Noble Metal Polyoxometalate Research
featured in Platinum Metals Review

Platinum Metals Rev., 2014, 58, (1), 40

Pope, M. T.; Kortz, U. Encyclopedia of Inorganic and Bioinorganic Chemistry2012[Read Online]
The term polyoxometalate has been applied to polyoxoanions that are predominantly or entirely based on transition elements, in order to distinguish them from their main group relatives (borates, silicates, etc.) which display distinctly different structural and chemical features. Thus polyoxometalates (POMs) are typically water-soluble anions that adopt molecular structures, often of high symmetry, and which commonly incorporate 5–50 metal centers, although the current record is 368.

Diphosphates and Diphosphonates in Polyoxometalate Chemistry
Banerjee, A.; Bassil, B. S.; Röschenthaler, G.-V.; Kortz, U. Chem. Soc. Rev. 2012, 41, 7590-7604. [Read Online]
In the wide area of polyoxometalate (POM) chemistry, diphosphate/diphosphonate-based POMs represent a more recent area of study. However, in this short time it has emerged to become very dynamic, as shown by the wide variety of compounds reported. Ever since the discovery of the first polyoxotungstate framework constructed from diphosph(on)ate ligands, a widespread investigation on the preparative chemistry and properties of such compounds has followed. The main focus of such a study is based on factors such as the oxidation state of the metal, the effect of pH and temperature during synthesis, and the presence of different functional groups on the diphosphonate. In this review we discuss in detail all diphosphate/diphosphonate-based POMs, beginning with early developments, subsequent growth in interest, and finally focusing on the very latest developments.

Noble Metals in Polyoxometalates
Izarova, N. V.; Pope, M. T.; Kortz, U. Angew. Chem. Int. Ed.201251, 9492-9510. [Read Online]
Polyoxometalates containing noble metal ions, such as ruthenium, osmium, rhodium, palladium, platinum, silver and gold, are a struc- turally diverse class of compounds. They include both classical heteropolyanions (vanadates, molybdates, tungstates) in which noble metals are present as heteroatoms, as well as the recently discovered class of polyoxometalates with noble metal “addenda” atoms. The focus of this Review is on complexes that should, in principle, exist as discrete molecular species in solution, and which are therefore of interest for their reactivity, their future synthetic utility and potential applications, for example, in catalysis or nanoscience.

Divacant Polyoxotungstates: Reactivity of the gamma-Decatungstates [γ-XW10O36]8- (X = Si, Ge)
Bassil, B. S.; Kortz, U. Dalton Trans. 201140, 9649-9661. [Read Online]
The dilacunary, Keggin-based gamma-decatungstate ions [γ-XW10O36]8− (X = Si, Ge) {XW10} exhibit an exciting and versatile solution chemistry, which is probably unmatched by any other lacunary polytungstate. The reactivity of {XW10} in the presence, and even absence, of electrophiles, includes loss/gain of tungsten, isomerization, and dimerization. Ever since the syntheses and structures of {XW10} were reported, many research groups around the world have investigated the reactivity of these polyanions towards nucleophiles (mostly d-block metal ions) and different products with various shape, size and composition were obtained. Here we provide an overview of the state-of-the-art in this subarea of polyoxometalate chemistry, with a focus on synthetic and structural aspects.

Recent Advances in Lanthanide-Containing Polyoxotungstates
Bassil, B. S.; Kortz, U., Z. Anorg. Allg. Chem.2010, 636, 2222-2231. [Read Online]

The area of lanthanide-containing polyoxometalates has been a field of large interest for several years due to the interesting structural and physicochemical properties of such compounds. This chemistry is dominated by tungsten based POMs, as a large number of vacant (lacunary) polytungstate precursors is known (as opposed to vanadium or molybdenum based POMs). The main subclasses in this field are lanthanide-containing iso– and hetero-polytungstates. The number of examples in the latter class is significantly larger than the former, probably because more lacunary hetero– than iso-polytungstates are known. Here we report on recent examples of lanthanide-containing iso– and hetero-polytungstates with a focus on synthetic and in particular structural aspects. The compounds discussed include discrete molecular species as well as 1-, 2- and 3-D solid-state assemblies.

Polyoxometalates: Fascinating Structures, Unique Magnetic Properties
Kortz, U.; Müller, A.; van Slageren, J.; Schnack, J.; Dalal, N. S.; Dressel, M. Coord. Chem. Rev.2009, 253, 2315-2327. [Read Online]

We report on several discrete molecular transition metal- and lanthanide-containing polyoxo-tungstates and -molybdates with a focus on their magnetic properties. The polyanions discussed here all contain 3d paramagnetic centers and are mostly of the spherical {Mo132} Keplerate type, the cyclic {P8W48} type, the dimeric {XIII2W18} (X = As, Sb) type, and the dimeric, fused {Si2W18} type. The number of incorporated magnetic ions in the structures described here ranges from 3 to 30.