Crystal structures of azido or thiocyanato-coordinated nickel(II) complexes with tridentate Schiff bases

Article abstract of DOI:10.1134/S0022476613050120

A new azido-coordinated nickel(II) complex [NiL¹(N₃)] (1) and a new thiocyanato-coordinated nickel(II) complex [NiL²(NCS)] (2), where L¹ and L² are the monoanionic forms of Schiff bases 2-[(2-isopropylaminoethylimino)methyl]-6-methylphenol and 2-[(2-dimethlaminoethylimino)methyl]-6-methylphenol respectively, are prepared and structurally characterized by elemental analysis, IR spectra, and single crystal X-ray crystallography. Complex 1 crystallizes in the triclinic space group P-1 with unit cell dimensions a = 8.812(2) A, b = 9.433(3) A, c = 9.488(2) A, α = 81.933(2), β = 69.925(2), γ = 84.591(2), V = 732.5(3) A³, Z = 2, R ₁ = 0.0291, and wR ₂ = 0.0734. Complex 2 crystallizes in the monoclinic space group P2₁/n with unit cell dimensions a = 7.4497(4) A, b = 6.1933(3) A, c = 31.5126(18) A, β = 92.484(2), V = 1452.57(13) A³, Z = 4, R ₁ = 0.0307, and wR ₂ = 0.0668. The Ni atom in each of the complexes is coordinated by three donor atoms of the Schiff base ligand and by one N atom of the azide or thiocyanate ligand, forming a square planar geometry. The azide and thiocyanate anions readily coordinate to the complexes as secondary ligands.

Full text of DOI:10.1134/S0022476613050120

Journal of Structural Chemistry. Vol. 54, No. 5, pp. 926-930, 2013
Original Russian Text Copyright © 2013 by S.-S. Qian, M. Zhang, Z.-L. You, H.-L. Zhu
CRYSTAL STRUCTURES OF AZIDO OR THIOCYANATO-
COORDINATED NICKEL(II) COMPLEXES
WITH TRIDENTATE SCHIFF BASES
1
S.-S. Qian, M. Zhang, Z.-L. You, and H.-L. Zhu
2
2
1
UDC 548.73:547.13:546.74
©
1
A new azido-coordinated nickel(II) complex [NiL (N )] (1) and a new thiocyanato-coordinated nickel(II)
3
2
complex [NiL (NCS)] (2), where L and L are the monoanionic forms of Schiff bases 2-[(2-
1
2
isopropylaminoethylimino)methyl]-6-methylphenol and 2-[(2-dimethlaminoethylimino)methyl]-6-
methylphenol respectively, are prepared and structurally characterized by elemental analysis, IR spectra,
and single crystal X-ray crystallography. Complex 1 crystallizes in the triclinic space group P-1 with unit
cell dimensions a = 8.812(2) Å, b = 9.433(3) Å, c = 9.488(2) Å, α = 81.933(2)°, β = 69.925(2)°,
3
γ = 84.591(2)°, V = 732.5(3) Å , Z = 2, R = 0.0291, and wR = 0.0734. Complex 2 crystallizes in the
1
2
monoclinic space group P2 /n with unit cell dimensions a = 7.4497(4) Å, b = 6.1933(3) Å,
1
3
c = 31.5126(18) Å, β = 92.484(2)°, V = 1452.57(13) Å , Z = 4, R = 0.0307, and wR = 0.0668. The Ni
1
2
atom in each of the complexes is coordinated by three donor atoms of the Schiff base ligand and by one N
atom of the azide or thiocyanate ligand, forming a square planar geometry. The azide and thiocyanate
anions readily coordinate to the complexes as secondary ligands.
DOI: 10.1134/S0022476613050120
Keywords: Schiff base, nickel complex, azide, thiocyanate, crystal structure.
INTRODUCTION
The Schiff bases derived from salicylaldehyde and its derivatives are a kind of versatile ligands in coordination
chemistry [1-3]. Nickel complexes with such Schiff bases have been proved to have diverse properties, such as magnetism
[4, 5], catalyst [6, 7] and biological activities [8–10]. As is well known, azide and thiocyanate are two charming ligands for
the construction of polymeric structures [11-14]. The search in the Cambridge Crystallographic Database (CSD; version 5.32
with addenda up to February 2012) [15] has revealed that no complexes derived from 2-[(2-isopropylamino-
1 2
ethylimino)methyl]-6-methylphenol (HL ; Scheme 1) and 2-[(2-dimethlaminoethylimino)methyl]-6-methylphenol (HL ;
Scheme 1) have been reported, and even very few complexes have been reported based on the Schiff bases derived from 3-
1
methylsalicylaldehyde. In this paper, a new azido-coordinated nickel(II) complex [NiL (N )] (1) and a new thiocyanato-
3
2
coordinated nickel(II) complex [NiL (NCS)] (2) were prepared and characterized.
1
2
School of Life Sciences, Shandong University of Technology, ZiBo, P. R. China. Department of Chemistry and
Chemical Engineering, Liaoning Normal University, Dalian, P. R. China; hailiang_zhu@163.com (Hai-Liang Zhu);
youzhonglu@yahoo.com.cn (Zhong-Lu You). The text was submitted by the authors in English. Zhurnal Strukturnoi Khimii,
Vol. 54, No. 5, pp. 888-892, September-October, 2013. Original article submitted May 21, 2012.
926
0022-4766/13/5405-0926

1
Scheme 1. The Schiff base HL and HL
2
EXPERIMENTAL
Materials and measurements. Starting materials, reagents, and solvents with analytical grade were purchased from
commercial suppliers and used without further purification. Elemental analyses were performed on a Perkin-Elmer 240C
–1
elemental analyzer. The IR spectra were recorded on a Jasco FT/IR-4000 spectrometer as KBr pellets in the 4000-200 cm
region. Single crystal structural X-ray diffraction was carried out on a Bruker X8 PROTEUM diffractometer.
1
Synthesis of HL . To the methanolic solution (20 ml) of 3-methylsalicylaldehyde (1.0 mmol, 0.14 g) was added a
methanolic solution (20 ml) of N-isopropylethane-1,2-diamine (1.0 mmol, 0.10 g) with stirring. The mixture was stirred for
30 min at room temperature to give a yellow solution. The solvent was evaporated to give a yellow gummy product of the Schiff
–1
base. Characteristic IR data: 1639 cm . Anal. Calc. for C H N O: C, 70.9; H, 9.2; N, 12.7. Found: C, 70.7; H, 9.2; N, 12.8%.
13 20
2
2
Synthesis of HL . HL was synthesized by the similar method as that described for HL , with N-isopropylethane-
2
1
–1
1,2-diamine replaced by N,N-dimethylethane-1,2-diamine (1.0 mmol, 0.09 g). Characteristic IR data: 1638 cm . Anal. Calc.
for C H N O: C, 69.9; H, 8.8; N, 13.6. Found: C, 69.6; H, 8.9; N, 7.8%.
12 18 2
1 1
Synthesis of the complexes. [NiL (N )] (1): To the methanolic solution (5 ml) of HL (0.1 mmol, 0.022 g) was
3
added a methanolic solution (5 ml) of Ni(CH COO) ⋅4H O (0.1 mmol, 0.025 g) and an aqueous solution (1 ml) of sodium
3 2 2
azide (0.1 mmol, 0.007 g) with stirring. The mixture was stirred for 30 min at room temperature and filtered. Red block-
shaped crystals of 1, suitable for the X-ray crystal structural determination, formed from the filtrate after a few days. The
–1
crystals were isolated by filtration, washed three times with methanol and dried in air. Yield 63%. Characteristic IR data (cm ):
3208 (sh), 2050 (vs), 1623 (s). Anal. Calc. for C H N NiO: C, 48.8; H, 6.0; N, 21.9. Found: C, 48.7; H, 5.9; N, 21.7%.
13 19 5
2
[NiL (NCS)] (2): Complex 2 was synthesized by the similar method as that described for 1, with sodium azide
1 2
replaced by ammonium thiocyanate (0.1 mmol, 0.008 g), and with HL replaced by HL (0.1 mmol, 0.021 g). Red small
–1
block-shaped single crystals of 2 formed. Yield 72%. Characteristic IR data (cm ): 2107 (vs), 1623 (s). Anal. Calc. for
C H N NiOS: C, 48.5; H, 5.3; N, 13.0. Found: C, 48.3; H, 5.4; N, 13.1%.
13 17 3
X-ray crystallography. Diffraction intensities for the complexes were collected at 298(2) K using a Bruker X8
PROTEUM diffractometer with MoK radiation (λ = 0.71073 Å). The collected data were reduced with the SAINT program
α
[16], and multi-scan absorption correction was performed using the SADABS program [17]. The structures were solved by
2
direct methods. The complexes were refined against F by full-matrix least-squares method using the SHELXTL package
[18]. All of the non-hydrogen atoms were refined anisotropically. The amino H atom in 1 was located from a differrence
Fourier map and refined isotropically, with the N–H distance restrained to 0.90(1) Å. The remaining hydrogen atoms were
placed in calculated positions and constrained to ride on their parent atoms. The crystallographic data for the complexes are
summarized in Table 1. Selected bond lengths and angles are given in Table 2.
RESULTS AND DISCUSSION
Structure description of the complexes. Single crystal X-ray diffraction shows that the complexes crystallize as
similar azido- or thiocyanato-coordinated mononuclear structures (Fig. 1 for 1, Fig. 2 for 2). The Ni atom in each of the
complexes is in a square planar coordination environment and is four-coordinated by one phenolate O and two N atoms of the
Schiff base ligand and by one N atom of a pseudohalide ligand (azide for 1 and thiocyanate for 2). A slight distortion of
927

TABLE 1. Crystallographic and Experimental Data for 1 and 2
Complex
Formula
1
2
C H N NiO
13 19 5
C H N NiOS
13 17 3
Mr
320.0
322.1
298(2)
T, K
298(2)
Crystal shape/color
Crystal size, mm
Crystal system
Space group
a, b, c, Å
Block/red
Block/red
0.23×0.22×0.20
0.10×0.07×0.06
Monoclinic
Triclinic
P-1
P2 /n
1
8.812(2), 9.433(3), 9.488(2)
7.4497(4), 6.1933(3), 31.5126(18)
81.933(2), 69.925(2), 84.591(2)
90, 92.484(2), 90
1452.57(13)
4
α, β, γ, deg
3
V, Å
732.5(3)
2
Z
–3
1.451
1.327
336
1.473
D , g⋅cm
c
–1
1.474
μ(MoK ), mm
α
F(000)
Independent/Observed reflections
(I ≥ 2σ(I ))
672
2666/2445
2494/2410
Min. and max. transmission
Parameters
0.750 and 0.777
187
0.867 and 0.917
175
Restraints
1
0
2
GOOF on F
1.057
1.237
a
0.0291, 0.0734
0.0324, 0.0762
0.0307, 0.0668
0.0323, 0.0675
R , wR [I ≥ 2σ(I )]
1 2
a
R , wR (all data)
1 2
2
R = F – F /F , wR = [∑w(F –
0
2
2 1/2
)/∑w(F ) ] .
0
a
2
F
1
0
c
0
2
c
TABLE 2. Selected Bond Lengths (Å) and Angles (deg) for 1 and 2
1
2
Ni1–O1
Ni1–N2
Ni1–N1
Ni1–N3
1.833(2)
1.919(2)
1.843(2)
1.899(2)
O1–Ni1–N1
O1–Ni1–N3
N1–Ni1–N3
O1–Ni1–N2
N1–Ni1–N2
N3–Ni1–N2
95.0(1)
90.2(1)
174.8(1)
178.0(1)
86.6(1)
88.1(1)
Ni1–O1
Ni1–N2
Ni1–N1
Ni1–N3
1.833(2)
1.946(2)
1.844(2)
1.880(2)
O1–Ni1–N1
O1–Ni1–N3
N1–Ni1–N3
O1–Ni1–N2
N1–Ni1–N2
N3–Ni1–N2
94.4(1)
88.4(1)
173.8(1)
179.2(1)
86.2(1)
91.0(1)
the square planar coordination is revealed by the bond angles. The perpendicular coordinate bond angles range from 86.6(1)°
to 95.0(1)° for 1, and from 86.2(1)° to 94.4(1)° for 2. The trans bond angles are 174.8(1)° and 178.0(1)° for 1, and 173.8(1)°
and 179.2(1)° for 2. The deviation of Ni atoms from the best fit square planes are 0.005(2) Å for 1 and 0.050(2) Å for 2. The
Ni–O and Ni–N bond lengths in both complexes are comparable to each other, and are also comparable to those observed in
other Schiff base nickel(II) complexes [19, 20]. The azide and thiocyanate bridging groups are nearly linear and show bent
coordination mode with the Ni atoms [for 1: N3–N4–N5/Ni1–N3–N4 = 176.5(2)/122.1(2)°; for 2: N3–C13–S1/Ni1–N3–
C13 = 179.1(2)/162.4(2)°].
In the crystal structure of 1, the adjacent two complex molecules are linked through two intermolecular N–H⋯N
hydrogen bonds, to form a dimer (Fig. 3). In the crystal structure of 2, the complex molecules are stacked along the a axis
with no obvious short contacts (Fig. 4).
928

Fig. 2. A perspective view of the molecular structure of
2 with the atom labeling scheme. The thermal elipsoids
are drawn at the 30% probability level.
Fig. 1. A perspective view of the molecular structure of 1
with the atom labeling scheme. The thermal ellipsoids are
drawn at the 30% probability level.
Fig. 3. Packing structure of 1.
Fig. 4. Packing structure of 2.
929

–1
IR spectra. In the IR spectra of the complexes, the strong absorption bands at 1623 cm can be assigned to the
azomethine stretching frequencies of the Schiff base ligands, whereas for the free Schiff base the corresponding band is observed
–1
at about 1638 cm . The shift of these bands toward lower frequencies on complexation suggests the coordination to Ni atoms
–1
through the imine N atoms. The ν(C–O) mode is present as middle bands at about 1230 cm for the complexes. The intense
–1 –1
band at 2050 cm for 1 and 2107 cm for 2 are assigned to the stretching vibration of the azide ligand in 1 and the thiocyanate
–1
ligand in 2 respectively. The weak bands indicative of the Ni–O and Ni–N bonds are located in the region 550-350 cm .
CCDC 879634 (1) and 879635 (2) contain the supplementary crystallographic data for this paper. These data can be
obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
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