Light-induced metastable linkage isomers of ruthenium sulfur dioxide complexes

The irradiation of ruthenium-sulfur dioxide complexes of general formula trans-[Ru(II)(NH(3))(4)(SO(2))X]Y with laser light at low temperature results in linkage isomerization of SO(2), starting with eta(1)-planar S-bound to eta(2)-side S,O-bound SO(2). The solid-state photoreaction proceeds with retention of sample crystallinity. Following work on trans-[Ru(NH(3))(4)Cl(eta(1)-SO(2))]Cl and trans-[Ru(NH(3))(4)(H(2)O)(eta(1)-SO2)](C(6)H(5)SO(3))(2) (Kovalevsky, A. Y.; Bagley, K. A.; Coppens, P. J. Am. Chem. Soc. 2002, 124, 9241-9248), we describe photocrystallographic, IR, DSC, and theoretical studies of trans-[Ru(II)(NH(3))(4)(SO(2))X]Y complexes with (X = Cl(-), H(2)O, or CF(3)COO(-) (TFA(-))) and a number of different counterions (Y = Cl(-), C(6)H(5)SO(3)(-), Tos(-), or TFA(-)). Low temperature IR experiments indicate the frequency of the asymmetric and symmetric stretching vibrations of the Ru-coordinated SO(2) to be downshifted by about 100 and 165 cm(-1), respectively. Variation of the trans-to-SO(2) ligand and the counterion increases the MS2 decay temperature from 230 K (trans-[Ru(II)(NH(3))(4)(SO(2))Cl]Cl) to 276 K (trans-[Ru(II)(NH(3))(4)(SO(2))(H(2)O)](Tos)(2)). The stability of the MS2 state correlates with increasing sigma-donating ability of the trans ligand and the size of the counterion. Quantum chemical DFT calculations indicate the existence of a third eta(1)-O-bound (MS1) isomer, the two metastable states being 0.1-0.6 eV above the energy of the ground-state complex.     

The first photocrystallographic evidence for light-induced metastable linkage isomers of ruthenium sulfur dioxide complexes

Light-induced metastable linkage isomers of trans-[Ru(NH(3))(4)Cl(SO(2))]Cl and trans-[Ru(NH(3))(4)(H(2)O)(SO(2))](C(6)H(5)SO(3))(2) have been identified for the first time using photocrystallographic methods. In both linkage isomers the SO(2) ligand is side bound, but the Ru-O and Ru-S distances are considerably longer and almost equal in the trans-H(2)O isomer. DFT calculations confirm that both isomers correspond to minima on the ground-state potential energy surface and also predict the existence of a second oxygen-bound isomer for both compounds. The decay of the light-induced species has been studied by both DSC and IR. Activation energies for the thermal back-reaction, as derived from the temperature-dependent disappearance of light-induced IR bands, are 50.0 and 58.4 kJ/mol for the two isomers, which is larger than the corresponding numbers for photoinduced side-bound nitrosyl linkage isomers.     

Study of sulfur dioxide reduction mechanism in dimethyl sulfoxide

The electroreduction of sulfur dioxide in DMSO has been studied by normal and dp polarography, controlled-potential coulometry and cyclic voltammetry. Results suggest that the main process in the electrochemical reduction of sulfur dioxide in DMSO is a one-electron reversible reduction, followed by a reduction product dimerization according to:

$\begin{array}{l}{SO}_2+\mathit{e}?{SO}_2^{?}\\ 2{SO}_2^{?}\underset{K_f}{\overset{K_d}{?}}{S}_2{O}_4^{2?}\end{array}$

The behavior of the electrochemical parameters as function of depolarizer concentration and potential scan rate is consistent with the mechanism mentioned. In this case there is a transition between a pure kinetic control and a fast equilibrated dimerization.Moreover, the main process of SO₂ discharge is complicated by secondary reactions. Therefore, polarographic measurements have been also carried out with Na₂S₂O₄ solutions in DMSO. Furthermore, the influence that the nature and concentration of the supporting electrolyte exert on SO₂ reduction in DMSO has been studied.     

1,2-Diaryl(3-pyridyl)ethanone oximes. Intermolecular hydrogen bonding networks revealed by X-ray diffraction

The synthesis of a set of 1-aryl-2-aryl(3-pyridyl)ethanones 1-5 and the corresponding ketoximes 6-9 is reported. Structural studies of oximes 6, 7 and 9 were performed in solution using (1)H-NMR and in the solid state by X-ray crystallography, providing evidence of H-bonding networks. The crystal packing was controlled by homomeric intermolecular oxime...oxime H-bond interactions for 6 and cooperative oxime...N(pyridyl) and CH/pi interactions for 7 and 9.     

Phenylation of sulfur dioxide by pentaphenylbismuth

Conclusions Pentaphenylbismuth phenylates sulfur dioxide to give diphenylsulfone under mild conditions in high yield.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2598–2599, November, 1987.     

In situ formation of ruthenium catalysts for the homogeneous hydrogenation of carbon dioxide

A total of 44 different phosphines were tested, in combination with [RuCl(2)(C(6)H(6))](2) and three other Ru(II) precursors, for their ability to form active catalysts for the hydrogenation of CO(2) to formic acid. Half (22) of the ligands formed catalysts of significant activity, and only 6 resulted in very high rates of production of formic acid. These were PMe(3), PPhMe(2), dppm, dppe, and cis- and trans-Ph(2)PCH=CHPPh(2). The in situ catalysts prepared from [RuCl(2)(C(6)H(6))](2) and any of these 6 phosphine ligands were found to be at least as efficient as the isolated catalyst RuCl(O(2)CMe)(PMe(3))(4). There was no correlation between the basicity of monophosphines (PR(3)) and the activity of the catalysts formed from them. However, weakly basic diphosphines formed highly active catalysts only if their bite angles were small, while more strongly basic diphosphines had the opposite trend. In situ (31)P NMR spectroscopy showed that trans-Ru(H)(2)(dppm)(2), trans-RuCl(2)(dppm)(2), trans-RuHCl(dppm)(2), cis-Ru(H)(O(2)CH)(dppm)(2), and cis-Ru(O(2)CH)(2)(dppm)(2) are produced as the major metal-containing species in reactions of dppm with [RuCl(2)(C(6)H(6))](2) under catalytic conditions at 50 degrees C.     

Carbon dioxide reduction by mononuclear ruthenium polypyridyl complexes

New mononuclear ruthenium complexes with general formula [Ru(bid)(B)(Cl)] (bid is (1Z,3Z)-1,3-bis(pyridin-2-ylmethylene)isoindolin-2-ide; B = bidentate ligand 2,2'-bipyridine or R(2)-bpy, where R = COOEt or OMe) were synthesized and tested as precatalysts for the hydrogenative reduction of CO(2) in 2,2,2-trifluoroethanol (TFE) as solvent with added NEt(3). Significant amounts of formic acid were produced by these catalysts and a kinetic analysis based on initial rate constants was carried out. The potential mechanisms including intermediate species for these catalytic systems were investigated by means of quantum chemical calculations to gain deeper insight into the processes. The effect of electron-donating and electron-withdrawing groups on catalyst performance was studied both experimentally and theoretically.     

Study of the adsorption of sulfur dioxide on dealuminated zeolites Y by thermal desorption and powder X-ray diffraction

Sulfur dioxide is adsorbed on zeolites Y in two forms. The amount of the stable form (T_des=350–390 K) changes in proportion to the sodium content in the zeolite The stable form is localized in a large void at a distance of 1.8 å from the S_II position and causes redistribution of sodium cations. The weakly bound form (T_des=286–300 K) makes the main contribution to the adsorption of SO₂ on highly siliceous zeolites Y and is formed by adsorbate-adsorbate interaction, and it is apparently delocalized in a large void. Out-of-framework aluminum compounds that are formed during dealumination decrease the free volume of the zeolite without changing the nature of interaction of SO₂ with the zeolite.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 535–541, March, 1991.     

Thiocyanate linkage isomerism in a ruthenium polypyridyl complex

Ruthenium polypyridyl complexes have seen extensive use in solar energy applications. One of the most efficient dye-sensitized solar cells produced to date employs the dye-sensitizer N719, a ruthenium polypyridyl thiocyanate complex. Thiocyanate complexes are typically present as an inseparable mixture of N-bound and S-bound linkage isomers. Here we report the synthesis of a new complex, [Ru(terpy)(tbbpy)SCN][SbF(6)] (terpy = 2,2';6',2'-terpyridine, tbbpy = 4,4'-di-tert-butyl-2,2'-bipyridine), as a mixture of N-bound and S-bound thiocyanate linkage isomers that can be separated based on their relative solubility in ethanol. Both isomers have been characterized spectroscopically and by X-ray crystallography. At elevated temperatures the isomers equilibrate, the product being significantly enriched in the more thermodynamically stable N-bound form. Density functional theory analysis supports our experimental observation that the N-bound isomer is thermodynamically preferred, and provides insight into the isomerization mechanism.     

原位红外光谱法研究中孔炭限域钌纳米催化剂的形成机理（英文）

炭载金属纳米催化剂广泛应用于精细化学品加氢反应及燃料电池等许多领域.炭载体因具有较高的表面积、易于调控的表面化学官能团以及特有的耐酸耐碱等性质而经常用作负载型金属催化剂的载体.但是相对于氧化物载体,炭载体表面较为惰性,与金属纳米粒子的相互作用较弱,采用后引入金属前体,如沉淀-沉积法和浸渍法等方法制备的催化剂,在液相和高温反应条件下,金属纳米粒子易流失和烧结.因此制备高稳定性的炭负载金属纳米催化剂仍是多相催化剂制备领域的一个重要课题.随着新型炭材料的出现及纳米孔材料制备科学的发展,极大丰富和推动了炭载金属催化剂制备方法的发展.近年来,通过炭热还原法即在制备中孔炭的过程中引入金属前体,一步制备炭载金属催化剂已经成为炭载金属催化剂的一个新的制备方法.此法制备的催化剂通常具有金属纳米粒子分散均匀、炭和金属活性中心之间的作用力强、热稳定性好、炭载体对负载金属纳米粒子具有限域作用等诸多优点,而且在诸多催化反应中具有优异的催化性能.例如本课题组曾以RuCl_3/SBA-15为硬模板,采用原位碳热还原法制备了Ru-OMC催化剂,它在液相苯环加氢、合成氨及费托合成反应中均具有优异的催化性能及稳定性,但是对于中孔炭中均匀分散的钌纳米颗粒形成的机理尚不清楚.基于此,本文采用原位的红外光谱结合热重表征技术对sucrose-RuCl_3/SBA-15炭化过程钌物种的形成过程及机理进行了研究,探讨了蔗糖在炭化过程中对高分散钌纳米颗粒形成过程的稳定机制.研究发现,尽管经历了高达850 oC的高温炭热处理,所得Ru-OMC催化剂中钌纳米粒子仍然可以均匀分散,钌粒径在1-2 nm之间.同时,由于这种方法中钌前体预先负载在SBA-15载体表面,在炭化过程中,钌纳米粒子可以均匀地分散在模板氧化硅和形成的炭骨架之间的界面上,去除氧化硅模板后,钌纳米粒子可以更多的暴露在中孔炭的孔道内侧,因而具备更好的催化剂性能.通过对sucrose-RuCl_3/SBA-15炭化过程中原位红外光谱表征发现,Ru~(3+)在炭化过程中逐步被还原,并和具有含氧官能团的炭前体形成类金属羰基配合物Ru(CO)x.这种配合物的生成可以有效抑制钌纳米粒子在热处理过程的迁移乃至长大,因而对得到均匀分散的钌纳米粒子具有至关重要的作用.同时Ru(CO)_x周围刚性的氧化硅模板和碳骨架可以有效地防止钌纳米粒子在高温处理过程中烧结和团聚.对sucrose-RuCl_3/SBA-15炭化中间体的X射线光电子能谱表征进一步证明了Ru~(3+)在350 oC之前即可被还原,钌的3p轨道结合能发生了位移,说明钌和炭载体之间具有较强的相互作用.该结果可为炭载贵金属催化剂的调控制备及高活性纳米催化剂的形成机理研究提供一定的参考.     

Determination of sulfur dioxide in air

The determination of sulfur dioxide in air is based on a preliminary purification with a cellulose filter and 80% isopropanol and absorption of sulfur dioxide by means of two midget impingers in 0.3 N hydrogen peroxide. The formed sulfate is titrated in an aliquot with 0.005 M barium perchlorate employing Chlorophosphonazo III (CPA) as an indicator. The method is suitable for 0.3–19.0 mg of sulfur dioxide per 50 liters of air. The standard deviation of the titration is ±0.02 ml per consumption of 5.00 ml and is four times smaller than that of the Thorin method.     

In situ Ru K-edge X-ray absorption spectroscopy of a high-area ruthenium dioxide electrode in a Nafion-based supercapacitor environment

Changes in the state of charge of a high-area RuO_x electrode in an operating RuO_x|Nafion|IrO_x supercapacitor were monitored in situ by time-resolved, transmission Ru K-edge X-ray absorption spectroscopy (XAS). Linear and reversible variations in the intensity of the transmitted X-ray beam as a function of time were found by fixing the energy of the incident X-ray beam, E_i, at judiciously selected values within the Ru K-edge X-ray near edge structure (XANES), while the supercapacitor was charged and discharged at constant current. The sign of the slope of these temporal signals was found to vary, depending on the value of E_i. This behavior could be rationalized based on the spectral differences between the Ru K-edge XANES of RuO_x in the fully oxidized and fully reduced states, recorded in situ from films of the material electrodeposited on a gold substrate in the fluorescence mode.This paper is dedicated to Prof. Wolf Vielstich on the occasion of his 80th birthday for his outstanding contributions to electrochemistry     

Synthesis of 5-chloropyrazoles by chlorodediazoniation with sulfur dioxide

A facile synthesis of 5 -chloropyrazoles 4a-e from 5 -aminopyrazoles 2a-e via diazotization followed by chlorodediazoniation is described. A new application of sulfur dioxide as a catalyst was demonstrated to be the best for the chlorodediazoniation of diazonium chlorides 3a-e .     

Shielding of ionic interactions by sulfur dioxide in an ionic liquid

The effect of adding SO2 on the structure and dynamics of 1-butyl-3-methylimidazolium bromide (BMIBr) was investigated by low-frequency Raman spectroscopy and molecular dynamics (MD) simulations. The MD simulations indicate that the long-range structure of neat BMIBr is disrupted resulting in a liquid with relatively low viscosity and high conductivity, but strong correlation of ionic motion persists in the BMIBr-SO2 mixture due to ionic pairing. Raman spectra within the 5相似文献   

Selective fluoroalkylation of thiophenols by 1,2-dibromotetrafluoroethane activated by sulfur dioxide

Treatment of 1,2-dibromotetrafluoroethane with thiophenols in DMF in the presence of sulfur dioxide and pyridines having pK_a > 5 gives fluoroalkylated thioethers in high yields under mild conditions. The influence of thiophenol reactant structure and medium basicity is discussed.     

功能化MCM-41固载的钌基催化剂上二氧化碳加氢合成甲酸

采用两种方法制备了功能化MCM-41固载的钌基催化剂,并用原子吸收光谱,紫外可见光谱以及红外光谱等手段对其进行表征。结果表明,钌基在功能化MCM-41上顺利固载。将这两种固载的钌基催化剂用于二氧化碳加氢合成甲酸反应,发现在较低反应温度和较低氢分压下,固载的RuCl2(PPh3)3催化剂表现出更高的催化活性,在反应温度80℃,H2分压5MPa, CO2分压8MPa下,甲酸转化数达到1275。固载的RuCl2(PPh3)3催化剂也表现出很好的重复再用性。     

The nature of sulfur bonding in thiopyrylium cation

Comparison of the PMR spectrum ofthiopyrylium cation with those of the oxygen (pyrylium cation) and nitrogen (pyridinium cation) analogs has suggested the unique electronic structure of the thiopyrylium cation. To investigate this structure the extended Hückel MO calculations have been carried out using two basis sets, one with and another without sulfur 3d orbitals. The electronic structure of thiopyrylium cation can be rationalized by the 3d orbital involvement of the S atom in the basis set. The primary effect of the involvement of 3d orbitals on the S atom is shown to be the electron transfer from the ring carbon fragment, in particular from the β ring carbons, to the S atom, with an accompanying increase in sulfur-α-carbon bond order.     

Anti-Markovnikov hydroarylation of styrenes catalyzed by an in situ generated ruthenium complex

An efficient and practical catalytic system for the anti-Markovnikov ruthenium-catalyzed hydroarylation of styrenes with acetophenone, allowing a straightforward access to bibenzyl backbones, is described for the first time: this process, involving regioselective C-H bond activation, is complementary to a Friedel-Crafts type reaction giving the branched adduct.