Oxidation of copper with dicarbonylcyclopentadienyliron chloride in polar solvents

Article abstract of DOI:10.1023/B:RUGC.0000007609.38388.b7

Dicarbonylcyclopentadienyliron chloride oxidizes copper in dimethylformamide and dimethyl sulfoxide to give copper(II) chloride and dicarbonylcyclopentadienyliron dimer. The apparent kinetic characteristics of the process and the thermodynamic parameters

Full text of DOI:10.1023/B:RUGC.0000007609.38388.b7

Russian Journal of General Chemistry, Vol. 73, No. 7, 2003, pp. 1051 1053. Translated from Zhurnal Obshchei Khimii, Vol. 73, No. 7, 2003,
pp. 1110 1113.
Original Russian Text Copyright
2003 by S. Maslennikov, Piskunov, Spirina, V. Maslennikov.
Oxidation of Copper with Dicarbonylcyclopentadienyliron
Chloride in Polar Solvents
S. V. Maslennikov, A. V. Piskunov, I. V. Spirina, and V. P. Maslennikov
Research Institute of Chemistry, Lobachevsky Nizhni Novgorod State University, Nizhni Novgorod, Russia
Received June 27, 2001
Abstract Dicarbonylcyclopentadienyliron chloride oxidizes copper in dimethylformamide and dimethyl
sulfoxide to give copper(II) chloride and dicarbonylcyclopentadienyliron dimer. The apparent kinetic charac-
teristics of the process and the thermodynamic parameters of adsorption of reactants on the metal surface
were determined. The reaction scheme was proposed.
In [1], we studied oxidation of magnesium with
5-
C H Fe(CO) Cl (I) in dimethylformamide (DMF).
Ali et al. [6] detected no reaction of DMSO with I at
300 K within a month in the absence of UV radiation.
5
5
2
We found that compound I, in contrast to the related
molybdenum and tungsten compounds [2], oxidizes in
dimethyl sulfoxide (DMSO) and DMF not only mag-
nesium, but also copper.
After reaction completion, the unchanged copper
was removed, and the major fraction of the solvent
was distilled off at reduced pressure. The residue was
treated with chloroform. The precipitate that formed
was identified by chemical analysis as [CpFe(CO)]4
[5, 7] (found Fe, %: 36.9. C H Fe O . Calculated
Fe, %: 37). When heated to 210 C, the compound
decomposes without melting. A similar result was
obtained in [7]. The structure of this compound is also
confirmed by spectral analysis. Its IR spectrum con-
tains no bands at 1955 and 1995 cm 1 characteristic of
In reaction of I with copper in these solvents, the
reaction stops at 20 30% conversion of the oxidant.
This is probably due to shielding of the metal surface
with the reaction products. The color of the reaction
mixture changes from red to red-brown. Monitoring of
the consumption of copper (gravimetrically) and I (by
2
4
20
4
4
a decrease in the intensity of the IR absorption band
1
2
048 cm ) shows that 2 mol of the oxidant is
terminal coordinated CO groups in [CpFe(CO) ] , and
CO
2 2
1
consumed per mole of the metal.
the band of bridging CO groups at 1776 cm is well
pronounced.
A study of copper oxidation with ethyl iodide in
DMSO [3] showed that the starting alkyl halide rap-
idly reacts with the solvent [4]. As a result, molecular
iodine is accumulated, which is actually the reactive
Our results suggest the following mechanism of
copper oxidation with I in DMF or DMSO.
species. Adsorption of I and DMSO molecules oc-
curs on metal surface centers of different nature.
L
2
CpFe(CO) Cl + Cu
CpFe(CO) CuCl.
(1)
2
2
II
Compound I used in this work as an oxidant does
not react with DMSO or, at least, its reaction with
DMSO is much slower than oxidation of the metal.
This is indicated, firstly, by the fact that the concen-
tration of I in the reaction mixture in the course of the
process does not noticeably differ from the concentra-
tion calculated assuming that the oxidant is spent
exclusively for copper oxidation. Secondly, chlorine
that could be formed in the reaction of DMSO with I
by the scheme given in [3] is considerably less soluble
The product of copper oxidation passes into the
solution and reacts therein with the second oxidant
molecule:
II + CpFe(CO) Cl
CuCl2 + [CpFe(CO) ] . (2)
2
2 2
III
The kinetic relationships of the reaction, given
below, support the suggested reaction scheme.
in DMSO than I , and it would evolve into the gas
2
phase. This would distort the chlorine balance [5] in
the reaction products, which disagrees with the exper-
iment (initial Cl concentration 0.100 M, concentra-
tion in the reaction products 0.102 M). Furthermore,
Formation of II is confirmed by the following
experiment. When HgCl was added to the starting
2
mixture in the concentration comparable with that of
the oxidant, bis(dicarbonylcyclopentadienyliron)mer-
1
070-3632/03/7307-1051$25.00 2003 MAIK Nauka/Interperiodica

1052
MASLENNIKOV et al.
cury was isolated from the reaction products as yel-
6
4
1
1
2
8
low-orange crystals, mp 145.9 C (published data [8]:
mp 146 C).
2
3
II + HgCl2
CuCl2 + [CpFe(CO) ] Hg. (3)
2 2
Dimer III formed by reaction (2) in accordance
with [7] transforms into the tetramer:
4
2
0
4
III
[CpFe(CO)]4 + 4CO.
(4)
The presence of CO in the reaction products was
proved by chromatographic analysis.
0
0
.05
0.10
0.15 0.20
, M
The plots of the rate of copper oxidation with I in
DMF as a function of oxidant concentration COx at
constant ligand concentration C and as a function of
C at constant C pass through a maximum (Figs. 1,
), suggesting that the reactants are adsorbed on the
copper surface centers of similar nature. As for the
reaction in DMSO, the shapes of the kinetic curves
V = f(C ) at C = const and V = f(C ) at C =
const (Figs. 1, 2) do not allow unambiguous conclu-
sion on whether the oxidant and ligand are adsorbed
on the active surface centers of similar or different
nature. However, the plots of the reaction rate vs.
oxidant concentration at different (but constant during
the process) ligand concentrations (Fig. 3) unambig-
uously show that in this case also the reactants are
adsorbed on similar reaction centers of the copper
surface.
C
CpFe(CO) Cl
2
Fig. 1. Rate of copper oxidation with CpFe(CO) Cl in
2
L
(
1
1, 3) DMSO (C
14 M) and (2, 4) DMF (C
DMSO DMF
L
Ox
3 M) as a function of the oxidant concentration.
2
Temperature, K: (1, 2) 333 and (3, 4) 323.
1
1
1
0
.5
.0
.5
0
ox
L
L
Ox
4
2
3
4
2
0
4
8
12
16
Thus, in both DMF and DMSO, oxidation of cop-
per with compound I is described by the Langmuir
Hinshelwood scheme [9]:
CL, M
Fig. 2. Rate of copper oxidation with CpFe(CO) Cl as a
2
function of the ligand concentration. Inert solvent
p-xylene; C
0.1 M. Ligand: (1, 2) DMSO and
KOx
CpFe(CO) Cl
2
(
3, 4) DMF. Temperature, K: (1, 3) 333 and (2, 4) 323.
Ox + S
L + S
OxS,
(5)
(6)
(7)
KL
1
0
0
.0
.8
.6
LS,
1
k
OxS + LS
Products.
2
Here, Ox is the oxidant; L, ligand; S, active center
of the metal surface; KOx and K , equilibrium con-
L
stants of adsorption of the oxidant and ligand, respec-
tively.
0
0
.4
.2
0
In accordance with (5) (7), the reaction rate is
described as follows:
2
S [Ox][L]KOxKL
0
V = k
.
(
8)
0
.04 0.08
0.12 0.16
, M
1 + KOx[Ox] + K [L])2
(
L
C
CpFe(CO) Cl
2
2
0
Fig. 3. Oxidation of copper with CpFe(CO) Cl in
Here, k = k S , where k is the rate constant of the
2
DMSO: plot of V/V
vs. oxidant concentration
surface reaction, and S is the number of active cen-
max
0
(
333 K). C
, M: (1) 9 and (2) 14.
ters per unit surface area.
DMSO
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 73 No. 7 2003

OXIDATION OF COPPER WITH DICARBONYLCYCLOPENTADIENYLIRON CHLORIDE
1053
Apparent equilibrium constants, enthalpies, and entropies of adsorption of CpFe(CO) Cl, DMSO, and DMF on the copper
2
surface; rate constants and activation energies of the reactions
Ox
Ox
L
L
k 104,
H
,
1
S
,
H
,
S
,
E ,
a
ads
ads
ads
ads
T, K
KOx
KL
J mol 1 K 1
kJ mol 1
J mol 1 K 1 g cm 2 min 1 kJ mol
1
kJ mol
DMSO
61 9
DMF
70 11
3
3
3
23
33
43
8.2
6.7
4.7
0.10
0.07
0.06
3.0
5.4
9.2
25 4
28 5
20 4
92 8
51 1
51 4
323
333
343
8.4
6.8
4.5
0.55
0.38
0.23
8.0
13.1
24.0
39 4
130 12
The experimental data processed in the coordinates
resistometric method [12] modified to exclude the
access of atmospheric oxygen and moisture to the
reaction mixtures.
1
/2
1/2
(
C /V) = f(C ) at C = const and (C /V)
=
Ox
Ox
L
L
f(C ) at C = const at various temperatures allowed
L
Ox
calculation of the apparent equilibrium constants of
adsorption of the oxidant and ligand on the metal sur-
face, of the enthalpy and entropy of these processes,
and of the apparent rate constants and activation ener-
gies (see table).
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2
3
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0
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stance, was kept for 24 h in DMF. Then the wire was
cleaned to remove the swollen insulating film, im-
mersed in concentrated HNO immediately before the
experiment, washed successively with water and ace-
tone, and dried at reduced pressure. Dicarbonylcyclo-
pentadienyliron chloride was prepared according to
3
[
10]. The compound was 99.6% pure according to
analysis for chlorine and iron [5]; it decomposed at
8.9 C, in agreement with published data [10]. The
8
copper(II) content in the reaction mixture was deter-
mined by the procedure described in [5]. Carbon mon-
oxide was determined chromatographically (Tsvet-106
chromatograph, thermal conductivity detector, 1000
5
-mm glass column, sorbent NaX 4 , column tem-
perature 30 C, detector temperature 50 C, carrier gas
helium, flow rate 40 ml min ). The solvents were
1
purified and dried by common procedures [11] and
degassed before use by repeated freeze pump thaw
cycles. Syntheses of organometallic compounds and
all manipulations with them were performed at re-
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argon. Kinetic measurements were performed by the
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RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 73 No. 7 2003