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 the catalytic process. Among these, the 18-electron cobalt carbonyl hydride with a chiral bis(phosphine), ( R , R )-( iPr DuPhos)Co(CO) 2 H has been structurally characterized. Despite being an analog of rhodium precatalysts widely used in asymmetric hydroformylation, ( R , R )-( iPr DuPhos)Co(CO) 2 H promoted exclusive hydrogenation of styrene in the presence of 750 psi of H 2 /CO gas (1:1) at 100 masculineC. 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 beta-H elimination from cobalt alkyls occurred under an atmosphere of N 2 , alkylation of the cobalt chloride ( R , R )-( iPr DuPhos)Co(CO) 2 Cl in the presence of CO enabled the interception of a cobalt acyl complex, ( R , R )-( iPr DuPhos)Co(CO) 2 C(O)CH 2 CH 2 Ph. Hydrogenolysis of the cobalt acyl under 4 atm H 2 produced the corresponding aldehyde and cobalt hydride, demonstrating the feasibility of elementary steps in hydroformylation. While the hydride derivative was inert to CO substitution, the pi-donating chloride ligand in ( R , R )-( iPr DuPhos)Co(CO) 2 Cl underwent rapid CO dissociation (or exchange) to form a tetrahedral, S = 1 complex, ( R , R )-( iPr DuPhos)Co(CO)Cl.