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Four-coordinated see-saw N-(aryl)-2-(propan-2-ylidene)hydrazinecarbothioamide complexes of nickel(ii), copper(ii) and zinc(ii) and their propensity for catalytic cyclisation†
Dalton Transactions ( IF 3.5 ) Pub Date : 2018-03-07 00:00:00 , DOI: 10.1039/c8dt00453f
Arup Tarai 1, 2, 3, 4 , Jubaraj B. Baruah 1, 2, 3, 4
Affiliation  

A series of mononuclear complexes of divalent nickel and zinc with N-(4-methoxyphenyl)-2-(propan-2-ylidene)hydrazine carbothioamide (H2Lmethoxy) as well as with N-(4-nitrophenyl)-2-(propan-2-ylidene)hydrazine carbothioamide (H2Lnitro) have been structurally characterised. Among these two ligands, H2Lnitro formed an analogous copper(II) complex to that of nickel and zinc, whereas H2Lmethoxy undergoes a catalytic cyclisation reaction in the presence of copper(II) nitrate trihydrate. Control experiments based on ESR have revealed that copper(II) is reduced to copper(I) and reverts back to copper(II) as the cyclisation reaction proceeds, generating a catalytic reaction. The crystal structures of H2Lnitro and H2Lmethoxy show that the plane of the phenyl ring with respect to the plane of the hydrazine-containing unit in H2Lnitro is more or less coplanar, whereas the H2Lmethoxy molecule is non-planar with a 67.05° angle between these planes. DFT calculations have shown a large difference in the localisation of electrons in the HOMO of the two ligands; the HOMO of H2Lmethoxy is spread over the aromatic ring, which facilitates involvement of the ring in the formation of a C–N bond through a single electron transfer to a copper(II) ion. This cyclic product has a distinguishable absorption maximum at 299 nm, which makes it possible to detect copper ions over other first row transition metal ions and alkali metal ions. On the other hand, the copper(II) complex of H2Lnitro shows a characteristic absorption at 395 nm in the presence of fluoride ions, whereas the free ligand with fluoride shows absorption at 418 nm, which shows that the interactions of the ligand with fluoride and with the corresponding copper complex widely differ.

中文翻译:

镍(ii),铜(ii)和锌(ii)的 四配位跷跷板N-(芳基)-2-(丙-2-亚烷基)肼基碳硫磺酰胺配合物及其催化环化的趋势

二价镍和锌与N-(4-甲氧基苯基)-2-(丙-2-亚烷基)肼碳硫酰胺(H 2 L甲氧基)以及与N-(4-硝基苯基)-2-的一系列单核络合物(丙烷-2-亚烷基)肼碳硫酰胺(H 2 L硝基)的结构特征。在这两个配体中,H 2 L硝基与镍和锌形成类似的铜(II)配合物,而H 2 L甲氧基在铜(II)存在下进行催化环化反应)三水硝酸盐。基于ESR的对照实验表明,随着环化反应的进行,铜(II)还原为铜(I),然后还原为铜(II),从而产生催化反应。H 2 L硝基H 2 L甲氧基的晶体结构表明,相对于H 2 L硝基中的含肼单元的平面,苯环的平面或多或少是共面的,而H 2 L甲氧基的分子是非平面的,这些平面之间的夹角为67.05°。DFT计算表明,在两个配体的HOMO中电子的定位存在很大差异。H 2 L甲氧基的HOMO散布在芳环上,这通过单电子转移到铜(II)离子上促进了该环参与C-N键的形成。该环状产物在299 nm处具有明显的吸收最大值,这使得可以检测其他第一行过渡金属离子和碱金属离子上的铜离子。另一方面,H 2 L硝基的铜(II)配合物 在氟离子存在下,在395 nm处有一个特征吸收,而带有氟的游离配体在418 nm处有吸收,这表明该配体与氟化物以及与相应的铜络合物之间的相互作用大相径庭。
更新日期:2018-03-07
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