[2-(2-Pyridyl)-1H-benzimidazolej κ2N2,N 3]bis(p-toluato-κ2O,O′)- manganese(II)

Article abstract of DOI:10.1107/S0108270107055023

In the title compound, [Mn(C8H7O2)2(C12H9N3)], the manganese(II) centre is surrounded by three bidentate chelating ligands, namely, one 2-(2-pyrid-yl)benzimidazole ligand [Mn - N = 2.1954 (13) and 2.2595 (14) A] and two p-toluate ligands [Mn - O = 2.1559 (13)-2.2748 (14) A]. It displays a severely distorted octa-hedral geometry, with cis angles ranging from 58.87 (4) to 106.49 (5)°. Inter-molecular C - H...O hydrogen bonds between the p-toluate ligands link the mol-ecules into infinite chains, and every two neighbouring chains are further coupled by N - H...O and C - H...O hydrogen bonds between the 2-(2-pyrid-yl)benzimidazole and p-toluate ligands, leading to an infinite ribbon-like double-chain packing mode. The complete solid-state structure can be described as a three-dimensional supra-molecular framework, stabilized by these inter-molecular hydrogen-bonding inter-actions and possible C - H...π inter-actions, as well as stacking inter-actions involving the 2-(2-pyrid-yl)benzimidazole ligands. International Union of Crystallography 2007.

Full text of DOI:10.1107/S0108270107055023

metal-organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
into the structural aspects that may influence the mechanism
of action of the enzyme active sites. As far as we are aware, for
the great majority of six-coordinate Mn complexes with
carboxylate ligation, the number of carboxylate ligands acting
as a chelating ligand usually remains low so as to avoid (or
reduce) the strain from small-angle chelation (the chelation
angle is usually less than 60ꢀ), and thus far reports of mono-
nuclear complexes with more than two carboxylate ligands
chelating an octahedral Mn centre have been rare (Jha &
Mishra, 1986; Chai et al., 2004; Moubaraki et al., 2003). In the
present paper, we report the structure of the title compound,
(I), which is a rare example of a mononuclear manganese
complex with three chelating ligands, including a pair of
chelating carboxylate ligands and a third chelating imidazole-
containing ligand, simultaneously in the coordination envir-
onment. A mononuclear seven-coordinate MnII complex with
a similar chelating ligand situation has recently been reported
(Viossat et al., 2003).
ISSN 0108-2701
[2-(2-Pyridyl)-1H-benzimidazole-
j2N2,N3]bis(p-toluato-j2O,O0)-
manganese(II)
Cheng-Bing Ma, Chang-Neng Chen* and Qiu-Tian Liu
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the
Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, People’s
Republic of China
Correspondence e-mail: ccn@fjirsm.ac.cn
Received 3 October 2007
Accepted 31 October 2007
Online 30 November 2007
In the title compound, [Mn(C8H7O2)2(C12H9N3)], the manga-
nese(II) centre is surrounded by three bidentate chelating
ligands, namely, one 2-(2-pyridyl)benzimidazole ligand [Mn—
˚
N = 2.1954 (13) and 2.2595 (14) A] and two p-toluate ligands
˚
[Mn—O = 2.1559 (13)–2.2748 (14) A]. It displays a severely
distorted octahedral geometry, with cis angles ranging from
58.87 (4) to 106.49 (5)ꢀ. Intermolecular C—Hꢁ ꢁ ꢁO hydrogen
bonds between the p-toluate ligands link the molecules into
infinite chains, and every two neighbouring chains are further
coupled by N—Hꢁ ꢁ ꢁO and C—Hꢁ ꢁ ꢁO hydrogen bonds
between the 2-(2-pyridyl)benzimidazole and p-toluate ligands,
leading to an infinite ribbon-like double-chain packing mode.
The complete solid-state structure can be described as a three-
dimensional supramolecular framework, stabilized by these
intermolecular hydrogen-bonding interactions and possible
C—Hꢁ ꢁ ꢁꢀ interactions, as well as stacking interactions
involving the 2-(2-pyridyl)benzimidazole ligands.
Compound (I) consists of neutral [Mn(ptl)2(pybim)]
monomers [ptl is p-toluate and pybim is 2-(2-pyridyl)benz-
imidazole] lying in a crystallographic general position. The
MnII atom is coordinated to one bidentate chelating pybim
ligand via atoms N1 and N2, and to a pair of anionic bidentate
chelating ptl ligands via atoms O1, O2, O3 and O4, as shown in
Fig. 1. The complex displays a highly distorted octahedral
Comment
Low molecular weight manganese carboxylate species play an
important role at the active sites of various redox-based
enzymes (Weighardt, 1989). Mn superoxide dismutase, Mn
peroxidase and Mn dioxygenase are each believed to contain a
mononuclear Mn site, which participates in the redox changes
of biological systems (Law et al., 1999). X-ray crystallography
reveals that the peripheral ligation around the Mn centre in
these enzymes includes both carboxylate groups in various
binding modes and the imidazole rings from various amino
acid residues (Pecoraro & Butler, 1986), suggesting that
changes in the carboxylate binding mode may be important to
the action of these enzymes (Rardin et al., 1991). Carboxyl-
and imidazole-containing molecules are often employed to
prepare simple models for the active sites of these enzymes.
Understanding the structural effects of imidazole ligation to
the Mn centre and the different carboxylate binding modes in
these models will undoubtedly be helpful in gaining insight
Figure 1
A view of the molecule of (I), showing the atomic labelling scheme and
30% probability displacement ellipsoids. H atoms are shown as small
spheres of arbitrary radii.
m618 # 2007 International Union of Crystallography
doi:10.1107/S0108270107055023
Acta Cryst. (2007). C63, m618–m621

metal-organic compounds
˚
(pybim)2] [Ac is acetyl; 2.197 (2) and 2.394 (2) A, and
72.72 (6)ꢀ, respectively; Tangoulis et al., 1996]. The Mn—
N(imidazole) distance in both compounds, perceptibly shorter
than the Mn—N(pyridine) distance, indicates that the imida-
zole N atom of the pybim ligand is a stronger donor, since the
benzene group in the ortho position enhances the electron
density on this N atom. The Mn—O distances and O—Mn—O
carboxylate chelate angles are as expected for MnII complexes
with a similar coordination environment (Chai et al., 2004;
Moubaraki et al., 2003; Viossat et al., 2003; Baumeister &
Hartung 1997; Jha & Mishra, 1986).
The two chelate ring planes formed by the ptl ligands, viz.
O1/C7/O2/Mn1 and O3/C15/O4/Mn1, with a maximum out-of-
˚
plane deviation of 0.027 (1) A for atom C7, are each almost
coplanar with the respective attached methylphenyl planes
[C1–C6/C8 and C9–C14/C16, respectively], as indicated by the
small dihedral angles of 7.9 (6) and 3.4 (1)ꢀ, respectively. The
pybim ligand and the pybim chelate ring (N1/C23/C24/N2/
Mn1) are each reasonably planar, with a maximum out-of-
Figure 2
Aview of (I), showing the coplanarity of the central metal atom with each
of the ligands and the approximately perpendicular interpenetration of
the mean planes.
˚
plane deviation of 0.096 (6) A for atom H28A and a very small
dihedral angle of 3.3 (1)ꢀ observed between them, suggesting
that the pybim plane can be extended to involve atom Mn1.
The three Mn1-containing mean planes, denoted P1 (C1–C8/
O1/O2/Mn1), P2 (C9–C16/O3/O4/Mn1) and P3 (C17–C28/
N1–N3/Mn1), with maximum out-of-plane deviations of
geometry around the Mn centre (Table 1), in which three O
atoms (O1, O2 and O3) of the tpl ligands and one pyridyl N
atom (N2) of the pybim ligand define the equatorial plane,
with atom Mn1 displaced from the least-squares O1–O3/N2
˚
plane by 0.163 (2) A. Imidazole atom N1 of the pybim ligand
˚
˚
˚
0.137 (6) A for atom O1, 0.062 (1) A for C10 and 0.085 (9) A
for Mn1, respectively, make P1/P2, P3/P1 and P3/P2 dihedral
angles of 87.2 (2), 83.8 (6) and 71.0 (4)ꢀ, respectively, indi-
cating the approximate perpendicularity of these planes to one
another (Fig. 2).
and atom O4 of the tpl ligand complete the distorted octa-
hedron through coordination in the axial positions, with an
N1—Mn1—O4 angle of 155.83 (5)ꢀ.
The Mn—N distances and N—Mn—N pybim chelate angle
(Table 1) are comparable to those observed in the only
reported pybim-containing MnII complex, viz. [Mn3(AcO)6-
The high-spin d5 Mn2+ ion usually favours the formation of
the octahedral d2sp3 hybrid orbital, with
cis angles equal to 90ꢀ. The chelating
carboxylate group usually gives
a
narrow bite of less than 60ꢀ at the
central Mn atom, thus resulting in the
distortion of the coordination environ-
ment, and the higher the number of
chelating carboxylate groups, the more
distorted the central metal coordination
environment and the more unstable the
complex in keeping an octahedral
coordination. Thus far, mononuclear
Mn complexes with more than two
chelating carboxylate groups have
therefore rarely been encountered. The
strong distortion deviating from an ideal
Mn octahedron in (I), with the cis angles
subtended at the Mn atom ranging from
58.87 (4) to 106.49 (5)ꢀ, is obviously due
to the triple narrow bite of the three
chelating ligands. The title compound
provides a rare example of a six-
coordinate Mn compound with an
added N,N0-chelating ligand besides two
chelating carboxylate ligations, though
several similar complexes are found to
Figure 3
A packing diagram for (I), showing part of the one-dimensional hydrogen-bonded ribbon-shaped
double-chain network. Atoms labelled with a dollar sign ($), a hash (#) or an ampersand (&) are at
the symmetry positions (x – 1, y, z), (x + 1, y, z) and (–x, –y + 1, –z + 1), respectively. H atoms not
involved in the hydrogen bonding have been omitted.
ꢂ
Acta Cryst. (2007). C63, m618–m621
Ma et al. [Mn(C8H7O2)2(C12H9N3)] m619

metal-organic compounds
Figure 4
Aview of the partial ꢀ–ꢀ stacking interactions between the pyridine rings
of the pybim ligands in (I).
Figure 6
A partial packing diagram of (I), showing the formation of the three-
dimensional supramolecular framework. Hydrogen-bonding and C—
Hꢁ ꢁ ꢁꢀ interactions are depicted as dashed lines. H atoms not involved in
the intermolecular interactions have been omitted for clarity.
generate infinite one-dimensional chains with the pybim
ligands located at the same side of the chain (Fig. 3). Two
molecules of neighbouring chains are further coupled via an
N3—H3Bꢁ ꢁ ꢁO2i [symmetry code: (i) –x, –y + 1, –z + 1]
hydrogen bond and a fifth weak C25—H25Aꢁ ꢁ ꢁO2i hydrogen
bond to generate a centrosymmetric dimer (Fig. 3), thus
resulting in the formation of an infinite hydrogen-bonded
ribbon-shaped double-chain network (Fig. 3). All the pybim
ligands are located within the region of the hydrogen-bonded
ribbon network, in which a normal and a weaker ꢀ–ꢀ stacking
˚
interaction (3.4 A; Bondi, 1964) between inversion-related
pybim ligands are observed (Fig. 4), with perpendicular pybim
˚
plane separations of 3.498 (4) and 3.669 (7) A, respectively.
Three C—Hꢁ ꢁ ꢁꢀ interactions, with Hꢁ ꢁ ꢁCg distances of less
Figure 5
ꢀ
˚
A partial packing diagram of (I), showing the three symmetry-
independent C—Hꢁ ꢁ ꢁꢀ interactions. The ꢀ-ring centroids (Cg1 and
Cg2) labelled with a percent sign (%), an asterisk (*) or a plus sign (+) are
than 3 A (Cg is the centroid of the ꢀ ring) and ꢁ less than 30
(ꢁ is the angle formed by the Hꢁ ꢁ ꢁCg vector and the normal to
the ꢀ-ring plane) (Spek, 2003) are also observed within the
structure of (I) (Table 2). These C—Hꢁ ꢁ ꢁꢀ interactions link
the monomer to adjacent symmetry-related monomers (Fig. 5)
and complete an overall three-dimensional supramolecular
network (Fig. 6). These intermolecular interactions together
with numerous other van der Waals contacts ensure the solid-
state crystalline cohesion of the title compound.
at the symmetry positions (1 + x, 12 ꢃ y, 21 + z), (1 ꢃ x, ꢃ + y, 21 ꢃ z) and
1
2
1
(ꢃx, ꢃ + y, 12 ꢃ z), respectively. Cg1 denotes the centroid of the C1–C6
2
ring and Cg2 denotes the centroid of the C9–C14 ring. H atoms not
involved in C—Hꢁ ꢁ ꢁꢀ interactions have been omitted.
have two added monodentate ligands in a more regular
octahedral Mn coordination (Jha & Mishra, 1986; Chai et al.,
2004; Moubaraki et al., 2003). Two seven-coordinate
complexes with a di- or mononuclear Mn centre have also
been previously reported to possess a similar chelating ligand
set, in which the central Mn coordination environments are
approximately described as distorted capped octahedra
(Viossat et al., 2003; Baumeister & Hartung, 1997).
As listed in Table 2, one normal intermolecular N—Hꢁ ꢁ ꢁO
hydrogen bond and five nonclassical intermolecular C—
Hꢁ ꢁ ꢁO hydrogen bonds are observed in the crystal structure.
Four benzene C atoms (C5, C6, C10 and C11) in one molecule
donate their H atoms to the carboxyl O atoms (O1, O3, O2
and O4, respectively) of two symmetry-related molecules to
Experimental
2-(2-Pyridyl)benzimidazole (1 mmol) dissolved in ethanol (15 ml)
was added dropwise to an ethanol–dimethylformamide solution
(30 ml, ca 1:1 v/v) containing manganese p-toluate tetrahydrate
(1 mmol), with continuous stirring. The mixture was refluxed for 1 h
and then filtered. The yellow filtrate was allowed to stand undisturbed
for several weeks at room temperature, during which time yellow
crystals of (I) suitable for X-ray diffraction analysis were deposited.
Analysis calculated for C28H23MnN3O4: C 64.62, H 4.45, N 8.07%;
found C 64.47, H 4.55, N 8.11%. FT–IR (KBr, cmꢃ1): 3066 (m),
ꢂ
m620 Ma et al. [Mn(C8H7O2)2(C12H9N3)]
Acta Cryst. (2007). C63, m618–m621

metal-organic compounds
2922 (w), 1618 (s), 1587 (s), 1520 (vs), 1412 (vs), 1311 (m), 1299 (m),
1194 (m), 1058 (w), 980 (m), 863 (s), 787 (m), 774 (s), 746 (s), 622 (s),
544 (w), 486 (w).
Table 1
Selected geometric parameters (A, ).
ꢀ
˚
Mn1—O3
Mn1—N1
Mn1—O1
2.1559 (13)
2.1954 (13)
2.2268 (13)
Mn1—O2
Mn1—N2
Mn1—O4
2.2370 (13)
2.2595 (14)
2.2748 (14)
Crystal data
3
˚
[Mn(C8H7O2)2(C12H9N3)]
Mr = 520.43
Monoclinic, P21=c
V = 2442.3 (11) A
Z = 4
O3—Mn1—N1
O3—Mn1—O1
N1—Mn1—O1
O3—Mn1—O2
N1—Mn1—O2
O1—Mn1—O2
O3—Mn1—N2
N1—Mn1—N2
102.06 (5)
101.12 (4)
104.44 (5)
154.21 (4)
98.99 (4)
58.87 (4)
106.49 (5)
74.45 (5)
O1—Mn1—N2
O2—Mn1—N2
O3—Mn1—O4
N1—Mn1—O4
O1—Mn1—O4
O2—Mn1—O4
N2—Mn1—O4
152.00 (5)
93.35 (5)
59.32 (4)
155.83 (5)
94.87 (5)
103.43 (4)
95.17 (5)
Mo Kꢃ radiation
ꢄ = 0.58 mmꢃ1
T = 295 (2) K
˚
a = 7.582 (2) A
˚
b = 17.482 (5) A
˚
c = 18.731 (5) A
0.46 ꢄ 0.42 ꢄ 0.20 mm
ꢂ = 100.368 (4)ꢀ
Data collection
Table 2
Hydrogen-bond geometry (A, ).
Rigaku Mercury CCD
diffractometer
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
Tmin = 0.760, Tmax = 0.890
18797 measured reflections
5561 independent reflections
4584 reflections with I > 2ꢅ(I)
Rint = 0.027
ꢀ
˚
Cg1 and Cg2 are defined in the caption to Fig. 5.
D—Hꢁ ꢁ ꢁA
D—H
Hꢁ ꢁ ꢁA
Dꢁ ꢁ ꢁA
D—Hꢁ ꢁ ꢁA
N3—H3Bꢁ ꢁ ꢁO2i
0.88 (2)
0.93
0.93
0.93
0.93
0.93
0.93
0.93
0.93
2.18 (2)
2.57
2.42
2.44
2.54
2.55
2.90
2.79
2.91
2.9882 (19)
3.442 (2)
3.196 (2)
3.345 (2)
3.426 (2)
3.351 (2)
3.794 (1)
3.654 (3)
3.712 (1)
153.3 (18)
157
141
166
158
145
163
155
145
C5—H5Aꢁ ꢁ ꢁO1ii
Refinement
C6—H6Aꢁ ꢁ ꢁO3ii
R[F2 > 2ꢅ(F2)] = 0.036
wR(F2) = 0.105
S = 1.00
5561 reflections
331 parameters
H atoms treated by a mixture of
independent and constrained
refinement
C10—H10Aꢁ ꢁ ꢁO2iii
C11—H11Aꢁ ꢁ ꢁO4iii
C25—H25Aꢁ ꢁ ꢁO2i
C13—H13Aꢁ ꢁ ꢁCg1iv
C26—H26Aꢁ ꢁ ꢁCg2v
C27—H27Aꢁ ꢁ ꢁCg1vi
ꢃ3
˚
Áꢆmax = 0.22 e A
ꢃ3
˚
Áꢆmin = ꢃ0.30 e A
Symmetry codes: (i) ꢃx; ꢃy þ 1; ꢃz þ 1; (ii) x ꢃ 1; y; z; (iii) x þ 1; y; z; (iv)
H atoms on phenyl/pyridyl rings and methyl groups were placed in
˚
calculated positions, with C—H distances of 0.93 and 0.96 A,
1
2
1
2
1
2
1
2
1
2
1
2
x þ 1; ꢃy ꢃ ; z ꢃ ; (v) ꢃx þ 1; y ꢃ ; ꢃz þ ; (vi) ꢃx; y ꢃ ; ꢃz þ .
respectively, and were included in the final cycles of refinement as
riding [Uiso(H) = 1.2Ueq(C) and 1.5Ueq(C), respectively]. The H atom
on the imidazole N atom was located from difference maps and
refined isotropically.
References
Baumeister, U. & Hartung, H. (1997). Acta Cryst. C53, 1246–1248.
Bondi, A. (1964). J. Phys. Chem. 68, 441–451.
Data collection: CrystalClear (Rigaku, 2000); cell refinement:
CrystalClear; data reduction: CrystalClear; program(s) used to solve
structure: SHELXTL (Sheldrick, 1997); program(s) used to refine
structure: SHELXTL; molecular graphics: SHELXTL; software used
to prepare material for publication: SHELXTL and PLATON (Spek,
2003).
Chai, J.-F., Zhu, H.-P., Peng, Y., Roesky, H. W., Singh, S., Schmidt, H.-G. &
Noltemeyer, M. (2004). Eur. J. Inorg. Chem. pp. 2673–2677.
Jha, R. R. & Mishra, H. C. (1986). Chim. Acta Turc. 14, 51–58.
Law, N. A., Caudle, M. T. & Pecoraro, V. L. (1999). Adv. Inorg. Chem. 46, 305–
440.
Moubaraki, B., Murray, K. S. & Tiekink, E. R. T. (2003). Z. Kristallogr. New
Cryst. Struct. 218, 351–353.
Pecoraro, V. L. & Butler, W. M. (1986). Acta Cryst. C42, 1151–1154.
Rardin, R. L., Tolman, W. B. & Lippard, S. J. (1991). New J. Chem. 15, 417–430.
Rigaku (2000). CrystalClear. Version 1.3.5. Rigaku Corporation, Tokyo, Japan.
This work was supported by the NNSFC (grant Nos.
20471061 and 20633020) and the Fujian Province Youth
Foundation (grant No. 2005 J059).
¨
Sheldrick, G. M. (1996). SADABS. University of Gottingen, Germany.
Sheldrick, G. M. (1997). SHELXTL. University of Gottingen, Germany.
¨
Spek, A. L. (2003). J. Appl. Cryst. 36, 7–13.
Tangoulis, V., Malamatari, D. A., Soulti, K., Stergiou, V., Raptopoulou, C. P.,
Terzis, A., Kabanos, T. A. & Kessissoglou, D. P. (1996). Inorg. Chem. 35,
4974–4983.
Viossat, V., Lemoine, P., Dayan, E., Dung, N.-H. & Viossat, B. (2003).
Polyhedron, 22, 1461–1470.
Weighardt, K. (1989). Angew. Chem. Int. Ed. Engl. 28, 1153–1172.
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: SK3169). Services for accessing these data are
described at the back of the journal.
ꢂ
Acta Cryst. (2007). C63, m618–m621
Ma et al. [Mn(C8H7O2)2(C12H9N3)] m621