HYDROFORMYLATION OF 1-HEXENE WITH Rh_4(CO)_(12) AND [Rh(CO)_2Cl]_2

The hydroformylation of hexene-1 catalyzed by Rh4 （CO）12 and 〔Rh（CO）2Cl〕2 andthe effects of solvents （benzene, n-heptane and THF） and PPh3 on the activity andselectivity of the catalysts were studied.The results indicated that the activity of Rh4（CO）12 decreased with increasing solventpolarity and it did not change appreciably with addition of PPh3 when the molar ratioPPh3/Rh4（CO）12≤4. Thc activity of Rh4（CO）12 was over twice as large as that of〔Rh（CO）2Cl〕2 when calculated according to the number of moles of rhodium clusters inbenzene without PPh3, but the activities of both Rh4（CO）12 and 〔Rh（CO）2Cl〕2 wereabout the same when calculated according to the number of rhodium atoms. It is suggestedthat the clusters probably dissociated into the similar active rhodium mononuclear speciesunder the reaction conditions and the species formed a cluster similar to Rh4（CO）12 againwhen the conditions were reduced to the ambient temperature and pressure.

The hydroformylation of hexcne-1 catalyzed by Rh4(CO)12 and [Rh(CO )2C1]2 and the effects of solvents (benzene, n-heptane and THF) and PPh3 on the activity and selectivity of the catalysts were studied.The results indicated that the activity of Rh4(CO) 12 decreased with increasing solvent polarity and it did not change appreciably with addition of PPh3 when the molar ratio PPh3/ Rh4(CO)12≤4. The activity of Rh4(CO)12 was over twice as large as that of [Rh ( CO) 2Cl]2 when calculated according to the number of moles of rhodium clusters in benzene without PPh3, but the activitics of both Rh4(CO) 12 and [ Rh (CO) 2Cl]2 were about the same when calculated according to the number of rhodium atoms. It is suggested that the clusters probably dissociated into the similar active rhodium mononuclear species under the reaction conditions and the species formed a cluster similar to Rh4(CO) 12 again when the conditions were reduced to the ambient temperature and pressure.