Frank Peters

Organizational Forms of Matter: An Inorganic Super Fullerene and Keplerate Based on Molybdenum Oxide

Plato and Kepler would have been pleased. Despite the large number of atoms present the cluster anion 1 resembles an icosahedral-type structure. This represents definitively an unprecedented event in chemistry! The structure is made up of 12 {Mo11 } fragments such that the fivefold symmetry axes are retained in the resulting spherical object. As an inscribed icosahedron can be recognized in the spherical shell of 1 (see picture), similarities with Keplers famous shell model of the cosmos can be seen.

Materielle Organisationsformen: ein anorganisches Superfulleren und Keplerat auf Molybdänsauerstoffbasis

Da hatten wohl auch Platon und Kepler ihre Freude gehabt! Trotz der grosen Zahl an Atomen weist das Cluster-Anion 1 eine ikosaedrische Struktur auf – sicherlich ein Novum in der Geschichte der Chemie! Es setzt sich derart aus 12 {Mo11}-Fragmenten zusammen, das im resultierenden kugelformigen Gebilde die funfzahligen Drehachsen erhalten bleiben. Da man in 1 ein in eine Kugel einbeschriebenes Ikosaeder erkennen kann, ahnelt dieses Anion strukturell dem beruhmten Keplerschen Schalenmodell des Kosmos (siehe Bild).

Giant Ring-Shaped Building Blocks Linked to Form a Layered Cluster Network with Nanosized Channels: [Mo124VIMo28VO429(μ3-O)28H14(H2O)66.5]16−

A novel type of electron-rich (basic!) nanosized channels can be built up by linking giant ring-shaped building blocks, which occur in the layered compound of composition [Mo124VIMo28VO429(μ3-O)28H14(H2O)66.5]16− (see figure). The corresponding sodium salt is obtained by reduction of an acidified aqueous molybdate solution under special reaction conditions.

Unusual Stepwise Assembly and Molecular Growth: [H14Mo37O112]14− and [H3Mo57V6(NO)6O189(H2O)12(MoO)6]21−

The understanding of the formation of complex molecular systems from simple building blocks by conservative self-assembly processes is still a challenge. We report the synthesis and structural characterization of the large reduced polyoxometallate compounds (NH4)(14)[H14Mo37O112]. 35 H2O (1), (NH4)(21)[H3Mo57V6(NO)(6)O-183(H2O)(18)]. 55H(2)O (2) (by an improved synthesis) and Na-3(NH4)(18)[H3Mo63V6(NO)(6)O-195(H2O)(12)]. 41H(2)O (3). The cluster systems are formed by a stepwise growth process. This implies the appearance, during the cluster formation, of ephemeral polyoxometallate intermediates (some of which we were able to isolate). The negative charge and therefore the nucleophilicity of the intermediate cluster fragments increase when they are reduced, resulting in further attraction of electrophiles and thus in growth of molecular systems. IN the case of the cluster anion of 3 we observed, correspondingly, the loss of an [MoO](4+) oxometallate fragment by air oxidation; this implies that aits uptake and release are controlled by th degree of reduction of the cluster. correspondingly, intermediates between the anions of 2 and 3 of the {Mo57+xV6} type could be isolated. The unusual anion of 1 is formed by symmetry breaking processed.

Building blocks as disposition in solution: [{MoVIO3(H2O)}10{VIVO(H2O)}20{(MoVI/MoVI5O21)(H2O)3}10({MoVIO2(H2O)2}5/2)2 ({NaSO4}5)2]20–, a giant spherical cluster with unusual structural features of interest for supramolecula

The unique polyoxometalate compound Na20[{MoVIO3- (H2O)}10{VIVO(H2O)}20{(MoVI/MoVI5O21)(H2O)3}10({MoVI- O2(H2O)2}5/2)2 ({NaSO4}5)2]·xH2O 1 (x ≈ 170) shows remarkable structural features: e.g. (i) {MoVI/MoVI5}-type pentagons as building blocks (being present in the relevant reaction medium as disposition), (ii) a ‘magnetic ring-shaped band’ built up by ten linked {VIV3} triangles having common corners and (iii) two {NaSO4}5 rings encapsulated inside the cavity of an icosidodecahedron formed by twenty triangular and twelve pentagonal faces built up by ten MoVI and twenty VIV centres, respectively.