Monomeric and polymeric copper(II) hexaaza macrocyclic complexes with btc anions (btc=1,2,4,5-benzenetetracarboxylic acid)

Article abstract of DOI:10.1016/S0020-1693(02)01149-0

Two new copper(II) complexes with the composition [Cu(L)(btc^-)₂] (1) and [Cu(L)(btc^2-)]_n (2), where btc=1,2,4,5-benzenetetracarboxylic acid, L=3,10-bis(2-hydroxyethyl)-1,3,5,8,10,12-hexaazacyclotetradecane, have been synthesized and structurally characterized by a combination of analytical, spectroscopic, and crystallographic methods. The structure of 1 is made up of a macrocyclic copper(II) cation [Cu(L)]²⁺ and btc^- anions. The copper(II) coordination geometry in 1 exhibits an axially elongated octahedron with four nitrogen atoms from the macrocycle and two carbonyl oxygen atoms from the btc^- ligands. The structure of 2 shows a 1D coordination polymer, in which the copper(II) ions are bridged by the btc^2- anions.

Full text of DOI:10.1016/S0020-1693(02)01149-0

Inorganica Chimica Acta 342 (2003) 305Á310
/
www.elsevier.com/locate/ica
Note
Monomeric and polymeric copper(II) hexaaza macrocyclic complexes
with btc anions (btcꢀ1,2,4,5-benzenetetracarboxylic acid)
/
Jaeheung Cho a, Alan J. Lough b, Ju Chang Kim a,ꢁ
a Department of Chemistry, Pukyong National University, 559-1 Daeyeon 3-dong, Nam-gu, Pusan 608-737, South Korea
b Department of Chemistry, University of Toronto, Toronto, Ont., Canada M5S 3H6
Received 2 April 2002; accepted 27 May 2002
Abstract
Two new copper(II) complexes with the composition [Cu(L)(btcꢂ)2] (1) and [Cu(L)(btc2ꢂ)]n (2), where btcꢀ
benzenetetracarboxylic acid, Lꢀ3,10-bis(2-hydroxyethyl)-1,3,5,8,10,12-hexaazacyclotetradecane, have been synthesized and
/1,2,4,5-
/
structurally characterized by a combination of analytical, spectroscopic, and crystallographic methods. The structure of 1 is
made up of a macrocyclic copper(II) cation [Cu(L)]2ꢃ and btcꢂ anions. The copper(II) coordination geometry in 1 exhibits an
axially elongated octahedron with four nitrogen atoms from the macrocycle and two carbonyl oxygen atoms from the btcꢂ ligands.
The structure of 2 shows a 1D coordination polymer, in which the copper(II) ions are bridged by the btc2ꢂ anions.
# 2002 Elsevier Science B.V. All rights reserved.
Keywords: Crystal structures; Copper complexes; Macrocyclic ligand complexes; Benzenetetracarboxylic acid; Coordination polymer
1. Introduction
donors and/or hydrogen bond acceptors, affording the
possibilities of participation in intermolecular and/or
intramolecular hydrogen bonding interactions; (iii) the
COOH and/or the COOꢂ groups can be tilted from the
phenyl ring plane upon coordination to metal ions,
mainly due to the types of hydrogen bonding interac-
tions and steric hindrances, allowing rich coordination
modes. Although some metal complexes containing the
Transition metal complexes containing aromatic
polycarboxylate ligands have received considerable
current interest owing to their interesting structures
and potential applications [1Á3]. Macrocyclic complexes
/
with multi-connecting ligands which provide two or
more metal-binding sites such as aromatic polycarbox-
ylate ligands have been proved to be good building
blocks for the construction of coordination polymers
btc moieties have been reported [7Á9,13], the studies on
/
the metal complexes of polyaza macrocycles in this
family are still limited [14]. Reported herein, we describe
the syntheses and structures of 1 and 2 obtained from
the reactions between [Cu(L)Cl2] and btc.
and multi-dimensional supramolecular networks [2,4Á
/
10]. Among the various aromatic polycarboxylate
ligands, btc is especially of interest for the investigation
of complexes with unusual coordination modes or the
construction of complexes with higher dimensions since
it has following interesting features [9,11,12]: (i) btc
contains four COOH groups which can be fully or
partially deprotonated, resulting in a versatile coordina-
tion behavior to metal ions; (ii) the COOH and the
COOꢂ groups in the btc moieties can be hydrogen bond
2. Experimental
2.1. Materials and methods
All chemicals used in this work were of reagent grade
and were used without further purification. Infrared
spectra were measured as Nujol mulls between KBr
plates using a PerkinÁ
spectrophotometer over the range 4000 and 400 cmꢂ1
UVÁVis diffuse reflectance spectra using samples di-
/
Elmer Paragon 1000 FT IR
ꢁ Corresponding author. Tel.: ꢃ
8147
E-mail address: kimjc@pknu.ac.kr (J.C. Kim).
/
82-51-620 6382; fax: ꢃ82-51-628
/
.
/
0020-1693/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 0 - 1 6 9 3 ( 0 2 ) 0 1 1 4 9 - 0

306
J. Cho et al. / Inorganica Chimica Acta 342 (2003) 305Á310
/
luted with BaSO4 were recorded with a Shimadzu 2401
PC UVÁVis recording spectrophotometer. Elemental
analyses were performed by the Korea Research In-
stitute of Chemical Technology, Taejon, Korea. The
precursor complex [Cu(L)Cl2] was prepared by a
template method according to the literature procedures
previously reported [15].
used to collect sufficient data. The data frames were
integrated and scaled using the DENZO-SMN package
[16]. The structures were solved and refined, using the
/
SHELXTL\PC V5.1 package [17]. Refinement was by full-
matrix least-squares on F2, using all data (negative
intensities included). Hydrogen atoms were included in
calculated positions, except for those involving hydro-
gen bonding specifically for the hydrogen atoms of the
carboxyl groups, hydroxyl groups and those bonded to
the nitrogen atoms, which were refined with isotropic
2.2. Synthesis of 1
thermal parameters. In 2 the hydrogen atom on the ꢀ
OH group of ꢀCH2ꢀCH2ꢀOH is disordered over two
OH
/
To an aqueous solution (10 ml) of [Cu(L)Cl2] (217 mg,
0.5 mmol) was added a methanol solution (10 ml) of btc
(254 mg, 1.0 mmol) in an open beaker. Reddish purple
crystals 1 were obtained in a day. Suitable crystals of 1
for X-ray diffraction studies and subsequent spectro-
scopic measurements were manually collected under the
microscope. Anal. Calc. for C32H40N6O18Cu (1): C,
44.64; H, 4.65; N, 9.76. Found: C, 45.01; H, 4.88; N,
9.97%.
/
/
/
sites to facilitate hydrogen bonding to two other ꢀ
/
groups on symmetry related molecules.
3. Results and discussion
3.1. Description of structures for 1 and 2
2.3. Synthesis of 2
The molecular structure of 1 shows a monomeric
copper(II) complex [Cu(L)(btcꢂ)2] as illustrated in Fig.
1. The coordination environment around the central
copper(II) ion shows an axially elongated octahedron
To an aqueous solution (20 ml) of [Cu(L)Cl2] (217 mg,
0.5 mmol) was added a methanol solution (20 ml) of btc
(127 mg, 0.5 mmol) and two drops of pyridine in an
open beaker. Purple crystals 2 were obtained in 2 weeks.
Double deprotonation of btc occurred regardless of the
ratio of acid to base. However, the longer crystallization
times and more dilute reaction conditions are requisite
for the isolation of the compound 2. Suitable crystals of
2 for X-ray diffraction studies and subsequent spectro-
scopic measurements were manually collected under the
microscope. Anal. Calc. for C22H34N6O10Cu (2): C,
43.56; H, 5.61; N, 13.86. Found: C, 44.04; H, 5.90; N,
14.11%.
with four Cuꢀ
contacts. The Cu atom is located on an inversion center.
The four CuꢀN distances are in the range 2.0026(12)Á
/
N bonds and two Cuꢀ/O (carbonyl)
/
/
˚
2.0189(13) A and shorter than the Cuꢀ
/
O distance
˚
of 2.4814(11) A. These values fall within the range
of comparable reports for such
([Cu(L1)(CH3CN)2]×2PF6; Cuꢀ
2.0481(18) A, [Cu(L1)(terephthalato)]n ×
a
Nꢀ
2nH2O; Cuꢀ
3,14-dimethyl-
geometry
2.0188(18),
/
/
/
˚
/
/
˚
Nꢀ
/
2.0225(16), 2.0294(16) A) (L1ꢀ
/
2,6,13,17-tetraazatricyclo[14.4.01.18.07.12]docosane)
[18,19]. Selected interatomic distances and angles for 1
are listed in Table 2. As is usual, the macrocyclic ligand
skeleton in 1 adopts the trans III (R,R,S,S) conforma-
tion. Two structurally interesting features are found in
complex 1. Only one of the four COOH groups in the
btc is deprotonated under the reaction conditions
described in the Section 2, resulting in the formation
of a rare btcꢂ anion. The most common are the btc4ꢂ
and the btc2ꢂ anions [11,20]. The deprotonated COOꢂ
2.4. X-ray crystallography
A summary of selected crystallographic data for 1 and
2 is given in Table 1. X-ray data were collected on a
Nonius KappaCCD diffractometer, using graphite
˚
0.71073 A). A
monochromated Mo Ka radiation (lꢀ
/
combination of 18 f and V (with k offsets) scans were

J. Cho et al. / Inorganica Chimica Acta 342 (2003) 305Á
/310
307
Table 2
Selected interatomic distances (A) and angles (8) for [Cu(L)(btcꢂ)2] (1)
Table 1
Crystal data and structure refinement for [Cu(L)(btcꢂ)2] (1) and
[Cu(L)(btc2ꢂ)]n (2)
˚
Cu1ꢀN1
Cu1ꢀO2
O3ꢀC13
O5ꢀC14
O7ꢀC15
O9ꢀC16
2.0026(12)
2.4814(11)
1.320(2)
Cu1ꢀN2
O2ꢀC13
O4ꢀC14
O6ꢀC15
O8ꢀC16
2.0189(13)
1.214(2)
1
2
1.2186(19)
1.220(2)
1.2704(19)
1.3102(19)
1.2858(19)
1.2369(19)
Empirical formula
Formula weight
Temperature (K)
C
32H40CuN6O18
C22H34CuN6O10
606.09
150(1)
860.24
150(1)
˚
Wavelength (A)
0.71073
triclinic
0.71073
monoclinic
C2/c
N1ꢀCu1ꢀN1#1
N1ꢀCu1ꢀN2#1
N1#1ꢀCu1ꢀO2
N2#1ꢀCu1ꢀO2
180
N1ꢀCu1ꢀN2
N1ꢀCu1ꢀO2
N2ꢀCu1ꢀO2
92.95(5)
87.63(5)
92.55(5)
Crystal system
Space group
87.05(5)
92.37(5)
87.45(5)
¯
P
/1/
˚
a (A)
7.82390(10)
9.07370(10)
13.4700(2)
72.9900(10)
89.5400(10)
69.8600(10)
853.924(19)
1
20.5580(6)
14.6080(4)
8.9330(3)
90
˚
b (A)
˚
c (A)
Symmetry transformations used to generate equivalent atoms: #1
ꢂxꢃ1, ꢂyꢃ1, ꢂzꢃ1.
a (o)
b
g
113.3630(11)
90
˚
O2 distance of 2.4814(11) A found in 1. Our
the Cu1ꢀ
/
3
˚
V (A )
2462.73(13)
4
1.635
recent studies on the macrocyclic nickel(II) and cop-
per(II) complexes with the btc moieties always indicate
that the COOꢂ groups favorably interact with metal
ions than the COOH group [14]. The following effects
may be responsible for this unusual carbonyl coordina-
Z
Dcalc (Mg mꢂ3
Absorption coefficient
(mmꢂ1
F(000)
)
1.673
0.735
0.958
)
447
0.36ꢄ0.28ꢄ0.20
1268
0.22ꢄ0.18ꢄ0.14
Crystal size (mm)
u Range for data
collection (8)
tion to the copper(II) ion: (i) the pre-organized Nꢀ
/H
2.79Á/27.47
2.67Á27.56
/
directionality of the macrocyclic ligand with its role in
profacial selection of the btcꢂ anion binding is achieved
through hydrogen bonding interactions; (ii) the complex
1 contains an intramolecular hydrogen bond [22]
Index ranges
ꢂ105h 510,
ꢂ115k 511,
ꢂ165l 517
12 436
ꢂ265h 526,
ꢂ185k 518,
ꢂ115l 511
10 084
Reflections collected
Independent
reflections
between C15ꢀ
/
O6ꢀ
/
O7 and C16ꢀ
/
O8ꢀ
/
O9ꢀ/H8O which
3901 [Rintꢀ0.0400] 2834 [Rintꢀ0.0380]
inhibits the carboxylate group for binding to the
copper(II) ion, instead resulting in the carbonyl coordi-
nation. The complex 1 extends its structure through
multiple intermolecular hydrogen bonding interactions
(Table 4). The btcꢂ ligand in 1 is not planar since the
Completeness to u
Absolute correction
99.6% (uꢀ27.478) 99.3%(uꢀ27.568)
multi-scan from
equivalent reflec-
tions
semi-empirical from
equivalents
Max and min
transmission
Refinement method
0.8669 and 0.7778 0.8776 and 0.8169
dihedral angle (O2ꢀ
/
C13ꢀ
/
C7ꢀ
/
C12) between the COOH
full-matrix least-
squares on F2
3901/0/284
full-matrix least-
squares on F2
2834/1/191
group which is coordinated to copper(II) and the
aromatic ring (C13ꢀ
/
O2ꢀ
/
O3ꢀH30) is 81.18. The other
/
Data/restraints/
parameters
two COOH and COOꢂ groups which are not coordi-
nated to the central copper(II) ion lie almost in the
phenyl ring plane (dihedral angles between carboxyl
groups and aromatic ring is less than 58).
Goodness-of-fit on
F2
1.041
1.043
Final R indices
[I ꢀ2s(I)]
R indices (all data)
R1ꢀ0.0310,
wR2ꢀ0.0777
R1ꢀ0.0348,
wR2ꢀ0.0799
R1ꢀ0.0321,
wR2ꢀ0.0782
R1ꢀ0.0406,
wR2ꢀ0.0827
As illustrated in Fig. 2, the structure of 2 consists of a
1D coordination polymer with a basic [Cu(L)(m-btc2ꢂ)]
unit. The coordination environment around the central
copper(II) ion shows a distorted octahedron in the chain
Largest difference peak 0.354 and ꢂ0.586 0.290 and ꢂ0.526
ꢂ3
˚
and hole (e A
)
R1ꢀajjFoꢂFcjj/ajFoj and wR2ꢀ[a[w(Fo2ꢂFc2)2]/a[w(Fo2)2]]1/2
.
direction with four Cuꢀ
contacts. The Cu atom sits on an inversion center. The
N distances are in the range 1.9999(14)Á
/
N bonds and two Cuꢀ
/
O
four Cuꢀ
/
/
˚
2.0006(14) A and the Cuꢀ
/
O distances are 2.6445(13)
˚
˚
O distance of 2.6445(13) A is comparable to
that found in the related tetraaza system
group participates in hydrogen-bonding interaction to
the neighboring COOH group by an intramolecular
fashion to form a seven-membered ring. The other
COOH groups remain in free acid form and one of
these is coordinated to the copper(II) ion through
carbonyl. Carbonyl coordination to the copper(II) ion
is unusual. The reported copper(II)-carbonyl oxygen
atom distances by Colacio et al. are 2.444(8) and
A. The Cuꢀ
/
([Cu(L1)(terephthalato)]n ×2nH2O; CuꢀOꢀ2.7323(12)
/
/
/
˚
A). Selected interatomic distances and angles for 2 are
listed in Table 3. Several combined effects are believed
to work for this long Cuꢀ
/
O contact: (i) the well-known
JahnÁTeller effect is observed in this system, which
/
indicates that the structure of copper(II) complex must
be distorted due to the octahedral d9 configuration
˚
2.453(8) A, respectively, [21]. Those are comparable to

308
J. Cho et al. / Inorganica Chimica Acta 342 (2003) 305Á310
/
Fig. 1. Molecular structure of [Cu(L)(btcꢂ)2] (1) with atom-labeling scheme. Hydrogen atoms other than those participating in hydrogen bonding
are omitted for clarity.
which is orbitally degenerate, and therefore, susceptible
Table 4
Hydrogen bonds for [Cu(L)(btcꢂ)2] (1) (A and 8)
to distortion; (ii) the intramolecular hydrogen bond
(Table 5) between C11ꢀO5ꢀO4ꢀH4O and C10ꢀO3ꢀO2
as found in 1 results in the weak CuꢀO interaction [22];
˚
/
/
/
/
/
DꢀHꢀ ꢀ ꢀA
d(DꢀH) d(Hꢀ ꢀ ꢀA) d(Dꢀ ꢀ ꢀA)
ꢁ(DHA)
/
(iii) the sterically hindered carboxyl groups in the btc2ꢂ
anion prevent the anion from approaching closely to the
copper(II) macrocycle. In the btc2ꢂ anion in 2, two
carboxylate groups and two carboxylic acid groups
nearly lie in the phenyl ring plane with the afore-
mentioned intramolecular hydrogen bonds. The tor-
sional angles of those groups with the phenyl ring range
from 1.7 to 6.08. The different shapes of the btc2ꢂ
anions and other btc moieties have been reported, and
their shapes vary with different structures, depending on
N2ꢀH2Nꢀ ꢀ ꢀO4
0.89(2)
0.84(2)
0.81(3)
0.82(3)
0.80(3)
1.18(3)
2.38(2)
2.16(2)
1.80(3)
1.77(3)
1.89(3)
1.21(3)
3.2567(17) 168.6(17)
2.9464(17) 155.1(18)
2.6008(16) 170(3)
2.5877(18) 177(3)
2.6794(17) 171(3)
2.3800(17) 174(3)
N1ꢀH1Nꢀ ꢀ ꢀO7#2
O5ꢀH5Oꢀ ꢀ ꢀO9#3
O3ꢀH3Oꢀ ꢀ ꢀO1#4
O1ꢀH1Oꢀ ꢀ ꢀO6#5
O8ꢀH8Oꢀ ꢀ ꢀO7
Symmetry transformations used to generate equivalent atoms: #2
ꢂxꢃ1, ꢂyꢃ1, ꢂz; #3 xꢂ1, yꢃ1, z; #4 x, yꢂ1, z; #5 ꢂx, ꢂyꢃ2,
ꢂz.
the degree of deprotonation of the btc and the types of
the hydrogen bonding systems involved [7Á9,11,12].
/
As is common with supramolecular polymers and
coordination polymers, the complexes 1 and 2 are
Table 3
Selected interatomic distances (A) and angles (8) for [Cu(L)(btc2ꢂ)]n
(2)
˚
Table 5
Hydrogen bonds for [Cu(L)(btc2ꢂ)]n (2) (A and 8)
Cu1ꢀN1
Cu1ꢀO2
O3ꢀC10
O5ꢀC11
2.0006(14)
2.6445(13)
1.227(2)
Cu1ꢀN2
O2ꢀC10
O4ꢀC11
1.9999(14)
1.284(2)
1.295(2)
˚
DꢀHꢀ ꢀ ꢀA
d(DꢀH) d(Hꢀ ꢀ ꢀA) d(Dꢀ ꢀ ꢀA)
ꢁ(DHA)
1.220(2)
O1ꢀH1OAꢀ ꢀ ꢀO1#3 0.78(3)
1.95(3)
1.93(3)
1.96
2.693(3)
2.711(3)
2.845(2)
159(5)
178(4)
158.1
N1#1ꢀCu1ꢀN1
N2ꢀCu1ꢀN1#1
N2ꢀCu1ꢀO2
180
N2ꢀCu1ꢀN1
N2#1ꢀCu1ꢀO2
N1#1ꢀCu1ꢀO2
93.94(6)
91.19(5)
96.28(6)
O1ꢀH1OBꢀ ꢀ ꢀO1#4
N2ꢀH2Nꢀ ꢀ ꢀO3
O4ꢀH4Oꢀ ꢀ ꢀO2
0.78(3)
0.93
0.95(4)
86.06(6)
88.81(5)
83.73(6)
1.47(4)
2.4065(19) 169(4)
N1ꢀCu1ꢀO2
Symmetry transformations used to generate equivalent atoms: #3
ꢂxꢃ1, y, ꢂzꢃ3/2; #4 ꢂxꢃ1, ꢂy, ꢂzꢃ1.
Symmetry transformations used to generate equivalent atoms: #1
ꢂxꢃ1/2, ꢂyꢃ1/2, ꢂz.

J. Cho et al. / Inorganica Chimica Acta 342 (2003) 305Á
/310
309
Fig. 2. One-dimensional polymeric chain structure of [Cu(L)(btc2ꢂ)]n (2) with atom-labeling scheme. Hydrogen atoms other than those participating
in hydrogen bonding are omitted for clarity.
insoluble in common solvents such as methanol, water,
acetonitrile, and DMF.
4. Supplementary material
Crystallographic data have been deposited at the
Cambridge Crystallographic Data Center (CCDC),
CCDC Nos. 185966 for 1 and 185967 for 2. Copies of
this information may be obtained free of charge from
The Director, CCDC, 12 Union Road, Cambridge, CB2
3.2. Spectroscopic properties for 1 and 2
The IR spectrum of 1 shows the stretching frequencies
of the three different carboxyl groups at 1715, 1694,
1604 cmꢂ1 for the nas(COO) and 1455, 1380, 1272 cmꢂ1
for the ns(COO). Similarly, the absorption bands for the
carboxyl groups under two different environments at
1556, 1481 cmꢂ1 for the nas(COO) and 1362, 1328 cmꢂ1
for the ns(COO) are observed in 2 [23]. In addition,
sharp bands n(OH) at 3318 and 3243 cmꢂ1 in 1 (3367
and 3236 cmꢂ1 in 2) and a weak band n(NH) at 3192
cmꢂ1 (3195 cmꢂ1 in 2) indicate that the complexes 1
and 2 contain a macrocyclic ligand, carboxylic acid and
hydroxyl groups.
1EZ, UK (fax: ꢃ44-1223-336-033; e-mail: deposit@
/
ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk).
Acknowledgements
This work was supported by the Pukyong National
University Fund in 2001.
References
The solid state electronic spectrum of 1 is composed
of three bands at 210, 298, and 520 nm (210, 300, and
510 nm in 2). The broad band maxima (520 nm in 1 and
[1] M. Eddaoudi, D.B. Moler, H. Li, B. Chen, T.M. Reineke, M.
O’Keeffe, O.M. Yaghi, Acc. Chem. Res. 34 (2001) 319.
[2] H.J. Choi, T.S. Lee, M.P. Suh, Angew. Chem. Int. Ed. 38 (1999)
1405.
510 in 2) in the visible region can be attributed to a
2
2B2g,
[3] O.M. Yaghi, H. Li, C. Davis, D. Richardson, T.L. Groy, Acc.
Chem. Res. 31 (1998) 474.
composite of two possible transitions B1g0
/
2B1g02Eg out of three spin allowed transitions of
tetragonally elongated copper(II) ion under approxi-
/
[4] H.J. Choi, M.P. Suh, Inorg. Chem. 38 (1999) 6309.
[5] K.-Y. Choi, K.M. Chun, I.-H. Suh, Polyhedron 20 (2001) 57.
[6] M. Eddaoudi, J. Kim, J.B. Wachter, H.K. Chae, M. O’Keeffe,
O.M. Yaghi, J. Am. Chem. Soc. 123 (2001) 4368.
[7] F.D. Rochon, G. Massarweh, Inorg. Chim. Acta 304 (2000) 190.
[8] F.D. Rochon, G. Massarweh, Inorg. Chim. Acta 314 (2001) 163.
[9] Q. Shi, R. Cao, D.-F. Sun, M.-C. Hong, Y.-C. Liang, Polyhedron
20 (2001) 3287.
mate D4h symmetry [24,25]. The blue shift of this band
along with the longer Cuꢀ
/
O distance compared with
those found in 1 supports that the stronger JahnÁ
/Teller
effect is present in 2. The remaining two bands at higher
energy region may be from the charge-transfer in origin.

310
J. Cho et al. / Inorganica Chimica Acta 342 (2003) 305Á310
/
[10] L.P. Wu, M. Munakata, T. Kuroda-Sowa, M. Maekawa, Y.
Suenaga, Inorg. Chim. Acta 249 (1996) 183.
[18] J.C. Kim, J.C. Fettinger, Y.I. Kim, Inorg. Chim. Acta 286 (1999)
67.
[19] J.C. Kim, J. Cho, A.J. Lough, Inorg. Chim. Acta 317 (2001) 252.
[20] J.-Z. Zou, Q. Liu, Z. Xu, X.-Z. You, X.-Y. Huang, Polyhedron 17
(1998) 1863.
[11] K. Biradha, M.J. Zaworotko, Cryst. Eng. 1 (1998) 67.
[12] B. Moulton, M.J. Zaworotko, Chem. Rev. 101 (2001) 1629.
[13] D.-Q. Chu, J.-Q. Xu, L.-M. Duan, T.-G. Wang, A.-Q. Tang, L.
Ye, Eur. J. Inorg. Chem. (2001) 1135.
[21] J.-M. Dom´ınguez-Vera, A. Rodr´ıguez, R. Cuesta, R. Kivekas, E.
¨
Colacio, J. Chem. Soc., Dalton Trans. (2002) 561.
[22] P. Gilli, V. Bertolasi, V. Ferretti, G. Gilli, J. Am. Chem. Soc. 116
(1994) 909.
[14] J.C. Kim, A.J. Lough, H. Jo, Inorg. Chem. Commun 5 (2002)
616.
[15] R.W. Hay, J.M. Armstrong, M.M. Hassan, Trans. Met. Chem. 17
(1992) 270.
[23] R. Diniz, H.A. de Abreu, W.B. de Almeida, M.T.C. Sansiviero,
N.G. Fernandes, Eur. J. Inorg. Chem. (2002) 1115.
[24] A.A. El-Bindary, A.Z. El-Sonbati, Polish J. Chem. 74 (2000) 615.
[25] B.N. Figgis, M.A. Hitchman, Ligand Field Theory and its
Application, Wiley-VCH, New York, 2000, p. 210.
[16] Z. Otwinowski, W. Minor, Methods Enzymol. 276 (1997) 1783.
[17] G.M. Sheldrick, SHELXL\PC V5.1, Bruker Analytical X-ray
Systems, Madison, WI, 1997.