Oxidation of cadmium with dicarbonylcyclopentadienyliron chloride in dimethylformamide

Article abstract of DOI:10.1007/s11176-005-0425-5

The kinetic and activation parameters of oxidation of cadmium with dicarbonylcyclopentadienyliron chloride in dimethylformamide were determined. The apparent equilibrium constants, enthalpy, and entropy of adsorption of the reactants on the metal surface

Full text of DOI:10.1007/s11176-005-0425-5

Russian Journal of General Chemistry, Vol. 75, No. 9, 2005, pp. 1351 1353. Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 9, 2005,
pp. 1423 1425.
Original Russian Text Copyright
2005 by Usanov, S. Maslennikov, Spirina, V. Maslennikov.
Oxidation of Cadmium with Dicarbonylcyclopentadienyliron
Chloride in Dimethylformamide
A. A. Usanov, S. V. Maslennikov, I. V. Spirina, and V. P. Maslennikov
Research Institute of Chemistry, Lobachevskii Nizhny Novgorod State University, Nizhny Novgorod, Russia
Received June 24, 2004
Abstract The kinetic and activation parameters of oxidation of cadmium with dicarbonylcyclopentadi-
enyliron chloride in dimethylformamide were determined. The apparent equilibrium constants, enthalpy, and
entropy of adsorption of the reactants on the metal surface were evaluated. The reaction scheme was suggested.
In [1] we reported on the synthesis of an organo-
metallic compound with a Mg Fe bond by oxidation
of Mg with dicarbonylcyclopentadienyliron chloride
(C /V)1 = f(C ) at C = const allowed calculation
/2
L
L
Ox
of the apparent equilibrium constants of adsorption of
I and DMF and the reaction rate constants:
(
I). In this study we examined the kinetics and
products of the reaction of I with Cd.
T, K
278
14.59
288
7.11
293
5.55
ads
K
Ox
The dependences of the reaction rate on the content
of I and dimethylformamide (DMF, used as solvent)
in the reaction mixture are shown in Figs. 1 and 2.
The curves shown in Figs. 1 and 2 do not allow un-
ambiguous conclusion on whether the adsorption cen-
ters on the metal surface are similar or different in
nature. Therefore, we studied the dependences of the
reaction rate on the concentration of I at different
fixed concentrations of DMF in the reaction mixture
ads
K
0.25
1.17
0.19
4.65
0.16
5.70
L
k 10 , g cm min 1
2
2
From the temperature dependences of these quan-
tities, we determined the apparent enthalpy and entro-
py of adsorption of the reactants on the metal surface:
ads
1
ads
Ox
1
1
H
H
52 4 kJ mol ,
21 2 kJ mol ,
S
164 12 J mol K ,
99 9 J mol K ,
Ox
ads
L
1
ads
L
1
1
S
1
and activation energy of the process E 75 5 kJ mol .
The latter value is indicative of the kinetic control of
the reaction [3].
(
Fig. 3). The results, in line with the concept pre-
sented in [2], suggest that both compound I and DMF
are adsorbed on reaction centers of similar nature
on the Cd surface. In this case, the reaction course
can be described by the scheme
In accordance with [4], the electronegativity of the
Cp(CO) Fe fragment is appreciably lower than that of
2
ads
K
Cp(CO) Mo. This may be one of the factors responsi-
ble for the 140 times higher rate constant of oxida-
tion of Cd with I in DMF at 293 K, compared to that
3
Ox
Ox + S
OxS,
(1)
ads
L
K
of the reaction of Cp(CO) MoCl with Cd under iden-
(
(
2)
3)
3
L + S
LS,
tical conditions [5].
k
OxS +LS
Products.
After completion of the oxidation of Cd with
The expression for the reaction rate is as follows:
a solution of I (C 0.15 M) in THF at 20 C, the
0
brown liquid phase was separated from the unchanged
metal and light-colored precipitate. The amount of
converted Cd was 0.85 mol per mole of consumed
I. The precipitate was washed with diethyl ether and
dried under reduced pressure. According to the anal-
ysis for Cd and Cl (1 : 2), the precipitate was CdCl2.
Its yield was 20.6% based on consumed I. The
liquid phase was evaporated, and the residue was
treated with diethyl ether to obtain a red solution and
a yellow precipitate, which were separated. The solid
phase insoluble in ether was (dicarbonylcyclopentadi-
ads ads
k K
K
COxCL
ads
Ox
L
V =
.
(
4)
ads
2
(
1 + K COx + K C )
L
Ox
L
2
where k = k(S ) , k is the rate constant, S is the
0
0
number of active centers on unit surface area of the
ads
ads
metal, and KOx and KL are the equilibrium constants
of adsorption of the oxidant and ligand, respectively.
Treatment of the experimental data in the coordi-
1
/2
nates (C /V)
= f(C ) at CL = const and
Ox
Ox
1
070-3632/05/7509-1351 2005 Pleiades Publishing, Inc.

1352
USANOV et al.
enyliron)cadmium chloride, as indicated by the results
of its analysis: Fe : Cd : Cl = 1.00 : 1.05 : 1.11. The
6
5
4
1
yield of CpFe(CO) CdCl was 53.6% based on I. Cer-
2
tain excess of Cd and Cl corresponds to the presence
2
of a CdCl impurity (2.6% based on I).
2
3
2
1
0
Thus, the first step of the oxidation of Cd with I
is reaction (5):
3
Cd + Cp(CO) FeCl
Cp(CO) FeCdCl.
(5)
2
2
0.05
0.10
0.15
0.20
COx, M
The ether was partially evaporated under reduced
pressure, and pentane was added in small portions to
the residue cooled to 5 C. In so doing, a violet crys-
talline substance precipitated; it was washed with cold
pentane and dried under reduced pressure. The prod-
uct was identified as bis(dicarbonylcyclopentadienyl-
iron) (II) by the decomposition point (194 C) and
analysis for Fe. Found, %: Fe 31.0. Calculated, %:
Fe 31.5. Published data [6]: decomposition point
Fig. 1. Rate of oxidation of Cd with dicarbonylcyclo-
pentadienyliron chloride in DMF toluene (C 3 M)
as a function of the oxidant concentration. Temperature,
DMF
K: (1) 293, (2) 288, and (3) 278.
3
2
.0
.5
1
95 C. The yield of II was 14.0% based on I.
1
It is known [7] that, in oxidation of Cu with I in
2
DMF, the (dicarbonylcyclopentadienyliron)copper
chloride formed in the first step reacts with I to form
complex II. Similar reaction occurs in the case of Cd:
2
1
1
.0
.0
.5
3
Cp(CO) FeCdCl + Cp(CO) FeCl
2
2
0
.5
0
[Cp(CO) Fe]2 + CdCl2.
(6)
2
According to [8], polynuclear organometallic hal-
ides can occur in the Schlenk equilibrium with the
corresponding symmetrical species:
5
10
15
CDMF, M
Fig. 2. Rate of the reaction of dicarbonylcyclopentadi-
enyliron chloride with Cd as a function of DMF
2Cp(CO)2FeCdCl
[Cp(CO)2Fe]2Cd + CdCl2. (7)
concentration. Inert diluent toluene (C
0.05 M).
Ox
Temperature, K: (1) 293, (2) 288, and (3) 278 K.
However, in the products of cadmium oxidation
with I, bis(dicarbonylcyclopentadienyliron)cadmium
was not detected even in trace amounts. This fact
indicates that equilibrium (7) is strongly shifted to the
left. This conclusion is consistent with the results of
our experiments [5] on oxidation of cadmium with
tricarbonylcyclopentadienylmolybdenum chloride.
1
.0
.8
.6
.4
1
0
2
0
EXPERIMENTAL
0
Cadmium [TU (Technical Specifications) 6-09-
3
095 78] in the form of turnings and 0.5-mm wire
0
.2
0
was used without additional surface treatment. Dicar-
bonylcyclopentadienyliron chloride was prepared
according to [6]. The main substance content in the
product, according to the results of the analysis for
Cl and Fe [9], was no less than 99%; decomposition
point 89 C (published data [6]: decomposition point
88 89 C). Analysis for cadmium was performed
according to [9]. Organic solvents were purified by
0.05
0.10
0.15
COx, M
Fig. 3. Relative rate of oxidation of Cd in DMF toluene
as a function of the concentration of I at 278 K. DMF
concentration, M: (1) 3 and (2) 9.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 75 No. 9 2005

OXIDATION OF CADMIUM WITH DICARBONYLCYCLOPENTADIENYLIRON CHLORIDE
1353
standard procedures [10]. All manipulations with
organometallic compounds and their solutions were
performed under reduced pressure or in an Ar atmos-
phere. The reaction kinetics was monitored resistomet-
rically with an installation modified for experiments
with readily oxidizable and readily hydrolyzable sub-
stances [11].
Maslennikov, V.P., and Artemov, A.N., Zh. Obshch.
Khim., 2001, vol. 71, no. 5, p. 714.
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7
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Barium), Moscow: Akad. Nauk SSSR, 1963, p. 50.
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