Selective CH Bond Activation by a Supramolecular Host–Guest Assembly

Leung, Dennis; Fiedler, Dorothea; Bergman, Robert G.; Raymond, Kenneth N.

doi:10.1002/anie.200352772

Cited by 191 publications

(123 citation statements)

References 29 publications

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“…34 (12) was prepared by addition of ethylene to a solution of 10 in CH 2 Cl 2 and is stable in aqueous solution, since the ethylene ligand is more strongly coordinating than water to the iridium center. As a consequence of this stability, 12 has decreased reactivity compared to neutral triflate species.…”

Section: Encapsulated Transition Metal Reactivitymentioning

confidence: 99%

Selective Molecular Recognition, C−H Bond Activation, and Catalysis in Nanoscale Reaction Vessels

et al. 2004

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Supramolecular chemistry represents a way to mimic enzyme reactivity by using specially designed container molecules. We have shown that a chiral self-assembled M4L6 supramolecular tetrahedron can encapsulate a variety of cationic guests with varying degrees of stereoselectivity. Reactive iridium guests can be encapsulated, and the C-H bond activation of aldehydes occurs with the host cavity controlling the ability of substrates to interact with the metal center based upon size and shape. In addition, the host container can act as a catalyst by itself. By restricting reaction space and preorganizing the substrates into reactive conformations, it accelerates the sigmatropic rearrangement of enammonium cations.

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Section: Encapsulated Transition Metal Reactivitymentioning

confidence: 99%

Selective Molecular Recognition, C−H Bond Activation, and Catalysis in Nanoscale Reaction Vessels

et al. 2004

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“…70 A possible geometry of such a ligand is the triangle (C 3 -symmetry), which in combination with appropriate metal ions can form a tetrahedron. 71,72 Our approach was to use triangular ligands with catechol corners and octahedrally coordinating metal ions to obtain tetrahedra. [73][74][75][76][77] In the investigations the problem was addressed, if the ligands have to be rigid and highly preorganized, or if flexible ligands also can be manipulated in such a way that they lead to the desired oligonuclear structure and not only to mononuclear complexes (Fig.…”

Section: Tripodal Triscatechol Ligands For the Formation Of Mononuclementioning

confidence: 99%

Symmetry Driven Self-Assembly of Metallo-Supramolecular Architectures

Albrecht¹,

Fröhlich²

2007

Bulletin of the Chemical Society of Japan

111

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The self-assembly of well-defined metallosupramolecular aggregates highly depends on the symmetry of the ligands as well as of the metals. Approaches in which symmetry considerations allow the stepwise-''hierarchical''-assembly of helicate-type complexes from very simple catechol derivatives are described. In addition helicates and meso-helicates are stereoselectively obtained by the use of linear ligands possessing the relevant symmetry element for the formation of either diastereomer (even-odd principle). In case of helicates, this allows the preparation of enantiomerically pure complexes. Finally, the self-assembly of tetrahedral M 4 L 4 complexes is described using either constrained flexible or highly predisposed rigid ligands.

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“…41,42 While the 12-overall charge of 1 imparts water solubility, the naphthalene walls of the assembly provide a hydrophobic interior cavity, able to encapsulate guests, which is isolated from the bulk aqueous solution. A wide variety of small neutral and monocationic guests including aliphatic hydrocarbons, 43 protonated guests, 44 simple organic cations, 45 and reactive organometallic complexes [46][47][48] have been encapsulated in 1. Analysis of the mechanism for guest exchange revealed that 1 stays intact during the guest exchange process and that the apertures along the 3-fold axis of 1 dilate to allow for guest ingress and egress.…”

Section: Introductionmentioning

confidence: 99%

“…45 Using 1 to mediate the reactivity of organometallic guests, both stoichiometric and catalytic reactions have been carried out inside of 1 with both size-and stereo-selectivity. [46][47][48] Furthermore, 1 has been used as a catalyst for the sigmatropic rearrangement of enammonium cations. 49 We have recently reported the ability of 1 to greatly favor the protonated form of encapsulated substrates such as amines, with pK a shifts of up to 4.5 pK a units, and have exploited this stabilization for the catalysis of orthoformates and acetals in basic solution.…”

Section: Introductionmentioning

confidence: 99%

Spin Equilibria in Monomeric Manganocenes: Solid-State Magnetic and EXAFS Studies

et al. 2009

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A water-soluble self-assembled supramolecular host molecule catalyzes the hydrolysis of orthoformates in basic solution. Comparison of the rate constants of the catalyzed and uncatalyzed reactions for hydrolysis displays rate accelerations of up to 3900 for tri-n-propyl orthoformate. Kinetic analysis shows that the mechanism of hydrolysis with the supramolecular host obeys the Michaelis-Menten model.Mechanistic studies, including 13 C-labeling experiments, revealed that the resting state of the catalytic system is the neutral substrate encapsulated in the host. Activation parameters for the k cat step of the reaction revealed that upon encapsulation in the assembly, the entropy of activation becomes more negative in contrast to the uncatalyzed reaction. Furthermore, solvent isotope effects reveal a normal k(H 2 O)/k(D 2 O) = 1.6, confirming that proton transfer is occurring in the transition state and is rate limiting in the catalyzed reaction. In comparison to the uncatalyzed reaction, which operates by an A-1 mechanism in which the decomposition of the protonated substrate is rate limiting, the encapsulated reaction proceeds through an A-S E 2 mechanism in which proton transfer from protonated water to the substrate is rate limiting.

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Selective CH Bond Activation by a Supramolecular Host–Guest Assembly

Cited by 191 publications

References 29 publications

Selective Molecular Recognition, C−H Bond Activation, and Catalysis in Nanoscale Reaction Vessels

Selective Molecular Recognition, C−H Bond Activation, and Catalysis in Nanoscale Reaction Vessels

Symmetry Driven Self-Assembly of Metallo-Supramolecular Architectures

Spin Equilibria in Monomeric Manganocenes: Solid-State Magnetic and EXAFS Studies

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