Fullerene-like Niobovanadate Cage Built from {(Nb)V5 } Pentagon.

The striking aesthetic appeal of fullerene-like clusters has captured the interest of researchers. Nevertheless, the assembly of fullerene-like polyoxovadanadate (POV) cages remains a significant challenge due to the scarcity of suitable pentagonal motif. Herein, we have successfully synthesized the first fullerene-like all-inorganic POV cage, {(V2 O)V30 Nb12 O102 (H2 O)12 } (V30 Nb12 ), by introducing Nb into the POVs. V30 Nb12 is assembled by 12 heterometallic {(Nb)V5 } pentagons through sharing V centers with Ih symmetry, reminiscent of C60 . To our knowledge, the fullerene-like V30 Nb12 not only represents the highest-nuclearity POV cage but also stands as the first niobovanadate cluster. Notably, V30 Nb12 exhibits excellent solution stability, as confirmed by ESI-MS, FT-IR and UV/Vis spectra. As there is no protection organic ligand on its outer surface, V30 Nb12 can be further modified with Cu-complexes to form a fullerene-like cluster based zigzag chain (Cu-V30 Nb12 ).

Double Cation-π Directed Two-Dimensional Metallacycle-Based Hierarchical Self-Assemblies for Dual-Mode Catalysis.

Hierarchical self-assembly of Pt(II) metallacycles for the construction of functional materials has received considerable research interest, owing to their potential to meet increasing complexity and functionality demands while being based on well-defined scaffolds. However, the fabrication of long-range-ordered Pt(II) metallacycle-based two-dimensional hierarchical self-assemblies (2D HSAs) remains a challenge, primarily because of the limitations of conventional orthogonal noncovalent interaction (NCI) motifs and the intrinsic characteristics of Pt(II) metallacycles, making the delicate self-assembly processes difficult to control. Herein, we prepare well-regulated Pt(II)-metallacycle-based 2D HSAs through a directed strategy involving double cation-π interactions derived from C3-symmetric hexagonal Pt(II) metallacycles and C2-symmetric sodium phenate monomers. Spatially confined arrays of planar Pt(II) metallacycles and the selective growth of self-assemblies at desired locations are achieved by employing strong cation-π driving forces with well-defined directionality as the second orthogonal NCI, realizing the bottom-up, three-stage construction of Pt(II)-metallacycle-based 2D HSAs. The resultant 2D HSAs are applied as dual-mode catalysis platforms, which are loaded with two different nanocatalysts, one promoting catalytic oxidation and the other promoting photocatalytic reduction.

A Rhombus-Like Tetrameric Vanadoniobate Containing Pseudo-Sandwich-Type {Li ⊂ V2O8(Nb5O14)2} and Its Electrocatalytic Activity for the Selective Oxidation of Benzyl Alcohol.

Ongoing research on V-containing polyoxoniobates (PONbs) is driven by their diverse structures and potential applications. Although Lindqvist-type {Nb6O19} is a widely used building block in PONbs, vanadoniobates based on {Nb6O19} and/or its derivatives are still very limited. Herein, a discrete vanadoniobate, LiNa14K11[Li2 ⊂ VIV8Nb32O110]·45H2O (1), has been synthesized by a hydrothermal method, which shows a rhombus-like tetrameric structure composed of two {V2O6(Nb6O19)} and two {Li ⊂ V2O8(Nb5O14)2} subunits derived from {Nb6O19}. Notably, the {Li ⊂ V2O8(Nb5O14)2} subunit has an interesting pseudo-sandwich-type structure, where a {LiV2O8} belt is coordinated by two monolacunary {Nb5O14} molecules and the central site of the cluster is occupied by Li+. Considering that 1 has both basic hexaniobates and redox active V centers, 1 was used as a noble metal-free electrocatalyst for the selective oxidation of benzyl alcohol to benzaldehyde, achieving complete conversion of benzyl alcohol with 94% selectivity for benzaldehyde in 3 h under ambient conditions without using any alkaline additives. Moreover, the catalytic performance of 1 remained largely unchanged after four cycles.

Redox-switchable Pickering emulsion stabilized by hexaniobate-based ionic liquid for oxidation catalysis.

Pickering emulsions provide an efficient platform for interfacial catalysis, but product separation and catalyst recycling rely on time- and energy-consuming centrifugation or filtration. Herein, three hexaniobate-based ionic liquids, [CnMIM]Nb6 (n = 12, 14 and 16), have been successfully synthesized by self-assembly of hexaniobate (Nb6) with long alkyl chain-modified imidazole cations (CnMIM). Interestingly, the surface wettability of [C16MIM]Nb6 can be regulated by redox reactions, and the rapid switch between emulsification and demulsification can be achieved by alternately adding oxidant (H2O2) and reductant (Na2SO3) agents. Furthermore, studies suggest that the redox-responsive behavior is related to the reversible transformation between [C16MIM]Nb6 and peroxohexaniobate [C16MIM]Nb6-O2, which leads to the rearrangement of hydrophobic long chains on imidazole cations around hydrophilic Nb6. Moreover, [C16MIM]Nb6 can effectively catalyze oxidative desulfurization (conversion > 99%), and the separation of clean model oil and the recycling of the interfacial catalyst were realized in a facile route.

{V6 } Ring Sandwiched Polyoxoniobate as Molecular Electrocatalyst for Oxidant-Free Synthesis of Sulfoxides.

Electrocatalytic oxidation of organic molecules to value-added chemicals has attracted recent attention. Although a series of transition metal based electrocatalytic materials have been developed, the lack of precise structure information generates great challenges in understanding the catalytic mechanism at a molecular level. Herein, we present the synthesis and characterization of a molecular electrocatalyst, Na2 K6 H14 [(VO)6 (α-TeNb9 O33 )2 ] ⋅ 31H2 O ⋅ 2.5 C2 H8 N2 (abbreviated as V6 (TeNb9 )2 ), where a reduced {V6 } ring is sandwiched by two trivacant Keggin-type {α-TeNb9 O33 }. V6 (TeNb9 )2 as heterogeneous electrocatalyst can selectively convert 95 % of thioanisole to sulfoxide with the Faraday efficiency up to 98 %. Notably, the important role of the embedded {V6 } ring in the electrocatalytic oxidation was illustrated by comparing with {Nb6 } ring sandwiched catalyst, Na5 K7 H4 [(NbO)6 (α-TeNb9 O33 )2 ] ⋅ 17H2 O (abbreviated as Nb6 (TeNb9 )2 ). Mechanism studies reveal that during the electrocatalytic oxidation process water is the only oxygen source and a key intermediate PhCH3 S+ ⋅ is involved.

Controllable Assembly of Vanadium-Containing Polyoxoniobate-Based Materials and Their Electrocatalytic Activity for Selective Benzyl Alcohol Oxidation.

During the controllable synthesis of two vanadium-containing Keggin-type polyoxoniobates (PONbs), [Ni(en)2]5[PNb12O40(VO)5](OH)5·18H2O (1) and [Ni(en)3]5[PNb12O40(VO)2]∙17H2O (2, en = ethylenediamine) are realized by changing the vanadium source and hydrothermal temperature. Compounds 1 and 2 have been thoroughly characterized by single-crystal X-ray diffraction analysis, FT-IR spectra, X-ray photoelectron spectrum (XPS), powder X-ray diffraction (PXRD), etc. Compound 1 contains a penta-capped Keggin-type polyoxoniobate {PNb12O40(VO)5}, which is connected by adjacent [Ni(en)2]2+ units into a three-dimensional (3D) organic-inorganic framework, representing the first nickel complexes connected vanadoniobate-based 3D material. Compound 2 is a discrete di-capped Keggin-type polyoxoniobate {PNb12O40(VO)2} with [Ni(en)3]2+ units as counter cations. Compounds 1 and 2 have poor solubility in common solvents and can keep stable in the pH range of 4 to 14. Notably, both 1 and 2 as electrode materials are active for the selective oxidation of benzyl alcohol to benzaldehyde. Under ambient conditions without adding an alkaline additive, compound 1 as a noble metal free electrocatalyst can achieve 92% conversion of benzyl alcohol, giving a Faraday efficiency of 93%; comparatively, 2 converted 79% of the substrate with a Faraday efficiency of 84%. The control experiments indicate that both the alkaline polyoxoniobate cluster and the capped vanadium atoms play an important role during the electrocatalytic oxidation process.

Electrocatalytic ethylbenzene valorization using a polyoxometalate@covalent triazine framework with water as the oxygen source.

Ethylbenzene (EB) oxidation is an important transformation in the chemical industry. Herein, PMo10V2@CTF, a noble metal free electrocatalyst, was used to promote the oxidative upgrading of EB. Under ambient conditions, 65% of EB was converted to three value-added products using water as the oxygen source yielding a total Faraday efficiency of 90.4%. This excellent performance is ascribed to the homogeneous dispersion of PMo10V2 and its dual role in the electrocatalytic process.

Reduced polyoxomolybdate immobilized on reduced graphene oxide for rapid catalytic decontamination of a sulfur mustard simulant.

Keggin-type polyoxometalates (POMs) were immobilized on poly(diallyldimethylammonium chloride) (PDDA) functionalized reduced graphene oxide (rGO) by a facile and broad-spectrum hydrothermal method. The prepared POMs@PDDA-rGO composites (POM = H3PMo12O40, H3PW12O40, H5PMo10V2O40) have been thoroughly characterized using a series of techniques. The three composites can catalyze the oxidative decontamination of a sulfur mustard simulant, 2-chloroethyl ethyl sulfide (CEES) in the order of PMo12@PDDA-rGO > PMo10V2@PDDA-rGO > PW12@PDDA-rGO. Notably, under ambient conditions PMo12@PDDA-rGO can convert 99% of CEES within 30 min in the presence of nearly stoichiometric aqueous H2O2 (3 wt%) and its catalytic activity is significantly higher than that of homogeneous H3PMo12O40. XPS spectral analysis and control experiments indicate that the Mo center of POM is reduced from +6 to +5 during the hydrothermal process, and the excellent catalytic performance is related to the reduction of Mo. Moreover, the PMo12@PDDA-rGO composite is stable during the decontamination process and it can be used for at least five cycles without loss of activity.

Efficient Conversion of Biomass-Derived Levulinic Acid to γ-Valerolactone over Polyoxometalate@Zr-Based Metal-Organic Frameworks: The Synergistic Effect of Bro̷nsted and Lewis Acidic Sites.

Catalytic transformation of levulinic acid (LA) to γ-valerolactone (γ-GVL) is an important route for biomass upgradation. Because both Bro̷nsted and Lewis acidic sites are required in the cascade reaction, herein we fabricate a series of H3PW12O40@Zr-based metal-organic framework (HPW@MOF-808) by a facile impregnation method. The synthesized HPW@MOF-808 is active for the conversion of LA to γ-GVL using isopropanol as a hydrogen donor. Interestingly, with the increase in the HPW loading amount, the yield of γ-GVL increases first and then decreases, and 14%-HPW@MOF-808 gave the highest γ-GVL yield (86%). The excellent catalytic performance was ascribed to the synergistic effect between the accessible Lewis acidic Zr4+ sites in MOF-808 and Bro̷nsted acidic HPW sites. Based on the experimental results, a plausible reaction mechanism was proposed: the Zr4+ sites catalyze the transfer hydrogenation of carbonyl groups and the HPW clusters promote the esterification of LA with isopropanol and lactonization to afford γ-GVL. Moreover, HPW@MOF-808 is resistant to leaching and can be reused for five cycles without significant loss of its catalytic activity.

Imidazole-Functionalized Polyoxometalate Catalysts for the Oxidation of 5-Hydroxymethylfurfural to 2,5-Diformylfuran Using Atmospheric O2.

Biomass as a sustainable and abundant carbon source has attracted considerable attention as a potential alternative to petroleum resources. The selective oxidation of 5-hydroxymethylfurfural (HMF), a versatile platform molecule, to value-added 2,5-diformylfuran (DFF) provides an efficient pathway for biomass valorization. Herein, three discrete imidazole-functionalized polyoxometalates (POMs), HPMo8VVI4O40(VVO)2[(VIVO)(IM)4]2·nH2O·(IM)m (IM = 1-methylimidazole, n = 4, m = 8 for 1; IM = 1-ethylimidazole, n = 4, m = 9 for 2; IM = 1-propylimidazole, n = 0, m = 4 for 3), have been successfully synthesized by a facile solvothermal method and thoroughly characterized by routine techniques. Compounds 1-3 contain a bi-capped pseudo-Keggin {HPMo8V4O40(VO)2} and two imidazole-functionalized {(VO)(IM)4} groups, which, to our knowledge, represent the first examples of organic-functionalized Mo-V clusters. Compounds 1-3 as heterogeneous catalysts can effectively promote the transformation of HMF to DFF using atmospheric O2 as oxidant. Under minimally optimized conditions, 95% of HMF was converted by 1 with 95% selectivity for DFF and its catalytic activity was basically maintained after five cycles. Moreover, the important roles of the bi-capped pseudo-Keggin cluster and the functionalized V groups in the selective oxidation of HMF have been explored. According to experimental and spectroscopic results, a three-step oxidation mechanism of HMF to DFF has been proposed.

Assembly of Lanthanide-Containing Tungstotellurates(VI): Syntheses, Structures, and Catalytic Properties.

Lanthanide (Ln)-containing polyoxometalates (POMs) have attracted particular attention owing to their structural diversity and potential applications in luminescence, magnetism, and catalysis. Herein three types of Ln-containing tungstotellurates(VI) (Ln = Dy3+, Ho3+, Er3+, Tm3+, Yb3+, and Lu3+), dimeric (DMAH) n [H22-n {Ln(H2O)3[TeW17O61]}2]·mH2O (abbreviated as {Ln2Te2W34}; DMAH+ = dimethylammonium), mono-substituted (DMAH)7Na2{H2Ln(H2O)4[TeW17O61]}·mH2O (abbreviated as {LnTeW17}), and three-dimensional (3D) inorganic frameworks (DMAH) n {H3-n Ln(H2O)4[TeW6O24]}·mH2O (abbreviated as {LnTeW6}), have been synthesized by using simple metal salts and characterized by single-crystal X-ray diffraction and other routine techniques. Interestingly, the assembly of these POMs is pH dependent. Using the same starting materials, {Ln2Te2W34} were obtained at pH 1.7, where two Dawson-like monovacant [TeW17O61]14- are linked by two Ln3+ ions; mono-substituted Dawson-like {LnTeW17} were isolated at pH 1.9, and 3D inorganic framework {LnTeW6} based on Anderson-type [TeW6O24]6- were formed at pH 2.3. It was also found that the assembly of Ln-containing POMs depends on the type of Ln3+ ions. The three types of POMs can be prepared by using Ln3+ ions with a relatively smaller ionic radius, such as Tb3+-Lu3+, while the use of Ln3+ ions (La3+-Eu3+) results in the formation of precipitation or {TeW18O62} clusters. Furthermore, three {LnTeW6} (Ln = Tb3+, Er3+, Lu3+) were used as Lewis acid catalysts for the cyanosilylation of benzaldehydes, and their catalytic activity decreases with the decrease of Ln3+ ionic radius, giving the order: {TbTeW6} > {ErTeW6} > {LuTeW6}. Notably, {TbTeW6} is stable to leaching and can be reused for five cycles without a significant loss of its activity.

Self-assembly of polyoxovanadate-capped polyoxoniobates and their catalytic decontamination of sulfur mustard simulants.

We report the synthesis and characterization of two discrete vanadoniobates, H6Cs4Na5K7[V5Nb23O80]·28H2O (1) and H6Cs4Na5K8[V6Nb23O81]·34H2O (2), based on a brand new {Nb23} and a 5/6-nuclear polyoxovanadate cap. The two vanadoniobates as heterogeneous catalysts can effectively promote the oxidative decontamination of sulfur mustard simulants.

Polyoxometalates encapsulated into hollow double-shelled nanospheres as amphiphilic nanoreactors for an effective oxidative desulfurization.

Although some catalytic hollow nanoreactors have been fabricated in the past, the encapsulated active species focus on metal nanoparticles, and a method for polyoxometalate (POM)-containing hollow nanoreactors has seldom been developed. Herein, we report a synthetic strategy towards POM-based amphiphilic nanoreactors, where the hollow mesoporous double-shelled SiO2@C nanospheres were used to encapsulate Keggin-type H3PMo12O40 (PMo12). The outer hydrophobic carbon shell was beneficial for the enrichment of the organic substrate around the nanoreactor and simultaneously prevented the deposition of POMs on the outer surface of the nanoreactor. The inner hydrophilic silica cavity was modified by two types of organosilanes, which not only created an amphiphilic cavity environment but also acted as an anchor to mobilize PMo12. As the POM nanoreactor had the hydrophilic@hydrophobic SiO2@C shell and an amphiphilic cavity, both dibenzothiophene (DBT) and H2O2 could smoothly diffuse into the nanosized cavity, where the DBT was effectively oxidized (conversion: >99%) by the immobilized PMo12 under mild conditions. Importantly, the control experiments indicated that the confined effect of nanoreactor, amphiphilic SiO2@C double-shell, unique cavity environment, and mesoporous channels accounted for an excellent catalytic performance. Moreover, the nanoreactor was robust and could be reused for five cycles without loss of activity.

Mono- and Di-Sc-Substituted Keggin Polyoxometalates: Effective Lewis Acid Catalysts for Nerve Agent Simulant Hydrolysis and Mechanistic Insights.

Recently, the hydrolysis of nerve agents by Lewis acid catalysts has attracted considerable attention. The development of molecular catalysts, such as polyoxometalates (POMs) with Lewis acidic sites, is helpful to improve degradation efficiency and understand the catalytic mechanism at a molecular level. Herein, two novel Keggin-type POMs, namely, mono-Sc-substituted K4[Sc(H2O)PW11O39]·22H2O·2(CH3COOK) (1) and di-Sc-substituted Na7[Sc2(CH3COO)2PW10O38]·10H2O·2CH3COONa (2), have been successfully synthesized and thoroughly characterized by routine techniques. To our knowledge, 1 and 2 represent the first example of discrete Sc-substituted Keggin clusters. Compared with the reported Sc-containing POMs, 1 and 2 exhibit relatively good solubility and stability in aqueous solution, as evidenced by 31P nuclear magnetic resonance spectroscopy and Fourier-transform infrared spectroscopy. The two Sc-substituted POMs can effectively catalyze the hydrolytic decontamination of dimethyl 4-nitrophenyl phosphate (DMNP), a nerve agent simulant, at near-neutral pH. Notably, the catalytic performance of 2 (conversion: 97%) is much better than that of 1 (conversion: 28%). It is found that the different coordination environment of Sc is the key factor to impact their activity. Mechanistic studies including the control experiments and spectroscopy analysis (13C nuclear magnetic resonance spectroscopy and electrospray ionization mass spectrometry) show that under the turnover conditions the coordinated acetate dissociates from 2 and the exposed coordinatively unsaturated Sc center is more active than the water-coordinated Sc in 1 for binding with DMNP.

Mono-transition-metal-substituted polyoxometalate intercalated layered double hydroxides for the catalytic decontamination of sulfur mustard simulant.

The Keggin-type mono-transition-metal-substituted [PW11M(H2O)O39]5- (PW11M, M = Ni, Co, Cu) were intercalated into Zn2Cr-based layered double hydroxide (Zn2Cr-LDH) by an exfoliation-reassembly method and the synthesized Zn2Cr-LDH-PW11M composites were thoroughly characterized by Fourier transform infrared (FT-IR) spectroscopy, powder X-ray diffraction (PXRD), solid state 31P nuclear magnetic resonance (31P NMR) spectroscopy, thermogravimetric analysis (TGA), inductively coupled plasma atomic emission spectroscopy (ICP-AES), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The three composites can be used as heterogeneous catalysts to promote the oxidative decontamination of the sulfur mustard simulant 2-chloroethyl ethyl sulfide (CEES). Interestingly, a cooperative effect between the PW11M cluster and Zn2Cr-LDH is evidenced by the fact that the composites have a higher catalytic performance than either of the individual constituents alone. The catalytic activity of Zn2Cr-LDH-PW11M is significantly influenced by the substituted transition metals, showing the order: Zn2Cr-LDH-PW11Ni > Zn2Cr-LDH-PW11Co > Zn2Cr-LDH-PW11Cu. Under ambient conditions, the Zn2Cr-LDH-PW11Ni composite can convert 98% of CEES in 3 h using nearly stoichiometric 3% aqueous H2O2 with the selectivity of 94% for the nontoxic product 2-chloroethyl ethyl sulfoxide (CEESO). Moreover, the decontaminating material, Zn2Cr-LDH-PW11Ni, is stable to leaching and can be readily reused for up to ten cycles without obvious loss of its activity.

A Versatile Self-Detoxifying Material Based on Immobilized Polyoxoniobate for Decontamination of Chemical Warfare Agent Simulants.

A decontaminating composite, Mg3 Al-LDH-Nb6 , has been successfully prepared by immobilizing Lindqvist [H3 Nb6 O19 ]5- (Nb6 ) into a Mg3 Al-based layered double hydroxide (Mg3 Al-LDH). To our knowledge, this represents the first successful approach to the immobilization of polyoxoniobate. As a versatile catalyst, Mg3 Al-LDH-Nb6 can effectively catalyze the degradation of both vesicant and nerve agent simulants by multiple pathways under mild conditions. Specifically, the sulfur mustard simulant, 2-chloroethyl ethyl sulfide (CEES), is converted into the corresponding nontoxic 2-chloroethyl ethyl sulfoxide (CEESO) by selective oxidation, whereas the Tabun (G-type nerve agent) simulant, diethyl cyanophosphonate (DECP), and the VX (V-type nerve agent) simulant, O,S-diethyl methylphosphonothioate (OSDEMP), are detoxified through hydrolysis and perhydrolysis, respectively. A possible mechanism is proposed on the basis of control experiments and spectroscopic studies. The Mg3 Al-LDH-Nb6 composite exhibits remarkable robustness and can be readily reused for up to ten cycles with negligible loss of its catalytic activity. More importantly, a protective "self-detoxifying" material has easily been constructed by integrating Mg3 Al-LDH-Nb6 into textiles. In this way, the flexible and permeable properties of textiles have been combined with the catalytic activity of polyoxoniobate to remove 94 % of CEES in 1 h by using nearly stoichiometric dilute H2 O2 (3 %) as oxidant with 96 % selectivity.

Recoverable amphiphilic polyoxoniobates catalyzing oxidative and hydrolytic decontamination of chemical warfare agent simulants in emulsion.

Amphiphilic polyoxoniobates (PONbs), [CnH2n+1N(CH3)3]7HNb6O19 (for 1, n=14; for 2, n=16; and for 3, n=18), were successfully prepared by the electrostatic interaction of hexaniobate anions with quaternary ammoniums containing long alkyl chain, and thoroughly characterized by using various techniques including Fourier transform infrared (FT-IR), 1H nuclear magnetic resonance (1H NMR), 13C nuclear magnetic resonance (13C NMR), thermogravimetric analysis (TGA), and elemental analysis. All three PONbs were used in the emulsion systems to catalytically decontaminate chemical warfare agent simulants and the influences of quaternary ammonium cations, polyanions, and amount of catalyst on the catalytic efficiency have been evaluated. Under optimal conditions, catalyst 3 in emulsion can completely convert both a the nerve agent simulant, diethyl cyanophosphonate (DECP), in 2h by hydrolysis and a sulfur mustard simulant, 2-chloroethyl ethyl sulfide (CEES), in 20min by oxidation using nearly stoichiometric 3% aqueous H2O2. Moreover, the amphiphilic catalyst 3 can be simply separated and readily reused for five recycles without obvious losing its activity. To the best of our knowledge, this study represents the first example where the emulsions of PONbs are used in the catalysis.

Self-Assembly of Ln(III)-Containing Tungstotellurates(VI): Correlation of Structure and Photoluminescence.

The generation of five types of Ln(III)-containing tungstotellurates(VI), dimeric (DMAH)12Na2[H10(WO2){Ln(H2O)5(TeW18O65)}2]· nH2O (abbreviated as {Ln2Te2W37}; Ln = Eu, Gd, or Tb; DMAH = dimethylammonium), tetrameric (DMAH)21Na7[H16{Ln(H2O)5(TeW18O64)}4]· nH2O (abbreviated as {Ln4Te4W72}, Ln = Eu or Gd), 2:2 dimeric (DMAH)12[H6{Tb(H2O)3(TeW17O61)}2]·25H2O (abbreviated as {Tb2Te2W34}), 1:1 monosubstituted (DMAH)7Na2[H2Tb(H2O)4(TeW17O61)]·21H2O (abbreviated as {TbTeW17}), and three-dimensional polymer (DMAH)2[HTb(H2O)4{TeW6O24}]·14H2O (abbreviated as {TbTeW6} n), provides insight into the rich condensation chemistry of lacunary and other Dawson-type polyoxometalates. The pH and the type of Ln3+ source both dictate which of these new complexes form. To our knowledge, {Ln4Te4W72} is the highest-nuclearity tungstotellurate to date, and {Tb2Te2W34} and {TbTeW17} contain the first lacunary {TeW17O61}. Electrospray ionization mass spectra analyses indicate that the Dawson-like building blocks, {TeW18O65} and {TeW17O61}, found in solid structures are also present in solution. The intense photoluminescence (characteristic green emission) of {TbTeW6} n, 100× greater than those of {Tb2Te2W37}, {Tb2Te2W34}, and {TbTeW17}, is explained by analysis of all 4 X-ray structures and multiple structure-intensity correlations.

Three Pd-decavanadates with a controllable molar ratio of Pd to decavanadate and their heterogeneous aerobic oxidation of benzylic C-H bonds.

By the combination of Pd-complexes and [V10O28]6-, three Pd-decavanadate compounds [Pd(NH3)4]3[V10O28]·8H2O (1), [Pd(deta)(H2O)]2(NH4)2[V10O28]·2H2O (2) (deta = diethylenetriamine) and [Pd(dpa)2](Hdpa)2(Et3NH)2[V10O28]·2H2O (3) (dpa = 2,2'-dipyridylamine) have been successfully synthesized and thoroughly characterized using single X-ray diffraction (SXRD), powder X-ray diffraction (PXRD), infrared spectroscopy (FT-IR) and elemental analyses (EA). Interestingly, in the three compounds, the molar ratios of Pd to decavanadate vary from 3 : 1 to 1 : 1 by changing N-ligands. The three Pd-decavanadates as heterogeneous catalysts are active in the aerobic oxidation of benzylic hydrocarbons under solvent-free conditions without adding any additives and co-catalysts. Moreover, compound 1 can be reused three times without losing its activity.

Immobilization of Keggin polyoxovanadoniobate in crystalline solids to produce effective heterogeneous catalysts towards selective oxidation of benzyl-alkanes.

Two ionic organic-inorganic hybrid compounds, [CuII(C2N2H8)2]4[CuII(C2N2H8)2(H2O)2]2[PNb12O40VVVIVO2]·(OH)2·11H2O (1) and [CoIII(C2N2H8)3]2[CoIII(C2N2H8)2(H2O)2]0.5[H2.5PNb12O40 VVVIVO2]·20H2O (2), based on P-centered dicapped polyoxoniobates and organometallic cations were isolated and structurally characterized by routine techniques. The trivalent cobalt complex-containing compound exhibits a looser arrangement compared with its divalent copper complex-containing counterpart, with a space volume of 34.9% for the former and 17.0% for the latter. The two compounds were proved to be effective in facilitating the oxidation of benzyl-alkanes to ketone products in a heterogeneous manner, evidencing the feasiblity of the strategy of self-immobilization of catalytically active, readily soluble PNb12O40(VO)2 species in crystalline solids.