On the interaction of Mo and Mo2 with NH3, C2H4, and C3H6

The reactivity of Mo and Mo₂ with ammonia, ethene, and propene molecules has been investigated by using Density Functional Theory. Different gradient‐corrected and hybrid exchange‐correlation functionals have been employed. Coordination modes, binding energies, geometrical structures, vibrational frequencies have been computed and compared with the available experimental counterparts. The results obtained show that the molybdenum atom is able to react with C₂H₄ and C₃H₆, and binds weakly with NH₃. The dimer Mo₂ gives a stable complexes with ammonia, ethene, and propene. For the Mo₂NH₃ complex, all the employed levels of theory give binding energies in good agreement with the experimental value, while in the case of the MoC₂H₄ system, the use of model core potentials coupled with gradient‐corrected exchange‐correlation functionals overestimates the binding energies. For MoC₃H₆, Mo₂C₂H₄, and Mo₂C₃H₆ we predict a binding energy of 14–15, 20–24, and 18–20 kcal/mol, respectively. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1557–1564, 2001     

ChemInform Abstract: Sc0.43(2)Rb2Mo15S19, a Partially Sc‐Filled Variant of Rb2Mo15S19.

Single crystals of the title compound are obtained from a mixture of Sc₂S₃, Rb₂MoS₄, MoS₂, and Mo (Mo crucible, 1773 K, 48 h).     

ChemInform Abstract: Calculated Structures of MO22+, MN2, and MP2 (M: Mo,W).

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

Metal–metal bond energies in Mo2, Mo2Cl,and Mo2(O2CH)4

Previous attempts to determine the strengths of multiple metal-metal bonds are reviewed. Estimates of 73 and 97 kcal/mole for the Mo? Mo bond energies in Mo₂Cl and Mo₂(O₂CH)₄, respectively, are obtained by combining the known experimental bond energy in Mo₂ (96.5 ± 5 kcal/mole) with the results of SCF-Xα-SW calculations on Mo₂, Mo₂Cl, and Mo₂(O₂CH)₄. Possible errors in the estimates are discussed. It is noted that the quadruple bonds in the complexes are predicted stronger per component than the sextuple bond in the diatomic.     

ChemInform Abstract: Synthesis and Characterization of K3Mo14O22, K1.66Pb1.34Mo14O22, and K1.29Sn1.71Mo14O22: Oligomeric Clusters with Three Trans Edge-Shared Mo Octahedra.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

ChemInform Abstract: Li4Ge2B as a New Derivative of the Mo2B5 and Li5Sn2 Structure Types.

Single crystals of Li₄Ge₂B are obtained by solid state reaction of stoichiometric mixtures of the elements (sealed Ta crucible, 1473 K, 15 min; rapid cooling to 25 °C).     

Die Kristallstruktur des Komplexnitrides Mo(Ta,Mo)2N2

In the ternary system Ta/Mo/N a complex nitride of formula Mo(Ta,Mo)₂N₂ was observed at a nitrogen pressure of 360 bar and a temperature of 1,600°C. The crystal structure was determined from X-ray powder diagrams. The tetragonal unit cell, space groupI4/mmm-D _4h ¹⁷ , lattice parametersa=0.3051 nm,c=1.2530 nm contains ten atoms with an arrangement of the metal atoms corresponding to the MoSi₂-Type structure.

     

Rubidium dimolybdate,Rb2Mo2O7, and caesium dimolybdate,Cs2Mo2O7

The crystal structures of dirubidium hepta­oxodimolybdate, Rb₂Mo₂O₇, and dicaesium hepta­oxodimolybdate, Cs₂Mo₂O₇, in the space groups Ama2 and P2₁/c, respectively, have been determined for the first time by single‐crystal X‐ray diffraction. The structures represent two novel structure types of monovalent ion dimolybdates, A₂Mo₂O₇ (A = alkaline elements, NH₄, Ag or Tl). In the structure of Rb₂Mo₂O₇, Mo atoms are on a twofold axis, on a mirror plane and in a general position. One of the Rb atoms lies on a twofold axis, while three others are on mirror planes. Two O atoms attached to the Mo atom on a mirror plane are located on the same plane. Rubidium dimolybdate contains a new kind of infinite Mo–O chain formed from linked MoO₄ tetra­hedra and MoO₆ octa­hedra alternating along the a axis, with two terminal MoO₄ tetra­hedra sharing corners with each octa­hedron. The chains stack in the [001] direction to form channels of an approximately square section filled by ten‐coordinate Rb ions. Seven‐ and eight‐coordinate Rb atoms are located between chains connected by a c translation. In the structure of Cs₂Mo₂O₇, all atoms are in general positions. The MoO₆ octa­hedra share opposite corners to form separate infinite chains running along the c axis and strengthened by bridging MoO₄ tetra­hedra. The same Mo–O polyhedral chain occurs in the structure of Na₂Mo₂O₇. Eight‐ to eleven‐coordinate Cs atoms fill the space between the chains. The atomic arrangement of caesium dimolybdate has an ortho­rhom­bic pseudosymmetry that suggests a possible phase transition P2₁/c→Pbca at elevated temperatures.     

ChemInform Abstract: Group 6 Dioxydichlorides MO2Cl2 (M: Cr,Mo, W,and Element 106, Sg): The Electronic Structure and Thermochemical Stability.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

Die Kristallstruktur von Mo2FeB2

Zusammenfassung Mo₂FeB₂ wird aus den Elementen synthetisiert. Diese Phase ist mit U₃Si₂ isotyp, jedoch mit Ordnung der Mo- und Fe-Atome.     

ChemInform Abstract: Low-Temperature Syntheses and Characterization of Novel Layered Tellurites,A2Mo3TeO12 (A: NH4, Cs), and “Zero-Dimensional” Tellurites,A4Mo6Te2O24×6H2O (A: Rb,K).

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

含金属-金属多重键原子簇化合物Mo2I4(NCR)4体系光谱研究

使用INDO/CI程序计算了含金属-金属多重键的钼原子簇化合物Mo₂I₄(NCR)₄(R=Me,Et,Ph)体系的电子光谱,所得波数及强度与实验符合.在谱带指认分析中,除看到已知的δ_d→δ_d^*跃迁外,还看到了新的金属多重键具有的π_d→σ_p-s(M)跃迁.说明R=Me,Et,Ph次序变化的取代基效应引起的体系第一吸收带红移.对Mo≡Mo键的性质也进行了讨论.     

Synthese und Struktur von Mo2NCl8 und Mo3N2Cl11

Synthesis and Crystal Structure of Mo_2<>NCl₈ and Mo₃N₂Cl₁₁ The reaction of MoCl₅ with Cl₃VNCl at 140 °C in a sealed glass ampoule yields air sensitive black crystals of the mixed valent molybdenum(V, VI) nitride chloride, Mo₂NCl₈. It crystallizes in the monoclinic space group P2/c with a = 996.1(1), b = 629.4(1), c = 1780.8(3) pm, β = 101.82(2)°, and Z = 4. The crystal structure consists of dinuclear C₂‐symmetrical units [Cl₂(N≡)Mo(μ₂‐Cl)₃Mo(≡N)Cl₂]^— and [Cl₄Mo(μ₂‐Cl)MoCl₄]⁺, connected in an alternating sequence by asymmetric nitrido bridges Mo≡N‐Mo to form chains. The reaction of Cl₃VNCl with MoCl₃ at 140 °C affords Mo₃N₂Cl₁₁, but for the prolonged reaction period, MoNCl₃ is observed in addition. Mo₃N₂Cl₁₁ can also be obtained from MoNCl₃ and MoCl₅ (2:1) at 140 °C. It forms orthorhombic, black crystals with the space group Pca2₁ and a = 1256.1(1), b = 1001.9(1), c = 1330.10(5) pm, and Z = 4. The structure contains the same dinuclear units [Cl₂(N≡)Mo(μ₂‐Cl)₃Mo(≡N)Cl₂]^— as in Mo₂NCl₈, which in this case are connected with MoCl₄⁺ moieties by asymmetric nitrido bridges Mo≡N‐Mo forming chains. In Mo₂NCl₈ the Mo‐N distances in the nearly linear nitrido bridges are 167.6(2), and 214.8(2) pm, whereas in case of Mo₃N₂Cl₁₁ two sets of Mo‐N distances of 166, 8(4) and 214, 0(4) pm as well as 166, 9(4) and 211, 9(4) pm are observed.     

Activation and properties of Mo=O bonds in Mo/SiO2 catalysts

The existence of the charge transfer excited triplet state [Mo⁵⁺-O^-] produced by UV-irradiation of Mo/SiO₂ catalysts, and its reactivity are evidenced by experiments of photoluminescence, photoinduced metathesis, and photoreduction of CO. Mo⁵⁺ ions can be produced separately by thermal activation and O^- ions by further adsorption of N₂O on those Mo⁵⁺ ions. The latter of which are adsorbed on Mo⁶⁺ ions are found to be more reactive than O^2- of [Mo⁶⁺ =O^2-] bond. They are able either to add a molecule such as CO or C₂H₄, or to abstract hydrogen from H₂, CH₄ or trans-dicyanoethylene, or a CN group form tetracyanoethylene (TCNE). The Mo⁵⁺ ions are able to coordinate gas phase ligands when their coordination sphere possesses vacant sites. This is the case for tetracoordinated Mo⁵⁺ _4c ions arising from reduction of tetrahedral Mo⁶⁺ ions (Eq. (7)). These Mo⁵⁺ _4c ions are similar to those produced by UV-irradiaiion (Eq. (2)). In addition, if the adsorbed molecule has a sufficiently large electron affinity, such as TCNE or O₂, an electron transfer can occur (Eq. (9) and (17)). The [Mo⁵⁺-O^-] bond obtained by thermal activation is more difficult to evidence than that obtained with UV-activation because it is not detectable by EPR. However, the EPR results obtained at low temperature show that the O^- ions adsorbed on Mo/SiO₂ catalysts as well as the [Mo⁵⁺-O^-] excited triplet state obtained by UV-irradiation of 1Mo⁶⁺=O²] interact with methanol (Eq. (16)). They are consistent with the mechanism of methanol oxidation occurring at high temperature (Eq. (4)).     

Structure and Energy of Mo27SxCy Clusters: A Density Functional Theory Study

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.     

Ag2.54Tl2Mo12Se15: a new structure type containing Mo6 and Mo9 clusters

The novel structure‐type Ag_2.54Tl₂Mo₁₂Se₁₅ (silver thallium molybdenum selenide) is built up of Mo₆Seⁱ₈Se^a₆ and Mo₉Seⁱ₁₁Se^a₆ cluster units in a 1:2 ratio, which are three‐dimensionally connected to form the Mo–Se network. The Ag and Tl cations are distributed in several voids within the cluster network. Three of the seven independent Se atoms and one Tl atom lie on sites with 3.. symmetry (Wyckoff sites 2c or 2d).