Synthesis and Reactivity of Organometallic Intermediates Relevant to Cobalt‐Catalyzed Hydroformylation. (30th March 2020)

• Record Type: Journal Article
• Authors: MacNeil, Connor S.; Mendelsohn, Lauren N.; Zhong, Hongyu; Pabst, Tyler P.; Chirik, Paul J.
• Is Part Of: Angewandte Chemie. Volume 132:Number 23(2020)
• Page Start: 8997
• Page End: 9001
• Publication Date: 2020-03-30
• Subjects: acyl complex -- asymmetric catalysis -- cobalt -- P ligands -- structure elucidation; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.202001677
• Languages: English
• ISSNs: 0044-8249

Abstract

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 )‐( 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. Abstract : The 18‐electron cobalt hydride ( R, R )‐( iPr DuPhos)Co(CO)2 H has been synthesized. Despite being coordinatively saturated this compound promotes reversible 2, 1‐insertion of styrene and catalytic hydrogenation, raising questions as to the mechanism of action of the modified cobalt catalysts.