Synthesis and spectral studies on metal complexes with the neutral O,N,O-tridentate Schiff base 6-amino-5-formyl-1,3-dimethyluracil-benzoylhydrazone: Crystal structure of a bidimensionally hydrogen-bonded perchlorate copper(II) complex

Article abstract of DOI:10.1016/S0277-5387(99)00108-4

From the reaction between different Co(II), Cu(II), Zn(II) and Pd(II) salts and the Schiff base 6-amino-5-formyl-1,3-dimethyluracil-benzoylhydrazone (H₂BEZDO), in ethanol and acetone media, five complexes with M/L stoichiometry 1/1, containing the neutral organic ligand, have been obtained. These compounds have been studied by IR, ¹³C and ¹H-NMR, UV-VIS-NIR and EPR spectroscopies and magnetic measurements. A single crystal X-ray diffraction study has been carried out on the compound [Cu(ClO₄)(H₂BEZDO)(H₂O)]ClO₄. The structure consists of mononuclear cations [Cu(ClO₄)(H₂BEZDO)(H₂O)]⁺ and uncoordinated perchlorate anions. The coordination environment around the Cu(II) may be described as a square-based pyramid in which the Schiff base acts as tridentate ligand through the O(4), N(51) and O(52) atoms, making two five- and six-membered chelate rings. The coordination sphere is completed with the oxygen atom of the water molecule and an oxygen atom of a weakly coordinated perchlorate group occupying the apical position of the polyhedron. Both complex units and uncoordinated perchlorate anions are extensively hydrogen-bonded, forming bidimensional sheets. Elsevier Science Ltd.

Full text of DOI:10.1016/S0277-5387(99)00108-4

Polyhedron 18 (1999) 2205–2210
Synthesis and spectral studies on metal complexes with the neutral O,N,O-
tridentate Schiff base 6-amino-5-formyl-1,3-dimethyluracil-
benzoylhydrazone
Crystal structure of a bidimensionally hydrogen-bonded perchlorate
copper(II) complex
a
a
a ,
*
,
˜
˜
Francisco Hueso-Urena , Antonio L. Penas-Chamorro , Miguel N. Moreno-Carretero
b
c
d
´
´
Jose M. Amigo , Vicente Esteve , Tony Debaerdemaeker
Departamento de Quımica Inorganica y Organica, Universidad de Jaen, 23071 Jaen, Spain
Departamento de Geologıa, Universidad de Valencia, 46100-Burjassot, Valencia, Spain
Departamento de Quımica Inorganica y Organica, Universidad ‘Jaume I’, 12080 Castellon, Spain
a
´
´
´
´
´
b
´
c
´
´
´
´
d
¨
¨
Sektion Rontgen- und Elektronenbeugung, Universitat Ulm, Ulm, Germany
Received 5 February 1999; accepted 15 April 1999
Abstract
From the reaction between different Co(II), Cu(II), Zn(II) and Pd(II) salts and the Schiff base 6-amino-5-formyl-1,3-dimethyluracil-
benzoylhydrazone (H2BEZDO), in ethanol and acetone media, five complexes with M/L stoichiometry 1/1, containing the neutral
1
organic ligand, have been obtained. These compounds have been studied by IR, 13C and H-NMR, UV-VIS-NIR and EPR spectroscopies
and magnetic measurements.
A
single crystal X-ray diffraction study has been carried out on the compound
[Cu(ClO4)(H2BEZDO)(H2O)]ClO4. The structure consists of mononuclear cations [Cu(ClO4)(H2BEZDO)(H2O)]1 and uncoordinated
perchlorate anions. The coordination environment around the Cu(II) may be described as a square-based pyramid in which the Schiff base
acts as tridentate ligand through the O(4), N(51) and O(52) atoms, making two five- and six-membered chelate rings. The coordination
sphere is completed with the oxygen atom of the water molecule and an oxygen atom of a weakly coordinated perchlorate group
occupying the apical position of the polyhedron. Both complex units and uncoordinated perchlorate anions are extensively hydrogen-
bonded, forming bidimensional sheets.
1999 Elsevier Science Ltd. All rights reserved.
Keywords: Crystal structure; Complexes; Schiff bases; Uracil
1. Introduction
and antiviral agents. They usually show an N,N,S coor-
dinating mode. However, there is very little information
available on O,N,O or N,N,O hydrazone compounds in the
literature. Thus, not many papers on benzoylhydrazones
have been published [6–10], in spite of the strong anti-
microbial activity found in some of these compounds [10].
In the ligand used in this study, we have tried to extend
the potentially bidentate coordinating capacity of ben-
zoylhydrazones with another metal binding site (O4 or N6)
supplied by a 6-aminouracil moiety. Moreover, the pres-
ence of the uracil ring may contribute to the resulting
compounds with a structural analogy with the ones present
in biological systems: this fact may be useful to their
potential pharmacologic applications due to the possibility
of the azomethinic bond being hydrolyzed in the acid pH
Biological activity of complexes derived from hy-
drazones has been widely studied and reported, acting in
processes such as antibacterial, antitumoral, antiviral,
antimalarial and antituberculosis effects [1]. With the aim
of participating in this research field, we have synthesized
a new ligand in which we have tried to join the activity of
benzoylhydrazones with that of uracil derivatives.
Many complexes derived from hydrazones, such as
thiosemicarbazones, have been reported [2–5]; compounds
of this type have a great biological activity as antitumoral
*Corresponding author. Tel.: 134-53-212-150; fax: 134-53-212-186.
E-mail address: mmoreno@ujaen.es (M.N. Moreno-Carretero)
0277-5387/99/$ – see front matter
PII: S0277-5387(99)00108-4
1999 Elsevier Science Ltd. All rights reserved.

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F. Hueso-Urena et al. / Polyhedron 18 (1999) 2205–2210
2206
of cancer cells, liberating the uracil derivative, which may
act as either an alkylating agent or an antimetabolite.
the palladium complex is placed in the bottom of the range
cited in the literature for 1:1 compounds [11] and the
values of the [Cu(ClO4)(H2BEZDO)(H2O)]ClO4 and
Zn(NO3)2(H2BEZDO)?1.5H2O complexes are inter-
mediate between the ones expected for 1:1 and 1:2
electrolytes. However, taking into account the single
crystal X-ray diffraction study on the copper perchlorate
complex, there is only one uncoordinated perchlorate ClO42
group, showing that the slightly high conductivity values
are owing to a partial solvolysis of the compounds.
2. Experimental section
2.1. Synthesis
The Schiff base ligand (H2BEZDO) was prepared by
reacting, in EtOH medium containing a few drops of
glacial acetic acid, equimolar amounts of 6-amino-5-
formyl-1,3-dimethyluracil with benzoylhydrazine; the
structure of the ligand is depicted in Fig. 1.
2.2. Crystallographic studies
The synthesis of the complexes was carried out by
mixing equimolar amounts (0.5 mmol) of the ligand and
the corresponding metallic salt in 50 ml of solvent; the
copper(II) complexes were obtained in acetone solutions,
and the remaining were obtained in ethanolic ones. The
resulting solutions were stirred and strongly heated for
several hours; then, in order to make a very slow evapora-
tion of the solvent, the flasks were covered with a plastic
cover containing small holes. Some days later, a small
quantity of crystals of the perchlorate Cu(II) complex were
obtained, which were filtered off, washed with ethanol and
diethylether and air dried. The other complexes were
isolated as powdered material. The analytical data, color
and molar conductivity values (V21 cm2 mol21) were as
follows: CoCl2(H2BEZDO) (1) (green, LM534), found
39.1% C, 3.8% H, 16.3% N, calculated 39.0% C, 3.5% H,
16.2% N; CuCl2(H2BEZDO)?H2O (2) (orange, LM536),
found 37.1% C, 3.4% H, 15.5% N, calculated 37.1% C,
3.8% H, 15.4% N; [Cu(ClO4)(H2BEZDO)(H2O)]ClO4 (3)
(green, LM5116), found 28.9% C, 3.3% H, 12.4% N,
A prismatic green crystal of [Cu(ClO4)(H2BEZDO)-
(H2O)]ClO4 (3) with dimensions 0.3630.1830.18 mm
was mounted in a Stoe Ipds diffractometer (T5293(2) K)
˚
with MoKa radiation (l50.71073 A) monochromatized
with a highly oriented graphite crystal. The unit cell was
determined from 25 random reflections. The intensities
were collected using the v 2 2u scan mode, in the range
1.758,u ,24.058. A total of 14 260 reflections were
measured with 29#h#9, 218#k#18, 218#l#19.
They were averaged to 3511 independent ones (Rint 5
0.0511), 3196 with I . 2s(I) retained for structure solution
and refinement. Data were corrected by Lorentz, polariza-
tion and semiempirically by absorption (c-scans).
2.2.1. Crystal data
C14H17N5O12Cl2Cu,
f.w.5581.77,
orthorhombic,
P212121 space group, unit cell dimensions: a58.2107(8)
3
˚
˚
˚
˚
A, b515.976(2) A, c517.056(2) A, V52237.3(4) A ,
Z54, density(calc)51.727 Mg m23, absorption coefficient
1.286 mm21, F(000)51180.
calculated
28.9%
C,
2.9%
H,
12.0%
N;
Non-H atoms were refined anisotropically by full-matrix
least-squares on F2. H-atoms were idealized and refined
isotropically; the isotropic temperature factors of hydrogen
atoms of methyl and water molecules were fixed to 1.5
times Ueq of the parent atom, whereas for the other
H-atoms, the isotropic temperature factors were fixed to
1.2 times Ueq of the parent atom; O–H distances in the
Zn(NO3)2(H2BEZDO)?1.5H2O (4) (green, LM5136),
found 32.2% C, 3.5% H, 18.7% N, calculated 32.5% C,
3.5% H, 18.9% N; PdCl2(H2BEZDO)?2H2O (5) (yellow,
LM558), found 32.8% C, 3.3% H, 14.0% N, calculated
32.7% C, 3.7% H, 13.6% N. According to the conductivity
values, the CoCl2(H2BEZDO) and CuCl2(H2BEZDO)?
H2O complexes are non-electrolytes, therefore the chloride
ions seem to be coordinated to the metal. The other
complexes have conductivity data attributable to the
presence of two ions; however, the molar conductivity of
˚
water molecule were fixed to 1.10 A. A weighting
scheme
w21 5 s2(F2o) 1 (0.1921P)2 1 0.17P
(P 5
2
2
1
]
3 a[Max(Fo,0) 1 2Fc]) was used and 313 parameters
refined.
Final R indices were R[I . 2s(I)] 5 0.0734 and wR2 5
0.2164. Goodness-of-fit51.075, data-to-parameter ratio
11.2, DF values in the final map comprised between
20.544 and 3.496 eA23. All calculations and drawings
˚
were performed using the Siemens SHELXTL PLUS and
PLUTON 94 systems.
2.3. Apparatus
Microanalyses of C, H and N were performed on a
Fisons EA1108 apparatus. Conductivity measurements
Fig. 1. Structure of ligand H2BEZDO.

˜
F. Hueso-Urena et al. / Polyhedron 18 (1999) 2205–2210
2207
have been carried out using 1023 M freshly prepared
Table 1
˚
Selected bond lengths (A) and angles (8) in the crystal structure of
dimethylformamide solutions on a Hanna HI8820 instru-
ment. Infrared spectra were measured on a Perkin-Elmer
FT-IR 1760-X (KBr pellets, 4000–400 cm21) and FT-IR
Bruker Vector-22 spectrophotometer (polyethylene pellets,
600–220 cm21). The 13C and 1H-NMR spectra of the
Zn(II) compound (DMSO-d6 solution) were recorded on a
Bruker DPX-300 machine. The EPR spectra were obtained
in the X-band at room temperature on a Bruker ESP 300E
apparatus, with a microwave frequency of 9.79 GHz and a
modulation frequency of 100 kHz. Reflectance diffuse
spectra (240–1500 nm) were recorded on a Perkin-Elmer
UV/VIS/NIR Lambda-19 machine using a BaSO4 pellet
as reference. Magnetic measurements (77–290 K) were
carried out on a Manics DSM-8 system.
[Cu(ClO4)(H2BEZDO)(H2O)]ClO4
Around the metal ion
Cu–N(51)
Cu–O(4)
Cu–O(12)
Cu–O(52)
1.924(6)
1.916(6)
2.532(6)
1.965(6)
1.908(6)
90.0(2)
81.97(3)
92.18(3)
82.6(3)
O(12)–Cu–O(52)
O(4)–Cu–O(W)
N(51)–Cu–O(W)
O(12)–Cu–O(W)
O(52)–Cu–O(W)
C(51)–N(51)–Cu
N(52)–N(51)–Cu
C(52)–O(52)–Cu
C(4)–O(4)–Cu
87.20(3)
92.2(3)
177.7(4)
96.78(3)
96.2(3)
130.0(6)
109.1(4)
112.8(5)
128.8(5)
Cu–O(W)
N(51)–Cu–O(4)
N(51)–Cu–O(12)
O(4)–Cu–O(12)
N(51)–Cu–O(52)
O(4)–Cu–O(52)
172.6(2)
In the organic ligand
C(2)–O(2)
C(4)–O(4)
1.18(1)
1.26(1)
1.33(1)
1.25(1)
1.393(9)
1.33(1)
C(52)–O(52)
1.26(1)
125.0(7)
122.3(7)
123.7(7)
117.4(6)
117.9(7)
O(4)–C(4)–C(5)
C(4)–C(5)–C(51)
C(5)–C(51)–N(51)
N(51)–N(52)–C(52)
N(52)–C(52)–O(52)
C(6)–N(6)
C(51)–N(51)
N(51)–N(52)
N(52)–C(52)
3. Results and discussion
3.1. Crystallographic studies
In Fig. 2, a view of the molecular structure of the
complex 3 is depicted. The bond lengths and angles around
the metal centre are given in Table 1. The structure
consists of mononuclear cations [Cu(ClO4)(H2BEZDO)-
(H2O)]1 and uncoordinated perchlorate counterions linked
to the molecular unit through hydrogen bonds.
The metal is coordinated to the O(4), N(51) and O(52)
atoms of the Schiff base, which acts as a tridentate ligand,
making two five- and six-membered chelate rings; the
coordination sphere is completed with the oxygen atom of
the water molecule and an oxygen atom of a weakly
coordinated perchlorate group (Cu–O(12), 2.532(6) A).
˚
The shape of the polyhedron may be best described as a
square-based pyramid, with a distortion parameter D of
0.95 [12,13] and a trigonality index t of 0.09 [14], in
which the O(12) atom of the perchlorate group occupies
the apical position. Furthermore, the ratio between the
apical and equatorial metal–ligand bond lengths (R51.31)
is smaller than the limit cited in the literature [15] to
propose a square-planar geometry around the Cu(II) ion
Fig. 2. Molecular drawing and numbering scheme for the molecular unit of [Cu(ClO4)(H2BEZDO)(H2O)]ClO4.

˜
F. Hueso-Urena et al. / Polyhedron 18 (1999) 2205–2210
2208
(R.1.4). Both chelate rings are close to planarity with
average torsion angles of 1.6 (Cu–O(52)–C(52)–N(52)–
N(51)) and 3.98 (Cu–O(4)–C(4)–C(5)–C(51)–N(51)),
being slightly angled to each other (2.18).
3.2. Spectral and magnetic studies
The comparative study of the infrared spectra of the
complexes and the free ligand is very difficult due to the
great number of bands and only general remarks can be
made. The most interesting features are listed in Table 3.
In Table 3, a general displacement is observed due to the
coordination process, although it is not very pronounced in
some cases since the ligand remains in its non-deproto-
nated form. These shifts agree with the ones found in the
literature in similar compounds [16–20]. In all cases, as it
has been observed in other related complexes, the band
assigned to the n(N–N) mode is shifted to upper
wavenumber, which could be explained because of the
higher electronic delocalization due to the O52 coordina-
tion to the metal.
In the palladium complex the n(C=O) modes appear as
three bands; this fact supports a differentiation of these
groups with each other, since two of them are coordinated
to the metal.
The bands assigned to the nitrate and perchlorate groups
have been clearly detected. In the 600–200 cm21 range the
bands associated to M–N and terminal M–X vibrations
have been assigned, and are in good accordance with the
data found in the literature [21].
In the organic ligand, the substituents of the azomethinic
double bond are in an E conformation, as they are in the
structure of the free ligand, but there is an approximate
1808 turn around the C(5)–C(51) bond, with respect to its
arrangement in the free ligand, due to the involvement in
the coordination of the O(4) atom, which facilitates the
breaking of the initially existent intramolecular hydrogen
bond N(6)–H???N(51). Furthermore, the uracil and phenyl
rings are angled at 11.08 with respect to each other, in
contrast to a value of 38.28 in the free ligand; this
difference is due to the steric requests of the chelates.
Geometric features are similar to the ones found in the free
ligand; so, the uracil and phenyl rings are nearly planar,
with average torsion angles of 2.8 and 2.68, respectively.
Nevertheless, in the coordinated ligand the C(4)–O(4)
˚
distance becomes longer (0.018 A), and the C(2)–O(2)
˚
distance becomes shorter (0.029 A). As in the free ligand,
the C(6)–N(6) bond length is intermediate between the
values for the double and single bond. Likewise, the
˚
distances N(51)–N(52) (1.393 A) and N(52)–C(52)
˚
(1.333 A) suggests that the electronic delocalization in the
The 13C and 1H-NMR spectra of the Zn(II) complex
display the following signals (d, ppm), whose assignments
have been corroborated from both DEPT and HMQC
spectra: 29.1 (C1), 27.7 (C3), 150.2 (C2), 153.7 (C4), 82.9
(C5), 161.1 (C6), 146.4 (C51), 162.2 (C52), 133.1 (C1B),
127.5 (C2B1C6B), 128.5 (C3B1C5B), 131.7 (C4B);
3.16 and 3.34 (hydrogens from N-methyl groups), 8.70
(H51), 8.19 (hydrogens from the 6-amino group), 11.72
(H52), 7.90 (H2B1H6B, doublet), 7.51 (H3B1H5B1
H4B, multiplet). It has not been possible to make this on
the palladium complex due to its low solubility. As
expected, due to the neutral character of the coordinated
H2BEZDO, the spectra of the Zn(II) complex are not
much different to the ones of the free ligand. In the free
H2BEZDO there is an intramolecular H-bond N6–H???
N51 which explains the appearance of two signals for the
hydrogens of the 6-amino group. These two signals do not
appear in the spectrum of the complex because the above
cited intramolecular hydrogen bond is not possible in the
conformation adopted by the ligand, in which the O(4)
atom becomes available to make the O,N,O tridentate
system in the complex; therefore, both H atoms are now
equivalent and appear as a single signal in the spectrum.
The electronic spectrum of CoCl2(H2BEZDO) (1)
chain which joins both rings is nearly the same as in the
uncoordinated ligand.
The geometrical features of the H-bonds are given in
Table 2. In the structure, the hydrogen bonding network is
formed by wavy sheets which are placed parallel to the ac
plane, as observed in Fig. 3. In such sheets, each organic
ligand is bonded to an uncoordinated perchlorate (1 2 x,
1
1
2
]
]
2 2 1 y, 2 z) through two hydrogen bonds between the
N(52)–H???O(24) and N(6)–H???O(22). The hydrogen
atom attached to the N(52) atom bifurcates its hydrogen
bond forming another one with a coordinated perchlorate
group, N(52)–H???O(13) (x 2 1, y, z). Finally, the remain-
ing hydrogen atom of the 6-amino group bonds with
3
1
]
]
another coordinated perchlorate group ( 2 2 x, 2 y, 2 2
1
z). Although it may seem surprising, the water molecules
are not involved in any hydrogen bonding, since there is no
˚
suitable atom at distances shorter than 3 A around the
O(W) atom.
Table 2
Hydrogen bonds in the structure of [Cu(ClO4)(H2BEZDO)(H2O)]ClO4
˚
˚
D–H???A
D???A, A
H???A, A
D–H???A, 8
N(52)–H???O(13)a
N(52)–H???O(24)b
N(6)–H???O(11)c
N(6)–H???O(22)d
2.941
2.949
2.996
2.968
2.446
2.215
2.256
2.202
117
143
144
148
4
4
21
4
4
9
9
9
shows the transitions E9← A2 (9400 cm ), A2(P)← A2
4
4
(15 600 cm21) and E0(P)← A2 (17 500 cm21), belong-
ing to the Co(II) ion in a high spin trigonal bipyramidal
structure [22]. The spectra of Cu(II) complexes show a
broad asymmetric band at 11 600 (2) and 15 400 cm21 (3)
typical of pyramidal square-based structures (411)
[22,23]. The bathochromic displacement of this band
9
a x 2 1, y, z.
b
1
]
2 x 1 1, y 2 2 , 2 z.
c
3
1
]
]
2 x 1 2 , 2 y, z 2 2
.
d
1
1
]
]
2 x 1 1, y 2 2 , 2 z 1 2
.

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F. Hueso-Urena et al. / Polyhedron 18 (1999) 2205–2210
2209
Fig. 3. View of the bidimensional H-bonded sheets in the crystal structure of [Cu(ClO4)(H2BEZDO)(H2O)]ClO4, from the [100] (top) and [010] (bottom)
directions.
Table 3
Selected infrared data (cm21
)
Compound
n(N–H)
n(C=O)
n(N–N)
n(M–N)
n(M–X)
H2BEZDO
3311
3243
3468
3414
3415
3377
3413
3249
3356
3229
3311
3243
1705
1646
1709
1661
1704
927
–
–
CoCl2(H2BEZDO)
972
969
968
975
970
356
369
465
353
451
246
295
–
CuCl2(H2BEZDO)?H2O
a
[Cu(ClO4)(H2BEZDO)(H2O)]ClO4
Zn(NO3)2(H2BEZDO)?1.5H2Ob
PdCl2(H2BEZDO)?2H2O
1703
1714
–
1709
1695
1680
369
a n(Cl–O) of the ClO24 group, 1146, 1115 and 1087 cm21
b n(N–O) of the NO23 group, 1385 cm21
.
.

˜
F. Hueso-Urena et al. / Polyhedron 18 (1999) 2205–2210
2210
observed from the perchlorate to the chlorine complex may
be explained assuming that in the second one, both
chloride ions are coordinated to the metal.
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˜
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1982.
[16] D.X. West, J.S. Ives, J. Krejci, M.M. Salberg, T.L. Zumbahlen, G.A.
The experimental data permits us to suggest that for
complex 1, a distorted trigonal bipyramid with a coordina-
tion sphere CoCl2(O,N,O) exists. In the copper complex 2
the structure may be similar, although due to the similarity
to the perchlorate compound (3), the environment around
the metal may be a distorted square based pyramidal, with
both chloride atoms coordinated to the metal. The zinc
complex acts as a 1:1 electrolyte, it may have a
´
´
´
Bain, A.E. Liberta, J. Valdes-Martınez, S. Hernandez-Ortiz, R.A.
Toscano, Polyhedron 14 (1995) 2189.
[17] D.X. West, R.M. Makeever, G. Ertem, J.P. Scovill, L.K. Pannell,
Trans. Metal Chem. 11 (1986) 131.
[18] D. Kovala-Demertzi, A. Domopoulou, M.A. Demertzis, G. Valle, A.
Papageorgiou, J. Inorg. Biochem. 68 (1997) 147.
[19] D. Lin-Vien, N.B. Colthup, W.G. Fateley, J.G. Grasselli, The
Handbook of Infrared and Raman Characteristic Frequencies of
Organic Molecules, Academic Press, 1991.
[20] G. Socrates, Infrared Characteristic Group Frequencies, Wiley, 1994.
[21] J.R. Ferraro, Low-frequency Vibrations of Inorganic and Coordina-
tion Compounds, Plenum Press, New York, 1971.
[Zn(NO3)(H2BEZDO)]1
or
[Zn(NO3)(H2BEZDO)-
(H2O)]1 cation; we do not have enough data to discern
between them, since both coordination numbers four (Td)
and five (D3h) are usual for Zn(II) ion [27,28]. However,
the virtual planarity of the tridentate O,N,O chelating
system may suggest a TBP structure in which the three
equatorial positions would be occupied by the hydrazone
donor atoms and the apical ones, by a water molecule and
a coordinated nitrate ligand in a similar way to that found
in the [Zn(NO2)(HBEZDO)(H2O)] complex [29]. The
palladium complex may be a square planar, with only a
coordinated chloride atom, [PdCl(O,N,O–H2BEZDO)]Cl?
2H2O.
[22] A.B.P. Lever, Inorganic Electronic Spectroscopy, Elsevier, Am-
sterdam, 1984.
´
[23] D. Sutton, Transition Metal Complexes Electronic Spectra, Reverte,
1975.
[24] R.L. Carlin, Magnetochemistry, Springer-Verlag, Berlin, 1986.
[25] B.J. Hathaway, D.E. Billing, Coord. Chem. Rev. 5 (1970) 143.
[26] J.R. Pilbrow, Transition Ion Electron Paramagnetic Resonance,
Oxford Science Publications, Oxford, 1990.
[27] A. Bino, N. Cohen, Inorg. Chim. Acta 210 (1993) 11.
´
¨
[28] M.C. Rodrıguez-Arguelles, L.P. Battaglia, M.B. Ferrari, G.G. Fava,
Supplementary data
C. Pelizzi, G. Pelosi, J. Chem. Soc., Dalton Trans. (1995) 2297.
˜
˜
[29] F. Hueso-Urena, A.L. Penas-Chamorro, M.N. Moreno-Carretero, M.
Supplementary data are available from the CCDC, 12
Union Road, Cambridge CB2 1EZ, UK on request, quoting
the deposition number CCDC 113469.
´
´
´
Quiros-Olozabal, J.M. Salas-Peregrın, Polyhedron 18 (1999) 351.
Acknowledgements
Thanks are due to DGESIC (MEC, Spain) for financial
support (PB97-0786-C03-03).