Synthesis of bis(η5-cyclopentadienyldicarbonyliron)stannane dichloride by direct oxidation of tin and reaction of this compound and its analogs with magnesium

Article abstract of DOI:10.1023/B:RUGC.0000045872.42657.fd

A procedure was developed for preparing [Cp(CO)₂Fe] ₂SnCl₂ by direct oxidation of tin with η⁵-cyclopentadienyldicarbonyliron chloride in polar solvents. The reaction kinetics was studied, and its scheme was suggested. Products of the reaction of magnesium with compounds R₂SnCl₂ [R = Cp(CO)₃Mo, Cp(CO)₃W, Cp(CO)₂Fe] were identified. The reaction mechanism was discussed.

Full text of DOI:10.1023/B:RUGC.0000045872.42657.fd

Russian Journal of General Chemistry, Vol. 74, No. 7, 2004, pp. 1101 1104. Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 7, 2004,
pp. 1191 1194.
Original Russian Text Copyright
2004 by S. Maslennikov, Tsarev, Spirina, Lado, V. Maslennikov, Usanov.
5
Synthesis of Bis( -cyclopentadienyldicarbonyliron)stannane
Dichloride by Direct Oxidation of Tin and Reaction
of This Compound and Its Analogs with Magnesium
S. V. Maslennikov, M. V. Tsarev, I. V. Spirina,
A. V. Lado, V. P. Maslennikov, and A. A. Usanov
Research Institute of Chemistry, Lobachevsky Nizhni Novgorod State University, Nizhni Novgorod, Russia
Received July 4, 2002
Abstract A procedure was developed for preparing [Cp(CO)2Fe]2SnCl2 by direct oxidation of tin with
5-cyclopentadienyldicarbonyliron chloride in polar solvents. The reaction kinetics was studied, and its
scheme was suggested. Products of the reaction of magnesium with compounds R2SnCl2 [R = Cp(CO)3Mo,
Cp(CO)3W, Cp(CO)2Fe] were identified. The reaction mechanism was discussed.
ox
In [1], we reported on preparation of compounds
[Cp(CO)3M]2SnCl2 (M = Mo, W) in high yield by
oxidation of tin with Cp(CO)3MCl in polar solvents.
In this work, using Cp(CO)2FeCl (I) as oxidant, we
prepared by a similar procedure [Cp(CO)2Fe]2SnCl2
(II). As solvents we used DMF, DMSO, and THF.
Here K and KLads are the equilibrium constants
ads
of adsorption of the oxidant and ligand, respectively,
on the solid phase surface. For a process following
scheme (1) (3), the kinetic equation has the form
Ox
K
[Ox]KLads[L]
ads
V = k
.
(4)
Ox
(1 + K [Ox] + KLads[L])2
Gentle heating (313 K) of a solution of I (C0
0.15 M) for 20 h under stirring (120 rpm) with a ten-
fold (relative to the oxidant) excess of tin chips gives
[Cp(CO)2Fe]2SnCl2. Its yield per 2 mol of the oxidant
was 0.89, 0.70, and 0.49 mol of the crude product in
DMF, DMSO, and THF, respectively. After twofold
recrystallization of the products from benzene heptane
(1 : 2 by volume), we obtained yellow-orange needle-
shaped crystals with mp 167.95 C; according to [2],
the melting point of II is 168 C. Found, %: Cl 16.72;
Fe 26.48; Sn 28.14. C14H10Cl2Fe2O4Sn. Calculated,
%: Cl 16.79; Fe 26.44; Sn 28.10. The IR spectrum of
ads
Here k = kS20; S0 is the number of active centers
per unit surface area.
Treatment of the experimental data in the co-
ordinates (Cox/V)1/2 = f(Cox) at CL = const and
(Cox/V)1/2 = f(CL) at COx = const, followed by com-
bined solution of the equations obtained, allowed cal-
culation of the apparent rate constants of the process
and equilibrium constant of adsorption of the reactants
on the metal surface; from the temperature depen-
dences of these quantities, we calculated the apparent
activation energy of the reaction and the enthalpy
and entropy of adsorption of the oxidant and ligand
(Table 1).
1
II (absorption bands at 2027, 2002, 1978, 1958 cm )
virtually coincides with the IR spectrum (2026, 2000,
1
1975, 1956 cm ) of the sample of [Cp(CO)2Fe]2SnCl2
prepared from [Cp(CO)2Fe]2 and SnCl2 [3].
Figure 1 shows that the curve of the reaction rate
vs. oxidant concentration consists of two ascending
portions separated by an inflection. This may be due
to formation of the reaction product by different
possible pathways. At the initial concentrations of I
lower than 0.25 M, the intermediate Cp(CO)2FeSnCl
passes into solution, where it reacts with the second
oxidant molecule:
The kinetics of tin oxidation with I was studied in
DMF and its mixtures with p-xylene. The kinetic
curves (Figs. 1, 2) show that, at the initial oxidant
concentration C0 0.25 M, the reaction can be de-
scribed by the Langmuir Hinshelwood scheme for the
case of adsorption of reactants on similar active cen-
ters of the metal surface [4]:
Ox
K
Cp(CO)2FeSnCl + Cp(CO)2FeCl
ads
Ox + S
L + S
Ox S,
L S,
(1)
(2)
(3)
K Lads
k
[Cp(CO)2Fe]2SnCl2.
(5)
An increase in the rate of the heterogeneous reac-
tion with an increase in the initial oxidant concentra-
Ox S + L S
Products.
1070-3632/04/7407-1101 2004 MAIK Nauka/Interperiodica

1102
MASLENNIKOV et al.
5
4
3
2
1
2
4
3
2
1
0
3
1
2
3
1
0
2
4
6
8
10 12 14
cDMF, M
0.1
0.2
0.3
0.4 0.5
[Cp(CO)2FeCl], M
Fig. 1. Rate of tin oxidation with Cp(CO) FeCl in DMF
Fig. 2. Rate of tin oxidation in the system Cp(CO) FeCl
2
2
0
as a function of the oxidant concentration. C
DMF
DMF p-xylene. Initial Cp(CO) FeCl concentration
2
12.9 M. Temperature, K: (1) 333, (2) 323, and (3) 313.
0.2 M. Temperature, K: (1) 333, (2) 323, and (3) 313.
tion, after all the active centers of the surface are
filled, is due to the bimolecular process involving
attack of an active center with an adsorbed molecule
of I by a similar molecule from the bulk of solution:
by a single kinetic equation throughout the oxidant
concentration range studied.
In accordance with [7], the Cp(CO)2Fe fragment is
appreciably less electronegative than the Cp(CO)3Mo
fragment. This fact, apparently, explains why the rate
constant of tin oxidation with I in DMF at 323 K is
by a factor of 150 higher compared to the tin oxida-
tion with Cp(CO)3MoCl under the same conditions.
The curve of the rate of the tin oxidation vs. initial
concentration of 5-cyclopentadienyltricarbonylmo-
lybdenum does not contain the second ascending por-
tion which should be observed at the oxidant concen-
tration exceeding 0.5 M [1].
Cp(CO)2Fe Cl
Cp(CO)2FeCl +
///// Sn /////
(6)
[Cp(CO)2Fe]2SnCl2.
A similar pattern was observed in oxidation of
magnesium with halogenated hydrocarbons in mix-
tures of benzene with diethyl ether [5] and in reaction
of magnesium with triphenylchlorostannane in THF
[6]. The following fact, however, should be taken into
account. In the reactions studied in [5, 6], the oxidant
and ligand are adsorbed on active centers differing in
nature. In these systems, the ligand molecules cannot
significantly compete with the oxidant molecules for
the active centers of the metal surface even if the
adsorption occurred on similar centers, since the ad-
sorption constants of ethers are very low. In the sys-
tem Sn Cp(CO)2FeCl DMF the pattern is quite dif-
ferent: The reactant molecules are adsorbed on the
similar centers, and the ligand molecules significantly
compete with the oxidant molecules. This fact does
not allow description of the kinetic curves in Fig. 1
Reduction of dichlorides of dialkyl and diaryl tin
derivatives is a route to cyclic and linear oligomeric
stannylenes [8]. Further oxidation of these compounds
yields effective catalysts for polyurethane synthesis
[9].
To assess the suitability of compounds R2SnCl2
[R = Cp(CO)3Mo (III), Cp(CO)3W (IV), Cp(CO)2Fe]
as starting compounds for such processes, we studied
their reduction with magnesium in THF.
A solution of R2SnCl2 (C0 0.15 M) in THF was
kept over magnesium turnings, taken in a tenfold ex-
Table 1. Apparent rate constants and activation energy of the reaction of Cp(CO)2FeCl with DMF and the equilibrium
constants, enthalpies, and entropies of adsorption of the reactants
Ox
Ox
H
,
1
S
,
ads
HLads
,
1
SLads
J mol 1 K
,
1
k 103,
g cm 2 min
E,
Ox
T, K
K
ads
KLads
ads
1
1
1
kJ mol
J mol 1 K
kJ mol
kJ mol
313
323
333
15.5
12.6
12.0
0.92
0.37
0.26
11 4
13 6
21 6
73 17
0.92
1.29
1.43
28 4
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 74 No. 7 2004

SYNTHESIS OF BIS( 5-CYCLOPENTADIENYLDICARBONYLIRON)STANNANE DICHLORIDE
1103
Table 2. Products of magnesium oxidation with R2SnCl2 (C0 0.15 M) in THF at 293 K
Yield, mole per mole of oxidant
Oxidant R2SnCl2
Sn
Cp(CO)nMMgCla
[Cp(CO)nM]2Mga
MgCl2
[Cp(CO)2Fe]2SnCl2
[Cp(CO)3Mo]2SnCl2
[Cp(CO)3W]2SnCl2
0.98
0.97
0.98
1.67
1.88
1.93
0.15
0.04
0.03
0.14
0.05
0.03
a
n = 2, M = Fe; n = 3, M = Mo, W.
cess relative to the oxidant and preactivated with
dibromoethane at 323 K, for 48 h under stirring with
a magnetic stirrer at 120 rpm. In the process, the
mixture changed color from yellow to dark brown,
and a black precipitate of tin and a white precipitate
very poorly soluble in THF formed.
RCl + Mg
RMgCl,
R2Mg + MgCl2.
(11)
(12)
2RMgCl
EXPERIMENTAL
Magnesium wire (0.5 mm in diameter) and magne-
sium turnings [MCh-1, GOST (State Standard) 804
86] containing 99.92% main substance were used
without additional treatment. [Cp(CO)3Mo]2SnCl2
and [Cp(CO)3W]2SnCl2 were prepared as described in
[1]. Cp(CO)2FeCl was prepared according to [13].
The main substance content in these compound, as
determined by analysis for Mo, W, Fe, Sn, and Cl,
was no less than 99.5% [14]. The physicochemical
constants of the compounds were consistent with
published data.
The weight loss of magnesium after the reaction
completion was 1.98 mol per mole of the starting
oxidant. The amount of tin precipitated by the end of
the reaction virtually corresponded to its content in
the starting mixture (0.98 mol per mole of R2SnCl2).
The yield of the white precipitate per mole of the
starting oxidant depends on the structure of the or-
ganometallic fragment bound to tin and decreases in
the order Cp(CO)2Fe > Cp(CO)3Mo > Cp(CO)3W.
The ratio of manesium and transition metal (Fe,
Mo, W) in the white precipitate is 1 : 2, suggesting its
formula R2Mg. This assumption is confirmed by the
following facts. The precipitates gradually dissolve
on contact with a concentrated solution of MgCl2 in
THF; they are readily soluble in pyridine. The prod-
ucts containing Fe, Mo, and W melt with decomposi-
tion at 423, 433, and 458 K, respectively, which is
consistent with the data given for R2Mg in [10, 11].
The yields of products of magnesium oxidation with
II IV are listed in Table 2.
The solvents were purified and dried by standard
procedures [15]. Syntheses of the organometallic
compounds and manipulations with them were per-
formed in an atmosphere of dry oxygen-free Ar or in
a vacuum. Liquid mixtures were degassed by repeated
freeze pump thaw cycles.
The reaction kinetics was studied by a resistometric
procedure [16] modified for experiments with readily
oxidizable and hydrolyzable compounds.
REFERENCES
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mation of compounds containing an Sn M group
(M = Mg) in oxidation of Mg with dibenzyltin dichlo-
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reaction of Mg with R2SnCl2:
1. Piskunov, A.V., Maslennikov, S.V., Spirina, I.V.,
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R2SnCl2 + Mg
R2Sn(Cl) MgCl
R2Sn(Cl) MgCl,
(7)
(8)
(9)
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RSnCl + RMgCl,
RSnMgCl
Sn + RCl.
Sn + RMgCl,
RSnCl
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(10)
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RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 74 No. 7 2004

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