Coligand driven diverse organometallation in benzothiazolyl-hydrazone derivatized pyrene: ortho vs. peri C–H activation†,New Journal of Chemistry

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Coligand driven diverse organometallation in benzothiazolyl-hydrazone derivatized pyrene: ortho vs. peri C–H activation†
New Journal of Chemistry ( IF 2.7 ) Pub Date : 2019-12-16 , DOI: 10.1039/c9nj05088d
Soumitra Dinda _{1,

2,

3,

4} , Sarat Chandra Patra _{1,

4,

5,

6,

7} , Subhadip Roy _{1,

4,

8} , Supriyo Halder _{1,

4,

5,

6,

7} , Thomas Weyhermüller _{9,

10,

11} , Kausikisankar Pramanik _{1,

4,

5,

6,

7} , Sanjib Ganguly _{1,

2,

3,

4}

Affiliation

Benzothiazolyl hydrazones 1 (H₂L^PAH) incorporating polycyclic aromatic hydrocarbons (PAHs) have been fabricated as hemilabile scaffolds and elegantly utilized the inbuilt nitrogen donors as a proficient directing group (DG) to bring about ruthenium(II) assisted C–H activation in PAHs at both the peri and ortho positions. An isomeric pair of organometallics having formula [Ru^II(L^Pyr)(CO)(PPh₃)₂] (peri: 3a, ortho: 5a) have been conveniently prepared by varying the [Ru^II] precursors with H₂L^Pyr. In contrast, only one type of activated product viz. [Ru^II(L^Anc)(CO)(PPh₃)₂] 3b has been obtained with the 9-anthracene derivative of 1, H₂L^Anc, under analogous reaction conditions. The underlying mechanistic aspects have been elucidated by isolating the thermally unstable intermediates viz. [Ru^II(HL^Pyr)Cl(CO)(PPh₃)₂] 2a and [Ru^II(HL^Pyr)H(CO)(PPh₃)₂] 4a in the course of the peri and ortho C–H activation processes, respectively. The coligand (Cl/H) plays a vital role to bring about the C–H activation at the desired positions via formation of either a four- or five-membered metallacycle in 2a and 4a, respectively. The activation process vis-à-vis Ru–C bond formation in 3a can be achieved smoothly from 2a by a thermal transformation route, which proceeds via an initial rupture of the Ru–N_hydrazonyl bond. In contrast, the trans influential hydride coligand prefers a five-membered chelate to avoid confrontation with N_hydrazone in 4a, which in turn furnishes exclusively ortho activation owing to the close approach of the Ru–H bond towards ortho-H in pyrene. The organometallated complexes exhibit oxidative responses at mild potential. EPR and computational studies indicate that the redox activity originates from the ligand-centered orbitals. The observed rich optoelectronic features are analysed primarily as ¹ILCT admixed with ¹MLCT components by theoretical means, indicating an appreciable accumulation of electron density over the ligand backbone in their ground states.

中文翻译：

配位体驱动的苯并噻唑基hydr pyr衍生的diverse中的各种有机金属化：邻位vs. CHH活化†

结合了多环芳烃（PAHs）的苯并噻唑1（H ₂ L ^PAH）被制成半不稳定的支架，并优雅地利用内置的氮供体作为熟练的导向基团（DG）来实现钌（II）辅助C–H活化周围和邻位的PAHs 。通过改变[Ru]可以方便地制备具有式[Ru ^II（L ^Pyr）（CO）（PPh ₃）₂ ]（peri：3a，ortho：5a）的有机金属异构体对。^二]前体与H₂ L的^Pyr。相反，仅一种类型的活化产物即。[Ru^II（L^Anc）（CO）（PPh₃）₂ ] 3b在类似的反应条件下用1的9-蒽衍生物H₂ L^Anc得到。底层机制方面已通过隔离热不稳定的中间体阐明即。[Ru^II（HL^Pyr）Cl（CO）（PPh₃）₂ ] 2a和[Ru^II（HL^Pyr）H（CO）（PPh₃）₂ ] 4a分别在周围和邻位C–H活化过程中发生。大肠菌素（Cl / H）通过在2a和4a中分别形成四元或五元金属环，在所需位置实现CH活化起着至关重要的作用。相对于Ru–C键在3a中形成的活化过程可以通过热转化途径从2a顺利完成，该过程通过Ru–N_肼基键的初始断裂而进行。相反，反式有影响氢化共配体偏好的五元螯合物到用N避免对抗_腙在4a中，而这又配料专门邻由于朝向的Ru-H键的紧密接近激活邻芘-H。有机金属化的配合物在中等电位下表现出氧化反应。EPR和计算研究表明，氧化还原活性起源于以配体为中心的轨道。观察到的丰富的光电特征主要是通过理论方法将¹ ILCT与¹ MLCT组分混合在一起进行分析，表明在配体主链上处于基态的电子密度有明显的积累。

更新日期：2020-01-14

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