Synthesis and Reactivity of Organometallic Intermediates Relevant to Cobalt‐Catalyzed Hydroformylation

Abstract

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)‐(iPrDuPhos)Co(CO)2H 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)‐(iPrDuPhos)Co(CO)2D. Whereas rapid β‐hydrogen elimination from cobalt alkyls occurred under an N2 atmosphere, alkylation of (R,R)‐(iPrDuPhos)Co(CO)2Cl in the presence of CO enabled the interception of (R,R)‐(iPrDuPhos)Co(CO)2C(O)CH2CH2Ph, 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 13CO. Under reduced pressure, (R,R)‐(iPrDuPhos)Co(CO)2Cl underwent CO dissociation to form (R,R)‐(iPrDuPhos)Co(CO)Cl.

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

“…Hydroformylation of olefins is the most important process in the chemical industry to produce aliphatic aldehydes (global annual manufacture of around 10 million tons) for a range of applications. − Although the original cobalt-catalyzed process was discovered and commercialized more than 80 years ago, , there is still intense research both in industry and academia on this topic, especially regarding the development of new catalysts.…”

[Co(NHC)(CO)3]: Isolation and Reactivity Study of a Model 17-Electron Species in the Oxo Process

“…More than 10 billion kilograms (more than 1 kg for every person on Earth) of aliphatic aldehydes are produced annually using Co- or Rh-catalyzed hydroformylation of olefins . Despite the development of highly active and selective Rh-catalysts, improvement of Co-catalyzed hydroformylation is an attractive research target . The currently accepted mechanism for Co-catalyzed hydroformylation was first proposed by Heck and Breslow. , An unsolved question in this mechanism is how the activation of H 2 occurs with dinuclear [Co­(L)­(CO) 3 ] 2 or mononuclear [Co­(L)­(CO) 3 ] radical − (L = CO or PR 3 ) to generate a Co-hydride species, [HCo­(L)­(CO) 3 ], under high partial CO pressure ( P CO ) used in industrial hydroformylation (eq ).…”

Visible-Light-Enhanced Cobalt-Catalyzed Hydrogenation: Switchable Catalysis Enabled by Divergence between Thermal and Photochemical Pathways

“…By comparison, [(R,R)-( iPr DuPhos)Co(μ 2 -CO)] 2 , a precatalyst that differs by only one carbon monoxide ligand from 1, hydrogenates MAA with >99% ee (enantiomeric excess), suggesting an outer-sphere pathway with 1. 53 As has been reported previously, 19 the reaction of (R,R)-( iPr DuPhos)Co(CO) 2 D (1-D) with 5 equiv. of styrene in benzene at 60 °C for 3 h resulted in deuterium incorporation into the two β-positions of the alkene as well as in the formation of a small amount of α,β-deuterated ethyl benzene (Scheme 6).…”

“…Previous Work: (a) Reaction of 1 with Styrene under Thermal Hydroformylation Conditions Yields the Exclusive Hydrogenated Product. 19 (b) UV Irradiation Promoted the Hydrogenation of Olefins by Fe(CO) 5 . 26 absorbance at 267 nm, with a tail feature extending to 444 nm (Figure 1).…”

“…Such a pathway also accounts for the lack of thermal hydroformylation activity observed with 1. 19 Outer-sphere HAT between 1 and the alkene suppresses subsequent and requisite insertion events required for carbonylation; instead, capture of the alkyl and subsequent C−H bond formation release the alkane product.…”