152639-59-3Relevant academic research and scientific papers
Kinetics and mechanism of the regioselective homogeneous hydrogénation of quinoline using [Rh(COD) (PPh3)2]PF6 as the catalyst precursor
Sánchez-Delgado, Roberto A.,Rondón, Deyanira,Andriollo, Antida,Herrera, Verónica,Martín, Gonzalo,Chaudret, Bruno
, p. 4291 - 4296 (1993)
The kinetics and mechanism of the regiospecific homogeneous hydrogenation of quinoline (Q) to 1,2,3,4-tetrahydroquinoline (THQ) using [Rh(COD)(PPh3)2]PF6 (1) as the catalyst precursor in toluene solution under mild reaction conditions have been studied. The experimentally determined rate law is ri = kcat[Rh][H2]2, where kcat = 50 ± 6 M-2 s-1 at 370 K; the corresponding activation parameters are ΔH? = 9 ± 1 kcal mol-1, ΔS? = -27.0 ± 0.3 eu, and ΔG? = 19.1 ± 0.3 kcal mol-1. Complex 1 was shown to react rapidly with Q to yield [Rh(COD)(PPh3)(Q)]PF6 (2) at room temperature and [Rh(COD)Q2]PF6 (4) in boiling toluene; complex 4 was also isolated almost quantitatively from the catalytic runs. Reaction of 1 with H2 followed by interaction with Q at room temperature produces [Rh(PPh3)2Q2]PF6 (3). These findings indicate that 4 is the catalytically active species and are consistent with a mechanism involving a rapid and reversible hydrogenation of one coordinated Q in 4 to dihydroquinoline (DHQ), followed by a rate-determining reduction of this intermediate to yield THQ. A catalytic cycle accounting for these results is postulated.
