Catalysis in a Porous Molecular Capsule: Activation by Regulated Access to Sixty Metal Centers Spanning a Truncated Icosahedron

Kopilevich S, Gil A, Garcia-Rates M, Bonet-Avalos J, Bo C, Müller A, Weinstock IA (2012)
Journal of the American Chemical Society 134(31): 13082-13088.

Zeitschriftenaufsatz | Veröffentlicht | Englisch
 
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Abstract / Bemerkung
The 30 cationic {(Mo2O4)-O-V(acetate)}(+) units linking 12 negatively charged pentagonal "ligands," {(Mo-VI)-(Mo5O21)-O-VI(H2O)(6)}(6-) of the porous metal-oxide capsule, [{(Mo6O21)-O-VI(H2O)(6)}(12){(Mo2O4)-O-V(acetate)}(30)](42-) provide active sites for catalytic transformations of organic "guests". This is demonstrated using a well-behaved model reaction, the fully reversible cleavage and formation of methyl tert-butyl ether (MTBE) under mild conditions in water. Five independent lines of evidence demonstrate that reactions of the MTBE guests occur in the ca. 6 x 10(3) angstrom(3) interior of the spherical capsule. The Mo atoms of the {(Mo2O4)-O-V(acetate)}(+) linkers-spanning an ca. 3-nm truncated icosahedron-are sterically accessible to substrate, and controlled removal of their internally bound acetate ligands generates catalytically active {(Mo2O4)-O-V(H2O)(2)}(2+) units with labile water ligands, and Lewis- and Bronsted-acid properties. The activity of these units is demonstrating by kinetic data that reveal a first-order dependence of MTBE cleavage rates on the number of acetate-free {(Mo2O4)-O-V(H2O)(2)}(2+) linkers. DFT calculations point to a pathway involving both Mo(V) centers, and the intermediacy of isobutene in both forward and reverse reactions. A plausible catalytic cycle satisfying microscopic reversibility is supported by activation parameters for MTBE cleavage, deuterium and oxygen-18 labeling studies, and by reactions of deliberately added isobutene and of a water-soluble isobutene analog. More generally, pore-restricted encapsulation, ligand-regulated access to multiple structurally integral metal-centers, and options for modifying the microenvironment within this new type of nanoreactor, suggest numerous additional transformations of organic substrates by this and related molybdenum-oxide based capsules.
Erscheinungsjahr
2012
Zeitschriftentitel
Journal of the American Chemical Society
Band
134
Ausgabe
31
Seite(n)
13082-13088
ISSN
0002-7863
eISSN
1520-5126
Page URI
https://pub.uni-bielefeld.de/record/2530403

Zitieren

Kopilevich S, Gil A, Garcia-Rates M, et al. Catalysis in a Porous Molecular Capsule: Activation by Regulated Access to Sixty Metal Centers Spanning a Truncated Icosahedron. Journal of the American Chemical Society. 2012;134(31):13082-13088.
Kopilevich, S., Gil, A., Garcia-Rates, M., Bonet-Avalos, J., Bo, C., Müller, A., & Weinstock, I. A. (2012). Catalysis in a Porous Molecular Capsule: Activation by Regulated Access to Sixty Metal Centers Spanning a Truncated Icosahedron. Journal of the American Chemical Society, 134(31), 13082-13088. doi:10.1021/ja304513t
Kopilevich, S., Gil, A., Garcia-Rates, M., Bonet-Avalos, J., Bo, C., Müller, A., and Weinstock, I. A. (2012). Catalysis in a Porous Molecular Capsule: Activation by Regulated Access to Sixty Metal Centers Spanning a Truncated Icosahedron. Journal of the American Chemical Society 134, 13082-13088.
Kopilevich, S., et al., 2012. Catalysis in a Porous Molecular Capsule: Activation by Regulated Access to Sixty Metal Centers Spanning a Truncated Icosahedron. Journal of the American Chemical Society, 134(31), p 13082-13088.
S. Kopilevich, et al., “Catalysis in a Porous Molecular Capsule: Activation by Regulated Access to Sixty Metal Centers Spanning a Truncated Icosahedron”, Journal of the American Chemical Society, vol. 134, 2012, pp. 13082-13088.
Kopilevich, S., Gil, A., Garcia-Rates, M., Bonet-Avalos, J., Bo, C., Müller, A., Weinstock, I.A.: Catalysis in a Porous Molecular Capsule: Activation by Regulated Access to Sixty Metal Centers Spanning a Truncated Icosahedron. Journal of the American Chemical Society. 134, 13082-13088 (2012).
Kopilevich, Sivil, Gil, Adria, Garcia-Rates, Miguel, Bonet-Avalos, Josep, Bo, Caries, Müller, Achim, and Weinstock, Ira A. “Catalysis in a Porous Molecular Capsule: Activation by Regulated Access to Sixty Metal Centers Spanning a Truncated Icosahedron”. Journal of the American Chemical Society 134.31 (2012): 13082-13088.

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