Combined ruthenium(II) and lipase catalysis for efficient dynamic kinetic resolution of secondary alcohols. Insight into the racemization mechanism

Pentaphenylcyclopentadienyl ruthenium complexes (3) are excellent catalysts for the racemization of secondary alcohols at ambient temperature. The combination of this process with enzymatic resolution of the alcohols results in a highly efficient synthesis of enantiomerically pure acetates at room temperature with short reaction times for most substrates. This new reaction was applied to a wide range of functionalized alcohols including heteroaromatic alcohols, and for many of the latter, enantiopure acetates were efficiently prepared for the first time via dynamic kinetic resolution (DKR). Different substituted cyclopentadienyl ruthenium complexes were prepared and studied as catalysts for racemization of alcohols. Pentaaryl-substituted cyclopentadienyl complexes were found to be highly efficient catalysts for the racemization. Substitution of one of the aryl groups by an alkyl group considerably slows down the racemization process. A study of the racemization of (S)-1-phenylethanol catalyzed by ruthenium hydride eta(5)-Ph(5)CpRu(CO)(2)H (8) indicates that the racemization takes place within the coordination sphere of the ruthenium catalyst. This conclusion was supported by the lack of ketone exchange in the racemization of (S)-1-phenylethanol performed in the presence of p-tolyl methyl ketone (1 equiv), which gave <1% of 1-(p-tolyl)ethanol. The structures of ruthenium chloride and iodide complexes 3a and 3c and of ruthenium hydride complex 8 were confirmed by X-ray analysis.     

Ruthenium(II) complex catalysts bearing a pyridyl-supported pyrazolyl-imine ligand for transfer hydrogenation of ketones

A new class of hemilabile unsymmetrical 2-(1-arylimino)-6-(pyzazol-1-yl)pyridine ligands and their ruthenium(II) and nickel(II) NNN complexes were synthesized. The Ru(II) complex catalysts have been fully characterized and exhibited good to excellent catalytic activity in the transfer hydrogenation (TH) of ketones in refluxing 2-propanol. These results have demonstrated rare examples of active ruthenium(II) NNN complex catalysts that do not feature a N-H functionality for TH of ketones.     

Soluble polymer-supported ruthenium porphyrin catalysts for epoxidation,cyclopropanation, and aziridination of alkenes

[reaction: see text] Attachment of poly(ethylene glycol) (PEG) to ruthenium porphyrin via a covalent etheric bond gives soluble polymer-supported ruthenium catalysts 3-5. These catalysts exhibit high reactivity and selectivity toward alkene epoxidation with 2,6-dichloropyridine N-oxide and alkene cyclopropanation with diazo compounds. The application of these catalysts in the synthesis of unstable organic compounds has been demonstrated.     

Determination of platinum and ruthenium in Pt and Pt-Ru catalysts with carbon support by direct and derivative spectrophotometry

Platinum and ruthenium in carbon supported Pt and Pt-Ru catalysts were determined by direct and derivative spectrophotometric methods. Complexes of platinum and ruthenium with SnCl(3)(-) ligands (tin(II) chloride in HCl) were used to determine both metals in solutions obtained after digestion of the samples of the catalysts. Platinum in the Pt/C catalyst can be determined in solutions obtained by digestion of the samples in aqua regia. Derivative spectrophotometry was used to determine both metals in the presence of each other in solutions obtained after digestion of samples of the Pt-Ru/C catalyst in the mixture of HCl+HNO(3) (6:1). The first derivative at 377 nm (;zero-crossing' point of ruthenium) and the second-derivative values at 495 nm (;zero-crossing' point of platinum) were used to estimate the concentration of platinum and ruthenium, respectively.     

吡啶基桥联双四唑钌(Ⅱ)配合物催化酮的转移氢化反应（英文）

含氮配体具有稳定性好、易于合成等优点,而且其过渡金属配合物表现出较高的催化活性,因而在配位化学和均相催化等研究领域受到了广泛关注.基于吡啶骨架的三齿NNN配体具有良好的配位能力和丰富的配位模式,如吡啶桥联的对称配体2,2':6',2'-三吡啶、2,6-双噁唑啉基吡啶、2,6-双亚胺基吡啶和2,6-双吡唑基吡啶等在有机合成及配合物催化剂制备等方面得到广泛应用.2,6-双四唑基吡啶也是基于吡啶的多齿配体,已被用于合成发光材料或高效回收次锕系元素等,但是其在催化领域的应用较少.过渡金属催化的不饱和化合物的转移氢化反应具有反应条件温和、不直接使用氢气等优点,因而受到越来越多的关注.一系列优异的配体及配合物在转移氢化反应中脱颖而出,如对甲苯磺酰手性二胺配体、2-甲胺基吡啶钌配合物、配体中含有NH官能团的过渡金属配合物等.我们也报道了几种吡啶基桥联的含氮配体及其钌配合物,并应用于催化酮的转移氢化反应.在此基础上,本文合成了三种连有不同膦配体的2,6-双四唑基吡啶钌配合物,并用于催化酮的转移氢化反应.从N~2,N~6-二对甲苯基-2,6-吡啶二甲酰胺(1)出发,经氯代/环化两步反应合成4-氯吡啶基桥联双四唑化合物(2),配体2与RuCl_2(PPh_3)_3在对应的反应条件下制得三种连有不同膦配体的2,6-双四唑基吡啶钌配合物(3),其分子结构通过核磁共振波谱和X射线单晶晶体结构测定得到确认.将这三种钌配合物应用于催化酮的转移氢化反应,当催化剂用量为0.5 mol%时,在异丙醇回流条件下,比较连有不同膦配体的2,6-双四唑基吡啶钌配合物的催化活性.膦配体为1,4-双(二苯基膦)丁烷的钌配合物3b表现出更高的催化活性,含有双三苯基膦的钌配合物3a则表现出与3b相当或略低的催化活性,含有1,5-双(二苯基膦)戊烷的钌配合物3c活性最差.以3b为催化剂拓展了一系列酮底物,取代的芳香酮、链状和环状的脂肪酮都可以高效地被还原,大部分酮底物以95%的转化率还原成相应的醇.含有氯取代基的苯乙酮对反应有较大的加速作用,反应时间更短,转化率更高.由于羰基环的张力,1-四氢萘酮与9-芴酮转化率略低.结合实验结果与相关文献,提出了一条基于Ru-H活性中间体的内层反应机理:钌配合物在iPrOK作用下生成Ru(Ⅱ)-烷氧基中间体Ⅰ,随后发生β-H消除反应脱去一分子丙酮得到Ru-H配合物,Ru-H配合物与酮底物作用经过渡态Ⅱ生成另一分子Ru(Ⅱ)-烷氧基中间体Ⅲ,随后异丙醇与烷氧基发生交换生成目标产物,同时生成中间体Ⅰ完成催化循环.     

第二代氨合成催化体系——钌系氨合成催化剂及其工业应用*

本文综述了第二代氨合成催化体系——钌系氨合成催化剂的研制、开发及工业应用情况。介绍了钌系氨合成催化剂的载体、促进剂、钌活性前身物对氨合成催化活性的影响。比较了钌系氨合成催化剂与铁系氨合成催化剂的反应机理与性能特点。新型氨合成催化工艺流程的成功开发为钌系氨合成催化剂的工业应用提供了有力的保障。     

Strong-metal-support-interaction in titania-supported rhodium, ruthenium, and rhodium-ruthenium bimetallic catalysts

Titania-supported rhodium, ruthenium and rhodium-ruthenium catalysts were prepared by impregnation followed by reduction at 573 K (low temperature reduced-LTR) and 773 K (high temperature reduced — HTR). Temperature programmed desorption of hydrogen showed the existence of strong-metal-support-interaction (SMSI) in rhodium and ruthenium catalysts, but not in the bimetallic catalyst. In either case, metal-hydrogen bond strength had undergone change in going from an LTR to HTR sample. X-ray photoelectron spectroscopy (XPS) results did not show any electron transfer between metal and support in any of the catalysts but electron transfer from rhodium to ruthenium was indicated in the bimetallic catalyst under HTR.     

Cover Picture

The cover picture shows an arrangement of ruthenium atoms representing the active site of ruthenium catalysts for ammonia synthesis. This B(5)-type active site consists of three ruthenium atoms in one layer (blue spheres) and two ruthenium atoms in the layer directly above this (red spheres). This arrangement is energetically preferred, because none of the ruthenium atoms is in contact with both of the nitrogen atoms (green spheres) of the adsorbed N(2) molecule. Based on knowledge of this active site a number of catalysts were prepared by using [Ru(3)(CO)(12)] (upper green sphere) as a precursor. These catalysts were characterized (left red sphere and TEM micrograph in the background), tested using a parallel screening procedure (left and lower blue spheres), and kinetically analyzed (right blue sphere). The resulting barium-promoted Ru/MgO catalyst is the most active catalyst for ammonia synthesis to be described (right red sphere). It can be concluded that the B(5)-type site also dominates the activity of the promoted catalysts (lower green sphere). The enormous catalytic potential of Ba-Ru/MgO is described by Muhler et al. on pp. 1061 ff.     

Formation of Ru–M/Sibunit Catalysts for Ammonia Synthesis

The effects of the nature of ruthenium and alkaline promoter precursor compounds and support properties on the activity of Ru–(Cs, K)/Sibunit catalysts in the reaction of ammonia synthesis were studied. The formation of active centers in the catalysts was studied with the use of EXAFS, XPS, and electron micro-scopy. It was found that ruthenium and a portion of cesium occurred in metallic states in the reduced catalysts. The most active catalysts containing 4 wt % ruthenium at the atomic ratios [K] : [Ru] = 4.5 and [Cs] : [Ru] = 2.5 were obtained with the use of the [Ru(dipy)₃](OH)₂ complex.     

New latent metathesis catalysts equipped with exchangeable boronic ester groups on the NHC

Abstract

Latent metathesis catalysts equipped with boronate esters of diols as exchangeable end-groups on their NHC ligands and an S-chelated ruthenium-benzylidene core were synthesized. The stable S-chelated ruthenium complexes underwent hydrolysis under mild acidic conditions, allowing easy exchange of terminal units by several 1,2- and 1,3-diols, without degrading the central ruthenium benzylidene. Using this strategy, we also prepared metathesis catalysts equipped with diallyl substrates at the termini that showed concentration dependency on RCM reactions. Notably, the larger dendritic catalysts were more efficient at the more dilute condition.     

纳米材料负载钌催化剂的制备与应用

钌基催化剂在温和条件下具有优异的催化性能,因而广泛应用于各种反应中.主要综述了纳米材料负载钌催化剂的制备方法和应用研究的最新进展,总结了载体材料、前驱体和纳米钌粒子对催化剂性能的影响,系统地介绍负载型钌催化剂最新制备方法和传统制备方法的新发展,并简单探讨了各种方法的优缺点,较全面地概述了负载型钌催化剂的应用领域及其性能,展望了其发展前景.     

Structure and kinetic characterization of unsupported, ruthenium based catalysts

Ruthenium(III) chloride and ruthenium(IV) oxide have been reduced to unsupported ruthenium catalyst powders. The texture and properties of the catalysts were studied by SEM, XRD and BET techniques. The activity of the catalysts was tested in the liquid phase hydrogenation of benzene to cyclohexene and cyclohexane.Dept. of Organic TechnologyDept. of Solid State ChemistryDept. of Glass and Ceramics     

The analysis of ruthenium catalysts by photon-induced X-ray fluorescence using a microcomputer for data acquisition and analysis

An improved method for the determination of ruthenium in catalytic materials based on a relative fluorescence ratio factor is presented. This method employs a thin-film technique and an internal standard technique to minimize absorption and enchancement effects. The samples and standards were fluorescent with a¹⁰⁹Cd (7 mCi) annular source for 200 seconds and the data were collected and analyzed with an Apple II+ micro computer. Precision (total variation) for typical ruthenium catalysts in the range of 1–5% ruthenium was about 2%. Finally, the concentration of ruthenium in six commercial catalysts was determined for both alumina and carbon supports.Parts of this work have been funded by an international program between CONICIT (Venezuela) and NSF (United States of America).     

Photocatalytic CO2 Reduction under Visible-Light Irradiation by Ruthenium CNC Pincer Complexes

Photocatalytic CO₂ reduction using a ruthenium photosensitizer, a sacrificial reagent 1,3-dimethyl-2-(o-hydroxyphenyl)-2,3-dihydro-1H-benzo[d]imidazole (BI(OH)H), and a ruthenium catalyst were carried out. The catalysts contain a pincer ligand, 2,6-bis(alkylimidazol-2-ylidene)pyridine (CNC) and a bipyridine (bpy). The photocatalytic reaction system resulted in HCOOH as a main product (selectivity 70–80 %), with a small amount of CO, and H₂. Comparative experiments (a coordinated ligand (NCMe vs. CO) and substituents (tBu vs. Me) of the CNC ligand in the catalyst) were performed. The turnover number (TON_HCOOH) of carbonyl-ligated catalysts are higher than those of acetonitrile-ligated catalysts, and the carbonyl catalyst with the smaller substituents (Me) reached TON_HCOOH=5634 (24 h), which is the best performance among the experiments.     

氧化铝载体和氧化钡助剂对钌基氨合成催化剂结构和性能的影响

采用不同来源γ-Al2O3(市售Al2O3-1,合成Al2O3-2)作为钌基氨合成催化剂载体,利用浸渍法制备了一系列添加不同BaO助剂含量的Ba-Ru/Al2O3催化剂.通过X射线衍射(XRD)、N2-低温物理吸附、X射线荧光光谱(XRF)、透射电镜(TEM)、H2程序升温还原(H2-TPR)、NH3程序升温脱附(NH3-TPD)和X射线光电子能谱(XPS)等方法研究了不同来源的Al2O3以及BaO助剂含量对负载型钌基催化剂的物相结构、织构性质、微观形貌、表面性质和催化剂的氨合成活性等方面的影响.结果表明,载体的物理化学性质对制备的钌基氨合成催化剂的结构以及活性有较大影响.BaO助剂对催化剂的影响主要表现在两个方面:添加量不同导致BaO与γ-Al2O3的作用力不同,从而进一步影响催化体系的比表面积和孔结构性质;BaO助剂会对体系的Ru物种还原性质以及催化剂表面酸碱性质进行调节,适量BaO的加入能够极大提高反应活性,而这种最佳量与载体性质密切相关.     

Rhodium versus ruthenium: contrasting behaviour in the asymmetric transfer hydrogenation of α-substituted acetophenones

The reduction of a number of α-substituted acetophenones has been achieved using both ruthenium(II)- and rhodium(III)-based asymmetric transfer hydrogenation catalysts employing formic acid as the hydrogen donor.     

Development of a method for the preparation of ruthenium indenylidene-ether olefin metathesis catalysts

The reactions between several derivatives of 1-(3,5-dimethoxyphenyl)-prop-2-yn-1-ol and different ruthenium starting materials [i.e., RuCl?(PPh?)? and RuCl?(p-cymene)(L), where L is tricyclohexylphosphine di-t-butylmethylphosphine, dicyclohexylphenylphosphine, triisobutylphosphine, triisopropylphosphine, or tri-n-propylphosphine] are described. Several of these reactions allow for the easy, in-situ and atom-economic preparation of olefin metathesis catalysts. Organic precursor 1-(3,5-dimethoxyphenyl)-1-phenyl-prop-2-yn-1-ol led to the formation of active ruthenium indenylidene-ether complexes, while 1-(3,5-dimethoxyphenyl)-prop-2-yn-1-ol and 1-(3,5-dimethoxyphenyl)-1-methyl-prop-2-yn-1-ol did not. It was also found that a bulky and strong σ-donor phosphine ligand was required to impart good catalytic activity to the new ruthenium complexes.     

Synthesis,characterization, and reactivity of ruthenium(II) complexes containing η6-arene-η1-pyrazole ligands

New ruthenium(II) complexes containing η⁶-arene-η¹-pyrazole ligands were synthesized and characterized by elemental analysis and spectroscopic methods. In addition, the molecular structure of dichloro-3,5-dimethyl-1-(pentamethylbenzyl)-pyrazole–ruthenium(II), [Ru]L_3b, was determined by X-ray diffraction studies. These complexes were applied in the transfer hydrogenation of acetophenone by isopropanol in the presence of potassium hydroxide. The activities of the catalysts were monitored by NMR.     

孔雀石绿-KIO4催化动力学光度法测定痕量钌

在H2SO4介质中及80 ℃的条件下, 钌对KIO4氧化孔雀石绿的褪色反应有明显催化作用, 探讨了反应的最佳条件, 据此建立了催化动力学光度法测定钌的新方法. 非催化反应吸光度A0与催化反应吸光度A之间的差值ΔA与Ru(Ⅲ)质量浓度在0.1～1.5 μg/25 mL范围内具有良好的线性关系, 检出限为4.31×10-10 g/mL. 测定了动力学参数, 反应为准一级反应, 表观速率常数为3.52×10-4 s, 表观活化能为46.97 kJ/mol. 该方法用于分子筛样品及活性炭样品中痕量钌的测定, 其回率在98.6%～104.8%之间, 符合痕量分析的要求.     

Effect of Activated Carbon as a Support on Metal Dispersion and Activity of Ruthenium Catalyst for Ammonia Synthesis

IntroductionSince the beginning of the 2 0 th century,ammonia has been produced over the fused ironcatalyst known as Haber- Bosch process.Thecatalyst most widely used is Fe,promoted withK2 O and Al2 O3and other un- reducible oxides.Thefused iron catalyst has many advantages,such aslow unit price and long lifetime,worldwide about1 40 million tons of ammonia is manufactured peryear in the presence of Fe catalyst.But its lowactivity below40 0℃ makes it necessary to carryout the process at a …