The concentration effects of reactants and components in the Pd(OAc) 2/p-toluenesulphonic acid/trans-2,3-bis(diphenylphosphinomethyl)- norbornane catalytic system on the rate of cyclohexene hydrocarbomethoxylation

Article abstract of DOI:10.1016/j.apcata.2012.09.020

The reactants and components of a catalytic system were studied for their effects on the rate of Pd-catalysed cyclohexene hydrocarbomethoxylation. First-order reaction rate dependences were established for cyclohexene and Pd(OAc)₂, while non-monotonic rate dependences were determined for the diphosphine and p-toluenesulphonic acid concentrations and the SO pressure. The reaction was shown to follow first-order kinetics when the methanol concentration was below 0.4 mol/L; however, the reaction rate slowed upon a further increase in the methanol concentration. The obtained results were interpreted by considering a hydride mechanism supplemented with ligand exchange reactions, which decreased the activity of the catalyst, and with hydride complex annihilations by p-toluenesulphonic acid, resulting in complete loss of catalytic activity. Treatment of the proposed mechanism using the quasi-equilibrium concentration method gave a kinetic equation for the reaction that was consistent with the experimental data.

Full text of DOI:10.1016/j.apcata.2012.09.020

Applied Catalysis A: General 449 (2012) 145–152
Contents lists available at SciVerse ScienceDirect
Applied Catalysis A: General
journal homepage: www.elsevier.com/locate/apcata
The concentration effects of reactants and components in the
Pd(OAc) /p-toluenesulphonic
2
acid/trans-2,3-bis(diphenylphosphinomethyl)-norbornane catalytic
system on the rate of cyclohexene hydrocarbomethoxylation
a,d,∗
c
b
b
b
b
I.E. Nifant’ev
, N.T. Sevostyanova , V.A. Averyanov , S.A. Batashev , A.A. Vorobiev ,
a
d
S.A. Toloraya , V.V. Bagrov , A.N. Tavtorkin
a
Department of Chemistry, M.V. Lomonosov Moscow State University, 119992 Moscow, Russian Federation
L.N. Tolstoy Tula State Pedagogical University, 125 Lenin Prospect, 300026 Tula, Russian Federation
Department of Chemistry, Moscow State Pedagogical University, 1 M. Pirogovskaya, 119991 Moscow, Russian Federation
A.V. Topchiev Institute of Petrochemical Synthesis, 29 Leninsky prospect, 119991 Moscow, Russian Federation
b
c
d
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 10 May 2012
Received in revised form 6 September 2012
Accepted 27 September 2012
Available online 6 October 2012
The reactants and components of a catalytic system were studied for their effects on the rate of
Pd-catalysed cyclohexene hydrocarbomethoxylation. First-order reaction rate dependences were estab-
lished for cyclohexene and Pd(OAc)2, while non-monotonic rate dependences were determined for the
diphosphine and p-toluenesulphonic acid concentrations and the CO pressure. The reaction was shown to
follow first-order kinetics when the methanol concentration was below 0.4 mol/L; however, the reaction
rate slowed upon a further increase in the methanol concentration. The obtained results were interpreted
by considering a hydride mechanism supplemented with ligand exchange reactions, which decreased the
activity of the catalyst, and with hydride complex annihilations by p-toluenesulphonic acid, resulting in
complete loss of catalytic activity. Treatment of the proposed mechanism using the quasi-equilibrium
concentration method gave a kinetic equation for the reaction that was consistent with the experimental
data.
Keywords:
Hydrocarboalkoxylation
Catalytic carbonylation
Pd-catalysis
Phosphine-based catalysts
Esters
©
2012 Elsevier B.V. All rights reserved.
1
. Introduction
pair of products with linear and branched structures and is almost
free from cyclohexene and CO copolymerisation.
Olefin carbonylation catalysed by a transition metal complex
Among the catalytic systems used in alkene hydrocarbalkoxyla-
tion, palladium derivatives promoted by strong protic acids and
free phosphines are of particular interest [3,9–13]. In the series
of phosphines, diphosphines are used increasingly frequently.
Diphosphines are able to form chelates with the palladium centre of
the catalyst, which are more stable than standard monophosphine
derivatives and allow for more pronounced effects on the kinet-
ics and regioselectivities of the alkene hydroalkoxycarbonylation
reactions [4,14–16].
is a promising process for the production of various organic com-
pounds, particularly pharmacological and agrochemical agents [1].
An important carbonylation process is the palladium-catalysed
hydrocarbalkoxylation of alkenes, which is suitable for the one-
step conversion of widely available alkenes to various esters [2,3]
(
Scheme 1).
This process has already found use in industry. For example,
in 2008, Lucite commercialised the ethylene hydrocarbomethoxy-
lation process [4]. However, the hydrocarbalkoxylation of cyclo-
hexene to produce cyclohexylcarboxylates is also of interest for
commercialisation, as various cyclohexylcarboxylates are used as
plasticisers [5], intermediates in the synthesis of pharmacological
agents [6], liquid crystals [7], and in cosmetics [8]. The particular
synthetic value of cyclohexene hydrocarbalkoxylation comes from
the fact that this process is not complicated by the formation of a
Previously, we undertook
a special study to determine
how the structures of various diphosphines affect the rate of
cyclohexene hydrocarbomethoxylation [17]. That study revealed
the highest promoting activities known for trans-diphosphines
with four-membered carbon bridges; specifically, trans-2,3-
bis(diphenylphosphinomethyl)norbornane (TBDPN, Scheme 2)
was the most effective diphosphine studied for the promotion of
this process [17].
Based on the investigation on the effects of the Pd-
catalysed carbalkoxylation components on the reaction route
and the remarkable catalytic performance of trans-2,3-bis
∗ Corresponding author.
E-mail address: inif@org.chem.msu.ru (I.E. Nifant’ev).
0
926-860X/$ – see front matter © 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.apcata.2012.09.020

1
46
I.E. Nifant’ev et al. / Applied Catalysis A: General 449 (2012) 145–152
Table 1
Amounts of reactants and catalytic system components used in single experiments for cyclohexene hydrocarbomethoxylation.
Variable component
V(C6H10) (mL)
V(CH3OH) (mL)
V(o-xylene)
mL)
V(toluene)
(mL)
n(Pd(OAc)2)
(mmol)
n(TBDPN)
(mmol)
n(TsOH)
(mmol)
(
Cyclohexene
PCO
Methanol
Pd(OAc)2
TBDPN
0–0.506
0.506
0.506
0.506
0.506
0.506
0.608
0.912
0–3.04
0.912
0.912
0.912
0.306
0.306
0.306
0.306
0.306
0.306
48.580–49.086
48.276
46.148–49.188
48.276
48.276
48.276
0.100
0.100
0.100
0–0.625
0.050
0.050
0.300
0.300
0.300
2.00
0–1.0 0
1.20
1.20
1.20
1.50
0.60
a
TsOH
0.200
0–7.20
a
2
.00 mmol of free diphosphine TBDPN with allowance for its binding to Pd(OAc)2 in a 1:1 ratio = Pd(OAc)2:TBDPN.
(
diphenylphosphinomethyl)norbornane in cyclohexene hydrocar-
the catalytic system into the reaction medium. The moment of
introduction of the catalytic system was taken as the onset of
the reaction. Owing to the high promoting activity of trans-2,3-
bis(diphenylphosphinomethyl)norbornane, the reaction had no
autocatalytic region (see Fig. 1). Therefore, the initial reaction rates
were determined from the slopes of the initial sections of the
kinetic curves for the accumulation of methyl cyclohexanecarboxy-
late.
During the kinetic experiments, the reaction mixture was sam-
pled at specific time intervals, and the samples were analysed
by gas–liquid chromatography on a Tsvet-162 chromatograph
(Tsvet Company) with a flame ionisation detector. The anal-
yses were performed using 3000× 3-mm glass columns. The
separation was performed with Chromosorb W (80/100 mesh)
bomethoxylation, we performed a separate study on the kinetics of
this reaction, which is the subject of this communication.
2
. Experimental
Trans-2,3-bis(diphenylphosphinomethyl)norbornane was syn-
thesised as described previously [17]. The hydrocarbomethoxy-
lation of cyclohexene was studied in a jacketed batch reactor
equipped with a sampler, which was described previously [18].
The reactor was a 120-mL autoclave made of diamagnetic steel,
which enabled efficient stirring of the reaction mixture with a
magnetic stirrer. The autoclave temperature was monitored by a
pre-calibrated chromel–copel thermocouple. A constant temper-
ature was maintained by circulating a high-temperature organic
heat medium (polymethylsiloxane) through the reactor jacket.
During the kinetic experiments, the temperature was maintained
and an OV-275 3% stationary phase.
A carrier gas (argon)
flow rate of 30 mL/min and an evaporator temperature of
◦
225 C were also utilised. A temperature program increased
◦
◦
◦
with an accuracy of ± 0.5 C. The autoclave pressure was measured
the temperature from 75 to 205 C at a rate of 8 C/min[0].
Chromatographic calculations were performed using Multi-
Chrom software (A. Schwartz, Foley & Lardner, Alexandria, VA).
The chromatographic peaks of the reactants and products were
by a standard pressure gauge attached to the lid. The experiments
◦
were performed in toluene at a constant temperature (105 C) and
6
CO pressure (2.1 × 10 Pa). In the experiments testing the effects
of CO, the CO pressure was varied from 0 to 5.1 MPa. In all of the
experiments, o-xylene was used as the internal standard for chro-
matography. The compositions of the reaction systems used are
summarised in Table 1.
The kinetic experiment comprised the following sequence
of operations.
and o-xylene (the internal standard for chromatography) in
toluene was placed in an autoclave. catalytic mixture
A 50 mL mixture of cyclohexene, methanol,
A
of Pd(OAc)2, p-toluenesulphonic acid (TsOH), and trans-2,3-
bis(diphenylphosphinomethyl)norbornane was placed in a special
glass container fastened to the autoclave lid. The autoclave was
6
purged three times with 0.3 × 10 Pa of CO and then pressurised
6
to (0.4–1.6) × 10 Pa at room temperature. Next, the system was
◦
heated to 105 C, and the CO pressure was increased to the desired
◦
value. After the specified temperature (105 C) and CO pressure
were established, the glass container containing the catalytic sys-
tem was immersed in the reaction solution, thus introducing
Fig. 1. Kinetic curves for the accumulation of methyl cyclohexanecarboxy-
late over time for different cyclohexene concentrations: (1) 0.04 mol/L, (2)
0
.06 mol/L, and (3) 0.07 mol/L. T = 378 K; PCO = 2.1 MPa; concentrations (mol/L):
−
3
−3
−2
,
[
CH3OH] = 0.30, [Pd(OAc)2] = 2.0 × 10 , [TBDPN] = 6.0 × 10 , [TsOH] = 2.4 × 10
−
2
Scheme 1.
and [o-xylene] = 5.0 × 10
.
Scheme 2.

I.E. Nifant’ev et al. / Applied Catalysis A: General 449 (2012) 145–152
147
Table 2
Ratio of the amounts of reactants that participated in hydrocarbomethoxylation to the amount of methyl cyclohexanecarboxylate that was produced. T = 378 K. Conversion
of C6
Н
10 = 100%. Р= 4.1 MPa.
Run
Amount of starting
cyclohexene (mmol)
Amount of residual
cyclohexene (mmol)
Amount of starting
methanol (mmol)
Amount of residual
methanol (mmol)
Amount of methanol
that reacted (mmol)
Amount of the
ester (mmol)
1
.
4.84
4.84
4.84
0.01
0
0
9.68
24.2
14.5
4.83
19.34
9.69
4.85
4.86
4.81
4.82
4.85
4.83
2
.
3
.
identified based on their retention times, and the content of each
component was determined using chromatograms of artificial mix-
tures of known concentrations.
3.2. The effects of CO pressure on the rate of cyclohexene
hydrocarbomethoxylation
To elucidate the correlation between the amounts of reac-
tants that reacted and the methyl cyclohexanecarboxylate that
was produced, we carried out balance experiments on cyclohex-
ene hydrocarbomethoxylation. In all experiments, the cyclohexene
conversion was optimised to 100%. The results of selected experi-
ments are presented in Table 2.
A family of kinetic curves for different pressure values was cre-
ated from the data generated by varying the PCO and was similar
to that of the curves in Fig. 1. The dependence of the reaction
rate on the PCO corresponding to these data is shown in Fig. 3.
This dependence was non-monotonic and had a maximum at
PCO = 3.5 MPa.
Analysis of these data demonstrated the exact stoichiometric
correspondence between the reactants that reacted and the ester
that was produced, which occurred according to the following
equation:
COOCH3
C H + CO + CH OH
6
10
3
and confirmed that the reaction was not complicated by side
reactions.
These results were indirectly supported by the kinetic curves
for methyl cyclohexanecarboxylate accumulation (Fig. 1) and by
Fig. 1 (curve b) of a previously published report [17]. In the former
case, as the reaction progresses, the amount of the ester formed
approached the amount of cyclohexene, which was the limiting
reagent. In the latter case, the amount of the ester at the end of the
reaction strictly corresponded to the initial amount of cyclohexene.
This result seemed reasonable assuming the steric hindrance of the
cyclohexene in the acylpalladium intermediate, which hindered
alkene and CO co-polymerisation.
All experiments were carried out at 378 K and with a stirrer rota-
∗
tion speed of 600 rpm. In all cases, the inequality r /kLa · C ꢀ 0.1
0
CO
Fig. 2. Determination of the reaction order with respect to cyclohexene. T = 378 K;
−1
(
where kLa is the mass transfer coefficient (s ) [9]), which ensures
−
3
PCO = 2.1 MPa; concentrations (mol/L): [CH3OH] = 0.30, [Pd(OAc)2] = 2.0 × 10
,
the absence of diffusion retardation, was fulfilled.
TBDPN] = 6.0 × 10−3, [TsOH] = 2.4 × 10−2, and [o-xylene] = 5.0 × 10
−2
[
.
3
. Experimental results
The effects of the reactants and the catalytic system components
on the rate of cyclohexene hydrocarbomethoxylation were studied
in six experimental series. In each series, the concentration of one
component was varied.
3.1. The effects of the cyclohexene concentration on the rate of
hydrocarbomethoxylation
Some of the experimental results for the effects of the cyclo-
hexene concentration on the hydrocarbomethoxylation rate are
presented in Fig. 1 as time-dependent concentrations of the result-
ing methylcyclohexanecarboxylate ester. The initial reaction rates
(
r0) were determined by differentiating the initial sections of
the kinetic curves. The data obtained in these calculations are
presented in Fig. 2 as reaction rates (r ) that are dependent
0
upon the cyclohexene concentrations. The linear trend of these
dependences confirmed the first-order reaction rate of this reac-
tant.
Fig. 3. Effects of РCO on the rate of cyclohexene hydrocarbomethoxylation. T = 378 K;
−3
concentrations (mol/L): [C6H10] = 0.1, [CH3OH] = 0.45, [Pd(OAc)2] = 2.0 × 10
,
−
3
−2
−2
.
[TBDPN] = 6.0 × 10 , [TsOH] = 2.4 × 10 , and [o-xylene] = 5.0 × 10

1
48
I.E. Nifant’ev et al. / Applied Catalysis A: General 449 (2012) 145–152
Fig. 4. Determination of the reaction order with respect to methanol. T = 378 K;
Fig. 6. Effects of diphosphine TBDPN on the rate of cyclohexene hydro-
−
3
carbomethoxylation.
T = 378 K;
CO
P = 2.1 MPa;
concentrations
(mol/L):
PCO = 2.1 MPa; concentrations (mol/L): [C6H10] = 0.1, [Pd(OAc)2] = 2.0 × 10
,
TBDPN] = 6.0 × 10−3, [TsOH] = 2.4 × 10−2, and [o-xylene] = 5.0 × 10
−2
[C H10] = 0.1, [CH OH] = 0.45, [Pd(OAc) ] = 1.0 × 10−3, [TsOH] = 1.2 × 10−2, and
[
.
6
3
2
−
2
[
o-xylene] = 5.0 × 10
.
3
.5. The effects of the diphosphine TBDPN concentration on the
3
.3. The effects of methanol concentration on the rate of
rate of cyclohexene hydrocarbomethoxylation
cyclohexene hydrocarbomethoxylation
Differentiation of the initial sections of the kinetic curves
obtained for the different TBDPN concentrations further demon-
strated that r0 was dependent on the concentration of this
component (Fig. 6). This dependence was observed to be non-
The treatment of the kinetic curves showing the effects of
methanol on the rate of cyclohexene hydrocarbomethoxylation
(
similar to the curves in Fig. 1) produced the r vs. [CH OH] depend-
0 3
ence plotted in Fig. 4. This plot showed that, in the concentration
range of 0–0.4 mol/L, the reaction was first order with respect to
methanol concentration. When the methanol concentration was
increased beyond 0.4 mol/L, the reaction rate slowed.
−
2
monotonic at a diphosphine concentration of ∼0.3 × 10 mol/L,
indicating that the action of the diphosphine required a threshold
−
3
concentration of ∼10 mol/L.
3
.6. The effects of the p-toluenesulphonic acid concentration on
3.4. The effects of the palladium acetate concentration on the rate
the rate of cyclohexene hydrocarbomethoxylation
of cyclohexene hydrocarbomethoxylation
In the series of experiments studying the effects of the TsOH
concentration on the rate of hydrocarbomethoxylation, a family of
kinetic curves was obtained. Differentiation of the initial sections
Differentiation of the initial sections of the kinetic curves
obtained for the different Pd(OAc)2 concentrations suggested that
r0 was dependent on the concentration of this component (Fig. 5).
The linear pattern of this dependence revealed the first-order reac-
tion rate of the Pd(OAc)2 precursor.
of these curves produced the reaction rate (r ). The dependence
0
of the reaction rate on the TsOH concentration corresponding to
these data is plotted in Fig. 7. This dependence was non-monotonic,
and the maximum region was a plateau, indicating an approxi-
mately invariable rate in this region. However, after the plateau,
the rate decreased sharply to zero after an upper limit was reached
(∼0.12 mol/L).
4. Results and discussion
4.1. Hydrocarbomethoxylation mechanism
The results shown in Fig. 8 could be interpreted in the con-
text of the literature [3,12–14,19–21], which have reported that
the hydrocarbalkoxylation mechanism is catalysed by the joint
actions of palladium phosphine complexes and strong protic acids.
Specifically, analogues of the intermediates that appear in Fig. 8
have been previously isolated, characterised by spectroscopy, and
examined for their participation in the catalytic cycle. For instance,
HPd(PPh ) Cl, which corresponds to type Х , was prepared from
3
2
1
Pd(PPh3)4 and HCl and was found to produce carboxylic acids
upon the addition of 1-hexene, CO, and water [22]. Furthermore,
when HPd(PPh ) Cl was treated with ethylene, a hydride complex
3
2
Fig. 5. Determination of the reaction order with respect to palladium acetate.
T = 378 K; PCO = 2.1 MPa; concentrations (mol/L): [C6H10] = 0.1, [CH3OH] = 0.45,
isolated from the Pd(OAc) –P(C H -m-SO Na) system in aqueous
2
6
4
3
TBDPN] = 4.0 × 10− , [TsOH] = 3.0 × 10−2, and [o-xylene] = 5.0 × 10
2
−2
.
[
trifluoroacetic acid was converted to an alkylpalladium complex

I.E. Nifant’ev et al. / Applied Catalysis A: General 449 (2012) 145–152
149
the function of CO as a reactant in the catalytic cycle predominates.
However, at a high PCO, CO contributes to the deactivation of the
catalytic cycle by reacting with active intermediates and convert-
ing them to inactive or low-activity forms. This type of CO effect
could be present in, for example, reactions (9) and (10).
The effects of TsOH on the reaction rate (Fig. 7) deserve special
consideration because the ascending branch of the r0 vs. [TsOH]
plot was related to the function of this molecule as a hydride source,
which was responsible for the formation of the key intermediate
Х1 during the catalytic cycle (reaction (2)). The observed plateau
in this plot was consistent with similar plots that displayed the
effects of TsOH on the rates of alkene hydrocarbalkoxylations pro-
moted by monophosphines [10,12,13,19]. However, in all of these
cases, the plateau is maintained over the entire range of [TsOH]/[P]
ratios (up to 960) [19]. In the case of the diphosphine promoter,
the reaction rate was sharply reduced after a threshold TsOH con-
centration was reached, after which complete suppression of the
reaction occurred. In our opinion, the influence of TsOH was related
to its reaction with the hydride complex Х , as is presented in
1
Scheme 3 [3].
Fig. 7. Effects of TsOH on the rate of cyclohexene hydrocarbomethoxyla-
tion. T = 378 K; PCO = 2.1 MPa; concentrations (mol/L): [C6H10] = 0.1, [CH3OH] = 0.45,
The decrease in the rate of cyclohexene hydrocarbalkoxylation
following an increase in the TsOH concentration could, however,
also be attributed to the acid-induced destruction of the diphos-
phine TBDPN. This possibility could not be ruled out due to the
ability of the norbornane derivatives to undergo sigmatropic rear-
rangements in the presence of electrophilic reagents [32].
The obtained non-monotonic dependence of the reaction rate on
the diphosphine concentration (Fig. 6) was similar to the depen-
dences obtained by other authors for monophosphine ligands
[12,13,19]. The pattern of the dependence reflects the dual function
of the diphosphine. For instance, in the diphosphine concentra-
−3
−2
−2
.
[Pd(OAc)2] = 1.0 × 10 , [TBDPN] = 4.0 × 10 , and [o-xylene] = 5.0 × 10
of type Х , which reacted with CO to produce the correspond-
3
ing acyl complex. The acyl complex was subsequently hydrolysed
to produce propionic acid and a recovered hydride complex [23].
However, some Pd-containing reaction systems have also enabled
the isolation of acyl complexes of type Х , which were then con-
5
verted to carboxylic acids by treatment with aqueous solutions
of protic acids (e.g., HCl) or to esters when treated with alcohols
−
2
[
22,24–29]. Overall, these published data on the analogues of com-
tion range below 0.3 × 10 mol/L, an increase in its concentration
plexes Х , Х , and Х provide a strong basis for the proposed
accelerated the reaction by shifting the equilibrium (10) towards
1
3
5
scheme. The possibility of forming type Х0 Pd(0) complexes upon
the reduction of Pd(II) precursors with methanol has also been
demonstrated in the literature [12,13]. Additionally, the coordina-
the hydride intermediate Х . At higher concentrations, diphos-
1
phine could be involved in reactions with the intermediates of the
catalytic cycle, thus transforming some of the catalyst into inac-
tive or low-activity forms. A probable transformation of this type
tively saturated complex Х formed in reaction (1) has been shown
0
to add a TsOH molecule to produce the desired hydride complex
would be the formation of polynuclear palladium complex Х , in
9
(
reaction (2)) [3,19].
which diphosphine bridges link the palladium atoms (Scheme 4).
Based on this study, the first-order reaction rate of the cyclohex-
ene concentration (see Fig. 2) confirmed the negligible contribution
of the cyclohexene ␲-complexes to the overall balance of the pal-
ladium centre Х2 of the catalyst species.
4.2. Kinetic description of the cyclohexene
hydrocarbomethoxylation catalysed by a Pd(OAc) /TsOH/TBDPN
system
2
The first-order character of methanol at concentrations below
0
.4 mol/L indicated that methanol participates as a reactant in the
Presumably, the nucleophilic attack of the alcohol on the acyl-
palladium complex Х5 is the rate-determining step of the catalytic
cycle. This idea was supported by the sensitivity of the reaction rate
to the concentration of the alcohol and to the size of the molecule
[8,28], as well as by the possibility of isolating acylpalladium com-
plexes of type Х5 in measurable amounts [3,19,23,28]. In this way,
all of the preceding reversible steps could be considered to be in
equilibrium. Therefore, the reaction rate could be expressed by the
following equation:
final stage of the catalytic cycle. Specifically, the subsequent retar-
dation of the reaction rate following the increase in the methanol
concentration might indicate a role for methanol in the ligand
exchange reaction (8), which converted the hydride intermediate
Х to the low-activity species Х . For instance, the stronger coordi-
nating ability of the methanol molecule compared with that of the
tosylate anion makes the palladium centre in the hydride complex
Х less accessible. Toniolo et al. [19] reported similar data regarding
1
6
6
the role of methanol. In their report, styrene hydrocarbalkoxylation
in toluene was found to change from first order to a fractional order
as the methanol concentration increased. Thus, the retardation of
the reaction rate following an increase in the methanol concen-
tration was likely because of the involvement of methanol in the
ligand exchange with intermediates of the catalytic cycle, resulting
in the formation of less active forms of the palladium complexes.
This interpretation was also expressed previously [19].
The obtained non-monotonic dependence of the hydrocar-
bomethoxylation rate on the PCO was consistent with the data
presented by Toniolo [12,13], Petrov and Noskov [30], and El’man
et al. [31]. The pattern of this dependence indicated that there must
r = k7[X ][CH OH]
(11)
6
3
By applying the principle of quasi-equilibrium concentrations to
the mechanism as presented by reactions (1)–(10) and (Scheme 4),
with allowance for the first order reaction rate of cyclohexene, the
following kinetic equation is produced:
kCcatPCO[ol][TsOH][CH OH]
3
r =
(12)
1 + a[CH OH] · [TsOH] + bP2 + c(P2 [TsOH]/[P ]) + d[P ] + e[TsOH]
2
3
2
2
CO
CO
where Ccat is the concentration of the initial form of the catalyst
Pd(OAc)2 (mol/L), [ol] is the cyclohexene concentration (mol/L),
be an interplay between two PCO-dependent factors. At a low PCO
,
[P ] is the free diphosphine concentration (mol/L), and Р is the
2
CO

1
50
I.E. Nifant’ev et al. / Applied Catalysis A: General 449 (2012) 145–152
Fig. 8. Mechanism of Pd/phosphine-catalysed cyclohexene hydrocarbomethoxylation.
Scheme 3.

I.E. Nifant’ev et al. / Applied Catalysis A: General 449 (2012) 145–152
151
Fig. 9. Determination of the correspondence of Eq. (12) to the experimental data
regarding the effect of methanol concentration on the reaction rate. T = 378 K;
−
3
PCO = 2.1 MPa; concentrations (mol/L): [C6H10] = 0.1, [Pd(OAc)2] = 2.0 × 10
,
Fig. 10. Determination of the correspondence of Eq. (12) to the experimental
data regarding the effect of diphosphine TBDPN concentration on the reaction
rate. T = 378 K; PCO = 2.1 MPa; concentrations (mol/L): [C6H10] = 0.1, [CH3OH] = 0.45,
TBDPN] = 6.0 × 10−3, [TsOH] = 2.4 × 10−2, and [o-xylene] = 5.0 × 10
−2
.
[
−
3
−2
−2
.
[
Pd(OAc)2] = 1.0 × 10 , [TsOH] = 1.2 × 10 , and [o-xylene] = 5.0 × 10
CO pressure (MPa). k = k7K K K K5K , a = K K , b = K , c = K K10,
2
3
4
6
2
8
9
2
d = K and e = K .
1
1
2
To interpret the data and give consideration to the effects of
diphosphine, the difference between the concentrations of the ini-
Analysis of Eq. (12) indicates that, at low concentrations of TsOH,
the reaction should be first order with respect to this acid. This was
actually observed in the acid concentration range of 0–0.01 mol/L.
If the concentration is increased above 0.01 mol/L, the rate constant
should plateau.
tial diphosphine and Pd(OAc) was used as the concentration of the
2
free diphosphine, based on the formation of the Pd:P stoichiomet-
2
ric complexes (X , X , and X ):
0
1
2
The results of the single-factor experiments on the effects of the
concentrations of each reaction component confirmed that Eq. (12)
corresponded to the experimental data. Thus, when the methanol
concentration was varied, Eq. (12) was transformed to the following
form:
[
P ] = [P ] − Ccat
2
2
0
For the single-factor experiment examining the effects of
diphosphine on the reaction rate, Eq. (12) was transformed into
the following form:
kef.1[CH OH]
kef.2
3
r =
(13)
r =
(15)
A + a ∗ ·[CH OH]
2
3
B + (c ∗ /[P ]) + d · [P ]
2
2
where
kef.1 = kCcatPCO[ol][TsOH],
2
A = 1 + b · P2 + c ·
CO
where
kef.2 = kCcatPCO[ol][TsOH][CH3OH],
B = 1 + a ·
2
2
2
CO
2
CO
(
P
[TsOH]/[P ]) + d · [P ] + e[TsOH] and a∗ = a[TsOH].
[CH3OH][TsOH] + b · P + e[TsOH] and c∗ = c · P · [TsOH].
2
CO
Eq. (13) is also easily converted to the following:
Eq. (15) can be readily converted to the following:
[
CH OH]
A
a∗
+ k
[P2]
r
c∗
B
d
[P2]3
3
= k
· [CH OH]
(14)
=
+
[P2] +
(16)
3
r
kef.2
kef.2
kef.2
ef.1
ef.1
The least-squares estimation of the parameters of Eq. (16)
Therefore, the plot of [CH OH]/r vs. [CH OH] was linear (Fig. 9),
3
0
3
2
gives the following values: (c ∗ /kef.2) = (2 ± 2) × 10 min,
indicating that Eq. (12) matched the experimental data on the
effects of the methanol concentration on the reaction rate.
The least-squares estimation for the parameters of Eq. (14)
2
(B/kef.2) = (6.8 ± 0.2) × 10 L min/mol, and (d/kef.2) = (1.09 ±
6
3
3
0
.08) × 10 L min/mol . The plot of [P ]/r vs. [P ] shown in
2
0
2
2
produces the following values: (A/kef.1) = (0.90 ± 0.05) × 10 min
Fig. 10 confirmed the strong agreement between the calculated
(continuous line) and experimental (dots) data. Furthermore, the
2
and (a ∗ /kef.1) = (3.62 ± 0.07) × 10 L min/mol.
Scheme 4.

1
52
I.E. Nifant’ev et al. / Applied Catalysis A: General 449 (2012) 145–152
the ligand exchange reactions responsible for the inflections of the
plots of the reaction rate vs. the concentrations of alcohol, diphos-
phine, and CO, were considered. Additionally, the application of the
quasi-equilibrium concentration principle to the presented mech-
anism resulted in a kinetic equation for the reaction that was
consistent with the experimental data.
Acknowledgments
The reported study was partially supported by RFBR, research
project No. 12-08-31280-mol a.
References
[
1] K. Nozaki, I. Ojima, in: I. Ojima (Ed.), Catalytic Asymmetric Synthesis, 2nd ed.,
Wiley, New York, 2000, p. 429.
[
[
[
2] E. Drent, P.H.M. Budzelaar, Chem. Rev. 96 (1996) 663–681.
3] G. Kiss, Chem. Rev. 101 (2001) 3435–3456.
4] T. Fanjul, G. Eeastham, N. Fey, A. Hamilton, A.G. Orpen, P.G. Pringle, M. Waugh,
Organometallics 29 (2010) 2292–2305.
[
5] (a) K. Colle, J.E. Stanat, J.J., Reinoso, A.D.Godwin, WO Patent 2009/070398 to
(
2009) ExxonMobil.;
(
b) A.D. Godwin, WO Patent 2009/085453 (2009) to ExxonMobil.
Fig. 11. Determination of the correspondence of Eq. (12) to the experimental data
regarding the effect of CO pressure on the reaction rate. T = 378 K; concentrations
[
6] (a) U. Hoffmann, M. Jansen, R. Reents, H. Stahr, US Patent 2009/0253927 (2009)
to Hoffmann-La Roch Inc.;
−3
−3
,
(
[
mol/L): [C6H10] = 0.1, [CH3OH] = 0.45, [Pd(OAc)2] = 2.0 × 10 , [TBDPN] = 6.0 × 10
(
b) G.J. Harnett, U. Hoffmann, M. Jansen, R. Reents, T. Sattelkau, D.A. Smith, H.
−2
−2
.
TsOH] = 2.4 × 10 , and [o-xylene] = 5.0 × 10
Stahr, US Patent 2009/0253928 (2009) to Hoffmann-La Roch Inc.;
(
(
(
c) B. Lohri, US Patent 2009/0312569 (2009) to Hoffmann-La Roch Inc.;
d) A.M. Diederich, A.M. Eldridge, R.J. Mills, V.J. Novack, US Patent 6,740,765
2004) to SmithKline Beecham Corporation.
zero value for the [P ]/r function at the origin of the coordinates
2
0
[
7] S. Sugimori, US Patent 4617142 to Chisso Corp. (1986).
[8] K. Jenni, O. Springer, US Patent 20100068160 to Evonik Goldschmidt GmbH
(2010).
confirmed the statistical insignificance of the factor c ∗ /kef.2.
For the single-factor experiment on the effects of the CO pres-
sure on the rate of cyclohexene hydrocarbomethoxylation, Eq. (12)
was transformed as follows:
[
9] T.E. Kron, M.I. Terekhova, Yu.G. Noskov, E.S. Petrov, Kinet. Catal. 42 (2001)
04–211.
10] V.A. Averyanov, S.A. Batashev, N.T. Sevostianova, N.M. Nosova, Kinet. Catal. 47
2006) 381–390.
2
[
(
kef.3 · P
CO
r =
(17)
[11] N.T. Sevostyanova, S.A. Batashev, V.A. Averyanov, A.M. Demerley, Pet. Chem. 52
(2012) 35–40.
12] A. Vavasori, G. Cavinato, L. Toniolo, J. Mol. Catal. A: Chem. 176 (2001) 11–18.
[13] A. Vavasori, L. Toniolo, G. Cavinato, J. Mol. Catal. A: Chem. 191 (2003) 9–21.
[14] I. del Rio, N. Ruiz, C. Claver, L.A. van der Veen, P.W.N.M. Leeuwen, J. Mol. Catal.
A: Chem. 161 (2000) 39–48.
15] W. Clegg, G.R. Eastham, M.R. Elsegood, R.P. Tooze, X.L. Wang, K. Whiston, Chem.
Commun. (1999) 1877–1878.
16] E. Guiu, M. Caporali, D. Munoz, C. Muller, M. Lutz, A.L. Spek, C. Claver, P.W.N.M.
van Leeuwen, Organometallics 25 (2006) 3102–3104.
17] I.E. Nifant’ev, S.A. Batashev, S.A. Toloraya, A.N. Tavtorkin, N.T. Sevostyanova,
A.A. Vorobiev, V.V. Bagrov, V.A. Averyanov, J. Mol. Catal. A: Chem. 350 (2011)
2
C + b ∗ ·P
CO
[
where kef.3 = kCcat[ol][TsOH][CH OH], C = 1 + a · [CH OH] + d ·
3
3
2
[
P ] + e · [TsOH] and b∗ = b + (c · [TsOH]/[P ]).
2
2
Eq. (17) could also be represented as follows:
[
[
[
PCO
C
kef.3
b∗
+ k
2
CO
=
· P
(18)
r
ef.3
The linear trend of the PCO/r vs. P2 plot (Fig. 11) indicated that
0
CO
6
4–68.
18] A.R. El’man, V.A. Matveev, E.V. Slivinskii, S.M. Loktev, Pharma. Chem. J. 24 (1990)
17–221.
Eq. (12) was in agreement with the experimental data regarding the
effects of CO pressure on the reaction rate. The estimation of the
[
2
parameters for Eq. (18) resulted in the following values: (C/k ) =
[19] A. Seayad, A.A. Kelkar, L. Toniolo, R.V. Chaudhari, J. Mol. Catal. A: Chem. 151
(2000) 47–59.
[20] Yu.G. Noskov, A.I. Simonov, E.S. Petrov, Kinet. Catal. 41 (2000) 511–516.
[21] V.A. Averyanov, N.T. Sevostyanova, S.A. Batashev, Pet. Chem. 48 (2008)
ef.3
2
(
5.1 ± 0.4) × 10 MPa L min/mol and (b ∗ /k ) = (0.78 ± 0.01) ×
ef.3
2
1
0 L min/MPa mol.
2
87–295.
22] M.I. Terekhova, A.B. Sigalov, N.E. Petrova, E.S. Petrov, Russ. J. Gen. Chem. 55
1985) 944–945.
[
5
. Conclusion
(
[23] G. Verspui, I. Moiseev, R.A. Sheldon, J. Organomet. Chem. 586 (1990) 196–199.
[24] Yu.G. Noskov, A.I. Simonov, E.S. Petrov, Kinet. Catal. 42 (2001) 182–188.
[25] A. Seayad, S. Jayasree, K. Damodaran, L. Toniolo, R.V. Chaudhari, J. Organomet.
Chem. 601 (2000) 100–107.
The kinetics of cyclohexene hydrocarbomethoxylation catal-
ysed by the Pd(OAc) /trans-2,3-bis(diphenylphosphinomethyl)
2
norbornane/p-toluenesulphonic acid system were studied. The
first-order reaction rates of Pd(OAc)2 and cyclohexene, as well
as the non-monotonic rate dependences (which have maxima)
on the diphosphine and p-toluenesulphonic acid concentrations
and PCO, were established. Based on these data, the reaction was
found to follow first-order kinetics at methanol concentrations up
to 0.4 mol/L and then to slow as the concentration of methanol was
increased beyond this threshold.
[26] M.I. Terekhova, N.E. Petrova, R.R. Shifrina, E.S. Petrov, Russ. J. Gen. Chem. 58
1988) 658–661.
(
[
[
27] G. Cavinato, L. Toniolo, A. Vavasori, J. Mol. Catal. A: Chem. 219 (2004) 233–240.
28] R. Bardi, A.M. Piazzasi, G. Cavinato, L. Toniolo, Inorg. Chim. Acta 102 (1985)
99–103.
[
29] R. Bardi, A. Del Pra, A.M. Piazzasi, L. Toniolo, Inorg. Chim. Acta 35 (1979)
L345–L346.
[
30] E.S. Petrov, Yu.G. Noskov, Ross. Khim. Zh. 42 (1998) 149–157.
[31] H.A. Suerbaev, I.A. Tsukanov, A.R. El’man, K.A. Jubanov, J. Org. Chem. 64 (1994)
189–1191.
1
[
32] D. Barton, W.D. Ollis (Eds.), Comprehensive Organic Chemistry, vol. 1, Pergamon
Press, Oxford/New York, 1979.
To interpret the results, intermediate hydride, cycloalkyl, and
cycloacyl palladium complexes of the catalytic cycle, as well as