温控离子液体/有机两相体系中纳米Rh催化烯烃氢甲酰化反应

将具有"高温混溶、室温分相"功能的离子液体[CH3(OCH2CH2)16N+Et3][CH3SO3–](ILPEG750)与甲苯-正庚烷组成的两相体系用于纳米Rh催化的烯烃氢甲酰化反应中,在优化的反应条件下,1-辛烯转化率和醛收率分别为99%和91%.催化剂经简单分相即可与产物分离,且可连续使用8次,其活性基本保持不变.     

Hydroformylation of Olefins by a Rhodium Single‐Atom Catalyst with Activity Comparable to RhCl(PPh3)3

Homogeneous catalysts generally possess superior catalytic performance compared to heterogeneous catalysts. However, the issue of catalyst separation and recycling severely limits their use in practical applications. Single‐atom catalysts have the advantages of both homogeneous catalysts, such as “isolated sites”, and heterogeneous catalysts, such as stability and reusability, and thus would be a promising alternative to traditional homogeneous catalysts. In the hydroformylation of olefins, single‐atom Rh catalysts supported on ZnO nanowires demonstrate similar efficiency (TON≈40000) compared to that of homogeneous Wilkinson's catalyst (TON≈19000). HAADF‐STEM and infrared CO chemisorption experiments identified isolated Rh atoms on the support. XPS and XANES spectra indicate that the electronic state of Rh is almost metallic. The catalysts are about one or two orders of magnitude more active than most reported heterogeneous catalysts and can be reused four times without an obvious decline in activity.     

An Operando FTIR Spectroscopic and Kinetic Study of Carbon Monoxide Pressure Influence on Rhodium‐Catalyzed Olefin Hydroformylation

The influence of carbon monoxide concentration on the kinetics of the hydroformylation of 3,3‐dimethyl‐1‐butene with a phosphite‐modified rhodium catalyst has been studied for the pressure range p(CO)=0.20–3.83 MPa. Highly resolved time‐dependent concentration profiles of the organometallic intermediates were derived from IR spectroscopic data collected in situ for the entire olefin‐conversion range. The dynamics of the catalyst and organic components are described by enzyme‐type kinetics with competitive and uncompetitive inhibition reactions involving carbon monoxide taken into account. Saturation of the alkyl–rhodium intermediates with carbon monoxide as a cosubstrate occurs between 1.5 and 2 MPa of carbon monoxide pressure, which brings about a convergence of aldehyde regioselectivity. Hydrogenolysis of the acyl intermediate is fast at 30 °C and low pressure of p(CO)=0.2 MPa, but is of minus first order with respect to the solution concentration of carbon monoxide. Resting 18‐electron hydrido and acyl complexes that correspond to early and late rate‐determining states, respectively, coexist as long as the conversion of the substrate is not complete.     

Spiroketal‐Based Phosphorus Ligands for Highly Regioselective Hydroformylation of Terminal and Internal Olefins

A new class of bidentate phosphoramidite ligands, based on a spiroketal backbone, has been developed for the rhodium‐catalyzed hydroformylation reactions. A range of short‐ and long‐chain olefins, were found amenable to the protocol, affording high catalytic activity and excellent regioselectivity for the linear aldehydes. Under the optimized reaction conditions, a turnover number (TON) of up to 2.3×10⁴ and linear to branched ratio (l/b) of up to 174.4 were obtained in the Rh^I‐catalyzed hydroformylation of terminal olefins. Remarkably, the catalysts were also found to be efficient in the isomerization–hydroformylation of some internal olefins, to regioselectively afford the linear aldehydes with TON values of up to 2.0×10⁴ and l/b ratios in the range of 23.4–30.6. X‐ray crystallographic analysis revealed the cis coordination of the ligand in the precatalyst [Rh( 3 d )(acac)], whereas NMR and IR studies on the catalytically active hydride complex [HRh(CO)₂( 3 d )] suggested an eq–eq coordination of the ligand in the species.     

Increased Water Reduction Efficiency of Polyelectrolyte‐Bound Trimetallic [Ru,Rh,Ru] Photocatalysts in Air‐Saturated Aqueous Solutions

The groundbreaking use of polyelectrolytes to increase the efficiency of supramolecular photocatalysts in solar H₂ production schemes under aqueous aerobic conditions is reported. Supramolecular photocatalysts of the architecture [{(TL)₂Ru(BL)}₂RhX₂]⁵⁺ (BL=bridging ligand, TL=terminal ligand, X=halide) demonstrate high efficiencies in deoxygenated organic solvents but do not function in air‐saturated aqueous solution because of the quenching of the metal‐to‐ligand charge‐transfer (MLCT) excited state under these conditions. The new photocatalytic system incorporates poly(4‐styrenesulfonate) (PSS) into aqueous solutions containing [{(bpy)₂Ru(dpp)}₂RhCl₂]⁵⁺ (bpy=2,2′‐bipyridine, dpp=2,3‐bis(2‐pyridyl)pyrazine). PSS has a profound impact on the photocatalyst efficiency, increasing H₂ production over three times that of deoxygenated aqueous solutions alone. H₂ photocatalysis proceeds even under aerobic conditions for PSS‐containing solutions, an exciting consequence for solar hydrogen‐production research.     

Thermoregulated Phase-separable Ru_3(CO)_(12)/PETPP Complex Catalyst for Hydrogenation of Styrene

The basic problem in homogeneous catalysis is the separation of catalyst from the reaction mixtures. To overcome this drawback, a number of methods have been developed. One of them is to attach homogeneous catalyst to supports 1. An alternative and well used approach involves liquid/liquid biphasic catalysis in which the catalyst and product reside in different phases and separation of the products is achieved simply by phase separation2. Recently, a concept of thermoregulated phase transf…     

Towards the Development of a Selective Ruthenium‐Catalyzed Hydroformylation of Olefins

The ruthenium‐catalyzed hydroformylation of 1‐ and 2‐octene to give preferentially the corresponding linear aldehyde is reported. The catalyst system comprising of Ru₃(CO)₁₂ and an imidazole‐substituted monophosphine ligand allows for high chemo‐ and regioselectivity. The hydroformylation proceeds with unprecedented rates for a ruthenium‐based catalyst.     

Rhodium‐Catalyzed Hydroformylation of 1,1‐Disubstituted Allenes Employing the Self‐Assembling 6‐DPPon System

A rhodium‐catalyzed hydroformylation of 1,1‐disubstituted allenes is reported. Using a Rh^I/6‐DPPon catalyst system, one can obtain β,γ‐unsaturated aldehydes in high regio‐ and chemoselectivity. The Z‐configured product is formed with up to >95 % selectivity when unsymmetrically 1,1‐disubstituted allenes are submitted to the reaction conditions. This is the first time that these interesting building blocks are accessible by hydroformylation of allenes. The utility of this methodology is demonstrated by further transformations of one of the obtained products.     

Labelling Studies to Determine Product Formation from Reactions of CO and Hydrogen Catalysed by Ru Clusters and Rh Complexes

Reaction of CO with hydrogen in the presence of [Ru₃(CO)₁₂], KI and N-methylpyrrolidone produces small amounts of methanol under mild conditions. Using D₂ the methanol is CD₃OD confirming that it is a product of CO hydrogenation. In the presence of added H₂O, CH _x D_1-y OH/D (y=0–3) are produced. Carrying out the same reaction in the presence of MeI water and RhCl₃·xH₂O (x=3–4) produces ethanoic acid in a slow reaction which continues for at least 64 h. The effects of different reaction parameters are discussed and labelling using ¹³CH₃I shows that some of the ethanoic acid originates from sources other than MeI whilst labelling with D₂, CD₃I, and/or D₂O suggest that some originates from CO and H₂. Electrospray mass spectrometry and high pressure infra-red spectroscopic studies show that the main species present in catalytic solutions are [HRu₃(CO)₁₁]⁻, [HRu₄(CO)₁₃]⁻ and [Ru(CO)₃I₃]⁻ for methanol carbonylation, [Ru(CO)₃I₃]⁻ and [RhI₂(CO)₂]⁻ for ethanoic acid production. A reaction carried out in the absence of [Ru₃(CO)₁₂] gave similar results to a reaction in which it was added, suggesting that the entire process may be catalysed by rhodium complexes alone. Electronic Supplementary Material  Supplementary material for this article is available at and is accessible for authorized users.

Synthesis and Application of Tetraphosphane Ligands in Rhodium‐Catalyzed Hydroformylation of Terminal Olefins: High Regioselectivity at High Temperature

A new class of substituted tetraphosphane ligands has been developed and applied in the rhodium‐catalyzed regioselective hydroformylation of terminal olefins. The high regioselectivity (linear selectivity is above 97 % for 1‐octene and 1‐hexene) at high temperature (140 °C) shown by these tetraphosphane ligands is remarkable considering the low regioselectivity commonly observed under similar reaction conditions when other bisphosphane analogues are used. The steric and electronic effects of substituents on the diarylphosphane moiety have also been examined.     

Hydrogenation of Cinnamaldehyde to Cinnamyl Alcohol over An Ultrafine Co—B Amorphous Catalyst

A novel Co-B amorphous alloy catalyst in the form of ultrafine particles was prepared by chemical reduction of CoCl2 with aqueous NaBH4, which exhibited excellent activity and selectivity during the hydrogenation of cinnamaldehyde to cinnamyl alcohol in liquid phase. The optimum yield of cinnamyl alcohol was 87.6%, much better than the yield of using Raney Ni, Raney Co and other Co-based catalysts.     

Direct Catalytic Hydrogenation of an Acrylonitrile‐Butadiene Rubber Latex Using Wilkinson's Catalyst

Summary: Hydrogenated acrylonitrile‐butadiene rubber is a high‐performance elastomer that has found important applications in the automobile industry and petroleum fields. A new catalytic process has been investigated for producing hydrogenated acrylonitrile‐butadiene rubber by direct hydrogenation of the rubber in latex form using RhCl(PPh₃)₃ as catalyst. The reactions were achieved without the addition of any organic solvents. This is the first time that the direct catalytic hydrogenation of an acrylonitrile‐butadiene rubber latex has been successfully realized in the absence of any organic solvent with a conversion of higher than 95% without cross‐linking of the polymer.

Effect of RhCl(PPh₃)₃/acrylonitrile‐butadiene rubber ratio on hydrogenation.     

Enhancement of Solar Fuel Production Schemes by Using a Ru,Rh,Ru Supramolecular Photocatalyst Containing Hydroxide Labile Ligands

Polyazine‐bridged Ru^IIRh^IIIRu^II complexes with two halide ligands, Cl^? or Br^?, bound to the catalytically active Rh center are efficient single‐component photocatalysts for H₂O reduction to H₂ fuel, with the coordination environment on Rh impacting photocatalysis. Herein reported is a new, halide‐free Ru^IIRh^IIIRu^II photocatalyst with OH^? ligands bound to Rh, further enhancing the photocatalytic reactivity of the structural motif. H₂ production experiments using the photocatalyst bearing OH^? ligands at Rh relative to the analogues bearing halides at Rh in solvents of varying polarity (DMF, CH₃CN, and H₂O) suggest that ion pairing with halides deactivates photocatalyst function, representing an exciting phenomenon to exploit in the development of catalysts for solar H₂ production schemes.     

高分散 Ru/MMT 催化剂的制备及其催化喹啉加氢性能

 通过简单的离子交换法制备出高分散的蒙脱土 (MMT) 负载 Ru 催化剂, 采用 X 射线衍射、X 射线光电子能谱、程序升温还原和高分辨透射电子显微镜等手段对催化剂进行了表征. 结果表明, 金属 Ru 在蒙脱土层间高度分散, Ru 的平均粒径约 2 nm. 在喹啉加氢反应中, 该催化剂显示出很高的反应活性和选择性. 在 2 MPa 和 60 °C 的温和条件下, 以水为溶剂时, Ru/MMT 催化喹啉加氢生成 1,2,3,4-四氢喹啉的选择性高于 96.4%, 喹啉转化率达 99.2%. 当温度升高到 140 °C、压力增加到 3 MPa 时, 不需要补加催化剂就可以将喹啉一步加氢生成十氢喹啉, 选择性高达 98.1%.     

Hydrogenation of N‐Acylcarbamates and N‐Acylsulfonamides Catalyzed by a Bifunctional [Cp*Ru(PN)] Complex

Awakening of the Cp one : The bifunctional complex 1 facilitates the interaction with substrates bearing less electrophilic carbon atoms than ketones, epoxides, and imides. The title reaction was applicable to the reduction of Evans' asymmetric alkylation products to the chiral alcohols along with good recovery of the chiral oxazolidinone auxiliary. EWG=electron‐withdrawing group.

     

Highly Enantioselective Hydrogenation of N‐Aryl Imines Derived from Acetophenones by Using Ru–Pybox Complexes under Hydrogenation or Transfer Hydrogenation Conditions in Isopropanol

The asymmetric reduction of N‐aryl imines derived from acetophenones by using Ru complexes bearing both a pybox (2,6‐bis(oxazoline)pyridine) and a monodentate phosphite ligand has been described. The catalysts show good activity with a diverse range of substrates, and deliver the amine products in very high levels of enantioselectivity (up to 99 %) under both hydrogenation and transfer hydrogenation conditions in isopropanol. From deuteration studies, a very different labeling is observed under hydrogenation and transfer hydrogenation conditions, which demonstrates the different nature of the hydrogen source in both reactions.