Kinetics and mechanisms of homogeneous catalytic reactions. Part 3. Regioselective, catalysed [RuH(CO)(NCMe)2(PPh3)2]BF4reduction of quinoline

✍ Scribed by Merlin Rosales; Ysaías Alvarado; Mirixa Boves; Raúl Rubio; Humberto Soscún; Roberto A. Sánchez-Delgado

• Publisher: Springer
• Year: 1995
• Tongue: English
• Weight: 551 KB
• Volume: 20
• Category: Article
• ISSN: 0340-4285
• DOI: 10.1007/bf00143486

✦ Synopsis

A kinetic study of the regioselective homogeneous hydrogenation of quinoline (Q) to 1,2,3,4-tetrahydroquinoline (THQ) was carried out using the cationic complex I-RuH-(CO)(NCMe)2(PPh3)2]BF4 (1) as the precatalyst. The experimentally determined rate law was r = {k2Kj(1

s-1 at 398 K). The corresponding activation parameters were found to be AH~=42+6kJmo1-1, ASS= -ll5___2JK-lmo1-1 and AG~=92+8kJmo1-1 Complex (1) was found to react with Q in CHC13 under reflux to yield

(2) which was also isolated from the hydrogenation runs. These experimental findings, together with the results of ab initio self-consistent-field molecular orbital calculations on the free organic molecules involved, are consistent with a mechanism involving a rapid and reversible partial hydrogenation of (2) to yield the corresponding dihydroquinoline (DHQ) species [RuH-(CO)(NCMe)(DHQ)(PPh3)z]BF 4 (4), followed by a ratedetermining second hydrogenation of DHQ to yield [RuH(CO)(NCMe)(THQ)(PPh 3)2]BF4 (3).