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.
All Science Journal Classification (ASJC) codes
- P ligands
- acyl complex
- asymmetric catalysis
- structure elucidation