Reaction of vanadocene and vanadocene dichloride with ortho-iodobenzoic acid

Article abstract of DOI:10.1134/S1070363213020114

At the interaction of bis (η⁵-cyclopentadienyl)vanadium with iodobenzoic acid or trimethylsilyl o-iodobenzoate in toluene depending on the ratio of the initial reagents bis(η⁵-cyclopentadienyl)vanadium(o- iodobenzoate) or η⁵

Full text of DOI:10.1134/S1070363213020114

ISSN 1070-3632, Russian Journal of General Chemistry, 2013, Vol. 83, No. 2, pp. 299–302. © Pleiades Publishing, Ltd., 2013.
Original Russian Text © A.S. Gordetsov, S.V. Zimina, V.F. Ur’yash, E.M. Moseeva, 2013, published in Zhurnal Obshchei Khimii, 2013, Vol. 83, No. 2,
pp. 245–248.
Reaction of Vanadocene and Vanadocene Dichloride
with ortho-Iodobenzoic Acid
A. S. Gordetsov, S. V. Zimina, V. F. Ur’yash, and E. M. Moseeva
Nizhny Novgorod State Medical Academy, pl. Minina i Pozharskogo 10/1, Nizhny Novgorod, 603005 Russia
e-mail: Chem@gma.nnov.ru
Received December 13, 2011
Abstract―At the interaction of bis (η5-cyclopentadienyl)vanadium with iodobenzoic acid or trimethylsilyl o-
iodobenzoate in toluene depending on the ratio of the initial reagents bis(η5-cyclopentadienyl)vanadium(o-
iodobenzoate) or η5-cyclopentadienylvanadium-bis-o-iodobenzoate were obtained in high yields. The latter was
also formed in the reaction of bis(η5-cyclopentadiene)vanadium dihloride with trimethylsilyl o-iodobenzoate.
DOI: 10.1134/S1070363213020114
The reaction of vanadocene (Cp2V) with carboxylic
acids is known to afford depending on the ratio of
initial reagents mono- or dicarboxylate derivatives of
the type Cp2VOCOR and CpV(OCOR)2 [1–3]. It was
also found that vanadocene was able to break covalent
bonds between carbon and halogens [4]. It was
therefore appropriate to examine the reaction of vanado-
cene with compounds containing both a carboxy group
and an active carbon–halogen bond, especially because
as a result new biologically active organovanadium
complexes like the Cp2VCl2 could be obtained [5].
Thus, in the reaction of Cp2V with o-iodobenzoic
acid (evacuated sealed ampule, toluene, room
temperature, 60–72 h) at a ratio of initial reagents 2:1
and 1:1 o-iodo-bis(η5- cyclopentadienyl)vanadium-
benzoate (I) was obtained in the form of fine black-
violet crystals with the yield up to 70% (Scheme 1). In
the study of compound I by IR spectroscopy and
differential thermal analysis (DTA) we found that it
dimerizes in the reaction process to afford compound
Id (Scheme 1). As a by-product hydrogen is produced
(proved by GLC).
Scheme 1.
C6H4I
O
C
O
O
O
O
O
Cp
Cp
Cp
Cp
Cp
Cp
IH C
IH4C6
Cp2V +
C
C
V
V
4
6
V
−1/2R2
OR
O
C
C6H4I
Ie
I
R = H, Me3Si.
In the reaction of vanadocene with a specially
in the same ratio and conditions iodobenzoate I was also
synthesized trimethylsilyl o-iodobenzoate (II) (Scheme 2)
obtained, and in solution hexamethyldisilane was detected.
Scheme 2.
+ (Me3Si)2NH
O
O
IH C
C
2
+ NH3
IH C
C
2
4
6
4
6
OSiMe3
OH
299

300
GORDETSOV et al.
The iodobenzoate II has not been previously
tion of more rigid conditions (toluene, 100°C, 48–60 h)
led to the formation of η5-cyclo-pentadienylvanadium
bis(o-iodobenzoate) III as black-violet fine crystalline
powder as the main reaction product (yield up to 59%).
In the reaction mixtures were also found cyclopenta-
diene and hydrogen or hexamethyldisilane, respectively.
obtained as an individual substance but was only
mentioned in one publication as an intermediate in the
synthesis of aromatic polyamides [6].
The change in the ratio of o-iodobenzoic acid (or
iodobenzoate II) and vanadocene to 2:1 and the applica-
Scheme 3.
O
C
O
C
O
Cp2V + 2 IH4C6
C
IH4C6
O
C6H4I
V
O
−CpH, −R2
OR
Cp
III
R = H, Me3Si.
Using vanadocene dichloride (Cp2VCl2) instead of
the vanadocene in the reaction with organosilicon
iodobenzoate II also resulted in the bisiodobenzoate
III obtained in the form of greenish-black crystals
(reagents ratio 2:1, toluene, 100°C, 48–60 h, yield of
41% .) The ESR method revealed a small admixture of
the original Cp2VCl2. From the reaction solution
cyclopentadiene and trimethylchlorosilane were
isolated.
pound III, 3050, 1590, 1080, 800, 705 (C6H5), 1630
(νas OCO), 1410 (νs OCO), 3005, 1005, 830 (cyclo-
pentadienyl), 580 (iodine–carbon bond) [7]; compound
II, 3050, 1580, 1450, 1090, 760, 730 (C6H5), 1700 (νas
OCO), 1420 (νs OCO), 2940, 2890, 1250, 860 (Me3Si),
605 (iodine–carbon).
As show the IR spectral data of compound Id, the
band νas of free carbonyl group is absent, which may
be explained by the formation of the dimeric structure
with the C=O groups well coordinated with vanadium
(Scheme 4). However, the difference between
asymmetric and symmetric vibrations of the ester
group OCO of compound (III) is 215 cm–1, which
confirms the presence of the dimeric bridge structure
IIId by analogy with the organovanadium salicylate
and carboxytriazine derivatives [3, 8, 9].
Thus, in contrast to the data [4], vanadocene did not
react with the iodine–carbon bonds, obviously owing
to the electronic influence of the benzene aromatic
ring. This is confirmed by the failure at the attempted
reaction of vanadocene with iodobenzene (toluene,
100°C, 48–60 h), which did not result in Cp2VI2 or
Cp2VI. Instead a dark green complex compound
formed readily soluble in toluene that decomposed to
the initial reagents at the attempt to isolate. It should
also be noted that the iodine–carbon bond in the
studied compounds is inert with respect to
hexamethyldisilazane (e.g., see Scheme 2).
Phase transitions of the synthesized compounds Id
and III were studied by the differential thermal
analysis (DTA) in the temperature range from –50 to
350°C. In all thermograms 1–3 in the range 0–50°C
there are glass-like transition of G-type [10, 11]. For
samples obtained at a ratio of 2:1 of the starting
materials (thermograms 2 and 3) about 120°C a
significant heat evolution begins with a maximum at
168–174°C, which apparently corresponds to the
transition of the intermediate structure IV in the
structure III in the crystalline state (Scheme 4). The
transition ends at about 190°C. Almost immediately
begins the second exothermic transition with a
maximum at 254–255°C, corresponding to the
transition of structure III to IIId. The thermograms of
both samples are similar, indicating identity of the
crystal structures of the products of synthesis at the
specified ratio of the starting materials.
Hydrolysis of the reaction mixtures 1–3 leads to the
formation of the initial o-iodobenzoic acid as the main
product. We failed to detect the presence of any
paramagnetic vanadium compounds (except for the
residual original vanadocene complexes) by ESR,
which indirectly confirms the proposed structure of the
products I–III.
IR spectra of the newly acquired iodobenzoates
contain the following main absorption bands, cm–1:
compound Id, 3060, 1550, 1070, 795, 710 (C6H5),
1510 (νas OCO), 1405 (νs OCO), 3020, 1010, 820
(cyclopentadienyl), 590 (iodine–carbon bond); com-
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REACTION OF VANADOCENE AND VANADOCENE DICHLORIDE
301
Scheme 4.
Cp
O
C
O
C
C6H4I
III
V
O
O
I
Ie
IH4C6
−Cp2V
−CpH
Cp
IV
IH4C6
C6H4I
O
Cp
V
C
C
O
O
O
O
O
C
V
C
Cp
C6H4I
O
IH4C6
O
IIIe
The thermogram (see the figure) shows the results
of DTA for the sample obtained at 1:1 ratio of
precursors (compound I). There is an exothermic
transition with a maximum at 155°C, which can be
attributed to the conversion of Id to IV, accompanied
by the release of a significant amount of Cp2V (mp
168°C). In connection with this, the exothermic
transition of structure IV in the structure III is shifted
to higher temperatures with a maximum at 206°C. The
transition of structure III to IIId occurs at 261°C,
which corresponds to a similar transition in the
thermograms 2 and 3. Slight exothermic transition
(with maximum at 151°C) in the thermogram 2,
apparently, is also associated with the presence in the
compound III of a small admixture of the compound
Id, which is absolutely excluded in the synthesis of
compound III from Cp2VCl2 (thermogram 3).
katharometer 120°C, of evaporator 150°C. All
chemical operations with organovanadium compounds
were carried out in a vacuum. DTA was performed in
the range 50–350°C on an installation whose
construction and method of work were described in
[12]. The thermal chamber was filled with helium,
quartz was used as a reference. A sample and the
reference of ~0.35 g weight were placed in sealed
Thus, the DTA data also confirm the proposed
scheme of interconversions.
EXPERIMENTAL
IR spectra were registered on spectrophotometers
Specord IR-75 and Specord M-80 from a thin layer of
a substance in mineral oil or without it between KBr or
ZnSe plates. The ESR spectra were recorded on a
Bruker EMX instrument with diphenylpicrylhydrazyl
(DPPH, gi = 2.0037) as a reference substance for
determining g-factor. Chromatographic studies were
performed on a Tsvet-69A gas chromatograph with
katharometer. The conditions: stationary phase Chro-
maton N-AW, mobile phase Reoplex-400, column
length 2 m. The temperature of the oven 70°C, of
Δt
t, °C
Thermograms of the compounds: (1) Id, (2) III,
synthesized from o-iodobenzoic acid and Cp2V, (3) III,
synthesized from the compound II and Cp2VCl2.
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GORDETSOV et al.
evacuated glass crucibles. The sample temperature and
the temperature difference between the sample and the
H 2.15; V 8.35. In the filtrate hexamethyldisilane and
CpH were identified by GLC (yields up to 70%).
reference was measured with
a
chromel-copel
b. Similarly, from 0.70 g of Cp2VCl2 and 1.80 g of
o-iodobenzoate II (1:2 ratio) under the same
conditions were isolated 0.70 g (41%) of η5-cyclo-
pentadienylvanadium bis-o-iodobenzoate III as black-
green fine crystalline powder. Found, %: C 37.84, H
2.50; V 8.60. C19H13I2O4V. Calculated, %: C 37.41, H
2.15; V 8.35. In the filtrate Me3SiCl and CpH were
identified by GLC.
thermocouple, error 0.5°C. The sample in the thermal
chamber was cooled with liquid nitrogen to –190°C,
and then heated at a rate of 5°C min–1. The deviation
from linearity did not exceed 1%. To test the DTA
installation, melting temperature of the reference n-
heptane and the glass transition temperature of the
purified glycerol were determined. The results
obtained agree with the literature data for n-heptane
[13] and glycerol [14] with an accuracy of 0.2°C and
1°C, respectively.
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Synthesis of trimethylsilyl o-iodobenzoate (II). A
mixture of 12.0 g of o-iodobenzoic acid and 8.0 g of
hexamethyldisilazane (ratio of reagents 2:1) was
refluxed in the presence of a catalyst (NH4)2SO4 for
11 h till the ammonia release ceased. From the
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Synthesis of bis(η5-cyclopentadienyl)vanadim o-
iodobenzoate (I). a. A mixture of 0.8 g of Cp2V and
1.0 g of o-iodobenzoic acid (reagent ratio 1:1) in 30 ml
of toluene was kept for 60 h in a sealed evacuated
ampule at room temperature. The formed precipitate of
black-violet color was washed with solvent, filtered
off, and dried in a vacuum. We obtained 1.16 g (70%)
of bis(η5-cyclopentadienyl)vanadium o-iodobenzoate
I. Found, %: C 47.98, H 3.50; I 29.14; V 12.30.
C17H14IO2V. Calculated, %: C 47.69, H 3.30; I 29.64;
V 11.90. In the filtrate by GLC was determined
cyclopentadiene (yield 80%).
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b. Similarly, from a mixture of 1.8 g of Cp2V and
0.95 g of iodobenzoate II (2:1 ratio) was isolated
0.77 g (69%) of bis(η5-cyclopentadienyl)vanadium o-
iodobenzoate I. In the filtrate hexamethyldisilane was
determined by GLC.
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iodobenzoate (III). a. A mixture of 0.67 g of Cp2V
and 1.84 g of iodobenzoate II (the ratio of reagents
1:2) in 30 ml of toluene was kept for 100 h in an
evacuated sealed ampule at room temperature. The
precipitate of black-violet color was washed with
solvent, filtered off, and dried in a vacuum. We
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obtained 1.32
g
(59%) of η5-cyclopentadienyl-
vanadium bis-o-iodobenzoate III. Found, %: C 37.93,
14. Ur’yash, V.F., Mochalov, A.N., Yushin, A.S., and
H 2.61; V 8.10. C19H13I2 O4V. Calculated, %: C 37.41,
Bochkova, G.B., Termodin. Org. Soed., 1989, p. 55.
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