A new synthetic method for MS42− (M Mo, W). Evidence for catalysis of aqueous MO42−/MS42− interconversion by thiols
摘要:
The reaction of aqueous molybdate with sulfide leading to [MoO4-xSx]2- (x = 1-4, hereafter referred to as S1-S4) in basic solution is greatly accelerated by thiols, as are the reverse hydrolyses. In aqueous solution buffered at pH 9, a 50-fold molar excess of 2-mercaptoethanol over molybdenum increased the rate of formation of S1 from molybdate and sulfide by at least a factor of 10(4) and also substantially increased the rates of S2 --> S3 --> S4 conversion. Dithiols behaved similarly to 2-mercaptoethanol in accelerating the formation of S1-S4 from molybdate and sulfide. The same molar excess of 2-mercaptoethanol over molybdenum was found to increase the rates of hydrolyses of S2 and S3 by almost-equal-to 10(2) and almost-equal-to 10(1), respectively, at pH 9. Thus, in basic aqueous solution, thiols appear to function as catalysts of oxo/sulfido ligand substitution on [MoO4-xSx]2-. Similar accelerating effects of thiol were observed on reactions of aqueous tungstate with sulfide. Based on these results a new method for the preparation of (NH4)2[MS4] (M = Mo, W) was developed; this method combines aqueous MO4(2-) and lithium sulfide in the presence of 2-mercaptoethanol in NH3/NH4+ buffer at pH 9.6. These results may be relevant to the biological chemistry of molybdate and tungstate.
A Crystallographic and Mo K‐Edge XAS Study of Molybdenum Oxo Bis‐, Mono‐, and Non‐Dithiolene Complexes – First‐Sphere Coordination Geometry and Noninnocence of Ligands
作者:Prinson P. Samuel、Sebastian Horn、Alexander Döring、Kajsa G. V. Havelius、Stefan Reschke、Silke Leimkühler、Michael Haumann、Carola Schulzke
DOI:10.1002/ejic.201100331
日期:2011.10
spectra were observed for complexes with dithiolene-derived ligands. The results emphasize that the noninnocent character of the dithiolene ligand influences the electronic structure of the modelcompounds, but does not significantly affect their metal coordination geometry, which is largely determined by the Mo(IV) or (V) ion itself. The latter conclusion also holds for the molybdenum site geometries in
制备了十个具有不同硫供体配体(即各种二硫烯和硫化物)的方形锥体钼配合物,它们模拟了钼依赖性氧化还原酶的钼辅因子的配位基序。模型化合物通过 Mo K-edge X 射线吸收光谱 (XAS) 进行研究,并且(有一个例外)通过 X 射线衍射分析它们的分子结构,以获得关于钼的第一配位壳的键长和几何形状的详细信息. 对于所有配合物,包括那些含有 Mo(CO) 2 或 Mo(μ-S) 2 Mo 基序的配合物,仅观察到 Mo=O 和 Mo-S 键长及其各自配位角的微小变化。XAS 分析(边缘能量)显示,与二硫烯配合物相比,具有无害硫基配体的化合物中钼离子的相对氧化水平更高,众所周知,二硫烯配合物表现出无害,即从配体向金属提供大量电子密度。此外,对于与二硫烯衍生的配体的配合物,观察到更长的平均 Mo-S 和 Mo=O 键,因此在红外光谱中观察到较低的 ν(Mo=O) 伸缩频率。结果强调,二硫烯配体的无害特
Synthesis and reactivity of iridium complexes with pyridine and piperidine ligands: models for hydrodenitrogenation
作者:Merlín Rosales、Teresa González、Reinaldo Atencio、Roberto A. Sánchez-Delgado
DOI:10.1039/b406949h
日期:——
Ir(H)2Cl(eta1-N-L)(PPh3)2 (L = py, 4; iQ, 5) and IrH(Cl)2(eta1-N-L)(PPh3)2 (L = py, 6; iQ, 7). Reaction of 3 with py or iQ yielded complexes 1 and 2, respectively, while under a slow stream of carbon monoxide the complex [Ir(H)2(eta1-N-pip)(CO)(PPh3)2]PF6 (8) was produced. Complex 3 also reacts with halide and 4-bromothiophenolate anions leading to the corresponding neutral species Ir(H)2(X)(eta1-N-pip)(PPh3)2, X
Mechanistic Studies on the Reactions of PhS<sup>-</sup> or [MoS<sub>4</sub>]<sup>2</sup><sup>-</sup> with [M<sub>4</sub>(SPh)<sub>10</sub>]<sup>2</sup><sup>-</sup> (M = Fe or Co)
作者:Zhen Cui、Richard A Henderson
DOI:10.1021/ic020284j
日期:2002.8.1
Kinetic studies, using stopped-flow spectrophotometry, on the reactions of [M(4)(SPh)(10)](2)(-) (M = Fe or Co) with PhS(-) to form [M(SPh)(4)](2)(-) are described, as are the reactions between [M(4)(SPh)(10)](2)(-) and [MoS(4)](2)(-) to form [S(2)MoS(2)Fe(SPh)(2)](2)(-) or [S(2)MoS(2)CoS(2)MoS(2)](2)(-). The kinetics of the reactions with PhS(-) are consistent with an initial associative substitution
phosphate buffered aqueous solutions with NO. Three consecutive reactions are observed. The two first ones obey pseudo first order rate laws with observed rates proportional to [NO]. The third reaction obeys a first order rate law. Nitrite is one of the final products. The mechanism proposed involves thiol nitrosation via a radical mechanism followed by hydrolysis of the S–N bond. The findings indicate
摘要 MoS 4 2− (TTM) 在脱气的中性磷酸盐缓冲水溶液中与 NO 反应。观察到三个连续反应。前两个遵循伪一阶速率定律,观察速率与 [NO] 成正比。第三个反应服从一阶速率定律。亚硝酸盐是最终产品之一。所提出的机制涉及通过自由基机制进行硫醇亚硝化,然后是 S-N 键的水解。研究结果表明,如果将 MoS 4 2- 用作药物,它不会显着影响系统中的 NO 浓度。
Kinetics of the formation and hydrolysis reactions of some thiomolybdate(VI) anions in aqueous solution
作者:Nicholas J. Clarke、Stuart H. Laurie、Mike J. Blandamer、John Burgess、Andrew Hakin
DOI:10.1016/s0020-1693(00)85933-2
日期:1987.6
The kinetics of the formation of the thiomolybdate ions MoOS32− and MoS42− were determined spectroscopically from the addition of excess sulphide to MoO2S22− in pH buffered media (6–8) at 30 °C. The reverse (hydrolysis) reactions of MoO2S22− and MoOS32− were measured under the same conditions. The reaction rates measured are shown below: Values of the rate-constants (s−1) obtained at pH 7.0 were k10