Discovery of Heteroatom‐“Embedded” Te⊂{W18O54} Nanofunctional Polyoxometalates by Use of Cryospray Mass Spectrometry

The cryo game : Heteroatom‐embedded nanofunctional clusters are described that incorporate a [Te^VIO₆]^6? species contained within a {W₁₈O₅₄} cage. Not only does the tellurium‐based species activate the {W₁₈O₅₄} cluster surface for assembly of larger nanoscale structures, such as [H₁₀Te^VI₂W₅₈O₁₉₈]^26?, it also undergoes a redox transformation inside the cluster from [Te^VIO₆]^6? to [Te^IVO₃]^2?.

     

The Mixed Gold–Palladium Polyoxo‐Noble‐Metalate [NaAuIII4PdII8O8(AsO4)8]11−

The first fully inorganic, discrete gold–palladium–oxo complex [NaAu^III₄Pd^II₈O₈(AsO₄)₈]^11? has been synthesized in aqueous medium. The combination of single‐crystal XRD, elemental analysis, mass spectrometry, and DFT calculations allowed establishing the structure and composition of the novel polyanion, and UV/Vis studies suggest that it is stable in neutral aqueous media.     

Electroactive Benzothiazole Hydrazones and Their [Mo6O19]2− Derivatives: Promising Building Blocks for Conducting Molecular Materials

The electroactive benzothiazole hydrazone AMBTH–H₂, a new member of the 2,2′‐azino‐bis(N‐alkylbenzothiazole) family, was synthesised in a five‐step procedure and characterised by using X‐ray diffraction along with two intermediates and the N‐methylbenzothiazole hydrazone MBTH–H₂. Both AMBTH–H₂ and MBTH–H₂ were coupled to [Mo₆O₁₉]^2? in acetonitrile in the presence of dicyclohexylcarbodiimide and dimethylaminopyridine to give two new diazoalkane–hexamolybdates, which were isolated as tetrabutylammonium salts and characterised by using IR, UV/Vis and NMR spectroscopies, cyclic voltammetry and, for one of them, X‐ray diffraction. The packing arrangement molecules in crystals of AMBTH–H₂, the redox features of the AMBTH–hexamolybdate hybrid together with a good electronic communication between the organic π system and the molybdenum centres make these compounds very promising blocks for the synthesis of conducting molecular materials.     

New organosilyl derivatives of the Dawson polyoxometalate [alpha2-P2W17O61(RSi)2O]6-: synthesis and mass spectrometric investigation

In the field of functionalized polyoxometalates, organosilyl derivatives of polyoxotungstate constitute a special class of hybrid organic-inorganic system. The first organosilyl derivative of the monovacant Dawson heteropolyoxotungstate [alpha2-P2W17O61]10- was obtained by three different methods. The use of two organosilanes as reagents enabled the preparation of the functionalized polyoxometalate [alpha2-P2W17O61(RSi)2O]6- in good yield. Electrospray (ESI-MS) and matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry, and 183W, 31P, and 29Si NMR spectroscopy were used to characterize the composite systems. In several cases, ESI-MS analyses generated reduction processes which were compared to those related to [PMo11VO40]4-, the highly reducible Keggin polyoxometalate.     

Titanium‐Substituted Polyoxotantalate Clusters Exhibiting Wide pH Stabilities: [Ti2Ta8O28]8− and [Ti12Ta6O44]10−

Two new substituted polyoxotantalate clusters, [Ti₂Ta₈O₂₈]^8? and [Ti₁₂Ta₆O₄₄]^10?, considerably expand the pH range where tantalates persist in aqueous solution. The structures of [Ti₂Ta₈O₂₈]^8? and [Ti₁₂Ta₆O₄₄]^10? are reported as tetramethylammonium salts after synthesis at hydrothermal conditions in aqueous solution. These Ti‐substituted polyoxotantalate clusters have analogues among recently discovered niobates, but are slightly larger and more persistent in solution. Most importantly, they exhibit a much wider range of pH stability than the familiar hexatantalate cluster, which is the only other tantalate known to be stable at highly basic pH conditions. These molecules are kinetically stable to near‐neutral pH, making them excellent synthons for further development into materials and catalysts, and an significant advance in adapting tantalates for use in aqueous solutions.     

Molecular Salt Effects in the Gas Phase: Tuning the Kinetic Basicity of [HCCLiCl]− and [HCCMgCl2]− by LiCl and MgCl2

A combination of gas‐phase ion–molecule reaction experiments and theoretical kinetic modeling is used to examine how a salt can influence the kinetic basicity of organometallates reacting with water. [HC?CLiCl]^? reacts with water more rapidly than [HC?CMgCl₂]^?, consistent with the higher reactivity of organolithium versus organomagnesium reagents. Addition of LiCl to [HC?CLiCl]^? or [HC?CMgCl₂]^? enhances their reactivity towards water by a factor of about 2, while addition of MgCl₂ to [HC?CMgCl₂]^? enhances its reactivity by a factor of about 4. Ab initio calculations coupled with master equation/RRKM theory kinetic modeling show that these reactions proceed via a mechanism involving formation of a water adduct followed by rearrangement, proton transfer, and acetylene elimination as either discrete or concerted steps. Both the energy and entropy requirements for these elementary steps need to be considered in order to explain the observed kinetics.     

ChemInform Abstract: Structural and Vibrational Study of [Mo7O24]6‐ and [W7O24]6‐.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

Grafting of Secondary Diolamides onto [P2W15V3O62]9− Generates Hybrid Heteropoly Acids

The Dawson tungstovanadate [P₂W₁₅V₃O₆₂]^9? can be grafted to secondary diolamides. The electron‐withdrawing character of the polyanion increases the acidity of the amide proton, leading to an organo‐polyoxometalate, which can be used as a Brønsted organocatalyst. High‐field NMR and DFT modeling indicate that the amide proton stays on the nitrogen and that the exalted acidity derives from the interaction between the organic and inorganic parts of the organo‐polyoxometalate. The amide‐inserted vanadotungstates thus form a new family of (hybrid) heteropolyacids, offering new perspectives for the application of POM‐based catalysis in organic synthesis.     

Sensing the chirality of Dawson lanthanide polyoxometalates [alpha1-LnP2W17O61]7- by multinuclear NMR spectroscopy

Lanthanide complexes of the chiral Dawson phosphotungstate [alpha(1)-P(2)W(17)O(61)](10-) were used to study the formation of diastereomers with optically pure organic ligands. The present work started with the full assignment of the (183)W NMR spectra of [alpha(1)-Yb(H(2)O)(4)P(2)W(17)O(61)](7-) at different temperatures and concentrations, which allowed the structure of the dimerized form in aqueous solution to be established. Different enantiopure amino acids and phosphonic acids were screened as ligands. Both types allowed chiral differentiation by multinuclear NMR spectroscopy under fast-exchange conditions. Functional groups with a good affinity for the oxo framework of the polyoxometalate were identified, and maps of the interactions between L-serine and N-phosphonomethyl-L-proline with [alpha(1)-Yb(H(2)O)(4)P(2)W(17)O(61)](7-) were established. This demonstrates the power of (183)W NMR spectroscopy to elucidate the molecular recognition of inorganic molecules by organic compounds. N-Phosphonomethyl-L-proline appears to be a convenient ligand to promote separation of the diastereomers and ultimately resolution of the enantiomers of [alpha(1)-Yb(H(2)O)(4)P(2)W(17)O(61)](7-).     

Direct Observation by Electrospray Ionization Mass Spectrometry of [Cp*RhMo3O8(OMe)5]−, a Key Intermediate in the Formation of the Double-Bookshelf-Type Oxide Cluster [(Cp*Rh)2Mo6O20(OMe)2]2−

The use of methanol as solvent is essential for the formation of the double-bookshelf-type oxide cluster [(Cp*Rh)₂Mo₆O₂₀(OMe)₂]²⁻ from [{Cp*Rh(μ-Cl)Cl}₂] and four equivalents of [Mo₂O₇]²⁻. The reaction proceeds via [Cp*RhMo₃O₈(OMe)₅]⁻. The proposed structure for this key intermediate (shown schematically) is supported by electrospray ionization mass spectrometry and labeling experiments with CD₃OD as solvent. Cp*=η⁵-C₅Me₅.