Der Herr der Ringe: ein octamerer Lanthan-Pyrazolonat-Cluster

Xu, Jide; Raymond, Kenneth N.

doi:10.1002/1521-3757(20000804)112:15<2857::aid-ange2857>3.0.co;2-2

Cited by 31 publications

(2 citation statements)

References 34 publications

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“…As lanthanide ions have variable and high coordination numbers as well as poor stereochemical preferences,10 the construction of high‐nuclearity lanthanide wheels is more difficult than the construction of their TM analogues. In comparison with a number of TM wheels such as [Mo 176 ],2a [Mn 84 ],3a [Ni 24 ],4a [Fe 18 ],5a [Cr 10 ],6 [Co 12 ],7 [Cu 10 ],8a [Ti 8 ],11a and [V 8 ],11b only a few lanthanide wheels such as [Ln 8 ],9a,b [Ln 10 ],9c,d [Ln 12 ],9e,f and [Ln 15 ] have been made 9e–g…”

Section: Methodsmentioning

confidence: 99%

“…Compared with TM wheels, which are formed by TM ions and organic ligands,3–8 Ln wheels comprise not only organic ligands but also sharing Ln ions 9. In [Ln 8 ]/[Ln 10 ] wheels,9a–d the Ln ions are linked by OC 2 H 4 OMe ligands to form an 8/10 ring in which the center is empty. In [Ln 12 ]/[Ln 15 ] wheels,9e–g four/five {Ln 4 } cores share Ln vertices to form a 4 /5 ring around 1 or 2 halide ions in their central cavity.…”

Section: Methodsmentioning

confidence: 99%

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Lanthanide–Transition‐Metal Sandwich Framework Comprising {Cu₃} Cluster Pillars and Layered Networks of {Er₃₆} Wheels

et al. 2005

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Synergistic coordination between isonicotinate (ina) and 1,2‐benzenedicarboxylate (bdc) ligands under hydrothermal conditions results in the formation of two new coordination polymers, [Er7(μ3‐O)(μ3‐OH)6(bdc)3](ina)9[Cu3X4] (X=Cl, Br). Wheel‐shaped [Er36(μ3‐OH)30(μ3‐O)6(bdc)6]54+ ions form a 2D network (see picture), which is further pillared by [Cu3X4(ina)6]4− to give a 3D framework.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Lanthanide–Transition‐Metal Sandwich Framework Comprising {Cu₃} Cluster Pillars and Layered Networks of {Er₃₆} Wheels

et al. 2005

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Combinatorial Libraries of Metal-Ligand Assemblies with an Encapsulated Guest Molecule

et al. 2001

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Remarkable self-assembled polyhedral structures of high symmetry are found in nature. In some cases, subunits are interchangeable and assemble in mixtures of different components to form a structure with higher functionality and complexity. For example, the multicatalytic protease complex in the archaebacterium Thermoplasma acidophilum consists of 14 identical protein subunits assembled in a cylindrical structure with D 7 symmetry, [1] whereas the proteasome in a higher organism, the yeast Saccharomyces cerevisiae, is made of pairs of seven different protein subunits assembled in a structure with C 7 symmetry. [2] A number of synthetic coordination clusters of various sizes, stoichiometries, and symmetries has recently been described and reviewed. [3±5] We have shown that careful consideration of the geometric requirements of a particular symmetry and stoichiometry for a cluster leads to the controlled formation of M 4 L 4 (T), [6] M 4 L 6 (S 4 and T), [7,8] M 6 L 6 (D 3 ), [9] M 6 L 8 (O), and M 8 L 8 (D 4d ) [10] assemblies (with point symmetry noted). By combination of different subunits out of a pool of available ligands and metals, a large array of different assemblies (a library) can be obtained. Here we report the formation of libraries of tetrahedral M 4 L 6 complexes (Scheme 1) and describe the synthesis and character-Scheme 1. A schematic representation of the generation of a supramolecular library consisting of 152 496 possible tetrahedral M 4 L 6 assemblies made from 10 different components with homoconfigurational metal centers.

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Highly Reactive SmII Macrocyclic Clusters: Precursors to N2 Reduction

Mani¹,

Gambarotta²,

Yap³

2001

Angew. Chem.

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Divalent samarium complexes have been prepared with a wide variety of ligand systems, [1] but the extreme level of reactivity and the uniqueness of transformations displayed by the samarocene derivatives [2] was never reproduced. To date, the Sm II polypyrrolide derivatives [3] are the only systems which share with decamethylsamarocene [4] the ability to react with an exceedingly inert molecule such as dinitrogen. Unlike samarocene, however, these species may perform four-electron reduction of dinitrogen, thus indicating that their reducing power is particularly strong. Particularly versatile with this respect are divalent samarium complexes of dipyrrolide dianions, [5] which are reminiscent of the ansametallocene ligand systems. So far these species have led to three novel dinitrogen complexes. [6, 7] However, attempts to isolate the presumably highly reactive divalent precursors facilitates the formation of a peroxide species with molecular oxygen. The hydride transfer from the aluminum alkoxide of hydrotalcite is effected by the neighboring peroxide on the nickel atom. Hydrotalcites are homogeneous mixtures of heterobimetallic composition having a periodic composition of M II and M III ions. The cationic order of cat. A as revealed by IR studies suggests that the presence of one aluminum atom for every two nickel atoms substituted alternately in the hydrotalcite provides the optimum use of nickel in cat. A, better than is possible with the other compositions, and is thus responsible for the display of higher activity.In conclusion, Ni-Al hydrotalcite efficiently oxidizes a wide range of alcohols, such as allylic and benzylic, and a-ketols to the corresponding carbonyl compounds under mild reaction conditions by employing molecular oxygen as the stoichiometric oxidant. This process is not only economically viable but also applicable to large-scale reactions. Moreover, the high yields of oxidized products can be obtained in heterogeneous catalysis using hydrotalcites as catalysts. Experimental SectionVarious catalysts with varied composition of Ni-Al hydrotalcites (Ni:Al 2:1 (cat. A), 2.5:1, 3:1) were prepared by coprecipitation employing NaOH/ Na 2 CO 3 as described in the literature. [12a] Catalyst A was rehydrated according to our previous report [11b] and calcined at 450 8C in a flow of air. Ni-Al hydrotalcite (Ni:Al 2:1, cat. B) was prepared by coprecipitation using ammonia solution. [12b] The samples of nickel impregnated on galumina (2, 5, and 10 %) were prepared by adding the required amounts of Ni(NO 3 ) 2´6 H 2 O in water to g-alumina and stirring occasionally while heating on a water bath till complete evaporation of water had occurred. The residue was dried in an oven at 110 8C for 16 h.Typical oxidation procedure: Oxygen was bubbled at atmospheric pressure through a reaction mixture containing p-nitrobenzyl alcohol (2 mmol) and catalyst (0.5 g) in toluene (10 mL) at 90 8C under stirring. The reaction was monitored by thin-layer chromatography and purified by column chromatography (hexane:eth...

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Der Herr der Ringe: ein octamerer Lanthan-Pyrazolonat-Cluster

Cited by 31 publications

References 34 publications

Lanthanide–Transition‐Metal Sandwich Framework Comprising {Cu₃} Cluster Pillars and Layered Networks of {Er₃₆} Wheels

Lanthanide–Transition‐Metal Sandwich Framework Comprising {Cu₃} Cluster Pillars and Layered Networks of {Er₃₆} Wheels

Combinatorial Libraries of Metal-Ligand Assemblies with an Encapsulated Guest Molecule

Highly Reactive SmII Macrocyclic Clusters: Precursors to N2 Reduction

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Der Herr der Ringe: ein octamerer Lanthan-Pyrazolonat-Cluster

Cited by 31 publications

References 34 publications

Lanthanide–Transition‐Metal Sandwich Framework Comprising {Cu3} Cluster Pillars and Layered Networks of {Er36} Wheels

Lanthanide–Transition‐Metal Sandwich Framework Comprising {Cu3} Cluster Pillars and Layered Networks of {Er36} Wheels

Combinatorial Libraries of Metal-Ligand Assemblies with an Encapsulated Guest Molecule

Highly Reactive SmII Macrocyclic Clusters: Precursors to N2 Reduction

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Lanthanide–Transition‐Metal Sandwich Framework Comprising {Cu₃} Cluster Pillars and Layered Networks of {Er₃₆} Wheels

Lanthanide–Transition‐Metal Sandwich Framework Comprising {Cu₃} Cluster Pillars and Layered Networks of {Er₃₆} Wheels