Journal ArticleDOI
Cation-Directed Structure Changes in Polyoxometalate Chemistry. Equilibria between Isomers of Bis(9-tungstophosphatodioxouranate(VI)) Complexes
Kee-Chan Kim,Michael T. Pope +1 more
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TLDR
The first polyoxometalates incorporating uranyl hetero groups have been synthesized by reaction of Na9(A-PW9O34) with UO2(NO3)2 as discussed by the authors.Abstract:
The first examples of polyoxometalates incorporating uranyl hetero groups have been synthesized by reaction of Na9(A-PW9O34) with UO2(NO3)2. Sodium, ammonium, and potassium salts of (M2(UO2)2- (PW9O34)2) 12- (M ) Na, NH4, K) were characterized by P and W NMR spectroscopy and single-crystal structural analysis. The sodium salt (1) contains an anion of Ci symmetry in which two PW9O34 groups sandwich two UO2 2+ and two Na + cations. The uranium atoms have pentagonal-bipyramidal coordination, achieved by three equatorial bonds to one PW9O34 and two bonds to the other. The sodium cations have approximate tetrahedral coordination geometry. Single-line P and five-line W NMR spectra confirm that the anion structure is maintained in solutions containing excess Na + . The ammonium and potassium salts contain anions in which the UO2 2+ cations (pentagonal bipyramids) are unsymmetrically sandwiched between the PW9O34 groups, as are two closely associated cations, one internal and one external. In solution both, salts give two-line P and nine-line W NMR spectra that are consistent with the solid-state structures. Solution equilibria are rapidly established between the two structure types and are dependent upon the concentrations and identities of the cations. Based on integrated P NMR spectra, the equilibrium constants for (Na2(UO2)2(PW9O34)2) 12- + 2M + T (M2(UO2)2(PW9O34)2) 12- + 2Na + are 128 ( 12 (M ) K + ) and 1.8 ( 0.8 (M ) NH4 + ). The requirement of the second cation in order to satisfy the mass-action expression for Keq, coupled with a W NMR spectrum that implies Cs symmetry, demonstrates that the external ion-paired cation undergoes rapid exchange between several surface sites of the heteropolyanion. Solutions of 1 are stable at pH 7 in the presence of excess sodium cations, and the anion is transferable into toluene by phase-transfer techniques. Addition of calcium ions to solutions of 1 generates a new one-line P NMR spectrum of a Ca derivative which is assumed to be isostructural with 1.read more
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Polyoxometalate clusters, nanostructures and materials: From self assembly to designer materials and devices
TL;DR: In this critical review the synthetic and design approaches to the many polyoxometalate cluster types are presented encompassing all the sub-types of polyxometalates including, isopolyoxometAlates, heteropolyoxometricalates, and reduced molybdenum blue systems.
Journal ArticleDOI
Controlled Assembly of Polyoxometalate Chains from Lacunary Building Blocks and Lanthanide-Cation Linkers Supported in part by the National Science Foundation (CHE9727417) and Georgetown University.
Journal ArticleDOI
Three Mechanisms in One Material: Uranium Capture by a Polyoxometalate–Organic Framework through Combined Complexation, Chemical Reduction, and Photocatalytic Reduction
Hailong Zhang,Wei Liu,Wei Liu,Ao Li,Duo Zhang,Xiaoyan Li,Fuwan Zhai,Lanhua Chen,Long Chen,Yanlong Wang,Shuao Wang +10 more
TL;DR: SCU-19 is currently the only uranium sorbent material with three distinct sorption mechanisms, as further demonstrated by X-ray photoelectron spectroscopy (XPS) andX-ray absorption near edge structure (XANES) analysis.
Journal ArticleDOI
Clusters of Actinides with Oxide, Peroxide, or Hydroxide Bridges
Jie Qiu,Peter C. Burns +1 more
Journal ArticleDOI
A New Type of Heteropolyoxometalates formed from Lacunary Polyoxotungstate Ions and Europium or Yttrium Cations.
Robertha C. Howell,Frances G. Perez,Sanhya Jain,William DeW. Horrocks,Arnold L. Rheingold,Lynn C. Francesconi +5 more
TL;DR: In this article, four lacunary PW9 O349- ions (blue polyhedra) are held together by eight MIII (M = Y, Eu) ions and seven W atoms that form a [M8 W7 O30 ]6+ network (center) in the novel heteropolyoxometalates.
References
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Journal ArticleDOI
Heteropolytungstate complexes of the lanthanide elements. Part I. Preparation and reactions
R. D. Peacock,T. J. R. Weakley +1 more
TL;DR: In this paper, the formulae of the previously reported 8-tungstocerates are revised, and the mode of co-coordination of Lanthanide cations is discussed.
Journal ArticleDOI
Heteropolyanions of the types M3(W9PO34)212- and MM'M"(W9PO34)212-: novel coordination of nitrate and nitrite
Journal ArticleDOI
New chemistry for heteropolyanions in anhydrous nonpolar solvents: coordinative unsaturation of surface atoms ― polyanion oxygen carriers
Journal Article
Heteropolyanions of the types M3(W9PO34)212−: novel coordination of nitrate and nitrite
Journal ArticleDOI
Crystal chemical studies of the 5f-series of elements. XXV. The crystal structure of sodium uranyl acetate
TL;DR: In this paper, the positions of all atoms were deduced from precisely measured x-ray-diffraction intensities, and a revised bond length versus bond strength curve for U/sup VI/-O bonds was presented.
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