A Bicadmium-Substituted Polyoxometalate Network Based on a Vanadosilicate Cluster for the Selective Oxidation of Styrene to Benzaldehyde

A new bicadmium-substituted vanadosilicate, [Cd(en)₂]₂[(en)₂Cd₂Si₈V₁₂O₄₀(OH)₈(H₂O)_0.5]·5H₂O (1; en = ethylenediamine), had been hydrothermally synthesized and characterized. Structural analysis revealed that the kind of new [(en)₂Cd₂Si₈V₁₂O₄₀(OH)₈(H₂O)_0.5]^4- polyoxoanionic cluster was derived from the classical {V₁₈O₄₂} cluster by replacing six {VO₅} square pyramids with four {Si₂O₇} and two [Cd(en)]²⁺ groups. Notably, such mixed substitution of both main-group and transition metals in polyoxovanadates is much less developed. Furthermore, compound 1 displays efficient catalytic activity toward the selective oxidation of styrene to benzaldehyde with a conversion of 97% and a selectivity of 87% in 8 h.

New pronounced progress in the synthesis of group 5 polyoxometalates

This highlight summarizes new developments made in group 5 polyoxometalate science of high nuclearity clusters with focus on synthetic approaches.

Soluble Hetero-Polyoxovanadates and Their Solution Chemistry Analyzed by Electrospray Ionization Mass Spectrometry

Polyoxometalates (POMs) are an intriguing class of compounds due to their tremendous structural variety and the wide spectrum of resulting properties, which make them interesting for applications in fields such as catalysis, material science or nanotechnology. Their ability to form large supramolecular architectures by self-assembly offers an entry to complex, functional systems. After an introduction into the structure and synthesis of POMs of the early transition metals, recently discovered water-soluble antimonato polyoxovanadates (Sb-POVs) and the investigation of their chemical reactivity are discussed. Electrospray ionization mass spectrometry (ESI-MS) is presented as an analytical technique suitable to investigate the structure of complex POM assemblies in solution and to probe the underlying reactivity and formation mechanisms. This Minireview highlights the first studies on the soluble Sb-POVs and how the knowledge of their reactivity obtained by ESI-MS has fostered the syntheses of numerous novel Sb-POV compounds.

Mixing SbIII and GeIV occupancy in the polyoxovanadate {V14E8} archetype

The first mixed germanato-antimonato derivative of the {V14E8O42} (E=semi-metal) cluster archetype has been synthesized under hydrothermal conditions and isolated as {Ni(phen)3}2[α-VIV 14SbIII 5GeIV 3O42(OH)3(H2O)]· ≈16H2O (phen=1,10-phenanthroline). In the cluster anion, seven of the eight hetero-metal positions are occupied by disordered Ge/Sb atoms, while one position is fully occupied by Sb atoms. The [V14Sb5Ge3O42(OH)3(H2O)]6− anions are arranged in pairs with remarkably short inter-cluster Sb···O contacts. Bond valence sum calculation strongly suggests that the Sb···O contact must be taken into account as a weak bond. The magnetic properties are dominated by strong intra-cluster antiferromagnetic exchange interactions, and the cluster anion is magnetically quasi-isolated from the spins of the Ni2+ complex cations.

Ordnung muss sein: heteroelement order and disorder in polyoxovanadates

Three new mixed antimonato–germanato polyoxovanadates exhibit different degrees of order of their unique crystallographic heterometal atom positions.