Edge-sharing MoO Research Articles

Synthesis, Crystal Structure, and Electrical and Magnetic Characterizations of the Monoclinic Compounds Ln3Mo4+xSi1–xO14 (Ln = La, Ce, Pr, and Nd; x = 0 and 0.35) Containing Mo3 Clusters and Mo2 Dimers

Powder samples of the new monoclinic compounds Ln3Mo4SiO14 (Ln = La, Ce, Pr, and Nd) and single crystals of Pr3Mo4.35Si0.65O14 were obtained by the solid-state reaction. The crystal structure of Pr3Mo4.35Si0.65O14 was determined by single-crystal X-ray diffraction. Pr3Mo4.35Si0.65O14 crystallizes in the monoclinic space group P21/n with unit-cell parameters a = 5.6361 (2) Å, b = 17.5814 (8) Å, c = 10.9883 (4) Å, and Z = 4. Full-matrix least-squares refinement on F2 using 7544 independent reflections for 203 refinable parameters results in R1 = 0.0359 and wR2 = 0.0831. The structure contains chains of Mo3O13 clusters and chains of edge-sharing MoO6 octahedra with alternately short (2.508 Å) and long (3.161 Å) Mo-Mo distances running parallel to the a axis that are separated by 8- or 10-coordinate Pr-O polyhedra. Magnetic susceptibility measurements on the Ln3Mo4SiO14 (Ln = La, Ce, Pr, and Nd) are in agreement with a trivalent state of the rare earths for the Ce, Pr, and Nd compounds, while that on the lanthanum compound confirms the presence of one unpaired electron per Mo3 as expected. Resistivity measurements on a single crystal show that Pr3Mo4.35Si0.65O14 is a small band gap semi-conductor.

Identifying Key Descriptors for the Single-Atom Catalyzed CO Oxidation

Identifying Key Descriptors for the Single-Atom Catalyzed CO Oxidation

The structural effects of alkaline- and rare-earth element incorporation into thorium molybdates

Four novel thorium molybdates containing alkaline-earth or rare-earth metals were isolated from high-temperature solid-state synthesis. The incorporation of divalent and trivalent cations into the thorium molybdate system results in complex structural topologies. A2MgTh3(MoO4)8 (A = K, Rb) which crystallizes in the space group C2/c is the first instance among the thorium molybdate family that incorporates alkaline-earth metals. Its crystal structure is based on complex channels composed of ThO8 square antiprisms and MoO4 tetrahedra arranged in a corner-sharing manner. K2SrTh2(MoO4)6, as the first thorium polymolybdate compound, is constructed from ThO8 square antiprisms and Mo4O16 tetramers. The Mo4O16 tetramers, lying in the (001) plane, are built from four edge-sharing MoO6 octahedra. Nd2Th3(MoO4)9 is the first thorium molybdate containing rare-earth cations. The resemblance of Nd2Th3(MoO4)9 with hexagonal-ThMo2O8 reveals its potential as a host for different trivalent transuranium elements. Raman spectra analysis shows that the different Mo polyhedral geometries (MoO4 tetrahedra and MoO6 octahedra) have significant effects on the vibrational bands of these compounds. The thermal behavior and stability of the newly obtained materials have been studied.

K2Na8(UO2)8Mo4O24[(S,Mo)O4], the first uranium molybdosulfate: synthesis, crystal structure, and comparison to related compounds

Orange platy crystals of K2Na8(UO2)8Mo4O24[(S,Mo)O4], the first known uranium molybdosulfate, have been prepared by high-temperature solid-state reactions. The structure (monoclinic, C2/c, a = 24.282(4), b = 12.1170(18), c = 13.6174(17) A, β = 106.33(1)o, V = 3845.0(9) A3, Z = 4) has been solved by direct methods and refined to R1 = 0.058 on the basis of 2837 unique observed reflections. The structure consists of a three-dimensional heteropolyhedral framework based upon the [(UO2)4O4(Mo2O10)] layers parallel to (010). The layers are formed by linkage of chains of edge-sharing UO7 bipyramids running along the c axis via the Mo2O10 dimers of edge-sharing MoO6 octahedra. Linkage of the layers into a three-dimensional framework is provided by the MoO4 and SO4 tetrahedra that share corners with the MoO6 octahedra. The Na+ and K+ cations reside in framework cavities in between the uranyl molybdate layers. The structure of K2Na8(UO2)8Mo4O24[(S,Mo)O4] is yet another complex derivative of the U2MoO8 structure type.

K3MoPO7: the first molybdenum phosphate with edge-sharing MoO6octahedra and PO4tetrahedra

The unique edge-sharing MoO6and PO4polyhedra were first discovered in a novel molybdenum phosphate K3MoPO7.

New Molybdenum(VI) Phosphates: Synthesis, Characterization, and Calculations of Centrosymmetric RbMoO2PO4and Noncentrosymmetric Rb4Mo5P2O22

Two new molybdenum(VI) phosphates, RbMoO(2)PO(4) and Rb(4)Mo(5)P(2)O(22), have been synthesized by standard solid-state reactions, and their structures were determined by single-crystal X-ray diffraction. The former is centrosymmetric, whereas the latter is noncentrosymmetric and chiral. Their crystal structures both consist of corner- and edge-shared MoO(6) octahedra, PO(4) tetrahedra, and RbO(n) (n = 8 or 10) polyhedra and exhibit three- and one-dimensional structures, respectively. Powder second-harmonic generation (SHG) measurements revealed an SHG efficiency of approximately 1.4 × KH(2)PO(4) (KDP) for Rb(4)Mo(5)P(2)O(22). Thermal analysis, infrared and UV-vis-NIR diffuse reflectance spectroscopy, and electronic band structure calculations were also performed on the reported materials. Crystal data are the following: RbMoO(2)PO(4), orthorhombic, space group Fddd (No. 70), a = 11.012(5) Å, b = 12.403(5) Å, c = 15.839(7) Å, V = 2163.3(16) Å(3), and Z = 16; Rb(4)Mo(5)P(2)O(22), orthorhombic, space group C222(1) (No. 20), a = 6.5300(5) Å, b = 19.7834(18) Å, c = 17.3451(15) Å, V = 2240.7(3) Å(3), and Z = 4.

The heteropolymolybdate family: structural relations, nomenclature scheme and new species

AbstractType specimens of the molybdoarsenates betpakdalite, natrobetpakdalite and obradovicite and the molybdophosphates mendozavilite, paramendozavilite and melkovite, and similar material from other sources, have been examined in an effort to elucidate the relations among these phases, which we designate as the heteropolymolybdate family of minerals. Using electron microprobe analysis, X-ray powder diffraction and single-crystal X-ray diffraction with crystal structure determination where possible, it was found that natrobetpakdalite, mendozavilite and melkovite are isostructural with betpakdalite and that obradovicite has a closely related structure.The betpakdalite and obradovicite structure types are based on frameworks containing four-member clusters of edge-sharing MoO6 octahedra that link by sharing corners with other clusters, with Fe3+O6 octahedra and with PO4 or AsO4 tetrahedra (T). The structures differ in the linkages through the Fe3+O6 octahedra, which produce different but closely related framework configurations. The structures contain two types of non-framework cation sites, which are designated A and B. In general, there are two or more A sites partially occupied by disordered, generally larger cations that are coordinated to O atoms in the framework and to H2O molecules. The B site is occupied by a smaller cation that is octahedrally coordinated to H2O molecules. The general formula for minerals with either the betpakdalite or the obradovicite structure is: [A2(H2O)nB(H2O)6][Mo8T2Fe3+3O30+7(OH)7–x], where x is the total charge of the cations in the A and B sites (+3 to +7) and n is variable, ideally 17 for arsenates and 15 for phosphates. The ideal total number of A cations is defined as 2 in the general formula, but varies from 1 to 3.8 in analysed samples. Dominant cations at the A site include K, Na and Ca and at the B site Na, Ca, Mg, Cu and Fe. The combinations that have been identified in this study define six new heteropolymolybdate species.A suffix-based nomenclature scheme is established for minerals of the betpakdalite, mendozavilite and obradovicite groups, with the following root names based on the structure types and the T-site cations: betpakdalite (T = As), mendozavilite (T = P) and obradovicite (T = As). Two suffixes of the form -AB, corresponding to the dominant cations in the two different types of non-framework cation sites complete the species name. The historical name melkovite is retained rather than introducing mendozavilite-CaCa.Our investigation of the paramendozavilite type specimen revealed no paramendozavilite, but an apparently closely related new mineral; however, another sample of paramendozavilite analysed had K > Na.

Pentaguanidinium monohydrogendiphosphopentamolybdate(VI) 2.5-hydrate, (CH6N3)5[HP2Mo5O23]·2.5H2O: hydrogen bonding and π-stacking in guanidinium cations

The asymmetric unit of the title compound consists of two crystallographically independent, but structurally identical, [HP(2)Mo(5)O(23)](5-) anions, ten guanidinium cations and five water molecules. Each singly protonated diphosphopentamolybdate(VI) anion retains the typical geometry of a ring of five edge-sharing MoO(6) octahedra [Mo...Mo = 3.3265 (8)-3.4029 (10) Å], except for one corner-sharing link [Mo···Mo = 3.6642 (7) and 3.6826 (8) Å]. Two capping PO(4) tetrahedra share corners with the five octahedra. Despite being surrounded by an extensive network of hydrogen bonds, predominantly from the guanidinium cations, short P-O-H···O=P contacts [O···O = 2.519 (7) and 2.457 (7) Å] associate the anions into infinite columns generated by the c-glide. In addition to their heavy involvement in hydrogen bonding, with all N-H donors being utilized, the guanidinium cations assemble into extensive π-stacked columns with an average interplanar spacing of 3.53 Å.

New assembly of organic components and transition metal complexes based on [VMo6O22]3− and [V2Mo6O26]6− building blocks: syntheses, crystal structures, and magnetic properties

Two new molybdovanadates, (H3NCH2CH2NH3)3 [Mo6VO22(CH3COO)3]·5H2O (1) and (H3NCH2CH2NH3)2{(Mo6V2O26)[Cu(NH2CH2CH2NH2)(H2O)2]}·4H2O (2), have been synthesized in aqueous solution and characterized by IR, UV–vis, single-crystal X-ray diffraction, thermal gravimetric, elemental analysis, and magnetic analysis. Compound 1 is a crown-shaped ring consisted of six edge-sharing MoO6 octahedra linked to a central {VO4} unit. The MoO6 octahedra are in pairs connected with the carboxylato ligands from three acetic acid molecules. Compound 1 is the first example of a molybdovanadate coordinated by acetic acid molecules. In addition, multipoint hydrogen-bonding interactions exist in 1, which bridge the crown-shaped [Mo6VO22 (CH3COO)3]6− clusters and the protonated ethylenediamine molecules into three-dimensional (3D) networks. The structural feature of compound 2 is the formation of one-dimensional (1D) zip-zag chain in which [Mo6V2O26]6− clusters are covalently bonded to copper coordination groups through the terminal oxygen of the {VO4} tetrahedron. The magnetic investigation on compound 2 demonstrates the possible occurrence of antiferromagnetic interactions by intermolecular linkage.

NaAg2Mo3O9AsO4

The title compound, sodium disilver arsenatotrimolybdate, Na0.93 (1)Ag2.07 (1)Mo3AsO13, was prepared by a solid-state reaction. In the crystal structure, isolated AsO4 tetra­hedra share corners with groups of three edge-sharing MoO6 octa­hedra. This arrangement leads to the formation of anionic 1 ∞[Mo3AsO13]n ribbons extending parallel to [100]. The three metal sites show occupational disorder by AgI and NaI cations, each with a different Ag:Na ratio. The metal cations are situated in the space between the ribbons and are surrounded by terminal O atoms of the ribbons in the form of distorted MO7 polyhedra (M = Ag, Na) for distances < 3.0 Å. The title compound shows weak ionic conductivity. Structural relationships between different compounds in the quaternary systems M–Sb–P–O, M–Nb–P–O and M–Mo–As–O (M is Ag or an alkali metal) are also discussed.

Monopotassium monosodium hexahydrogen α-hexamolybdoplatinate(IV) undecahydrate

The title compound, KNa[H6PtMo6O24]·11H2O, contains a discrete hexa­molybdoplatinate(IV) [H6PtMo6O24]2− poly­anion (1 symmetry), which has the highest level of protonation. Five O atoms of the central PtO6 octa­hedron (μ3-atoms, Oc) and one O atom of an outer edge-sharing MoO6 octa­hedron (O bridging μ2-atom, Ob) are protonated. The polyanions are connected by almost linear O—H⋯O hydrogen bonds between protonated and unprotonated Ob atoms. Further consolidation of the crystal structure is accomplished by extensive O—H⋯O hydrogen bonding involving the uncoordinated water mol­ecules. The two independent K+ cations are equally disordered about a twofold rotation axis.

Metal oxide-organic frameworks (MOOFs), a new series of coordination hybrids constructed from molybdenum(vi) oxide and bitopic 1,2,4-triazole linkers

A series of molybdenum(VI) oxide-organic solids were prepared by hydrothermal reactions employing N-donor tectons, which combine two 1,2,4-triazol-4-yl sites separated by representative aliphatic spacers (ethylene, tr(2)eth; 1,3-propylene, tr(2)pr; trans-1,4-cyclohexanediyl, tr(2)cy; diamondoid 1,3-adamantanediyl, tr(2)ad; 1,6- and 4,9-diamantanediyls, 1,6-tr(2)dia and 4,9-tr(2)dia) and heterofunctional 5-[4-(1,2,4-triazol-4-yl)phenyl]tetrazole (trtz). In all the compounds the 1,2,4-triazol-4-yl group acts as a short-distance N(1),N(2)-bridge between two Mo ions (Mo-N 2.36-2.50 A). The 3D framework structure is based upon pseudo-4(1) helices ([Mo(4)O(12)(tr(2)eth)(2)] 1, [Mo(2)O(6)(tr(2)cy)] 3) or sinusoidal chains ([Mo(2)O(6)(tr(2)pr)] 2, [Mo(2)O(6)(tr(2)ad)].6H(2)O 4, [Mo(2)O(6)(4,9-tr(2)dia)].0.5H(2)O 5) of vertex-sharing MoO(4)N(2) octahedra, while the bitopic organic ligands manifest a dual role as connectors for two adjacent octahedra and as links between separate 1D inorganic subtopologies. For linear, lengthy tectons tr(2)cy and 4,9-tr(2)dia two identical frameworks interpenetrate. In [MoO(3)(trtz)] 7, the 4(1) helices aggregate into 3D tetragonal framework (five-fold interpenetrated) by hydrogen bonding between the tetrazole groups. The 2D structure of [Mo(4)O(12)(1,6-tr(2)dia)].2H(2)O 6 is influenced by the very bulky aliphatic portion of the ligands, which connect chains of edge-shared octahedra MoO(5)N (Mo-N 2.346(2), 2.456(2) A).

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, (C(4)H(7)N(2))(3)[NaMo(8)O(26)(C(4)H(6)N(2))(2)], prepared from an aqueous solution containing Na(2)MoO(4) and 1-methylimidazole, contains the novel chain-like anion (infinity)(1)[NaMo(8)O(26)(mim)(2)](3-) (mim is 1-methylimidazole). The [Mo(8)O(26)(mim)(2)](4-) building unit, which lies across a center of inversion, is comprised of eight edge-sharing MoO(6) and MoO(5)(N(mim)) octahedra. These molybdate units are interlinked by sodium, itself exhibiting a sixfold coordination with O atoms.

Poly[propane-1,3-diammonium [tetra-μ3-oxo-hexaoxotrimolybdenum(VI)] dihydrate

The crystal structure of the title compound, [(C(3)H(12)N(2))[Mo(3)O(10)].2H(2)O](n), is composed of [Mo(3)O(10)](2-) anionic chains, propane-1,3-diammonium cations and solvent water molecules. The [Mo(3)O(10)](2-) chain is constructed from edge-sharing MoO(6) octahedra. The protonated propane-1,3-diamine cations and solvent water molecules are located between the chains and are linked to the O atoms of the inorganic chains by hydrogen bonds.

Synthesis and Crystal Structure of K6Mo10O33

A new potassium molybdenum oxide, K6Mo10O33, was synthesized by solid state reaction from the appropriate quantities of pre-dried MoO3 and K2MoO4, fired at around 650 °C for 2 d. The structure has been solved by using single crystal X-ray diffraction. The compound adopts the space group P1, with the lattice constants a = 7.7100(5), b = 11.9659(8), c = 17.1321(12) A° , α = 86.42 (10), β = 77.18(10), γ = 74.14(10)°. The structure is built up of infinite chains of edge-sharing MoO6 octahedra and groups of four MoO6 octahedra forming Mo4O17 units. These sub-units are connected together by common vertices.

Dipotassium heptahydrogenhexamolybdochromate(III) octahydrate, the first heptaprotonated Anderson-type polyoxometalate

The title compound, K2[H7CrMo6O24]·8H2O, contains an unexpectedly protonated polyanion, [H7CrMo6O24]2− in the B series Anderson-type heteropolyoxomolybdate. It was obtained by recrystallizing K3[H6CrMo6O24]·nH2O at pH 1.80. The asymmetric unit contains two crystallographically independent polyanions that have Ci (\overline{1}) symmetry. Six O atoms of the central CrO6 octa­hedron and one atom of an edge-shared MoO6 octa­hedron are protonated.

Dipotassium hexahydrogen hexamolybdoplatinate(IV) hexahydrate

The title compound, K2[H6PtMo6O24]·6H2O, containing the hexa­molybdoplatinate(IV) polyanion with the highest level of protonation, was isolated at pH 1.60. The anion has the Pt atom at an inversion center and exhibits a local symmetry close to \overline{3}m. Four O atoms of the central PtO6 octa­hedron and two O atoms of the edge-shared MoO6 octa­hedron are protonated. One K+ ion and one O atom of a water mol­ecule are located on twofold axes; the positions of a second K+ ion and one water mol­ecule, both on general sites, are half-occupied.

H3[AlMo6(OH)6O18]·10H2O

The title compound, trihydrogen hexa­hydroxoocta­deca­oxo­aluminiumhexa­molybdate deca­hydrate, crystallizes from an aqueous solution of potassium molybdate and aluminium(III) chloride. The structure features [Al(OH)6Mo6O18]3− clusters consisting of six edge-sharing MoO6 octa­hedra, which are arranged hexa­gonally around a central {Al(OH)6} octa­hedron. The overall symmetry of the Al(OH)6Mo6O18 unit is \overline{1}.

Monopotassium monosodium hexahydrogen α-hexamolybdoplatinate(IV) hexahydrate

The title compound, KNa[H6α-PtMo6O24]·6H2O, containing the hexa­molybdoplatinate(IV) polyanion with the highest level of protonation, was isolated at pH = 0.48. The anion has the Pt atom at an inversion center and has local symmetry close to \overline 3m; there are two independent half-anions in the asymmetric unit. Four O atoms of the central PtO6 octa­hedron and two O atoms of the edge-shared MoO6 octa­hedron are protonated. One Na atom occupies an inversion center.

Na2Te3Mo3O16: A New Molybdenum Tellurite with Second-Harmonic Generating and Pyroelectric Properties

The synthesis, structure, and characterization of a new noncentrosymmetric molybdenum tellurite, Na2Te3Mo3O16, are reported. Na2Te3Mo3O16 crystallizes in the noncentrosymmetric monoclinic space group I2 (No. 5, cell choice 3) with a = 7.3373(10) A, b = 11.2668(16) A, c = 8.2369(18) A, and β = 97.387(3)°. The material exhibits a quasi-one-dimensional crystal structure, with each chain consisting of edge-shared MoO6 octahedra that are connected by TeO3 and TeO4 polyhedra. The SHG efficiency of Na2Te3Mo3O16, using 1064 nm radiation, is approximately 500 × α-SiO2 and is phase-matchable (type 1). The strong SHG efficiency is maintained up to the melting temperature. The maximum polarization is 0.189 μC/cm2 at 25 kV/cm, and the pyroelectric coefficient (total effect), p, is −2.6 μC/m2 K.