Cobalt-catalyzed Hydroformylation Research Articles

Ligand-induced suppression of undesirable pathways in cobalt-catalyzed hydroformylation

Ligand-induced suppression of undesirable pathways in cobalt-catalyzed hydroformylation

Cobalt-catalysed hydroformylation of epoxides in the presence of phosphine oxides

Phosphine oxides showed exceeding performance as promoters for the cobalt-catalyzed hydroformylation of epoxides to β-hydroxyaldehydes, which were hydrogenated in situ to 1,3-diols, important intermediates for polyesters and fibres.

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.

Cobalt-Catalyzed Hydroformylation under Mild Conditions in the Presence of Phosphine Oxides

In the presence of phosphine oxides, specifically triphenylphosphine oxide (P14), the cobalt-catalyzed hydroformylation of olefins takes place under mild conditions compared to traditional processe...

Synthesis and Reactivity of Organometallic Intermediates Relevant to Cobalt-Catalyzed Hydroformylation.

Intermediates relevant to cobalt-catalyzed alkene hydroformylation have been isolated and evaluated in fundamental organometallic transformations relevant to aldehyde formation. The 18-electron (R,R)-(iPr DuPhos)Co(CO)2 H has been structurally characterized, and it promotes exclusive hydrogenation of styrene in the presence of 50 bar of H2 /CO gas (1:1) at 100 °C. Deuterium-labeling studies established reversible 2,1-insertion of styrene into the Co-D bond of (R,R)-(iPr DuPhos)Co(CO)2 D. Whereas rapid β-hydrogen elimination from cobalt alkyls occurred under an N2 atmosphere, alkylation of (R,R)-(iPr DuPhos)Co(CO)2 Cl in the presence of CO enabled the interception of (R,R)-(iPr DuPhos)Co(CO)2 C(O)CH2 CH2 Ph, which upon hydrogenolysis under 4 atm H2 produced the corresponding aldehyde and cobalt hydride, demonstrating the feasibility of elementary steps in hydroformylation. Both the hydride and chloride derivatives, (X=H- , Cl- ), underwent exchange with free 13 CO. Under reduced pressure, (R,R)-(iPr DuPhos)Co(CO)2 Cl underwent CO dissociation to form (R,R)-(iPr DuPhos)Co(CO)Cl.

Computational Modelling of Selectivity in Cobalt-Catalyzed Propene Hydroformylation.

A mechanistic model for the cobalt-catalyzed hydroformylation of propene, based on density functional theory and coupled cluster electronic structure calculations and transition state theory, is proposed to explain the experimentally observed reactivity and selectivity. The electronic structure calculations provide very accurate energies, which are used with transition state theory to compute rate constants; the kinetics of the network of coupled reactions are then modelled numerically for this organometallic reaction. The model accounts well for the dependence of rate on the concentrations of catalysts and reagents, and also on the temperature, and the agreement with experiment is improved still further upon making small adjustments to the ab initio calculated free energy values. The calculations provide detailed kinetic insight into the mechanism of hydroformylation and the role of various elementary steps in defining reactivity and selectivity.

Synthesis of Polyamide Carboxylic Acid Containing Amino Acid via Amidocarbonylation

Herein, we synthesize and characterize polyamide carboxylic acids containing amino acid by polymerization via the amidocarbonylation of bifunctional components. Cobalt-catalyzed hydroformylation fo...

An automated method to find reaction mechanisms and solve the kinetics in organometallic catalysis.

A novel computational method is proposed in this work for use in discovering reaction mechanisms and solving the kinetics of transition metal-catalyzed reactions. The method does not rely on either chemical intuition or assumed a priori mechanisms, and it works in a fully automated fashion. Its core is a procedure, recently developed by one of the authors, that combines accelerated direct dynamics with an efficient geometry-based post-processing algorithm to find transition states (Martinez-Nunez, E., J. Comput. Chem.2015, 36, 222-234). In the present work, several auxiliary tools have been added to deal with the specific features of transition metal catalytic reactions. As a test case, we chose the cobalt-catalyzed hydroformylation of ethylene because of its well-established mechanism, and the fact that it has already been used in previous automated computational studies. Besides the generally accepted mechanism of Heck and Breslow, several side reactions, such as hydrogenation of the alkene, emerged from our calculations. Additionally, the calculated rate law for the hydroformylation reaction agrees reasonably well with those obtained in previous experimental and theoretical studies.

ChemInform Abstract: Computational Catalysis Using the Artificial Force Induced Reaction Method

AbstractReview: 33 refs.

Computational Catalysis Using the Artificial Force Induced Reaction Method.

The artificial force induced reaction (AFIR) method in the global reaction route mapping (GRRM) strategy is an automatic approach to explore all important reaction paths of complex reactions. Most traditional methods in computational catalysis require guess reaction paths. On the other hand, the AFIR approach locates local minima (LMs) and transition states (TSs) of reaction paths without a guess, and therefore finds unanticipated as well as anticipated reaction paths. The AFIR method has been applied for multicomponent organic reactions, such as the aldol reaction, Passerini reaction, Biginelli reaction, and phase-transfer catalysis. In the presence of several reactants, many equilibrium structures are possible, leading to a number of reaction pathways. The AFIR method in the GRRM strategy determines all of the important equilibrium structures and subsequent reaction paths systematically. As the AFIR search is fully automatic, exhaustive trial-and-error and guess-and-check processes by the user can be eliminated. At the same time, the AFIR search is systematic, and therefore a more accurate and comprehensive description of the reaction mechanism can be determined. The AFIR method has been used for the study of full catalytic cycles and reaction steps in transition metal catalysis, such as cobalt-catalyzed hydroformylation and iron-catalyzed carbon-carbon bond formation reactions in aqueous media. Some AFIR applications have targeted the selectivity-determining step of transition-metal-catalyzed asymmetric reactions, including stereoselective water-tolerant lanthanide Lewis acid-catalyzed Mukaiyama aldol reactions. In terms of establishing the selectivity of a reaction, systematic sampling of the transition states is critical. In this direction, AFIR is very useful for performing a systematic and automatic determination of TSs. In the presence of a comprehensive description of the transition states, the selectivity of the reaction can be calculated more accurately. For relatively large molecular systems, the computational cost of AFIR searches can be reduced by using the ONIOM(QM:QM) or ONIOM(QM:MM) methods. In common practice, density functional theory (DFT) with a relatively small basis set is used for the high-level calculation, while a semiempirical approach or a force field description is used for the low-level calculation. After approximate LMs and TSs are determined, standard computational methods (e.g., DFT with a large basis set) are used for the full molecular system to determine the true LMs and TSs and to rationalize the reaction mechanism and selectivity of the catalytic reaction. The examples in this Account evidence that the AFIR method is a powerful approach for accurate prediction of the reaction mechanisms and selectivities of complex catalytic reactions. Therefore, the AFIR approach in the GRRM strategy is very useful for computational catalysis.

Automated Prediction of Catalytic Mechanism and Rate Law Using Graph-Based Reaction Path Sampling.

In a recent article [ J. Chem. Phys. 2015 , 143 , 094106 ], we introduced a novel graph-based sampling scheme which can be used to generate chemical reaction paths in many-atom systems in an efficient and highly automated manner. The main goal of this work is to demonstrate how this approach, when combined with direct kinetic modeling, can be used to determine the mechanism and phenomenological rate law of a complex catalytic cycle, namely cobalt-catalyzed hydroformylation of ethene. Our graph-based sampling scheme generates 31 unique chemical products and 32 unique chemical reaction pathways; these sampled structures and reaction paths enable automated construction of a kinetic network model of the catalytic system when combined with density functional theory (DFT) calculations of free energies and resultant transition-state theory rate constants. Direct simulations of this kinetic network across a range of initial reactant concentrations enables determination of both the reaction mechanism and the associated rate law in an automated fashion, without the need for either presupposing a mechanism or making steady-state approximations in kinetic analysis. Most importantly, we find that the reaction mechanism which emerges from these simulations is exactly that originally proposed by Heck and Breslow; furthermore, the simulated rate law is also consistent with previous experimental and computational studies, exhibiting a complex dependence on carbon monoxide pressure. While the inherent errors of using DFT simulations to model chemical reactivity limit the quantitative accuracy of our calculated rates, this work confirms that our automated simulation strategy enables direct analysis of catalytic mechanisms from first principles.

From alkenes to alcohols by cobalt-catalyzed hydroformylation–reduction

The cobalt-catalyzed hydroformylation of alkenes in the presence of a range of novel cyclic phosphine ligands was investigated. The effect of various parameters such as solvents, additives, cobalt/phosphine ratio, CO/H2 (1:2), and nature of the alkenes was examined. The results revealed that both terminal and internal alkenes are hydroformylated in high yields to give mainly linear products at moderate temperature and syn gas pressure. The linearity ranges from 43 to 85%, with Lim-10 giving the highest proportion of linear product.

Computational Kinetics of Cobalt‐Catalyzed Alkene Hydroformylation

Density functional theory, coupled-cluster theory, and transition state theory are used to build a computational model of the kinetics of phosphine-free cobalt-catalyzed hydroformylation and hydrogenation of alkenes. The model provides very good agreement with experiment, and enables the factors that determine the selectivity and rate of catalysis to be determined. The turnover rate is mainly determined by the alkene coordination step.

Exploring transition state structures for intramolecular pathways by the artificial force induced reaction method

Finding all required transition state (TS) structures is an important but hard task in theoretical study of complex reaction mechanisms. In the present article, an efficient automated TS search method, artificial force induced reaction (AFIR), was extended to intramolecular reactions. The AFIR method has been developed for intermolecular associative pathways between two or more reactants. Although it has also been applied to intramolecular reactions by dividing molecules manually into fragments, the fragmentation scheme was not automated. In this work, we propose an automated fragmentation scheme. Using this fragmentation scheme and the AFIR method, a fully automated search algorithm for intramolecular pathways is introduced. This version for intramolecular reactions is called single-component AFIR (SC-AFIR), to distinguish it from multicomponent AFIR for intermolecular reactions. SC-AFIR was tested with two reactions, the Claisen rearrangement and the first step of cobalt-catalyzed hydroformylation, and successfully located all important pathways reported in the literature.

Ligand Effects on Reactivity of Cobalt Acyl Complexes

Hydrogenolysis reactions of cobalt acyl complexes, [Co(CO)3(L)(COR)] (L = phosphine, R = Me, nPr) have been monitored using in situ IR spectroscopy at moderate temperatures (<75 °C) and pressures (<25 bar). The reactions provide a model for the product-formation step in phosphine-modified, cobalt-catalyzed hydroformylation. The reaction kinetics are dependent on L, with the fastest rate being observed for the complex containing n-pentyl-9-phosphabicyclo[4.2.1]nonane (a5-PhobPC5). The observed dependence of rate on H2 and CO pressure is consistent with a mechanism involving initial CO dissociation, followed by reaction of [Co(CO)2(L)(COR)] with H2. Isotopic exchange experiments, monitored by IR spectroscopy, demonstrate that both terminal and acetyl carbonyls of [Co(CO)3(L)(COR)] exchange with free 13CO. Kinetic data are also reported for reactions of [Co(CO)3(L)(COR)] with triphenyltinhydride. A zero-order dependence on [Ph3SnH] (at large excess) and positive values of ΔS‡ demonstrate rate-determining CO dissociation. For a series of less bulky, symmetrical phosphines, the rates follow the sequence PEt3 < PMe2Ph ∼ PEtPh2 < PPh3 < P(4-ClC6H4)3, in accord with their electron-donating strength. Higher rates are found for more bulky phosphines, and the fastest rate is again found for L = a5-PhobPC5. Calculations using density functional theory indicate that the CO dissociation energy for [Co(CO)3(L)(COMe)] is influenced by the stereoelectronic properties of L, with steric bulk having a substantial effect. X-ray crystal structures are reported for [Co(CO)3(PEtPh2)(COMe)], [Co(CO)3(s-PhobPC5)]2, and [Co(CO)3(a5-PhobPC5)]2.

Protic metal-containing ionic liquids as catalysts: Cooperative effects between anion and cation

HCo(CO) 4 is known to be the active species in the cobalt-catalyzed hydroformylation reaction. Although it is known that the anion [Co(CO) 4] − is catalytically inactive, some cobalt carbonyl-containing ionic liquids are surprisingly able to catalyze hydroformylation reactions. However, only ionic liquids with protic cations demonstrate activity, whilst aprotic cations such as BMIM + result in a completely inactive compound. The four applied cobalt-containing ionic liquids differ only by the cation component. Their different performance in catalytic activity allows the presumption of cooperative effects between the cation and the anion. These fundamental influences of the cation on the hydroformylation kinetics give hints for the reaction mechanism of biphasic hydroformylation reactions as well as on the reaction pathways of the conventional hydroformylation reaction under different reaction conditions.

A Catalytic Route to Ampakines and Their Derivatives

A catalytic domino reaction that efficiently provides access to an important class of heterocycles, the ampakines, is reported. Our approach is based on the cobalt-catalyzed hydroformylation of dihydrooxazines and allows for the facile synthesis of the pharmaceutically interesting compound CX-614 and related substances.

ChemInform Abstract: Photochemical Hydroformylation of Olefins in the Cobalt-Phosphine Catalyst System.

Cobalt-catalyzed hydroformylation of olefins was found to proceed even at ambient temperature under UV irradiation in the presence of phosphine. Extremely high selectivity toward straight-chain aldehyde (99% in case of 1-hexene) was obtained by lowering the partial pressure of carbon monoxide at ambient temperature. A catalytic species different from the well-known species under high pressure of carbon monoxide and high temperature contributed to the highly selective formation of straight-chain aldehydes. Two photochemical processes were suggested to be involved in the photochemical hydroformylation reaction, that is, the formation of HCo(CO)3PBu3 from the cationic cobalt species, [Co(CO)3(PBu3)2]+, and then the formation of the coordinatively unsaturated hydride, HCo(CO)2PBu3.

ChemInform Abstract: Kinetics and Equilibrium of the Olefin-Promoted Interconversion of n- Butyryl- and Isobutyrylcobalt Tetracarbonyl. The Aldehyde Isomer Ratio in the Cobalt-Catalyzed Olefin Hydroformylation.

ChemInform Abstract: Kinetics and Equilibrium of the Olefin-Promoted Interconversion of n- Butyryl- and Isobutyrylcobalt Tetracarbonyl. The Aldehyde Isomer Ratio in the Cobalt-Catalyzed Olefin Hydroformylation.

Cobalt-Catalyzed Hydroformylation of Alkenes: Generation and Recycling of the Carbonyl Species, and Catalytic Cycle

Cobalt-Catalyzed Hydroformylation of Alkenes: Generation and Recycling of the Carbonyl Species, and Catalytic Cycle