Kinetics and mechanism of cyclohexene hydrocarbomethoxylation catalyzed by the Pd(OAc)2-PPh3-p-toluenesulfonic acid system

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

“…3 as non-monotonic dependences of the initial reaction rate on the TBDPN concentration with maxima at [TBDPN] = (2.5-4.0) 9 10 -3 mol/L, which is consistent with the results of other recent studies about the effect of concentration of free organophosphines on the rate of hydrocarboalkoxylation of alkenes [7,9,10,[12][13][14][15][16]18]. …”

“…However, these results differ from some other data. In particular, a non-monotonic dependence of the reaction rate on the alcohol concentration was reported for hydrocarbomethoxylation of cyclohexene in toluene catalyzed by the Pd(OAc) 2 /PPh 3 /ptoluenesulfonic acid system [14]. When the Pd(PPh 3 ) 2 Cl 2 /PPh 3 /p-toluenesulfonic acid catalytic system was used, non-monotonic dependences of the cyclohexene hydrocarboalkoxylation rate on the concentrations of methanol [10,11] and cyclohexanol [12,13] for reactions carried out in toluene were elucidated.…”

“…For example, in [8], the hydrocarboalkoxylation of cyclohexene was reported to have a zeroth order character with respect to methanol, the reaction being catalyzed by PdCl 2 /PPh 3 /HCl, while in another publication [9], first order dependence was established for the same reaction catalyzed by Pd(PPh 3 ) 2 (TsO) 2 /PPh 3 /TsOH. A non-monotonic pattern of dependences of the hydrocarboalkoxylation rate on the methanol or cyclohexanol concentration was observed for catalysis by Pd(PPh 3 ) 2 Cl 2 /PPh 3 /TsOH [10][11][12][13] and Pd(OAc) 2 /PPh 3 /TsOH [14]. The ascending branches of the non-monotonic curves at low alcohol concentrations were attributed to the action of alcohol as a reactant according to the mass action law, whereas the descending branches were interpreted as being due to the formation of inactive or low-active ''ballast'' forms of the palladium catalyst under the action of excess alcohol [7,[10][11][12][13][14].…”

“…A non-monotonic pattern of dependences of the hydrocarboalkoxylation rate on the methanol or cyclohexanol concentration was observed for catalysis by Pd(PPh 3 ) 2 Cl 2 /PPh 3 /TsOH [10][11][12][13] and Pd(OAc) 2 /PPh 3 /TsOH [14]. The ascending branches of the non-monotonic curves at low alcohol concentrations were attributed to the action of alcohol as a reactant according to the mass action law, whereas the descending branches were interpreted as being due to the formation of inactive or low-active ''ballast'' forms of the palladium catalyst under the action of excess alcohol [7,[10][11][12][13][14]. The descending branches of the curves for hydrocarboalkoxylation rate plotted versus the concentrations of organophosphines PPh 3 [10,[12][13][14][15] and TBDPN [7] and slower increase in the reaction rate at higher methanol concentrations [7] were interpreted in a similar way.…”

“…The ascending branches of the non-monotonic curves at low alcohol concentrations were attributed to the action of alcohol as a reactant according to the mass action law, whereas the descending branches were interpreted as being due to the formation of inactive or low-active ''ballast'' forms of the palladium catalyst under the action of excess alcohol [7,[10][11][12][13][14]. The descending branches of the curves for hydrocarboalkoxylation rate plotted versus the concentrations of organophosphines PPh 3 [10,[12][13][14][15] and TBDPN [7] and slower increase in the reaction rate at higher methanol concentrations [7] were interpreted in a similar way. As shown in a number of papers [11,13,15], studies of the temperature effect on the reaction rate provide a thermodynamic substantiation of the possible formation of inert ''ballast'' forms of the catalyst in the system and serves to compare stabilities of these species under the reaction conditions.…”