{XW12O40 [Cu(en)2(H2O)]3} (X=V, Si): Two novel tri-supported Keggin POMs with transition metal complexes

Insights into organic-inorganic hybrid molecular materials: organoimido functionalized polyoxomolybdates

Polyoxometalates (POMs) are polyatomic anions that comprise transition metal group 5 (V, Nb, Ta) or group 6 (Mo, W) oxyanions connected together by shared oxygen atoms. POMs are fascinating because of their exclusive and remarkable characteristics. One of the most interesting features of POMs is their capability to function as an electron relay by performing stepwise multi-electron redox reactions while maintaining their structural integrity. Functionalization of POMs with amino organic compounds results in organoimido derivatives of polyoxometalates, which have aroused interest due to augmentation of their properties. Comprehensive study has shown that the synthesis methodologies to obtain desired organoimido derivatives of POMs by employing various imido-releasing reagents have progressed drastically in recent decades, particularly the innovative DCC-dehydrating technique. These organoimido functionalized POMs have been used as major building blocks to develop unique nanostructured organic-inorganic hybrid molecular materials. Many conventional organic synthesis processes such as Pd-catalyzed carbon-carbon coupling and esterification reactions have been performed with organoimido functionalized POMs where the presence of POM triggered the reaction process. Thus, investigation of the reactivity of organoimido derivatives of POMs foreshadows the intriguing future of POMs chemistry.

On the preferences of five-membered chelate rings in coordination chemistry: insights from the Cambridge Structural Database and theoretical calculations

The purpose of this review is to give an overview of three important N-bidentate ligands: 1,10-phenanthroline (phen), 2,2'-bipyridine (bpy), and ethylenediamine (en). We have not attempted to be comprehensive because of the huge amount of activity being done in coordination chemistry using these ligands. Instead we present a full structural and geometrical study by using the Cambridge Structural Database (CSD) combined with theoretical calculations that allow us to parameterize their coordinating properties and ability to coordinate to transition and non-transition metals. More importantly, we illustrate that upon coordination and formation of the five-membered chelate ring, these ligands are able to adapt themselves to the requirements of the different metals by changing the MN distances and NMN angles. Therefore, a redefinition of the preferences of these ligands to metals with large ionic radii is needed. Finally, we will present some facts about the participation of these ligands in inorganic-organic hybrids (IOHs) based on Keggin polyoxometalates (POMs).

Hydrothermal synthesis, X-ray structure and DFT and magnetic studies of a (H2SiW12O40)2− based one-dimensional linear coordination polymer

In this paper, we report the synthesis and characterization of a novel POM-based inorganic–organic hybrid with an in situ transformation of pyridine-2,3-dicarboxylic acid into nicotinic acid and 2-hydroxynicotinic acid under hydrothermal conditions.

Three novel polyoxoanion-supported compounds: confinement of polyoxoanions in Ni-containing rigid concave surfaces with enhanced NLO properties

Three new polyoxometalates confined in metal-containing rigid concave surfaces were developed. All of them gave a strong third-order NLO response.

A new 3D framework based on reduced Wells-Dawson arsenotungstates as eight-connected linkages

A compound representing the first example of high dimensional and high connected hybrid based on reduced Wells-Dawson arsenotungstates has been synthesized, and its electrocatalytic and photocatalytic properties have been investigated.

μ(3)-Dodeca-tungsto(V,VI)aluminato-κO:O':O''-tris-[aqua-bis-(ethyl-ene-diamine-κN,N')copper(II)]

The title compound, [AlCu(3)W(12)O(40)(C(2)H(8)N(2))(6)(H(2)O)(3)], was prepared under hydro-thermal conditions. The Cu(2+) ion displays an elongated octa-hedral geometry defined by one bridging O atom from the polyoxidoanion and a coordinated water mol-ecule in axial positions and four N atoms of the two chelating ethyl-enediamine (en) ligands in equatorial positions. The one-electron reduced [AlW(12)O(40)](6-) anion coordinates three [Cu(en)(H(2)O)](2+) fragments, generating a neutral tri-supported Keggin-type polyoxidometalate (POM). This tri-supported POM is located in a special position of [Formula: see text] symmetry and therefore O atoms from the central AlO(4) tetra-hedron are disordered over two sets of sites. Disorder is also observed for three other bridging O atoms of the POM. In the crystal, mol-ecules are connected via N-H⋯O and O-H⋯O hydrogen bonds, forming a three-dimensional framework.

Bis[tris-(ethyl-enediamine-κN,N')cobalt(III)] octa-kis-μ-(3)-oxido-hexa-deca-μ(2)-oxido-tetra-deca-oxido-μ(12)-tetra-oxo-silicato-octa-molybdenum(VI)hexa-vanadium(IV,V) hexa-hydrate

The title compound, [Co(C₂H₈N₂)₃]₂[SiMo₈V₄O₄₀(VO)₂]·6H₂O, was prepared under hydro­thermal conditions. The asymmetric unit consists of a transition metal complex [Co(en)₃]³⁺ cation (en is ethyl­enediamine), one half of an [SiMo₈V₄O₄₀(VO)₂]⁶⁻ heteropolyanion, two solvent water mol­ecules in general positions and two half-mol­ecules of water located on a mirror plane. In the complex cation, the Co³⁺ ion is in a distorted octa­hedral coordination environment formed by six N atoms of the three chelating en ligands. One of the en ligands exhibits disorder of its aliphatic chain over two sets of sites of equal occupancy. The [SiMo₈V₄O₄₀(VO)₂]⁶⁻ heteropolyanion is a four-electron reduced bivanadyl-capped α-Keggin-type molybdenum–vanadium–oxide cluster. In the crystal, it is located on a mirror plane, which results in disorder of the central tetra­hedral SiO₄ group: the O atoms of this group occupy two sets of sites related by a mirror plane. Furthermore, all of the eight μ₂-oxide groups are also disordered over two sets of sites with equal occupancy. There are extensive inter­molecular N—H⋯O hydrogen bonds between the complex cations and inorganic polyoxidoanions, leading to a three-dimensional supra­molecular network.