A large series of isotypic Mo(V) diphosphates with a tunnel structure: From A(MoO)10(P2O7)8 with A=Ba, Sr, Ca, Cd, Pb to A(MoO)5(P2O7)4 with A=Ag, Li, Na, K

The single crystal structure of a series of nine isotypic Mo(V) diphosphates was determined from crystals with composition A²⁺(MoO)₁₀(P₂O₇)₈ (A=Ba, Sr, Ca, Cd, Pb) and A⁺(MoO)₅(P₂O₇)₄ (A=Ag, Li, Na, K). The structure of those phosphates, built up of corner sharing MoO₆ octahedra, MoO₅ tetragonal pyramids and P₂O₇ diphosphates groups, forms eight-sided tunnels as described by Lii et al. for A=Ag. New features are evidenced: (1) existence of two orientations, up and down along b for the MoO₅ pyramids; (2) maximum insertion rate of the divalent cations which is twice less than that of the univalent cations; (3) different behavior of the series “Pb, Sr, Ba, Li, Na, K” which exhibits only one kind of site for the inserted cation, compared to the “Cd, Ca, Ag” series for which two kinds of sites are observed; (4) off-centering of the A-site cations with respect to the tunnel axis; and (5) unusually high thermal factors along the tunnel axis, but absence of ionic conductivity.     

[Zn(H2PO4)4] clusters and ∞[Zn2(HPO4)3(H2PO4)2] layers in two new zinc phosphates templated by [H2(4-amino-2.2.6.6-tetramethylpiperidine)] cations

Two zinc phosphates (ZnPO), [H₂(N₂C₉H₂₀)]·[Zn(H₂PO₄)₄] (I) and [H₂(N₂C₉H₂₀)]₂·[Zn₂(HPO₄)₃(H₂PO₄)₂]·H₂O (II), are synthesized under hydrothermal conditions using 4-amino-2.2.6.6-tetramethylpiperidine as organic template. I crystallizes in space group with , , , α=92.57(1)°, β=89.76(1)°, γ=102.16(2)°, and Z=2. Its structure, refined to R=0.029 and R_w=0.076 for 4279 independent reflections, consists of [Zn(H₂PO₄)₄]²⁻ clusters held together through strong hydrogen bonds to form pseudo-layers between which the doubly protonated amine molecules are inserted. II is monoclinic, C2, with , , , β=103.72(5)°, and Z=4 (R=0.079, R_w=0.268, 2477 independent reflections). The structure of II consists of _∞[Zn₂(HPO₄)₃(H₂PO₄)₂]⁴⁻ inorganic (2D) layers built up from vertex-sharing [ZnO₄] and [(H₂/H)PO₄] tetrahedra. Organic cations and water molecules ensure the connection between these layers via hydrogen bonds. It is shown that numerous (1D), (2D), e.g., [H₂(N₂C₉H₂₀)]₂·[Zn₂(HPO₄)₃(H₂PO₄)₂]·H₂O, and (3D) (ZnPO) result from the condensation of the [Zn(H₂PO₄)₄]²⁻ clusters.     

Two mixed valent molybdenophosphates with a tunnel structure closely related to K0.17MoP2O7: Pb2(PbO)2Mo8(P2O7)8 and PbK2Mo8(P2O7)8

Two new mixed valent Mo(III)/Mo(IV) diphosphates containing lead Pb₂(PbO)₂Mo₈(P₂O₇)₈ and PbK₂Mo₈(P₂O₇)₈ have been synthesized. The [Mo₈P₁₆O₅₆]∞ frameworks of these phosphates are closely related to that of K_0.17MoP₂O₇: the MoO₆ octahedra and P₂O₇ groups form two sorts of large eight-sided tunnels. They are occupied in an ordered way by PbO chains and Pb²⁺ cations in Pb₂(PbO)₂Mo₈(P₂O₇)₈ and by K⁺ and Pb²⁺ cations in PbK₂Mo₈(P₂O₇)₈. It results in different symmetries of these two structures, which are tetragonal and monoclinic, respectively, showing the great flexibility of these mixed frameworks, susceptible to accommodate various species with different sizes.     

A2VNb6Cl18 (A=Rb, In, Tl): synthesis, crystal structure and magnetic properties of a new series of quaternary niobium chloride cluster compounds

A new series of quaternary niobium chloride cluster compounds corresponding to the general formula, A₂VNb₆Cl₁₈ (A=Rb, Tl or In), has been prepared in sealed quartz tubes from a mixture containing NbCl₅, Nb, VCl₃ and RbCl, or In or Tl metal by solid state reactions at 750°C. The structure of Tl₂VNb₆Cl₁₈ was determined using single-crystal X-ray diffraction: Crystal data: rhombohedral, (No. 148), a=9.1122(17), c=25.178(7) Å, V=1810.5(7) ų and Z=3. The full-matrix least-squares refinement against F² converged to R₁=0.0515, wR₂=0.1104 (all data). The structure consists of discrete octahedral cluster units, [Nb₆Clⁱ₁₂Cl^a₆]⁴⁻ linked by V²⁺ and A⁺ cations, located in a 6-coordinated octahedral and 12-coordinated anticubeoctahedral chloride environment, respectively. The intra-cluster bond lengths indicate 16 valence electrons per cluster. Magnetic susceptibility studies show paramagnetic behavior with a magnetic moment of 3.37 μ_B per formula unit. Electrical resistivity measurements indicate a semiconducting behavior.     

Synthesis, characterization and reactivity of the molybdenum(VI) complex [MoCl(NAr)2(CH2CMe2Ph)] (Ar=2,6-Pr2C6H3)

The compounds [MoCl(NAr)₂R] (R=CH₂CMe₂Ph (1) or CH₂CMe₃(2); Ar=2,6-Prⁱ₂C₆H₃) have been prepared from [MoCl₂(NAr)₂(dme)] (dme=1,2-dimethoxyethane) and one equivalent of the respective Grignard reagent RMgCl in diethyl ether. Similarly, the mixed-imido complex [MoCl₂(NAr)(NBu^t)(dme)] affords [MoCl(NAr)(NBu^t)(CH₂CMe₂Ph)] (3). Chloride substitution reactions of 1 with the appropriate lithium reagents afford the compounds [MoCp(NAr)₂(CH₂CMe₂Ph)] (4) (Cp=cyclopentadienyl), [MoInd(NAr)₂(CH₂CMe₂Ph)] (5) (Ind=Indenyl), [Mo(OBu^t)(NAr)₂(CH₂CMe ₂Ph)] (6), [MoMe(NAr)₂(CH₂CMe₂Ph)] (7), [MoMe(PMe₃)(NAr)₂(CH₂CMe ₂Ph)] (8) (formed in the presence of PMe₃) and [Mo(NHAr)(NAr)₂(CH₂CMe₂P h)](9). In the latter case, a by-product {[Mo(NAr)₂(CH₂CMe₂Ph) ]₂(μ-O)}(10) has also been isolated. The crystal structures of 1, 4, 5 and 10 have been determined. All possess distorted tetrahedral metal centres with cis near-linear arylimido ligands; in each case (except 5, for which the evidence is unclear) there are α-agostic interactions present.     

A new vanadium(III) fluorophosphate with ferromagnetic interactions, (NH4)[V(PO4)F]

A new vanadium(III) phosphate, (NH₄)[V(PO₄)F], has been synthesized by using mild hydrothermal conditions under autogeneous pressure. The crystal structure has been solved from X-ray single crystal data. The compound crystallizes in the Pnna orthorhombic space group, with the unit-cell parameters a=12.982(2), b=10.608(1), c=6.4789(6)Å and Z=8. The final R factors were R₁=0.077 [all data] and wR₂=0.068. The crystal structure consists of a three-dimensional framework formed by VO₄F₂ octahedra and tetrahedral (PO₄)³⁻ phosphate anions. The vanadium(III) cations from the VO₄F₂ octahedra are linked through the fluorine atoms giving rise to zig-zag chains. The ammonium cations are located in the cavities of the structure compensating the anionic charge of the [V(PO₄)F]⁻ inorganic skeleton. The IR spectrum shows the characteristic bands of the phosphate anion. The diffuse reflectance spectroscopy allowed us to calculate the Dq and Racah parameters. The values are Dq=1540, B=505 and C=2460 cm⁻¹. Magnetic measurements indicate the existence of weak ferromagnetic interactions.     

Synthese und Struktur von Cs11[(WN2,5O1,5)2](N3)2, ein Caesiumoxonitridomonowolframat(VI)-azid

Synthesis and Structure of Cs₁₁[(WN_2,5O_1,5)₂](N₃)₂, a Cesium Oxo Nitrido Monotungstate(VI) Azide Cs₁₁[(WN_2,5O_1,5)₂](N₃)₂ results from the reaction of a mixture of CsNH₂, W and WO₃ at 620 °C in autoclaves. It crystallizes monoclinic in the space group C2/m with the lattice parameters a = 12.421(4) Å, b = 11.568(6) Å, c = 10.516(4) Å, β = 118.71(3)° and Z = 4. The crystal structure is built up by isolated tetrahedra [WX₄] with X = N, O, which are connected by cesium cations. Between the cesium ions lie azide ions separated from the anions [WX₄]. The tungsten atoms and azide ions together build up the motif of a distorted arrangement of the CsCl structure type.     

A novel Mo(V) oligophosphate built up of di- and triphosphate groups: Cs(MoO)4(P2O7)2(P3O10)

A Mo(V) oligophosphate, built up of di and triphosphate groups, Cs(MoO)₄(P₂O₇)₂(P₃O₁₀) has been synthesized for the first time. This compound crystallizes in the triclinic P−1 space group with , , , α=94.534(6)°, β=102.520(6)°, γ=103.663(4)°. This original structure can be described by the association of MoO₆ octahedra, MoP₂O₁₁ units built up of one P₂O₇ group sharing two apices with the same MoO₆ octahedron, and triphosphates groups P₃O₁₀. The resulting tridimensional framework forms large S-shaped tunnels running along c where the Cs⁺ cations are located.     

Halide abstraction as a route to cationic molybdenum(IV) compounds: Crystal and molecular structure of [CpMoCI(MeCN)4][SbCl6]2 · MeCN

Treatment of CpMoC1₃(MeCN)₂ with SbCl₅ in acetonitrile solution provides the solvated cationic series [CpMoCl₂(MeCN)₃]⁺, [CpMoCl(MeCN)₄]²⁺ and [CpMo(MeCN)₆]³⁺ as hexachloroantimon(V)ate salts following sequential halide abstraction. Characterization follows from microanalytical and spectroscopic (IR, and ¹H NMR) data and, in the case of [CpMoCl(MeCN)₄][SbCl₆]₂ · MeCN, by X-ray crystallographic studies. The structure is disordered but individual cations contain a six coordinated pseudo-octahedral metal geometry in which the cyclopentadienyl ligand (regarded as unidentate) and the chlorine atom occupy axial positions with an equatorial array of four acetonitrile ligands.     

Synthesis,spectral characterization and crystal structure studies of a new hydrazone Schiff base and its dioxomolybdenum(VI) complex

A new hydrazone Schiff base, (E)-N′-(3-ethoxy-2-hydroxybenzylidene)isonicotinohydrazide (H₂L), has been prepared and characterized by elemental analyses, spectroscopic methods, and single-crystal X-ray diffraction. The corresponding dioxomolybdenum(VI) complex [Mo(O)₂(L)(CH₃OH)] was synthesized and characterized by spectroscopic methods and by single-crystal X-ray diffraction. The hydrazone ligand coordinates to Mo through the phenolate O, imine N, and enolic O. The Mo center displays a distorted octahedral geometry with the three donors of the ligands and an oxo defining the equatorial plane, and one methanol and another oxo occupying the axial positions.     

Tl2D coordination polymer involving close Tl?π (aromatic) contacts, [Tl3(μ-BPC)2(μ-NO3)]n

A two-dimensional polymer, [Tl₃(μ-BPC)₂(μ-NO₃)]_n [BPC = biphenyl-2-carboxylate], has been synthesized and characterized. Its single-crystal X-ray structure shows three types of Tl^I-ions with coordination numbers of 5 (Tl1 and Tl2), and 4 (Tl3). Two of the thallium atoms, Tl1 and Tl3, contain close Tl^I?π (aromatic) contacts, thus attaining a total hapticity of 11 and 10 with environments Tl1O₅C₆ and Tl3O₄C₆, respectively.     

Synthesis,structural characterization,and catalytic reactivity of a new molybdenum(VI) complex containing 1,3,4-thiadiazole derivative as a tridentate NNO donor ligand

A new cis-dioxo molybdenum(VI) complex was obtained by reaction of 2,4-dihydroxybenzylidene(5-N,N-methylphenylamino-1,3,4-thiadiazol-2-yl)hydrazone as ligand and [MoO₂(acac)₂] in methanol and was characterized by elemental analyses, ¹H NMR, IR, and electronic spectroscopic studies. The complex was also analyzed by single-crystal X-ray diffraction. The structure determination revealed a distorted octahedral coordination geometry around molybdenum in which the tridentate NNO donor (L^2–) is bonded to [MoO₂]²⁺ through phenolic oxygen, hydrazinic nitrogen, and thiadiazole nitrogen. The sixth coordination site is occupied by a weakly bonded methanol. The complex was tested as a catalyst for homogeneous epoxidation of olefins using tert-butyl hydrogen peroxide as an oxidant. In the homogeneous catalytic system, the reactions are efficiently carried out with high yields and selectivity.     

Synthesis,structure and properties of eight novel molybdenum(VI) complexes of the types: [MoO2LD] and [{MoO2L}2D] (L = thiosemicarbazonato ligand,D = N-donor molecule)

Eight new molybdenum(VI) complexes with 4-(diethylamino)salicylaldehyde and 2-hydroxy-3-methoxybenzaldehyde thiosemicarbazones have been prepared. They were characterized as mononuclear [MoO₂LD] or dinuclear [{MoO₂L}₂D] complexes. In all the compounds the MoO₂²⁺ core is coordinated by a tridentate ONS thiosemicarbazonato ligand and by the N-donor molecule (imidazole, pyridine or γ-picoline). All the complexes were characterized by chemical analysis, IR spectroscopy and thermogravimetry. Three of the mononuclear complexes, dioxo[(2-hydroxy-3-methoxybenzaldehyde thiosemicarbazonato)(pyridine)]molybdenum(VI), dioxo[(2-hydroxy-3-methoxybenzaldehyde thiosemicarbazonato)(γ-picoline)]molybdenum(VI) and dioxo[(2-hydroxy-3-methoxybenzaldehyde thiosemicarbazonato)(imidazole)]molybdenum(VI) were also characterized by single-crystal X-ray structural analysis. A spectrophotometric method for the determination of molybdenum based on extraction of ion-pairs formed by the cationic surfactant and the [MoO(SCN)₄]⁻ anion is described.     

New thallium iodates—Synthesis, characterization, and calculations of Tl(IO3)3 and Tl4(IO3)6, [Tl3Tl(IO3)6]

Two new thallium iodates have been synthesized, Tl(IO₃)₃ and Tl₄(IO₃)₆ [Tl⁺₃Tl³⁺(IO₃)₆], and characterized by single-crystal X-ray diffraction. Both materials were synthesized as phase-pure compounds through hydrothermal techniques using Tl₂CO₃ and HIO₃ as reagents. The materials crystallize in space groups R-3 (Tl(IO₃)₃) and P-1 (Tl₄(IO₃)₆). Although lone-pairs are observed for both I⁵⁺ and Tl⁺, electronic structure calculations indicate the lone-pair on I⁵⁺ is stereo-active, whereas the lone-pair on Tl⁺ is inert.     

A Series of New Molybdenum(VI) Complexes with the ONS Donor Thiosemicarbazone Ligands

New dioxomolybdenum(VI) complexes were obtained by the reaction of [MoO₂(acac)₂] with 4‐phenylthiosemicarbazone ligands derived from salicylaldehyde, 2‐hydroxy‐1‐naphthaldehyde, 2‐hydroxy‐3‐methoxybenzaldehyde or from 4‐(diethylamino)salicylaldehyde. In all complexes the ligands are coordinated to molybdenum as tridentate ONS‐donors through phenolic‐oxygen, imine‐nitrogen and thiol‐sulphur. Octahedral coordination of each Mo atom is completed either by one neutral donor molecule (D) or by the oxygen atom of the Mo=O unit from the neighbouring molecule. All compounds were characterized by means of chemical analysis, IR spectroscopy, TG and in some cases by DSC measurements, some of them by X‐ray crystallography, and by one and two‐dimensional NMR method.     

Synthesis,characterization, X-ray structure and DFT calculation of two Mo(VI) and Ni(II) Schiff-base complexes

In this study, the syntheses of two new Mo(VI) and Ni(II) complexes with H₂L tridentate (ONO) Schiff-base ligand have been described and fully characterized by means of elemental analysis, FT–IR, electronic, ¹H-NMR spectroscopy and single-crystal X-ray diffraction. In both complexes, the Schiff-base completely deprotonates and coordinates to the metal ion as a dianionic tridentate ligand via the donor oxygens and nitrogen atoms. The coordination numbers of Mo(VI) and Ni(II) are six and four, respectively. The DFT-B3LYP/6–31 + G (d,p) and PBEPBE/6–31 + G (d,p) calculations are carried out for the determination of the optimized structures. Frequency calculations and NBO analysis are also performed for characterization. According to the theoretical analysis of the complexes, ligand-to-metal donation is greater than back donation. NBO data revealed that the main contribution of the frontier orbitals belongs to L⁻².     

Solid-state synthesis, structural variants and transformation of three-dimensional sulfides, AGaSnS4 (A=Na, K, Rb, Cs, Tl) and Na1.263Ga1.263Sn0.737S4

New cubic-AGaSnS₄ (A=Na, K, Rb, Cs, Tl) and orthorhombic-NaGaSnS₄ compounds were synthesized by solid-state reactions and characterized by X-ray diffraction and diffuse reflectance spectroscopy. Single crystals of orthorhombic-Na_1.263Ga_1.263Sn_0.737S₄ were obtained in the crystal growth attempts of sodium compound. All six new compounds have orthorhombic AgGaGeS₄ and cubic BaGa₂S₄ structures, as determined from single crystal X-ray structures of Na_1.263Ga_1.263Sn_0.737S₄ and cubic-AGaSnS₄ (A=Na, K, Rb). Orthorhombic-NaGaSnS₄ and known layered-KGaSnS₄ undergo structural transformation to thermodynamically stable cubic form.     

Synthesis, structure studies and electrochemistry of molybdenum(VI) Schiff base complexes in the presence of different donor solvent molecules

The reactions between bis(acetylacetonato)dioxomolybdenum(VI) and Schiff base ligands derived from 5-chlorosalicylaldehyde or 3-ethoxy-salicylaldehye, and 3-methoxy-benzoic hydrazide (m-anisic hydrazide), 2-furoic hydrazide or 2,4-dihydroxy-benzoic hydrazide in the presence of donor solvents yielded cis-dioxomolybdenum(VI) complexes with the general formula MoO₂L(D), where L = tridentate Schiff base ligand and D = dimethylsulfoxide, hexamethylphosphoramide, dimethylformamide, imidazole or methanol. The complexes were characterized by elemental analysis, electronic spectra, IR, ¹H and ¹³C NMR spectroscopies, thermogravimetric analysis, cyclic voltammetry, and the molecular structures of five of the dioxomolybdenum complexes were elucidated by single crystal X-ray diffractometion studies. In general, the complexes adopt an octahedral environment around the Mo center with a cis-oxo configuration. The other coordination sites are occupied by the imino nitrogen, phenoxyl oxygen, hydroxyl oxygen of the tridentate Schiff base and the donor atom of the solvent molecule. The structural data revealed that the labile coordination site, which is occupied by N or O atoms from the donor solvents, has a longer Mo-O or Mo-N bond distance.     

Structures,DNA binding,DNA cleavage,and antitumor investigations of a series of molybdenum(VI) complexes with some N(4) methyl and ethyl thiosemicarbazone ligands

Four dioxomolybdenum(VI) complexes were synthesized by reaction of [MoO₂(acac)₂] with thiosemicarbazones derived from 5-allyl-2-hydroxy-3-methoxybenzaldehyde (1), 2-hydroxynaphthaldehyde (2), 2,3-dihydroxybenzaldehyde (3), or 5-tert-butyl-2-hydroxybenzaldehyde (4). The ligands were coordinated to molybdenum as tridentate ONS donors. X-ray crystallography showed that the distorted octahedral coordination of molybdenum is completed by methanol (D) in 1a, 3a, and 4a or H₂O in 2a. The molecular structures of 1, 3, and 4, and the complexes were determined by single-crystal X-ray crystallography. Binding of the ligand and complexes with calf thymus DNA were investigated by UV, fluorescence titrations, and viscosity measurements. Gel electrophoresis revealed that all the complexes can cleave pBR322 plasmid DNA. The cytotoxic properties of the complexes against human colorectal (HCT 116) cell line showed strong antiproliferative activities in relative order 4a?>?3a?>?1a?>?2a with IC₅₀ values of 1.6, 4.0, 4.8, and 6.7?μM, respectively. The complexes exhibited more activity than the standard reference drug, 5-fluorouracil (IC₅₀ 7.3?μM). These studies show that dioxomolybdenum(VI) complexes have potential use in chemotherapy.     

Hydrothermal synthesis and characterisation of new methylenediphosphonates of molybdenum(VI), A[MoO2(O3PCH2PO3H)] (A = Rb, NH4 and Tl)

Three new, isostructural methylenediphosphonates of molybdenum, A[MoO₂(O₃PCH₂PO₃H)] (A = Rb (1), NH₄ (2) and Tl (3)) have been synthesized by hydrothermal method and structurally characterised by X-ray diffraction and spectroscopic techniques. These compounds crystallize in monoclinic space group,P2 ₁ /c with Z = 4 and consist of [MoO₂(O₃PCH₂PO₃H)]-anionic layers interleaved with A⁺ ions. Dedicated to Professor C N R Rao on his 70th birthday