Energetics of intermediates and reaction steps involved in the hydroformylation reaction catalyzed by HCo(CO)/sub 4/. A theoretical study based on density functional theory

Journal Article · Wed Mar 15 04:00:00 EST 1989 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00188a011· OSTI ID:5762616

Versluis, L; Ziegler, T; Baerends, E J; Ravenek, W

A theoretical study based on density functional theory has been carried out on the CO dissociation of HCo(CO)/sub 4/ and the migratory insertion reaction RCo(CO)/sub 4/ /yields/ RC(O)Co(CO)/sub 3/ for R = H and R = CH/sub 3/, respectively. RCo(CO)/sub 4/ was shown to form two stable isomers of trigonal-bipyramidal geometry. The configuration with R in axial position was lower in energy (63 kJ mol/sup /minus/1/ for R = H and 42 kJ mol/sup /minus/1/ for R = CH/sub 3/) than the corresponding isomer with R along the basal axis. The Co-CO dissociation energy of HCo(CO)/sub 4/ was found to be 186 kJ mol/sup /minus/1/. The resulting intermediate HCo(CO)/sub 3/ had as its most stable conformation a butterfly structure with the hydride in apical position. The migratory insertion of CO into the Co-CH/sub 3/ bond affords a coordinatively unsaturated acyl intermediate CH/sub 3/C(O)Co(CO)/sub 3/ that was found to form several stable isomers, with the ones that have the acyl oxygen facing the vacant site lowest in energy due to the formation of stable /eta//sup 2/ interactions. The reaction profile of the migration process was investigated by a linear transit procedure. The methyl 1,2-shift reaction to a cis-carbonyl group was found to have a low activation barrier and a reaction enthalpy of not more than 70 kJ mol/sup /minus/1/, whereas the direct insertion of a CO ligand into the Co-CH/sub 3/ bond was disfavored by an activation barrier of /approx/ 200 kJ mol/sup /minus/1/. The corresponding hydride migration to a neighboring CO group was considerably more endothermic and did not produce stable formyl intermediates on the Hartree-Fock-Slater energy surface. The alternative isomers with the formyl oxygen pointing toward the empty site were found to be stable but high in energy.

• Research Organization: Univ. of Calgary, Alberta (Canada)
• OSTI ID: 5762616
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 111:6; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CARBONYLS
CATALYSIS
CATALYSTS
CATALYTIC EFFECTS
CHALCOGENIDES
COBALT COMPLEXES
COMPLEXES
DATA
DISSOCIATION
INFORMATION
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
REACTION INTERMEDIATES
THEORETICAL DATA
THERMODYNAMICS
TRANSITION ELEMENT COMPLEXES