http://www1.udel.edu/chem/polenova/PDF/Polyoxometalates/POMs_Catalysis_NMR_ChemRev1998.pdf

Catalysis by Heteropoly Acids and Multicomponent Polyoxometalates in Liquid-Phase Reactions

Electrochemical Properties of Polyoxometalates as Electrocatalysts.

Polyoxometalates (POMs) are discrete anionic metaloxygen clusters which can be regarded as soluble oxide fragments. They exhibit a great diversity of sizes, nuclearities, and shapes. They are built from the connection of {MOx} polyhedra, M being a d-block element in high oxidation state, usually VIV,V, MoVI, or WVI.1 While these species have been known for almost two centuries, they still attract much interest partly based on their large domains of applications. They play a great role in various areas ranging from catalysis,2 medicine,3 electrochemistry,4 photochromism,5 to magnetism.6 This palette of applications is intrinsically due to the combination of their added value properties (redox properties, large sizes, high negative charges, nucleophilicity...). Parallel to this domain, the organic-inorganic hybrids area has followed a similar expansion during the last 10 years. The concept of organic-inorganic hybrid materials * To whom correspondence should be addressed. E-mail: dolbecq@ chimie.uvsq.fr. Chem. Rev. 2010, 110, 6009–6048 6009

Hybrid Organic−Inorganic Polyoxometalate Compounds: From Structural Diversity to Applications

Homogeneous catalysis by transition metal oxygen anion clusters

Traditional homogeneous water oxidation catalysts are plagued by instability under the reaction conditions. We report that the complex [Co4(H2O)2(PW9O34)2]10-, comprising a Co4O4 core stabilized by oxidatively resistant polytungstate ligands, is a hydrolytically and oxidatively stable homogeneous water oxidation catalyst that self-assembles in water from salts of earth-abundant elements (Co, W, and P). With [Ru(bpy)3]3+ (bpy is 2,2'-bipyridine) as the oxidant, we observe catalytic turnover frequencies for O2 production > or = 5 s(-1) at pH = 8. The rate's pH sensitivity reflects the pH dependence of the four-electron O2-H2O couple. Extensive spectroscopic, electrochemical, and inhibition studies firmly indicate that [Co4(H2O)2(PW9O34)2]10- is stable under catalytic turnover conditions: Neither hydrated cobalt ions nor cobalt hydroxide/oxide particles form in situ.

https://science.sciencemag.org/content/sci/328/5976/342.full.pdf

A Fast Soluble Carbon-Free Molecular Water Oxidation Catalyst Based on Abundant Metals

The P2Co4(H2O)2W18O6810– anion contains four edge-linked coIIO6 octahedra with coplanar cobalt atoms, in addition to two fragments of the Keggin structure.

18-Tungstotetracobalto(II)diphosphate and related anions: a novel structural class of heteropolyanions

Triheteropolyanions containing copper(II), manganese(II), or manganese(III)

Heteropolyanions [WM3(H2O)2(XW9O34)2]12–(X = M = Zn or CoII) form on ageing concentrated solutions of sodium salts of the well known polyanions [Zn(H2O)(ZnW11O39)]8– and [CoII(H2O)(CoIIW11O39)]8–. Their high-yield syntheses are reported. An X-ray crystallographic study of Na12[WZn3(H2O)2(ZnW9O34)2]·46H2O [Space group p21/c, a= 13.027(4), b= 17.788(5), c= 24.124(4)A, β= 118.94(2)°, Z= 2, R′= 0.051 for 3783 reflections] and its high-resolution 183W NMR spectrum (ten lines, one with half the intensity of the others) reveal that the polyanion is isotypical of the earlier described [M4(H2O)2(PW9O34)2]10– anions (M = Zn or CoII) and elucidate the puzzling analytical composition Zn5W19. However, the lower point-group symmetry C2 (instead of C2h) points to the existence of enantiomers. This anion and the homologous cobalt(II) anion are always obtained as racemic mixtures. Both parent anions transform into substitution derivatives by replacement of atoms in M positions (Two or three for Zn, two only for Co) by transition elements: derivatives of MnII or MnIII, FeII or FeIII, CoII, NiII, CuII, Zn, PdII, PtII and VIV are reported. The structures of D,L-Na12[WCu3(H2O)2(ZnW9O34)2]·48H2O and D,L-K12[WZnV2O2(ZnW9O34)2]·30H2O are also described and compared. Chemical features, comparative electronic UV–VIS spectra, and 183W NMR spectra of these series are discussed.

Chiral polytungstometalates [WM3(H2O)2(XW9O34)2]12–(X = M = Zn or CoII) and their M-substituted derivatives. Syntheses, chemical, structural and spectroscopic study of some D,L sodium and potassium salts

Preparation and characterization of iron(III)- and rhodium(III)-containing heteropolytungstates. Identification of novel oxo-bridged iron(III) dimers

The crystal structures of K10[Co4(H2O)2(PW9O34)2]·22H2O (1) and isomorphous K10[Zn4(H2O)2(AsW9O34)2]·23H2O (2) have been determined {Mo-Kα radiation, space group P21/n, Z= 2; (1)a= 15.794(2), b= 21.360(2), c= 12.312(1)A, β= 91.96°, R= 0.084 for 3 242 observed reflections [I 3σ(I)]; (2)a= 15.842(4), b= 21.327(5), c= 12.308(4)A, β= 92.42(4)°, R= 0.066 for 4 675 observed reflections [F 3σ(F)]}. The anions have crystallographic symmetry and non-crystallographic symmetry very close to 2/m(C2h). Each consists of two [XW9O34]9– moieties [α-B isomers; X = P (1) or As (2)] linked via four CoIIO6 or ZnO6 groups. Two Co or Zn atoms each carry a water ligand. The 183W n.m.r. spectra of the anions [Zn4(H2O)2(XW9O34)2]10–(X = P or As) confirm that the anions retain 2/m symmetry in aqueous solution. Homonuclear coupling constants between 183W atoms are 5.8–9.0 Hz for adjacent WO6 octahedra sharing edges, and 19.6–25.0 Hz for octahedra sharing corners.

X-Ray crystallographic and tungsten-183 nuclear magnetic resonance structural studies of the [M4(H2O)2(XW9O34)2]10– heteropolyanions (M = COII or Zn, X = P or As)

Gilbert F. Tourné

Papers

18-Tungstotetracobalto(II)diphosphate and related anions: a novel structural class of heteropolyanions

Triheteropolyanions containing copper(II), manganese(II), or manganese(III)

Chiral polytungstometalates [WM3(H2O)2(XW9O34)2]12–(X = M = Zn or CoII) and their M-substituted derivatives. Syntheses, chemical, structural and spectroscopic study of some D,L sodium and potassium salts

Preparation and characterization of iron(III)- and rhodium(III)-containing heteropolytungstates. Identification of novel oxo-bridged iron(III) dimers

X-Ray crystallographic and tungsten-183 nuclear magnetic resonance structural studies of the [M4(H2O)2(XW9O34)2]10– heteropolyanions (M = COII or Zn, X = P or As)