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The internal functionalization of the Keplerate-type capsule Mo132 has been carried out by ligand exchange leading to the formation of glutarate and succinate containing species isolated as ammonium or dimethylammonium salts. Solution NMR analysis is consistent with asymmetric inner dicarboxylate ions containing one carboxylato group grafted onto the inner side of the spheroidal inorganic shell while the second hangs toward the center of the cavity. Such a disposition has been confirmed by the single-crystal X-ray diffraction analysis of the glutarate containing {Mo132} species. A detailed NMR solution study of the ligand-exchange process allowed determining the binding constant KL of acetate (AcO−), succinate (HSucc−) or glutarate (HGlu−) ligands at the 30 inner coordinating sites, which vary such as K [ABSTRACT FROM AUTHOR]

Two nanosized polyoxothiometalates were synthesized based on linking oxomolybdate building blocks with {Mo2O2S2}2+ groups. Remarkably, both compounds are formed selectively primarily upon changing the related concentrations in a logical way; they exhibit common structural features based on the same {Mo9O6S3}-type pores, which result in connections between {Mo6O21} pentagons and {Mo2O2S2}2+ linkers. Whereas the much larger spherical Mo132-type Keplerate contains twenty pores, the smaller Mo63-type cluster remarkably contains only two. The two compounds and a similar Keplerate exhibit interesting supramolecular properties related to interactions with the unusual predominantly apolar NMe4+ cations. Structural characterization of the Mo63-type compound reveals in the solid state a clathrate-like species that contains four NMe4+ cations embedded in two types of structurally well-adapted pockets. Related NMR spectroscopic investigations in solution using NMe4+ as the NMR spectroscopic probe are in agreement with the solid-state description. 1H NMR spectroscopic experiments (1D variable-temperature, 2D total correlation spectroscopy (TOCSY), exchange spectroscopy (EXSY), and diffusion-ordered spectroscopy (DOSY)) feature firmly immobilized and mobile NMe4+ ions in relationship with the type of host-guest arrangements. The use of the 1H NMR DOSY spectroscopic methodology has been successfully applied to track the interactions of the NMe4+ cations with the {Mo9O6S3} pores of a sulfurated Keplerate, thereby allowing the first quantitative analysis of this type of plugging process. The stability constant K=(210±20) mol−1 L is discussed related to the character of the process. [ABSTRACT FROM AUTHOR]

The last decade has see the development of sulfur-containing polyoxometalates (POTMs) as a subclass of the polyoxometalate family. The structural and physico-chemical properties of this emerging class of compounds is dominating by the striking coordination properties of the [MoOS(OH)] oxothio cation, used as a building block. The cyclic topology of this arrangement corresponds to the main feature of the {MoOS}-based compounds, able to develop cycle-based chemistry. The control of the linear oligomerization of the {MoOS} core is achieved by the presence of the anionic component, which acts as a template. Here, we report on recent examples which illustrate how the use of various template ions such as halide, sulfate, polyphosphate, and polycarboxylate anions allows to tune the nuclearity of the inorganic host from {Mo} to {Mo}. A special focus on behavior in solution is given, highlighting the dynamic and fluxional character of these host-guest systems. The Diffusion Ordered Spectroscopy (DOSY) H NMR, carried out on a large series of cycle-based and capsule-like compounds, demonstrates that such a method can be applied for the speciation of POM anions in solution. Finally, electrocatalytic behavior of the {MoOS}-based compounds is presented. Preliminary results show that the electrocatalytic reduction of protons into hydrogen (HER) could constitute one of the most relevant applications for this class of molecular compounds. [ABSTRACT FROM AUTHOR]

Incorporates sulfur atoms to Keggin analogues [PW11O39ME]4- (M = Nb, Ta, E = S, Se). Description of anion structure; Function of transition metal sulfides in commercial hydrotreating processes; Impact of thio fragment size on sandwich-type compound formation; Properties of heteropolyoxometalates.

Reaction of the [Mo2VS2O2]2+ oxothiocation with a stochiometric amount of C2O42− in water, at pH around 5, affords the novel anion [Mo6S6O6(OH)4(C2O4)3]4−. The structure has been solved by single-crystal X-ray diffraction and consists in a six-membered incomplete wheel encapsulating a template oxalate anion and showing two external bridging oxalate ligands. In the solid state, two potassium ions bound to the terminal oxygen atoms of the [Mo6S6O6(OH)4(C2O4)3]4− anion direct the formation of a 1D chain. The four members of this family of products obtained by condensation of the oxothiocation with oxalate ligands are thus now perfectly characterized and can be easily distinguished by infrared spectroscopy. [Copyright &y& Elsevier]

The high-nuclearity polyoxothiomolybdate [H8Mo84S48O188(H2O)12(CH3COO)24]32- has been prepared and characterized by single-crystal X-ray crystallography and ¹H NMR, IR, Raman, and UV-vis spectroscopy. The solid-state structure reveals an unprecedented and intriguing arrangement consisting of a nanoscaled anionic cube. The surprisingly open structure of this {Mo84}-type cubic box features a large inner void that is accessible via its six open square faces with diameters of ca. 9 Å. Importantly, this molecular system appears to be highly functionalizable because of the presence of 24 exposed exchangeable acetate ligands. [ABSTRACT FROM AUTHOR]

Reaction of the cyclic lacunary [H7P8W48O184]33- anion (noted P8W48) with the [Mo2S2O2(H2O)6]2+ oxothiocation led to two compounds, namely, [K4{Mo4O4S4(H2O)3(OH)2}2(WO2)(P8W48O184)]30- (denoted 1) and [{Mo4O4S4(H2O)3(OH)2}2(P8W48O184)]36- (denoted 2), which were characterized in the solid state and solution. In the solid state, the structure of [K4{Mo4O4S4(H2O)3(OH)2}2(WO2)(P8W48O184)]30- reveals the presence of two disordered {Mo4O4S4(H2O)3(OH)2}2+ "handles" connected on both sides of the P8W48 ring. Such a disorder is consistent with the presence of two geometrical isomers where the relative disposition of the two {Mo4O4S4(H2O)3(OH)2}2+ handles are arranged in a perpendicular or parallel mode. Such an interpretation is fully supported by 31P and 183W NMR solution studies. The relative stability of both geometrical isomers appears to be dependent upon the nature of the internal alkali cations, i.e., Na+ vs K+, and increased lability of the two {Mo4O4S4(H2O)3(OH)2}2+ handles, compared to the oxo analogous, was clearly identified by significant broadening of the 31P and 183W NMR lines. Solution studies carried out by UV-vis spectroscopy showed that formation of the adduct [{Mo4O4S4(H2O)3(OH)2}2(P8W48O184)]36- occurs in the 1.5-4.7 pH range and corresponds to a fast and quantitative condensation process. Furthermore, 31P NMR titrations in solution reveal formation of the "monohandle" derivative [{Mo4O4S4(H2O)3(OH)2}(P8W48O184)]38- as an intermediate prior to formation of the "bishandle" derivatives. Furthermore, the electrochemical behavior of [{Mo4O4S4(H2O)3(OH)2}2(P8W48O184)]36- was studied in aqueous medium and compared with the parent anion P8W48. [ABSTRACT FROM AUTHOR]

Abstract: The self-condensation of the [Mo2O2E2]2+ precursors is at the origin of a family of discrete cyclic species. The condensation can be performed in the presence or not of guest species. With E=O, the resulting cycles delimit an anionic open cavity, which can be filled by neutral polar molecules such as aquo ligands, or by alkaline cations. With E=S, the resulting cycles delimit a cationic cavity, which can be filled with neutral molecules, or anions like halides or more sophisticated groups like caboxylates. The flexibility of the rings is at the origin of striking host–guest properties: the symmetry and the nuclearity of the inorganic backbone are directed by the size and shape of the encapsulated guest. The metal coordination versatility confers to the ring unusual dynamic properties. In the solid state, molecular rings arrange in striking 3-D networks in which alkaline cations organize in pillars or layers decorated with anionic rings. The control of the partial occupancy of the cationic pillars permits to synthesize very good ionic conductors. To cite this article: F. Sécheresse et al., C. R. Chimie. 8 (2005) . [Copyright &y& Elsevier]

[(PW[sub 11]O[sub 39])[sub 2](Mo[sub 4]S[sub 4]O[sub 4](OH[sub 2])[sub 2])][sup 10-] anions were obtained through the stereospecific addition of the [Mo[sub 2]S[sub 2]O[sub 2]][sup 2+] oxothiocation to the monovacant α-[PW[sub 11]O[sub 39]][sup 7-] anion. K[sub 10][(PW[sub 11]O[sub 39])[sub 2]Mo[sub 4]S[sub 4]O[sub 4](OH[sub 2])[sub 2])]·25H[sub 2]O has been isolated as crystals and characterized by X-ray diffraction. The structure revealed a "sandwich-like" dimer of two α-[PW[sub 11]O[sub 39]][sup 7-] subunits assembled by the noteworthy central cluster {H[sub 4]Mo[sub 4]S[sub 4]O[sub 6]}. The crystallization of the crude product produces an isomerically pure compound, which was characterized by [sup 31]P and [sup 183]W NMR. IR data were also supplied. In solution, the compound isomerizes, giving a second diastereoisomer. A kinetic experiment, carried out by [sup 31]P NMR, allowed the conditions of the thermodynamic equilibrium to be determined. A structural relationship between the two isomers is proposed, fully consistent with NMR data. Cisoid and transoid isomers result in the relative disposition of each [PW[sub 11]O[sub 39]][sup 7-] subunit, either staggered or eclipsed. An investigation of the formation of the [Mo[sub 2]O[sub 2]S[sub 2]][sup 2+] unit from the polycondensed cyclic precursor [Mo[sub 10]S[sub 10]O[sub 10](OH)[sub 10](H[sub 2]O)[sub 5]] and the aggregation process resulting in the oxothio [(PW[sub 11]O[sub 39])[sub 2](Mo[sub 4]S[sub 4]O[sub 4](OH[sub 2])[sub 2])][sup 10-] compound has been undertaken. The studies were monitored by [sup 31]P NMR and UV-vis spectroscopies. The reaction is quantitative in nearly stoichiometric conditions. [ABSTRACT FROM AUTHOR]