A tetranuclear copper(II) cluster: Bis-(μ-4-chlorobenzoato- κ2O:O′)(4-chlorobenzoato-κ2 O,O′)(4-chlorobenzoato-κO)tetrakis(μ3-2- pyridylmethanolato-4 N,O:O:O)tetracopper(II)

Article abstract of DOI:10.1107/S010827011103335X

The title compound, [Cu₄(C₇H₄ClO ₂)₄(C₆H₆NO)₄], consists of isolated tetra-nuclear clusters, where the Cu²⁺ cations are five- and sixfold coordinated by O atoms from the 4-chloro-benzoate anions and by pyridine N and methanol-ate O atoms from bidentate 2-pyridylmethanolate ligands. While three Cu atoms are six-coordinated by an NO₅ donor set forming distorted octahedra, the fourth Cu atom is five-coordinated by an NO ₄ donor set forming a distorted tetragonal-pyramidal coordination around the Cu atom. The nucleus is a deformed cubane-like Cu₄O ₄ structure, with Cu...Cu distances in the range 3.0266 (11)-3.5144 (13) A.

Full text of DOI:10.1107/S010827011103335X

metal-organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
methanolato)tetracopper(II), (I). The full tetranuclear mol-
ecule defining the asymmetric unit is shown in Fig. 1. The four
Cu2+ cations and four ꢀ3-bridging methanolate O atoms of the
2-pyridylmethanolate ligands form a deformed cubane-like
Cu4O4 core (Fig. 2). The distances between pairs of Cu2+
ISSN 0108-2701
˚
cations are in the range 3.0266 (11)–3.5144 (13) A. Each pair
A tetranuclear copper(II) cluster:
bis(l-4-chlorobenzoato-j2O:O0)-
(4-chlorobenzoato-j2O,O0)(4-chloro-
benzoato-jO)tetrakis(l3-2-pyridyl-
methanolato-j4N,O:O:O)tetra-
copper(II)
of Cu atoms (Cu1ꢀ ꢀ ꢀCu2 and Cu2ꢀ ꢀ ꢀCu3) is also bridged by
one carboxylate group of a 4-chlorobenzoate ligand (Fig. 2).
Each Cu2+ ion is coordinated in a different coordination
environment.
Jan Moncol,a* Klaudia Jomova,b Lubomir Zelenicky,b
Tadeusz Lisc and Marian Valkoa
aFaculty of Chemical and Food Technology, Slovak Technical University, SK-812 37
Bratislava, Slovakia, bFaculty of Natural Sciences, Constantine the Philosopher
University in Nitra, SK-949 74 Nitra, Slovakia, and cFaculty of Chemistry, University
of Wrocław, PL-503 83 Wrocław, Poland
Correspondence e-mail: jan.moncol@stuba.sk
Received 27 July 2011
Accepted 16 August 2011
Online 31 August 2011
The title compound, [Cu4(C7H4ClO2)4(C6H6NO)4], consists of
isolated tetranuclear clusters, where the Cu2+ cations are five-
and sixfold coordinated by O atoms from the 4-chloro-
benzoate anions and by pyridine N and methanolate O atoms
from bidentate 2-pyridylmethanolate ligands. While three Cu
atoms are six-coordinated by an NO5 donor set forming
distorted octahedra, the fourth Cu atom is five-coordinated by
an NO4 donor set forming a distorted tetragonal–pyramidal
coordination around the Cu atom. The nucleus is a deformed
cubane-like Cu4O4 structure, with Cuꢀ ꢀ ꢀCu distances in the
The Cu1 cation is six-coordinated by O and N atoms from
chelating ligands and lies in the centre of a [4+1+1] coordi-
˚
range 3.0266 (11)–3.5144 (13) A.
Comment
Much attention has been devoted in the past 20 years to the
preparation and characterization of multinuclear metal
complexes (Oshio & Ichida, 1995). These metal complexes
have been prepared with the aim of providing new functional
materials such as single-molecule magnets or catalysts (Sessoli
et al., 1993). In these complexes, the bridging ligands may
provide superexchange pathways between the metal centres.
Several tetrameric transition metal complexes with ꢀ3-brid-
ging 2-pyridylmethanolate anions have been crystallo-
graphically studied. These complexes form cubane-like core
structures (Clemente-Juan et al., 2000, 2002; Efthymiou et al.,
2009; Escuer et al., 1999; Lecren et al., 2008; Wang et al., 2010;
Yang et al., 2003, 2005, 2006; Zhang et al., 2010).
Figure 1
A perspective view of (I), showing the atom-numbering scheme.
Displacement ellipsoids are drawn at the 30% probability level. H atoms
have been omitted for clarity. The Cu4—O4 and Cu1—O11 semicoordi-
nated bonds are drawn as dashed lines.
In this paper, we present an interesting structure, a tetra-
meric copper(II) complex, namely bis(ꢀ-4-chlorobenzoato)(4-
chlorobenzoato)(4-chlorobenzoato)tetrakis(ꢀ3-2-pyridyl-
m318 # 2011 International Union of Crystallography
doi:10.1107/S010827011103335X
Acta Cryst. (2011). C67, m318–m320

metal-organic compounds
and one methanolate O atom from a chelating 2-pyridyl-
˚
methanolate anion [Cu4—N1 = 1.984 (2) A and Cu4—O9 =
˚
1.954 (2) A], one carboxylate O atom from a chelating
˚
4-chlorobenzoate anion [Cu4—O3 = 1.937 (2) A] and one
methanolate O atom from a neighbouring bridging 2-pyridyl-
˚
methanolate anion [Cu4—O11 = 1.942 (2) A] in the equatorial
plane. The next two positions of the coordination polyhedron
are occupied by one methanolate O atom from a neighbouring
˚
bridging 2-pyridylmethanolate anion [Cu4—O10 = 2.396 (2) A]
and one carboxylate O atom from a chelating 4-chlorobenzoate
˚
anion [Cu4—O4 = 2.811 (2) A].
Figure 2
The structure of the cubane-like core of tetrameric complex (I)
The packing in (I) is rather complex; the crystal structure
does not contain medium–strong hydrogen bonds but the
molecules are linked through weak C—Hꢀ ꢀ ꢀO and C—Hꢀ ꢀ ꢀCl
hydrogen-bonding interactions (Gilli & Gilli, 2009). There
are three weak intramolecular C—Hꢀ ꢀ ꢀO hydrogen bonds
(entries 1–3 in Table 1). There complex molecules are in
turn connected through weak intermolecular C—Hꢀ ꢀ ꢀO
hydrogen bonds (entries 4–7 in Table 1) and weak C—Hꢀ ꢀ ꢀCl
hydrogen bonds (entries 8–9 in Table 1). These weak contacts
are further reinforced by a C—Hꢀ ꢀ ꢀꢄ interaction (Suezawa et
al. 2002), viz. C28—H28ꢀ ꢀ ꢀCg1vi [Cg1 is the centroid of the
C2–C7 ring; symmetry code: (vi) ꢁx + 12, ꢁy + 21, ꢁz + 21], with
nation polyhedron. The axial Cu1—O11 semicoordination
˚
bond distance is 2.873 (2) A. The tetragonal plane is formed
by one pyridine N and one methanolate O atom from a
˚
chelating 2-pyridylmethanolate anion [Cu1—N4 = 1.988 (2) A
˚
and Cu1—O12 = 1.974 (2) A], one carboxylate O atom from a
˚
monodentate 4-chlorobenzoate anion [Cu1—O5 = 1.919 (2) A]
and one methanolate O atom from a neighbouring bridging
˚
2-pyridylmethanolate anion [Cu1—O9 = 1.945 (2) A]. The axial
positions of the coordination polyhedron are occupied by one
carboxylate O atom from a bridging 4-chlorobenzoate anion
˚
[Cu1—O7 = 2.385 (2) A] and one methanolate O atom from a
second neighbouring bridging 2-pyridylmethanolate anion
˚
[Cu1—O11 = 2.873 (2) A].
vi
˚
H28ꢀ ꢀ ꢀCg1 = 2.62 A and a shortest distance of H28ꢀ ꢀ ꢀC4 =
˚
2.79 A.
The Cu2 atom has a tetragonal–bipyramidal [4+2] coordi-
nation environment. The tetragonal plane is built up by one
pyridine N and one methanolate O atom from a chelating
This communication reports the second known example of a
tetragonal cubane-like copper(II) complex with ꢀ3-bridging
2-pyridylmethanolate anions, the first being that reported by
Ang et al. (2004). However, while in this latter complex all four
Cu2+ cations show the same type of coordination polyhedra,
the title compound, as already described, does not. Examples
of both types can be found among the reports in the literature
dealing with cubane-like tetramers of different transition
metals (nickel, iron and zinc) and ꢀ3-bridging 2-pyridyl-
methanolate anions. Thus, in the two cubane-like tetrameric
nickel(II) complexes reported by Zhang et al. (2010) and
Efthymiou et al. (2009), all the NiII cations have a similar
coordination, with the metal centres being connected via four
ꢀ3-bridging 2-pyridylmethanolate anions. Different coordi-
nation geometries, on the other hand, can be found in the
nickel(II) complex reported by Clemente-Juan et al. (2000)
and the two iron(II) complexes reported by Clemente-Juan et
al. (2002), where only one ꢀ3-bridging 2-pyridylmethanolate
anion connects three of the four metal centres; the remaining
bridges linking the metal ions are provided by different
ligands.
˚
2-pyridylmethanolate anion [Cu2—N2 = 1.998 (2) A and
˚
Cu2—O10 = 1.957 (2) A], one carboxylate O atom from a
˚
bridging 4-chlorobenzoate anion [Cu2—O8 = 1.932 (2) A] and
one methanolate O atom from a neighbouring bridging
˚
2-pyridylmethanolate anion [Cu2—O12 = 1.965 (2) A]. The
axial positions of the tetragonal bipyramid are occupied by
one carboxylate O atom from a second bridging 4-chloro-
˚
benzoate anion [Cu2—O7 = 2.607 (2) A] and one methanolate
O atom from a second neighbouring bridging 2-pyridyl-
˚
methanolate anion [Cu2—O9 = 2.545 (2) A].
The Cu3 cation is coordinated in a tetragonal–pyramidal
[4+1] geometry. The tetragonal plane is formed by one pyri-
dine N and one methanolate O atom from a chelating
˚
2-pyridylmethanolate anion [Cu3—N3 = 2.008 (2) A and
˚
Cu3—O11 = 1.913 (2) A], one carboxylate O atom from a
˚
bridging 4-chlorobenzoate anion [Cu3—O1 = 1.918 (2) A] and
one methanolate O atom from a neighbouring bridging
˚
2-pyridylmethanolate anion [Cu3—O10 = 1.955 (2) A]. The
axial position is occupied by one methanolate O atom from a
second neighbouring bridging 2-pyridylmethanolate anion
˚
[Cu3—O12 = 2.303 (2) A]. For this type of five-coordinate
structure, the parameter ꢁ [ꢁ = (ꢂ ꢁ ꢃ)/60, where ꢂ and ꢃ are
the equatorial angles] was introduced by Addison et al. (1984).
The value of ꢁ ranges from 0 for perfectly tetragonal–pyra-
midal geometry to 1 for perfectly trigonal–bipyramidal
geometry. In this case, ꢁ = 0.14, which favours the description
as a tetragonal–pyramidal geometry.
All the cases discussed so far correspond to cubane-like
complexes without internal crystallographic symmetry, but
there are, in addition, reported examples of tetranuclear
cubane-like metal complexes presenting a higher degree of
symmetry in tetragonal space groups where only one-quarter
of the molecule is independent, such as those presented by
Wang et al. (2010), Yang et al. (2003, 2005, 2006) and Escuer et
al. (1999).
Since the bridging ligands in cubane-like complexes may
provide superexchange pathways between the metal centres,
magnetic susceptibility measurements in (I) are underway.
The coordination polyhedron around Cu4 has [4+1+1]
geometry. The Cu4 cation is coordinated by one pyridine N
ꢂ
Acta Cryst. (2011). C67, m318–m320
Moncol et al.
[Cu4(C7H4ClO2)4(C6H6NO)4] m319

metal-organic compounds
Data collection: CrysAlis CCD (Agilent, 2011); cell refinement:
CrysAlis RED (Agilent, 2011); data reduction: CrysAlis RED;
program(s) used to solve structure: SHELXS97 (Sheldrick, 2008);
program(s) used to refine structure: SHELXL97 (Sheldrick, 2008);
molecular graphics: XP in SHELXTL (Sheldrick, 2008); software
used to prepare material for publication: publCIF (Westrip, 2010).
Experimental
For the preparation of the title compound, Cu(4-ClC6H4CO2)2ꢀ2H2O
(0.001 mol, 0.411 g) was dissolved in methanol (50 ml) and treated
with 2-pyridylmethanol (0.001 mol, 0.10 ml) in a 1:1 molar ratio. The
mixture was stirred and left to stand at room temperature, giving
crystals of (I) suitable for X-ray analysis (yield 85%). Analysis found:
C 52.45, H 3.71, N 4.68, Cu 10.78%; calculated: C 52.67, H 3.74, N 4.73,
Cu 10.72%.
This work was supported by the Scientific Grant Agency of
the Ministry of Education of the Slovak Republic (VEGA
Project Nos. 1/0856/11 and 1/0562/10) and by the Research and
Development Agency of the Slovak Republic (contract No.
APVV-0202-10).
Crystal data
3
˚
[Cu4(C7H4ClO2)4(C6H6NO)4]
Mr = 1308.84
V = 10541 (6) A
Z = 8
Monoclinic, I2=a
Mo Kꢂ radiation
ꢀ = 1.86 mmꢁ1
T = 100 K
0.45 ꢄ 0.35 ꢄ 0.25 mm
˚
a = 20.326 (6) A
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: BG3141). Services for accessing these data are
described at the back of the journal.
˚
b = 14.184 (4) A
˚
c = 36.696 (13) A
ꢃ = 94.89 (3)ꢃ
Data collection
Kuma KM-4 CCD area-detector
diffractometer
Absorption correction: analytical
CrysAlis RED (Agilent, 2011)
Tmin = 0.467, Tmax = 0.659
36942 measured reflections
12348 independent reflections
8586 reflections with I > 2ꢅ(I)
Rint = 0.042
References
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Refinement
R[F2 > 2ꢅ(F2)] = 0.034
wR(F2) = 0.069
S = 1.02
685 parameters
H-atom parameteꢁrs3 constrained
˚
Áꢆmax = 0.56 e A
ꢁ3
˚
12348 reflections
Áꢆmin = ꢁ0.37 e A
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Table 1
Hydrogen-bond geometry (A, ).
ꢃ
˚
D—Hꢀ ꢀ ꢀA
D—H
Hꢀ ꢀ ꢀA
Dꢀ ꢀ ꢀA
D—Hꢀ ꢀ ꢀA
Lecren, L., Roubeau, O., Li, Y.-G., Le Goff, X. F., Miyasaka, H., Richard, F.,
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1857–1863.
C34—H34Aꢀ ꢀ ꢀO5
C39—H39ꢀ ꢀ ꢀO8
C46—H46Aꢀ ꢀ ꢀO6
C33—H33ꢀ ꢀ ꢀO4i
C36—H36ꢀ ꢀ ꢀO6ii
C37—H37ꢀ ꢀ ꢀO4ii
C48—H48ꢀ ꢀ ꢀO8iii
C30—H30ꢀ ꢀ ꢀCl3iv
C34—H34Aꢀ ꢀ ꢀCl2v
0.99
0.95
0.99
0.95
0.95
0.95
0.95
0.95
0.99
2.59
2.55
2.52
2.46
2.41
2.46
2.53
2.78
2.75
3.116 (3)
3.034 (3)
3.462 (3)
3.010 (3)
3.221 (3)
3.279 (3)
3.401 (3)
3.501 (3)
3.337 (3)
114
112
158
117
143
145
152
134
118
1
2
1
2
1
2
1
2
1
2
Symmetry codes: (i) ꢁx þ ; y; ꢁz; (ii) x ꢁ ; ꢁy; z; (iii) ꢁx þ ; ꢁy þ ; ꢁz þ ; (iv)
1
2
x ꢁ ; ꢁy þ 1; z; (v) x; y þ 1; z.
Yang, E.-C., Kirman, C., Lawrence, J., Zakharov, L. N., Rheingold, A. L., Hill,
S. & Hendrickson, D. N. (2005). Inorg. Chem. 44, 3827–3836.
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Isidro, R. M., Lu, G.-D., Wilson, S. A., Rheingold, A. L., Ishimoto, H. &
Hendrickson, D. N. (2006). Inorg. Chem. 45, 529–546.
The structure was refined in the nonconventional monoclinic space
group I2/a, a variant of C2/c. H atoms were positioned in ideal
˚
positions, with C—H = 0.95 A for aromatic H atoms and C—H =
˚
0.99 A for methylene H atoms, and constrained to ride on their
parent atoms, with Uiso(H) = 1.2Ueq(C).
Zhang, J., Teo, P., Pattacini, R., Kermagoret, A., Welter, R., Rogez, G., Hor,
T. S. A. & Braunstein, P. (2010). Angew. Chem. Int. Ed. 49, 4443–4446.
ꢂ
m320 Moncol et al. [Cu4(C7H4ClO2)4(C6H6NO)4]
Acta Cryst. (2011). C67, m318–m320