The reaction of Mo(N)(CH2tBu)3 (1) and SiO2-(700) generates (SiO)Mo(NH)(CHtBu)(CH2tBu) (2) when performed in C6H6 (material [1/SiO2-(700)]C6H6). The grafting occurs presumably by protonation of the nitrido ligand to form an intermediate (SiO)Mo(NH)(CH2tBu)3 (3), a pentacoordinated complex, which decomposes into 2 and 2,2-dimethylpropane. While [1/SiO2-(700)]C6H6 is highly active in olefin metathesis, [1/SiO2-(700)]CH2Cl2 and [1/SiO2-(700)]THF are poorly active or inactive catalysts respectively. In contrast, when Mo(N)(CH2tBu)3 reacts with a molecular silanol derivative, a soluble model of the surface of SiO2-(700), it yields a very stable complex, (c-C5H9)7Si7O12SiO-Mo(NH)(CH2tBu)3 (3m), which does not spontaneously generate 2,2-dimethylpropane and an alkylidene complex in contrast to the surface complex. Moreover, 3m does not catalyse olefin metathesis at room temperature as it does not already contain the initiating carbene ligand, and it is necessary to heat up the reaction mixture to 110 °C to obtain low catalytic activity. Nevertheless, the complex 3m generates well-defined metallocarbenes when heated in the presence of PMe3: (c-C5H9)7Si7O12SiO-Mo(N)(CHtBu)(P(CH3)3)2 (4m) as a 10:1 mixture of its syn and anti rotamers with the loss of 2 equiv. of 2,2-dimethylpropane. 相似文献
Nanosized molybdenum boride and carbide were synthesized from MoO3, KBH4, and CCl4 by thermo-synthesis method at lower temperature. The relative content of Mo, Mo2C, and molybdenum boride in the product was decided by the molar ratio between MoO3, KBH4, and CCl4. Increasing the molar ratio of CCl4 to MoO3 was favorable to the production of Mo2C. Increasing the molar ratio of KBH4 to MoO3 was favorable to the production of molybdenum boride. By carefully adjusting the reaction conditions and annealing in Ar at 900°C, a single phase of MoB could be obtained. 相似文献
A chitosan resin functionalized with 3-nitro-4-amino benzoic acid moiety (CCTS-NABA resin) was newly synthesized for the collection/concentration of trace molybdenum by using cross-linked chitosan (CCTS) as base material. The carboxyl group of the moiety was chemically attached to amino group of cross-linked chitosan through amide bond formation. The adsorption behavior of molybdenum as well as other 60 elements on the resin was examined by passing the sample solutions through a mini-column packed with the resin. After the elution of the elements collected on the resin with 1 M HNO3, the eluates were analyzed by inductively coupled plasma-mass spectrometry (ICP-MS) and atomic emission spectrometry (ICP-AES).
The CCTS-NABA resin can adsorb several metal ions, such as vanadium, gallium, arsenic, selenium, silver, bismuth, thorium, tungsten, tin, tellurium, copper, and molybdenum at appropriate pHs. Among these metal ions, only molybdenum could be adsorbed almost completely on the resin at acidic regions. An excellent selectivity toward molybdenum could be obtained at pH 3–4. The adsorption capacity of CCTS-NABA resin for Mo(VI) was 380 mg g−1 resin. Through the column pretreatment, alkali and alkaline earth metals in river water and seawater samples were successfully removed.
The CCTS-NABA resin was applied to the adsorption/collection of molybdenum in river water and seawater samples. The concentrations of molybdenum in river water samples were found in the range of 0.84 and 0.95 ppb (ng g−1), whereas molybdenum in seawater was about 9 ppb. The validation of the proposed method was carried out by determining molybdenum in the certified reference materials of SLRS-4, CASS-4, and NASS-5 after passing through the CCTS-NABA resin; the results showed good agreement with the certified values. 相似文献
Ga8Ir4B – a Gallium Iridium Boride with isolated, nearly square planar Ir4B Groups in a Structure derived from the CaF2 Type The new compound Ga8Ir4B (tetragonal, I41/acd, a = 853.69(2) pm, c = 2 105.69(6) pm, Z = 8, 614 reflections, 31 parameters, R = 0.034) was prepared by reaction of the elements at 1 100°C. The structure is derived from the CaF2 type. It contains isolated Ir4B groups with boron in an unusual, nearly square planar coordination. 相似文献
Nitrogen doped carbon nanosheets supported molybdenum carbides nanoparticles (MoxC/NCS) have been synthesized by tuning the mass ratio of melamine and ammonia molybdate. The Mo2C/NCS-10 exhibits superior electrocatalytic performance and stability for HER, which was attributed to N-doped carbon nanosheets, small particle size, mesoporous structure, and large electrochemical active surface area. 相似文献
Iron interference in the spectrophotometric catalytic determination of molybdenum based on the iodide-hydrogen peroxide reaction can be corrected by using sulphosalicylic acid as masking and color-forming reagent. The catalytic influence of iron ions is circumvented to the extent of about 90% and correction of any remaining iron ions is possible by monitoring the colored iron(III)-salicylate complex at 490 nm. In this way, iron is also determined. With the proposed system, molybdenum can be determined in plant and food digests within the 0–100 μg Mo 1−1 range in the presence of up to 25 mg Fe 1−1, at a sampling rate of about 50 determinations h−1. The relative standard deviation of 10 consecutive measurements was estimated as < 2%. Results for samples were comparable with those obtained by graphite furnace atomic absorption spectrometry. In addition, recoveries within the range 94–100% were calculated. 相似文献
A series of heterodimetallic complexes of general formula (C5R5)M(μ-CO)3RuC5Me5 (M = Cr, Mo, W; R = Me, Et) has been prepared in good yields by the reaction of [C5R5M(CO)3]− with [C5Me5Ru(CH3CN)3]+. (C5Me4Et)W(μ-CO)3Ru(C5Me5) was characterized by a crystal structure determination. The W---Ru bond length of 2.41 Å is consistent with the formulation of a metal-metal triple bond, while the unsymmetrical bonding mode of the three bridging carbonyl groups reflects the inherent non-equivalence of the two different C5R5M-units. Using [CpRu(CH3CN)3]+ or [CpRu(CO)2(CH3CN)]+ as the cationic precursor leads to the formation of dimetallic species (C5R5)M(CO)5RuC5H5 with both bridging and terminal carbonyl groups. 相似文献
Molybdenum-tungsten-carbonitrides can be prepared by reacting prealloyed powders of Mo and W with carbon in the presence of nitrogen or ammonia. Single phase carbonitrides (Mo, W) (C, N) with the WC-type structure can be obtained. The nitrogen content of these carbonitrides increases with increasing molybdenum content. Flowing ammonia has a decarburizing effect, which has to be counterbalanced by an addition of a carbonaceous gas such as methane. Nitrogen instead of ammonia is equally effective and gives carbonitrides which have a nitrogen content only insignificantly lower than the carbonitrides obtained in flowing ammonia. The lattice parameters of the carbonitrides are found to be slightly smaller than the lattice parameters of the corresponding carbides. 相似文献
Nanocrystalline Mo2C powders were successfully synthesized at 500 °C by reacting molybdenum chloride (MoCl5) with C (graphite or carbon nanotube) in metallic sodium medium. X-ray powder diffractometer (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscope (XPS) and surface area analyzer (BET method) were used to characterize the samples. Experiments reveal that the carbon source used for the carbide synthesis has a great effect on the particle size and the surface area of the samples. When micro-sized graphite was used as C source the obtained nanocrystalline Mo2C powder consists of particles of 30∼100 nm, with a surface area of 2.311 m2/g. When carbon nanotubes were used as C source, the as-synthesized Mo2C sample is composed of particles of 20∼50 nm, with a surface area of 23.458 m2/g, which is an order of magnitude larger than that of the carbide prepared from the graphite. 相似文献