Homogeneous Catalytic Hydrogenation of Carbon Monoxide

Klingler, R. J.; Rathke, J. W.

doi:10.1002/9780470166406.ch3

Cited by 4 publications

(1 citation statement)

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“…In comparison with our previous measurement for L = CO, these phosphine ligands span a range of Lewis basicities and differ considerably in their back-bonding characteristics when compared with CO. Accordingly, data of this type should be of considerable value in providing experimental benchmarks for theoretical investigations of cobalt carbonyl hydride chemistry. − The latter field spans an impressive range of reactions including the hydroformylation of olefins to aldehydes, − the Reppe carbonylation of olefins to carboxylic acids, the homologation of methanol to higher alcohols, − the BASF process for the carbonylation of methanol to acetic acid, and the hydrogenation of CO to methanol . The cobalt hydroformylation system based on the n -Bu 3 P ligand was patented by Slaugh and Mullineaux , and is considered representative of the Shell hydroformylation process. ,− We also report here on the solvent effect for hydride formation in eq 3 for this important phosphine ligand.…”

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confidence: 99%

Effect of Phosphines on the Thermodynamics of the Cobalt-Catalyzed Hydroformylation System

et al. 2006

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Thermodynamic parameters relevant to the phosphine-modified cobalt hydroformylation reaction are reported. Equilibrium constants for the hydrogenation of Co 2 (CO) 6 L 2 to yield HCo(CO) 3 L were determined using in situ 1 H and 31 P NMR spectroscopy between 75 and 175 °C for various solvents and phosphine ligands. Special emphasis was placed on n-Bu 3 P, as this ligand is prototypical of the Shell hydroformylation process. The resultant van't Hoff plots yield the enthalpy and entropy change (∆H ) 7.0 ( 0.4 kcal/mol and ∆S ) 2 ( 1 cal/mol•K) for the case of L ) n-Bu 3 P in benzene solvent. These parameters were found to be relatively insensitive to changes in the solvent, suggesting that the hydride product is not very polar. Even for isobutyl alcohol solvent, the resultant enthalpy and entropy changes (∆H ) 5.8 ( 0.4 kcal/mol and ∆S ) -2 ( 1 cal/mol•K) were found to be similar to those obtained in benzene and dioxane. Analysis of the 31 P NMR line widths allows rigorous lower limits to be established for the catalytically relevant Co-Co and Co-H bond energies in the case of L ) n-Bu 3 P (Co-Co g 23 kcal/mol and Co-H g 60 kcal/mol) relative to the previously reported values for the case of L ) CO (Co-Co ) 19 ( 2 kcal/mol and Co-H ) 59 ( 1 kcal/mol).

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