95504-91-9Relevant academic research and scientific papers
MECHANISTIC ASPECTS OF CATALYTIC HYDROGENATION OF KETONES BY RHODIUM(I)-PERALKYLDIPHOSPHINE COMPLEXES
Tani, Kazuhide,Tanigawa, Eiji,Tatsuno, Yoshitaka,Otsuka, Sei
, p. 87 - 102 (1985)
Mechanistic aspects of the hydrogenation of ketones employing cationic rhodium(I) complexes ClO4 (NBD=norbornadiene) and ClO4 (CyDIOP=2,3-O-isopropylidene-2,3-dihydroxy-1,4-bis(dicyclohexylphosphino)butane) and a neutral complex, "Rh(CyDIOP)Cl" were studied.The cationic complex-catalyzed hydrogenation of the poor coordinating simple ketone substrates followed a rate equation r0=kobs00 and showed an unusual negative temperature dependence of the reaction rate.The hydrogenation of the chelating substrate PhCOCONHCH2Ph followed a rate equation r0=kobs with the activation parameters Ea 5.51 kcal mol-1, ΔH excit.308 4.90 kcal mol-1, ΔS excit.308-32.0 e.u. (ClO4 catalyst); Ea 5.36 kcal mol-1, ΔH excit.308 4.75 kcal mol-1, ΔS excit.308-30.9 e.u. (ClO4 catalyst).For the neutral complex-catalyzed hydrogenation of PhCOCONHCH2Ph, the rate equation r0=0.2500 was obtained with the activation parameters (Ea 3.99 kcal mol-1, ΔH excit308 3.38 kcal mol-1, ΔS excit.308-43.0 e.u.) Several intermediate complexes in the cationic complex-catalyzed hydrogenation were alo detected spectroscopically or isolated.On the basis of these observations, a general scheme was proposed.
