862079-94-5Relevant academic research and scientific papers
Hydroformylation of alkenes with paraformaldehyde catalyzed by rhodium-phosphine complexes
Rosales, Merlin,González, Angel,González, Beatríz,Moratinos, Cristhina,Pérez, Homero,Urdaneta, Johán,Sánchez-Delgado, Roberto A.
, p. 3095 - 3098 (2005)
The hydroformylation of medium-chain C6 olefins and of allyl alcohol was achieved with paraformaldehyde in dioxane solution using rhodium catalysts with mono-, bi-, and tri-dentate phosphine ligands. The highest activities with n/i ratios around 2, were obtained for a system derived from [Rh(dppe) 2]+, prepared in situ by reaction of Rh(acac)(CO) 2 with 2 eq of dppe.
Kinetics and mechanisms of homogeneous catalytic reactions. Part 6. Hydroformylation of 1-hexene by use of Rh(acac)(CO)2/dppe [dppe = 1,2-bis(diphenylphosphino)ethane] as the precatalyst
Rosales, Merlin,González, Angel,Guerrero, YusbeIi,Pacheco, Inés,Sánchez-Delgado, Roberto A.
, p. 241 - 249 (2007)
A kinetic study of the homogeneous hydroformylation of 1-hexene to the corresponding aldehydes (heptanal and 2-methyl-hexanal) was carried out using a rhodium catalyst formed by addition of 1 equiv. of 1,2-bis(diphenylphosphino)ethane (dppe) to Rh(acac)(CO)2 under mild reaction conditions (80 °C, 1-7 atm H2 and 1-7 atm CO) in toluene; in all cases linear to branched ratios were close to 2. The reaction rate is first-order in dissolved hydrogen concentration at pressures below 3 atm, but independent of this parameter at higher pressures. In both regimes (low and high H2 pressure), the initial rate was first-order with respect to the concentration of Rh and fractional order with respect to 1-hexene concentration. Increasing CO pressure had a positive effect on the rate up to a threshold value above which inhibition of the reaction was observed; the range of positive order on CO concentration is smaller when the total pressure is increased. The kinetic data and related coordination chemistry are consistent with a mechanism involving RhH(CO)(dppe) as the active species initiating the cycle, hydrogenolysis of the acyl intermediate as the rate-determining step of the catalytic cycle at low hydrogen pressure, and migratory insertion of the olefin into the metal-hydride bond as rate limiting at high hydrogen pressure. This catalytic cycle is similar to the one commonly accepted for RhH(CO)(PPh3)3 but different from previous proposals for Rh-diphosphine catalysts.
