Solution and solid study of Zn(II) and Cd(II) complexes with N-(6-amino-3,4-dihydro-3-methyl- 5-nitroso-4-oxo-pyrimidin-2-yl)-glycine as ligand. Crystal structures of [ZnL2(H2O)4]·6H2O and {[Cd(μ-L)Cl(H2O)2]·H2O}(n)

Article abstract of DOI:10.1016/S0020-1693(00)00070-0

Reactions of N-(4-amino-1,6-dihydro-1-methyl-5-nitroso-6-oxo-pyrimidin-2-yl)glycine with Zn(II) and Cd(II) (1:1 and 1:4 metal/ligand ratios, in aqueous media at 35 °C and 0.1 M KCl ionic strength) were studied by potentiometric methods. This study has revealed a similar qualitative behaviour to that found by us for this family of N-pyrimidine aminoacids, the primary coordination site being either the pyrimidine or the carboxylate group depending on whether the ligand acts in neutral form or deprotonated, respectively. In solid state two complexes were obtained by working in 1:1 metal-to-ligand ratio: [Zn(L)₂(H₂O)₄]·6H₂O and {[Cd(μ-L)Cl(H₂O)₂]·H₂O}(n), which were characterised by IR and NMR spectroscopies, TG and DSC techniques and single crystal X-ray diffraction. The former complex is mononuclear with the Zn(II) ion hexacoordinated in a distorted octahedral geometry. The coordination sphere is formed by four water molecules and two ligands coordinating in a monodentate fashion through the carboxylate group. The Cd(II) complex consists of a 1D infinite chain, with the metal ion heptacoordinated in a distorted pentagonal bipyramid. The ligand bridges the metal ions coordinating in a bis-didentate fashion through the pyrimidine and the carboxylate group. The nature of these complexes is very different to that shown by the Zn(II) and Cd(II) complexes with the related methionine derivative, which is attributed to he effect of the R substituent on the aminoacid moiety. (C) 2000 Elsevier Science S.A.

Full text of DOI:10.1016/S0020-1693(00)00070-0

www.elsevier.nl/locate/ica
Inorganica Chimica Acta 304 (2000) 137–143
Note
Solution and solid study of Zn(II) and Cd(II) complexes with
N-(6-amino-3,4-dihydro-3-methyl-5-nitroso-4-oxo-pyrimidin-2-yl)-
glycine as ligand. Crystal structures of [ZnL2(H2O)4]·6H2O and
{[Cd(m-L)Cl(H2O)2]·H2O}n
P. Arranz-Mascaro´s a, R. Lo´pez-Garzo´n* a,1, M.D. Gutierrez-Valero a,
M.L. Godino-Salido a, J.M. Moreno* b,2
a Departamento de Qu´ımica Inorga´nica y Orga´nica, Facultad de Ciencias Experimentales, Uni6ersidad de Jae´n, 23071-Jae´n, Spain
b Departamento de Qu´ımica Inorga´nica, Facultad de Ciencias, Uni6ersidad de Granada, 18071-Granada, Spain
Received 15 September 1999; accepted 21 January 2000
Abstract
Reactions of N-(4-amino-1,6-dihydro-1-methyl-5-nitroso-6-oxo-pyrimidin-2-yl)glycine with Zn(II) and Cd(II) (1:1 and 1:4
metal/ligand ratios, in aqueous media at 35°C and 0.1 M KCl ionic strength) were studied by potentiometric methods. This study
has revealed a similar qualitative behaviour to that found by us for this family of N-pyrimidine aminoacids, the primary
coordination site being either the pyrimidine or the carboxylate group depending on whether the ligand acts in neutral form or
deprotonated, respectively. In solid state two complexes were obtained by working in 1:1 metal-to-ligand ratio:
[Zn(L)2(H2O)4]·6H2O and {[Cd(m-L)Cl(H2O)2]·H2O}n, which were characterised by IR and NMR spectroscopies, TG and DSC
techniques and single crystal X-ray diffraction. The former complex is mononuclear with the Zn(II) ion hexacoordinated in a
distorted octahedral geometry. The coordination sphere is formed by four water molecules and two ligands coordinating in a
monodentate fashion through the carboxylate group. The Cd(II) complex consists of a 1D infinite chain, with the metal ion
heptacoordinated in a distorted pentagonal bipyramid. The ligand bridges the metal ions coordinating in a bis-didentate fashion
through the pyrimidine and the carboxylate group. The nature of these complexes is very different to that shown by the Zn(II)
and Cd(II) complexes with the related methionine derivative, which is attributed to he effect of the R substituent on the aminoacid
moiety. © 2000 Elsevier Science S.A. All rights reserved.
Keywords: Crystal structures; Zinc complexes; Cadmium complexes; Amino acid complexes
and have been extensively studied. In this line we are
working with a new family of ligands containing both
fragments (Scheme 1), by which could be described as
N-substituted a-amino acids as well as pyrimidine
derivatives. The synergic effect of both moieties makes
of this kind of compounds a versatile ligands showing
different coordination patterns, which can be tuned to
give rise metal complexes ranging from mononuclear to
1D, 2D and 3D polynuclear. The coordination modes
of N-substituted a-aminoacids depend on the nature of
1. Introduction
It is well known that both pyrimidine bases and
a-aminoacids act as ligands toward metal ions. Actu-
ally, metal complexes of these ligands are of interest
1 *Corresponding author. Tel.: +39-9-5824 3322; fax: +34-9-5824
8526.
2 *Corresponding author. Tel.: +39-9-5824 3322; fax: +34-9-5824
8526; e-mail: jmoreno@ugr.es
0020-1693/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0020-1693(00)00070-0

138
P. Arranz-Mascaro´s et al. / Inorganica Chimica Acta 304 (2000) 137–143
2.1. Potentiometric measurements
the substituent. Thus, N-alkyl derivatives enhance the
basicity of the NH group [1–5], while electronic attrac-
tive substituents (such as pyrimidine bases) reduce the
basicity of the amino group coordinating to the metal
ion through the carboxylate group [6–9]. In addition to
this, a certain number of factors govern the coordina-
tion behaviour of N-pyrimidine a-aminoacids ligands,
among others, the R-group on the Ca (see Scheme 1),
the nature of the metal ion and the pH. Our aqueous
solution studies have show that in neutral or slightly
basic medium these ligands coordinate through the
deprotonated carboxylate group, while in acidic
medium the carboxylate group remains protonated and
interactions take place through the exocyclic oxo and
nitroso groups belonging to the pyrimidine moiety
(Scheme 1) [7–10].
Previously acidified aqueous solutions containing
Zn(II)/HL mixtures ([HL]=10−3 M) in 1:1 and 1:4
molar ratios, were titrated potentiometrically with 0.1
M KOH at 35°C and 0.1 M KCl ionic strength in order
to study the complex formation processes. The pH
range investigated was usually 2.5–7.5, before the
Zn(OH)2 precipitation.
Calibration of electrodes (Gran’s method [12]) and
the ionic product of the medium [13] was through the
titration of known amounts of HCl with CO2-free
KOH solutions. The BEST program [14] was used to
calculate the formation constants. In these calculations,
previously reported values of protonation constants of
the ligand were used [10]. The species formed in the
equilibria are labelled by the pqr parameters, which
define the number of metal ions, deprotonated ligands
and protons, respectively.
In the present paper we study the reactivity of Zn(II)
and Cd(II) ions with N-2-(4-amino-1,6-dihydro-1-
methyl-5-nitroso-6-oxopyrimidinyl)glycine (HL), in
aqueous solution and in solid state, and the results are
compared to those obtained by us for related systems.
2.2. Preparation of the complexes
2.2.1. [Zn(L)2(H2O)4]·6H2O (1)
To a mixture of HL (1 mmol) and KOH (1 mmol) in
50 ml of water, ZnCl2 (1 mmol) was added under
stirring, resulting a pH 6.5 solution. After 24 h at room
temperature (r.t.) an orange crystalline solid appeared,
which being submerged in the mother liquor keeps both
its crystalline appearance and stoichiometry; otherwise,
if it is filtered off, washed with ethanol and ether, and
dried over P4O10 results in a powdered solid phase of
2. Experimental
The ligand was obtained by following a previously
reported procedure [10]. Nanopure water was used as
solvent for potentiometric measurements. Standardised
KOH, HCl, ZnCl2 and CdCl2 aqueous solutions
(Merck) were also used. All the potentiometric mea-
surements were carried out in 0.1 M KCl as back-
ground electrolyte.
C, H and N microanalyses were performed with a
Fison’s EA-1109 instrument. IR and NMR spectra, and
TG and DSC diagrams were obtained as already re-
ported [8]. The potentiometric assembly was described
in a previous work [11], and the pH measurements were
carried out with a calomel K4040 and a glass G2040B
Radiometer electrodes.
[ZnL2(H2O)4]
stoichiometry.
Anal.
Calc.
for
ZnC14H24N10O12: C, 28.51; H, 4.07; N, 23.75. Found:
C, 28.36; H, 4.26; N, 23.62%. Thermal data: Dehydra-
tion processes [ZnL2(H2O)4]“[ZnL2] occur in the 50–
240°C temperature range, corresponding to a weight
loss of 12.10% (calc. for 4H2O: 12.22%). In the DSC
appear as four endothermic effects centred at 93.3,
144.8, 168.8 and 206.3°C with DH of −46.31, −7.66,
−16.50 and −14.32 kJ mol−1, respectively. Pyrolysis
of ZnL2 starts at 250°C and ends at 760°C to yield ZnO
as residue (13.8%).
2.2.2. {[Cd(v-L)Cl(H2O)2]·H2O}n (2)
To a mixture of HL (1 mmol) and KOH (1 mmol) in
50 ml of water, CdCl2 (1 mmol) was added, resulting a
pH 6.0 solution. This was evaporated at r.t. appearing
a rose solid which was filtered off and despised. Five
days later a violet crystalline solid appeared, which was
collected, washed with ethanol and ether, and dried
over P4O10. Anal. Calc. for CdC7H14N5O7Cl: C, 19.63;
H, 3.27; N, 16.36. Found: C, 19.65; H, 3.03; N, 16.10%.
Thermal
data:
Dehydration
process
{[Cd(m-
L)Cl(H2O)2]·H2O}n“[CdLCl] occurs in the tempera-
ture range 60–180°C, appearing as two overlapped
endothermic effects in the DSC curve with an averaged
Scheme 1.

P. Arranz-Mascaro´s et al. / Inorganica Chimica Acta 304 (2000) 137–143
139
Table 1
empirical „-scan. Structures were solved by direct
methods and subsequent Fourier syntheses with the
SHELXTL-PC V5.0 package [15]. Non-hydrogen atoms
were refined anisotropically in the final cycles, while
hydrogen were placed at their calculated position and
were refined isotropically riding on the previous atoms.
Neutral atomic scattering and dispersion factors were
those included in the SHELXTL-PC program.
Crystal data and structure refinement for 1 and 2
Complex
1
2
Empirical formula
Formula weight
Temperature (K)
Wavelength (A)
Crystal system
Space group
ZnC14H36N10O18
697.90
293(2)
0.71069
triclinic
C7H14N5O7ClCd
428.08
293(3)
0.71073
triclinic
,
(
(
P1
P1
Unit cell dimensions
,
a (A)
7.453(2)
8.290(2)
12.724(3)
105.835(5)
91.058(5)
109.73(5)
1
706.6(3)
1.640
0.966
6.7316(11)
9.4810(14)
11.087(2)
83.695(8)
77.616(8)
77.190(8)
2
672.5(2)
2.114
1.866
3. Results and discussion
,
b (A)
,
c (A)
3.1. Solution study
h (°)
i (°)
k (°)
The acid–base behaviour of this family of N-pyrim-
idine aminoacids (see Scheme 1) is, as could be ex-
pected, qualitatively similar. The first protonation
process involves the carboxylate group whereas the
second protonation occurs on the pyrimidine ring [7].
Nevertheless, the pH values at which these processes
take place significantly vary within this series of com-
pounds, as shown in Table 2, which is due to the
different nature of the R group on the aminoacid rest.
In view of this, we are investigating the coordinative
behaviour of these ligands toward different metal ions,
such as Zn(II) and Cd(II), in aqueous medium.
Z
3
,
V (A )
Dcalc (g cm−3
)
Absorption coefficient
(mm−1
F(000)
Crystal size (mm)
q range (°)
)
364
424
0.25×0.20×0.35
1.685q529.99
−105h510
−115k511
05l517
0.30×0.20×0.08
1.805u530.0
−15h58
−135k513
−1551515
4630
Limiting indices
Reflections collected
Independent reflections 4117
[Rint=0.0018]
8234
3706
[Rint=0.0186]
full-matrix
least-squares
on F2
The potentiometric study of the 1:1 [M(II)]/[HL]
systems (where HL stands for N-2-(4-amino-1,6-dihy-
dro-1-methyl-5-nitroso-6-oxopyrimidinyl)glycine
Refinement method
full-matrix
least-squares
on F2
and
Data/restraints/
parameters
4109/0/196
3706/0/190
M(II)=Zn and Cd) points out a rather weak interac-
tion between the ligand and the metal ions, where only
the M(OH)2 species were detected [9], which could be
indicative of dissociation processes of the possible ad-
ducts formed.
The best fit of the experimental results obtained from
solutions with 1:4 [Zn(II)]/[HL] ratio corresponds to the
equilibria given in Table 2 (|fit=0.0071). Although the
Zn(HL)2+ species exists in little extension (Fig. 1) it
was included in the postulated model because it af-
Goodness-of-fit (F2)
R indices [I\2|(I)]
1.090
1.043
R1=0.0494
Rw2=0.1282
0.636 and
−0.714
R1=0.0231
Rw2=0.0601
0.535 and
−0.535
Largest peak and hole
−3
,
(e A
)
DH of −51.0 kJ mol−1, corresponding to a weight loss
of 12.26% (calc. for 3H2O: 12.61%). Pyrolysis of
[CdLCl] occurs in the temperature range of 220–800°C
to yield CdO (18.53%) and sublimated CdCl2.
Table 2
Solution data
2.3. X-ray data collection and structure determination
Species (pqr) Process
Log i
Reference
Single-crystal data collection for 1 were obtained
from a crystal submerged in the mother liquors in a
Lindeman capillary tube. Data collection for 1 and 2
were performed at 293 K with a Siemens R 3m/V
diffractometer using graphite monochromatized using
graphite Mo Ka radiation. Crystal data and details of
the structure determination are included in Table 1.
The unit cell parameters were calculated by least-
squares refinement of 25 well centred reflections in the
range 15B2qB45°. The data were collected by ꢀ/2q
scan mode and were corrected for Lorenz and polarisa-
tion effects. Absorption correction were applied via an
(011)
(011)
(011)
(012)
(012)
(012)
(111)
(120)
(111)
(120)
L
−+H+=HL
3.98(3)
3.34(1)
3.88(3)
6.54(4)
4.89(3)
6.30(4)
[10]
[7]
[8]
[10]
[7]
[8]
this work
this work
[9]
(L1)−+H+=HL1
(L2)−+H+=HL2
L
−+2H+=H2L+
(L1)−+2H+=(H2L1)+
(L2)−+2H+=(H2L2)+
Zn2++L−+H+=Zn(HL)2+ 5.28(4)
Zn2++2L−=Zn(L)2
7.61(2)
Cd2++L−+H+=Cd(HL)2+ 5.44(9)
Cd2++2L−=Cd(L)2
7.47(9)
−15.56(1) this work
−30.20(3) this work
[9]
(102)
Zn2+=Zn(OH)2+4H+
Zn2+=Zn(OH)42−+4H+
(
(
(104)

140
P. Arranz-Mascaro´s et al. / Inorganica Chimica Acta 304 (2000) 137–143
different behaviour exhibited by the HL ligand with
Zn(II) and Cd(II) compared to the related HL1 (see
Scheme 1). Thus, in the case of the HL1 only the ZnL21
[log i=6.42(1)] and Cd(HL)2+ [log i=6.81(8)] spe-
cies were detected [7]. In order to elucidate the effect of
the R substituent on the aminoacid moiety we are
working with the related alanine- and valine- deriva-
tives, HL2 and HL3, respectively (Scheme 1).
3.2. Solid study
Complexes [Zn(L)2(H2O)4]·6H2O (1) and {[Cd(m-
L)Cl(H2O)2]·H2O}n (2) were obtained by reacting the
corresponding metal(II) chloride with the deprotonated
L ligand in a 1:1 ratio. When the N-pyrimidine
aminoacids ligands act deprotonated their primary co-
ordination site is the carboxylate group. In addition to
this, these ligands are able to use the pyrimidine moiety,
which is the primary coordination site when they act in
neutral form, to yield polynuclear complexes. This fact
is also favoured by a 1:1 metal-to-ligand ratio since the
metal can complete its coordination sphere by interact-
ing with additional ligands, which act bridging two or
more metal ions [7,8,10].
Fig. 1. Distribution species diagram for [Zn(II)]/[HL] at 1:4 molar
ratio versus pH.
forded an improvement in the |fit value. At 1:4 metal-
to-ligand ratio both metal ions, Zn(II) and Cd(II) [9],
exhibit a similar behaviour. Thus, very close log i
values are obtained for the M(HL)2+ and ML2 species
(Table 2), being lower to those observed for the Cu(II)/
HL system [10]. For the M(HL)2+ complexes the car-
boxylate group remains protonated, by which the
coordination likely takes place through the exocyclic
nitroso and oxo groups of the pyrimidine ring, at it has
been observed for the related 4-amino-5-nitroso-6-ox-
opyrimidine base [16]. As for the ML2 species the
log i120 values are still lower than that of CuL2 but less
than for the former M(HL)2+ complexes, which is
indicative that when the carboxylate group is the pri-
mary coordination site the reactivity of the ligand in-
creases [7–9]. Nevertheless, it has to be pointed out the
In this line, the related Zn(II) and Cd(II) complexes
obtained by us with the methionine derivative (HL1)
show a supramolecular 2D layered structure in which
the R groups (R=CH2CH2SCH3), see Scheme 1, are
oriented to the external surfaces of the layers, resulting
,
in an interlayer separation of approximately 11 A [7].
Therefore, one might expect that by replacing the HL1
Fig. 2. A perspective view of complex 1 (ellipsoids represent 40% of probability).

P. Arranz-Mascaro´s et al. / Inorganica Chimica Acta 304 (2000) 137–143
141
Table 3
to those reported for similar structures [17–20], and do
not deserve additional comments. The tridimensional
structure of 1 is achieved by an extended and compli-
cated hydrogen bonding network involving the coordi-
nated and the six lattice water molecules and the L
ligands. These lattice water molecules are lost very
easily, by which the crystal structure was solved sub-
merging the crystal in the mother liquor. Within this
network of hydrogen bonding it is noteworthy to men-
tion the intramolecular hydrogen bond between the
N(4)H2 and the O(5) atom, which is retained in dmso
a
,
Selected bond lengths (A) and angles (°)
Complex 1
Zn(1)ꢀO(24)
Zn(1)ꢀO(1w)
Zn(1)ꢀO(2w)
2.083(2)
2.053(2)
2.196(2)
Zn(1)ꢀO(24)I
Zn(1)ꢀO(1w)I
Zn(1)ꢀO(2w)I
2.083(2)
2.053(2)
2.196(2)
O(1w)ꢀZn(1)ꢀO(1w)I 180.0
O(24)IꢀZn(1)ꢀO(2w)
O(24)ꢀZn(1)ꢀO(2w)
O(1w)IꢀZn(1)ꢀO(2w)I
O(1w)ꢀZn(1)ꢀO(2w)I
O(24)IꢀZn(1)ꢀO(2w)I
O(24)ꢀZn(1)ꢀO(2w)I
92.60(9)
87.40(9)
91.53(9)
88.47(9)
87.40(9)
92.60(9)
O(1w)IꢀZn(1)ꢀO(24)I 90.04(7)
O(1w)ꢀZn(1)ꢀO(24)I
O(1w)IꢀZn(1)ꢀO(24)
O(1w)ꢀZn(1)ꢀO(24)
89.96(7)
89.96(7)
90.04(7)
O(24)IꢀZn(1)ꢀO(24) 180.0
O(1w)IꢀZn(1)ꢀO(2w) 88.47(9)
O(2w)ꢀZn(1)ꢀO(2w)I 180.0
1
solutions as reveal the H NMR signals listed in Table
O(1w)ꢀZn(1)ꢀO(2w)
91.53(9)
4. This hydrogen bond has only not been observed
when the pyrimidine moiety coordinates in a chelating
fashion through the O(5)/O(6) atoms [16].
Complex 2
Cd(1)ꢀO(1W)
Cd(1)ꢀO(24)
Cd(1)ꢀO(2W)
Cd(1)ꢀO(6)
2.350(2)
2.361(2)
2.361(2)
Cd(1)ꢀN(5)
Cd(1)ꢀO(23)
Cd(1)ꢀCl(1)
2.455(2)
2.469(2)
2.5667(7)
134.56(6)
On the other hand, complex 2 consists of infinite
chains running approximately perpendicular to the ab
plane, see Fig. 3. Within the polynuclear structure each
Cd(II) is heptacoordinated by two bidentate L ligands,
two water molecules and a Cl− ion, being the mononu-
clear fragment: Cd(m-L)Cl(H2O)2. This heptacoordina-
tion for a cadmium(II) ion, which can be described as a
distorted pentagonal bipyramid with the O(2w) and
Cl(1) occupying the axial positions, is not unusual and
have been found for complexes with related ligands
[21–23]. The coordination mode of the ligand can by
described as a bis-didentate-bridging mode, linking the
metal ions through the pyrimidine and the carboxylate
group to yield a metal-metal intrachain distance of
2.3834(14) O(1w)ꢀCd(1)ꢀO(24)
O(1w)ꢀCd(1)ꢀO(2w)
O(1W)ꢀCd(1)ꢀO(6)
O(2W)ꢀCd(1)ꢀO(6)
O(24)ꢀCd(1)ꢀN(5)
O(6)ꢀCd(1)ꢀN(5)
O(24)ꢀCd(1)ꢀO(23)
O(6)ꢀCd(1)ꢀO(23)
O(1W)ꢀCd(1)ꢀCl(1)
86.54(7)
76.34(6)
84.54(6)
80.47(5)
67.96(5)
54.32(5)
156.60(5)
91.21(5)
O(24)ꢀCd(1)ꢀO(2W)
O(24)ꢀCd(1)ꢀO(6)
O(1W)ꢀCd(1)ꢀN(5)
O(2W)ꢀCd(1)ꢀN(5)
O(1W)ꢀCd(1)ꢀO(23)
O(2W)ꢀCd(1)ꢀO(23)
N(5)ꢀCd(1)ꢀO(23)
O(24)ꢀCd(1)ꢀCl(1)
O(6)ꢀCd(1)ꢀCl(1)
O(23)ꢀCd(1)ꢀCl(1)
89.80(6)
148.24(5)
144.01(6)
85.70(6)
80.47(6)
90.96(7)
134.71(5)
95.80(5)
89.42(4)
94.26(5)
O(2W)ꢀCd(1)ꢀCl(1) 173.90(5)
N(5)ꢀCd(1)ꢀCl(1) 92.85(4)
a I=−x+1, −y+1, −z+1.
,
11.671 A. The IR spectrum is, as expected, consistent
with this coordination mode. Thus, in 2 the w(NO) and
w(CO) bands are also shifted to lower frequencies, as
ligand by HL, where R=H, and working in identical
conditions we would obtain bidimensional polynuclear
complexes with reduced interlayer separation. Despite
of this, complex 1 consists of neutral mononuclear
entities in which the zinc ion is hexacoordinated by two
L ligands, completing the coordination sphere with four
water molecules, as depicted in Fig. 2. Selected bond
lengths and angles are listed in Table 3. The six ligands
are arranged around the Zn(II) ion in a distorted
octahedral geometry, with the metal ion lying on a Ci
centre. In this description two water molecules and two
monodentate carboxylate groups forms the equatorial
plane while the two remaining water molecules occupy
the axial positions at a longer distance (see Table 3).
The coordination mode of the ligand is also evident
well as the w(CO2−
)
band (Table 4). The NMR
symm
data are, as in 1, also consistent with a coordination of
the ligand to the Cd(II) ion only through the carboxy-
late group, as reveals the displacement to lower field of
the COO− signal and the unaffected displacements of
Table 4
Selected IR, 1H and 13C NMR data
KL·H2O
1
2
a
w(OH)+w(NH) 3458, 3239
3470, 3353, 3229 3426, 3357
w(C(6)ꢁO)
w(CO2)symm
w(NO)
1688
1622
1495
10.93, 8.34
3.59
1691
1602
1497
10.90, 8.30
3.96
1657
1598
1455
10.83, 8.35
4.03
from the IR spectrum; where the w(CO2−
)
band in
symm.
b
l N(4)H2
the uncoordinated ligand is shifted to lower frequency
while the w(CꢁO) and w(NꢁO) bands remain practically
unaffected (Table 4). In addition to this, the NMR data
also support this coordination mode, since the 13C-sig-
nal belonging to the COO− group is shifted to lower
field with respect to the L ligand, whereas the Ca¦ C(5)
and C(6) signals remain practically unaffected, see
Table 4. Remaining bond lengths and angles are similar
l C(a)H2
l C(a) c
46.12
45.01
44.02
l CO2
l C(6)ꢁO
l C(5)ꢀNO
168.68
168.61
141.92
172.78
161.66
141.11
174.16
161.68
141.42
a IR: cm−1 (KBr).
b 1H NMR: l(ppm), dmso-d6.
c 13C NMR: l(ppm), dmso-d6.

142
P. Arranz-Mascaro´s et al. / Inorganica Chimica Acta 304 (2000) 137–143
Fig. 3. Perspective views of the mononuclear fragment and a chain of complex 2 (ellipsoids represent 40% of probability).
the Ca, C(5) and C(6) signals, see Table 4. Obviously,
this fact indicates that the polynuclear structure is not
retained in dmso solutions, being the pyrimidineꢀmetal
bond the cleavage point, which, in turn, is in agree-
ment with the aqueous solution results since the pri-
mary coordination site when the ligand acts
deprotonated is the carboxylate group.
Bond distances and angles are usual for Cd(II) com-
plexes, except for N(5) and O(23) which are slightly
longer due to the steric crowding present in both
chelate rings [21–24].
family of ligands. The different reactivity is not only
evident from the solution studies but also from the
corresponding metal complexes isolated in solid state.
Thus, the HL ligand shows a marked trend to form
complexes of lower dimensionality when compared to
HL1, since for Zn(II) a mononuclear complex has been
obtained while for Cd(II), although the complex is
polynuclear, is monodimensional and not bidimen-
sional as in the case of HL1. Nevertheless, more exam-
ples of this family of ligands are needed in order to
understand all the factors, and in particular the role of
the substituent R on the Ca, in which we are currently
working.
Finally, it has to be noted again, the important
effect of the R-substituent in the reactivity of this
.

P. Arranz-Mascaro´s et al. / Inorganica Chimica Acta 304 (2000) 137–143
143
[12] G. Gran, Analyst 77 (1952) 661.
[13] A. Liberti, T.S. Light, J. Chem. Ed. 39 (1962) 236.
Acknowledgements
[14] A.E. Martell, R.J. Motekaitis, The Determination and Use of
Stability Constants, VCH, New York, 1992.
[15] SHELXTL-PC V5.0, Siemens Analytical X-ray Instruments,
Madison, WI, 1995.
The authors thank Junta de Andaluc´ıa for financial
support.
[16] P. Arranz-Mascaro´s, M.L. Godino-Salido, R. Lo´pez-Garzo´n,
M.D. Gutie´rrez-Valero, J.M. Moreno, Polyhedron 18 (1999)
689.
References
[17] H. Grewe, M.R. Udupa, B. Krebs, Inorg. Chim. Acta 63
(1982) 119.
[18] A. Fuertes, C. Miravitlles, E. Escriva, E. Coronado, D. Bel-
tran, L. Padel, J. Chem. Soc., Dalton Trans. (1989) 863.
[19] X-M. Chen, X-C. Huang, M-L Tong, Y-X. Tong, S.W. Ng,
Aus. J. Chem. 50 (1997) 865.
[20] N. Lalioti, C.P. Rastopoulou, A. Terzis, A. Panagiotopoulos,
S.P. Perlepes, E. Manessi-Zoupa, J. Chem. Soc., Dalton Trans.
(1998) 1327.
[21] N. Nakasuka, S. Azuma, M. Tanaka, Acta Crystallogr., Sect.
C 42 (1986) 1736.
[22] H.C. Lopez-Sandoval, N. Barba-Behrens, S. Bernes, N. Far-
fan-Garcia, H. Hopfl, J. Chem. Soc., Dalton Trans. (1997)
3415.
[23] E. Bermejo, A. Castin˜eiras, R. Dom´ınguez, J. Stra¨hle, C.
Maichle-Mo¨ssmer, Polyhedron 15 (1996) 1923 and refs.
therein; K.H. Chung, E. Hong, Y. Do, C.H. Moon, J. Chem.
Soc., Dalton Trans. (1996) 3363 and refs. therein.
[24] C.I.H. Ashby, W.F. Paton, T.L. Brown, J. Am. Chem. Soc.
102 (1980) 2990.
[1] B. Kaitner, N. Paulic, N. Raos, J. Coord. Chem. 25 (1992) 95.
[2] N. Paulic, N. Raos, J. Coord. Chem. 31 (1994) 181.
[3] N. Raos, J. Mol. Struct. 355 (1995) 211.
[4] J. Sabolovic, K. Rasmussen, Inorg. Chem. 34 (1995) 1221.
[5] D.B. Grotjahn, C. Joubran, Organometallics 15 (1996) 1230.
[6] M.A. D´ıaz-D´ıez, F.J. Garc´ıa-Barros, C. Valenzuela-Calahorro,
J. Inorg. Biochem. 56 (1994) 243.
[7] R. Lopez-Garzon, P. Arranz-Mascaro´s, M.L. Godino-Salido,
M.D. Gutierrez-Valero, J.M. Moreno, Inorg. Chim. Acta,
(1999) in press.
[8] P. Arranz-Mascaro´s, M.L. Godino-Salido, R. Lo´pez-Garzo´n,
M.D. Gutie´rrez-Valero, J.M. Moreno, Polyhedron 18 (1999)
793.
[9] P. Arranz-Mascaro´s, R. Lo´pez-Garzo´n, M.L. Godino-Salido,
M.D. Gutie´rrez-Valero, Transit. Met. Chem. 23 (1998) 501.
[10] J.M. Moreno, P. Arranz-Mascaro´s, R. Lo´pez-Garzo´n, M.D.
Gutie´rrez-Valero, M.L. Godino-Salido, J. Cobo-Domingo,
Polyhedron 18 (1999) 1635.
[11] M.L. Godino-Salido, M.D. Gutierrez-Valero, R. Lo´pez-Gar-
zo´n, J.M. Moreno, Inorg. Chim. Acta 221 (1994) 127.
.