揭示甲醛肟过渡金属配合物的结构,Inorganic Chemistry

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揭示甲醛肟过渡金属配合物的结构
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2021-04-07 , DOI: 10.1021/acs.inorgchem.0c03362
Ivan S. Golovanov ₁ , Roman S. Malykhin ₁ , Vladislav K. Lesnikov ₁ , Yulia V. Nelyubina ₂ , Valentin V. Novikov ₂ , Kirill V. Frolov ₃ , Andrey I. Stadnichenko ₄ , Evgeny V. Tretyakov ₁ , Sema L. Ioffe ₁ , Alexey Yu. Sukhorukov _{1,

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Affiliation

铁（III），镍（II）和锰（II）氯化物与福尔多肟环三聚体（tfoH ₃）和1,4,7-三氮杂环壬烷（tacn）的需氧反应可产生不确定稳定的通式[M（tacn）（ tfo）] Cl。尽管自19世纪末以来就已经知道了福尔多肟络合物的形成并用于分光光度法测定d-金属（福尔达肟方法），但这些配位化合物的结构至今仍难以捉摸。根据X射线分析，[M（tacn）（tfo）] ⁺阳离子具有扭曲的金刚烷样结构，金属离子由去质子化的tfoH _3的三个氧原子配位配体。该金属具有正式的+4氧化态，这对于铁和镍的有机络合物而言是非典型的。通过XPS，NMR，循环（CV）和微分脉冲（DPV）伏安法，Mössbauer光谱和DFT计算研究了[M（tacn）（tfo）] ⁺阳离子的电子结构。NBO分析证实，通过tfo ^3–配体对高价金属离子的异常稳定作用是由于氮原子通过超共轭将电子密度提供给金属-氧键的反键轨道所致。在环境条件下，对位[M（tacn）（tfo）] Cl的所有配合物在对硫代甲酚的好氧脱氢二聚反应中均表现出高催化活性。

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Revealing the Structure of Transition Metal Complexes of Formaldoxime

Aerobic reactions of iron(III), nickel(II), and manganese(II) chlorides with formaldoxime cyclotrimer (tfoH₃) and 1,4,7-triazacyclononane (tacn) produce indefinitely stable complexes of general formula [M(tacn)(tfo)]Cl. Although the formation of formaldoxime complexes has been known since the end of 19th century and applied in spectrophotometric determination of d-metals (formaldoxime method), the structure of these coordination compounds remained elusive until now. According to the X-ray analysis, [M(tacn)(tfo)]⁺ cation has a distorted adamantane-like structure with the metal ion being coordinated by three oxygen atoms of deprotonated tfoH₃ ligand. The metal has a formal +4 oxidation state, which is atypical for organic complexes of iron and nickel. Electronic structure of [M(tacn)(tfo)]⁺ cations was studied by XPS, NMR, cyclic (CV) and differential pulse (DPV) voltammetries, Mössbauer spectroscopy, and DFT calculations. Unusual stabilization of high-valent metal ion by tfo^3– ligand was explained by the donation of electron density from the nitrogen atom to the antibonding orbital of the metal–oxygen bond via hyperconjugation as confirmed by the NBO analysis. All complexes [M(tacn)(tfo)]Cl exhibited high catalytic activity in the aerobic dehydrogenative dimerization of p-thiocresol under ambient conditions.

更新日期：2021-04-19

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