Intrazeolite organometallics and coordination complexes: internal versus external confinement of metal guests

Ozin, Geoffrey A.; Gil, Caroline J.

doi:10.1021/cr00098a006

Cited by 217 publications

(91 citation statements)

References 26 publications

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“…Because of these future prospects of applications in heterogeneous catalysis confinement of organometallics in the voids of zeolite host frameworks has gained considerable attention over the last years. [1][2][3][4][5] For a fundamental understanding of these systems knowledge of the interaction between the organometallic guest molecules and the zeolite host framework is desired. We use the relatively simple organometallic ferrocene, Fe͑C 5 H 5 ) 2 , adsorbed in the supercages of NaY zeolite, Na x (AlO 2 ) x (SiO 2 ) 192Ϫx , as a model system.…”

Section: Introductionmentioning

confidence: 99%

“…One remarkable effect found is that unlike pure ferrocene in the solid or gas-phase state, ferrocene in zeolite Y oxidizes quite easily. 1,4 To fully understand the interaction between the ferrocene molecules and the zeolite framework, knowledge of the location of ferrocene in the zeolite host is required. In the present study we determine the location of ferrocene in NaY zeolite by means of powder x-ray and neutron diffraction at a temperature Tϭ10 K and Tϭ1.5 K, respectively, for loadings of one and two ferrocene molecules per supercage.…”

Section: Introductionmentioning

confidence: 99%

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Localization of ferrocene in NaY zeolite by powder x-ray and neutron diffraction

Kemner

Overweg

Eijck

et al. 2002

The Journal of Chemical Physics

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We study the inclusion of the metallocene ferrocene Fe͑C 5 H 5 ) 2 molecules in the supercages of NaY zeolite. To find the exact location of the ferrocene molecules within the supercages we perform neutron and powder x-ray diffraction on bare NaY zeolite, and on NaY zeolite loaded with one or two ferrocene molecules per supercage. Using the complementary properties of both techniques we show that the ferrocene molecules are located just above a line joining two neighboring sodium ions at the SII positions in the zeolite supercage. The C 5 H 5 rings are oriented towards the sodium ions in an ordered manner. This structure is confirmed by quantum chemistry calculations. The geometry of the ferrocene molecules barely changes, indicating that the increased reactivity of ferrocene upon adsorption in a zeolite is thus a result of the position of the molecules. The main interactions responsible for this position are Coulombic attraction and hydrogen bonding. The inclusion of ferrocene in a Y-type zeolite provides a homogeneous distribution of iron throughout the zeolite at well-defined locations.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Localization of ferrocene in NaY zeolite by powder x-ray and neutron diffraction

Kemner

Overweg

Eijck

et al. 2002

The Journal of Chemical Physics

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“…Immobilization of UMCs into porous hosts has been attempted with zeolites, polymeric matrices, and clays through ion exchange, impregnation, and isomorphous substitution. [1,2] However, in these cases, the isolation and uniformity of the UMCs is not sufficient and the environment around the UMCs is not clear. Completely isolated and uniform catalytic centers can be realized if the UMCs are directly incorporated into channel walls of crystalline microporous coordination polymers constructed from transition-metal ions and organic bridging ligands.…”

mentioning

confidence: 99%

“…Consequently, the porous structure was maintained with only slight structure distortions up to 573 K. A detailed study of these structural torsions is underway. We also investigated the use of Co II 2 ] n (3) were also synthesized by a similar synthetic procedure to 1. Figure 4 shows the XRPD patterns of 2 and 3.…”

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confidence: 99%

Immobilization of a Metallo Schiff Base into a Microporous Coordination Polymer

et al. 2004

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Immobilization of coordinatively unsaturated metal centers (UMCs) into porous frameworks is a very attractive area of research because the porous framework can induce regioselectivity or shape/size selectivity by creating an appropriate environment around the metal center in the restricted available space. Furthermore, porous frameworks can stabilize the catalytic center by efficiently isolating the sites in a manner similar to the peptide architecture of enzymes in biological systems. Immobilization of UMCs into porous hosts has been attempted with zeolites, polymeric matrices, and clays through ion exchange, impregnation, and isomorphous substitution. [1,2] However, in these cases, the isolation and uniformity of the UMCs is not sufficient and the environment around the UMCs is not clear. Completely isolated and uniform catalytic centers can be realized if the UMCs are directly incorporated into channel walls of crystalline microporous coordination polymers constructed from transition-metal ions and organic bridging ligands. [3,4] Such a situation would lead to novel highly selective catalysts and sensors.In spite of the importance, the incorporation of UMCs into porous frameworks is still rare because of difficulties associated with the formation of UMCs in channel walls by a self-assembly process.[5-7] Therefore, we focused on the establishment of a rational synthetic method to immobilize various UMCs in the pore walls of microporous coordination polymers. Ligands based on metallo Schiff bases are known to be useful for the generation of supramolecular systems for homogeneous catalyses and so might be suitable for incorporation into infinite porous frameworks for applications in heterogeneous catalyses and sensors. [8,9] Here, we report a novel three-dimensional (3D) microporous coordination framework obtained from Schiff base type ligands prepared from the reaction of N,N'-phenylenebis (salicylideneimine)

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“…The immobilization of transition-metal catalysts on solid supports has been the focus of many research efforts. [2][3][4][5][6] Key challenges in the design of these catalysts include (i) control over the species that is actually immobilized, and (ii) sufficient stability against deactivation and leaching. The novel mesoporous MCM-41 hosts are prepared in liquid crystalline phases where combinations of amphiphile-metal0x0 systems order in channel or layer structures.…”

mentioning

confidence: 99%

Reactivity of a trimethylstannyl molybdenum complex in mesoporous MCM-41

Huber¹,

Möller²,

Bein³

1994

J. Chem. Soc., Chem. Commun.

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A highly thermostable tin-molybdenum complex is encapsulated into the hexagonal mesoporous channel host MCM-41 and thermally transformed into supported metal clusters.The recent discovery of a new class of ordered mesoporous materials' with channel diameters between about 20 and 100 8, has opened up new opportunities for the design of hybrid catalysts. The immobilization of transition-metal catalysts on solid supports has been the focus of many research efforts.2-6 Key challenges in the design of these catalysts include (i) control over the species that is actually immobilized, and (ii) sufficient stability against deactivation and leaching. The novel mesoporous MCM-41 hosts are prepared in liquid crystalline phases where combinations of amphiphile-metal0x0 systems order in channel or layer structures. In the case of aluminosiiicate MCM-41, the pore system obtained after calcination presents well-defined hexagonal walls with terminal hydroxyl groups at 3745 cm-1 (in vacuum). Surface reactions with organometallic compounds should therefore produce well-defined species, in contrast to the situation on some amorphous supports. The enormous pore sizes of the MCM-41 family offer new opportunities for the encapsulation of large catalyst species and for the catalytic conversion of substrates much larger than in common zeolites.We have recently developed a concept for stabilizing low-valent transition-metal moieties [such as CI2(THF)Ge-M O ( C O )~~ or Me3SnMn(CO)S]g in large-pore zeolites, by using bimetallic complexes where the second, oxophilic main-group element serves to attach the complex to the internal zeolite cage surface. This communication describes

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Intrazeolite organometallics and coordination complexes: internal versus external confinement of metal guests

Cited by 217 publications

References 26 publications

Localization of ferrocene in NaY zeolite by powder x-ray and neutron diffraction

Localization of ferrocene in NaY zeolite by powder x-ray and neutron diffraction

Immobilization of a Metallo Schiff Base into a Microporous Coordination Polymer

Reactivity of a trimethylstannyl molybdenum complex in mesoporous MCM-41

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