Oxidation of palladium with allyl bromide and iodine in dimethylformamide

Article abstract of DOI:10.1023/B:RUGC.0000007607.86190.f9

The kinetic features of palladium oxidation with allyl bromide and iodine in dimethylformamide were determined. The apparent equilibrium constants, enthalpies, and entropies of reactant adsorption on the palladium surface were calculated.

Full text of DOI:10.1023/B:RUGC.0000007607.86190.f9

Russian Journal of General Chemistry, Vol. 73, No. 7, 2003, pp. 1040 1042. Translated from Zhurnal Obshchei Khimii, Vol. 73, No. 7, 2003,
pp. 1099 1101.
Original Russian Text Copyright
2003 by Piskunov, S. Maslennikov, Spirina, Manuilov, Novikov, V. Maslennikov.
Oxidation of Palladium with Allyl Bromide
and Iodine in Dimethylformamide
A. V. Piskunov, S. V. Maslennikov, I. V. Spirina,
A. V. Manuilov, V. A. Novikov, and V. P. Maslennikov
Research Institute of Chemistry, Lobachevsky Nizhni Novgorod State University, NIzhni Novgorod, Russia
Received June 27, 2001
Abstract The kinetic features of palladium oxidation with allyl bromide and iodine in dimethylformamide
were determined. The apparent equilibrium constants, enthalpies, and entropies of reactant adsorption on the
palladium surface were calculated.
An interest in oxidation of palladium with halogens
and various halohydrocarbons [1 5] is due to both
theoretical (detailed elucidation of the reaction mech-
anism) and applied (recovery of palladium from pro-
duction wastes) problems. However, some features of
previous studies [1 5] could affect their results. For
example, in [3] the reaction mixture was in contact
with air. In [5], the reaction was performed at a tem-
perature at which the oxidant could react with the
ligand at a noticeable rate to give products reactive
toward palladium. Furthermore, the kinetic features
of the reactions were not studied in [1 5].
oped process depends on the allyl bromide concentra-
tion COx at a constant ligand concentration C and on
L
the ligand concentration at a constant oxidant concen-
tration. The shape of the kinetic curves, in combina-
tion with data of [6], shows that the reaction is de-
scribed by the Langmuir Hinshelwood scheme [7],
with the adsorption of the oxidant and ligand on the
palladium surface occurring on active centers of dif-
ferent nature.
KOx
Ox + S1
L + S2
Ox(S1),
L(S2),
(1)
(2)
(3)
Our goal was to study the kinetics of palladium
oxidation with allyl bromide and iodine in dimethyl-
formamide (DMF).
KL
k
Figures 1 and 2 show how the rate V of the devel-
Ox(S ) + L(S )
Products.
1
2
4
4
3
2
0
1
2
1
1
5
0
3
2
8
4
2
5
0
1
1
0
2
4
6
8
10
, M
2
4
6
8
C
C H Br
CDMF, M
3
5
Fig. 1. Rate of palladium oxidation as a function of allyl
bromide concentration in DMF p-xylene (C 1.7 M).
Temperature, K: (1) 323, (2) 333, (3) 338, and (4) 343;
Fig. 2. Rate of palladium oxidation as a function of DMF
content in the reaction mixture. Inert solvent p-xylene,
DMF
the same for Fig. 2.
C
4.0 M.
C H Br
3
5
1
070-3632/03/7307-1040$25.00 2003 MAIK Nauka/Interperiodica

OXIDATION OF PALLADIUM WITH ALLYL BROMIDE
1041
Here, KOx and K are the equilibrium constants
of adsorption of the oxidant and ligand, respectively;
k is the rate constant of the reaction on the metal
surface.
L
8
6
In this case, the expression for the reaction rate has
the form
S S K K COxCL
0
1 02 Ox L
V = k
,
(4)
(
1 + KOxCOx)(1 + K C )
4
L
L
where S01 and S02 are the numbers of the correspond-
ing adsorption centers per unit surface area; k =
k S S .
0
1 02
2
0
Treatment of the kinetic data in the coordinates
/V = f(1/C ) at C = const and 1/V = f(1/C ) at
1
Ox
L
L
COx = const allowed calculation of the apparent equi-
librium constants of reactant adsorption on the metal
surface and of the reaction rate constants. From the
temperature dependences of these quantities, we deter-
mined the apparent activation energy of the process
and the apparent enthalpy and entropy of adsorption
of the oxidant and ligand on the palladium surface.
0
.05
0.10
0.15
0.20
C , M
I
2
Fig. 3. Rate of palladium oxidation in DMF at 333 K as
a function of the initial iodine concentration.
a peculiar shape with a sharp maximum (Fig. 2).
At the oxidant concentration corresponding to the
maximum, the metal removed from the mixture has a
dull surface, whereas at higher iodine concentrations
the palladium surface becomes covered with a dense
black precipitate, apparently preventing further reac-
tion. This fact did not allow determination of the
T, K
KOx 10
323
8.3
4.3
333
4.3
3.1
338
3.3
2.8
343
2.4
2.2
2
2
KL 10
k, g cm min 1 3.5 10
2
4
2.9 10 7.1 10 2.1 10 2
3
3
Ox
L
28 11 kJ mol 1;
Ea 187 11,
H
57 2,
H
ads
ads
Ox
ads
L
27 9 J mol 1 K 1
S
47 3,
S
ads
formal kinetics of the process. The yield of PdI was
2
After reaction completion, the unchanged metal
was removed, and the liquid phase was distilled off
at reduced pressure. The remaining oily liquid was
analyzed for the bromine content. The analysis results
show that 1 mol of metal reacts with 1 mol of allyl
bromide. Thus, in agreement with [1], the reaction
follows the scheme
determined at the initial iodine concentration corre-
sponding to the maximum in the plot V = f([I ]).
2
After removal of the liquid phase at reduced pressure
and recrystallization of the residue from acetone, the
IR spectrum of the product contained no bands assign-
1
able to N H vibrations (2450 cm ) in the dimethyl-
+
2
ammonium ion (CH ) NH , and the content of palla-
3
2
dium and iodine was consistent with the formula PdI2
(found, %: Pd 29.1; I 69.8. Calculated, %: Pd 29.5,
2
Pd + 2C H Br
(C H PdBr) .
(5)
3
5
3
5
2
I 70.5). The yield of PdI was 93% based on the dis-
2
An NMR study [8] showed that the halide bridges
in allylpalladium halides are broken in the presence
of dimethyl sulfoxide, and the allyl ligand becomes
solved metal. The difference between our results and
those obtained in [5] is due to different reaction con-
ditions.
-
coordinated. A similar process apparently occurs
EXPERIMENTAL
in DMF.
A part of the oily liquid was hydrolyzed by boiling
The IR spectra were recorded on an IKS-29 spec-
trophotometer.
with water, and the released propylene was deter-
mined chromatographically. Its amount was 0.47 mol
per mole of dissolved palladium, which, in agreement
with [9], corresponds to 94% yield of allylpalladium
halide.
Palladium wire (ultrapure grade, 99.999% main
substance, 0.2 mm in diameter) was used without
additional treatment. Crystalline I was of chemically
2
pure grade. Allyl bromide (pure grade) and DMF were
purified and dried by common procedures [10]. Liquid
reactants, if necessary, were degassed before use by
The dependence of the rate of palladium oxidation
with iodine in DMF on the iodine concentration has
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 73 No. 7 2003

1042
PISKUNOV et al.
repeated freeze pump thaw cycles. The content of
palladium [11] and bromine [12] in the reaction
product was determined photometrically with an SF-
Maslennikov, V.P., Metalloorg. Khim., 1992, vol. 5,
no. 5, p. 993.
7
8
. Bremer, H. and Wendlandt, K.-P., Heterogene Ka-
talyse: Eine Einfuhrung, Berlin: Akademie, 1978.
4
6 spectrophotometer. Iodine was determined by
argentometric titration [13]. Propylene was deter-
mined chromatographically (Tsvet-106 chromatograph,
thermal conductivity detector, 1000 5-mm glass
column packed with activated carbon, column and
detector temperatures 150 C, carrier gas helium, flow
. Chien, J.C.W. and Dehm, H.S., Chem. Ind., 1961,
no. 22, p. 745.
9. Huttel, R. and Ratzer, J., Angew. Chem., 1959, vol. 71,
no. 14, p. 456.
1
rate 40 ml min ). The kinetic measurements were
1
1
0. Gordon, A.J. and Ford, R.A., The Chemist’s Com-
panion. A Handbook of Practical Data, Techniques,
and References, New York: Wiley, 1972.
performed by the resistometric method [14] modified
to exclude contact with air.
1. Ginzburg, S.I., Ezerskaya, N.A., Prokof’eva, I.V.,
Fedorenko, N.V., Shlenskaya, V.I., and Belen’-
kii, N.K., Analiticheskaya khimiya platinovykh me-
tallov (Analytical Chemistry of Platinum Metals),
Ser.: Analiticheskaya khimiya elementov (Analytical
Chemistry of Elements), Moscow: Nauka, 1972,
p. 323.
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RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 73 No. 7 2003