Sulfided heterogeneous,bimetallic Ru/Mo catalysts derived from mixtures of Ru3(CO)12 (or RuCl3) and a molybdenum heteropolyanion: The reactions of ethanol with tetrahydroquinoline

Efforts have been made to develop Ru/Mo bimetallic catalyst systems for hydrodenitrogenation (HDN) of tetrahydroquinoline (THQ). In the course of these studies, it was discovered that in ethanol, under hydrogen and in the presence of carbon disulfide (CS₂), precatalyst solutions containing ruthenium [as Ru₃(CO)₁₂ or RuCl₃] and molybdenum [as the H₃PMo₁₂O₄₀ heteropolyanion (HPA)] decompose to form bimetallic, sulfided particles. Particle diameters run from 0.1 to 5μm depending on the rate of stirring. Catalyst particles with sizes ranging from 0.1 to 1μm can be prepared reproducibly. BET-measured surface areas for these size particles ranged from 2 to 20m² g^?1. These sulfided particles were found to catalyze, at temperatures of 200–250°C and hydrogen pressures of 200–1000 psig (1.4–6.9 MPa) hydrogen, the N-ethylation of THQ to form N-ethyltetrahydroquinoline (N-Et-THQ), rather than the formation of propylcyclohexane or propylbenzene, reaction products expected for HDN of THQ. Monometallic heterogeneous catalysts prepared from the individual precatalyst complexes, under identical conditions, show minimal activity for N-ethylation by comparison with the bimetallic catalyst. In the absence of hydrogen, the reaction proceeds so that THQ is converted to quinoline, N-Et-THQ, N-C₄H₉-THQ and N-C₆H₁₃-THQ. The latter products appear to arise via acetaldehyde, formed as an intermediate by dehydrogenation of ethanol. Acetaldehyde either condenses with THQ to form N-Et-THQ, or self-condenses (aldol condensation) prior to reaction with THQ, thereby giving higher-homolog alkylation products.     

Single-Crystal Neutron Structure Analysis of (NH4)21[H3Mo57V6(NO)6O183(H2O)18]·53 H2O

The crystal structure of (NH₄)₂₁[H₃Mo₅₇V₆(NO)₆O₁₈₃ (H₂O)₁₈]·53 H₂O a supramolecular heteropoly cluster compound (space group P6₃/mmcZ=2 final R1=0.1302 (I>2σ(I)) for 1745 unique reflections) was redetermined by single-crystal neutron diffraction studies at 20 K. The X-ray diffraction results reported in 1994 by Müller et al. (Z. Anorg. Allg. Chem. 620 599) are confirmed. Additionally we could localize many hydrogen positions not found so far and establish a phase transition near 240 K. Many of the ammonium ions the ligand and hydrate H₂O molecules and the hydroxy group are orientationally disordered even at 20 K. The central cavity of the structure is built up by two twelve-membered rings consisting of six O-H·sdot;·O hydrogen bonds each. These strong hydrogen bonds are obviously decisive for the stability of the cluster. The hydrate H₂O molecules are stronger-hydrogen-bond acceptor groups than the oxoligands of the cluster.     

α-和β-K7[SiW9O37Fe3(H2O)3]·xH2O的合成及其在有机溶剂中的反应

本文报道了从三缺位杂多阴离子α-和β-SiW₉O₃₄^10-合成α-和β-[SiW₉O₃₇Fe₃(H₂O)₃]^7-的钾盐的方法。FAB-负离子质谱表明,阴离子在溶液中主要是以单体形式存在,二聚体微量。阴离子中的配位水分子在甲苯中可被SCN等配体取代生成具有特征颜色的配离子。标题化合物具有催化PhIO(亚碘酰苯)环氧化反式-二苯乙烯、苯乙烯、环乙烯生成相应环氧化物的性质。     

A New Application for Heteropolyanions: Etching of III-V Semiconductor Compounds

This paper deals with the behaviour of two Keggin-type heteropolyanions: SiMo₁₂O^4– ₄₀ and SiW₁₂O^4– ₄₀ dissolved in aqueous acidic solution, towards semiconductors, at rest potential. Two III-V semiconductors are studied, GaAs and InP. At the material/solution interface, GaAs undergoes an oxidation/dissolution process while the heteropolyanions are reduced. These reactions lead to the growth of a film on the GaAs surface, its composition was determined by X-ray photoelectron spectroscopy. In the dark, at the InP/solution interface no reaction occurs whatever the heteropolyanion used. However, in the presence of SiMo₁₂O^4– ₄₀, when an n-type InP semiconductor is illuminated (h>1.35 eV) the heteropolyanions are reduced and the photodissolution of the material is achieved, no surface film is present on the etched surface. The difference of behaviour between GaAs and InP is primarily due to the difference of the positions of the semiconductor energy-band edges with respect to the first redox potential of the heteropolyanions.     

杂多阴离子柱撑水滑石层柱相互作用(Ⅰ)

杂多阴离子柱撑水滑石层柱相互作用（Ⅰ）李兴林＊佘益民郭军蒋大振（中国科学院长春应用化学研究所长春１３００２２）（吉林大学化学系长春）关键词杂多阴离子，柱撑水滑石，ＸＰＳ，ＩＲ，ＸＲＤ１９９６－０６－１８收稿，１９９６－１０－１２修回国家自然科学基金资...     

钨硅系列三元杂多阴离子柱撑阴离子粘土的合成及表征

采用离子交换法将过渡金属离子三元取代钨硅杂多阴离子引入Zn₂Al型阴离子粘土层内，得到柱撑水滑石Zn₂Al(OH)₆-SiW₉Z₃O₄₀(Z=Ti⁴⁺, Mo⁶⁺)及Zn₂Al(OH)₆-SiW₉Fe₃(H₂O)₃     

Electrocatalytic Reduction of Nitrite by Phosphotungstic Heteropolyanion. Application for Its Simple and Selective Determination

Three couples of reversible redox peaks of the PW₁₂O₄₀^3? (PW₁₂) anion, which are composed of two one‐electron and one two‐electron processes occur in the potential range from +0.25 to ?0.7 V in aqueous solutions. The electrocatalytic reduction of nitrite has been studied by the first redox couple of the PW₁₂ anion at the surface of a carbon paste electrode. Cyclic voltammetric and chronoamperometric techniques were used to investigate the suitability of PW₁₂ anion as a mediator for nitrite electrocatalytic reduction in aqueous solution with strongly acidic concentration of H₂SO₄. Results showed that H₂SO₄ 1.00 M is the best medium for this purpose. In the optimum concentration of H₂SO₄, the electrocatalytic ability about 500 mV can be seen and the homogeneous second‐order rate constant (k_s) for nitrite coupled catalytically to PW₁₂ anion was calculated as 2.52×10³ M^?1 s^?1 using the Nicholson–Shain method. According to our voltammetric experiments, the catalytic reduction peak current was linearly dependent on the nitrite concentration and the linearity range obtained was 3×10^?5 to 1.00×10^?3 M. The detection limit has been found to be 2.82×10^?5 M (2σ). This method has been applied as a selective, simple, and precise method for determination of nitrite in real samples.     

一缺位杂多阴离子XW_(11)O_(39)~((12-n)-)(X=P~(5+),Si~(4+),B~(3+),Ga~(3+))含硫有机膦衍生物的合成及结构表征

杂多化合物的衍生物由于具有潜在的多功能催化性能 ,长期以来一直受到人们的关注 [1～ 3 ] .将有机或有机金属基团引入杂多化合物中以修饰杂多阴离子的部分外部骨架结构 ,对研究杂多化合物的性质和应用及新型催化剂的开发具有重要意义[4,5 ] .在杂多化合物表面引入适当的有机基团还可改善其溶解性能及其它物理性质 ,从而拓宽其应用范围 .研究结果表明 ,这类化合物还具有很好的抗病毒和抗肿瘤活性 [6,7] .Klemperer等 [8] 合成的 [( η5 - C5 H5 ) Ti PW11O3 9] 4 -将多酸与金属有机化合物有机地融为一体 ,从而开辟了多酸金属有机化学的新…