Influence of tetrahedral distortion of CuN4 complexes on spectroscopic properties. Synthesis, characterization and crystal structures of [Cu(N-(2-methylpyridyl)benzenesulfonylamidate)2], [Cu(N-(2-methylpyridyl)toluenesulfonylamidate)2] and [Cu(N-(2-methylpyridyl)naphthalenesulfonylamidate)2] compounds

Article abstract of DOI:10.1016/S0277-5387(01)00717-3

A series of new N-sulfonamide ligands and their copper(II) complexes, [Cu(N-(2-methylpyridyl)toluenesulfonylamidate)₂] (1), [Cu(N-(2-methylpyridyl)benzenesulfonylamidate)₂] (2) and [Cu(N-(2-methylpyridyl)naphthalenesulfonylamidate)₂] (3), have been synthesized and characterized. Single crystal X-ray analysis of the three complexes revealed that all of them present a tetracoordinate CuN₄ chromophore. The ligands act as bidentate, coordinating the metal ion through the pyridine and sulfonamido N atoms. The main structural difference among the compounds is the varied degree of distortion of square-planar stereochemistry. Complex 1 exhibits a regular square-planar geometry. In complexes 2 and 3 the tetrahedrality values of 50.2° and 39.0° respectively indicate a strong distortion. EHMO calculations on idealized models show the correlation between the geometrical distortion and the spectroscopic properties.

Full text of DOI:10.1016/S0277-5387(01)00717-3

Polyhedron 20 (2001) 703–709
www.elsevier.nl/locate/poly
Influence of tetrahedral distortion of CuN4 complexes on
spectroscopic properties. Synthesis, characterization and crystal
structures of [Cu(N-(2-methylpyridyl)benzenesulfonylamidate)2],
[Cu(N-(2-methylpyridyl)toluenesulfonylamidate)2] and
[Cu(N-(2-methylpyridyl)naphthalenesulfonylamidate)2] compounds
Laura Gutierrez a, Gloria Alzuet a, Joaqu´ın Borra´s a,*, Malva Liu-Gonza´lez b,
Francisco Sanz b, Alfonso Castin˜eiras c
a Departamento de Qu´ımica Inorga´nica, Facultad de Farmacia, Uni6ersidad de Valencia, 46100 Burjassot, Valencia, Spain
b Departamento de Termolog´ıa, Uni6ersidad de Valencia, 46100 Burjassot, Valencia, Spain
c Departamento de Qu´ımica Inorga´nica, Uni6ersidad de Santiago, 15703 Santiago de Compostela, Spain
Received 9 October 2000; accepted 9 January 2001
Abstract
A series of new N-sulfonamide ligands and their copper(II) complexes, [Cu(N-(2-methylpyridyl)toluenesulfonylamidate)2] (1),
[Cu(N-(2-methylpyridyl)benzenesulfonylamidate)2] (2) and [Cu(N-(2-methylpyridyl)naphthalenesulfonylamidate)2] (3), have been
synthesized and characterized. Single crystal X-ray analysis of the three complexes revealed that all of them present a
tetracoordinate CuN4 chromophore. The ligands act as bidentate, coordinating the metal ion through the pyridine and
sulfonamido N atoms. The main structural difference among the compounds is the varied degree of distortion of square-planar
stereochemistry. Complex 1 exhibits a regular square-planar geometry. In complexes 2 and 3 the tetrahedrality values of 50.2° and
39.0° respectively indicate a strong distortion. EHMO calculations on idealized models show the correlation between the
geometrical distortion and the spectroscopic properties. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Tetracoordinate copper complexes; Crystal structures; Tetrahedral distortion
1. Introduction
for copper(II) and the factors which influence them
have been summarized by Hathaway [1]. The major
geometries that the copper takes up are octahedral and
square-pyramidal, and to a smaller extent square-pla-
nar and trigonal bipyramidal [2]. In blue copper
proteins, Cu(II) shows an elongated C36 distorted tetra-
hedral stereochemistry that gives rise to a small geome-
try change upon reduction that has been used to argue
that the blue copper site is an entatic or rack state [3].
Tetrahedrality for any tetracoordinate complex can be
characterized by the angle subtended by two planes,
each encompassing the copper and two adjacent donor
atoms. For strictly square-planar complexes with D4h
symmetry, the tetrahedrality is 0°. For tetrahedral com-
plexes with D2d symmetry, the tetrahedrality equals 90°.
Battaglia et al. correlated the dihedral angle with the
The importance of metal ions in biological systems is
well known. One of the very interesting features of
metal coordinated systems is the concerted spatial ar-
rangement of the ligands around the metal ion. Except
for special cases, the geometry exhibited by a coordi-
nated system is often distorted. Among metal ions of
biological importance, the copper(II) ion presents a
high number of complexes with distortion. The range of
stereochemistries which have now been characterized
* Corresponding author. Tel.: +34-96-3864530; Fax: +34-96-
3864960.
E-mail address: joaquin.borras@uv.es (J. Borra´s).
0277-5387/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0277-5387(01)00717-3

704
L. Gutierrez et al. / Polyhedron 20 (2001) 703–709
highest d–d transition in the electronic spectra of some
tetrachlorocuprates with compressed tetrahedral D2d
symmetry; they showed that this variation was linear
[4]. Later, a similar relationship was observed for a high
number of CuN4 complexes with the same symmetry
[5].
In a previous work we reported three copper(II)
complexes with the coordination polyhedron ranging
from highly distorted octahedral to distorted square-
pyramidal to slightly distorted square-planar geometry
[6]. We compared their electronic and EPR spectra with
the results obtained from molecular orbital calculations
on idealized models and we found a good agreement
between the theoretical results and the experimental
data.
In the present paper we present three copper(II)
complexes with a CuN4 arrangement obtained from
three related N-substituted sulfonamide ligands where
the distortion of the coordination polyhedron is differ-
ent. Our interest here is to uncover the structural
distortion in the spectroscopic properties of these cop-
per compounds.
2.3. Synthesis of [Cu(N-(2-methylpyridyl)toluene-
sulfonylamidate)2] (1), [Cu(N-(2-methylpyridyl)benzene-
sulfonylamidate)2] (2) and [Cu(N-(2-methylpyridyl)-
naphthalenesulfonylamidate)2] (3)
Cu(NO3)2·3H2O (0.24 g, 1 mmol) in 10 ml of DMF
was added to 10 ml of DMF solution containing 1
mmol of the corresponding ligand. Immediately, the
solution turned green. Then, 1 ml of aqueous 1 M
NaOH solution was added. The resulting dark green
solution was left to stand at room temperature (r.t.).
After 2 or 3 days brown–green crystals (complex 1) and
blue crystals (complexes 2 and 3) suitable for X-ray
diffraction were obtained.
Anal. Calc. for C26H26CuN4O4S2 (1) (yield 0.11 g,
44%): C, 53.3; H, 4.5; N, 9.6; S, 10.9. Found: C, 53.2;
H, 4.4; N 9.5; S 11.0%. IR (KBr) (wmax (cm−1)): 1610
w(py ring); 1280, 1140 w(SO2). Anal. Calc. for
C24H22CuN4O4S2 (2) (yield 0.098 g, 38%): C, 51.6; H,
4.0; N, 10.0; S, 11.5. Found: C, 51.7; H, 3.9; N 9.8; S
11.8%. IR (KBr) (wmax (cm−1)): 1610 w(py ring); 1290,
1145 w(SO2). Anal. Calc. for C32H26CuN4O4S2 (3) (yield
0.14 g, 48%): C, 58.4; H, 4.0; N, 8.5; S, 9.7. Found: C,
58.2; H, 4.1; N 8.3; S 10.0%. IR (KBr) (wmax (cm−1)):
1610 w(py ring); 1285, 1145 w(SO2).
2. Experimental
2.4. Crystallography
2.1. Materials and physical measurements
2.4.1. [Cu(N-(2-methylpyridyl)toluenesulfonylamidate)2]
(1)
Copper nitrate trihydrate, benzenesulfonylchloride,
A brown–green prismatic crystal was mounted on a
glass fibre and used for data collection. Cell constants
and an orientation matrix for data collection were
obtained by least-squares refinement of the diffraction
data from 25 reflections in the range of 19.106°BqB
45.654° in an Enraf–Nonius CAD-4 automatic diffrac-
tometer [9]. Data were collected at 293 K using Cu Ka
toluenesulfonylchloride,
naphthalenesulfonylchloride
and 2-(aminomethyl)pyridine were reagent grade and
were used without purification. Analytical data (C, H,
N and S), IR, UV–Vis and EPR spectra were carried
out as described previously [7].
,
radiation (u=1.54184 A) and the ꢀ-scan technique,
2.2. Synthesis of the ligands
and corrected for Lorentz and polarization effects [10].
A semi-empirical absorption correction („-scans) was
made [11].
The N-(2-methylpyridyl)toluenesulfonylamide was
obtained by condensation of 2-(aminomethyl)pyridine
and toluenesulfonylchloride following the synthesis pro-
cedure previously described [8]. The other two ligands
were obtained in a similar way but using benzenesul-
fonylchloride and naphthalenesulfonylchloride instead
of toluenesulfonylchloride.
N-(2-methylpyridyl)benzenesulfonylamide (yield 0.57
g, 53%). Anal. Calc. for C12H12N2O2S: C, 58.0; H, 4.8;
N, 11.2; S, 12.9. Found: C, 57.3; H, 4.7; N 11.1; S
12.7%. IR (KBr) (wmax (cm−1)): 3440 w(N–H); 1598
w(py ring); 1330, 1160 w(SO2).
The structure was solved by direct methods [12],
which revealed the position of all non-hydrogen atoms,
and refined on F2 by a full-matrix least-squares proce-
dure using anisotropic displacement parameters [13].
All hydrogen atoms were located from difference
Fourier maps and were refined isotropically. Atomic
scattering factors were from Ref. [14]. Molecular graph-
ics were from PLATON-98 [15]. A summary of the crystal
data, experimental details and refinement results is
listed in Table 1.
N-(2-methylpyridyl)naphthalenesulfonylamide (yield
0.75 g, 71%). Anal. Calc. for C16H14N2O2S: C, 64.4; H,
4.7; N, 9.4; S, 10.7. Found: C, 63.5; H, 4.8; N, 8.9; S,
10.4%. IR (KBr) (wmax (cm−1)): 3450 w(N–H); 1595
w(py ring); 1330, 1160 w(SO2).
2.4.2. [Cu(N-(2-methylpyridyl)benzenesulfonylamidate)2]
(2) and [Cu(N-(2-methylpyridyl)naphthalene-
sulfonylamidate)2] (3)
Green crystals were of size 0.20×0.25×0.30 mm
(complex 2) and 0.3×0.3×0.2 mm. (complex 3).

L. Gutierrez et al. / Polyhedron 20 (2001) 703–709
705
Throughout the experiment Mo Ka radiation was used
with a graphite crystal monocromator on an Enraf–
Nonius CAD-4 [16]. single crystal diffractometer (u=
mized was [ꢀꢀ(Fo2−Fc2)2/ꢀꢀ(Fo2)2]1/2, ꢀ=1/[|2(Fo2)
+(0.0828P)2] with |(Fo2) from counting statistic and
P=[(max(Fo2,0)+2Fc2)]/3. The final difference Fourier
3
,
,
0.7173 A).The unit cell dimensions were determined
map showed a peak of 0.600 A close to the Cu atoms,
3
,
from the angular settings of 25 reflections with q from
2.38 to 25.97° (complex 2) and from 1.59 to 26.08°
(complex 3). The space group was determined to be P21
the other peaks no deeper than −0.356 A for complex
3
,
2 and a peak of 0.397 A close to the atoms of Cu, the
3
,
other peaks not deeper than −0.595 A for complex 3.
(
(complex 2) from systematic absences and P1 (complex
The figures were drawn with ORTEP [22]. Atomic scat-
tering factors were made with PARST [23]. A summary
of the crystal data, experimental details and refinement
results is collected in Table 1.
3) from no systematic absences by ABSEN [17]. The
intensity data of 2571, in hkl range (0,0,−11) to
(11,18,10) and limits (1°BqB25°) for complex 2 and
5964 in hkl range (−10,−15,−17) to (0,15,17) and
limits (1°BqB25°) for complex 3 were measured, us-
ing the ꢀ–2q scan technique and variable scan rate
with a maximum scan time of 60 s per reflection. The
intensity of the primary beam was checked throughout
the data collection by monitoring three standard reflec-
tions every 60 min. On all reflections, profile analysis
was performed [18]. Lorentz and polarization correc-
tions were applied and then data were reduced to F02
values. The structure was solved using SIR-92 [19].
Isotropic least squared refinement on F2 was made
using SHELX-93 [20]. During the final stages of the
refinement on F2 the positional parameters and the
anisotropic thermal parameters of the non-hygrogen
atoms were refined. The hydrogen atoms were located
by XHYDEX [21]. The final conventional agreement
factors were R=0.039 and wR2=0.076 for 2425 ‘ob-
served’ reflections and 331 variables for complex 2 and
R=0.07 and wR2=0.15 for 5581 ‘observed’ reflections
and 408 variables for complex 3. The function mini-
2.5. EHMO calculations
All calculations were performed using the package of
Programs for Molecular Orbital Analysis by Mealli and
Proserpio [24] based on CDNT (atom Cartesian coordi-
nate calculations), ICON (extended Hu¨ckel method
with the weighted Hij formula) and FMO (fragment
molecular orbital), included in the drawing program
CACAO (computer aided composition of atomic
orbitals).
The extended Hu¨ckel parameters are as follows. Hij
(Ev): Cu 4s, −11.40; Cu 4p, −6.06; Cu 3d, −14.00;
N 2s, −26.00; N 2p, −13.401.950; S 3s, −20.30; S
3p, −14.00; O 2s, −32.30; O 2p, −14.80; C 2s,
−21.40; C 2p, −11.40; H 1s, −13.60 eV. Orbital
exponents(contraction coefficients in double-j expan-
sion given in parentheses): Cu 4s, 4p, 2.20; Cu 3d, 5.95
(0.5933), 2.30 (0.5744); N 2s, 2p, 1.950; S 3s, 3p, 1.900;
O 2s, 2p, 2.275; C 2s, 2p, 1.625; H 1s, 1.300.
Table 1
Crystal data and structure refinement for 1, 2, and 3
1
2
3
Formula
Symmetry
Space group
Unit cell dimensions
C26H26N4O4S2Cu
monoclinic
P21/c
C24H22N4O4S2Cu
monoclinic
P21
C
32H26N4O4S2Cu
triclinic
P1
(
,
a (A)
7.393(7)
17.081(14)
9.950(5)
90.0
99.307(6)
90.0
1239.9(17)
2
1.57
9.363(3)
14.798(2)
9.414(2)
90.0
114.39(2)
90.0
1188(4)
2
1.560
558.12
574
8.890(5)
12.434(5)
14.235(5)
114.77(5)
97.072(5)
91.289(5)
1413.0(11)
2
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
3
,
U (A )
Z
Dcalc (g cm−3
M
)
1.547
658.23
678
586.2
606
31.7
F(000)
v (cm−1
)
11.3
9.68
Goodness-of-fit
R
Rw
1.104
0.036
0.101
1.043
0.039
0.076
1.001
0.077
0.155

706
L. Gutierrez et al. / Polyhedron 20 (2001) 703–709
Table 2
,
Selected bond distances (A) and angles (°) for compounds 1, 2 and 3
1
2
3
Bond distances
Cu(1)–N(2)
1.9909(17)
1.9909(17)
1.9984(17)
1.9984(17)
Cu(1)–N(2A)
Cu(1)–N(2)
Cu(1)–N(1)
Cu(1)–N(1A)
1.929(5)
1.932(5)
1.989(6)
2.001(5)
Cu(1)–N(2)
Cu(1)–N(2A)
Cu(1)–N(1)
Cu(1)–N(1A)
1.925(9)
1.953(9)
1.994(9)
1.993(8)
Cu(1)–N(2)c
Cu(1)–N(1)
Cu(1)–N(1)c
Bond angles
N(2)–Cu(1)–N(2)c
N(2)–Cu(1)–N(1)
N(2)c–Cu(1)–N(1)
N(2)–Cu(1)–N(1)c
N(2)c–Cu(1)–N(1)c
N(1)–Cu(1)–N(1)c
180.0
N(2A)–Cu(1)–N(2)
N(2A)–Cu(1)–N(1)
N(2)–Cu(1)–N(1)
N(2A)–Cu(1)–N(1A))
N(2)–Cu(1)–N(1A)
N(1)–Cu(1)–N(1A)
157.0(3)
105.4(3)
82.5(2)
83.3(2)
104.9(2)
139.4(3)
N(2)–Cu(1)–N(2A)
N(2)–Cu(1)–N(1)
N(2A)–Cu(1)–N(1)
N(2)–Cu(1)–N(1A)
N(2A)–Cu(1)–N(1A
N(1)–Cu(1)–N(1A)
161.9(4)
82.5(4)
103.6(4)
102.2(4)
81.7(4)
83.02(7)
96.98(7)
96.98(7)
83.02(2)
180.0
148.4(3)
,
3. Results and discussion
tances are slightly lower [1.929(5) and 1.932(5) A]. The
main structural differences between complexes 1 and 2
can be observed in the bond angles of the CuN4 chro-
mophore. While in complex 1 the diagonal angles
N(1)–Cu(1)–N(1)c and N(2)–Cu(1)–N(2)c are
180°, in complex 2 these angles are 139.4(3)° and
157.0(3)° respectively. The strong distortion from the
square-planar geometry of complex 2 is indicated by
the tetrahedrality value of 50.2°.
3.1. Crystal structures
Relevant bond distances and angles for the three
complexes are given in Table 2. Figs. 1–3 show molec-
ular drawings of the complexes 1, 2 and 3 respectively
with the atom numbering scheme.
The crystal structure of complex 1 consists of
monomer units linked by stacking interactions between
the aromatic rings (mean distances between rings,
In complex 3 (Fig. 3) the Cu(II) ion resides in a
distorted square-planar environment that consists of
four nitrogen atoms of two deprotonated ligands. Each
ligand, acting as bidentate, links the metal ion through
its pyridyl and sulfonamidate nitrogen atoms. The Cu–
Nsulfonamidate bond distances are 1.925(9) and 1.953(9) A
and the Cu–Npyridyl distances are 1.993(8) and 1.994(9)
A. The tetrahedrality of the CuN4 chromophore is
39.0°, this value is intermediate between that observed
in complex 1 and complex 2.
,
3.571(4) A), see Fig. 4. The copper(II) ion is bound
centrosymmetrically by two deprotonated ligands in a
square-planar environment. Each ligand coordinates
the metal ion through the Npyridyl and the Nsulfonamidate
,
,
atoms, with mean Cu–N bond distances of 1.99 A.
,
These distances are similar to those reported for other
N-(2-methylpyridyl)toluenesulfonylamide copper com-
plexes [8] and for copper complexes with the related
sulfathiazole ligand [7]. The coordination bond angles,
ranging from 83.02(7)° [N(2)–Cu(1)–N(1)] to 96.98(7)°
[N(2)–Cu(1)–N(1)c], deviate slightly from those of
a regular square-planar geometry. The Cu(II) ion is in
the plane formed by the four N atoms; the dihedral
angle between the planes Cu(1)N(1)N(2) and
Cu(1)N(1)cN(2)c equal to 0° confirms the square-
planar arrangement of the CuN4 chromophore. The
coordination behavior of the ligand as bidentate gives
rise to a planar five-membered chelate ring that proba-
bly stabilizes the complex.
The most striking difference among the complexes 1,
2 and 3 is the varied degree of square-planar distortion.
The crystal structure of complex 2 shows the Cu(II)
ion surrounded by four N atoms from two deproto-
nated N-(2-methylpyridyl)benzenesulfonylamide lig-
ands in a very distorted square-planar arrangement.
The ligand presents the same bidentate behavior of the
N-(2-methylpyridyl)toluenesulfonylamide ligand in
complex 1. The Cu–Npyridyl bond distances [1.989(6)
,
and 2.001(5) A] are similar to the corresponding dis-
tances in complex 1 however, the Cu–Nsulfonamidate dis-
Fig. 1. Molecular drawing of [Cu(N-(2-methylpyridyl)toluenesul-
fonylamidate)2] (1) with the atom numbering scheme.

L. Gutierrez et al. / Polyhedron 20 (2001) 703–709
707
Fig. 2. Molecular drawing of [Cu(N-(2-methylpyridyl)benzenesulfonylamidate)2] (2) with the atom numbering scheme.
Fig. 3. Molecular drawing of [Cu(N-(2-methylpyridyl)naphtalenesulfonylamidate)2] (3) with the atom numbering scheme.
The three ligands in the compounds differ only in the
aromatic ring on the sulfur atom of the sulfonamide
group. At first, it could be suggested that the size of the
rings and therefore the steric effect afforded by them
would be a determining factor governing the degree of
the distortion of the coordination polyhedra. In this
sense, the distortion might increase in the order 2B1B
3. However, in our complexes the increment is found to
be in the order 1B3B2 and hence the dissimilarity in
the spatial arrangement around copper cannot arise
only as a result of steric effects of the ligand. In the
particular case of complex 1, the almost regular geome-
try of its coordination polyhedron could be determined
by the stacking interactions in the molecular structure.

708
L. Gutierrez et al. / Polyhedron 20 (2001) 703–709
Fig. 4. Crystal packing of [Cu(N-(2-methylpyridyl)toluenesulfonylamidate)2] (1).
3.2. Spectroscopic properties
the electronic structures of the compounds, so we have
designed three idealized models substituting the four N
atoms of the ligands by ammonia molecules using the
coordinates of the ligand N donor atoms obtained from
the crystallographic data. In this way, the copper ion
and the N atoms retain the sites found in the crystal
structures and the distortion of coordination polyhe-
dron remains.
In the IR spectra of the three complexes the stretch-
ing vibrations of the pyridine ring and the SO2 group
are shifted (approximately 12–50 cm−1) from those of
the free ligands due to their involvement in coordina-
tion and to the deprotonation of the sulfonamido
moiety.
The solid electronic spectra of the three complexes
display a band near 25000 cm−1 assigned to a LMCT
transition. Furthermore, complex 1 exhibits a d–d
broad band at about 20000 cm−1 and the other two
complexes show a broad and weak band at about 16000
cm−1. These electronic spectra are consistent with the
degree of distortion from the square-planar geometry
found in the X-ray structural analysis.
The X-band EPR spectra at room temperature of
polycrystalline samples of compounds 1 and 2 are
rhombic with g parameters, obtained by simulation
[25], gx=2.035, gy=2.070 and gz=2.140 (complex 1)
and gx=2.045, gy=2.095 and gz=2.200 (complex 2).
Complex 3 shows an axial spectrum with gÞ=2.054
and gꢁ=2.226. In good agreement with the most regu-
lar square-planar polyhedron of complex 1, its gz value
is the lowest [26].
From the EHMO calculations several interesting as-
pects can be deduced. (i) The SOMOs (semioccupied
molecular orbital) are antibonding orbitals. In all the
complexes, the dxy orbital of the Cu(II) has a contribu-
tion to SOMO formation of 43%. Moreover, in the
complexes 2 and 3 there is a small involvement (4%) of
the 4pz orbitals. The 2px and 2py orbitals of the nitro-
gen atoms of the ligands are involved in all the SOMOs
with a participation of 7%. The energy of the SOMO
orbital for complex 1 is −10.086 eV; for the complexes
2 and 3 it is −11.036 and −11.004 eV, respectively.
Hence, it seems that there is a correlation between the
degree of tetrahedral distortion and the stability of the
SOMO, higher tetrahedral distortion leading to higher
stability of the SOMO. (ii) In complex 1 the four
following molecular orbitals present the only contribu-
tion of the d orbitals of the Cu(II) ion while in the more
distorted complexes 2 and 3 the HOMO and HOMO-1
exhibit participation of the 2px and 2py orbitals of the
nitrogen atoms of the ligands. (iii) The energy differ-
ence between SOMO and HOMO for the square-planar
complex 1 is 3.710 eV, this difference for the complexes
2 and 3 is 2.345 and 2.475 eV, respectively. Thus, it can
be deduced that the electronic transition in complex 1
must be more energetic than in the complexes 2 and 3.
3.3. Molecular orbital calculations
In order to investigate the electronic structure of the
three complexes we carried out extended Hu¨ckel molec-
ular orbital (EHMO) calculations by means of the
CACAO program [24]. As the systems are so complicated
it is difficult to obtain results that can be correlated to

L. Gutierrez et al. / Polyhedron 20 (2001) 703–709
709
[5] V. Ravichandran, K.K. Chacko, A. Aoki, H. Yamazaki, J.
Ruiz-Sanchez, J. Suarez-Varela, J.D. Lopez-Gonzalez, J.M.
Salas-Peregrin, E. Colacio-Rodriguez, Inorg. Chim. Acta 173
(1990) 107.
[6] J. Casanova, G. Alzuet, S. Ferrer, J. Latorre, J.A. Ramirez, J.
Borra´s, Inorg. Chim. Acta 304 (2000) 170.
These results are consistent with the electronic spectra
where the d–d band of complex 1 appears near 20 000
cm−1 while in compounds 2 and 3 it is found at about
16 000 cm−1
.
[7] J. Casanova, G. Alzuet, J. Latorre, J. Borra´s, Inorg. Chem. 36
(1997) 2052.
4. Supplementary material
[8] L. Gutierrez, G. Alzuet, J.A. Real, J. Cano, J. Borra´s, A.
Castin˜eiras, Inorg. Chem. 39 (2000) 3608.
[9] CAD-4 Express Software, Version 5.1/1.2, Enraf–Nonius, Delft,
The Netherlands, 1994.
[10] M. Kretschmar, GENHKL Program for the Reduction of CAD-4
Diffractometer Data, University of Tu¨bingen, Germany, 1997.
[11] A.C.T. North, D.C. Phillips, F.S. Mathews, Acta Crystallogr.,
Sect. A 24 (1968) 351.
[12] G.M. Sheldrick, Acta Crystallogr., Sect. A 46 (1990) 467.
[13] G.M. Sheldrick, SHELXL-97. Program for the Refinement of
Crystal Structures, University of Go¨ttingen, Germany, 1997.
[14] International Tables for X-ray Crystallography, vol. C, Kluwer,
Dordrecht, 1995.
Supplementary crystallographic data have been de-
posited with the Cambridge Crystallographic Data
Centre, deposition numbers CCDC 150109, CCDC
150110, CCDC 150111. Copies of this information may
be obtained free of charge from The Director, CCDC,
12 Union Road, Cambridge CB2 1EZ, UK (fax: +44-
1223-336033; e-mail: deposit@ccdc.cam.ac.uk or www:
http://www.ccdc.cam.ac.uk).
[15] A.L. Spek, PLATON, A Multipurpose Crystallographic Tool,
Utrecht University, Utrecht, The Netherlands, 1998.
[16] CAD-4 Software, Enraf–Nonius, Delft, The Netherlands, 1996.
[17] P. Mcardle, Absen, J. Appl. Crystallogr. 29 (1996) 306.
[18] PROFIT, Profile Fitting Data Reduction. (a) M.S. Lehman, F.K
Larsen, Acta. Crystallogr., Sect A 30 (1974) 580. (b) V.A
Strel’tsov, V.E. Zavodnik, Sov. Phys. Crystallogr. 34 (1989) 824.
(c) V.A. Strel’tsov, V.E. Zavodnik, Sov. Phys. Crystallogr. 35
(1990) 281.
[19] A. Altomare, G. Cascarano, C. Giacovazzo, A. Guagliardi,
SIR-92 a program for crystal structure solution, J. Appl. Crystal-
logr. 26 (1993) 343.
[20] G.M. Sheldrick, SHELXL-93, Program for Crystal Structure
Refinement, University of Go¨ttingen, Germany, 1993.
[21] K. Harms, S. Wocadlo, XCAD-4-CAD-4 Data Reduction, Univer-
sity of Marburg, Germany, 1995.
Acknowledgements
G.A. and J.B. would like to thank Spanish CICYT
(PM97-0105-01-CO2-01) and Generalitat Valenciana
(GV-D-CN-09-145-96) for financial support. A.C.
thanks the Xunta de Galicia (Project XUGA
20309B97). M.L. and F.S thank the S.C.S.I.E. (X-ray
section) of the University of Valencia for provision of
the X-ray crystallographic facilities.
References
[22] L.J. Farrugia, ORTEP-3 for Windows, J. Appl. Crystallogr. 30
(1997) 565.
[1] B.J. Hathaway, in: R.D. Gillard, J.A. McCleverty (Eds.), Com-
prehensive Coordination Chemistry, Pergamon, New York,
1987, ch. 9.
[2] C. Ramakrishnan, Y.S. Geetha, Proc. Indian Acad. Sci. (Chem.
Sci.) 102 (1990) 481.
[23] PARST. (a) M. Nardelli, Comput. Chem. 7 (1983) 95. (b) M.
Nardelli, J. Appl. Crystallogr. 28 (1995) 659.
[24] C. Mealli, D. Proserpio, Computer Aided Composition of
Atomic Orbitals (CACAO program) PC version, July 1992. See
also: J. Chem. Edu. 67 (1990) 399.
[3] R.H. Holm, P. Kennepohl, E.I. Solomon, Chem. Rev. 96 (1996)
2239.
[25] WINEPR-Simfonia, 1.25, Bruker Analytik GmbH, Karlsruhe,
Germany, 1994–1996.
[4] L.P. Battaglia, A. Bonamartini-Corradi, G. Marcotrigiano, L.
Menabue, G.C. Pellacani, Inorg. Chem. 18 (1979) 148.
[26] A. Goodman, J.B. Raynor, Adv. Inorg. Chem. Radiochem. 13
(1970) 135.
.