The crystal structure of (NH4)2[Mo2(S2)6].8/3H2

The black crystal of (NH₄)[Mo₂(S₂)₆]* 8/3 H₂O belongs to the orthorhombic system, space group D³₂-P22₁2₁, with a = 12.064(6), b = 12.534(4), c = 19.558(9)Å, V =2957(3)ų, Z = 4 and D_c = 2.23g.cm^?3. The intensity data were collected on a Syntex R3 four-circle diffractometer. The structure was solved by Patterson method and direct method, the light atoms (except H atoms) were obtained from ΔF syntheses. The structure was refined by least-squares with anisotropic thermal parameters. The values of R and R_w were 0.092 and 0.072 respectively. The crystal structure contains discrete dimeric cluster [Mo₂(S₂)₆]^2? ions, NH₄⁺ cations and H₂O molecules. There are two crystallographically independent [Mo₂S₂)₆]^2? ions in the crystal, one locates on general position [Figure 1(a)], the other locates on two-fold axis [Figure 1(b)]. It contains one and a half [Mo₂S₂)₆]^2? ions in an asymmetric unit. In [Mo₂S₂)₆]^2? each Mo is coordinated side on by four S₂^2? groups in a distorted dodecahedral arrangement, two of which are bridging and the other two are terminal. The Mo? S bond length is 2.441 Å (mean), and S? S is 2.049 Å (mean). The Mo? Mo distance is 2.784 Å (mean), which is to be regarded as a single bond length. The formal oxidation state of Mo is five, it is probably a mixed valence Mo^IV? Mo^VI, and so shows a remarkable deep colour.     

The First Titanium Molybdenum Antimonide: Ti5.42Mo2.58Sb9, a Substitution Variant of Zr2V6Sb9

The new ternary antimonide Ti_5.42(2)Mo_2.58Sb₉ was uncovered by a reaction of the elements under exclusion of air at 1150 °C. It crystallizes in a ternary substitution variant of the V_7.5Sb₉ type, a structure not known to exist in either the Ti/Sb or the Mo/Sb system. The crystal structure of Ti_5.42Mo_2.58Sb₉ was determined from single crystal X‐ray data: space group P4/nmm, with a = 9.8178(8) Å, c = 7.1857(8) Å, V = 692.6(1) ų, Z = 2, R1 = 0.025, wR2 = 0.052 (all data). The structure contains four metal atom sites, two thereof occupied solely by Ti atoms, and two by different Ti/Mo mixtures. The former two correspond to the Zr sites, and the latter two to the V sites of the isostructural antimonide Zr₂V₆Sb₉. The crystal structure is comprised of chains of face‐sharing TiSb₈ square antiprisms, Ti/Mo tetrahedra and Sb atom pairs and squares. The electronic structure, computed with the LMTO approximation, is indicative of metallic properties. In addition to the dominating metal–Sb bonds, strong metal–metal and Sb–Sb bonds exist as well in Ti_5.42Mo_2.58Sb₉. The Mo content per metal site increases with increasing metal–metal interactions.     

Non-Dissociative Activation of Chemisorbed Dinitrogen on One or Two Vanadium Atoms Supported by a Mo6S8 Cluster

Adsorption of N₂ on Mo₆S₈^q_V_x clusters (x=0, 1, 2; q=0, ±1) were systematically studied by density functional theory calculations with dispersion corrections. It was found that the N₂ can be chemisorbed and undergo non-dissociative activation on single or double metal atoms. The adsorption and activation are influenced by metal types (V or Mo), N₂ coordination modes and charge states of the clusters. Particularly, anionic Mo₆S₈⁻_V₂ clusters have remarkable ability to fix and activate N₂. In Mo₆S₈⁻_V₂, two V atoms prefer to adsorb on two adjacent S−Mo−S hollow sites, leading to the formation of a supported V…V unit. The N₂ is bridged side-on coordinated with these two V atoms with high adsorption energy and significant charge transfer. The bond order, bond length and vibration frequency of the adsorbed N₂ are close to those of a N−N single bond.     

Structural behavior of the ferromagnetic spinels AlxMo2S4 and GaxMo2S4, containing tetrahedral clusters of molybdenum atoms

The structure of the ferromagnetic spinels Al_xMo₂S₄ and Ga_xMo₂S₄ (x ～ 0.5) was determined from powder diffraction data. The Al and Ga atoms order on the tetrahedral sites. The space group is $\text{F}\text{4}\text{3m; a = 9.726}$ Å for Al_xMo₂S₄ and 9.739 Å for Ga_xMo₂S₄. The Mo atoms were found to shift towards the tetrahedral site vacancies, created by the lower Al and Ga concentrations. This results in tetrahedral clusters of Mo around the vacancies. Their semiconducting and magnetic behavior was explained on the basis of the structural behavior of the molybdenum lattice in these spinel compounds.     

Cs2Mo15S19: a novel ternary reduced molybdenum sulfide containing Mo6 and Mo9 clusters

The crystal structure of dicaesium pentadecamolybdenum nonadeca­sulfide, Cs₂Mo₁₅S₁₉, consists of a mixture of Mo₆S₈S₆ and Mo₉S₁₁S₆ cluster units in a 1:1 ratio. Both units are interconnected via inter‐unit Mo—S bonds. The Cs⁺ cations occupy large voids between the different cluster units. The Cs and two inner S atoms lie on sites with 3 symmetry (Wyckoff site 12c) and the Mo and S atoms of the median plane of the Mo₉S₁₁S₆ cluster unit on sites with 2 symmetry (Wyckoff site 18e).     

Fe and Cr K‐edges EXAFS Study of Double Perovskite (Sr2‐xCax)FeMoO6 (0 ≤ x ≤ 2.0) and Sr2CrMO6 (M = Mo,W) Systems

The local structure of the double perovskite (Sr_2‐xCa_x)FeMoO₆ (0 ≤ × ≤ 2.0) and Sr₂CrMO₆ (M = Mo, W) systems have been probed by extended X‐ray absorption fine structure (EXAFS) spectroscopy at the Fe and Cr K‐edges. We found Fe‐O (ave) distance apparently decreases from 1.999 Å (x = 0) to 1.991 Å (x = 1.0) in (Sr_2‐xCa_x)FeMoO₆ (tetragonal structure). When x is increased further from 1.5 to 2.0, the Fe‐O bond distance decreased from 2.034 Å to 2.012 Å (monoclinic structure). In addition, Cr‐O, Sr‐Cr, and Cr‐Mo bond distances in Sr₂CrWO₆ are all slightly larger than the bond distances of Sr₂CrMoO₆, which is due to the ionic radius of the W⁵⁺ (0.62 Å) which is larger than the ionic radius of Mo⁵⁺ (0.61 Å). The results are consistent with our XRD refinements data.     

Tailoring Heterometallic Cluster Functional Building Blocks: Synthesis,Separation, Structural and DFT Studies of [Re6−xMoxSe8(CN)6]n−

Influence of the metal core composition and geometry on the structure, spectroscopic properties and redox potentials was investigated for the first time for heterometallic (Re/Mo)₆ octahedral clusters. The discrete anionic clusters [Re_6-xMo_xSe₈(CN)₆]ⁿ⁻ (x=2, 3; n=4, 5) were obtained as individual salts. Their isomeric composition and bond-length distribution were inspected using a combination of single-crystal X-ray structure analysis, NMR, EXAFS, and DFT calculations.     

Sc0.43(2)Rb2Mo15S19, a partially Sc‐filled variant of Rb2Mo15S19

The structure of scandium dirubidium pentadecamolybdenum nonadecasulfide, Sc_{0.43 (2)}Rb₂Mo₁₅S₁₉, constitutes a partially Sc‐filled variant of Rb₂Mo₁₅S₁₉ [Picard, Saillard, Gougeon, Noel & Potel (2000), J. Solid State Chem. 155 , 417–426]. In the two compounds, which both crystallize in the Rc space group, the structural motif is characterized by a mixture of Mo₆Sⁱ₈S^a₆ and Mo₉Sⁱ₁₁S^a₆ cluster units (`i' is inner and `a' is apical) in a 1:1 ratio. The two components are interconnected through interunit Mo—S bonds. The cluster units are centred at Wyckoff positions 6b and 6a (point‐group symmetries and 32, respectively). The Rb⁺ cations occupy large voids between the different cluster units. The Rb and the two inner S atoms lie on sites with 3. symmetry (Wyckoff site 12c), and the Mo and S atoms of the median plane of the Mo₉S₁₁S₆ cluster unit lie on sites with .2 symmetry (Wyckoff site 18e). A unique feature of the structure is a partially filled octahedral Sc site with symmetry. Extended Hückel tight‐binding calculations provide an understanding of the variation in the Mo—Mo distances within the Mo clusters induced by the increase in the cationic charge transfer due to the insertion of Sc.     

One-dimensional condensation of Mo6 octahedral clusters: A new cluster,Mo12, and a new building block,Mo12S14, in M2Mo9S11

Two new Mo compounds, Tl₂Mo₉S₁₁ and K₂Mo₉S₁₁, have been found. The structure of these compounds is characterized by the presence of a completely new building block, Mo₁₂S₁₄, in addition to the well-known Mo₆S₈ unit as in the PbMo₆S₈-type compounds. The new cluster, Mo₁₂, contained in the Mo₁₂S₁₄ unit can be considered as a one-dimensional condensation of three Mo₆ octahedral clusters. These new materials, the structure of which resembles that of PbMo₆S₈, are metallic but are not superconducting above 2.1°K.     

A decanuclear oxomolybdenum(V,VI) cluster with 4-isopropylpyridine

The title centrosymmetric cluster octakis(4-iso­propyl­pyridine-N)-di-μ₄-oxo-hexa-μ₃-oxo-octa-μ₂-oxo-deca­oxo­octa­molyb­denum(V)­dimolybdenum(VI), [Mo₁₀O₂₆(C₈H₁₁N)₈], consists of ten Mo atoms connected together by bridging oxo groups. Pentavalent Mo atoms are linked into four Mo₂^V pairs by metal–metal single bonds with lengths of 2.5637 (6) and 2.6132 (6) Å.     

Molybdänhalogenidcluster mit sechs terminalen Alkoholatliganden: (C18H36N2O6Na)2[Mo6Cl8(OCH3)6] · 6CH3OH und (C18H36N2O6Na2)2[Mo6Cl8(OC6H5)6]

Molybdenum(II) Halide Clusters with six Alcoholate Ligands: (C₁₈H₃₆N₂O₆Na)₂[Mo₆Cl₈(OCH₃)₆] · 6CH₃OH and (C₁₈H₃₆N₂O₆Na)₂[Mo₆Cl₈(OC₆H₅)₆] . The reaction of Na₂[Mo₆Cl₈(OCH₃)₆] and 2,2,2-crypt yields (C₁₈H₃₆N₂O₆Na)₂[Mo₆Cl₈(OCH₃)₆] · 6 CH₃OH ( 1 ), which is converted to (C₁₈H₃₆N₂O₆Na)₂[Mo₆Cl₈(OC₆H₅)₆] ( 2 ) by metathesis with phenol. According to single crystal structure determinations ( 1 : P3 1c, a=14.613(3) Å, c=21.036(8) Å; 2 : P3 1c, a=15.624(1) Å, c=19.671(2) Å) the compounds contain anionic clusters [Mo₆Cl₈ⁱ(OR^a)₆]^2? ( 1 : d(Mo—Mo) 2.608(1) Å to 2.611(1) Å, d(Mo—Cl) 2.489(1) Å to 2.503(1) Å, d(Mo—O) 2.046(4) Å; 2 : d(Mo—Mo) 2.602(3) Å to 2.608(3) Å, d(Mo—Cl) 2.471(5) Å to 2.4992(5) Å, d(Mo—O) 2.091(14) Å). Electronic interactions of the halide cluster and the phenolate ligands in [Mo₆Cl₈(OC₆H₅)₆]^2? is investigated by means of UV/VIS spectroscopy and EHMO calculations.     

An open-framework cobalt molybdate possessing {Mo2O7} building block: hydrothermal synthesis and structural characterization of [CoMo2O7(4,4′-bipy)1.5]

The hydrothermal reaction of Co(COO)₂?·?4H₂O, MoO₃, H₃PO₄ and 4,4′-bipyridine yields bipyridine-ligated cobalt dimolybdate [CoMo₂O₇(4,4′-bipy)_1.5] (1) (4,4′-bipy?=?4,4′-bipyridine) in the triclinic system with space group of P 1 and cell parameters of a?=?7.1951(8)?Å, b?=?11.1708(17)?Å, c?=?11.4514(11)?Å, α?=?98.545(7)°, β?=?90.315(2)°, γ?=?105.777(5)°, V?=?874.88(19)?ų, and Z?=?2. Its structure consists of Co/Mo/O bimetal oxide layers with {Mo₂O₇} building blocks, linked by the coordination of 4,4′-bipy ligand with Co and Mo atoms, into a 3D porous hybrid framework.     

Synthesis and structure of an open-type trinuclear molybdenum cluster compound[Mo_3(μ_3-S)(μ-S)_2-(μ-OAc)(S_2CNC_4H_8)_3(O)_2]·0.5CH_2Cl_2·2H_2O

The title compound was prepared by the reaction of Mo_3S_4(dtp)_4(H_2O)[ctp=S_2P(OEt)_2]with NaOAc·3H_2O and C_4H_8NCS_2NH_4.Crystallographic data:[Mo_3(μ_3-S)(μ-S)_2(μ-OAc)-(S_2CNC_4H_8)_3(O)_2]·0.5CH_2CI_2·2H_2O,Mr=980.18,triclinic,space group P,α=12.360(3),b=16.653(6),c=9.206(2)A,α=101.97(2),β=108.32(2),γ=86.14(3)°.V=1759.6(9)A~3,Z=2,Dc=1.85 g/cm~3,F(000)=962,μ(Mo K_α)=16.53 cm~(-1).Final R=0.044 for 4301 reflections with I≥3σ(I).This compoundmay be regarded as a mixed-valent trinuclear molybdenum cluster{Mo_2(V)Mo(Ⅳ)(μ_3-S)(μ-S)_2-(μ-OAc)(S_2CNC_4H_8)_3(O)_2}.The Mo-Mo distances are 2.783(1),2.833(1)and 3.374(2)A in the Mo_3non-equilateral triangle and there exist only two Mo-Mo bonds.The cluster was obtained by oxi-dation and ligand substitution of{Mo_3(μ_3-S)(μ-S)_3[μ-S_2P(OEt_2)][S_2P(OEt)_2]_3(H_2O)}.     

Darstellung der supraleitenden ternären Phase PbMo6S8 durch chemischen Transport

Preparation of the Superconducting Ternary Phase PbMo₆S₈ by Chemical Transport Reactions The only ternary phase existing in the system Pb? Mo? S is the superconducting compound Pb_xMo₆S_y (PMS). It can be transported by CTR using PbBr₂ if an equilibrium mixture of PMS and Mo is present at the starting side, or if there is the pure PMS phase not exceeding a critical sulphur content. The transport conditions were deduced from a thermodynamical analysis of the system Pb? Mo? S? Br. Now it can be stated that all condensed phases occuring in the Pb? Mo? S system can be deposited from vapour phase by CTR or by sublimation: Pb, Mo, S, PbS, Mo₂S₃, MoS₂, PMS.     

Sn4.4Mo24O38

The single‐crystal structure of tetratin tetracosa­molybdenum octatriaconta­oxide, Sn_4.4Mo₂₄O₃₈, contains infinite chains of centrosymmetric dioctahedral Mo₁₀ and centrosymmetric trioctahedral Mo₁₄ clusters. These clusters, as well as the O atoms, the arrangement of which derives from a closest‐packing with the layer sequence …ABAC…, form sheets parallel to the ac plane of the monoclinic unit cell. The Mo—Mo distances range from 2.6225 (7) to 2.8212 (9) Å and from 2.6270 (7) to 2.8365 (7) Å in the Mo₁₀ and Mo₁₄ clusters, respectively. The Mo—O distances vary between 1.949 (4) and 2.151 (4) Å in the Mo₁₀ cluster and between 1.938 (4) and 2.140 (4) Å in the Mo₁₄ cluster. The three crystallographically independent Sn²⁺ ions are off the centre of distorted oxy­gen octahedra.     

Synthesis and crystal structure of Mo6−x Nb x I11 (x = 1–1.5)

A solid solution Mo_{6 ? x} Nb _x I₁₁ (x = 1.1–1.5) containing cluster cores {Mo₅NbI₈} is obtained by the high-temperature reaction of molybdenum, niobium, and iodine (550°C, 70 h, quartz ampule). According to the X-ray diffraction data, heating at 800°C in a molybdenum container results in the decomposition of the solution to Mo₆I₁₂ and Nb₆I₁₁. According to the X-ray structure analysis data, the compounds are isostructural to the high-spin modification Nb₆I₁₁ (space group Pccn). The presence of Nb atoms in the structure changes the structural type from the layered (Mo₆I₁₂) to framework structure, noticeably increases the metalmetal distances (2.661–2.716 Å, 2.695 Å) Mo₆ octahedron with the retention of the distance from the metal (M) to the μ₃-“capped” I atoms, and strongly elongates the M₆-I-M₆ bridges almost to the value observed in Nb₆I₁₁.     

Stabilization of Mo6S8 by halogens; new superconducting compounds: Mo6S6Br2, Mo6S6I2

We present a study of the properties of the series Mo₆X_8?xY_x (X = S, Se, Te; Y = Br, I) having the hexagonal rhombohedral structure of the PbMo₆S₈ type. For X = S we have found two new superconducting compounds Mo₆S₆Br₂ and Mo₆S₆I₂, having critical temperatures of 13.8 and 14.0°K, respectively. We further find that Mo₆Te₈ becomes superconducting (T_c ≈ 2.6°K) upon substitution of Te by small quantities of iodine, and that in the case of Mo₆Se₈ substitution of a Se atom by a halogen, raises T_c up to about 7.6°K.     

Molten salt synthesis (MSS) of Cu2Mo6S8—New way for large-scale production of Chevrel phases

The Chevrel phase (CP), Mo₆S₈, was found to be an excellent cathode material for rechargeable magnesium batteries. Mo₆S₈ is obtained by a leaching process of Cu₂Mo₆S₈, which removes the copper. A new method of Cu₂Mo₆S₈ production was developed. In contrast to the well-known solid-state synthesis of CP, the method is based on the reaction in a molten salt media (KCl). A fast kinetics of this reaction allows using less active, but more convenient precursors (sulfides instead of sulfur), decreasing temperature and synthesis duration, as well as operation in the inert atmosphere instead of dynamic evacuated systems. It was shown that the composition and the electrochemical behavior of the products obtained by MSS and by the solid-state synthesis are identical. Thus, the molten salt method is extremely attractive for the large-scale production of the active materials for Mg batteries.     

Some reduced ternary and quaternary oxides of molybdenum. A family of compounds with strong metal-metal bonds

Several new, reduced ternary and quaternary oxides of molybdenum are reported, each containing molybdenum in an average oxidation state <4.0. All are prepared by reactions between a molybdate salt; metal oxide, if needed; and MoO₂ sealed in Mo tubes held at 1100°C for ca. 7 days. Refinement of the substructure of the new compound Ba_0.62Mo₄O₆ was based on an orthorhombic cell, witha = 9.509(2), b = 9.825(2), c = 2.853(1)Å, Z = 2 in space groupPbam; weak supercell reflections indicate the true structure hasc = 8(2.853) Å. The chief structural feature is closely related to that of NaMo₄O₆ (C. C. Torardi, R. E. McCarley,J. Amer. Chem. Soc.101, 3963 (1979)), which consists of infinite chains of Mo₆ octahedral clusters fused on opposite edges, bridged on the outer edges by O atoms and crosslinked by MoOMo bonding to create four-sided tunnels in which the Ba²⁺ ions are located. The structure of Ba_1.13Mo₈O₁₆ is triclinic,a = 7.311(1), b = 7.453(1), c = 5.726(1)Å, α = 101.49(2), β = 99.60(2), γ = 89.31(2)°,Z = 1, space groupP1¯. It is a low-symmetry, metal-metal bonded variant of the hollandite structure, in which two different infinite chains, built up from Mo₄O^2?₈ and Mo₄O^0.26?₈ cluster units, respectively, are interlinked via MoOMo bridge bonding to create again four-sided tunnels in which the Ba²⁺ ions reside. Other compounds prepared and characterized by analyses and X-ray powder diffraction data arePb_xMo₄O₆(x ～ 0.6), LiZn₂Mo₃O₈, CaMo₅O₈, K₂Mo₁₂O₁₉, and Na₂Mo₁₂O₁₉.     

On the preparation of binuclear S,S bridged molybdenum(V) complexes crystal and molecular structure of [Mo2S4(Et2dtc)2]

MoO₄^2? is reduced by diethyldithiocarbamate (Et₂dtc^?) on prolonged digestion in aqueous medium whereby the complex [Mo₂^VO₂S₂(Et₂dtc)₂] is formed. The central moiety Mo₂O₂S₂²⁺ has a high formation tendency. When [Mo₂^V(S₂)₆]^2? is refluxed with Et₂dtc^? in ethanol, [Mo₂^VS (Et₂dtc)₂] is formed, the X-ray crystal structure of which has been determined (space group P2₁2₁2₁, a = 10.550(2) Å, b = 13.820(5) Å, c = 14.723(12) Å, d_c = 1.90 g · cm^3?, Z = 4). The Mo? Mo distance of the diamagnetic compound is 2.817(2) Å and the average Mo=S_t distance 2.099(4) Å.