Unprecedented coordination modes and demetalation pathways for unbridged polyenyl ligands. Ruthenium eta1,eta4-cycloheptadienyl complexes from allyl/alkyne cycloaddition.
Unprecedented coordination modes and demetalation pathways for unbridged polyenyl ligands. Ruthenium eta1,eta4-cycloheptadienyl complexes from allyl/alkyne cycloaddition.
复制标题
非桥连多烯基配体前所未有的配位模式和脱金属途径。
DOI：
10.1021/ja0556023
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发表时间：
2005
影响因子：
15
通讯作者：
J. Stryker
中科院分区：
文献类型：
--
作者：
C. Older;R. McDonald;J. Stryker
阳离子（eta6-六亚甲基苯）钌（II）介导烯丙基和炔基配体的[3 + 2 + 2]环加成，导致eta1，eta4-环七烯基配合物的意外分离，这是一种前所未有的简单有机环过渡金属配合物的配位模式。用过量的乙烯处理未取代的烯丙基配合物，得到非共轭的、eta1、eta4配位配合物作为动力学反应产物；这个络合物在80℃时缓慢重排成热力学上更稳定的共轭乙烷-环庚二烯基异构体。eta1，eta4配位异构体在室温下具有流动性，通过易于消除/重新插入的-氢化物与环庚三烯氢化物中间体进行快速可逆的平衡。重新插入过程具有明显的区域选择性，在室温下只返回非共轭的eta1， eta1 -环庚二烯基异构体。对于含有二甲基乙炔二羧酸酯（DMAD）作为一个或两个炔组分的反应，尽管在到达一个观察到的eta1，eta4-异构体之前，在所有可能的eta1，eta4-环庚二烯基和环庚三烯氢化异构体之间经历了平衡，但在动力学和热力学上都有利于eta1，eta4-配位。对于这个系列，即使经过长时间加热，也没有观察到乙烷- 5配位的异构化。相比之下，在室温或低于室温的条件下，DMAD和苯乙炔的环化反应直接发生在eta5-环庚二烯异构体上，这表明该体系在能量上仍然可以获得eta5-配位。基于dmad的环化反应产生结构多样的次要副产物，包括eta1，eta4-甲烷环己二烯和无环的eta3，eta2-庚二烯异构体，这些异构体已经被分离出来并进行了严格的表征。七元环上不寻常的eta1，eta4配位导致碘解氧化脱金属产生独特的新有机产物。因此，与过量碘反应产生桥接三环含环丙烷内酯或取代环庚三烯，产率好，但有时是可变的，取决于底物和特定的反应条件。这些反应中的钌以高收率的形式以有趣的阳离子多三碘假二聚体（eta6-六甲基苯）钌的形式返回，得到三碘盐。这种Ru（III）配合物，以及几种具有代表性的Ru（II）环化产物，已经通过x射线晶体学在固态下进行了表征。
Cationic (eta6-hexamethylbenzene)ruthenium(II) mediates the [3 + 2 + 2] cycloaddition of allyl and alkyne ligands, leading to the unexpected isolation of eta1,eta4-cycloheptadienyl complexes, an unprecedented coordination mode for transition metal complexes of simple organic rings. The nonconjugated, eta1,eta4-coordinated complex is obtained as the kinetic reaction product from treatment of the unsubstituted allyl complex with excess ethyne; this complex rearranges slowly at 80 degrees C to the thermodynamically more stable conjugated eta5-cycloheptadienyl isomer. The eta1,eta4-coordinated isomer is fluxional at room temperature, undergoing rapid and reversible equilibration with a cycloheptatriene hydride intermediate via facile beta-hydride elimination/reinsertion. The reinsertion process is remarkably regioselective, returning the nonconjugated eta1,eta4-cycloheptadienyl isomer exclusively at room temperature. For reactions incorporating dimethylacetylene dicarboxylate (DMAD) as one or both of the alkyne components, eta1,eta4-coordination appears to be both kinetically and thermodynamically favored, despite undergoing equilibration among all possible eta1,eta4-cycloheptadienyl and cycloheptatriene hydride isomers prior to arriving at one observed eta1,eta4-isomer. For this series, no isomerization to eta5-coordination is observed even upon prolonged heating. In contrast, the cyclization incorporating both DMAD and phenylacetylene proceeds directly to the eta5-cycloheptadienyl isomer at or below room temperature, indicating that eta5-coordination remains energetically accessible to this system. The DMAD-based cyclization reactions produce structurally diverse minor byproducts, including both eta1,eta4-methanocyclohexadiene and acyclic eta3,eta2-heptadienyl isomers, which have been isolated and rigorously characterized. The unusual eta1,eta4-coordination of the seven-membered ring leads to unique new organic products upon oxidative demetalation by iodinolysis. Thus, reactions with excess iodine afford bridged tricyclic cyclopropane-containing lactones or substituted cycloheptatrienes in good but sometimes variable yields, depending on the substrate and specific reaction conditions. The ruthenium in these reactions is returned in high yield as the interesting cationic mu-triiodo pseudodimer of (eta6-hexamethylbenzene)ruthenium, which is obtained as a triiodide salt. This Ru(III) complex, along with several representative Ru(II) cyclization products, has been characterized in the solid state by X-ray crystallography.