Hydroformylation Catalysts Research Articles

Rhodium(I) N-Heterocyclic Carbene Complexes as Catalysts for Hydroformylation of Olefins: An Overview

The present state of art on the application of carbene-rhodium complexes as stable catalysts for hydroformylation reaction is described. A critical analysis of the influence of pressure and temperature on the hydroformylation of non-modified rhodium complexes and those ones described in the presence of carbenes is also done. Finally, a set of experiments using NHCs prepared by us at different reactions conditions is presented and discussed. Keywords: Aliphatic olefins, hydroformylation, rhodium, N-heterocyclic carbene ligands, Rhodium-NHC Complexes, Rhodium-Carbonyl Complexes, Influence of pressure, styrene, Influence of Temperature

RhCl(TPPTS) 3 encapsulated into the hexagonal mesoporous silica as an efficient heterogeneous catalyst for hydroformylation of vinyl esters

RhCl(TPPTS) 3 (TPPTS = m-trisulphonato triphenyl phosphine) was in situ encapsulated into the mesopores of hexagonal mesoporous silica (HMS) by in situ method. The catalyst was characterized by P-XRD, 31P-CPMAS NMR, FT-IR, N 2 adsorption, TGA, TEM and ICP techniques. These characterization confirmed the encapsulation and heterogenization of RhCl(TPPTS) 3. The synthesized heterogeneous catalyst evaluated for hydroformylation of vinyl esters gave 100% conversion and high selectivity to iso-aldehyde. Vinyl acetate was subjected as a representative vinyl ester for detailed investigations. The performance of the catalyst in terms of conversion and selectivity depended on the studied parameters: amount of the catalyst, substrate, partial pressure of CO and H 2, and temperature. Recyclability aspects of the heterogenized catalyst are investigated.

Triphenylphosphine modified rhodium catalyst for hydroformylation in supercritical carbon dioxide

The kinetics of 1-octene hydroformylation catalyzed by triphenylphosphine modified rhodium in carbon dioxide have been explored at 90 °C and pressures up to 48 MPa. The apparent catalyst solubility was determined by evaluating the reaction rate for different rhodium amounts. The kinetics follow a first order in 1-octene, a negative order of −1.2 in carbon monoxide, an order of 0.25 in hydrogen, and a negative order of −0.2 in triphenylphosphine, which is to a great extent in agreement with studies on the hydroformylation of linear 1-alkenes in organic solvents. The observed apparent turnover frequencies range from 1900 to 7000 mol aldehyde mol Rh −1 h −1. These turnover frequencies are of the same order of magnitude as observed for hydroformylations in organic solvents, indicating that rhodium modified with triphenylphosphine can be used with high efficiency in supercritical carbon dioxide rich mixtures.

Heteroatom‐Substituted Secondary Phosphine Oxides (HASPOs) as Decomposition Products and Preligands in Rhodium‐Catalysed Hydroformylation

O,O'-3,3'-Di-tert-butyl-5,5'-dimethoxy-1,1'-biphenyl-2,2'-diyl phosphonate (1) is the hydrolysis product of several mono- and bis-phosphites used as ligands in industrial hydroformylation and other catalytic reactions. As a result of a tautomeric equilibrium, this pentavalent heteroatom-substituted phosphine oxide (HASPO) can rearrange to the corresponding trivalent phosphorus compound. The latter is able to react with typical rhodium-containing precursors frequently used for the generation of catalysts. The resulting species were characterised by NMR spectroscopy and X-ray structure analysis. Proof is given that a rhodium complex of 1 forms an active hydroformylation catalyst. Moreover, 1 can add to aldehydes, which are generated as products in the hydroformylation. Thus a broad range of subsequent reactions can be associated with the degradation of the original phosphite ligands, which has a strong influence on the overall outcome of the hydroformylation reaction.

Influence of Phosphine Concentration on Propylene Hydroformylation over the PPh3-Rh/SiO2 Catalyst

The effect of triphenyl phosphine concentration in the novel PPh 3 -Rh/SiO 2 catalyst for propylene hydroformylation was studied and found an optimum P/Rh ratio of 15, a butyraldehyde n / i ratio of 14, a butyraldehyde TOF of 241 h −1 , and high catalytic stability for PPh 3 -Rh/SiO 2 . Solid-state 31 P NMR shows that in an atmosphere of syngas the physically adsorbed PPh 3 migrates onto the surface of Rh/SiO 2 where it chemically adsorbs and then promotes the in situ formation of carbonyl phosphine complexes. ：研究了 P/Rh 比对 PPh 3 -Rh/SiO 2 催化剂上丙烯氢甲酰化反应性能的影响. 结果表明, 当 P/Rh 比为 15 时, 丙烯氢甲酰化反应性能最好, 丙烯转化率为 25.9%, 产物丁醛正异比为 14, 转换频率为 241 h −1 . PPh 3 -Rh/SiO 2 催化剂的固体 31 P 核磁共振结果表明, 在合成气气氛下, 物理吸附的 PPh 3 能够溢流到 Rh/SiO 2 表面形成化学吸附的 PPh 3 , 从而促进了具有氢甲酰化活性的铑膦络合物的形成. Wilkinson 催化平衡理论也很好地解释了本实验结果. In a syngas atmosphere, the physically adsorbed PPh3 in PPh3-Rh/SiO2 catalysts migrate onto the surface of Rh/SiO2 and are chemically adsorbed before promoting the in situ formation of carbonyl phosphine complexes.

A General and Efficient Iridium‐Catalyzed Hydroformylation of Olefins

Breaking with conventional wisdom: Hydroformylation catalysts are generally based on rhodium; earlier, cobalt was used. Iridium, which is less expensive than rhodium, was considered too unreactive. However, iridium/phosphine complexes have now been shown to form active catalysts for the hydroformylation of olefins under mild conditions (see scheme; R1, R2=H, alkyl, aryl; R3=H, alkyl). Competing hydrogenation side reactions can be suppressed.

Hydroformylation activity of multinuclear rhodium complexes coordinated to dendritic iminopyridyl and iminophosphine scaffolds

The synthesis of poly(propyleneimine)-iminopyridyl and iminophosphine rhodium(I) metallodendrimers, with rhodium coordinated to monodentate ( N-donor) and chelating, heterobidentate ( P, N) moieties respectively located on the periphery, has been accomplished in order to evaluate their potential as hydroformylation catalysts. Related mononuclear complexes were obtained in a similar manner to model the multinuclear complexes. The multinuclear rhodium(I) complexes were found to be effective catalyst precursors in the hydroformylation of 1-octene, achieving higher conversions, faster reaction rates and slightly enhanced catalytic activity when compared with analogous mononuclear rhodium complexes. Hydroformylation reactions using the tetra- and octanuclear rhodium complexes generally show a chemoselective formation of aldehydes, together with a small amount of isomerisation products.

ChemInform Abstract: Promoting Effects of Se on Rh/ZrO2 Catalysis for Ethene Hydroformylation.

Abstract The positive effects of Se added to Rh/ZrO2 catalysts in ethene hydroformylation were studied from the viewpoints of promoter effects of electronegative atoms usually regarded as poisoning atoms as well as electronic interactions with both substrate metal and adsorbed species. Se-modified Rh/ZrO2 catalysts prepared by the reactive deposition of (CH3)2Se or coimpregnation method using SeO2 were found to be active and selective for ethene hydroformylation. The Se addition promoted the formation of propanol rather than propanal, the propanol formation being increased more than 70 times at an optimumSe/Rh ratio. The propanoyl intermediates were observed at ca. 1770 cm−1 converted reversibly to propionate species (bridge and bidentate) observed at 1425–1575 cm−1. The ensemble of Se2−/Rh was suggested to promote CO adsorption and the insertion of CO to ethyl species, where there is an electronic interaction between Se2− and CO or propanoyl species. The isotope effects of D2 and 13C18O showed the switchover of the rate-determining step for hydroformylation from the CO insertion on the Rh/ZrO2 catalysts to the dissociative adsorption of H2 on the SeRh/ZrO2 catalysts. The role of Se is discussed in relation with the reaction mechanism.

Secondary Phosphane Oxides as Preligands in Rhodium-Catalyzed Hydroformylation

Four aryl-substituted secondary phosphane oxides (SPOs) were tested as preligands in the rhodium catalyzed hydroformylation of cyclohexene and 1-octene. Three of them form active hydroformylation catalysts through their phosphinous acid tautomers. n-Regioselectivities of up to 56 % were achieved in the reaction with the linear olefin. The catalytic system with the electron-poor SPO showed exceptional behavior. In situ high-pressure IR spectroscopic investigations accompanied by DFT calculations provide an explanation of the observed inhibition of the catalytic reaction. Furthermore, proof is given that noncoordinated SPOs readily react with product aldehydes at room temperature to form α-hydroxyphosphinic acids. In contrast Rh-catalyzed hydrophosphination did not take place.

New Low-Temperature NMR Studies Establish the Presence of a Second Equatorial−Apical Isomer of [(R,S)-Binaphos](CO)2RhH

The important enantioselective hydroformylation catalyst [(R,S)-Binaphos](CO)2RhH has been reexamained by low-temperature NMR spectroscopy. Both 1H and 31P NMR spectroscopy at −90 °C allow direct observation of a mixture of two apical−equatorial chelates. The major chelate, 1eq,ap, was shown to have an equatorial phosphine and an apical phosphite. Its structure was unambiguously assigned using low-temperature 31P NMR spectroscopy with selective decoupling of aromatic hydrogens but not of the rhodium hydride, which showed a 225 Hz trans phosphite to RhH coupling. The equilibrium constant for [1eq,ap]/[1ap,eq] was determined over a wide temperature range.

Hydroformylation of Synthetic Naphtha Catalyzed by a Dinuclear gem-Dithiolato-Bridged Rhodium(I) Complex~!2009-09-28~!2009-12-18~!2010-04-23~!

This work focuses on the use of a gem-dithiolato-bridged rhodium(I) (Rh2(μ-S2CBn2)(cod)2) complex (cod = 1,5-cyclooctadiene, Bn2CS2 2� = 1,3-diphenyl-2,2-dithiolatopropane) dissolved in toluene in the presence of monodentate phosphite P-donor ligand (P(OPh)3) under carbon monoxide/hydrogen (1:1, syngas) atmosphere as an effective catalyst for hydroformylation of some olefins (oxo-reactions). The capability of this system to catalyze the hydroformylation of hex-1-ene, cyclohexene, 2,3-dimethyl-but-1-ene and 2-methyl-pent-2-ene and their quaternary mixture (synthetic naphtha) has been demonstrated. This innovative method to perform the in situ hydroformylation of the olefins present in naphthas to oxygenated products would be a promissory work for a future industrial catalytic process applicable to gasoline improving based on oxo-reactions. An important observation is that variation of CO/H2 pressure (6.8  34.0 atm), temperature (60  80 oC), reaction time (2  10 h), rhodium concentration ((1.0  1.8)x10 -3 mol/L) affect hydroformy- lation reaction rates. Optimal conversion to oxygenated products were achieved under (Rh) = 1.8 x10 -2 mol/L, P(CO/H2) = 34 atm (CO/H2 = 1:1) at 80 oC for 10 h.

Phenoxaphosphine-Based Diphosphine Ligands. Synthesis and Application in the Hydroformylation Reaction

The synthesis of a new series of diphosphine ligands based on 2,7-di-tert-butyl-9,9-dimethylxanthene (1), p-tolyl ether (2), ferrocene (3), and benzene (4) backbones, containing one or two 2,8-dimethylphenoxaphosphine moieties, is reported. The ligands were employed in the rhodium-catalyzed hydroformylation of 1-octene. For all four ligand backbones, introduction of phenoxaphosphine moieties led to an increase in catalytic activity and a decrease in regioselectivity toward the linear aldehyde product. Xanthene-based ligands 1a-1c yielded highly active and regioselective hydroformylation catalysts; ligands containing p-tolyl ether and ferrocene backbones 2a-2c and 3a-3c provided less active and less regioselective catalysts. Catalysts containing benzene-derived ligands 4a and 4b showed a remarkable preference for the formation of the branched aldehyde product. The coordination behavior of ligands 1-4 under hydroformylation conditions was investigated using high-pressureNMRand IRspectroscopy, revealing the distinct steric and electronic properties of the diphenylphosphine and 2,8-dimethylphenoxaphosphine moieties in ligands 1-4. The phosphacyclic moieties proved to be less basic and less sterically demanding toward other ligands in metal complexes than the acyclic diphenylphosphine moieties. For ligands that contain rigid backbones, the lack of conformational freedom in these phosphacyclic moieties does lead to repulsive interactions between the substituents of the two phosphorus donor atoms, resulting in an increase in the bite angle of the ligand. The low catalytic activity of rhodium catalysts modified by benzene-based ligands 4a-4c was attributed to the quantitative formation of HRh(L)2 under hydroformylation conditions.

Synthesis, characterization and coordination chemistry of a new phosphite–ether ligand: The effects of alkali metal salts and the ligand/Rh molar ratio on the catalytic activity and regioselectivity of a Rh(I) complex of this ligand in the hydroformylation of styrene

We have recently reported that the addition of alkali metal salts to styrene hydroformylation reactions catalyzed by Rh(I) complexes of bis(phosphite) ligands can significantly improve the iso/ n regioselectivity. To better understand the effects of the alkali metal salts on these styrene hydroformylation reactions, a monodentate phosphite–ether ligand, (2,2′-C 12H 8O 2)POCH 2CH 2OCH 3, 1 has been prepared, and its Rh(I) complex has been evaluated as a catalyst for the hydroformylation of styrene. Both the activity and regioselectivity of the catalyst are sensitive to the ligand:Rh molar ratio and to the presence of salts such as LiBPh 4·3dme, NaBPh 4 and HgCl 2. The most active catalyst has a 1:2.5 Rh:1 molar ratio and a 1:8 Rh:Li + molar ratio, but the most regioselective catalyst has a 1:8.2 Rh:1 ratio and a 1:4 Rh:Li + ratio. Model complexes for various steps in the catalytic cycle, cis-Mo(CO) 4( 1) 2, 6, cis-PtCl 2( 1) 2, 7, and PdCl 2( 1) 2, 8, have been synthesized and characterized by multinuclear NMR spectroscopy and X-ray crystallography to provide insight into the factors that may affect the rates and regioselectivities of the hydroformylation catalysts. The cis– trans isomerization of 6 in the presence of catalytic amount HgCl 2 has been carried out to determine the cis– trans preference of 1 in the octahedral coordination geometry.

Transition‐State Stabilization by a Secondary Substrate–Ligand Interaction: A New Design Principle for Highly Efficient Transition‐Metal Catalysis

A library of monodentate phosphane ligands, each bearing a guanidine receptor unit for carboxylates, was designed. Screening of the library gave some excellent catalysts for regioselective hydroformylation of beta,gamma-unsaturated carboxylic acids. A terminal alkene, but-3-enoic acid, was hydroformylated with a linear/branched (l/b) regioselectivity up to 41. An internal alkene, pent-3-enoic acid was hydroformylated with regioselectivity up to 18:1. Further substrate selectivity (e.g., acid vs. methyl ester) and reaction site selectivity (monofunctionalization of 2-vinylhept-2-enoic acid) were also achieved. Exploration of the structure-activity relationship and a practical and theoretical mechanistic study gave us an insight into the nature of the supramolecular guanidinium-carboxylate interaction within the catalytic system. This allowed us to identify a selective transition-state stabilization by a secondary substrate-ligand interaction as the basis for catalyst activity and selectivity.

Substrate influences on activity and stability of SBA-15– Pr-anchored Rh–P complex catalysts for olefin hydroformylation

RhCl 3 was immobilized to diphenylphosphinopropyl (– PrPPh 2)-modified mesoporous silica SBA-15 through a multi-step-assembly process. The prepared catalyst was characterized with reference to bulky and surface properties by X-ray diffraction (XRD), infrared spectroscopy (FT-IR), isothermal nitrogen sorption analysis and X-ray photoelectron spectroscopy (XPS). The metal content was determined by inductive coupling plasma-atomic emission spectroscopy (ICP-AES). The prepared rhodium-immobilized catalyst was employed in hydroformylation of several higher olefins of different lengths (C 6, C 8, and C 10), different C C bond positions (terminal or internal) or different structures (linear or branched). The substrate influences on the activity and recycling stability of the immobilized catalyst were investigated and are discussed. Shorter linear olefin substrates were more easily activated with higher catalyst specific activity, while the catalyst showed recycling stability in hydroformylation of longer and branched olefin substrates. For comparison, PPh 3 was externally added to immobilize RhCl 3 to – PrPPh 2-modified SBA-15. The immobilized catalyst so prepared showed a more flexible immobilizing structure and revealed a promoted turnover number of substrates.

Silicalite-1 membrane encapsulated Rh/activated-carbon catalyst for hydroformylation of 1-hexene with high selectivity to normal aldehyde

A tailor-made silicalite-1 membrane encapsulated catalyst with a size in millimeters has been directly synthesized over the activated-carbon supported Rh catalyst pellet to form a core–shell structure (S1/Rh/A.C.) by a hydrothermal synthesis method. For the reaction of hydroformylation of 1-hexene, the encapsulated catalysts present perfect catalytic performance for both the conversion and the normal to iso ratio of the aldehyde products. Increasing in the thickness of the silicalite-1 membrane can improve the selectivity of the normal products, but the reaction conversion decreases significantly. However, the modification of the encapsulated catalyst by tetraethyl orthosilicate (TEOS) can reduce the zeolite crystalline gaps to improve the normal aldehyde selectivity and to keep the similar 1-hexene conversion compared with that of the S1/Rh/A.C. catalyst. This encapsulated catalyst is efficient to produce and separate the aimed product from the multiple products in one-step with the spatial confined structure of the catalytic-inert silicalite-1 membrane.

Hydroformylation of alkenes using heterogeneous catalyst prepared by intercalation of HRh(CO)(TPPTS) 3 complex in hydrotalcite

Intercalation of HRh(CO)(TPPTS) 3 complex into the interlayer space of hydrotalcite was carried out to prepare an eco-friendly heterogeneous hydroformylation catalyst. Intercalated catalyst was characterized by 31P NMR, P-XRD, FT-IR, SEM and surface area measurements. Catalytic activity of intercalated catalyst [HT(3.5)-INT] was evaluated for hydroformylation of linear alkenes of varied carbon number from C 5 to C 13 as well as cyclic alkenes. Selectivity of the aldehydes was observed to decrease with increase in the carbon chain length of linear alkenes. Effect of reaction parameters on catalytic activity of intercalated catalyst was studied by varying the catalyst amount, 1-hexene concentration, reaction temperature, partial pressure of carbon monoxide and hydrogen for hydroformylation of 1-hexene. The catalyst was re-cycled up to five times without significant loss in the alkene conversion and selectivity of aldehydes.

Supramolecular Catalyst for Aldehyde Hydrogenation and Tandem Hydroformylation–Hydrogenation

Supramolecular Catalyst for Aldehyde Hydrogenation and Tandem Hydroformylation–Hydrogenation

Supramolecular Catalyst for Aldehyde Hydrogenation and Tandem Hydroformylation–Hydrogenation

Supramolecular Catalyst for Aldehyde Hydrogenation and Tandem Hydroformylation–Hydrogenation

Highly Regioselective and Active Rh–2,2′-Bis(dipyrrolylphosphinooxy)-1,1′-(±)-binaphthyl Catalyst for Hydroformylation of 2-Octene

Abstract Rhodium catalyst bearing 2,2′-bis(dipyrrolyphosphinooxy)-1,1′-(±)-binaphthyl (ligand 1) shows high regioselectivity and activity for the hydroformylation of 2-octene. The introduction of a pyrrolyl group in the ligand greatly improves the yield of the linear aldehyde. The regioselectivity is up to 97.5% under mild conditions (100 °C, 0.7 MPa H2/CO).