Hydroformylation Reaction Research Articles

Substrate scope driven optimization of an encapsulated hydroformylation catalyst.

Caged complexes can provide impressive selective catalysts. Due to the complex shapes of such caged catalysts, however, the level of selectivity control of a single substrate cannot be extrapolated to other substrates. Herein, the substrate scope using 41 terminal alkene substrates is investigated in the hydroformylation reaction with an encapsulated rhodium catalyst [Rh(H)(CO)3(P(mPy3(ZnTPP)3))] (CAT1). For all substrates, the amount of branched products formed was higher with CAT1 than with the unencapsulated reference catalyst [Rh(H)(CO)2(P(mPy3))2] (CAT2) (linear/branched ratio between 2.14 and 0.12 for CAT1 and linear/branched ratio between 6.22 and 0.59 for CAT2). Interestingly, the level of cage induced selectivity depends strongly on the substrate structure that is converted. Analysis of the substrate scope combined with DFT calculations suggests that noncovalent interactions between the substrate moieties and cage walls play a key role in controlling the regioselectivity. Consequently, these supramolecular interactions were further optimized by replacing the ZnTPP building block with a zinc porphyrin analog that contained OiPr substituents on the meta position of the aryl rings. The resulting caged catalyst, CAT4, converted substrates with even higher branched selectivity.

HYDROFORMYLATION OF METHYL ACRYLATE USING A PALLADIUM SCHIFF BASE CATALYST UNDER SYNGAS SOURCE

Hydroformylation of methyl acrylate can be carried out in a short time and without the use of syngas under microwave dielectric heating. We show that a Palladium Schiff base catalyst can control regioselectivity in heterogenous hydroformylation. Microwave irradiation, which produces greater yields in less reaction time and uses less energy than conventional heating systems, may carry out the hydroformylation reactions of the Methyl acrylate with greater efficiency and sustainability without using the CO and H2 cylinder. This method offers a hopeful prospect for a more sustainable future in chemical synthesis. Hydroformylation of Methyl acrylate using (PdL2)Cl2) (where L= N- (diphynylmethylide) Aniline (LA) and (E)-1-(2-methoxyphenyl)-N-phenylmethanimine (LB), as a catalyst at 120 oC for 20 minutes in the microwave and at 200 oC, 5 h in the conventional heating. This work demonstrates that methyl acrylates can be hydroformed in glyoxylic acid using a palladium catalyst system, producing the intended products, aldehydes, in outstanding yields and selectivities. Moreover, solventless synthesis using specific catalyst systems has improved catalytic performance compared to solvent-based reactions, attributed to higher reactant concentrations. Palladium complexes PdLA and PdLB gave excellent aldehyde yields in the microwave, 89 % (l/b ratio 96:4) and 86 % (95:5), respectively, over the conventional heating, which were analyzed by 1HNMR and GCMS spectroscopic techniques.

Heteroleptic dirhodium(II,II) acetato-bipyridyl complexes: Evaluation as catalyst precursors for hydroformylation reactions

The synthesis of cationic bimetallic ‘pseudo-paddlewheel’ dirhodium(II,II) acetato-bipyridyl complexes of the type [Rh2(OAc)2(bis-4,4′-R-bipy)2]2+ containing either acetate (AcO-) or hexafluorophosphate (PF6-) counter ions is described. In both series, the 4 and 4′ positions of each bipyridyl ligand are substituted such that R = H, CF3 or OMe (complexes 1-3 for AcO- and 4-6 for PF6- derivatives). As catalyst precursors for the hydroformylation reaction, the complexes were initially evaluated using 1-octene as a substrate. The complex which displayed the greatest chemoselectivity toward aldehydes was evaluated further as a catalyst precursor for the hydroformylation of styrene, cyclohexene and 7-tetradecene as substrates. A correlation between product distributions in terms of chemo- and regioselectivity in the hydroformylation reaction versus axial site interaction is delineated. Recyclability was achieved through suitable modification of the substituent and counter ion, culminating in a simplistic method of post-catalytic precursor collection with minimal reduction of the catalytic activity over 5 cycles.

Rh nanoparticles anchored on phosphorous-doped porous carbon for efficiently catalytic hydroformylation of alkenes

The hydroformylation of alkenes to prepare aldehydes using rhodium-based catalysts has been widely investigated, while homogeneous Rh catalysts always suffer from poor reusability. Herein, a promising solution was proposed to introduce phosphorous heteroatoms into a porous carbon support to fabricate a stable and efficient catalyst (Rh/P-mC). And the obtained Rh/P-mC had high hydroformylation activity under mild reaction conditions. The substrate expansion experiment using different alkene substrates and the catalyst cycling experiment demonstrated the universality and stability of this catalyst. The hydroformylation reaction mechanism was also proposed, and the effect of the interaction between phosphorus and rhodium on the hydroformylation reaction was verified. Thus, this work has great application prospects for the highly efficient catalytic hydroformylation of alkenes and provides an efficient method for the design of high-performance hydroformylation catalysts.

Nitrogen‐containing Porous Organic Polymer Supported Rhodium Catalyst for Hydroformylation of Olefins

AbstractThe hydroformylation reaction of olefins with syngas (CO/H2) to manufacture aldehydes is one of the largest homogeneous catalytic processes. However, it is important to extend the use of Rh catalysts promoted by nitrogen ligands to heterogeneous system. In this study, a nitrogen‐containing porous organic polymer supported Rh catalyst (Rh/TImT‐TBPT) was successfully synthesized, as well as showed excellent catalytic activity (TOF=216 h−1) and selectivity of aldehydes (98 %) in the hydroformylation of 1‐octene. Furthermore, the catalytic performance of Rh/TImT‐TBPT in the hydroformylation of various olefins was also investigated, displaying outstanding results. The catalytic material was characterized by FT‐IR, XRD, XPS, TEM, SEM and TGA in detail. The characterization data showed that Rh species were highly dispersed on the support, leading to the good stability. More importantly, the Rh/TImT‐TBPT catalyst could be separated from the reaction system at the end of the hydroformylation, and then reused in the next cycle under optimized conditions.

Quantitative ligand effect and mechanism insight of Rh-biphosphine complexes in hydroformylation of formaldehyde

Hydroformylation is one of the most important homogenous reactions with more than 10 million tons of aldehydes production each year. Due to monodentate ligands instable coordination under hydroformylation of formaldehyde, here, we introduced a range of chelating biphosphine ligands onto rhodium catalysts. Ligands, such as BINAP (TOFGA = 106.4 h−1), present higher activity relative to common monodentate ligand PPh3 (TOFGA = 73.4 h−1) with lower ligand to metal ratio. Density functional theory calculation revealed that Rh-biphosphine complexes follow the anion mechanism, with H2 oxidation addition being the rate-determining step. Activation strain analysis further demonstrated that lower H2 distortion energy resulting higher TOF of glycolaldehyde formation. Besides, the predictable quantitative structure–activity relationship model was established and suggested that both electronic and steric properties synergistically controlled formaldehyde hydroformylation activity. This combination of mathematical modeling and theoretical calculation will provide a reliable approach to activity prediction and catalyst design for important industrial hydroformylation reaction.

Modular Synthesis of Phosphite and Phosphoramidite Ligands for Rh‐Catalyzed Hydroformylation

AbstractRhodium‐catalyzed hydroformylation of olefins is an important method for synthesizing aldehydes, and it is worth noting that regioselectivity and enantioselectivity of the product controlled by ligand are the most commonly used strategies. The modular synthesis of phosphite and phosphoramidite ligands have significant advantages of simple synthesis and high catalytic activity, which was why these ligands have been widely used in hydroformylation reactions. Herein, we focus on the synthesis methods and design ideas of such ligands, as well as their application effects in hydroformylation reactions. This review aims to provide a reference for the design and synthesis of ligands in hydroformylation subsequently.

Tuning the framework flexibility and equilibrium of HRh(CO)2P2 active isomers in single-atom Rh/P&N-POPs catalysts for hydroformylation reactions

Tuning the microenvironment surrounding single atom metals is an effective but challenging way to regulate the performance of single atom catalysts (SACs). Herein, we prepared a series of P, N-abundant porous organic polymers (P&N-POPs) with diverse framework flexibility and coordination ability to serve as SACs’ carriers. The microenvironment (coordination site, coordination number) surrounding Rh and the equilibrium of ea/ee-HRh(CO)2P2 active species were effectively regulated in Rh/P&N-POPs catalysts. Our study shows that the specific active ee-HRh(CO)2(P)2 species confined in the flexible polymeric skeleton endowed the Rh/mPPh3&PPD-POP with superior activity (TOF = 2000 h−1), selectivity of aldehydes (93.5 %), ratio of linear aldehyde to branched aldehyde (l/b ratio = 15.9), favorable stability (10 recycling runs without activity loss) and extensive substrate applicability (19 kinds of olefins) in hydroformylation reactions. Multiple characterization techniques (EXAFS, STEM, in-situ FTIR etc.) were employed to get insights into this effective strategy to regulate the performance of single atom catalysts (SACs).

Tandem Hydroformylation-Aldol Condensation Reaction Enabled by Zn-MOF-74.

The tandem hydroformylation-aldol condensation (tandem HF-AC) reaction offers an efficient synthetic route to the synthesis of industrially relevant products. The addition of Zn-MOF-74 to the cobalt-catalyzed hydroformylation of 1-hexene enables tandem HF-AC under milder pressure and temperature conditions than the aldox process, where zinc salts are added to cobalt-catalyzed hydroformylation reactions to promote aldol condensation. The yield of the aldol condensation products increases by up to 17 times that of the homogeneous reaction without MOF and up to 5 times compared to the aldox catalytic system. Both Co2(CO)8 and Zn-MOF-74 are required to significantly enhance the activity of the catalytic system. Density functional theory simulations and Fourier-transform infrared experiments show that heptanal, the product of hydroformylation, adsorbs on the open metal site (OMS) of Zn-MOF-74, thereby increasing the electrophilic character of the carbonyl carbon atom and facilitating the condensation.

Boosting the Hydroformylation Activity of a Rh/CeO2 Single-Atom Catalyst by Tuning Surface Deficiencies

Controlling the interactions between atomically dispersed metal atoms and the support plays significant roles in determining the activity and selectivity of single-atom catalysts. In this report, we tuned the local coordination environment of Rh single atoms on CeO2 via calcination to construct a highly active hydroformylation catalyst. Single-atom Rh/CeO2 calcined at a high temperature exhibits more oxygen vacancies, which lead to the formation of a large amount of low-coordination Rh active species that are more active for hydroformylation. Under the optimum conditions, the best Rh/CeO2 catalyst achieved a TOF at approximately 5000 h–1 with 100% aldehyde selectivity in propylene hydroformylation to butanal. In situ FTIR spectroscopy and in situ XPS characterizations provide strong evidence that Rh on 800 °C-calcined CeO2 is easily activated to form surface HRh(CO)2 active species, favoring propylene adsorption and CO insertion. This work highlights the significance of engineering metal–support interactions in tuning the hydroformylation performance of single-atom catalysts and contributes to mechanistic insights into single-atom Rh-catalyzed hydroformylation reactions.

Rhodium nanoparticles supported on silanol-rich zeolites beyond the homogeneous Wilkinson’s catalyst for hydroformylation of olefins

Hydroformylation is one of the largest industrially homogeneous processes that strongly relies on catalysts with phosphine ligands such as the Wilkinson’s catalyst (triphenylphosphine coordinated Rh). Heterogeneous catalysts for olefin hydroformylation are highly desired but suffer from poor activity compared with homogeneous catalysts. Herein, we demonstrate that rhodium nanoparticles supported on siliceous MFI zeolite with abundant silanol nests are very active for hydroformylation, giving a turnover frequency as high as ~50,000 h−1 that even outperforms the classical Wilkinson’s catalyst. Mechanism study reveals that the siliceous zeolite with silanol nests could efficiently enrich olefin molecules to adjacent rhodium nanoparticles, enhancing the hydroformylation reaction.

In-situ adaptive evolution of rhodium oxide clusters into single atoms via mobile rhodium-adsorbate intermediates

It is a common phenomenon for supported metal catalysts to undergo thermally-induced or adsorbate-induced reconstruction. Great efforts have been devoted to making these reconstruction adaptive to the reaction environment instead of deactivation. Herein, we reported the evolution of initially inactive RhOx clusters on Al2O3 into the formation of catalytically active oxygen vacancies and Rh single atoms via mobile Rh-CO intermediates during hydroformylation of propene. The activated catalyst exhibited a high specific activity of 3.0 × 104 mol molRh–1 h–1 towards hydroformylation reaction. Mechanistic studies revealed the evolution paths. Specially, RhOx clusters were reduced by CO to form oxygen vacancy where the surrounding unsaturated Rh atoms enabled the chemisorption of CO*. Rh atoms that were ejected from RhOx clusters diffused on Al2O3 supports to generate Rh single atom via the formation of carbonyl or geminal dicarbonyl species. Meanwhile, the Rh atoms on clusters were also leached to the solution by the adsorbed CO molecules, followed by partial re-adsorption on the support. This work not only offers an efficient catalyst for propene hydroformylation, but also advances the understandings of dynamic evolution of catalysts.

Rhodium-catalyzed hydroformylation of strained dialkenes: Ligand effect on product selectivity and complex coordination mode

We reported the synthesis of new and easily tunable diphosphine ligands L1-L5 based on bis(1H-indol-3-yl)methane. Strained 2,5-norbornadiene and dicyclopentadiene were used as the substrates to elucidate the relationship between ligand structure and product selectivity in Rh-catalyzed hydroformylation. Details in NMR, HRMS and single-crystal X-ray diffraction revealed that the coordination number and oxidation state could change rapidly upon exposure of RhI-L complexes to air. More importantly, the special structure of ligand which led to intramolecular methylene C–H oxidative addition to metal center could facilitate the hydroformylation reaction in an unexpected way.

Recent Development of Single-Atom Catalysis for the Functionalization of Alkenes

The functionalization of alkenes is one of the most important conversions in synthetic chemistry to prepare numerous fine chemicals. Typical procedures, such as hydrosilylation and hydroformylation, are traditionally catalyzed using homogeneous noble metal complexes, while the highly reactive and stable heterogeneous single-atom catalysts (SACs) now provide alternative approaches to fulfill these conversions by combining the advantages of both homogeneous catalysts and heterogeneous nanoparticle catalysts. In this review, the recent achievement in single-atom catalyzed hydrosilylation and hydroformylation reactions are introduced, and we highlight the latest applications of SACs for additive reactions, constructing new C-Y (Y = B, P, S, N) bonds on the terminal carbon atoms of alkenes, and then mention the applications in single-metal-atom catalyzed hydrogenation and epoxidation reactions. We also note that some tandem reactions are conveniently realized in one pot by the concisely fabricated SACs, facilitating the preparation of some pharmaceutical compounds. Lastly, the challenges facing single-atom catalysis for alkene conversions are briefly mentioned.

The hydroformylation of 1-butene on phosphine modified 1Rh/MOF-5 prepared by different immobilization strategies

Immobilization of the Rh active sites in novel porous materials has attracted attentions for solving the problems of separation and recycling of homogeneous catalysts. In this work, a comparative study of phosphine modified 1Rh/MOF-5 using three different methods was reported, namely 1Rh-P/MOF-5, 1Rh/MOF-5-P and 1Rh/MOF-5-PPh3. Similar with the traditional methods, PPh3 was etched on Rh particles by impregnation in 1Rh-P/MOF-5 and encapsulated in the pores by solvothermal method in 1Rh/MOF-5-P. Moreover, we proposed a novel post-synthesis strategy for grafting phenyl phosphine on the organic linkers in 1Rh/MOF-5-PPh3. The position of phenyl phosphine in MOFs and the effect of phosphine on the Rh active sites in hydroformylation were investigated by XRD, IR, XPS, TGA and DRIFTS. 1Rh/MOF-5-PPh3 exhibited the best catalytic activity and stability than 1Rh-P/MOF-5 and 1Rh/MOF-5-P in the hydroformylation of 1-butene. Different P/Rh ratio in P-modified 1Rh/MOF-5 led to the spatial environment change around the Rh active sites. This study showed details in the role of phosphine ligands played in hydroformylation reactions and provided some guidance for MOFs materials in the immobilization of homogeneous catalysts.

Effect of OH-Group Introduction on Gas and Liquid Separation Properties of Polydecylmethylsiloxane.

Membrane development for specific separation tasks is a current and important topic. In this work, the influence of OH-groups introduced in polydecylmethylsiloxane (PDecMS) was shown on the separation of CO2 from air and aldehydes from hydroformylation reaction media. OH-groups were introduced to PDecMS during hydrosilylation reaction by adding 1-decene with undecenol-1 to polymethylhydrosiloxane, and further cross-linking. Flat sheet composite membranes were developed based on these polymers. For obtained membranes, transport and separation properties were studied for individual gases (CO2, N2, O2) and liquids (1-hexene, 1-heptene, 1-octene, 1-nonene, heptanal and decanal). Sorption measurements were carried out for an explanation of difference in transport properties. The general trend was a decrease in membrane permeability with the introduction of OH groups. The presence of OH groups in the siloxane led to a significant increase in the selectivity of permeability with respect to acidic components. For example, on comparing PDecMS and OH-PDecMS (~7% OH-groups to decyl), it was shown that selectivity heptanal/1-hexene increased eight times.

Enhancing stability via confining Rh-P species in ZIF-8 for hydroformylation of 1-octene.

The stability of Rh-based heterogeneous catalysts is a key issue in the hydroformylation of olefins. Confinement of active Rh species has been considered an effective strategy to achieve stable catalysts. In this work, a phosphine ligand was successfully confined in ZIF-8 material and coordinated with Rh metal by a reduction procedure to develop an efficient and stable Rh-based catalyst for hydroformylation of 1-octene. The results indicate that the catalyst reduced at 300°C under H2atmosphere exhibits better stability than that with NaBH4as reductant and undoped P catalyst. Various characterization studies demonstrate that the superior performance is due to the strong interaction between Rh metal and P, which inhibits the leaching of active Rh species. This work reveals an effective strategy for the synthesis of highly stable catalysts for use in the hydroformylation reaction.

Unique phosphine ligand synergy in asymmetric hydroformylation of styrene over the Rh@MOF-5 heterogeneous catalysis system

For the heterogeneous reaction of asymmetric hydroformylation (AHF), a highly decentralized active Rh site played a key role in enhancing the yield of chiral isomeric aldehydes.

Amino functionalized SBA-15 Loaded Rh Catalyst for Asymmetric Hydroformylation of Styrene

A recoverable Rh/N-SBA-15 heterogeneous catalyst for asymmetric hydroformylation of styrene was prepared by post grafting method. XRD, TG, 29Si MAS NMR and ICP characterization, revealed that the introduction of amino silane and RhCl3 had no adverse influence on the ordered mesoporous structure of the support. The Rh/N-SBA-15 catalyst was proved to be highly efficacious and stable for asymmetric hydroformylation of styrene. The experimental results demonstrated that amino silane improved the loading capacity of SBA-15 to RhCl3, and thereby improved its catalytic performance. The high efficiency and recyclability of Rh/N-SBA-15 catalyst demonstrated its great potential for application in asymmetric hydroformylation reactions.

Highly dispersed Rh single atoms over graphitic carbon nitride as a robust catalyst for the hydroformylation reaction.

Rhodium-catalysed hydroformylation, effective tool in bulk and fine-chemical synthesis, predominantly uses soluble metal complexes. For that reason, the metal leaching and the catalyst recycling are still the major drawbacks of this process. Single-atom catalysts have emerged as a powerful tool to combine the advantages of both homogeneous and heterogeneous catalysts. Since using an appropriate support material is key to create stable, finely dispersed, single-atom catalysts, here we show that Rh atoms anchored on graphitic carbon nitride are robust catalysts for the hydroformylation reaction of styrene.