Three 2,2′-biimidazole transition metal complex-supported octamolybdates derived from hexamolybdochromate

Three octamolybdate compounds, namely [Cu(H₂biim)₂]₂[β-Mo₈O₂₆{Cu(H₂biim)₂}₂][β-Mo₈O₂₆] (1), [{Fe(H₂biim)₂(Hbiim)}₂(γ-Mo₈O₂₆)]·5H₂O (2), and [{Co(H₂biim)₂(Hbiim)}₂(γ-H₂Mo₈O₂₆)]·5 H₂O (3) (H₂biim = 2,2′-biimidazole) have been hydrothermally synthesized from the reaction of mixtures of hexamolybdochromate ({CrMo₆}), transition metal, and H₂biim in acetate buffer solution, and characterized by physico-chemical and spectroscopic methods. They represent the first examples of the conversion of hexamolybdochromate to octamolybdate. Single-crystal X-ray diffraction analysis reveals that compound 1 is composed of a β-[Mo₈O₂₆]⁴⁻ polyoxoanion bi-supported by two [Cu(H₂biim)₂]²⁺ complex cations, an isolated β-[Mo₈O₂₆]⁴⁻ anion, and two [Cu(H₂biim)₂]²⁺ complex cations. The copper complex cations are situated at two different sites and associate with β-[Mo₈O₂₆]⁴⁻ anions to give 2D layers, which are further packed into a 3D framework via strong hydrogen bonding interactions. Compounds 2 and 3 are isostructural, and contain a γ-[Mo₈O₂₆N₂] unit and two symmetrical {M(H₂biim)₂(Hbiim)} (M=Fe or Co) fragments grafted onto the polyoxoanion through Mo–N bonds. The two compounds also exhibit 3D supramolecular frameworks involving hydrogen bonding interactions.     

Two new organic-inorganic hybrid compounds induced by γ-[Mo8O26]4− and [PMo12O40]3−

Two new organic–inorganic hybrid compounds, [Cu^II(btb)_1.5(γ-Mo₈O₂₆)_0.5(H₂O)]·2H₂O (1) and [Cu^II₂(btb)₄(PMo^VMo^VI₁₁O₄₀)]·2H₂O (2) (btb = 4-butyl-1,4-bis(1,2,4-triazole), have been hydrothermally synthesized and characterized by single-crystal X-ray diffraction analysis, IR spectra and elemental analyses. In 1, there exists a ladder-like metal-organic chain with the bidentate [γ-Mo₈O₂₆]^4? anions inserting into the grids. Adjacent chains share the same Cu-btb lines of the ladder to form a 2-D layer. Compound 2 also has a ladder-like metal-organic chain. The tetradentate [PMo₁₂O₄₀]^3? anions embed in the grids. The same Cu-btb line is shared by adjacent chains to build a 2-D layer. The btb ligands link adjacent layers to form a 3-D framework. Moreover, we also have investigated the electrochemical and photocatalytic properties of 1 and 2.     

Synthesis, crystal structure and properties of a new heptamolybdate (NH4)6H2[Cu(C2O4)2(Mo7O24)] · 9H2O

An interesting heptamolybdate (NH₄)₆H₂[Cu(C₂O₄)₂(Mo₇O₂₄)] · 9H₂O (I) was prepared by convenational method in an aqueous solution and characterized by IR spectroscopy, elemental analysis, thermogravimetric analysis, X-ray photoelectron spectroscopy and single-crystal X-ray diffraction. Crystal data for I: monoclinic, space group P2₁/m with a = 10.1460(5), b = 18.2616(9), c = 10.4994(5) ?, β = 94.3410(10)°, and Z = 2. X-ray structure analysis revealed the complexes to contain a copper center in an octahedral coordination mode bound to two [C₂O₄]²⁻ anios via the oxygen atoms and two oxygen atoms of the new heptamolybdate species. The zigzag chain structure of I is constructed by [Cu(C₂O₄)₂(Mo₇O₂₄)] units via Mo-O-Cu-O-Mo linkers.     

Supramolecular Systems Based on Ca2+, [Mo3O2S2Cl6(H2O)3]2s-, [Mo3S4Cl6.75Br0.25(H2O)2]3s- and Cucurbit[6]uril

Adducts of cucurbit[6]uril with Ca²⁺ and trinuclear cluster chloroaquacomplexes (H₉O₄)₂(H₇O₃)₂[(Ca(H₂O)₅)2(C₃₆H₃₆N₂₄O₁₂)]Cl₈·0.67H₂O (1) and [(Ca(H₂O)₅)₂(C₃₆H₃₆N₂₄O₁₂)]× [Mo₃O₂S₂Cl₆(H₂O)₃]₂·13H₂O (2) are obtained and structurally characterized. The structures of both compounds contain polymeric [Ca(H₂O) _n ]₂² CB[6]∞ cations that form infinite columns; the space between them is filled with Cl^s- (1) and [Mo₃O₂S₂Cl₆(H₂O)₃]^2s- (2). A new (H₇O₃)₂(H₅O₂)× [Mo₃S₄Cl_6.25Br_0.25(H₂O)₂](C₃₆H₃₆N₂₄O₁₂)·CH₂Cl₂·6H₂O complex (3) is also obtained and structurally characterized.     

Spectroscopic studies of molybdenum polyoxometallates with the buckyball structure and polymer-containing compositions based thereon

Molybdenum polyoxometallates with the buckyball structure, ((NH₄)₄₂[Mo₇₂^VIMo₆₀^VO₃₇₂(H₃CCOO)₃₀(H₂O)₇₂] · 30H₃CCOONH₄ · 250H₂O (I), (NH₄)₄₂[Mo₇₂^VIMo₆₀^VO₃₇₂(ClCH₂COO)₃₀(H₂O)₇₂)] · 250H₂O · 15ClCH₂COONa (II), in particular, as parts of polymer-containing compositions were studied by EPR, NMR, IR, and Raman spectroscopy. The structural and chemical aspects responsible for the formation of the observed spectra were considered.     

Syntheses and structural determination of binuclear nine-coordinate (NH4)4[SmIII2(Httha)2]·16H2O and 2-D ladder-like binuclear nine-coordinate (NH4)4[SmIII2(dtpa)2]·10H2O

Two rare-earth metal coordination compounds, (NH₄)₄[Sm^III₂(Httha)₂]·16H₂O (1) (H₆ttha?=?triethylenetetramine-N,N,N′,N′′,N′′′,N′′′-hexaacetic acid) and (NH₄)₄[Sm^III₂(dtpa)₂]·10H₂O (2) (H₅dtpa?=?diethylenetriamine-N,N,N′,N′′,N′′-pentaacetic acid), have been synthesized through reflux and characterized by FT-IR spectroscopy, thermal analysis, and single-crystal X-ray diffraction techniques. Sm^III of (NH₄)₄[Sm^III₂(Httha)₂]·16H₂O (1) is nine-coordinate, forming tricapped trigonal prismatic coordination with three amine nitrogens and six oxygens, in which four oxygens are from one ttha and two from the other ttha. (NH₄)₄[Sm^III₂(Httha)₂]·16H₂O (1) crystallizes in the monoclinic crystal system with P2(1)/c space group. The crystal data are: a?=?13.9340(13) Å, b?=?22.890(3) Å, c?=?20.708(2) (14) Å, β?=?99.521(2)°, and V?=?6513.7(13) ų. There are two –NH⁺– groups in the [Sm^III₂(Httha)₂]^4?. The polymeric (NH₄)₄[Sm^III₂(dtpa)₂]·10H₂O (2) also is nine-coordinate with tricapped trigonal prismatic conformation and crystallizes in the triclinic crystal system with P–1 space group. The cell dimensions are: a?=?9.8240(8) Å, b?=?10.0329(9) Å, c?=?13.0941(11) Å, β?=?77.1640(10)°, and V?=?1227.30(18) ų. In (NH₄)₄[Sm^III₂(dtpa)₂]·10H₂O, there are two types of ammonium cations, which connect [Sm^III₂(dtpa)₂]^4? and lattice water through hydrogen bonds, leading to a 2-D ladder-like layer structure.     

Reactions of cisplatin hydrolytes, cis-[Pt(15NH3)2(H2O) 2]2+, with N-acetyl-L-cysteine

The reaction of cis-[Pt(¹⁵NH₃)2(H₂O) ₂] ²⁺ (3) with N-acetylcysteine [H₃accys] was investigated in aqueous solution. In this reaction, the ammine in the platinum complex formed was liberated. A mono-dentate sulfur-boundplatinum(II) product cis-[Pt(¹⁵NH₃)₂(H₂O)(H2accys-S)]⁺ (7) and six-membered che-late ring complex cis-[Pt(¹⁵NH₃)₂ (Haccys-S,O)] (8) were formed in solution. The dinuclear sulfur-bridged complex 9, giving a broad peak in ¹⁵N NMR, was also observed, but only present in very tiny amounts. The mass spectrometry (ES-MS) was undertaken from this re action, and the product detected was only the dinuclear sulfur bridged platinum species and species related to it by ammine loss.     

Two-dimensional layer polyoxometalate-based inorganic metal–organic hybrid supramolecular networks woven by Cu ··· Opolyoxoanion short contact weak interactions

Two polyoxometalate-based inorganic metal-organic hybrid supramolecular complexes [Cu(2,2′-bpy)₂]₂[V^IV ₂Mo^V ₅Mo^VI ₇O₃₈(PO₄)] (1) (2,2′-bpy?=?2,2′-bipyridine) and [Cu(2,2′-bpy)₂]₂[Mo^VMo^VI ₁₁O₃₆(PO₄)]?·?3H₂O (2), have been hydrothermally prepared and structurally characterized by single-crystal X-ray diffraction. Both complexes are constructed from polyoxoanions (the bivanadyl capped α-Keggin polymolybdate anion [V^IV ₂Mo^V ₅Mo^VI ₇O₃₈(PO₄)]^4? for 1 and the reduced 12-molybdophosphate anion [Mo^VMo^VI ₁₁O₃₆(PO₄)]^4? for 2) and copper(II) complex cations [Cu(2,2′-bpy)₂]²⁺, forming two-dimensional (2D) layer network structures, in which the polyoxoanion and the complex fragment cation connect with each other through Cu?···?O_polyoxoanion short contact weak interactions, which mediate ferromagnetic interaction.     

[Cu(mim)4]2[α-Mo8O26] – A layer-type octamolybdate framework

By reaction of (NH₄)₆Mo₇O₂₄·4H₂O, Cu(NO₃)₂·2.5H₂O and 1-methylimidazole (mim) under hydrothermal conditions the novel copper molybdate [Cu(mim)₄]₂[α-Mo₈O₂₆] is obtained in the form of blue, rectangular-shaped crystals. The title compound crystallizes with monoclinic lattice symmetry in the space group P2₁/n. The predominant structural feature of the title compound is a two-dimensional framework that is constituted by [α-Mo₈O₂₆]^4?octamolybdate units as framework nods and the copper complex [Cu(mim)₄]²⁺ as a linker. In addition to single-crystal structure analysis [Cu(mim)₄]₂[α-Mo₈O₂₆] is characterized by powder diffraction as well as by FT-IR and UV–vis spectroscopy.     

Reactions of GeMe2-bridged dicyclopentadienes with molybdenum carbonyl: formation of germylidyne trimolybdenum clusters

In thermal reactions of the doubly bridged dicyclopentadienes (C₅H₃R(SiMe₂))(C₅H₃R(GeMe₂)) (R=H (1), ^tBu (5)) with Mo(CO)₆, the bridging GeMe₂ is cleaved to give the corresponding degermylated products [(η⁵-C₅H₃R)₂(SiMe₂)]Mo₂(CO)₆ (3, rac-7), or both GeMe₂ and SiMe₂ are cleaved to afford the nonbridged products [(η⁵-C₅H₄R)Mo(CO)₃]₂ (2, 6). The reactions also produce germylidyne trimolybdenum clusters [(η⁵-C₅H₃R)₂(SiMe₂)](η⁵-C₅H₄R)[Mo(CO)₂]₃(μ₃-GeMe) (4, rac-/meso-7) containing the Mo₃(μ₃-GeMe) units. Similarly, reaction of the single GeMe₂-bridged dicyclopentadienes (C₅H₅)₂GeMe₂ (9) with Mo(CO)₆ also results in the degermylated 2, as well as the similar trimolybdenum cluster [(η⁵-C₅H₅)Mo(CO)₂]₃(μ₃-GeMe) (10). The molecular structures of 4 and trans-5 were determined by X-ray diffraction.     

Two New Ferrous Molybdophosphates as Temperature-Dependent Hydrothermal Reaction Products

Two new ferrous molybdophosphates, (H₂enMe)₇Fe^II[Mo₁₂^V(HPO₄)₂(PO₄)₆(OH)₆O₂₄]·7H₂O 1 and (H₂enMe)₆Fe^II[Mo₁₂^V(HPO₄)₄(PO₄)₄(OH)₆O₂₄]·4H₂O 2 (enMe = 1,2-propanediamine), have been synthesized from an identical starting mixture through hydrothermal reactions using temperature as the only independent variable, and thoroughly characterized by IR, TG, single crystal X-ray diffraction and cyclic voltammetry. The structures of both 1 and 2 are built from the building blocks of the formula, {Fe^II[Mo₆P₄O₃₁]₂}, consisting of a network of MO₆ (M = Fe, Mo) octahedra and PO₄ tetrahedra linked through their vertices as anions, and protonated 1,2-propanediamine as cations, respectively. The most important aspect is that the non-hydrogen atomic ratio of Mo, Fe, P, O in the anions of 1 and 2 is the same, but the protonation of the PO₄ groups is different in 1 and 2. Less protonation of the PO₄ groups in 1 obtained at high temperature results in the anion carrying more charges and gives rise to more H₂enMe cations per [Fe^II(P₈Mo₁₂^V)] unit compared with that in 2 obtained at low temperature, and as a consequence, different interpenetrating hydrogen-bonded network structures are formed in the two different compounds in terms of packing efficiency and the system energy minimization.     

Syntheses and X-Ray Crystal Structures of Novel Oxonium Ion-12-Crown-4 Complexes Isolated From Liquid Clathrate Media

Abstract

The reactions of Mo(CO)₆ and W(CO)₆ with HCl_(g) in the presence of 12-crown-4 and H₂O have been investigated in toluene. For both reactions, two products were isolated, depending on the oxidation of the metal center. For molybdenum, the Mo^III species, [H₃O⁺ · 12-crown-4]₃[Mo₂Cl₉ ^3-], 1, was obtained from the liquid clathrate layer in the reaction mixture. Upon air oxidation of the reaction mixture, the Mo^v complex, [H₇O₃ ^? · H₄O₂ ⁺ · (12-crown-4)₂][MoOCl₄(H₂O)^?]₂, 2, rapidly formed. For tungsten, the W^II species, [(H₅O₂ ⁺)₂ · 12-crown-4][W(CO)₄Cl^? ₃]₂, 3, deposited from the liquid clathrate layer which upon oxidation formed the W^v complex, [H₃O⁺· 12-crown-4][WOCl₄(H₂O)^?], 4. These reactions were promoted by UV radiation and formed liquid clathrates almost immediately upon reaction. X-ray crystal structures were performed on each compound. Complexes 1 and 4 have H₃O⁺ oxonium ions involved in complex hydrogen bonded arrays with the 12-crown-4 acceptor molecules. The H₅O₂ ⁺ oxonium ions in 2 and 3 contain extremely short O…O separations, equivalent to the shortest O-H…O bonds known. Also isolated in complex 2 was the H₇O₃ ⁺ oxonium ion which contains an unusual linear O…O…O core.     

Experimental and theoretical study of <Superscript>13</Superscript>C shielding tensors in new-style molybdenum complex

¹³C 2D-PASS spectra of two new cis-dioxo catecholatomolybdenum complexes (NH₂CH₂NH₂CHCH₂)₂(H⁺)₃[Mo^vO ₂(C₆H₄O₂)₂] and (NH₂CH₂CH₂CH₂NH₂)₂(H⁺)₃[Mo^(v)O₂ (C₂H₂O₂)₂] have been obtained by solid-state nuclear magnetic resonance (NMR), in which the spinning sidebands were well-separated. The principal components of the ¹³C shielding tensors were extracted by theoretically fitting the intensities of ¹³C spinning sidebands. The effects of counter cations on ¹³C chemical shift isotropy and shielding tensor of cis-dioxo catecholatomolybdenum complex anion [Mo ^(v)O₂(C₆H₄O₂)₂]³⁻ were studied, comparing the ¹³C CSA of those carbon sites in complex anions with that of the counter cations. Based on the known structure of the molybdenum complex crystal, theoretical values of ¹³C shielding tensors were calculated by the ainitio GIAO method, in comparison with the experimental results.     

Hydrothermal Syntheses and Crystal Structures of Compounds Based on <Emphasis Type="Italic">α</Emphasis>- or <Emphasis Type="Italic">β</Emphasis>-[Mo<Subscript>8</Subscript>O<Subscript>26</Subscript>]<Superscript>4−</Superscript> Isomers

Using Cu(II/I)/Ni(II) complex fragments and [Bu₄N]₄[α-Mo₈O₂₆] as precursors, four compounds based on α- or β- octamolybdate isomers, [{Cu(tpdoen)}₂][α-Mo₈O₂₆]·3H₂O 1 (tpdoen = 2-(pyridin-2-ylmethoxy)-N-(2-(pyridin-2-ylmethoxy)ethyl)-N-(pyridin-2-ylmethyl)ethanamine); [{Cu(dpoen)}₂(α-Mo₈O₂₆)] 2 (dpoen = 2-(pyridin-2-ylmethoxy)-N-(pyridin-2-ylmethyl)ethanamine); [{Cu(dpmea)}₂(β-Mo₈O₂₆)] 3 (dpmea = N,N-diethyl-N-(pyridin-2-ylmethyl)ethanaminium); [{Ni(tpoen)}₂(β-Mo₈O₂₆)]·5H₂O 4 (tpoen = 2-(pyridin-2-ylmethoxy)-N,N-bis(pyridin-2-ylmethyl)ethanamine) were hydrothermally synthesized. They have been characterized by elemental analysis, FT-IR, TG analysis and single-crystal X-ray diffraction. Compound 1 is a discrete structure constructed from [α-Mo₈O₂₆]⁴⁻ anions and [Cu(tpdoen)]²⁺ coordination cations. The coordination cations aggregate around an octamolybdate anion via hydrogen bonding interactions, forming a “flowerpot” supramolecular network. Compound 2 is constructed from [α-Mo₈O₂₆]⁴⁻ anions bridged through [Cu(dpoen)]²⁺ fragments into a 2D layered grid. Compounds 3 and 4 are Cu(I) and Cu(II) complexes bis-supported by [β-Mo₈O₂₆]⁴⁻ anions, respectively. The electrochemical behaviors of compounds 1–4 modified solid bulk-modified carbon paste electrodes (1-MCPE-4-MCPE) have been studied.     

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.     

Hydrothermal synthesis and structural characterization of two new reduced phosphomolybdates based on an organoamine template and copper ion

Two new compounds, (H₂en)₃(H₂enMe)₄(H₃O){Cu^I[Mo^V ₆O₁₂(OH)₃(HPO₄)(PO₄)₃]₂}?·?6H₂O (1) and (H₂enMe)₄{Cu^ICu^II[Mo^V ₆O₁₂(OH)₃(PO₄)(HPO₄)₂(H₂PO₄)]₂}?·?3H₂O (2), were hydrothermally synthesized and characterized by elemental analysis, IR, TGA, and single-crystal X-ray diffraction analysis. Crystallographic analysis reveals that 1 is constructed from cluster anions {Cu^I[Mo^V ₆O₁₂(OH)₃(HPO₄)(PO₄)₃]₂}^15?, protonated organic amines, and water molecules. Each cluster is bridged through hydrogen bonds to form a 3-D supermolecular structure. For 2, {Cu^I[Mo^V ₆O₁₂(OH)₃(PO₄)(HPO₄)₂(H₂PO₄)]₂}^11? are connected by Cu^II cations to form an infinite chain. The formation of 1 and 2 reveals that organoamines influence the structures of the crystals.     

Hydrothermal Synthesis and Structure of Two New Mo(V)-Oxide Phosphates

Two new members of Mo(V) phosphates were synthesized by hydrothermal methods. (enH₂)(enH)[NaMo₁₂O₂₄(OH)₆(HPO₄)₂(H₂PO₄)₆]·(en)₄·20H₂O(1)(en=H₂ NCH₂CH₂NH₂)[HAD-H₂]₂[HAD-H]₂[Zn₃Mo₁₂O₂₄(OH)₆(PO₄)₂(HPO₄)₆]·6H₂O (2) (HAD=H₂N(CH₂)₆NH₂). Compound 1 crystallized in the space group P2(1)/n, a=15.93120(10) Å, b=15.8946(2) Å, c=17.0665(2) Å, V=4316.02(8), =92.9060(10)°, Z=2. Compound 2 crystallized in the space group P(–1) with a=12.3726(3) Å, b=14.1948(3) Å, c=14.2310(4) Å, =72.7100(10), =65.0230(10), =69.5600(10)°, Z=2089.70(9) ų, and Z=1. The structure of 1 consists of sandwich-shaped cluster anion [Na{Mo^V ₆O₁₂(OH)₃(HPO₄)(H₂PO₄)₃}₂]^3– ({Na(Mo ^V ₆ ) ₂ }) held together via intermolecular hydrogen-bonding contacts. For the compound 2, the sandwich-shaped clusters Zn[Mo₆O₁₂(OH)₃(PO₄)(HPO₄)₃]₂ ({Zn(Mo ^V ₆ ) ₂} are linked by tetrahedrally-coordinated zinc into layers. Organic cations ([H₃N(CH₂)₆NH₃]²⁺ and [H₃N(CH₂)₆NH₂]⁺) are filled in the spaces between lamellas. The layers are held together by a hydrogen-bonded network, which involves the terminal phosphate P-OH groups, as well as organic cations and several waters of solvation.     

Study on ligation of copper complexes of the quinolone antibacterial drugs and octamolybdates POMs

By introducing different quinolone antibacterial drugs into the octamolybdates POMs, four new compounds, [Cu^II(L¹)₂(H₂O)₂]H₂[β-Mo₈O₂₆]·4H₂O (1), [Cu^II₂(L²)₄][δ-Mo₈O₂₆]·4H₂O (2), [Cu^II₂(L³)₂(H₂O)₂][β-Mo₈O₂₆] (3), [Cu^II₂(L⁴)₂(H₂O)₄][β-Mo₈O₂₆]·2H₂O (4) (where L¹ = Enrofloxacin; L² = Pipemidic Acid; L³ = Norfloxacin; L⁴ = Enoxacin), have been synthesized and characterized by routine physical methods and single crystal X-ray diffraction. In compound 1, isolated Cu-Enrofloxacin coordination subunits array the both sides of β-Mo₈O₂₆, forming 3D supramolecular structure via noncovalent interactions. And the Cu-Pipemidic Acid subunits covalently link δ-Mo₈O₂₆ to form 3D supramolecular structures via short interactions in 2. In 3, the Cu-Norfloxacin motif exhibits 1D chain structure, and the tetra-dentate β-[Mo₈O₂₆]⁴⁻ clusters interact with neighboring chains to construct a 2D sheet. Similar to that of 3, the Cu-Enoxacin subunit in 4 exhibits 1D chain structure, and the bi-dentate β-[Mo₈O₂₆]⁴⁻ clusters interact with neighboring chains to construct a 2D sheet. Due to the introduction of different drug molecules, the octamolybdates POMs exhibit different isomers and structures, which bring different properties. The antitumor activities of compounds 1-4 in vitro were studied by MTT experiments, and the results show that introduction of different drug molecules onto the polyoxoanion surface can affect their antitumor activities.     

Synthesis, Structure, and 31P NMR of Sulfur/Oxygen-Bridged Incomplete Cubane-Type Molybdenum and Tungsten Clusters with Triphenylphosphine Ligands

Sulfur/oxygen-bridged incomplete cubane-type triphenylphosphine molybdenum and tungsten-clusters [Mo₃S₄Cl₄(H₂O)₂(PPh₃)₃]·3THF (1A), [Mo₃S₄Cl₄(H₂O)₂(PPh₃)₃]·2THF (2A), [Mo₃OS₃Cl₄(H₂O)₂(PPh₃)₃]·2THF (1B), and [W₃S₄Cl₄(H₂O)₂(PPh₃)₃]·2THF (1C) were prepared from the corresponding aqua clusters and PPh₃ in THF/MeOH. On recrystallization from THF, procedures with and without addition of hexane to the solution gave 1A and 2A, respectively, while the procedures gave no effect on the formation of 1B and 1C. Crystallographic results obtained are as follows: 1A: monoclinic, P2₁/n, a=17.141(4) Å, b=22.579(5) Å, c=19.069(4) Å, =96.18(2)°, V=7337(3) ų, Z=4, R(R _w)=0.078(0.102); 1C: monoclinic, P2 ₁/c, a=12.635(1) Å, b=20.216(4) Å, c=27.815(3) Å, =96.16(1)°, V=7062(2) ų, Z=4, R(R _w)=0.071(0.083). If the phenyl groups are ignored, the molecule [Mo₃S₄Cl₄(H₂O)₂(PPh₃)₃] in 2A has idealized CS symmetry with the mirror plane perpendicular to the plane determined by the metal atoms, while the molecule in 1A does not have the symmetry. The tungsten compound 1C is isomorphous with the molybdenum compound 2A. ³¹P NMR spectra of 1A, 2A, and 1C were obtained and compared with similar clusters with dmpe (1,2-bis(dimethylphosphino)ethane) ligands.     

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.