Synthesis and crystal structure of metal complexes based on 2,6-bis(6-methylquinolin-2-yl)pyridine ligand

Article abstract of DOI:10.1134/S1070328413090030

Two mononuclear five-coordinated transition metal complexes FeLCl ₂ (I) and MnLCl₂ (II) containing tridentate 2,6-bis(6-methylquinolin-2-yl)pyridine ligand (L) have been synthesized and characterized by single-crystal X-ray crystallography. In the complexes, the metal center was tridentately chelated by ligand and further coordinated by two chlorine atoms, resulting in distorted trigonal-bipyramidal geometry for complex I and II, respectively. In addition, crystal packing in complex is stabilized by C-H...Cl intermolecular hydrogen bond, which link the mononuclear complex to the 1D chain.

Full text of DOI:10.1134/S1070328413090030

ISSN 1070ꢀ3284, Russian Journal of Coordination Chemistry, 2013, Vol. 39, No. 9, pp. 650–654. © Pleiades Publishing, Ltd., 2013.
Synthesis and Crystal Structure of Metal Complexes Based
on 2,6ꢀbis(6ꢀMethylquinolinꢀ2ꢀyl)pyridine Ligand1
Y. Y. Lia, b, X. P. Lia, G. Zhanga, Y. F. Wanga, R. L. Zhanga, and J. S. Zhaoa, *
a Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education,
Shaanxi Key Laboratory of PhysicoꢀInorganic Chemistry, College of Chemistry & Material Science,
Northwest University, Xi’an, Shaanxi, 710069 P.R. China
b College of Chemistry and Chemical Engineering, Longdong University, Qingyang, Gansu, 745000 P.R. China
*eꢀmail: jszhao@nwu.edu.cn
Received January 10, 2012
Abstract—Two mononuclear fiveꢀcoordinated transition metal complexes FeLCl2 (I) and MnLCl2 (II) conꢀ
taining tridentate 2,6ꢀbis(6ꢀmethylquinolinꢀ2ꢀyl)pyridine ligand (L) have been synthesized and characterꢀ
ized by singleꢀcrystal Xꢀray crystallography. In the complexes, the metal center was tridentately chelated by
ligand and further coordinated by two chlorine atoms, resulting in distorted trigonalꢀbipyramidal geometry
for complex I and II, respectively. In addition, crystal packing in complex is stabilized by C–H⋅⋅⋅Cl intermoꢀ
lecular hydrogen bond, which link the mononuclear complex to the 1D chain.
DOI: 10.1134/S1070328413090030
1
INTRODUCTION
by one pyridine atom and two N atoms of the quinoꢀ
line group, and two chlorine atoms, forming distorted
trigonalꢀbiyramid geometry.
Hydro(solvo)thermal syntheses carried out in suꢀ
perheated solvent systems provides ideal conditions
for the crystal growth owing to the enhanced transport
ability of the solvents [1–6]. Besides, recent studies reꢀ
vealed that crystal growth under hydro(solvo)thermal
conditions occasionally involves in situ ligand synthesis
which not only provides a powerful synthesis method
for organic ligands which are difficult to synthesize but
also represents a potential new direction for novel inorꢀ
ganicꢀorganic hybrid network construction through
crystal engineering [7]. In the present paper, we report
the syntheses and crystal structures of two novel tranꢀ
sition metal complexes bearing tridentate 2,6ꢀbis(6ꢀ
EXPERIMENTAL
2,6ꢀPyridinedicarboxaldehyde was prepared by oxꢀ
idation of 2,6ꢀpyridinemethanol with activated MnO2
according to the procedure described in the literature
[10]. All reagents used in the syntheses were of analytꢀ
ical grade and used without further purification as reꢀ
ceived. Elemental analyses for carbon, hydrogen and
nitrogen were performed on a VarioEL III elemental
analyzer. 1H NMR data were collected from INOVAꢀ
400 MHz NMR system. The infrared spectra (4000–
400 cm–1) were recorded by using KBr pellet on a
BRUKER EQUINOXꢀ55 IR spectrometer.
methylquinolinꢀ2ꢀyl)pyridine ligand (L) under solvoꢀ
thermal conditions. During the course of the solvoꢀ
thermal treatment, new carbon–carbon bond would
format through reductive coupling or oxidative couꢀ
pling [8, 9]. Herein, ethanol and ligand 2,6ꢀbis
tolylimino)pyridine (
carbon bond connecting imino group and benzene to
form a hexatomic ring and new ligand 2,6ꢀbis(6ꢀmethꢀ
ylquinolinꢀ2ꢀyl)pyridine L was obtained. Conseꢀ
quently, treatment of the chelate schiffꢀbase ligand L1
with FeCl2 or MnCl2 yielded the corresponding metal
complexes I and II. These complexes were characterꢀ
ized by Xꢀray single crystal diffraction. The Fe atom
and Mn atom in the complexes are fiveꢀcoordinated
Synthesis of the ligand L1.
pꢀToluidime (0.5397 g,
(pꢀ
1) produced the new carbon–
5.0 mmol) dissolved in ethanol (10 mL) was added to
a solution of 2,6ꢀpyridine dicarboxaldehyde (0.3313 g,
2.5 mmol) in ethanol (6.0 mL). The solution was reꢀ
fluxed for 3 h after addition of several drops glacial
acetic acid. Then the solution was cooled to room
temperature and filtered. Residue was washed with
hexane. The product was crystallized from ethanol by
recrystallization. Finally, the light yellow needleꢀlike
particles were dried in vacuo. The yield was 69.7%,
L
m.p. 178.8–179.3
°
ppm): 8.44 (d., = 7.3 Hz, 2H), 8.19 (t.,
C. 1H NMR (400 MHz; CDCl3;
= 7.6 Hz,
δ,
1
The article is published in the original.
J
J
650

SYNTHESIS AND CRYSTAL STRUCTURE OF METAL COMPLEXES
651
x
C(10)
y
C(11)
z
C(9)
C(12)
C(13)
C(14)
C(8)
C(6)
C(15)
C(16)
N(2)
C(7)
C(5)
C(4)
N(3)
C(21)
N(1)
Fe(1)
C(17)
C(23)
Cl(1)
C(3)
Cl(2)
C(20)
C(24)
C(2)
C(18)
C(19)
C(25)
C(22)
C(1)
Fig. 1. The crystal structure of complex I.
1H), 7.75 (s., 2H), 7.55 (d.,
1H), 2.42 (s., 6H).
J
= 8.4 Hz, 8H), 3.71 (s.,
Xꢀray crystallography. Single crystal of the
complex and II were put on a Bruker SMART
APEX II CCD diffractometer equipped with a graphꢀ
iteꢀmonochromated Mo radiation ( = 0.71073
scan technique at room temperature.
The structure was solved by direct methods with
SHELXSꢀ97 [11]. The hydrogen atoms were assigned
with common isotropic displacement factors and inꢀ
cluded in the final refinement by use of geometrical reꢀ
strains, while the nonꢀhydrogen atoms were treated
with common anisotropic displacement factors and
included in the final refinement with geometrical reꢀ
strains. A fullꢀmatrix leastꢀsquares refinement on F2
was carried out using SHELXLꢀ97 [12]. The final
I
For C21H19N3
K
λ
Å)
α
by using a
φ/ω
anal. calcd., %: C, 80.48;
H, 6.110;
H, 6.094;
N, 13.41.
N, 13.34.
Found, %:
C, 79.62;
IR spectrum (KBr;
, cm–1): 3168, 1612, 1471, 1429,
ν
1268, 962, 815, 763.
Synthesis of I. 2,6ꢀBis
(0.0160 g, 0.05 mmol) and FeCl2
0.05 mmol) along with four drops of 0.1 M hydrochloꢀ
ric acid were dissolved in ethanol (10 mL). The mixꢀ
ture was heated in a Teflonꢀlined, stainlessꢀsteel Parr
bomb at 373 K for 120 h. The bomb was cooled at 5 K
per hour. Deep red crystals were obtained.
(pꢀtolylimino)pyridine
⋅
4H2O (0.0197 g,
agreement factor values for complex
and wR = 0.1095; for complex II are
I
R
are
R = 0.0413
= 0.0710 and
wR = 0.1468. Crystallographic data and refinement
parameters are listed in Table 1. The atomic coordiꢀ
nates and other parameters of the complexes have been
deposited with the Cambridge Crystallographic Data
For C25H19N3Cl2Fe
anal. calcd., %: C, 61.51;
H, 3.92;
N, 8.61.
Centre (nos. 783341 (I) and 830837 (II); deposꢀ
it@ccdc.cam.ac.uk).
Found, %:
C, 62.03;
H, 3.556;
N, 8.392.
IR spectrum (KBr;
, cm–1): 3172, 1602, 1471, 1409,
1268, 968, 819, 763, 592.
ν
RESULTS AND DISCUSSION
Xꢀray single crystal diffraction analysis reveals that
Synthesis of II. 2,6ꢀBis
(
p
ꢀtolylimino)pyridine
⋅
(0.0160 g, 0.05 mmol), and MnCl2
4H2O (0.0143 g,
0.05 mmol) along with five drops of 0.1 M hydrochloꢀ
ric acid were dissolved in ethanol (10 mL). The mixꢀ
ture was heated in a Teflonꢀlined, stainlessꢀsteel Parr
bomb at 373 K for 120 h. The bomb was cooled at 5 K
per hour. Orange red crystals were obtained.
complexes and II almost have the same coordination
geometry. Therefore, we just describe complex as folꢀ
low. The crystal structure of complex is shown in
Fig. 1, and selected bond distances and angles were
given in Table 2. Complex displays an approximate C2
I
I
I
I
symmetry about a plane containing the iron atom, the
two chlorine atoms, and the pyridyl nitrogen atom
[13]. The central pyridine ring, iron ion and two quinꢀ
oline groups are approximate in the same plane. The
For C25H19N3Cl2Mn
anal. calcd., %: C, 61.62;
H, 3.93;
N, 8.62.
Found, %:
C, 61.83;
H, 4.186;
N, 8.986.
iron ion is in the center by 0.046
coordinated plane. And the Fe atom, two chlorine atꢀ
oms and pyridyl nitrogen atom are in the same plane,
Å deviate from this
IR spectrum (KBr;
, cm–1): 3214, 1600, 1471, 1415,
1376, 998, 815, 763, 630.
ν
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 39
No. 9
2013

652
LI et al.
Table 1. Crystal data and structure refinement information for compounds
I
and II
Value
Parameter
I
II
Formular weight
Crystal system
488.18
487.27
Triclinic
Triclinic
Crystal size, mm
0.28
×
0.19
×
0.09
0.31
×
0.25 × 0.14
Space group
P
1
P1
a
, Å
, Å
9.6702(13)
9.7165(12)
b
10.3085(14)
11.0076(14)
95.055(2)
95.535(2)
95.806(2)
2; 1081.3(2)
1.499
10.4342(14)
10.8126(14)
95.572(2)
97.714(2)
95.310(2)
2; 1075.0(2)
1.505
c
, Å
, deg
α
β
λ
Z
, deg
, deg
; volume, Å3
ρcalcd, g/cm3
), mm–1
μ(Mo
K
0.963
0.881
α
F(000)
500
498
θ
Range, deg
1.87–25.10
1.91–25.09
Limiting indices
Reflections collected
Reflections with > 2
h
,
k
,
l
–11 <
h
< 9, –12 <
k
< 12, –13 <
l
< 10 –11 <
h
< 11, –12 <
k
< 12, –12 <
l
< 10
5479
5467
I
σ
(I
)
2877
2955
Independent reflections (Rint
Data/restraints/parameters
Goodnessꢀofꢀfit on F2
)
3787(0.0184)
3787/0/282
1.080
3783(0.0238)
3783/0/282
1.094
Final
R
indices (
I
> 2σ(I
))
R
= 0.0413, wR = 0.1095
= 0.0582, wR = 0.1302
–0.221/0.336
R
= 0.0710, wR = 0.1468
= 0.0912, wR = 0.1578
–0.528/0.919
R
indices (all data)
Å–3
R
R
Δρmin/Δρmax, e
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 39
No. 9
2013

SYNTHESIS AND CRYSTAL STRUCTURE OF METAL COMPLEXES
653
y
z
x
Cl
Cl
Fe
Fe
N
N
Fig. 2. 1D chain coordination motif of complex I.
C(12)
x
z
C(13)
C(14)
C(11)
C(10)
y
C(16)
C(8)
C(17)
C(18)
C(15)
N(2)
N(3)
C(9)
N(1)
C(7)
C(6)
Mn(1)
C(23)
C(19)
C(1)
C(5)
Cl(2)
Cl(1)
C(22)
C(4)
C(2)
C(20)
C(24)
C(3)
C(21)
C(25)
Fig. 3. The crystal structure of complex II
.
the dihedral angle between the ligand plane (N(1), ridyl nitrogen atom forming the equatorial plane [14].
N(2), N(3)) and the equatorial plane (Cl(1), Cl(2), The bond length of Fe(1)–Cl(2) (2.3488(11) ) is
N(3)) is 89.78(2) . The coordination geometry of the longer than that of Fe(1)–Cl(1) (2.2793(11) ), which
Å
°
Å
central iron ion can be described as distorted trigonalꢀ can be ascribed to apical elongation in the squareꢀpyꢀ
bipyramidal, with the two chlorine atoms and the pyꢀ ramidal complex. The equatorial angles range in
y
x
Cl
Cl
z
N
N
Mn
Mn
N
N
Fig. 4. 1D chain coordination motif of complex II
.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 39 No. 9 2013

654
LI et al.
Table 2. The selected bond lengths (Å) and bond angles
118.22(4)
bonds subtend an angle of 148.567(79)
ular hydrogen bonds are also found in the crystal of
Figure 2 shows the molecular arrangement of . The
°
–121.492(80)
°
, and the two axial Fe–N
(deg) for
I
and II
°. Intermolecꢀ
I.
I
II
I
C–H group in the benzene ring plays a key role. The
intermolecular hydrogen bonds occur between C–H
Bond
d, Å
Bond
d, Å
and coordinated chlorine atom (2.7760
C⎯H
as 1D chain structure by the intermolecular hydrogen
bonds [15]. In addition, the crystal structure and 1D
chain structure of complex II are shown in Figs. 3
and 4, respectively.
Å for
⋅⋅⋅Cl). Thus the units of FeLCl2 were connected
Fe(1)–N(1)
Fe(1)–N(2)
Fe(1)–N(3)
Fe(1)–Cl(1)
Fe(1)–Cl(2)
N(1)–C(7)
N(1)–C(23)
N(2)–C(12)
N(2)–C(8)
N(3)–C(13)
N(3)–C(21)
C(1)–C(2)
2.255(3)
2.100(3)
2.246(3)
Mn(1)–N(1)
Mn(1)–N(3)
Mn(1)–N(2)
2.339(4)
2.192(4)
2.312(4)
2.3319(18)
2.3747(17)
1.301(6)
1.401(6)
1.319(6)
1.382(6)
1.340(6)
1.343(6)
1.392(7)
2.2793(12) Mn(1)–Cl(1)
2.3488(10) Mn(1)–Cl(2)
ACKNOWLEDGMENTS
1.335(4)
1.370(4)
1.342(4)
1.351(4)
1.324(4)
1.376(4)
1.510(5)
N(1)–C(9)
N(1)–C(1)
N(2)–C(15)
N(2)–C(23)
N(3)–C(14)
N(3)–C(10)
C(1)–C(2)
We gratefully acknowledge financial support of this
work by the National Natural Science Foundation of
China (nos. 20972104 and 21171139) and the
National Science and Technology Pillar Program of
China (no. 2007BAB17B02).
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ö
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2013