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Bis(imino)aryl NCN pincer cobalt complexes: synthesis and disproportionation.
Dalton Transactions ( IF 4 ) Pub Date : 2020-04-28 , DOI: 10.1039/d0dt00747a
Li-Cheng Huang 1 , Jing-Shun Zhang 1 , Teng Jia 1 , Ying Mu 1 , Wei Gao 1
Affiliation  

Treatment of iPr[NCN]Br (2,6-(2,6-iPr2C6H3C[double bond, length as m-dash]N)2C6H3Br) with nBuLi in THF and the subsequent addition of 1 equiv. of CoCl2, CoCl2(Ph3P)2, and CoBr2 gave pincer Co(ii) complexes {iPr[NCN]Co(μ-Cl)}2 (1d), iPr[NCN]CoClPh3P (1d-Ph3P), and iPr[NCN]CoBr2·Li(THF)4 (1d-LiBr) respectively in moderate yields, whereas the slow addition of in situ prepared iPr[NCN]Li to CoCl2 in THF afforded an unexpected mixed-valence cobalt(i/ii) complex κ2C,N,η6-iPr[NCN]Co-κN-CoCl3·Li(THF)4 (2d). Complex 2d was probably formed via a disproportionation reaction of the iPr[NCN]Co(ii) species with excess CoCl2 during the reaction. Nevertheless, addition of CoCl2 to in situ formed 1d-THF at room temperature did not lead to 2d but gave a trinuclear Co(ii) complex {iPr[NCN]Co(μ-Cl)(μ-Br/Cl)}2Co (1d-CoCl2) in moderate yield. Similar reactions using ligands containing small ortho groups in the imine moieties R[NCN]Br (2,6-(2,6-Me2C6H3C[double bond, length as m-dash]N)2C6H3Br, Me[NCN]Br; 2,6-(2,6-Et2C6H3C[double bond, length as m-dash]N)2C6H3Br, Et[NCN]Br; 2,6-(2,4,6-Me3C6H2C[double bond, length as m-dash]N)2C6H3Br, Mes[NCN]Br) and CoBr2, regardless of the reactant addition sequence, afforded mixed-valence cobalt(i/ii) complexes {κ2C,N,η6-R[NCN]Co-κN-CoBr(μ-Br)}2 (Me[NCN] (2a), Et[NCN] (2b), and Mes[NCN] (2c)), suggesting that the bulkiness of the ortho-groups in the imine moieties of the ligands plays an important role in the disproportionation reaction. In the presence of PMe3, Co(ii) complexes κ2C,N-R[NCN]CoBr(PMe3)2 (3a-d) and a bisligated cobalt(ii) complex κ3N,C,N-κ2C,N-iPr[NCN]2CoPMe3 (4d) can be prepared respectively in high yields. The molecular structures of 1d-LiBr, 1d-CoCl2, 2b, 2d, 3a, and 4d were confirmed by X-ray crystallographic analysis and the detailed mechanisms of the disproportionation reaction were proposed.

中文翻译:

双(亚氨基)芳基NCN钳制钴配合物:合成和歧化。

在THF中用nBuLi处理iPr [NCN] Br(2,6-(2,6-iPr2C6H3C [双键,长度为m-虚线N] 2C6H3Br),然后加入1当量。CoCl2,CoCl2(Ph3P)2和CoBr2的合成得到钳制的Co(ii)络合物{iPr [NCN] Co(μ-Cl)} 2(1d),iPr [NCN] CoClPh3P(1d-Ph3P)和iPr [NCN ] CoBr2·Li(THF)4(1d-LiBr)的产率中等,而将原位制备的iPr [NCN] Li缓慢添加到THF中的CoCl2中,则得到了出乎意料的混合价钴(i / ii)复合物κ2C, N,η6-iPr[NCN]Co-κN-CoCl3·Li(THF)4(2d)。在反应过程中,iPr [NCN] Co(ii)物种与过量的CoCl2发生歧化反应,可能形成络合物2d。不过,在室温下向原位添加CoCl2形成1d-THF并不会导致2d,而是产生了三核Co(ii)络合物{iPr [NCN] Co(μ-Cl)(μ-Br/ Cl)} 2Co( 1d-CoCl2),收率中等。使用亚胺部分R [NCN] Br(2,6-(2,6-Me2C6H3C [双键,长度为m-N] N)2C6H3Br,Me [NCN] Br; 2 6-(2,6-Et2C6H3C [双键,长度为m-破折号] N)2C6H3Br,Et [NCN] Br; 2,6-(2,4,6-Me3C6H2C [双键,长度为m-破折号] N)2C6H3Br,Mes [NCN] Br)和CoBr2,无论反应物的添加顺序如何,均可提供混合价的钴(i / ii)配合物{κ2C,N,η6-R[NCN]Co-κN-CoBr(μ- Br)} 2(Me [NCN](2a),Et [NCN](2b)和Mes [NCN](2c)),表明配体亚胺部分中邻位基团的体积很大在歧化反应中的作用。在存在PMe3的情况下,Co(ii)配合物κ2C,NR [NCN] CoBr(PMe3)2(3a-d)和双键钴(ii)配合物κ3N,C,N-κ2C,N-iPr [NCN] 2CoPMe3 (4d)可以分别以高产率制备。
更新日期:2020-03-25
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