胺以1：1的比例反应生成六齿配体（HRR 'Y），得到假八面体镍（II）配合物Ni（HRR' Y）（ClO 4）Dq = 1250 cm-1;μ eff = 3μ B）.用碱性过硫酸铵将其氧化，生成Ni（RR 'Y）（Cl 0 4）2的红色晶体，该晶体（i）将铁（II）氧化为铁（III），反应化学计量比为Fe：Ni=1：1，（ii）具有μ eff = 2. 1 μB，（iii）在轴向场中显示S=1/2的多晶EPR谱特征（gp = 2. 04; g = 2. 14），（iv）经历单电子电化学还原但不氧化。因此，Ni（RR 'Y）2+含有氧化态为+3的镍。循环伏安法研究表明，在pH 6附近，Ni（RR 'Y）2+ +e - + H + Ni（HRR' Y）2+的反应过程是准可逆的，E°′ 298 V vs. SCE = 0.68 V。在高达+0.9V时没有检测到镍（IV）物质形成的迹象。本文和其他地方描述的各种胺-亚胺-肟配体的络合行为以及用每种配体可实现的镍的各种氧化态的比较表明，对于金属氧化态的每一个单位增加（高于+2），需要存在至少一个肟官能团。仅具有一个肟官能团的HRR ′ Y配体系统稳定镍（III），但不稳定镍（IV）。还报道了低自旋铁（II）配合物Fe（HRR 'Y）（C10 4）2。这些镍（II）和镍（III）配合物的红外光谱和电子光谱进行了描述和比较。铁（II）和镍（III）的配合物表现出MLCT和LMCT过渡，分别在可见光区（~ 500 nm）。
New hexadentate ligands (HRR'Y) generated by reaction of isonitroso ketones with tetraethylenepentamine in 1:1 ratio yield pscudooctahedral nickel(II) complexes Ni(HRR'Y)(CIO 4 )Dq≈1250 cm -1 ;μ eff ≈3μ B ). These are oxidized by alkaline ammonium persulfate to produce red crystals of Ni(RR'Y)(CI0 4 ) 2 which (i) oxidize iron(II) to iron(III), the reaction stoichiometry being Fe:Ni=1:1, (ii) have μ eff ≈2.1 μB, (iii) exhibit polycrystalline EPR spectra characteristic of S=1/2 in axial field (gp≈2.04; g⊥≈2.14), and (iv) undergo a ono-electron electrochemical reduction but no oxidation. Thus Ni(RR'Y)2+ contains nickel in the oxidation state +3. Extensive cyclic voltammetric studies have led to the identification of the following quasi-reversible process near pH 6: Ni(RR'Y) 2+ +e - + H + Ni(HRR'Y) 2+ with E°′ 298 ≈0.68 V vs. SCE. No sign of the formation of nickel( IV) species could be detected up to +0.9 V. Comparison of the ocnnplexing behavior of the various amine-imine-oxime ligands described in this paper and elsewhere and the various oxidation states of nickel achievable with each suggests that for each unit increase (above +2) in the oxidation state of the metal, the presence of at least one oxime function is needed. The HRR'Y ligand system having only one oxime function stabilizes nickel(III) but not nickel(IV). The low-spin iron(II) complexes Fe(HRR'Y)(C10 4 ) 2 are also reported. The IR and electronic spectra of these and the nickel(II) and nickel(III) complexes are described and compared. The iron(II) and nickel(III) complexes exhibit MLCT and LMCT transitions, respectively, in the visible region (∼500 nm).