Monoperoxo-vanadium(V) complexes of R,S-N-(carboxymethyl)-aspartate

Article abstract of DOI:10.1016/S0020-1693(03)00366-9

Monoperoxo complexes of vanadium(V), M₂[VO(O₂) cmaa(H₂O)] (M=K⁺, NH₄⁺) and M[VO(O₂)Hcmaa(H₂O)] (M=K⁺, Cs⁺, NBu₄⁺), where cm

Full text of DOI:10.1016/S0020-1693(03)00366-9

Inorganica Chimica Acta 355 (2003) 223Á228
/
www.elsevier.com/locate/ica
Monoperoxo-vanadium(V) complexes of R,S-N-(carboxymethyl)-
aspartate
a b,
Marian Casny´ , Michal Siva´k *, Dieter Rehder
a
ˇ
a Institute of Inorganic and Applied Chemistry, University of Hamburg, 20146 Hamburg, Germany
b Department of Inorganic Chemistry, Faculty of Natural Sciences, Comenius University, 842 15 Bratislava, Slovakia
Received 9 March 2003; accepted 24 May 2003
Abstract
Monoperoxo complexes of vanadium(V), M2[VO(O2)cmaa(H2O)] (Mꢀ
/
Kꢁ, NH4ꢁ) and M[VO(O2)Hcmaa(H2O)] (MꢀKꢁ
,
/
Csꢁ, NBu4ꢁ), where cmaa and Hcmaa are anions of (R,S)-N-(carboxymethyl)aspartic acid, H3cmaa, were prepared. Based on IR
spectra and thermal decomposition characteristics, the heteroligand is proposed to be bound via nitrogen and two carboxylic
oxygens, and the water molecule to be coordinated to vanadium. The 51V NMR spectra of aqueous solutions of dissolved complexes
at different pH values are consistent with the presence of the exo- and endo-forms, with chemical shifts at about ꢂ
/
590 and ꢂ600
/
ppm. Predominantly, the less stable endo-form partially decomposes as the pH is varied. No pH influence on chemical shifts of the
diastereomers was observed.
# 2003 Elsevier B.V. All rights reserved.
Keywords: Monoperoxo-vanadates(V); Diastereomers; 51V NMR spectra; R,S-N-(carboxymethyl)aspartic acid
1. Introduction
h2-peroxo ligand, two non-protein oxygens and the
nitrogen of a o-proximal histidine [5]. Thus, oxo- and
oxo-peroxo complexes of vanadium with amino acid
derivatives containing an OxN donor set provide useful
models for the enzyme in which, apart the distal
histidines His411 and His418, also the active site
aspartate Asp278 acts as potential mediator for proton
transfer [5,12]. Recent studies of the concomitant
complexation of vanadium(V) by hydrogen peroxide
and biogenic heteroligands such as a-hydroxycarboxylic
acids have shown that these studies are also of interest in
view of stereochemical features of the complexes [13].
Finally, the interaction of vanadium(V) with biologi-
cally relevant ligands in the presence or absence of
hydrogen peroxide has also been addressed in the
context of the insulin-mimetic potential of vanadium
compounds [14].
The isolation of vanadium containing haloperoxi-
dases [1,2], the structural characterization by XAS of the
enzyme from the alga Ascophyllum nodosum [3] and by
X-ray diffraction of both the native and peroxo forms of
the enzyme from the fungus Curvularia inaequalis [4,5],
have initiated extensive studies of the interaction of
vanadium with biologically relevant ligands such as
glycine [6],
L-histidine [7] and its N-carboxymethyl
derivative [8], alkoxides [9], or the dipeptides glycylgly-
cine and glycyltyrosine [10,11] both in solution and in
the solid state. Typically, either oxo-, dioxo- or oxo-
peroxo complexes have been isolated from such reaction
systems. The latter are investigated with respect to their
character as structural and functional models for the
peroxo form of the enzyme, in which the active site is a
monoperoxo complex with penta-coordinated vana-
In previous studies, we have synthesized and structu-
rally characterized the monoperoxo complexes of vana-
dium(V) with the achiral tetradentate glycine-derived
ligands nta, ada and ceida, providing an O3N (N, O1,
dium(V) in a tetragonalÁpyramidal array, bonded to a
/
* Corresponding author. Tel.: ꢁ
60296-273.
/
421-2-60296-349; fax: ꢁ421-2-
/
O2, O3) donor set [15Á
18] (Chart 1).
/
Here, we present results on the reaction between
vanadium(V), peroxide and the chiral N-(carboxy-
ˇ
E-mail addresses: mail@casny.de (M. Casny´), sivak@fns.uniba.sk
(M. Siva´k).
0020-1693/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved.
doi:10.1016/S0020-1693(03)00366-9

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224
M. Casny´ et al. / Inorganica Chimica Acta 355 (2003) 223Á228
/
K2Hcmaa ×
H3cmaa in KOH. KVO3 was prepared and crystallized
from a solution of V2O5 in KOH at pH Â8. The
/
2H2O was isolated from a solution of
/
following chemicals were obtained from commercial
sources: NH4VO3 (Loba Chemie), 10% NBu4OH
(Merck), CsCl (Lachema Brno), 30% H2O2 (Slavus
Slovakia).
The IR spectra in nujol mulls were measured on a FT
IR Nicolet Magna 750 spectrophotometer. pH values
were determined on a Titrator TTT 2 (Radiometer
Copenhagen). The UVÁVis spectra were recorded on a
/
Hewlett Packard 8452 spectrophotometer. The thermal
analysis was performed on a Derivatopraph Q 1500 D
(MOM, Budapest) with the following conditions: sam-
ple weight 100 mg, heating rate 1.25 8C minꢂ1, self-
generated atmosphere. For NMR measurements, a
Varian V-300 NMR spectrometer was used. The 51V
NMR spectra were recorded for 0.01 M aqueous
solutions at 78.879 MHz and 293 or 278 K, using
VOCl3 as external standard, and a capillary with D2O
coaxially immersed in rotating 5 mm diameter NMR
vial. The spectra were recorded approximately 10 min
after dissolution of the complex. The deconvolution of
the 51V NMR spectra was performed by the use of V
NMR 6.1 B program. Elemental analyses (CHN) were
carried out on a Carlo Erba 1106 analyser, vanadium by
titration with FeSO4 and diphenylamine as indicator.
Potassium and cesium contents were determined grav-
imetrically as tetraphenylborates. Peroxidic oxygen was
determinated by iodometry. Due to the disturbing effect
of vanadium, the iodine was extracted into chloroform
before being titrated with thiosulphate.
Chart 1.
methyl)aspartatic acid, carried out in the systems
MVO3ÁH2O2ÁH3cmaa ÁH2O (Mꢀ
Kꢁ, NH4ꢁ) and
V2O5ÁH2O2ÁH3cmaa ÁH2OÁCsCl/NBu4OH.
/
/
/
/
/
/
/
/
The Cambridge database does not contain any crystal
structure of a complex with the cmaa ligand. The
synthesis of the cis-N and trans-N isomers of mixed
ligand Co(III) complexes containing (S)-H3cmaa and
glycine or leucine was described [19]; in these com-
pounds, the aspartate derivative was proposed to be
bound as a tetradentate cmaa(3ꢂ
)-N, O1, O2, O3
ligand. This mode of cmaa coordination was quite
recently confirmed by a crystal structure determination
of [Co(cmaa)(en)] [20].
/
2. Experimental section
2.1. Chemicals and apparatus
2.2. Syntheses
Racemic N-(carboxymethyl)aspartic acid was synthe-
sized from maleic acid and glycine according to Ref. [21]
Prior to elemental analyses, the filtered-off products
were washed with small amounts of cooled ethanol
Table 1
Characteristic IR vibrations in cmꢂ1 of vanadium(V) monoperoxo-cmaa complexes
Assignment
Complex
1
2
3
4
5
n(Vꢀ
/
Op)
575 m
916 vs
944 m
958 s
564 s
573 m
930 s
962 s
570 m
925 s
959 s
581 m
914 s
959 s
n(Opꢀ
/Op)
920 vs
944 m
960 s
n(Vꢁ
/
O)
981 m
1143 w
n(Cꢀ
/
Ncoord
)
1128 w
1145 w
1120 w
1136 w
1108 w
1120 w
1262 m
1394 vs
1108 w
1130 w
1269 m
1378 vs
1410 sh
1630 vs,b
n(COOH)
ns(COO)
1255 m
1367 vs
1393 vs
1670 vs,b
1384 vs
1402 vs
1587 vs
1623 vs
1666 vs
1406 vs
nas(COO)
1576 vs
1622 vs
1653 s,sh
1635 vs,b
d(H2O)
n(COOH)
1705 s
1712 s
1720 s,sh

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M. Casny´ et al. / Inorganica Chimica Acta 355 (2003) 223Á
/228
225
Fig. 1. Structures of isomers of monoperoxovanadium-cmaa complexes. R is the pendent CH2COO(H) group bonded to the chiral carbon, for O3 cf.
the numbering in Chart 1.
(5 8C) and dried in dessicator above silica gel in
refrigerator.
H3cmaa (0.96 g, 5 mmol) in 15 ml of 25% aqueous
ammonia. The pH was then adjusted by 2 M HClO4 to
4.4. To the resulting red solution, pre-cooled ethanol
was added dropwise until the solution remained turbid.
2.2.1. K2[VO(O2)cmaa(H2O)] (1)
2 crystallized within 24 h as an orangeÁred, micro-
/
In a solution of KVO3 (0.69 g, 5 mmol) in 20 ml of
water and 0.75 ml of 30% H2O2, solid H3cmaa (0.96 g, 5
mmol) was slowly dissolved. The pH of the red solution
crystalline product. Anal. Calc. for C6H16N3O10V (Mꢀ
/
341.1 g molꢂ1): C, 21.11; H, 4.73; N, 12,31; O22ꢂ, 9.38;
V, 14.94. Found: C, 20.95; H, 4.66; N, 12.19; O22ꢂ, 9.56;
V, 14.40%.
thus formed was adjusted by KOH (cꢀ/2 M) to the
optimum value 4.0Á4.1. The solution was then diluted
/
with water to 30 ml and left to stay in a closed vessel at
5 8C. After 24 h, ethanol was added dropwise until
formation of a stable turbidity. From this solution, 1
precipitated within several hours as an orange micro-
crystalline product. Anal. Calc. for C6H8K2NO10V
2.2.3. K[VO(O2)Hcmaa(H2O)] (3)
The reaction solution was prepared as for 1, but the
pH was adjusted with 1 M HClO4 to 2.5. Crystallization
was initiated with ethanol. Anal. Calc. for
(Mꢀ
/
383.21 g molꢂ1): C, 18.78; H, 2.10; K, 20.41; N,
C6H9NO10KV (Mꢀ
361.13 g molꢂ1): C, 19.94; H,
2.51; N, 3.88;V, 14.11. Found: C, 19.79; H, 2.81; N,
3.58; V, 13.85%.
/
3.65; O22ꢂ, 8.35; V, 13.29. Found: C, 18.73; H, 1.92; K,
20.71; N, 3.54; O22ꢂ, 8.50; V, 12.96%.
2.2.2. (NH4)2[VO(O2)cmaa(H2O)] (2)
2.2.4. Cs[VO(O2)Hcmaa(H2O)] (4)
NH4VO3 (0.59 g, 5 mmol) was dissolved under
cooling in an ice bath in 0.6 ml of 30% H2O2 and 5 ml
of water. This solution was added to a solution of
V2O5 (0.18 g, 1 mmol) was dissolved in 5 ml of water
and 1.5 ml of 30% H2O2 under cooling in an ice bath. To
the red solution formed, solid H3cmaa (0.38 g, 2 mmol)

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M. Casny´ et al. / Inorganica Chimica Acta 355 (2003) 223Á
/228
Fig. 2. pH dependence of the percentage of the species present in aqueous solutions of 1 (cꢀ
/
0.01 M), as revealed by an evaluation of the 51V NMR
spectra at 293 K. MPV and DPV are mono- and diperoxovanadate, V1-cmaaꢀ
/
[VO2cmaa]2ꢂ
.
was added. The resulting solution was mixed with a
solution of CsCl (0.34 g, 2 mmol) in 10 ml of water. The
pH was adjusted with 10% CsOH to 2.8. The solution
was kept for 24 h in the refrigerator, and ethanol was
then added to initiate the crystallization. Anal. Calc. for
All our attempts to obtain a monocrystal of any of the
complexes prepared, using different reaction conditions
and methods of crystallization, failed. If not isolated in
the form of a microcrystalline product, they form
bundles of very thin, irregular needle-like crystals.
The assignment of characteristic vibrations in the IR
spectra (Table 1) was based on a comparison of the
C6H9CsNO10V (Mꢀ
438.94 g molꢂ1): C, 16.40; H, 2.07;
Cs, 30.29; N, 3.19; V, 11.61. Found: C, 16.20; H, 2.28;
Cs, 30.48; N, 2.94; V, 11.35%.
/
spectra of 1Á
in the case of 5, also with the spectrum of [NBu4]Br [23].
The IR spectra of 1Á5 exhibit bands corresponding to
stretching vibrations of the VꢀOp, OpꢀOp (Opꢀperoxo
oxygen) and VꢁO bonds, all in the regions characteristic
of vanadium(V) monoperoxo complexes [15Á18,24]. The
shift of the n(Cꢀ
N) vibrations from 1183 cmꢂ1 for
K2Hcmaa ×2H2O to 1108Á
1145 cmꢂ1 for the complexes
indicates coordination of the cmaa or Hcmaa ligand via
/
5 with that of K2[Hcmaa ×/2H2O] [22] and,
2.2.5. NBu4[VO(O2)Hcmaa(H2O)] (5)
/
V2O5 (0.36 g, 2 mmol) was dissolved in a 10% solution
of NBu4OH (2.6 ml, 4 mmol). The solution was diluted
with 10 ml of water, and solid H3cmaa (0.76 g, 4 mmol)
was added. After dissolution of the ligand, 0.6 ml of 30%
H2O2 was added. The pH of the solution was 2.7.
Within 3 days, yellow microcrystalline 5 formed. Anal.
/
/
/
/
/
/
/
/
Calc. for C22H46N2O10V (Mꢀ
548.37 g molꢂ1): C,
/
nitrogen [25]. In the spectra of 3Á5, the bands of
/
48.14; H, 8.27; N, 5.11; O22ꢂ, 5.83; V, 9.29. Found: C,
48.44; H, 8.17; N, 4.88; O22ꢂ, 5.50; V, 9.47%.
Repeated CHN analyses and IR spectra confirmed
that 1, 2 and 5 are stable for at least 6 months when kept
at 5 8C.
n(COOH) at 1712, 1705 and 1720 cmꢂ1, which are
Table 2
Time dependence of the relative integral intensities and W1/2 of I and II
at 278 K and pH 3
Time (min)
W1/2, Iint
I, ꢂ596 ppm
3. Results and discussion
/
II, ꢂ602 ppm
/
3.1. Characterization of the solids
8
32
266 Hz, 39.1%
345 Hz, 27.5%
376 Hz, 31.6%
392 Hz, 35%
360 Hz, 32%
350 Hz, 40.9%
330 Hz, 72.5%
333 Hz, 68.4%
321 Hz, 65%
338 Hz, 68%
76
The compounds were obtained at pH 4.5 as cmma (1,
2), or at pH approximately 2.6 as Hcmaa complexes (3Á
5). They contain one formula unit of water throughout.
125
200
/

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M. Casny´ et al. / Inorganica Chimica Acta 355 (2003) 223Á
/228
227
about as strong as the corresponding band at 1705 cmꢂ1
oxygens observed in other heteroligand complexes [18].
The weight loss (17.5%) exceeds that of water plus
peroxide (13%), suggesting that, besides of a release of
water and the peroxo group, partial heteroligand
decomposition simultaneously occurs.
in K2Hcmaa ×
/
2H2O, and the bands at 1262, 1269 and
1255 cmꢂ1 prove the presence of at least one protonated
carboxylate which is most probably free from coordina-
tion in the protonated complexes 3Á5. In contrast, the
/
spectra of 1 and 2 indicate that all three carboxylic acid
groups are deprotonated. In crystal structures of vana-
3.2. Solution properties
dium(V) monoperoxo complexes, both coordinated [15Á
/
18] and uncoordinated COOꢂ groups [26] have been
found. Recently, the first structure of a vanadium(V)
monoperoxo complex with the carboxylic acid function
coordinated through the doubly bonded oxygen has
The different protonation degrees of the carboxy-
methylaspartatic acid in compounds 1 and 2 (cmaa) as
compared to 3Á
metric titration. While the pH of aqueous solutions of 1
(cꢀ
10ꢂ3 M) was 5.7, and titration with NaOH caused
/
5 (Hcmaa) were proven also by alkali-
been reported [27]. The Dꢀ
for 1Á5 correspond to a monodentate coordination of
the carboxylates [28].
/
nas(COO)ꢂ/ns(COO) values
/
/
only a linear increase of pH, the pH of a solution of 5
with the same concentration was 2.8, i.e. 5 behaves as a
In all known crystal structures of mononuclear
cationic, anionic or neutral monoperoxo-vanadium(V)
complexes with heteroligands containing ON, ON2,
O2N, O2N2, O3N or NN donor sets, the vanadium
center is in a distorted pentagonal bipyramidal environ-
ment of donor atoms (Chart 1). The most probable
coordination mode of the Hcmaa ligand is via nitrogen
and two carboxylic oxygens occupying, together with
the two peroxo oxygens, the equatorial positions of the
pentagonal plane, thus forming two five-membered
chelate rings, a structural motif which has been reported
for complexes with iminodiacetate [29] and its N-
carbamoylmethyl- [17] and N-carbamoylethyl deriva-
tives thereof [18]. One of the axial positions is occupied
by the doubly bonded oxygen. The water ligand is
tentatively placed into the second axial position (also see
medium strong acid (pKaꢀ5.7). The titration curve
exhibited an equivalent point corresponding to the
neutralization of one proton in Hcmaa.
/
The UVÁ
band (Lꢀ
O22ꢂ) with a maximum at 423 nm (oꢀ
cmꢂ1) which is within the characteristic region 415Á
nm observed for heteroligand monoperoxo-vana-
dium(V) complexes. UVÁVis spectra for the in situ
formation of the monoperoxo-cmaa complex in the
KVO3ÁH2O2ÁH3cmaa ÁH2O system in the pH range 1Á
5 [c(V)ꢀ0.01 M, V:H3cmaaꢀ1:2, c(H2O2)ꢀ0.05 M]
/
Vis spectrum of 1 in water shows a LMCT
363 M
460
/
/
/
/
/
/
/
/
/
/
/
showed that the maximum concentration of the mono-
peroxo-cmaa complex is around pH 3.5. This observa-
tion is in agreement with 51V NMR measurements
which, moreover, allowed to identify the nature of the
monoperoxo-cmaa complexes in solution and the spe-
cies formed on their decomposition.
below), cf. AÁD in Fig. 1. The coordination of a chiral
/
carboxymethylaspartate will result in structures with
chiral centers on carbon, nitrogen and vanadium. The
Unlike the aqueous solutions of many heteroligand
monoperoxo complexes of vanadium(V), which exhibit
only one 51V NMR resonance in a relatively wide pH
mutual orientation of Vꢁ
/
O
and pending
ꢀ
/
CH2COO3(H) group decides whether the structure
represents the exo- or the endo-form. For the completely
deprotonated ligand, a tetradentate coordination is also
feasible. In this case, there are eight possible stereo-
range, [17,18,24,30Á
eous solutions of 1, 2 and also 5 at 293 K show, in the
pH range 1.1Á7.5, a two-component pattern, I and II,
with chemical shifts of ꢂ592(1) and ꢂ599(2) ppm
(W1/2 150, resp. 220 Hz) The chemical shifts are pH-
/
32] the 51V NMR spectra of aqu-
/
/
/
isomers, EÁ
eomeric pairs of enantiomers (EÁ
The thermal analysis of 1 showed that, in the
temperature interval of 20Á160 8C, no decomposition
/
L in Fig. 1, which represent four diaster-
Â
/
/
F; GÁH; IÁJ; KÁL).
/
/
/
independent, i.e. protonation/deprotonation of the car-
boxymethylaspartate ligand does not affect the shielding
of the 51V nucleus, nor is any significant change in
structures caused by variations in pH.
/
process occur. This is indicative of the absence of water
of crystallization. In all crystallohydrates of potassium
salts of heteroligand monoperoxo complexes of vana-
dium(V) we have studied so far, the crystal water was
released by an endothermic process at temperatures
below 150 8C, while corresponding anhydrous peroxo
complexes were formed [18]. The water molecule, which
Such a two-component system within a narrow 10
ppm range was described as characteristic for the
existence of diastereomers based on enantiomerism
[7,33]. The signal to lower magnetic field (I) was
observed to be less intense and possibly corresponds to
the exo form, while the more intense signal at higher
field (II) is assigned the endo form. Over the whole pH
range investigated, the exo form I is more stable than
the endo form II. Depending on the pH, decomposition
to a series of peroxo and non-peroxo vanadium(V)
species is observed. In the range of co-existence of the
diastereomers I and II, their intensity ratio is approxi-
is present in all of the complexes 1Á
counter cation, thus it is coordinated directly to
vanadium (structures AÁD, Fig. 1). The first thermal
/5, independent of the
/
decomposition process for 1 is an exothermic effect with
a maximum at 202 8C and terminated at 214 8C. This
temperature corresponds to the release of the peroxo

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M. Casny´ et al. / Inorganica Chimica Acta 355 (2003) 223Á228
/
[2] E.G.M. Vollenbrock, L.H. Simons, J.W.P van Schijndeln, P.
Barnett, M. Balzar, H.L. Dekker, C. van de Linden, R. Wever,
Biochem. Soc. Trans. 23 (1995) 267.
mately 1:3. In strongly acidic as well as in neutral media,
partial decomposition occurs, and the ratio I:II increases
to 1:2. The amount of I (23Á32%) varies only slightly;
/
[3] J.M. Arber, E. de Boer, C.D. Garner, S.S. Hasnain, R. Wever,
Biochemistry 28 (1989) 7968.
the decomposition products are formed preferentially
from II.
In the 51V NMR spectrum of 1 in water in the pH
[4] A. Messerschmidt, R. Wever, Proc. Natl. Acad. Sci. USA:
Biochem. 93 (1996) 392.
[5] A. Messerschmidt, L. Prade, R. Wever, Biol. Chem. 378 (1997)
309.
range 5.4Á7.5, the predominant monoperoxo-cmaa
/
species I and II partially decompose to a monomeric
peroxo-free vanadate [VO2cmaa]2ꢂ (V1-cmaa) with d at
[6] M. Bhattacharjee, S. Ganguly, J. Mukherjee, J. Chem. Res. (S) 2
(1995) 80.
[7] V. Vergopoulos, W. Priebsch, M. Fritzsche, D. Rehder, Inorg.
Chem. 32 (1993) 1844.
about ꢂ
/
542 to ꢂ
/
548 ppm, and aqua-diperoxovana-
date [VO(O2)2H2O]ꢂ (DPV), dꢀ
/
ꢂ/690 ppm, Eq. (1):
[8] K. Kanamori, K. Nishida, N. Miyata, Ken-ichi-Okamoto, Chem.
Lett. (1998) 1267.
3[VO(O2)cmaa]2ꢂ ꢁOHꢂ ꢁH2O 0[VO(O2)2H2O]ꢂ
ꢁ2[VO2cmaa]2ꢂ ꢁHcmaa2ꢂ ꢁ(1=2)O2
[9] D.C. Crans, F. Jiang, J. Chen, O.P. Anderson, M.M. Miller,
Inorg. Chem. 36 (1997) 1038.
(1)
[10] F.W.B. Einstein, R.J. Batchelor, S.J. Angus-Dunne, A.S. Tracey,
Inorg. Chem. 35 (1996) 1680.
As suggested by the counter-running curves for II and
V1-cmaa in Fig. 2, [VO2cmaa]2ꢂ forms, in the pH range
[11] D.C. Crans, H. Holst, A.D. Keramidas, D. Rehder, Inorg. Chem.
34 (1995) 2524.
3.8Á
the pH range 2Á
present in solution which, on acidification (pH 1.1Á
partially decompose to form the aqua-monoperoxova-
nadium species [VO(O2)(H2O)y]ꢀ with dꢀ
539 ppm,
Eq. (2):
/
5, at the expense of the less stable endo form II. In
3.7, only the diastereomers I and II are
1.7)
[12] M. Weyand, H.-J. Hecht, M. Kiess, M.-F. Liaud, H. Vilter, D.
Schomburg, J. Mol. Biol. 293 (1999) 595.
ˇ
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Biochem. 80 (2000) 59.
/
/
/
ꢂ
/
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Quian Sun, R. Bruck, E. Gershonov, D.C. Crans, Y. Goldwasser,
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[VO(O2)cmaa]2ꢂ ꢁxHꢁ ꢁyH2O 0[VO(O2)(H2O)y]ꢁ
ꢁHxcmaa(3ꢂx)ꢂ
Symposium Series 711, Washington DC (1998) 308Á315.;
/
(b) D. Rehder, J. CostaPessoa, C.F.G.C. Geraldes, T. Kabanos,
T. Kiss, B. Meier, G. Micera, L. Pettersson, M. Rangel, A.
Salifoglou, I. Turel, D. Wang, J. Biol. Inorg. Chem. 7 (2002) 384.
[15] M. Siva´k, D. Joniakova´, P. Schwendt, Trans. Met. Chem. 18
(1993) 304.
(2)
The 51V NMR spectra of 1 registered at 278 K and pH
3 (Table 2) revealed a slight shift of d(51V) for I (ꢂ
5900 596 ppm) and II (ꢂ6000 602 ppm) and a
/
/
ꢂ
/
/
/
ꢂ
/
[16] L. Kuchta, M. Siva´k, F. Pavelcˇ´ık, J. Chem. Res. (S) (1993) 393.
[17] M. Siva´k, J. Tyrsˇelova´, F. Pavelcˇ´ık, J. Marek, Polyhedron 15
(1996) 1057.
broadening of both signals by more than 110 Hz when
compared with 293 K. The decreased temperature did
not lead to an improved resolution and confirmation of
the existence of isomers (Fig. 1). While the intensity
ratio is 1:3 at 293 K and in the pH range giving rise to a
two component (I and II) spectrum, this ratio is 1:1 at
273 K shortly after dissolving the complex in water, and
then changes to 1:2 within an hour remaining constant
therafter.
[18] M. Siva´k, V. Sucha´, L. Kuchta, J. Marek, Polyhedron 18 (1998)
93.
[19] (a) G. Colomb, K. Bernauer, Helv. Chim. Acta 60 (1977) 459;
(b) G. Colomb, K. Bernauer, Helv. Chim. Acta 60 (1977) 468.
[20] F. Pavelcˇ´ık, J. Maderova´, J. Marek, unpublished results.
[21] R.V. Snyder, R.J. Angelici, J. Inorg. Nucl. Chem. 35 (1973) 523.
[22] IR spectrum of K2Hcmaa ×
517 m, 550 s, 613 s, 638 m, 758 m, 775 s, 855 w, 870 w, 918 w, 950
w, 996Á1075 b, 1183 vs, 1228 vs, 1255 vs, 1294 vs, 1350Á1380 b,
1503 vs, 1585 vs, 1625 vs, 1705 s.
/
2H2O in nujol, in cmꢂ1: 453 m, 472 s,
/
/
Efforts to support these findings based on 51V NMR
by running 13C NMR spectra were counter-acted by the
instability of the systems. At pH 3 and 277 K,
[23] IR spectrum of NBu4Br in nujol, in cmꢂ1: 725 sh, 737 s, 880 m,
900 vs, 920 vs, 994 m, 1034m, 1057 m, 1111 m, 1240 w.
[24] G.J. Colpas, B.J. Hamstra, J.W. Kampf, V.L. Pecoraro, J. Am.
Chem. Soc. 118 (1996) 3469.
decomposition became effective after 2.5Á3 h.
/
[25] D.T. Sawyer, J.M. Mc Kinnie, J. Am. Chem. Soc. 82 (1960) 4191.
[26] P. Schwendt, M. Siva´k, A.E. Lapshin, Y.I. Smolin, Y.F. Shepelev,
D. Gyepesova´, Trans. Met. Chem. 19 (1994) 34.
Acknowledgements
ˇ
[27] M. .Casny´, D. Rehder, Chem. Commun. (2001) 921.
[28] K. Nakamoto, Infrared and Raman Spectra of Inorganic and
Coordination Compounds, fifth ed., Willey, New York, 1997.
[29] C. Djordjevic, S.A. Craig, E. Sinn, Inorg. Chem. 24 (1985) 1281.
[30] F.W.B. Einstein, K.J. Batchelor, S.J. Angus-Dunne, A.S. Tracey,
Inorg. Chem. 35 (1996) 1680.
This research was financially supported by Ministry
of Education of the Slovak Republic (Grant 1/5227/98).
We thank Dr. Pavelcik for the synthesis of carboxy-
methylaspartic acid.
[31] M. Kosugi, Sh. Hikichi, M. Akita, Y. Moro-oka, J. Chem. Soc.,
Dalton Trans. 2 (1999) 1369.
[32] V. Conte, F. Di Furia, S. Moro, J. Mol. Catal. A, Chem. 104
(1995) 159.
References
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