Energetic and topological analysis of the reaction of Mo and Mo2 with NH3, C2H2, and C2H4 molecules

The Density functional theory has been applied to characterize the structural features of Mo(1,2)-NH(3),-C(2)H(4), and -C(2)H(2) compounds. Coordination modes, geometrical structures, and binding energies have been calculated for several spin multiplets. It has been shown that in contrast to the conserved spin cases (Mo(1,2)-NH(3)), the interaction between Mo (or Mo(2)) and C(2)H(4) (or C(2)H(2)) are the low-spin (Mo-C(2)H(4) and -C(2)H(2)) and high-spin (Mo(2)-C(2)H(4) and -C(2)H(2)) complexes. In the ground state of Mo(1,2)-C(2)H(4) and -C(2)H(2), the metal-center always reacts with the C-C center. The spontaneous formation of the global minima is found to be possible due to the crossing between the potential energy surfaces (ground and excited states with respect to the metallic center). The bonding characterization has been performed using the topological analysis of the Electron Localization Function. It has been shown that the most stable electronic structure for a pi-acceptor ligand correlates with a maximum charge transfer from the metal center to the C-C bond of the unsaturated hydrocarbons, resulting in the formation of two new basins located on the carbon atoms (away from hydrogen atoms) and the reduction of the number of attractors of the C-C basin. The interaction between Mo(1,2) and C(2)H(4) (or C(2)H(2)) should be considered as a chemical reaction, which causes the multiplicity change. Contrarily, there is no charge transfer between Mo(1,2) and NH(3), and the partners are bound by an electrostatic interaction.     

新型的含硫族元素碳硼烷配体的三(3，5-二甲基-1-吡唑)硼氢钼配合物的合成和分子结构(英)

三齿单核三(3，5-二甲基-1-吡唑)硼氢钼配合物Tp^*Mo(O)Cl₂ (1)(Tp^*=三(3，5-二甲基-1-吡唑)硼氢HB(C₃H(Me₂)N₂)₃)与含硫族元素碳硼烷的锂盐[(THF)₂LiE₂C₂B₁₀H₁₀(THF)]<     

硼掺杂还原态氧化石墨烯催化剂的制备及其蒽催化加氢性能的研究

制备了一系列硼掺杂的还原氧化态石墨烯催化剂并应用于蒽加氢反应。结果表明，随着催化剂处理温度的升高，催化剂中有序碳结构会发生变化，硼会取代材料骨架中的碳，进而影响蒽和氢气的吸附活化。经硼改性后，催化剂对蒽加氢反应表现出了很高的加氢活性，蒽的最高转化率可达97%，深度加氢产物八氢蒽的最高选择性可达19%。     

EFFECT OF MOLYBDENUM PROMOTER ON THE Cu-Co BASED CATALYSTS

The synthesis of mixed alcohols (C1-C5) from syngas has been studied at 6. 0 MPa over modified Co/CuLaZr catalysts. The molybdenum addition enhanced greatly the activity and the selectivity to alcohols. The improvement of hydrogenation capacity of the system via a reversible spillover effect of hydrogen could explain this effect, together with a great capacity of CO insertion, illustrated by the effect of C2H4 addition as a probe to syngas. Under our experimental conditions, a mixed alcohol production of 147.1g/kg. cat/h containing a proportion of 33. 1% of higher alcohols (C2 OH) was obtained with a selectivity to ROH of 52. 8%.     

不同环大小分子筛对钼基分子筛催化剂上甲烷无氧芳构化反应的影响

 钼基分子筛催化剂，由于不同分子筛的孔道大小及孔道形状不同\r\n，对甲烷芳构化反应表现出不同的催化性能．具有8元环孔道结构的小\r\n孔ERS－7分子筛没有催化活性，说明甲烷的芳构化反应离不开分子筛孔\r\n道的择形作用，较小的孔道中不能生成苯等芳烃．具有10元环孔道结构\r\n的ZSM－5，ZSM－11和ZRP－1三种分子筛具有较好的催化性能，但由于\r\n其孔道大小及孔道形状的差别在催化行为上表现出一定的差异．具有1\r\n0元环和12元环孔道结构的MCM－22分子筛，尤其对苯等轻芳烃而言，催\r\n化性能最佳．具有12元环孔道结构的JQX－1以及中孔分子筛SBA－15，\r\n虽然具有一定的催化性能，但活性较低．研究结果表明，孔道大小与苯\r\n分子动态直径相近或孔道稍大的分子筛是催化甲烷芳构化反应的良好载\r\n体，孔道过大或过小都不利于苯和萘等芳烃的生成．     

2,5-Dimethylthiophene coordination to three metal centers in the complexes (η4, S-μ3-2,5-Me2T)(IrCp*) [M(CO)2Cp]2 where MMo or W

The 2,5-dimethylthiophene (2,5-Me₂T) ligand in the isomers Cp*Ir(η⁴-2,5-Me₂T) (1) and Cp*Ir(C,S-2,5-Me₂T) (2) is activated to react with the dimers Cp(CO)₂M?M(CO)₂Cp[M?Mo (3), W (4)] to give complexes (5,6) in which the thiophene is coordinated to three metals. Oxidation of 5 with Cp₂Fe⁺ removes the Mo dimer to give Cp*Ir(η⁵-2,5-Me₂T)²⁺. Reaction of 5 with CO displaces the Mo as [CpMo(CO)₃]₂ to give Cp*Ir(CO)(C,S-2,5-Me₂T) (7). Ultraviolet photolysis of 1 provides a convenient route to the ring-opened isomer 2. Despite the remarkable nature of the thiophene coordination in 5 and 6, its reactivity does not suggest new pathways that would lead to the hydrodesulfurization of thiophenes.     

Selective Oxidation of Methane to Methanol Using Molecular Oxygen on MoOx／（LaCoO3＋Co3O4） Catalysts

Comparatively high CH3OH selectivity (60.0%) and yield (6.7%) were obtained on MoOx/(LaCoO3 Co3O4) catalysts in selective oxidation of methane to methanol using molecular oxygen as oxidant. The interaction between MoOx and La-Co-oxide modified the molecular structure of molybdenum oxide and the ratio of O^-/O^2- on the catalyst surface, which controlled the catalytic performance of MoOx/(LaCoO3 Co3O4) catalysts.     

Selective Electroanalytical Assay for Cysteine at a Boron Doped Diamond Electrode

The electrochemical oxidation of the cysteine‐quinone adduct has been examined as a means of providing an electroanalytical cysteine specific detection protocol. The appliance of square‐wave voltammetry allowed 0.5 μM as a limit of detection. The effects of various biologically relevant interferences including other thiols were studied and found to present no change in the voltammetric profile. The practical applicability and efficiency of the methodology was probed through the determination of cysteine concentration in growth tissue medium.     

Quantum chemical modeling of CO oxidation by the active site of molybdenum CO dehydrogenase

The catalytic mechanism of molybdenum containing CO dehydrogenase has been studied using hybrid DFT methods with quite large chemical models. The recent high-resolution X-ray structure, showing the surprising presence of copper linked to molybdenum, was used as a starting point. A pathway was initially found with a low barrier for C-O bond formation and CO2 release. However, this pathway did not include the formation of any S-CO2 species, which had been suggested by experiments with an n-butylisocyanide inhibitor. When these SCO2 structures were studied they were found to lead to deep minima, making CO2 release much more difficult. A large effort was spent, including investigations of other spin states, varying the number of protons and electrons, adding water, etc., until a plausible pathway for S-C bond cleavage was found. In this pathway a water molecule is inserted in between molybdenum and the SCO2 group. Full catalytic cycles, including electron and proton transfers, are constructed both with and without S-C bond formation. When these pathways are extended to two full catalytic cycles it can be understood why the formation of the S-C bond actually makes catalysis faster, even though the individual step of CO2 release becomes much more difficult. These results agree well with experimental findings.