Dilacunary Decatungstates Functionalized by Organometallic Ruthenium(II), [{Ru(C6H6)(H2O)}{Ru(C6H6)}(γ-XW10O36)]4- (X = Si, Ge)

{Ru(C6 H6 )}-Decorating Heteropolymolybdate for Highly Activity Photocatalytic Oxidation of Benzyl Alcohol to Benzaldehyde

An unclassical structure of {Ru(C6 H6 )}-based polyoxometalate, Cs6 H4 [Te2 Mo12 O46 {Ru(C6 H6 )}] ⋅ 16.5H2 O (1), has been successfully constructed from {Te2 Mo12 O46 }-type heteropolymolybdate and {Ru(C6 H6 )} group, which structure type was discovered for the first time. Compound 1 not only possesses strong light-harvesting ability, but also exhibits high carrier separation efficiency and lower charge transfer resistance. Under visible light irradiation, compound 1 displayed excellent catalytic activity and circularity in the conversion of benzyl alcohol to benzaldehyde (yield=94 %; turnover number=500; turnover frequency=20.8 h-1 ). Finally, the electron paramagnetic resonance measurement and energy level matching analysis provide theoretical basis for the derivation of the reaction mechanism.

Molar-Ratio-Dependent Coordination Assembly of Organoiridium(III)-Octatungstate Complexes in Aqueous Solution

We scrutinized the speciation of Cp*Ir-containing tungsten oxide clusters (Cp* is pentamethylcyclopentadienyl anion) in aqueous mixtures of [(Cp*IrCl)₂(μ-Cl)₂] and Na₂WO₄ in varying molar ratios. ¹H nuclear magnetic resonance (NMR) spectroscopy revealed the formation of three distinct Cp*Ir-polyoxotungstate species in the reaction solution, and they were isolated as Na₄[(Cp*Ir)₂(μ-OH)₃]₂[(Cp*Ir)₂H₂W₈O₃₀] (1), [(Cp*Ir)₂(μ-OH)₃]₂[(Cp*Ir)₂{Cp*Ir(OH₂)}₂H₂W₈O₃₀] (2), and [(Cp*Ir)₂{Cp*Ir(OH₂)}₂{Cp*Ir(OH₂)₂}₂H₂W₈O₃₀](NO₃)₂ (3) from the mixtures in which iridium concentration is less than, equal to, and more than the tungsten concentration, respectively. These results show the octatungstate [H₂W₈O₃₀]^10- anion is the major polyoxotungstate species in the presence of {Cp*Ir}²⁺ cations, and it has high nucleophilicity enough to bind up to six {Cp*Ir}²⁺ cations on its surfaces producing a cationic Cp*Ir-octatungstate complex. The octatungstate anion was also generated from the reaction of [(Cp*IrCl)₂(μ-Cl)₂] and methylammonium paratungstate-B, (CH₃NH₃)₁₀[H₂W₁₂O₄₂], and was isolated as a methylamine-coordinated complex (CH₃NH₃)₂[(Cp*Ir)₂{Cp*Ir(NH₂CH₃)}₂H₂W₈O₃₀] (4), indicating {Cp*Ir}²⁺ cations function as a structure-directing agent that converts tungsten species into octatungstate anions in aqueous solution. In addition, the coordination environment of {Cp*Ir}²⁺ can be further modified by coordination with pyridine forming [{Cp*Ir(NC₅H₅)}₂(μ-OH)₂][(Cp*Ir)₂{Cp*Ir(NC₅H₅)}₂H₂W₈O₃₀] (5).

Roles of Organic Fragments in Redirecting Crystal/Molecular Structures of Inorganic-Organic Hybrids Based on Lacunary Keggin-Type Polyoxometalates

Lacunary polyoxometalates (LPOMs) are key precursors for the synthesis of functional POMs. To date, reviews dedicated to behavioral studies of LPOMs often comprise the role of metal ions, including transition metal (TM) and rare earth (RE) ions, in extending and stability of high-nuclearity clusters. In contrast, the role of organic ligands in the structures and properties of lacunary-based hybrids has remained less explored. In this review, we focus on the role of organic fragments in the self-assembling process of POM-based architectures and discuss relationships between the nature and structure of organic ligand and properties such as the topology of hybrid inorganic–organic material in RE and TM-RE heterometallic derivatives of lacunary Keggin-type POMs. The effects of organic fragment in mixed ligand hybrids are also briefly reviewed.

Interactions of aromatic rings in the crystal structures of hybrid polyoxometalates and Ru clusters

Computational analysis for π–π interaction energies of {(arene)Ru}2+ containing complexes and relative group 5 hybrid polyoxometalates reveals different frameworks. Some perspectives on πOF materials processing and crystal engineering were discussed.

Reactions of [Ru(NO)Cl5]2- with pseudotrilacunary {XW9O33}9- (X = AsIII, SbIII) anions

Reactions of [Ru(NO)Cl₅]^2- with pseudotrivacant B-α-[XW₉O₃₃]^9- (X = As^III, Sb^III) at 160 °C result in the rearrangement of polyoxometalate backbones into {XM₁₈} structures. In the case of arsenic, oxidation of As^III to As^V takes place with the formation of a mixture of plenary and monosubstituted Dawson [As₂W₁₈O₆₂]^6- and [As₂W₁₇Ru(NO)O₆₁]^7- anions, of which the latter was isolated as Me₂NH₂⁺ (DMA-1a and DMA-1b) and Bu₄N⁺ (Bu₄N-1) salts and fully characterized. Both α₁ and α₂ isomers of [As₂W₁₇Ru(NO)O₆₁]^7- were present in the reaction mixture; pure [α₂-As₂W₁₇Ru(NO)O₆₁]^7- was isolated as the Bu₄N⁺ salt. In the case of antimony, [SbW₉O₃₃]^9- is converted into a mixture of [SbW₁₈O₆₀]^9- and [SbW₁₇{Ru(NO)}O₅₉]^10-. The formation of trisubstituted [SbW₁₅{Ru(NO)}₃O₅₇]^12- as a minor byproduct was detected by HPLC-ICP-AES. The monosubstituted [SbW₁₇{Ru(NO)}O₅₉]^10- anion was isolated as DMAH⁺ (DMA-2) and mixed inorganic cation (CsKNa-2) salts and characterized by XRD, HPLC-ICP-AES, EA and TGA techniques. X-ray analysis shows the presence of the {Ru(NO)}-group in the 6-membered ("equatorial") belt of the Sb-free hemisphere. The experimental findings were confirmed and interpreted by means of quantum chemical calculations.

19-Tungstodiarsenate(III) Functionalized by Organoantimony(III) Groups: Tuning the Structure-Bioactivity Relationship

A family of three discrete organoantimony(III)-functionalized heteropolyanions-[Na{2-(Me2HN(+)CH2)C6H4Sb(III)}As(III)2W19O67(H2O)](10-) (1), [{2-(Me2HN(+)CH2)C6H4Sb(III)}2As(III)2W19O67(H2O)](8-) (2), and [{2-(Me2HN(+)CH2)C6H4Sb(III)}{WO2(H2O)}{WO(H2O)}2(B-β-As(III)W8O30)(B-α-As(III)W9O33)2](14-) (3)-have been prepared by one-pot reactions of the 19-tungstodiarsenate(III) precursor [As(III)2W19O67(H2O)](14-) with 2-(Me2NCH2)C6H4SbCl2. The three novel polyanions crystallized as the hydrated mixed-alkali salts Cs3KNa6[Na{2-(Me2HN(+)CH2)C6H4Sb(III)}As(III)2W19O67(H2O)]·43H2O (CsKNa-1), Rb2.5K5.5[{2-(Me2HN(+)CH2)C6H4Sb(III)}2As(III)2W19O67(H2O)]·18H2O·Me2NCH2C6H5 (RbK-2), and Rb2.5K11.5[{2-(Me2HN(+)CH2)C6H4Sb(III)}{WO2(H2O)}{WO(H2O)}2(B-β-As(III)W8O30)(B-α-As(III)W9O33)2]·52H2O (RbK-3), respectively. The number of incorporated {2-(Me2HN(+)CH2)C6H4Sb(III)} units could be tuned by careful control of the experimental parameters. Polyanions 1 and 2 possess a dimeric sandwich-type topology, whereas 3 features a trimeric, wheel-shaped structure, representing the largest organoantimony-containing polyanion. All three compounds were fully characterized in the solid state via single-crystal X-ray diffraction (XRD), infrared (IR) spectroscopy, and thermogravimetric analysis, and their aqueous solution stability was validated by ultraviolet-visible light (UV-vis) and multinuclear ((1)H, (13)C, and (183)W) nuclear magnetic resonance (NMR) spectroscopy. Effective inhibition against six different types of bacteria was observed for 1 and 2, and we could extract a structure-bioactivity relationship for these polyanions.

Harvesting visible light for aerobic oxidation of alcohols by a novel and efficient hybrid polyoxometalate

The synthesis, characterization and photocatalytic application of a novel hybrid polyoxometalate, ((n-C₄H₉)₄N)₄[SiW₁₁O₃₉(Si(CH₂)₃NCHC₁₄H₉)₂O], which can absorb light in the visible region, in the oxidation of alcohols under an O₂ atmosphere are reported.

Complexation of metal carbonyl units with [α-PW11O39]7− and [α2-P2W17O61]10−: insights into the chiral “twisted-sandwich” dimeric structures

Capturing [M(CO)₃]⁺ (M = Re, Mn) by [α-PW₁₁O₃₉]⁷⁻ or [α₂-P₂W₁₇O₆₁]¹⁰⁻ leads to polyoxometalate-supported metal carbonyl complexes with chiral “twisted-sandwich” structures.

Divacant polyoxotungstates: reactivity of the gamma-decatungstates [γ-XW10O36]8-(X = Si, Ge)

The dilacunary, Keggin-based gamma-decatungstate ions [γ-XW(10)O(36)](8-) (X = Si, Ge) {XW(10)} exhibit an exciting and versatile solution chemistry, which is probably unmatched by any other lacunary polytungstate. The reactivity of {XW(10)} in the presence, and even absence, of electrophiles, includes loss/gain of tungsten, isomerization, and dimerization. Ever since the syntheses and structures of {XW(10)} 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.

Novel Doped Tungstovanadate and Molybdovanadate with Bi-antimony-Capped Keggin Structure

Three novel V-centred Keggin-based compounds containing cap-shaped Sb atoms: (HDMF)2[(VO4)W5.65V7.74Sb2.61O36.77]·6H2O (1), [Co(phen)3]2[(VO4)Mo9.58V2.42Sb2O36]·6H2O (2) and [Ni(phen)2(H2O)]2[(VO4)Mo8V4Sb2O36]·2H2O (3) (DMF = dimethylformamide; phen = 1,10-phenanthroline) have been synthesized and characterized. X-ray diffraction analysis revealed that compound 1 consists of an unusually one-dimensional 12-tungstovanadate Keggin-based polymer, in which the reduced tungstovanadate Keggin species are stabilized by introducing capping {VO} and {Sb} groups and then linked into chains via V(Sb)–O–V(Sb) interactions. Both 2 and 3 are built from secondary metal–ligand groups (Co-phen for 2, Ni-phen for 3) and 12-molybdovanadate doped Keggin-type cores with two antimony atoms capping two opposite sites. The anion in 3 represents a bi-capped and bi-supported Keggin-type structure. The electrochemical properties of 2- and 3-modified carbon paste electrodes (2-CPE and 3-CPE) are also studied.

Rare sandwich-type polyoxomolybdates constructed from Di-/tetra-nuclear transition-metal clusters and trivacant keggin germanomolybdate fragments

Two types of rare sandwich-type germanomolybdates [Na(12)(H(2)O)(36)][Cu(2)(beta-Y-GeMo(9)O(33))(2)].3H(2)O (1), [N(CH(3))(4)](4) [Na(6)(H(2)O)(24)][Cr(2)(beta-Y-GeMo(9)O(33))(2)].7H(2)O (2), and [Na(11)(H(2)O)(25)]H[M(4)(H(2)O)(2)(alpha-B-GeMo(9)O(34))(2)].6H(2)O (M = Ni(II) for 3, M = Mn(II) for 4 and M = Co(II) for 5) have been synthesized and characterized by elemental analyses, ICP spectra, IR spectroscopy, UV spectroscopy, thermogravimetry (TG) analyses (for 1-3), X-ray photoelectron spectroscopy (XPS) (for 1 and 3), X-ray powder diffraction (XRPD) (for 1 and 3) and single-crystal X-ray diffraction. To our knowledge, 1-5 represent the first sandwich-type germanomolybdates containing both {beta-Y-GeMo(9)O(33)}/{alpha-B-GeMo(9)O(34)} fragments and transition-metal clusters. Interestingly, 1 and 2 display the rare dinuclear transition-metal substituted sandwich-type structures with unusual trivacant {beta-Y-GeMo(9)O(33)} germanomolybdate units whereas 3-5 exhibit the first tetranuclear transition-metal substituted sandwich-type structures with familiar trivacant {alpha-B-GeMo(9)O(34)} germanomolybdate units. Surface photovoltage spectroscopy (SPS) and electric field induced surface photovoltage spectroscopy (EFISPS) measurements reveal that 1 and 3 bear the behavior of the n-type semiconductor. Magnetic measurements indicate 1 and 3 demonstrate antiferromagnetic exchange interactions and ferromagnetic exchange interactions, respectively.

Preparation and characterization of Langmuir-Blodgett films of wheel-shaped Cu-20 tungstophosphate and DODA by two different strategies

A novel surfactant-encapsulated organic-inorganic hybrid compound (DODA)(24)Li[Cu(20)Cl(OH)(24)(P(8)W(48)O(184))] x 18 H(2)O (DODA-Cu20) has been prepared from the wheel-shaped tungstophosphate salt K(12)Li(13)[Cu(20)Cl(OH)(24)(H(2)O)(12)(P(8)W(48)O(184))] x 22 H(2)O (Cu20) and dimethyldioctadecylammonium bromide (DODA), and it has been characterized by elemental analysis (EA), thermogravimetric analysis (TGA), (1)H NMR, Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD) measurements. Monolayer and multilayer films of DODA-Cu20 were fabricated on different substrates by the Langmuir-Blodgett (LB) technique using H(2)O as the subphase. Another type of organic-inorganic hybrid film, DODA/Cu20, was also deposited on the same substrates as used for the film containing DODA-Cu20 under the same conditions by the LB technique using a Cu20 aqueous solution as the subphase and DODA as the cationic amphiphile for comparison. Both thus-prepared organic-inorganic hybrid films were characterized by UV-vis spectroscopy, XRD, transmission and polarized FT-IR spectroscopy, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The results indicate that stable monolayers at the air-water interface for DODA-Cu20 and at the air-Cu20 solution interface for DODA can be formed and that two LB films containing DODA-Cu20 and DODA/Cu20 constructed by two different methods both exhibit well-ordered lamellar structures. It is proposed that Cu20 exhibits different packing modes in the two LB films depending on the deposition strategy used.

Polyoxometalate embedding of a tetraruthenium(IV)-oxo-core by template-directed metalation of [gamma-SiW10O36]8-: a totally inorganic oxygen-evolving catalyst

Solid state and solution evidence confirms the embedding of an adamantane-like, Ru4O6 fragment by the divacant, gamma-decatungstosilicate ligand. The resulting complex catalyzes water oxidation to oxygen with TON up to 500 and TOF > 450 h-1.