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 H 2 /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 N 2 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)CH 2 CH 2 Ph, which upon hydrogenolysis under 4 atm H 2 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.