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)‐(^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.