The novel chain‐like anion ∞1[NaMo8O26(mim)2]3− in (Hmim)3[NaMo8O26(mim)2] (mim is 1‐methylimidazole)

Tris(1‐methylimidazolium) bis(1‐methylimidazole)hexacosaoxidooctamolybdatesodium, (C₄H₇N₂)₃[NaMo₈O₂₆(C₄H₆N₂)₂], prepared from an aqueous solution containing Na₂MoO₄ and 1‐methylimidazole, contains the novel chain‐like anion _∞¹[NaMo₈O₂₆(mim)₂]^{3 −} (mim is 1‐methylimidazole). The [Mo₈O₂₆(mim)₂]⁴⁻ building unit, which lies across a center of inversion, is comprised of eight edge‐sharing MoO₆ and MoO₅(N_mim) octahedra. These molybdate units are interlinked by sodium, itself exhibiting a sixfold coordination with O atoms.     

The Reaction of Molybdenum with 2,3-Dihydroxynaphthalene

[H2N（CH2）3NH312[MoO2（C10H6O2）2] （1） was synthesized by the 2,3-dihydroxynaphthalene in the mixed solvent of CH3OH, CH3CN reaction of （n-Bu4N）4[Mo8O26] with and 1,3-propanediarnine. （C5HllN2）2- [HeN（CH2）3NH2][MoO2（CloH6O2）2] （2） was obtained by the reaction of Na2MoO4.2H20 with 2,3-dihydroxynaphthalene in the same solvent above. Both of the complexes possess complex anion [Mo（VI）O2（OC10H6O）2]^2- which shows pseudo-octahedrally coordinated fashion, while the counterions are two protonated 1,3-propanediamine in complex 1 and （CsH11N2）^＋ in complex 2. （C5H11N2）＋ is the byproduct of reaction 2, which results from combination of acetonitrile with 1,3-propanediamine. Packing diagrams of the two complexes are also different. There is anti-parallel-aligned-double-meso-bilayer unit in complex 1. However there are four chiral anions arranged in anticlockwise orientation in complex 2.     

Mass spectrometry of metal compounds. III. Electron-impact-induced mass spectrometric studies of bis(acetylacetonato)dioxomolybdenum(VI), MoO2(C5H7O2)2, and tetrakis(acetylacetonato)dioxo-μ-oxodimolybdenum(V), Mo2O3(C5H7O2)4

Electron-impact-induced mass spectra of MoO₂(C₅H₇O₂)₂, 1, and Mo₂O₃(C₅H₇O₂)₄, 2, recorded at an ion-source temperature of 100°C show the molecular ion signals at m/z 328 and at m/z 636, respectively, indicating that they do not undergo association in the vapour state. The parent ion of 1, unlike bis(acetylacetonato)metalates of the first-row transition metals, loses (CH₂CO followed by C₃H₅O to produce [MoO₂(C₅H₇O₂)]⁺ at m/z 229, the base peak, which ultimately fragments to [MoO₂]⁺. The molecular ion of 2, [Mo₂O₃(C₅H₇O₂)₄]⁺, undergoes fragmentation following two different, but equally probable, pathways with one involving the loss of C₅H₇O₂ and C₅H₇O groups producing the ion [Mo₂O₄(C₅H₇O₂)₂]⁺, and the other involving the formation of the ion [MoO(acac)₂]⁺ directly from the parent ion. The signal at m/z 312 owing to the ion [MoO(C₅H₇O₂)₂]⁺ constitutes the base peak in the spectrum of 2. Metastable transitions were studied, and the most probable fragmentation schemes for the compounds 1 and 2 are suggested. There is evidence for CH₃ shift from the ligand to the oxygen atoms bound to the metal centres or to form metal-carbon bonds.     

Synthesis and structure of two molybdovanadates containing coordinatively bound oxalato ligands: (NH4)6[Mo6V2O24(C2O4)2]·6H2O and (NH4)4[H2Mo2V2O12(C2O4)2]·2H2O

The compounds (NH₄)₆[Mo₆V₂O₂₄(C₂O₄)₂]·6H₂O (I) and (NH₄)₄[H₂Mo₂V₂O₁₂(C₂O₄)₂]·2H₂O (II) have been prepared from molybdenum(VI) oxide and ammonium vanadate in aqueous solution through the addition of ammonium oxalate, and their structures determined by X-ray structure analysis. Whereas the molybdovanadate anion [Mo₆V₂O₂₄(C₂O₄)₂]⁶⁻ found in (I) consists of six MoO₆ and two VO₆ edge-sharing octahedra of the γ-[Mo₈O₂₆]⁴⁻ type structure, the tetranuclear anion [H₂Mo₂V₂O₁₂(C₂O₄)₂]⁴⁻ of (II) adopts the structure with a M₄O₁₆ core. Both complexes contain bidentate oxalato ligands bonded to the vanadium ions. In both crystal structures the molybdovanadate anions are mutually hydrogen bonded by ammonium ions and water molecules.     

Hydrothermal syntheses and crystal structures of two organic–inorganic hybrid molybdovanadates based on [V2Mo6(OH)2O24]4− and [VMo12O40]3− polyoxoanions

Two new organic–inorganic hybrid cobalt-molybdovanadates [Co(phen)₃]H₂[H₂V₂Mo₆O₂₆] · 7H₂O (1) and [Co(2,2′-bipy)₃][Na(H₂O)₇][VMo₁₂O₄₀] (2) have been hydrothermally synthesized and structurally characterized by elemental analyses, IR, UV, XPS spectroscopy, thermogravimetric (TG) analyses, and X-ray single crystal diffraction. The molecular structure of 1 consists of a [V₂Mo₆(OH)₂O₂₄]^4? polyoxoanion, a [Co(phen)₃]²⁺, two H⁺ and seven lattice water molecules. The structure of [V₂Mo₆(OH)₂O₂₄]^4? consists of six MoO₆ octahedra and two VO₄ tetrahedra; six MoO₆ octahedra are linked by edge-sharing oxygens forming a {Mo₆} ring, and two VO₄ tetrahedra cap opposite sides of the {Mo₆} ring. The molecular structural unit of 2 is constructed from a typical Keggin-type [VMo₁₂O₄₀]^3? polyoxoanion and a [Co(2,2′-bipy)₃]²⁺ cation and a Na⁺ countercation; Co²⁺ is coordinated by six nitrogens from three 2,2′-bipyridines forming a distorted octahedron.     

Neue Oxooxalatokomplexe des Molybdän(VI)

New Osooxalatocomplexes of Molybdenum (VI) The preparation of the compounds Cs₂[Mo₂O₅F₂(C₂O₄)] · H₂O and Cs₂[Mo₂O₄Cl₄(C₂O₄)] · 2 H₂O is reported. The structure of the complex anions, which are containing quadridentated oxalate ligands, is derived from their vibration spectra. The compounds [NR₄]₂[Mo₂O₄F₄(C₂O₄)] with R = CH₃ and C₂H₅ are examined for comparison.     

Compounds of molybdenum(VI) with aspartic acid: A spectrophotometric and potentiometric study of the formation and interconversion equilibria in aqueous solution

Summary Addition of Na₂MoO₄ to an excess of aspartic acid (AspH₂) can produce any of four different complexes depending on the pH, namely [MoO₃(Asp)]^2–, [Mo₂O₅(Asp)₂]^2–, [Mo₂O₄(OH)(Asp)₂]^– and [Mo₂O₄(Asp)₂]. The ranges of formation of these species with pH, the number of equivalents of acid necessary for their formation, and their stoichiometries, condensation degrees and stability constants, have been calculated by potentiometric and spectrophotometric techniques. The aspartic acid acts as a tridentate ligand in all cases.     

Synthesis and crystal structure of (H3O)2{(Na2(OH)CB[5])2[HV4O12]}Cl · 14H2O

The compound (H₃O)₂{(Na₂(OH)CB[5])₂[HV₄O₁₂]}Cl · 14H₂O is synthesized by heating (120°C) of a mixture of sodium vanadate, cucurbit[5]uril (CB[5]), rubidium chloride, and water in a sealed ampule. According to the X-ray diffraction data, the binding of the [Na₂(OH)]⁺ binuclear cation with CB[5] occurs due to the bidentate coordination of the oxygen atoms of the portals of cucurbit[5]uril to the sodium atoms. The tetranuclear vanadium complex [HV₄O₁₂]^3? serves as a bridge, joining infinite chains {Na₂(OH)CB[5]} _∞ ⁺ in pairs.     

Molybdenum Bisphosphonates with Cr(III) or Mn(III) Ions

The synthesis of Mo^VI bisphosphonates (BPs) complexes in the presence of a heterometallic element has been studied. Two different BPs have been used, the alendronate ligand, [O₃PC(C₃H₆NH₃)(O)PO₃]^4? (Ale) and a new BP derivative with a pyridine ring linked to the amino group, [O₃PC(C₃H₆NH₂CH₂C₅H₄N)(O)PO₃]^4? (AlePy). Three compounds have been isolated, a tetranuclear Mo^VI complex with Cr^III ions, (NH₄)₅[(Mo₂O₆)₂(O₃PC(C₃H₆NH₃)(O)PO₃)₂Cr]·11H₂O (Mo₄(Ale)₂Cr), its Mn^III analogue, (NH₄)_4.5Na_0.5[(Mo₂O₆)₂(O₃PC(C₃H₆NH₃)(O)PO₃)₂Mn]·9H₂O (Mo₄(Ale)₂Mn), and a cocrystal of two polyoxomolybdates, (NH₄)₁₀Na₃[(Mo₂O₆)₂(O₃PC(C₃H₆NH₂CH₂C₅H₄N)(O)PO₃)₂Cr]₂[CrMo₆(OH)₆O₁₈]·37H₂O ([Mo₄(AlePy)₂Cr]₂[CrMo₆]). In this latter compound an Anderson-type POM [CrMo₆(OH)₆O₁₈]^3? is sandwiched between two tetranuclear Mo^VI complexes with AlePy ligands. The protonated triply bridging oxygen atoms bound to the central Cr^III ion of the Anderson anion develop strong hydrogen bonding interactions with the oxygen atoms of the bisphosphonate complexes. The UV–Vis spectra confirm the coexistence in solution of both POMs. Cyclic voltammetry experiments have been performed, showing the reduction of the Mo centers. In strong contrast with the reported Mo^VI BP systems, the presence of trivalent cations in close proximity to the Mo^VI centers dramatically impact the potential solid-state photochromic properties of these compounds.     

Chemistry of oxomolybdenum(V) and (VI) complexes incorporating oxygen,nitrogen and/or sulfur donor atoms. Part 1. Synthesis and characterization of [Mo2O3L4] (LH = HSCH2CH2CO2H,HSCH2CO2Me or HSCH2CH2CO2Me) and [MoO2L′2] (L′H = HOC6H4NH2, HOCH2C6H4NH2, HOC6H4CHO or HOC10H8N)

Reactions of an acidified aqueous solution of Na₂MoO₄ · 2H₂O with 3-mercaptopropionic acid, 2-mercaptomethylethanoate and 3-mercaptomethyl propanate yield blue oxo-bridged Mo^V complexes of the type [Mo₂O₃L₄], whereas corresponding reactions with 2-aminophenol, 2-aminobenzyl alcohol, salicylaldehyde and 2-methyl-8-hydroxyquinoline, yield yellow dioxomolybdenum(VI) complexes, [MoO₂L′₂]. All these coloured solids are sparingly soluble, even in coordinating solvents. They have been characterized by elemental and spectroscopic analysis.     

Effects of alkali metal ions on the thermal decomposition of ammonium heptamolybdate tetrahydrate

The thermal decomposition of pure ammonium heptamolybdate tetrahydrate (AHMT), and doped with Li⁺, Na⁺ and K⁺ ions was investigated using thermogravimetry, differential thermal analysis, infrared and X-ray diffraction techniques. Results obtained revealed that the decomposition of AHMT proceeded in three decomposition stages in which both NH₃ and H₂O were released in all stages. The presence of 0.5 mol % alkali metal ions enhances the formation of the intermediateb (NH₄)₂MO₇O₂₂·2H₂O while the decomposition of this intermediate into MoO₃ is slightly affected in the presence of all dopant concentrations used. The infrared absorption spectra of the thermal products of AHMT treated with 10 mol% alkali metal ions (AMI) at 350°C indicated a reduction of some Mo⁶⁺ ions. By heating of AHMT above 500°C in presence of 5 or 10 mol % of AMI, a solid-solid interaction between alkali metal oxides and MoO₃ giving rise to well crystallized alkali metal molybdates. finally the activation energies accompanied various decomposition stages were calculated.     

Was ist „Molybdänsäure”︁ oder „Polymolybdänsäure”︁?

What is “Molybdic Acid” or “Polymolybdic Acid”? According to a comparative study of the literature, supplemented by well-aimed experimental investigations and equilibrium calculations, the terms “molybdic acid” or “polymolybdic acid”, used for many substances, species, or solutions in the literature, are applicable to a species, a solution, and two solids:

• a) The monomeric molybdic acid, most probably having the formula MoO₂(OH)₂(H₂O)₂(? H₂MoO₄, aq), exists in (aqueous) solution only and never exceeds a concentration of ≈ 10^?3 M since at higher concentrations it reacts with other monomemeric molybdenum (VI) species to give anionic or cationic polymers.
• b) A concentrated (>0.1 M Mo^VI) aqueous molybdate solution of degree of acidification P = 2 (realized, e. g., by a solution of one of the Mo^VI oxides; by any molybdate solutions whose cations have been exchanged by H₃O⁺ on a cation exchanger; by suitable acidification of a molybdate solution) contains 8 H₃O⁺ and the well-known polyanion Mo₃₆O₁₁₂(H₂O)₁₆^8? exactly in the stoichiometric proportions.
• c) A glassy substance, obtained from an alkali metal salt-free solution prepared according to (b), refers to the compound (H₃O)₈[Mo₃₆O₁₁₂(H₂O)₁₆]·xH₂O, x = 25—29.
• d) A solid having the ideal composition [(H₃O)Mo₅O₁₅(OH)H₂O·H₂O]∞ consists of a polymolybdate skeleton (the well-known ?decamolybdate”? structure), in the tunnels of which H₃O⁺ and H₂O are intercalate. The structure is very unstable if only H₃O⁺ cations are present, but it is enormously stabilized by a partial exchange of H₃O⁺ by certain alkali or alkaline earth metal cations.

For the compounds MoO₃, MoO₃·H₂O, and MoO₃·2H₂O the term ?molybdic acid”? is unjustified. The commercial product ?molybdic acid, ≈85% MoO₃”? is the well-known polymolybdate (NH₄)₂O·4 MoO₃ with a layer structure of the polyanion.     

Synthesis and crystal structure of a supramolecular adduct of trinuclear molybdenum oxocluster with macrocyclic cavitand cucurbit[5]uril containing the included ionic associate Na<Superscript>+</Superscript>...Cl...Na<Superscript>+</Superscript>

The compound of composition [{Mo₃O₄(H₂O)₆Cl₃}₂(Na₂Cl⊂ C₃₀H₃₀N ₂₀O₁₀)]Cl₃⋅14H₂O (1) was prepared by evaporation of a hydrochloric acid solution containing NaCl, the trinuclear aqua complex [Mo₃O₄(H₂O)₉]⁴⁺, and the macrocyclic cavitand cucurbit[5]uril (C₃₀H₃₀N₂₀O₁₀). X-ray diffraction analysis demonstrated that the cucurbit[5]uril molecule is closed on both sides by the cluster cations through hydrogen bonding between the CO groups of the cucurbit[5]uril portals and the aqua ligands of the oxo cluster. The inner cavity of the supramolecular adduct includes an unusual ionic associate Na⁺...Cl...Na⁺. The sodium cations are coordinated by five carbonyl oxygen atoms of each portal of the macrocycle. Compound 1 is the first structurally characterized complex, in which the macrocyclic cucurbit[5]uril ligand is directly coordinated to the alkali metal cation. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1513–1517, July, 2005.     

Synthesis of Molybdovanadates Coordinated by Oxalato Ligands. The Crystal Structure of K6[Mo6V2O24(C2O4)2]·6H2O

The oxalato complex of a polyoxomolybdovanadate, K₆[Mo₆V₂O₂₄(C₂O₄)₂]·6H₂O has been obtained by reaction of potassium molybdate, ammonium vanadate and tartaric or ascorbic acid. Such conversion of dicarboxylate into oxalate ions indicates the catalytic role of molybdenum. Complexes of analogous composition also were obtained in the reactions of MoO₃, V₂O₅ and potassium oxalate, or M ₂CO₃ (M = Rb, Cs) and oxalic acid. The centrosymmetrical molybdovanadate anion [Mo₆V₂O₂₄(C₂O₄)₂]^6- consists of six MoO₆ and two VO₆ edge-sharing octahedra to give the n -[Mo₆O₂₆]^4- structure. All complexes were characterized by powder and single crystal X-ray analyses, ESR and IR spectra and TG and DSC measurements.     

Cuboidal oxalate cluster complexes with the Mo<Subscript>3</Subscript>CuQ<Subscript>4</Subscript><Superscript>5+</Superscript> cluster core (Q = S or Se): synthesis,structure, and electrochemical properties

The reactions of the [Mo₃(μ₃-Q)(μ₂-Q)₃(H₂O)₃(C₂O₄)₃]²⁻ complex (Q = S or Se) with CuX salts (X = Cl, Br, I, or SCN) in water produce the cuboidal heterometallic clusters [Mo₃(CuX)(μ₃-Q)₄(H₂O)₃(C₂O₄)₃]²⁻, which were isolated as the potassium and tetraphenylphosphonium salts. Two new compounds, K₂[Mo₃(CuI)(μ₃-S)₄(H₂O)₃(C₂O₄)₃]·6H₂O and (PPh₄)₂[Mo₃(CuBr)(μ₃-S)₄(H₂O)₃(C₂O₄)₃]·7H₂O, were structurally characterized. All compounds were characterized by elemental analysis and IR spectroscopy. The K₂[Mo₃(CuI)(μ₃-Se)₄(H₂O)₃(C₂O₄)₃] compound was characterized by the ⁷⁷Se NMR spectrum; the (PPh₄)₂[Mo₃(CuI)(μ₃-S)₄(H₂O)₃(C₂O₄)₃], (PPh₄)₂[Mo₃(CuI)(μ₃-Se)₄(H₂O)₃(C₂O₄)₃] and K₂[Mo₃(CuSCN)(μ₃-S)₄(H₂O)₃(C₂O₄)₃]·7H₂O compounds, by electrospray mass spectra. Dedicated to Academician G. A. Abakumov on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1639–1644, September, 2007.     

catena‐Poly­[[heptakis­(di­methyl­form­amide‐κO)­di‐μ4‐oxo‐tetra‐μ3‐oxo‐hexa­deca‐μ2‐oxo‐tetra­oxo­lan­than­um(III)­octamolybdenum(IV)]‐μ‐sodium(I)]

The title compound, [NaLaMo₈O₂₆(C₃H₇NO)₇]_n, contains infinite chains of [Mo₈O₂₆]⁴⁻ units supporting di­methyl­form­amide‐coordinated La^III cations and linked by Na⁺ cations. The lanthanum center adopts a nine‐coordinate geometry and the Na atom is sandwiched between two β‐[Mo₈O₂₆]⁴⁻ units.     

Bis(iminodiethylenedi­ammonium) di‐μ5‐hydrogen­phosphato‐penta­molybdate(VI) tetra­hydrate

The crystal structure of the title compound, (C₄H₁₅N₃)₂[Mo₅O₁₅(HPO₄)₂]·4H₂O, is made up of [Mo₅O₁₅(HPO₄)₂]⁴⁻ clusters, iminodiethylenediammonium cations and solvent water mol­ecules. The [Mo₅O₁₅(HPO₄)₂]⁴⁻ cluster, with approximate C₂ symmetry, can be considered as a ring formed by five distorted edge‐ and corner‐sharing MoO₆ octa­hedra, capped on both poles by a hydro­phosphate tetra­hedron. There exist N—H⋯O, O—H⋯N and C—H⋯O hydrogen bonds between the organic ammonium groups and the clusters, with inter­atomic N⋯O distances ranging from 2.675 (3) to 2.999 (3) Å, and C⋯O distances ranging from 3.139 (5) to 3.460 (5) Å.     

Investigations on the formation of rubidium dimolybdate via thermal decomposition of rubidium oxomolybdenum(VI) oxalate

The complex Rb₂[Mo₂O₅(C₂O₄)₂(H₂O)₂] (RMO) was prepared and characterized by means of chemical analysis and IR spectral studies. Its thermal decomposition was studied by using TG and DTA techniques. RMO loses its water between 160 and 200°C, this immediately being followed by the decomposition of anhydrous RMO, which takes place in three stages. The first two stages occur in the temperature ranges 200–220 and 220–255°, to give intermediates with tentative compositions Rb₈[Mo₈O₂₂(C₂O₄)₆] and Rb₈[Mo₈O₂₆(C₂O₄)(CO₃)], respectively, the latter then decomposing in the third stage between 255 and 340° to give the end-product, rubidium dimolybdate (Rb₂Mo₂O₇). Thed spacings for Rb₂Mo₂O₇ are given for 2θ values between 10 and 70°.     

Organic‐Inorganic Hybrids: Preparation and Structural Characterization of (Bu4N)2[Mo6O17(NAr)2] and (Bu4N)2[Mo6O18(NAr)] (Ar = o‐CH3C6H4)

In the presence of N, N′‐dicyclohexylcarbodiimide (DCC), (Bu₄N)₂[Mo₆O₁₈(NAr)] ( 1 ) and (Bu₄N)₂[Mo₆O₁₇(NAr)₂] ( 2 ), Ar = o‐CH₃C₆H₄, have been synthesized via the reaction of [α‐Mo₈O₂₆]^4— with o‐toluidine. If the hydrochloride salt of o‐toluidine was added into the reactive mixture, only the monofunctionalized imido derivative of [Mo₆O₁₉]^2— was obtained; the bifunctionalized derivative of [Mo₆O₁₉]^2— was exclusively synthesized in the presence of non‐protonated o‐toluidine. The molecular and crystal structures of the hybrid compounds 1 and 2 were determined by X‐ray single crystal diffraction, and their UV, IR and NMR spectra were compared. Additionally, a possible reaction mechanism was proposed.     

CO2 fixation by [WIVO(S2C2(CN)2)2]2?: functional model for the tungsten-formate dehydrogenase of Clostridium thermoaceticum

(NEt₄)₂[W^IVO(S₂C₂(CN)₂)₂] (1), isolated by reaction of Na₂ WO₄, Na₂S₂C₂(CN)₂ (Na₂mnt) in acidified (pH5.5) aqueous medium in the presence of excess of sodium dithionite and NEt₄Br, reduces CO₂/HCO ₃ ⁻ (pH 7.5) to yield HCOO⁻ and (NEt₄)₂[W^VIO₂(S₂C₂(CN)₂)₂] (2) mimicking tungsten-formate dehydrogenase (W-FDH) activity. (1) reacts with Na₂MoO₄ in acidic medium to produce [Mo^IvO(S₂C₂(CN)₂)₂]²⁻ implicating the displacement of tungsten by molybdenum from the cofactor complex in W-FDH.