Kinetic aspects of the influence of concentrations of methanol and the trans-2,3-bis(diphenylphosphinomethyl)norbornane promoting additive on the hydrocarbomethoxylation of cyclohexene catalyzed by the Pd(OAc)2/p-toluenesulfonic acid system

Abstract

The effects of temperature, the concentrations of methanol and the trans-2,3-bis(diphenylphosphinomethyl)norbornane (TBDPN) promoting additive on the rate of cyclohexene hydrocarbomethoxylation catalyzed by the Pd(OAc) 2 /ptoluenesulfonic acid system were studied. It was found that in the 358-383 K temperature range, the increase in the CH 3 OH concentration from 0 to 0.15 mol/L induces a virtually linear increase in the reaction rate, which slows down as the methanol concentration further increases. In the temperature range of 343-373 K, the dependences of the reaction rate on the TBDPN concentration pass through maxima at [TBDPN] = (3.0-4.0) 9 10 -3 mol/L. The results were interpreted in terms of the hydride mechanism that included diphosphinepalladium complexes as intermediates and was supplemented by ligand exchange reactions, resulting in a decrease in the activity of the palladium catalyst. The effective constants of the previously derived kinetic equation in the temperature range of 343-383 K were estimated by the least-squares method. The effective activation energies were determined and used to evaluate the enthalpy change in the ligand exchange reaction between the complexes Pd(TBDPN) 3 and [HPd(TBDPN)(CH 3 OH)]OTs. The zerovalent complex Pd(TBDPN) 3 was concluded to be more stable than the hydride complex [HPd(TBDPN)(CH 3 OH)]OTs.

Kinetic models of the cyclohexene hydromethoxycarbonylation catalyzed by the Pd(OAc)2/trans‐2,3‐bis(diphenylphosphinomethyl)norbornane/p‐toluensulfonic acid

“…Earlier in the temperature range 358–383 K in the region of initial rates, we established the first orders of this reaction by cyclohexene and Pd(OAc) 2 concentrations . We also detected extreme dependence of the initial rate on CO pressure and TBDPN concentration and nonlinear growth of the rate with increasing of the methanol concentration at the initial stage of hydromethoxycarbonylation . The interpretation of the established patterns was given on the basis of generally accepted hydride mechanism, and the equation of the initial reaction rate was obtained .…”

“…Nevertheless, to develop industrially important processes, it is necessary to study kinetics throughout the entire reaction to deep conversions. In this connection, we have continued our earlier research of the model reaction of cyclohexene hydromethoxycarbonylation catalyzed by the Pd(OAc) 2 / trans ‐2,3‐bis (diphenylphosphinomethyl) norbornane (TBDPN)/ p ‐toluensulfonic acid (TsOH) system (Scheme ).…”

“…We have entirely described the methods of kinetic experiment and reaction mixture analysis in Refs. .…”

“…On the basis of this mechanism, we obtained the equation of the initial reaction rate and estimated its effective constants under the conditions of one‐factor experiments on the various reaction participants: …”

“…The effective constants of this equation in the studied temperature range were estimated, and the effective activation energies were calculated on the basis of the Arrhenius equation. A comparison of the values of these energies allowed us to estimate the relative stability of some catalytically inactive palladium species in hydromethoxycarbonylation …”