Ni5, Ni8, and Ni10 clusters with 2,6-diacetylpyridine-dioxime as a ligand

Article abstract of DOI:10.1021/ic200895q

In the present work, novel coordination possibilities for the system dapdoH₂/Ni^II (dapdoH₂ = 2,6-diacetylpyridine- dioxime) have been explored. Depending on the starting reagents and solution conditions, several clusters w

Full text of DOI:10.1021/ic200895q

ARTICLE
pubs.acs.org/IC
Ni5, Ni8, and Ni10 Clusters with 2,6-Diacetylpyridine-dioxime as a
Ligand
Albert Escuer,*,† Jordi Esteban,† and Olivier Roubeau‡
†Departament de Química Inorgꢀanica and Institut de Nanociꢀencia i Nanotecnologia de la Universitat de Barcelona (IN2UB),
Martí i Franquꢁes 1-11, 08028 Barcelona, Spain
‡Instituto de Ciencia de Materiales de Aragꢁon (ICMA), CSIC and Universidad de Zaragoza, Departamento de Física de la Materia
Condensada, Pedro Cerbuna 12, 50009 Zaragoza, Spain
S Supporting Information
b
ABSTRACT: In the present work, novel coordination possibilities
for the system dapdoH2/NiII (dapdoH2 = 2,6-diacetylpyridine-
dioxime) have been explored. Depending on the starting reagents
and solution conditions, several clusters with nuclearities ranging
from Ni5 to Ni10 were achieved and structurally characterized,
namely, [Ni5(R-COO)2(dapdo)2(dapdoH)2(N(CN)2)2(MeOH)2]
in which R-COOꢀ = benzoate (1) or 3-chlorobenzoate (2), [Ni8-
(dapdo)4(NO3)4(OH)4(MeOH)4] (3), and [Ni10(dapdo)8(N-
(CN)2)2(MeO)(MeOH)](NO3) (4). For the first time, pentadentate coordination for the dapdo2ꢀ ligand has been established.
All compounds show a combination of square-planar and octahedrally coordinated nickel atoms. According to the Ni2(sp)Ni3(Oh)
(1 and 2), Ni4(sp)Ni4(Oh) (3), and Ni4(sp)Ni6(Oh) (4) environments, these systems magnetically behave as trimer, tetramer, and
hexanuclear clusters, respectively. dc magnetic measurements in the 2ꢀ300 K range of temperature reveal antiferromagnetic
coupling for all compounds, and the correlation of the superexchange interaction with the torsion angles involving the oximato
bridges is experimentally confirmed.
’ INTRODUCTION
Within this family of linkers, 2,6-diacetylpyridine-dioxime
(dapdoH2) is the most studied among the few related ligands
that have been reported to date,1 such as 2,6-pyridinedioxime
(pdoH2) or pyridine-2,6-diamidoxime (pdamoH2) (Scheme 1).
The most common coordination mode of these LH2, LHꢀ, or
L2ꢀ ligands is the 1.00111 mode (Harris notation, referred to as
X.Y1Y2Y3...Yn, where X is the overall number of metals bound by
the whole ligand and each value of Y refers to the number of metal
ions attached to the different donor atoms. The ordering of Y is
listed by the CahnꢀIngoldꢀPrelog priority rules, hence here O
before N),8 in which the tridentate coordination of the three
At present, research based on the use of oximes in coordina-
tion chemistry is a growing field. 2-Pyridyl oximes, {py}C(R)-
NOH, are well-known ligands in this area due to their ability to
generate stable first-row transition coordination compounds
with a large range of nuclearities.1 These molecules are very
versatile and able to act as bidentate ligands in their protonated
state or to link up to three metallic centers in their deprotonated
anionic form. In addition, the donor properties of the {py}C-
(R)NOH ligands can be tuned according to the nature of the R
group (H, Me, Ph, py, ꢀNH2, etc.). Self-assembly of nickel-
{py}C(R)NOꢀ fragments have yielded a large number of medium-
high nuclearity clusters, as for example, Ni7,2 Ni8,3 Ni9,4 Ni10,5
Ni12, or Ni14,3,6 exhibiting, in some cases, slow relaxation of
magnetization.7
One of the synthetic challenges in the search of high nuclearity
systems is the design of ligands able to stabilize large nuclearities
and/or generate new topologies in order to improve the desired
properties. Regarding this matter, pyridyldioximato ligands
(LH2, with R = various) (Scheme 1) are attractive ligands for
the achievement of polynuclear clusters because the three
nitrogen atoms give an excellent chelate that easily coordinates
one metallic center, whereas the two ortho-oximato groups are
able to coordinate at both sides of the central cation up to four
additional cations as a function of the degree of deprotonation of
the ligand.
nitrogen atoms yields octahedral mononuclear [MII(LH2)2]2ꢀ 9
,
[MII(LH)2],10 or [MIV(L)2]11 complexes or plays the role of
terminal ligand in a number of mononuclear12 or polynuclear9c,13
derivatives bridged by other ligands, such as halides, pseudoha-
lides, or carboxylates.
Larger nuclearities have been characterized, mainly in the very
recent years, allowing the characterization of an increasing
number of coordination modes. After the early characterization
of the LHꢀ 2.10111 mode in the double oximato bridged CuII
complex14 with the formula [Cu2(dapdoH)2](BF4)2, several
coordination modes have been reported for the deprotonated
dapdo2ꢀ ligand (L2ꢀ 3.11111/4.21111) or 3.20111 for LHꢀ in
Received: April 28, 2011
Published: August 19, 2011
r
2011 American Chemical Society
8893
dx.doi.org/10.1021/ic200895q Inorg. Chem. 2011, 50, 8893–8901
|

Inorganic Chemistry
ARTICLE
Scheme 1. Reported LH2 Pyridyldioxime Ligands
by dissolving equimolar quantities (40 mmol) of benzoic acid
(or 3-Cl-benzoic acid) and NaOH in 40 mL of H2O, filtering, and
mixing the final solution with a commercial source of Ni(NO3)2 6H2O
3
(20 mmol) in 20 mL of water. The resulting nickel salt was obtained in
good yield (>80%). DapdoH2 was prepared following the C. W. Glynn
and M. M. Turnbull method.9a
[Ni5(RCOO)2(dapdo)2(dapdoH)2(N(CN)2)2(MeOH)2] RCOOꢀ = benzo-
ate (1) or 3-Cl-benzoate (2). dapdoH2 (0.193 g, 1 mmol), Ni(BzO)2
3
3H2O (0.709 g, 2 mmol) or Ni(3-Cl-BzO)2 3H2O (0.847 g, 2 mmol),
3
and Na(N(CN)2)2 (0.178 g, 2 mmol) were dissolved in 20 mL of
MeOH, and NEt3 (0.202 g, 2 mmol) was added. The mixture was stirred
for 2 h and then filtered. Crystals were obtained by layering the final
solution with 10 mL of diethylether. Anal. Calcd for C56H54N18Ni5O14
(1): C, 44.88; H, 3.77; N, 16.82%. Found: C, 44.10; H, 3.67; N, 16.65%.
Anal. Calcd for C56Cl2H52N18Ni5O14 (2): C, 42.91; H, 3.47; N, 16.09%.
Found: C, 42.31; H, 3.39; N, 15.85%. Relevant IR bands (cmꢀ1): 3432
(b), 2257 (s), 2216 (m), 2156 (s), 1594 (m), 1534 (m), 1512 (m), 1490
(m), 1377 (m), 1203 (s), 1153 (m), 1122 (m), 1087 (m), 1065 (m), 807
(w), 724 (w) for 1 and 3413 (b), 2258 (s), 2215 (m), 2156 (s), 1592
(m), 1558 (m), 1484 (m), 1407 (m), 1372 (s), 1263 (m), 1154 (m),
1086 (m), 1060 (m), 813 (w), 765 (w) for 2.
Scheme 2. Coordination Modes for dapdoHꢀ or dapdo2ꢀ
Ligands Found in Compounds 1ꢀ4a
[Ni8(dapdo)4(NO3)4(OH)4(MeOH)4] 7MeOH (3 7MeOH). Solid
3
3
dapdoH2 (0.193 g, 1 mmol) was dissolved in 20 mL of MeOH
together with Ni(NO3)2 6H2O (0.581 g, 2 mmol) and NEt3 (0.202
3
g, 2 mmol). The solution was stirred at room temperature for a
couple of hours, filtered, and crystallized by layering with 10 mL of
diethylether. Anal. Calcd for C40H56N16Ni8O28 (3): C, 28.62; H,
3.36; N, 13.35%. Found: C, 27.89; H, 3.55; N, 13.00%. Relevant IR
bands (cmꢀ1): 3346 (b), 1630 (w), 1591 (m), 1519 (m), 1493 (m),
1407 (s), 1384 (s), 1220 (s), 1192 (m), 1167 (w), 1131 (w), 1089
(w), 809 (m), 701 (w).
[Ni10(dapdo)8(N(CN)2)2(MeO)(MeOH)](NO3) 3MeOH (4 3MeOH).
dapdoH2 (0.193 g, 1 mmol), Ni(NO3)2 6H2O (0.581 g, 2 mmol), and
NaN(CN)2 (0.178 g, 2 mmol) were dissolved in 20 mL of MeOH
together with NEt3 (0.202 g, 2 mmol). The solution was stirred for 2 h
and then filtered. Crystals were obtained by layering the final solution
with 10 mL of diethylether. Anal. Calcd for C81H91N31Ni10O24
3
3
a The novel coordination mode 5.22111 has been observed for the first
time in this work.
3
one mixed valence Fe3 complex,9d several MnII MnIII and
2
4
one MnII MnIII6 cluster,15 or two heterometallic CuII/CrIII and
2
(4 3MeOH): C, 39.39; H, 3.71; N, 17.58%. Found: C, 38.58; H,
3
MnIV/GdIII systems.16 Our recent contribution to the knowledge
of the properties of this kind of ligands comprised CuIIꢀpda-
moH2 derivatives,17 the first NiIIꢀdapdoH2 derivatives,18 and
3.52; N, 17.94%. Relevant IR bands (cmꢀ1): 3442 (b), 2267 (w),
2227 (w), 2159 (m), 1637 (m), 1592 (m), 1534 (w), 1384 (s), 1231 (w),
1205 (m), 1155 (m), 1125 (m), 1087 (m), 1086 (m), 1046 (m), 790 (w).
Physical Measurements. Magnetic susceptibility measurements
were carried out on polycrystalline samples with a DSM5 Quantum
Design susceptometer working in the range of 30ꢀ300 K under
magnetic fields of 0.3 T and under a field of 0.03 T in the 30ꢀ2 K
range to avoid saturation effects. Diamagnetic corrections were estimated
fromPascaltables. Infraredspectra (4000ꢀ400 cmꢀ1) were recorded from
KBr pellets on a Bruker IFS-125 FT-IR spectrophotometer.
one novel MnII MnIII2 dapdoH2 complex15c in which the modes
6
2.10111/3.11111/3.20111 and 2.10111/3.11111/3.20111/4.21111
were found for LHꢀ and L2ꢀ, respectively.
These previously reported complexes show how the increase
of nuclearity is closely related to the deprotonation of both
oximato arms, reaching the larger nuclearity reported until now
(Mn8) for the L2ꢀ 4.21111 coordination mode.15
Following our work on pyridyldioximate ligands, we now
report a series of Ni5 (1 and 2), Ni8 (3), and Ni10 (4) new clusters
containing dapdoHꢀ and dapdo2ꢀ ligands. All of them exhibit
nickel centers in both octahedral or square-planar coordination
environments in the same compound. For the first time, the
coordination mode 5.22111 has been characterized for this kind
of ligand, and larger nuclearity (M10) is achieved (Scheme 2).
Syntheses, structures, and magnetic behavior of 1ꢀ4 are de-
scribed in the following sections.
X-ray Crystallography. Data for compounds 1 and 2 were collected
on red blocks at 150 K and λ = 0.7383 Å both using a single-axis HUBER
diffractometer on station BM16 of the European Synchrotron Radiation
Facility, Grenoble, France. Cell refinement, data reduction, and absorption
corrections were done with the HKL-2000 suite.19 The structures were
solved with SIR92,20 and the refinement and all further calculations were
carried out using SHELXL-97.21 Data for compounds 3 and 4 were
collected at 100 K on, respectively, a red plate and an orange plate both
on a Bruker X8 Kappa APEX II diffractometer at the Unidade de Raios X,
RIAIDT, University of Santiago de Compostela, Spain. The structures were
solved by direct methods and refined on F2 using the SHELX-TL suite.21
All non-hydrogens were refined anisotropically, whereas hydrogens
were placed geometrically on their carrier atom and refined with a riding
model where possible.
’ EXPERIMENTAL SECTION
Syntheses. 2,6-Diacetylpyridine, NaN(CN)2, and Ni(NO3)2
3
6H2O were purchased from Sigma-Aldrich Inc. and used without further
purification. Ni(BzO)2 3H2O and Ni(3-Cl-BzO)2 3H2O were synthesized
In the case of 1, one strong electron density peak remained close to
one phenyl ring and could not be included in the structural model and
3
3
8894
dx.doi.org/10.1021/ic200895q |Inorg. Chem. 2011, 50, 8893–8901

Inorganic Chemistry
ARTICLE
Table 1. Crystal Data and Structure Refinement for Compounds 2ꢀ4
(2)
(3)
(4)
C78H79N31Ni10O21 3MeOH
formula
fw
C
56Cl2H54N18Ni5O14
C40H48N16Ni8O28 7MeOH
3
3
1567.62
P21/n
16.980(4)
11.613(3)
17.846(4)
90
1902.95
P1
2469.95
C2/c
space group
a/Å
11.261(2)
12.292(3)
13.577(3)
86.48(1)
67.61(1)
84.67(1)
1729.4(6)
1
15.335(3)
33.125(7)
21.821(4)
90
b/Å
c/Å
R/deg
β/deg
γ/deg
V/Å3
118.23(3)
90
108.18(3)
90
3101(2)
2
10531(4)
4
Z
T, K
150(2)
0.73830
1.679
100(2)
0.71073
1.666
100(2)
0.71073
1.558
λ (Mo KR), Å
F
calc, g cmꢀ3
3
μ (Mo KR), mmꢀ1
R [I > 2s(I)]
wR [all data]
S [all data]
1.832
2.433
1.826
0.0389
0.1113
1.091
0.0584
0.1600
1.050
0.0562
0.1576
1.054
both R1 and wR2 factors remained very high at the end of the refinement,
while unreasonably high EXTI and WEIGHT parameters were neces-
sary to reach convergence. We believe the problem lies in either or both
of the following: (i) strong reflections were not well treated and (ii)
absorption corrections were inadequate, possibly also due to problems
with strong reflections. Because compound 1 is isosutructural with
compound 2, only the structure of the latter is reported here in detail.
For compound 2, the terminal N(6) nitrogen atom of the dicyana-
mide ion was highly disordered. Splitting of the atom over two positions
was considered, but it did not improve the model, both half N atoms
remaining highly disordered. N6 was thus refined with one sole site and
displacement parameter restraints. All hydrogens were found in differ-
ence Fourier maps, and those on the oxime oxygen O(2) and methanol
oxygen O(7) were refined freely with their thermal parameters 1.5 times
that of their carrier O.
For compound 3, hydrogens on the hydroxide oxygens O(3) and O(4)
and on the coordinated methanol oxygens O(5) and O(8) were found in
successive difference Fourier maps and refined with their thermal
parameters 1.2 times that of their carrier oxygen and a soft distance
restraint. Together with the four dapdo2ꢀ and four-coordinated nitrate,
this clearly points at a neutral main complex. The solvent area was
particularly disordered. After locating one methanol molecule (O1S),
the remaining electron density peaks (max. ca. five electrons) occupying
a rather small void of ca. 300 Å3 could not be modeled satisfactorily (see
CIF for details). The disordered area was thus analyzed and taken into
account with PLATON/SQUEEZE that recovered a total of ca. 99
electrons per cell all in one void of ca. 275 Å3. The combination of
occupied volume and electrons would account reasonably with five
additional lattice methanol molecules per cell, which have been included
in the formula and related structural parameters.
a difference Fourier map and refined with its thermal parameter 1.5 times
that of O(9) and a distance restraint. Hydrogens on the lattice methanol
molecules were omitted. At the end of the refinement, there remained
areas in the structure with only weak electron density peaks that could
not be modeled satisfactorily as solvent molecules. This was, therefore,
analyzed and taken into account by PLATON/SQUEEZE22 that
recovered, per cell, four groups of ca. 20/70 electrons in voids of 103/
267 Å3, respectively. These figures altogether would agree with the
presence of 4 methanol and 4 diethylether diffuse molecules in addition
to the 12 MeOH per cell already in the structural model.
Crystallographic and experimental details for 2ꢀ4 are summarized in
Table 1, whereas experimental details of 1 are provided in Table S1 and
Figure S1 (Supporting Information). All data can be found in the
supplementary crystallographic data for this paper in CIF format with
CCDC numbers 817654-817657. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via www.
ccdc.cam.ac.uk/data_request/cif.
Plots for publication were generated with ORTEP3 for Windows and
plotted with POV-ray programs.23
’ RESULTS AND DISCUSSION
Syntheses. In our previous work,18 we studied the reactivity of
the Ni2+/dapdoH2/R-COOꢀ system in a basic medium and
several tri- and tetranuclear systems containing oximato and
carboxylato bridges where reported, and different coordination
modes for dapdoH2, dapdoHꢀ, or dapdo2ꢀ were characterized.
The presence of labile solvent molecules in these compounds
suggested the possibility to grow their nuclearity or dimension-
ality by means of the adequate bridging ligands. On the other
hand, it was also envisaged the possibility to generate novel
“empty” coordination sites by substitution of the carboxylate
ligands by less coordinating anions. With this aim, we have
explored the systematic reaction of nickel carboxylates with
dapdoH2 and additional bridging ligands, such as azide, dicya-
namide, or thiocyanate. When sodium dicyanamide was present
in the reaction medium, crystalline pentanuclear compounds 1
and 2 and decanuclear 4 were obtained in good yield. However,
In the case of 4, the terminal CN group of the dicyanamide ion was
highly disordered. It was considered splitting the two atoms, but the
partial atoms were still highly disordered. Therefore, C(20) and N(9)
were refined with displacement parameter restraints, and their remaining
high max/min ratios likely correspond to their real disorder. One of the
lattice methanol molecules was only half-occupied. The coordinated
methanol molecule is, in fact, half methanol and half methanoate for
charge compensation. The corresponding half-occupied hydroxyl hy-
drogen H(9) forming a hydrogen bond with the nitrate ion was found in
8895
dx.doi.org/10.1021/ic200895q |Inorg. Chem. 2011, 50, 8893–8901

Inorganic Chemistry
ARTICLE
in these compounds, the dicyanamide ligand acts as a terminal
ligand and does not provide the expected linkage between
polynuclear units. In contrast, reaction in the same synthetic
conditions starting from nickel benzoates and sodium azide
yields a mixture of dark crystals of the already reported11 mono-
nuclear NiIV complex [Ni(dapdo)2] containing two deproto-
nated dapdo2ꢀ ligands and red needles for which structural
characterization has been unsuccessful until now. The presence
of coordinated azide in its end-on coordination mode (checked
by IR spectroscopy) and the ferromagnetic response of these
systems suggest the probable formation of azido-containing
clusters, and efforts to reach their full structural characterization
are in progress.
of the NiII cation to the d6 low-spin NiIV oxidation state (e.g.,
[Ni(dapdo)2] and [Ni(dmg)3]2ꢀ, where dmg2ꢀ stands for dim-
etylglioximato).24 The square-planar environment is common
for NiII atoms linked to several deprotonated oximato groups as
in glioximato derivatives. However, pyridyloximato ligands give
hexacoordination systematically with the only exception of the
amidoxime function attached to pyridyl, pyrazyl, or pyimidinic
rings, which, as in our case, give complexes in which tetra- and
hexacoordination have been characterized simultaneously in the
same compound.3,6b,25 In our previous paper, we have reported
how coordination of only one 3.11111 dapdo2ꢀ ligand it is not
enough to favor the oxidation of NiII to NiIV but stabilizes the
square-planar environment around the nickel centers.
In agreement with these previous data, compounds 1ꢀ4
exhibit square-planar coordination for those nickel atoms linked
to the three N atoms of one 3.11111 dapdo2ꢀ ligand. In contrast,
characterization of the novel 5.22111 coordination mode shows
an octahedral environment for the nickel atom coordinating the
three N atoms of dapdo2ꢀ. This feature suggests an important
change in the electronic density and the reduction of the crystal
field of the ligand due to the coordination of a second metallic
atom to the oximato group at the limit between square-planar
and octahedral environments.
On the other hand, the change from carboxylato anions to
nitrate ones yielded the crystalline compounds 3 and 4, which
show larger nuclearity and new topologies clearly different than
the carboxylato-containing complexes, suggesting a rich noncar-
boxylato chemistry for this ligand.
The coordination behavior of the deprotonated form dapdo2ꢀ
bonded to Ni2+ atoms is remarkable. Strong spherical crystal
fields, provided by the oximato groups,24 favor the easy oxidation
Description of the Structures. [Ni5(3-ClBzO)2(dapdo)2-
(dapdoH)2(N(CN)2)2(MeOH)2] (2). A labeled plot of the neutral
centrosymmetric pentanuclear unit present in compound 2 is
shown in Figure 1. Selected bond parameters are listed in Table 2.
The pentanuclear units consist of two tetracoordinated nickel
atoms Ni(2) and symmetry related Ni(20) and three hexacoor-
dinated nickel atoms, Ni(1), Ni(10), and Ni(3), which are linked
by the oximato groups of four ligand molecules. Each tetracoor-
dinated cation Ni(2) is bonded to one 3.11111 dapdo2ꢀ
molecule by its three N atoms and linked to one O-oximato
atom from one neighbor dapdoHꢀ ligand, resulting in a distorted
square-planar environment. The coordination sphere of the
Ni(1) cation is formed by the three N atoms of one 3.20111
dapdoHꢀ ligand, one O-oximato atom from one neighbor
dapdo2ꢀ ligand, one O atom from one monocoordinated
benzoate group, and one N atom from one dicyanamide anion.
Finally, the central Ni(3) atom is linked by four O-oximato
groups (from two dapdo2ꢀ and two dapdoHꢀ ligands) and by
two trans-methanol molecules.
Figure 1. Labeled POV-ray plot of complex 2. Ni atoms in an
octahedral or square-planar environment are plotted in green and orange
color, respectively. H atoms are omitted for clarity.
NiꢀN bond distances are in the 1.813(2)ꢀ2.104(3) Å range,
corresponding the shorter distances to the square-planar cations
Table 2. Selected Interatomic Distances (Å) and Angles (deg) for Compound 2
Ni(1)ꢀN(1)
1.983(2)
2.104(3)
2.075(2)
1.813(2)
1.891(2)
2.070 (2)
2.114(2)
Ni(1)ꢀN(2)
Ni(1)ꢀN(4)
Ni(1)ꢀO(5)
Ni(2)ꢀN(8)
Ni(2)ꢀO(1)
Ni(3)ꢀO(4)
2.070(2)
2.074(2)
2.035(2)
1.921(2)
1.881(2)
1.991(2)
Ni(1)ꢀN(3)
Ni(1)ꢀO(3)
Ni(2)ꢀN(7)
Ni(2)ꢀN(9)
Ni(3)ꢀO(1)
Ni(3)ꢀO(7)
Ni(1)ꢀN(2)ꢀO(1)
Ni(2)ꢀN(8)ꢀO(3)
Ni(2)ꢀO(1)ꢀN(2)
Ni(3)ꢀO(4)ꢀN(9)
Ni(2)ꢀO(1)ꢀNi(3)
Ni(1)ꢀN(2)ꢀO(1)ꢀNi(2)
Ni(2)ꢀN(8)ꢀO(3)ꢀNi(1)
124.8(1)
Ni(1)ꢀO(3)ꢀN(8)
Ni(1)ꢀN(3)ꢀO(2)
Ni(2)ꢀN(9)ꢀO(4)
Ni(3)ꢀO(1)ꢀN(2)
111.4(1)
126.4(2)
114.1(1)
116.6(1)
112.83(8)
31.4(2)
126.9(2)
125.1(1)
116.9(1)
Ni(1)ꢀN(2)ꢀO(1)ꢀNi(3)
Ni(2)ꢀN(9)ꢀO(4)ꢀNi(3)
103.3(2)
6.4(2)
40.7(2)
8896
dx.doi.org/10.1021/ic200895q |Inorg. Chem. 2011, 50, 8893–8901

Inorganic Chemistry
ARTICLE
and being larger those provided by dapdoHꢀ than dapdo2ꢀ
ligands. NoximeꢀNiꢀNpyridyl angles deviate from 90° due to the
low bite angle of the ligand, being larger the angles generated by
the dapdo2ꢀ ligand (around 82°) than the angles that involve
monodeprotonated dapdoHꢀ ligands (around 77°). The torsion
angle corresponding to the Ni(1)ꢀN(1)ꢀO(2)ꢀNi(3) bridge
is surprisingly high, deviating only 13.3(2)° from orthogonality.
The two O atoms of the carboxylato anion participate in strong
intramolecular H bonds: the coordinated O(5) atom interacts
atoms (Ni(1), Ni(3), and symmetry related) are bonded to
one 3.11111 dapdo2ꢀ ligand by its three N atoms and to one μ3-
OH bridging group, exhibiting a distorted square-planar geome-
try. Hexacoordinated NiII atoms show a NiO6 environment and
can be described as central Ni(2) and Ni(2a) and the peripheral
Ni(4) and Ni(4a) groups. The central nickel atoms Ni(2) are
linked by double oximato/hydroxo bridges to Ni(1a) and Ni(3)
and by means of μ3-OH groups to Ni(1), Ni(2a), and Ni(4). The
coordination sphere of Ni(2) is completed with one methanol
molecule. The external Ni(4) atoms are linked by double
oximato/hydroxo bridges to Ni(3) and through a single oximato
bridge to Ni(1). Coordination sites around Ni(4) are completed
with two monodentate nitrato ligands and one methanol solvent
molecule.
with the methanol molecule with a O(7) O(5) distance of
3 3 3
2.835(3) Å, and the noncoordinated O(6) atom interacts with
the protonated oximate group with a O(6) O(2) distance of
3 3 3
2.635(3) Å. Aromatic rings of the dapdo2ꢀ and the chlorobenzo-
ate ligands give intercluster πꢀπ interactions with a distance
between centroids of 3.495(4) Å.
A set of intramolecular H bonds contribute to stabilize the
molecule: O(8) from one coordinated methanol molecule
interacts with O(1a) from one of the oximato groups with an
[Ni8(dapdo)4(NO3)4(OH)4(MeOH)4] 3MeOH,NEt3 (3). Fig-
3
ure 2 shows a labeled plot of the neutral centrosymmetric
compound 3, while Table 3 lists the selected bond parameters.
This octanuclear compound has four tetracoordinated and four
hexacoordinated nickel atoms. All four tetracoordinated NiII
(O(8) O(1a) distance of 2.589(7) Å) and with O(3) from
3 3 3
one of the hydroxo ligands with an (O(8) O(3) distance of
3 3 3
2.941(6) Å).
One of the O atoms from one coordinated nitrato ligand
interacts with the other hydroxo ligand with an O(11) O(4)
3 3 3
distance of 2.704(6) Å.
[Ni10(dapdo)8(N(CN)2)2(MeO)(MeOH)](NO3) 3MeOH (4). A
3
plot of the decanuclear compound 4 is shown in Figure 3. These
Figure 2. Labeled POV-ray plot of complex 3. Ni atoms in an
octahedral or square-planar environment are plotted in green and orange
color, respectively. O(10) and O(13) correspond to oxygen atoms from
coordinated nitrato ligands. H atoms are omitted for clarity.
Figure 3. Plot of complex 4. Ni atoms in an octahedral or square-planar
environment are plotted in green and orange color, respectively. H
atoms are omitted for clarity.
Table 3. Selected Interatomic Distances (Å) and Angles (deg) for Compound 3
Ni(1)ꢀN(1)
1.812(5)
1.902(6)
2.043(4)
2.060(4)
2.076(4)
1.790(5)
1.874(6)
2.027(4)
2.034(4)
2.088(4)
Ni(1)ꢀN(2)
1.885(5)
1.853(4)
2.121(4)
2.067(4)
2.031(4)
1.880(5)
1.868(4)
2.100(4)
2.075(4)
2.086(5)
Ni(1)ꢀN(3)
Ni(1)ꢀO(3a)
Ni(2)ꢀO(1)
Ni(2)ꢀO(3)
Ni(2)ꢀO(3a)
Ni(2)ꢀO(4)
Ni(2)ꢀO(5)
Ni(2)ꢀO(6)
Ni(3)ꢀN(4)
Ni(3)ꢀN(5)
Ni(3)ꢀN(6)
Ni(3)ꢀO(4)
Ni(4)ꢀO(2a)
Ni(4)ꢀO(4)
Ni(4)ꢀO(7)
Ni(4)ꢀO(8)
Ni(4)ꢀO(10)
Ni(4)ꢀO(13)
Ni(1a)ꢀO(3)ꢀNi(2)
Ni(2)ꢀO(1)ꢀN(2)
Ni(2)ꢀO(3)ꢀNi(2a)
Ni(2)ꢀO(4)ꢀNi(4)
Ni(4a)ꢀO(2)ꢀN(3)
Ni(4)ꢀO(10)ꢀN(7)
Ni(1)ꢀN(2)ꢀO(1)ꢀNi(2)
Ni(3)ꢀN(5)ꢀO(6)ꢀNi(2)
110.3(2)
Ni(1a)ꢀO(3)ꢀNi(2a)
Ni(2)ꢀO(6)ꢀN(5)
Ni(2)ꢀO(4)ꢀNi(3)
Ni(3)ꢀO(4)ꢀNi(4)
Ni(4)ꢀO(7)ꢀN(6)
Ni(4)ꢀO(13)ꢀN(8)
Ni(1)ꢀN(3)ꢀO(2)ꢀNi(4a)
Ni(3)ꢀN(6)ꢀO(7)ꢀNi(4)
114.0(2)
114.0(3)
95.5(2)
131.3(2)
124.5(4)
127.7(4)
10.0(6)
5.5(6)
113.0(3)
109.1(2)
105.9(2)
111.1(3)
127.9(5)
76.9(5)
18.9(6)
8897
dx.doi.org/10.1021/ic200895q |Inorg. Chem. 2011, 50, 8893–8901

Inorganic Chemistry
ARTICLE
units possess a C2 rotation axis that includes one NꢀO nitrato
bond and the two peripheral nickel atoms. Each cluster contains
six nonequivalent nickel atoms, organized as one inner {Ni4-
(dapdo2ꢀ)4} pseudocubane surrounded by four nickel atoms
distributed near each corner of the cube, and finally is capped by
two additional peripheral nickel atoms. Six of the nickel atoms are
hexacoordinated (inner cubane and peripheral ones), whereas
the remainder tetracoordinated nickel ions exhibit a square-
planar environment. The eight dapdo2ꢀ ligands are distributed
in two groups: four of them link the nickel atoms of the inner
cubane and adopt the unprecedented 5.22111 coordination
mode, in contrast with the four dapdo2ꢀ ligands linked to the
square-planar nickel atoms, which adopt the 3.11111 coordina-
tion mode. The two peripheral nickel atoms placed on the C2 axis
do not coordinate additional pyridyldioximato ligands.
terminal Ni(1) atom consists of four O-oximato atoms (from
two 5.22111 and two 3.11111 dapdo2ꢀ ligands) and two dicyana-
mides, giving a NiN2O4 environment, in contrast with Ni(6),
which exhibits a NiO6 environment from four oximato bridges
(two 5.22111 and two 3.11111 dapdo2ꢀ ligands) and one
metoxo and one methanol molecule.
Tetracoordinated Ni(2), Ni(5), and symmetry related atoms
show a square-planar environment. Each NiII atom is bonded to
one 3.1111 dapdo2ꢀ molecule by the three N atoms and to one
O-oximato group from another dapdo2ꢀ molecule (NiN3O
environment). Bond distances are between 1.79(1) and
1.935(7) Å, corresponding the shorter ones to the NiꢀN(ring)
bond. Bond angles deviate from the ideal 90° value due to the
small bite of the dapdo2ꢀ ligand.
The hexacoordinated Ni(3), Ni(4), and symmetry related
atoms form the inner [Ni4(NO)4] pseudocubane in which each
nonmetallic vertex has been substituted by one oximate bridge
(Figure 5). Each oximato group provides three edges and one
vertex of the pseudocube, resulting in four similar hexagonal
Ni2(NO)2 faces and two conventional Ni2O2 square faces, with
bond angles Ni(3)ꢀO(5)ꢀNi(3a) and Ni(4)ꢀO(4)ꢀNi(4a)
of 101.0(3)° and 101.5(3)°, respectively. NiꢀOꢀNꢀNi torsion
angles in the pseudocube are close to 70° in all cases. Ni(3) and
Ni(4) are bridged by one single oximato bridge to Ni(1) and
Ni(6), respectively, with a similar torsion angle close to 120°.
The anionic nitrate molecule interacts with the methanol/
methanoate ligands coordinated to Ni(6) via a multicentric H
bond in which the minimum distances of 2.65(1) and 2.814(9) Å
correspond to O(9) O(10) and O(9) O(9a), respectively.
A labeled plot of the core of the cationic decanuclear unit of 4
is depicted in Figure 4, and selected bond parameters are listed in
Table 4. The octahedral coordination environment for the
3 3 3
3 3 3
Magnetic Measurements and Modelization. Room-tem-
perature χMT values are 3.93 and 3.95 cm3 K molꢀ1, respectively,
Figure 4. Labeled POV-ray plot of the core of complex 4.
Table 4. Selected Interatomic Distances (Å) and Angles (deg) for Compound 4
Ni(1)ꢀO(1)
2.025(6)
2.106(6)
1.824(8)
1.924(7)
1.995(8)
2.187(7)
2.043(7)
2.005(8)
2.092(7)
2.064(6)
1.79(1)
Ni(1)ꢀN(7)
2.043(9)
Ni(1)ꢀO(3)
Ni(2)ꢀN(1)
Ni(2)ꢀN(2)
Ni(2)ꢀO(3)
Ni(3)ꢀN(5)
Ni(3)ꢀO(2)
Ni(3)ꢀO(5a)
Ni(4)ꢀN(11)
Ni(4)ꢀO(4)
Ni(4)ꢀO(4a)
Ni(5)ꢀN(14)
Ni(5)ꢀO(6)
Ni(6)ꢀO(8)
1.893(8)
1.847(6)
2.107(7)
2.077(6)
2.108(6)
2.175(7)
2.026(7)
2.125(6)
1.935(7)
1.843(7)
1.998(8)
Ni(2)ꢀN(3)
Ni(3)ꢀN(4)
Ni(3)ꢀN(6)
Ni(3)ꢀO(5)
Ni(4)ꢀN(10)
Ni(4)ꢀN(12)
Ni(4)ꢀO(7)
Ni(5)ꢀN(13)
Ni(5)ꢀN(15)
1.875(8)
2.067(6)
2.073(7)
Ni(6)ꢀO(6)
Ni(6)ꢀO(9)
Ni(3)ꢀO(5)ꢀNi(3a)
Ni(1)ꢀO(1)ꢀN(2)
Ni(2)ꢀO(3)ꢀN(5)
Ni(3)ꢀO(5)ꢀN(11)
Ni(4)ꢀO(7)ꢀN(14)
Ni(6)ꢀO(6)ꢀN(12)
Ni(1)ꢀO(1)ꢀN(2)ꢀNi(2)
Ni(2)ꢀO(3)ꢀN(5)ꢀNi(3)
Ni(2)ꢀN(3)ꢀO(2)ꢀNi(3)
Ni(3)ꢀN(6)ꢀO(4)ꢀNi(4a)
Ni(4)ꢀN(12)ꢀO(6)ꢀNi(5)
Ni(5)ꢀN(14)ꢀO(7)ꢀNi(4)
101.0(3)
Ni(4)ꢀO(4)ꢀNi(4a)
101.5(3)
118.9(5)
114.2(5)
112.0(5)
113.9(5)
124.3(5)
12.8(9)
37.4(7)
36.0(8)
69.6(6)
43.1(8)
33.4(9)
Ni(1)ꢀO(3)ꢀN(5)
123.7(5)
111.7(5)
111.5(5)
113.1(5)
117.9(6)
119.7(5)
45.0(6)
Ni(3)ꢀO(2)ꢀN(3)
Ni(4)ꢀO(4)ꢀN(6)
Ni(5)ꢀO(6)ꢀN(12)
Ni(6)ꢀO(8)ꢀN(15)
Ni(1)ꢀO(3)ꢀN(5)ꢀNi(3)
Ni(3)ꢀN(6)ꢀO(4)ꢀNi(4)
Ni(4)ꢀN(11)ꢀO(5)ꢀNi(3)
Ni(4)ꢀN(11)ꢀO(5)ꢀNi(3a)
Ni(4)ꢀN(12)ꢀO(6)ꢀNi(6)
Ni(5)ꢀN(15)ꢀO(8)ꢀNi(6)
45.6(7)
69.7(7)
117.0(6)
16.7(9)
8898
dx.doi.org/10.1021/ic200895q |Inorg. Chem. 2011, 50, 8893–8901

Inorganic Chemistry
ARTICLE
Figure 5. Pseudocube subunit of complex 4 generated by four dapdo2ꢀ
ligands. Each ligand provides three edges and one vertex of the
pseudocube.
Figure 7. Plot of the χMT product vs T for compounds 2 (diamonds)
and 4 (dot centered circles). The solid lines show the best fit of the
experimental data. Compounds 1 and 2 give practically equal magnetic
responses, and only the plot of 2 is shown for clarity.
Figure 8. Plot of the χMT product vs T for compound 3 (squares, left
axis) and χM vs T (dot centered circles, right axis). The solid lines show
the best fit of the experimental data in the 10ꢀ300 K range of
temperature.
Figure 6. Core of the bridges between paramagnetic centers of
compounds 1 and 2 (top), 3 (middle), and 4 (bottom). Nickel atom
numbering corresponds to the subindexes of the local spin carriers Sn
employed in the corresponding Hamiltonians.
for compounds 1 and 2, 4.82 cm3 K molꢀ1 for compound 3, and
7.39 cm3 K molꢀ1 for 4, in good agreement with structural data,
which reveals three, four, and six octahedral paramagnetic NiII
centers, respectively. Numbering of the paramagnetic centers
employed in the Hamiltonian expressions and the bridges
between these atoms are plotted in Figure 6.
susceptibility centered at 35 K (Figure 8). Compound 3 behaves
magnetically as a tetranuclear system with two well-differentiated
superexchange pathways (single or double hydroxo bridges with
different NiꢀOꢀNi bond angles). Simulation of the experimen-
tal data was thus performed using the CLUMAG program27 and
applying the Hamiltonian
Compounds 1 and 2 show a χMT value nearly constant
between 300 and 10 K, decreasing slightly at low temperature
down to a minimum value of 1.98 cm3 K molꢀ1 for 1 and
1.71 cm3 K molꢀ1 at 1.8 K (Figure 7). The fit of the experimental
data as a linear trinuclear system was calculated by means of the
MAGPACK program,26 for three local S = 1 spins derived from
the Hamiltonian
H ¼ ꢀJ1ðS2 S4 þ S2a S4aÞ ꢀ J2ðS2 S2aÞ
Best fit parameters were J1 = ꢀ24.6 cmꢀ1, J2 = ꢀ13.2 cmꢀ1, and
g = 2.302, with R = 3.6 ꢁ 10ꢀ5 (R = (χMTcalc ꢀ χMTobs)2/
(χMTobs)2.
3
3
3
The χMT plot for compound 4 decreases continuously on
cooling from the room temperature value of 7.39 cm3 K molꢀ1
.
2
The plot shows a small change of slope at 13 K, reaching a value
of 1.50 cm3 K molꢀ1 at 2 K. The χM plot does not exhibit a
maximum of susceptibility, and magnetization measurements
show a quasi saturated value equivalent to four electrons under
an external field of 5 T.
According to the coupling scheme of Figure 6, this system
behaves as a two-J cubane capped by two additional NiII atoms
linked by single oximato bridges. Bond parameters for the
H ¼ ꢀJðS1 S3 þ S3 S1aÞ þ DSz
3
3
Best fit parameters were J = ꢀ0.4(1) cmꢀ1, g = 2.279(2), and
D = ꢀ3.7(2) for compound 1 and J = ꢀ0.5(1) cmꢀ1, g = 2.285(2),
and D = ꢀ3.2(2) for complex 2.
The χMT plot for compound 3 decreases continuously on
cooling and tends to zero at low temperature. χM increases
from room temperature up to a well-defined maximum of
8899
dx.doi.org/10.1021/ic200895q |Inorg. Chem. 2011, 50, 8893–8901

Inorganic Chemistry
ARTICLE
oximato bridges between Ni(1) with Ni(3)/Ni(3a) and Ni(6)
with Ni(4)/Ni(4a) are very similar, and thus, to minimize the
number of coupling constants in the fitting process, we have
assumed greater symmetry than that experimentally found in the
structure. Simulation was performed by means of the CLUMAG
program27 applying the three-J Hamiltonian
calculated coupling constants provides experimental examples of
the predicted response of the NiꢀOꢀNꢀNi pathway with large
torsion angles.
’ ASSOCIATED CONTENT
S
Supporting Information. Crystallographic data files
b
H ¼ ꢀJ1ðS1 S3 þ S1 S3a þ S6 S4 þ S6 S4aÞ
3
3
3
3
(CIF format) for complexes 2ꢀ4, crystal data (Table S1), and
plot of compound 1 (Figure S1). This material is available free of
charge via the Internet at http://pubs.acs.org.
ꢀ J2ðS3 S3a þ S4 S4aÞ ꢀ J3ðS3 S4 þ S3 S4a
3
3
3
3
þ S3a S4 þ S3a S4aÞ
3
3
Best fit parameters were J1 = ꢀ4.8 cmꢀ1, J2 = ꢀ26.2 cmꢀ1
,
’ AUTHOR INFORMATION
J3 = ꢀ24.6 cmꢀ1, and g = 2.390 with R = 2.1 ꢁ 10ꢀ5
.
Corresponding Author
*E-mail: albert.escuer@ub.edu.
Correlations for the coupling in CuII or MnIII oximato bridged
systems have been well-established in the last recent years and
taking into account the orbitals of the NiII cation involved in the
superexchange interaction has been widely assumed a response
closer to CuII (decrease of the antiferromagnetic interaction with
the increase of the MꢀOꢀNꢀM torsion angle)28 than MnIII
(strong dependence of J with the torsion with even reversal of the
sign of the coupling constants for torsion angles around 30° in
triangular compounds).29 Very recently, on the basis of experi-
mental correlations on the NiꢀOꢀNꢀNi pathway, an inter-
mediate response between CuII and MnIII has been proposed,30
suggesting a decrease of the antiferromagnetic interaction for
increasing torsions up to around 75ꢀ80°, at which point the
switch to ferromagnetic interaction may be possible. The quasi
negligible values of J found for compounds 1 and 2 provide a nice
example of the magnetic response of the system NiꢀOꢀNꢀNi
with large torsion angles close to orthogonality. As was sug-
gested, this superexchange pathway experimentally reveals to
transmit a quasi negligible interaction in contrast with the well-
established medium-strong antiferromagnetic coupling widely
reported for planar or weakly distorted bridges.1
’ ACKNOWLEDGMENT
This work was supported by the CICYT projects CTQ2009-
07264. A.E. acknowledges the support of the ICREA-Academia
Research Award. The authors are grateful to Dr. G. Aromí,
Universitat de Barcelona, and to the Spanish MCI for facilitating
access to BM16 at ESRF (EXP16-01-739).
’ REFERENCES
(1) Milios, C. J.; Stamatatos, T. C.; Perlepes, S. P. Polyhedron 2006,
25, 134.
(2) Stamatatos, T. C.; Diamantopoulou, E.; Raptopoulou, C. P.;
Psycharis, V.; Escuer, A.; Perlepes, S. P. Inorg. Chem. 2007, 46, 2350.
(3) Ji, C.-M.; Yang, H.-J.; Zhao, C.-C.; Tangoulis, V.; Cui, A.-L.; Kou,
H.-Z. Cryst. Growth Des. 2009, 9, 4607.
(4) (a) Pajunen, A.; Mutikainen, I.; Saarinen, H.; Orama, M. Z.
Kristallogr. - New Cryst. Struct. 1999, 214, 217. (b) Khanra, S.; Weyhermuller,
T.;Rentschler, E.;Chaudhuri, P.Inorg. Chem. 2005, 44, 8176. (c) Stamatatos,
T. C.; Diamantopoulou, E.; Tasiopoulos, A.; Psycharis, V.; Vicente, R.;
Raptopoulou, C. P.; Nastopoulos, V.; Escuer, A.; Perlepes, S. P. Inorg. Chim.
Acta 2006, 359, 4149. (d) Stamatatos, T. C.; Papatriantafyllopoulou,
C.; Katsoulakou, E.; Raptopoulou, C. P.; Perlepes, S. P. Polyhedron 2007,
26, 1830.
Compound 4 contains two kinds of oximato bridges with
different torsion angles: large NiꢀOꢀNꢀNi torsions are found
for the bridges between the peripheral atoms and the central
cubane unit (117.0° and 119.7°) and lower torsions (around 45°
and 69°) inside the cubane. In agreement with the above general
trends, the found J values show weak antiferromagnetic coupling
for the bridges mediated by large torsion angles (ꢀ4.8 cmꢀ1) and
medium interactions with mean J values around ꢀ25 cmꢀ1 for
the less-distorted bridges.
The remainder of interactions in compound 4 and those found
in 3 follow the well-established correlations for NiꢀOꢀNi bond
angles with increasing antiferromagnetic interaction for larger
bond angles.26
(5) Psomas, G.; Dendrinou-Samara, C.; Alexiou, M.; Tsohos, A.;
Raptopoulou, C. P.; Terzis, A.; Kessissoglou, D. P. Inorg. Chem. 1998,
37, 6556.
(6) (a) Stamatatos, T. C.; Abboud, K. A.; Perlepes, S. P.; Christou, G.
Dalton Trans. 2007, 3861. (b) Papatriantafyllopoulou, C.; Jones, L. F.;
Nguyen, T. D.; Matamoros-Salvador, N.; Cunha-Silva, L.; Paz, F. A. A.;
Rocha, J.; Evangelisti, M.; Brechin, E. K.; Perlepes, S. P. Dalton Trans.
2008, 3153. (c) Stamatatos, T. C.; Escuer, A.; Abboud, K. A.; Raptopoulou,
C. P.; Perlepes, S. P.; Christou, G. Inorg. Chem. 2008, 47, 11825.
(7) Papatriantafyllopoulou, C.; Stamatatos, T. C.; Wernsdorfer, W.;
Teat, S. J.; Tasiopoulos, A.; Escuer, A.; Perlepes, S. P. Inorg. Chem. 2010,
49, 10486.
’ CONCLUSIONS
In the present work, we have reported a new series of NiII
clusters obtained using the dioximato ligand dapdoH2 in carbox-
ylato and noncarboxylato chemistry. The most relevant features
have been the characterization of the larger cluster reported until
now containing pyridyldioximato ligands and the new 5.22111
coordination mode characterized for the deprotonated form
dapdo2ꢀ, which spreads the picture of the coordination possibi-
lities of this kind of ligand. It becomes also relevant that, in
contrast with the well-known 3.11111 coordination mode that
systematically generates a square-planar coordination around the
NiII cations or even favors the easy oxidation to NiIV, the new
5.22111 mode stabilizes octahedral environments. Analysis of the
(8) Coxall, R. A.; Harris, S. G.; Henderson, D. K.; Parsons, S.;
Tasker, P. A.; Winpenny, R. E. P. J. Chem. Soc., Dalton Trans. 2000, 2349.
(9) (a) Glynn, C. W.; Turnbull, M. M. Transition Met. Chem. 2002,
27, 822. (b) Halcrow, M. A.; Kilner, C. A.; Wolowska, J.; McInnes,
E. J. L.; Bridgeman, A. J. New J. Chem. 2004, 28, 228. (c) Bovenzi, B. A.;
Pearse, G. A., Jr. J. Chem. Soc., Dalton Trans. 1997, 2793. (d) Vasilevsky,
I. V.; Stenkamp, R. E.; Lingafelter, E. C.; Rose, N. J. J. Coord. Chem. 1988,
19, 171.
(10) Salonen, M.; Saarinen, H.; Mutikainen, I. J. Coord. Chem. 2008,
61, 1462.
(11) (a) Sproul, G.; Stucky, G. D. Inorg. Chem. 1973, 12, 2898.
(b) Namli, H.; Azaz, A. D.; Karabulut, S.; C-Elen, S.; Kurtaran, R.; Kazak,
C. Transition Met. Chem. 2007, 32, 266.
8900
dx.doi.org/10.1021/ic200895q |Inorg. Chem. 2011, 50, 8893–8901

Inorganic Chemistry
ARTICLE
(12) (a) Nicholson, G. A.; Petersen, J. L.; McCormick, B. J. Inorg.
Chem. 1982, 21, 3274. (b) Vasilevsky, I. V.; Stenkamp, R. E.; Lingafelter,
E. C.; Schomaker, V.; Willett, R. D.; Rose, N. J. Inorg. Chem. 1989,
28, 2619. (c) Abboud, K. A.; Palenik, R. C.; Palenik, G. J. Acta Crystal-
logr., Sect. C 1994, C50, 525. (d) Abram, S.; Maichle-M€ossmer, C.;
Abram, U. Polyhedron 1997, 16, 2183. (f) Abram, S.; Maichle-M€ossmer,
C.; Abram, U. Polyhedron 1997, 16, 2291. (g) Singh, S. K.; Sharma, S.;
Dwivedi, S. D.; Zou, R.-Q.; Xu, Q.; Pandey, D. S. Inorg. Chem. 2008,
47, 11942.
(13) (a) Unni Nair, B. C.; Sheats, J. E.; Ponteciello, R.; Van Engen,
D.; Petrouleas, V.; Dismukes, G. C. Inorg. Chem. 1989, 28, 1582. (b)
Marsh, R. E. Inorg. Chem. 1990, 29, 572. (c) Escuer, A.; Cordero, B.;
Solans, X.; Font-Bardia, M.; Calvet, T. Eur. J. Inorg. Chem. 2008, 5082.
(14) Nicholson, G. A.; Petersen, J. L.; McCormick, B. J. Inorg. Chem.
1980, 19, 195.
(15) (a) Stamatatos, T. C.; Luisi, B. S.; Moulton, B.; Christou, G.
Inorg. Chem. 2008, 47, 1134. (b) Khanra, S.; Weyherm€uller, T.;
Chaudhuri, P. Dalton Trans. 2008, 4885. (c) Escuer, A.; Cordero, B.;
Font-Bardia, M.; Calvet, T.; Roubeau, O.; Teat, S. J.; Fedi, S.; Fabrizi di
Biani, F. Dalton Trans. 2010, 39, 4817.
(16) (a) Khanra, S.; Weyherm€uller, T.; Chaudhuri, P. Dalton Trans.
2007, 4675. (b) Lampropoulos, C.; Stamatatos, T. C.; Abboud, K. A.;
Christou, G. Inorg. Chem. 2009, 48, 429.
(17) Escuer, A.; Vlahopoulou, G.; Perlepes, S. P.; Font-Bardia, M.;
Calvet, T. Dalton Trans. 2011, 40, 225.
(18) Escuer, A.; Esteban, J.; Aliaga-Alcalde, N.; Font-Bardia, M.;
Calvet, T.; Roubeau, O.; Teat, S. J. Inorg. Chem. 2010, 39, 2259.
(19) Otwinowski, Z.; Minor, W. Methods in Enzymology; Carter,
C. W., Jr., Sweet, R. M., Eds.; Academic Press: New York, 1997; Vol. 276:
Macromolecular Crystallography, part A, pp 307ꢀ326.
(20) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G. L.;
Giacovazzo, C.; Guagliardi, A.; Polidori, G. J. Appl. Crystallogr. 1994,
27, 475.
(21) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112.
(22) Spek, A. L. J. Appl. Crystallogr. 2003, 36, 7.
(23) Ortep-3 for Windows: Farrugia, L. J. J. Appl. Crystallogr. 1997,
30, 565.
(24) Baucom, E. I.; Drago, R. S. J. Am. Chem. Soc. 1971, 93, 6469.
(25) (a) Kou, H.-Z.; An, G.-Y.; Ji, C.-M.; Wang, B.-W.; Cui, A.-L.
Dalton Trans. 2010, 39, 9604. (b) Gole, B.; Chakrabarty, R.; Mukherjee,
S.; Song, Y.; Mukherjee, P. S. Dalton Trans. 2010, 39, 9766. (c) An, G.-
Y.; Ji, C.-M.; Cui, A.-L.; Kou, H.-Z. Inorg. Chem. 2011, 50, 1079.
(26) Borras-Almenar, J. J.; Clemente-Juan, J. M.; Coronado, E.;
Tsukerblat, B. S. J. Comput. Chem. 2001, 22, 985.
(27) Gatteschi, D.; Pardi, L. Gazz. Chim. Ital. 1993, 123, 231.
(28) (a) Escuer, A.; Vlahopoulou, G.; Perlepes, S. P.; Font-Bardia,
M.; Calvet, T. Dalton Trans. 2011, 40, 225. (b) Ruiz, R.; Lloret, F.; Julve,
M.; Munoz, M. C.; Bois, C. Inorg. Chim. Acta 1994, 219, 179. (c)
Colacio, E.; Dominguez-Vera, J. M.; Escuer, A.; Klinga, M.; Kivekas, R.;
Romerosa, A. J. Chem. Soc., Dalton Trans. 1995, 343. (d) Dominguez-
Vera, J. M.; Colacio, E.; Escuer, A.; Klinga, M.; Kivek€as, R.; Romerosa, A.
Polyhedron 1997, 16, 281.
(29) (a) Milios, C. J.; Inglis, R.; Vinslava, A.; Bagai, R.; Wernsdorfer,
W.; Parsons, S.; Perlepes, S. P.; Christou, G.; Brechin, E. K. J. Am. Chem.
Soc. 2007, 129, 12505. (b) Inglis, R.; Jones, L. F.; Milios, C. J.; Datta, S.;
Collins, A.; Parsons, S.; Wernsdorfer, W.; Hill, S.; Perlepes, S. P.;
Piligkos, S.; Brechin, E. K. Dalton Trans. 2009, 3403.
(30) Palacios, M. A.; Mota, A. J.; Perea-Buceta, J. E.; White, F. J.;
Brechin, E. K.; Colacio, E. Inorg. Chem. 2010, 49, 10156.
8901
dx.doi.org/10.1021/ic200895q |Inorg. Chem. 2011, 50, 8893–8901