[(1,2,4-tri-tert-butylcyclopentadienyl)(1,2,4-tri-tert-butylcyclopentadienyl(-H))Ce] | 832076-21-8

• 英文名称: [(1,2,4-tri-tert-butylcyclopentadienyl)(1,2,4-tri-tert-butylcyclopentadienyl(-H))Ce]
• 英文别名: (1,3,4-tri-tert-butylcyclopentadienyl)((Me3C)2C5H2C(Me)2CH2)Ce
• CAS: 832076-21-8
• 化学式: C₃₄H₅₇Ce
• 分子量: 605.947
• InChiKey: OVVQBWMGJRISNO-UHFFFAOYSA-N

计算性质

• 辛醇/水分配系数(LogP)：
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• 重原子数：
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• 可旋转键数：
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• 环数：
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• sp3杂化的碳原子比例：
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• 拓扑面积：
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• 氢给体数：
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• 氢受体数：
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反应信息

• 作为反应物：
  描述：

  三氟甲烷 、 [(1,2,4-tri-tert-butylcyclopentadienyl)(1,2,4-tri-tert-butylcyclopentadienyl(-H))Ce] 以 全氘代环己烷 为溶剂， 生成 bis(1,2,4-tri-tert-butylcyclopentadienyl)cerium hydride
  参考文献：
  名称：

  Hydrogen for Fluorine Exchange in C₆F₆ and C₆F₅H by Monomeric [1,3,4-(Me₃C)₃C₅H₂]₂CeH:  Experimental and Computational Studies

  摘要：

  The net reaction of monomeric CP'2CeH [Cp' = 1,3,4-(Me3C)(3)(C5H2)] in C6D6 with C6F6 is CP'2CeF, H-2, and tetrafluorobenzyne. The pentafluoropheny/metallocene, CP'Ce-2(C6F5), is formed as an intermediate that decomposes slowly to CP'2CeF and C6F4 (tetrafluorobenzyne), and the latter is trapped by the solvent C6D6 as a [2+4] cycloadcluct. In C6F5H, the final products are also CP'2CeF and H-2, which are formed from the intermediates CP'Ce-2(C6F5) and CP'Ce-2(2,3,5,6-C6F4H) and from an unidentified metallocene of cerium and the [2+4] cycloadducts of tetra- and trifluorobenzyne with C6D6. The hydride, fluoride, and pentafluoropheny/metallocenes are isolated and characterized by X-ray crystallography. DFT(B3PW91) calculations have been used to explore the pathways leading to the observed products of the exergonic reactions. A key step is a H/F exchange reaction which transforms C6F6 and the cerium hydride into C6F5H and CP'2CeF. This reaction starts by an eta(1)-F-C6F5 interaction, which serves as a hook. The reaction proceeds via a sigma bond metathesis where the fluorine ortho to the hook migrates toward H with a relatively low activation energy. All products observed experimentally are accommodated by pathways that involve C-F and C-H bond cleavages.

  DOI：

  10.1021/ja0451012
• 作为产物：
  描述：

  [(1,2,4-tri-tert-butylcyclopentadienyl)2Ce(η2-methoxymethylene)] 以 全氘代环己烷 为溶剂， 生成 [(1,2,4-tri-tert-butylcyclopentadienyl)(1,2,4-tri-tert-butylcyclopentadienyl(-H))Ce]
  参考文献：
  名称：

  Hydrogen for X-Group Exchange in CH₃X (X = Cl, Br, I, OMe, and NMe₂) by Monomeric [1,2,4-(Me₃C)₃C₅H₂]₂CeH: Experimental and Computational Support for a Carbenoid Mechanism

  摘要：

  The reactions between [1,2,4-(Me3C)(3)C5H2](2)CeH, referred to as Cp'2CeH, and CH3X, where X is Cl, Br, I, OMe, and NMe2, are described. The reactions fall into three distinct classes. Class a, where X = Cl, Br, and I, rapidly form Cp'2CeX and CH4 without formation of identifiable intermediates in the H-1 NMR spectra. Class b, where X = Me, proceeds rapidly to CP'Ce-2(eta(2)-CH2OMe) and H-2 and then to CP'2CeOMe and CH4. The methoxymethyl derivative is sufficiently stable to be isolated and characterized, and it is rapidly converted to Cp'2CeOMe in the presence of BPh3. Class c, where X = NMe2, does not result in formation of Cp'2CeNMe2, but deuterium labeling experiments show that H for D exchange occurs in NMe3. Density functional calculations DFT(B3PW91) on the reaction of (C5H5)(2)CeH, referred to as Cp2CeH, and CH3X show that the barrier for alpha-CH activation, resulting in formation of Cp2Ce(eta(2)-CH2X), proceeds with a relatively low activation barrier (Delta G(double dagger)), but the subsequent ejection of CH2 and trapping by H-2 has a higher barrier; the height of the second barrier lies in the order F, Cl, Br, I < OMe << NMe2, consistent with the experimental studies. The DFT calculations also show that the two-step reaction, which proceeds through a carbenoid intermediate, has a lower barrier than a direct one-step or-bond metathesis mechanism. The reaction of Cp2CeCH2OMe and BPh3 is calculated to be a low-activation barrier process, and the ylide, CH2(+)BPh3(-1), is a transition state and not an intermediate.

  DOI：

  10.1021/om9001846

文献信息

• Reactions of Monomeric [1,2,4-(Me₃C)₃C₅H₂]₂CeH and CO with or without H₂:  An Experimental and Computational Study
  作者：Evan L. Werkema、Laurent Maron、Odile Eisenstein、Richard A. Andersen

  DOI：10.1021/ja066482h

  日期：2007.3.1

  Addition of CO to [1,2,4-(Me3C)3C5H2]2CeH, CeH, in toluene yields the cis-( Ce)2(μ-OCHCHO), in which the cis-enediolate group bridges the two metallocene fragments. The cis-enediolate quantitatively isomerizes intramolecularly to the trans-enediolate in C6D6 at 100 °C over 7 months. When the solvent is pentane, Ce(OCH2)Ce forms, in which the oxomethylene group or the formaldehyde dianion bridges the

  将 CO 添加到甲苯中的 [1,2,4-(Me3C)3C5H2]2CeH,CeH 中产生顺式-(Ce)2(μ-OCHCHO)，其中顺式烯二醇基团桥接两个茂金属片段。顺式烯二醇在 7 个月内在 100 °C 下在 C6D6 中定量异构化为反式烯二醇。当溶剂为戊烷时，会形成 Ce(OCH2)Ce，其中氧亚甲基或甲醛二价阴离子桥接两个茂金属片段。顺式烯二醇被认为是通过将 CO 插入 Ce(OCH2)Ce 的 Ce-C 键中形成的，生成 CeOCH2COCe。顺式烯二醇酯的立体化学由 OCH2CO 片段中的 1,2-氢位移决定，该片段具有相对于卡宾孤对的 OC(H2) 键反周面。桥接氧亚甲基络合物与 H2 反应，但不与 CH4 反应，得到 CeOMe，它也是 CeH 与 CO 和 H2 的混合物反应的产物。氧亚甲基络合物与 CO 反应生成顺式烯二醇络合物。C5H5 模型茂金属的 DFT 计算表明.
• The reaction of bis(1,2,4-tri-t-butylcyclopentadienyl)ceriumbenzyl, Cp′2CeCH2Ph, with methylhalides: a metathesis reaction that does not proceed by a metathesis transition state
  作者：Evan L. Werkema、Richard A. Andersen、Laurent Maron、Odile Eisenstein

  DOI：10.1039/b918103b

  日期：——

  The experimental reaction between [1,2,4-(Me3C)3C5H2]2CeCH2Ph and CH3X, X = F, Cl, Br, and I, yields the metathetical exchange products, [1,2,4-(Me3C)3C5H2]2CeX and CH3CH2Ph. The reaction is complicated by the equilibrium between the benzyl derivative and the metallacycle [1,2,4-(Me3C)3C5H2][(Me3C)2C5H2C(CH3)2CH2]Ce, plus toluene since the metallacycle reacts with CH3X. Labelling studies show that the methyl group of the methylhalide is transferred intact to the benzyl group. The mechanism, as revealed by DFT calculations on (C5H5)2CeCH2Ph and CH3F, does not proceed by way of a four-center mechanism, a σ-bond metathesis, but by a lower barrier process involving a haptotropic shift of the Cp2Ce fragment so that at the transition state the para-carbon of the benzene ring is attached to the Cp2Ce fragment while the CH2 fragment of the benzyl group attacks CH3F that is activated by coordination to the metal ion. As a result the mechanism is classified as an associative interchange process.

  [1,2,4-(Me3C)3C5H2]2Ce Ph 和 X（X = F、Cl、Br 和 I）之间的实验反应产生了元交换产物 [1,2,4-(Me3C)3C5H2]2CeX 和 Ph。苄基衍生物和金属环 [1,2,4-(Me3C)3C5H2][(Me3C)2C5H2C(CH3)2 ]Ce 以及甲苯之间的平衡使反应变得复杂，因为金属环会与 X 发生反应。标记研究表明，甲基卤化物的甲基完整地转移到了苄基上。通过对 (C5H5)2Ce Ph 和 F 的 DFT 计算发现，该机理不是通过四中心机理（Ï-键元合成）进行的，而是通过涉及 Cp2Ce 片段的触变转移的较低障碍过程进行的，因此在过渡态，苯环的对位碳附着在 Cp2Ce 片段上，而苄基的 CH2 片段攻击因与金属离子配位而活化的 F。因此，该机制被归类为关联交换过程。
• Two [1,2,4-(Me₃C)₃C₅H₂]₂CeH Molecules are Involved in Hydrogenation of Pyridine to Piperidine as Shown by Experiments and Computations
  作者：Lionel Perrin、Evan L. Werkema、Odile Eisenstein、Richard A. Andersen

  DOI：10.1021/ic500133y

  日期：2014.7.7

  Hydrogenation of pyridine to piperidine catalyzed by [1,2,4-(Me3C)(3)C5H2](2)CeH, abbreviated as Cp'2CeH or [Ce]'-H, is reported. The reaction proceeds from Cp'Ce-2(2-pyridyl), isolated from the reaction of pyridine with Cp(')2CeH, to Cp'Ce-2(4,5,6-trihydropyridyl), and then to Cp'Ce-2(piperidyl). The cycle is completed by the addition of pyridine, which generates Cp'Ce-2(2-pyridyl) and piperidine. The net reaction depends on the partial pressure of H-2 and temperature. The dependence of the rate on the H-2 pressure is associated with the formation of Cp'2CeH, which increases the rate of the first and/or second additions of H-2 but does not influence the rate of the third addition. Density functional theory calculations of several possible pathways are consistent with three steps, each of which are composed of two elementary reactions, (i) heterolytic activation of H-2 with a reasonably high energy,Delta G double dagger = 20.5 kcal mol(-1), on Cp'Ce-2(2-pyridyl), leading to Cp'2CeH(6-hydropyridyl), followed by an intramolecular hydride transfer with a lower activation energy, (ii) intermolecular addition of Cp'2CeH to the C-4=C-5 bond, followed by hydrogenolysis, giving Cp'Ce-2(4,5,6-trihydropyridyl) and regenerating Cp'2CeH, and (iii) a similar hydrogenation/hydrogenolysis sequence, yielding Cp'Ce-2(piperidyl). The calculations reveal that step ii can only occur in the presence of Cp'2CeH and that alternative intramolecular steps have considerably higher activation energies. The key point that emerges from these experimental and computational studies is that step ii involves two Cp'Ce-2 fragments, one to bind the 6-hydropyridyl ligand and the other to add to the C-4=C-6 double bond. In the presence of 112, this second step is intermolecular and catalytic. The cycle is completed by reaction with pyridine to yield Cp'Ce-2(2-pyridyl) and piperidine. The structures of Cp'2CeX, where X = 2-pyridyl, 4,5,6-trihydropyridyl, and piperidyl, are fluxional, as shown by variable-temperature H-1 NMR spectroscopy.