Bis[2-hydr-oxy-N′-(3-phenyl-prop-2-enyl-idene)benzohydrazidato- κ2 N′,O]bis-(methanol-κO)nickel(II) and bis-[2-hydr-oxy-N′-(3-phenyl-prop-2-enyl-idene)benzohydrazidato- κ2 N′,O]bis(pyridine-κN)nickel(II)

Article abstract of DOI:10.1107/S0108270108006240

In the two title complexes of cinnamaldehyde salicyloylhydra-zone [or 2-hydr-oxy-N′-(3-phenyl-prop-2-enyl-idene)-benzo-hy-dra-zide], [Ni(C16H13N2O2)2(CH4O)2], (I), and [Ni(C16H13N2O2)2(C5H5N)2], (II), the Ni ^II atoms lie on crystallographic inversion centres and have distorted octa-hedral geometries. The equatorial plane is defined by two carbonyl O atoms and two hydrazine N atoms of two bidentate trans-oriented salicyloylhydrazone ligands. The axial positions are occupied by two O atoms from two coordinated methanol mol-ecules in (I) and by two N atoms from two coordinated pyridine mol-ecules in (II). There is an extended chain structure in (I) resulting from inter-molecular O - H...O hydrogen bonds between coordinated methanol mol-ecules and phenol O atoms, while (II) comprises discrete mol-ecules. Complex (I) also exhibits weak π-π stacking inter-actions, and intra-molecular O - H...N hydrogen bonds are present in both (I) and (II). The salicyloylhydrazone ligands in (I) and (II) are coordinated to the metal atom through the carbohydrazide O and N² atoms, not via the phenol O atom. We have established a link between the reagents used and the nuclearity of the complex formed: the ligand produced by condensation between salicylhydrazide and an aldehyde leads to mononuclear complexes, while replacing the aldehyde in the reaction by a ketone leads to multinuclear complexes.

Full text of DOI:10.1107/S0108270108006240

metal-organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
al., 2006), although many hydrazone complexes have been
synthesized and characterized. We present here the syntheses
and structural characterization of the title nickel(II)
complexes, [NiL2(CH3OH)2], (I), and [NiL2(C5H5N)2], (II),
where L is monoanionic cinnamaldehyde salicyloylhydrazone
or 2-hydroxy-N0-(3-phenylprop-2-enylidene)benzohydrazid-
ate. To the best of our knowledge, the title complexes repre-
sent the first examples of structurally characterized
cinnamaldehyde salicyloylhydrazone complexes.
ISSN 0108-2701
Bis[2-hydroxy-N0-(3-phenylprop-2-
enylidene)benzohydrazidato-j2N0,O]-
bis(methanol-jO)nickel(II) and
bis[2-hydroxy-N0-(3-phenylprop-2-
enylidene)benzohydrazidato-j2N0,O]-
bis(pyridine-jN)nickel(II)
Mei-Xiang Xuea,b and Shi-Xiong Liua*
aDepartment of Chemistry, Fuzhou University, Fuzhou, Fujian 350002, People’s
Republic of China, and bDepartment of Environment and Life Sciences, Putian
University, Putian, Fujian 351100, People’s Republic of China
Correspondence e-mail: shixiongliu@yahoo.com
As shown in Fig. 1, compound (I) contains a distorted
octahedrally coordinated NiII ion located on a crystallographic
inversion centre, with two L ligands acting in a bidentate
manner to form five-membered chelate rings. Two methanol
molecules coordinate axially via their O atoms. Atoms O2,
O2i, N2 and N2i [symmetry code: (i) 1 ꢁ x, ꢁy, 1 ꢁ z] of the
two hydrazone ligands form the equatorial plane, while the
two O atoms of the methanol molecules (O3 and O3i) occupy
the two axial positions. The Ni1—N2(hydrazine) bond
Received 29 January 2008
Accepted 6 March 2008
Online 9 April 2008
In the two title complexes of cinnamaldehyde salicyloylhydra-
zone [or 2-hydroxy-N0-(3-phenylprop-2-enylidene)benzohy-
drazide], [Ni(C16H13N2O2)2(CH4O)2], (I), and [Ni(C16H13-
N2O2)2(C5H5N)2], (II), the NiII atoms lie on crystallographic
inversion centres and have distorted octahedral geometries.
The equatorial plane is defined by two carbonyl O atoms and
two hydrazine N atoms of two bidentate trans-oriented
salicyloylhydrazone ligands. The axial positions are occupied
by two O atoms from two coordinated methanol molecules in
(I) and by two N atoms from two coordinated pyridine
molecules in (II). There is an extended chain structure in (I)
resulting from intermolecular O—Hꢀ ꢀ ꢀO hydrogen bonds
between coordinated methanol molecules and phenol O
atoms, while (II) comprises discrete molecules. Complex (I)
also exhibits weak ꢀ–ꢀ stacking interactions, and intra-
molecular O—Hꢀ ꢀ ꢀN hydrogen bonds are present in both
(I) and (II). The salicyloylhydrazone ligands in (I) and (II) are
coordinated to the metal atom through the carbohydrazide O
and N2 atoms, not via the phenol O atom. We have established
a link between the reagents used and the nuclearity of the
complex formed: the ligand produced by condensation
between salicylhydrazide and an aldehyde leads to mono-
nuclear complexes, while replacing the aldehyde in the
reaction by a ketone leads to multinuclear complexes.
˚
distance of 2.0845 (15) A in (I) is longer than the corre-
˚
sponding values of 1.988 (2), 1.995 (2) and 1.983 (2) A in
similar complexes (Table 1). The Ni1—O3(methanol) bond
˚
length of 2.0970 (14) A in (I) falls within the range 2.0661 (7)–
˚
2.148 (3) A found for octahedral nickel complexes containing
methanol in axial positions (Table 2).
Comment
The design and construction of hydrazone complexes are of
great interest due to their intriguing structural topologies and
potential applications (Sreekanth et al., 2004; Bai et al., 2006).
To date, only a few structures of cinnamaldehyde hydrazone
complexes have been reported (Son et al., 2002; Chumakov et
Figure 1
A view of compound (I), showing the atomic numbering scheme.
Displacement ellipsoids are drawn at the 30% probability level. Dashed
lines indicate hydrogen bonding. H atoms not involved in the hydrogen
bonding have been omitted for clarity. [Symmetry code: (i) 1 ꢁ x, ꢁy,
1 ꢁ z.]
m190 # 2008 International Union of Crystallography
doi:10.1107/S0108270108006240
Acta Cryst. (2008). C64, m190–m193

metal-organic compounds
The NiII centre in complex (II) displays a slightly distorted
octahedral coordination and lies on an inversion centre. The
NiII centre is coordinated by two O atoms [O2 and O2i;
symmetry code: (i) ꢁx, 1 ꢁy, 1 ꢁz] and two N atoms (N2 and
N2i) of two L ligands, and by two N atoms (N3 and N3i ) of two
coordinated pyridine molecules (see Fig. 2). In the equatorial
˚
plane, the Ni1—N2(hydrazine) bond distances of 2.082 (2) A
˚
and Ni1—O2(carboxyl) bond distances of 2.0182 (15) A are
similar to the corresponding values in (I). The Ni1—
˚
N3(pyridine) bond length of 2.1487 (19) A lies within the
˚
range 2.140 (2)—2.165 (2) A found for related nickel
complexes (Table 3).
The dihedral angles between the two benzene rings (C1–C6
and C11–C16) of the L ligand in (I) and (II) are 8.1 (1) and
18.8 (1)ꢂ, respectively. These values indicate slightly different
degrees of coplanarity for the L ligands in the two complexes.
Adjacent complex molecules in (I) are linked by two
intermolecular methanol–phenol O—Hꢀ ꢀ ꢀOii hydrogen bonds
[symmetry code: (ii) x, y ꢁ 1, z] to form an extended one-
dimensional chain along the b axis (see Table 4 and Fig. 3).
However, there is no comparable intermolecular hydrogen
bonding in (II) and this complex exists as discrete molecules.
There are intramolecular phenol–hydrazine O—Hꢀ ꢀ ꢀN
hydrogen bonds in (I) and (II), forming a six-membered ring
(H1/O1/C1/C2/C7/N1) (Tables 4 and 5).
Figure 2
A view of compound (II), showing the atomic numbering scheme.
Displacement ellipsoids are drawn at the 30% probability level. Dashed
lines indicate hydrogen bonding. H atoms not involved in the hydrogen
bonding have been omitted for clarity. [Symmetry code: (i) ꢁx, 1 ꢁ y,
1 ꢁ z.]
The structure of (I) also exhibits weak ꢀ–ꢀ stacking inter-
actions between the C9 C10 double bond and the phenol
ring (C1–C6) in adjacent molecules (Fig. 3). The distance
˚
between their centroids is 3.467 (1) A.
Figure 3
A packing diagram for (I), with hydrogen bonds shown as dashed lines
and ꢀ–ꢀ stacking shown as double-dashed lines. H atoms not involved in
hydrogen bonding have been omitted.
metal and this type of hydrazone are usually linear multi-
nuclear or cyclic multinuclear complexes (Liu et al., 2001; John
et al., 2005; Moon et al., 2006) (see bottom of second scheme).
Important structural conclusions can be drawn from the
synthetic reactions and structural characterization of known
salicyloylhydrazone complexes and the salicyloylhydrazone
complexes synthesized by our group. Firstly, the salicyloyl-
hydrazone product of the condensation between salicyl-
hydrazide and an aldehyde coordinates to a metal atom
through its carboxyl O and hydrazine N atoms, not via its
phenol O atom. Therefore, the salicyloylhydrazone complexes
formed between a metal and this type of hydrazone are usually
mononuclear (Bonardi et al., 1991; Bermejo et al., 2000; Dang
et al., 2006) (see top of second scheme). Secondly, when a
salicyloylhydrazone is synthesized by condensation between
salicylhydrazide and a ketone, the salicyloylhydrazone is
coordinated through its carboxyl O, hydrazine N and phenol O
atom. Therefore, this type of hydrazone ligand is trianionic,
and the salicyloylhydrazone complexes formed between a
Experimental
The ligand HL was prepared by the reaction of salicylhydrazide and
cinnamaldehyde in a 1:1 molar ratio under reflux in ethanol for 2 h.
The yellow product obtained on cooling was washed first with
anhydrous ethanol and then with ethoxyethane. For the preparation
of (I), HL (0.1 mmol, 27 mg) and NiCl2ꢀ6H2O (0.1 mmol, 24 mg) were
dissolved in a mixture of CH3OH (8 ml) and CH2Cl2 (8 ml). The
mixed solution was stirred for 1 h and filtered. Yellow block-like
crystals of complex (I) were obtained after 4 d. For the preparation of
(II), HL (0.1 mmol, 27 mg) and NiCl2ꢀ6H2O (0.1 mmol, 24 mg) were
dissolved in a mixture of CH3OH (8 ml) and CH2Cl2 (8 ml). After
stirring for 5 min, one drop of pyridine was added to the mixed
solution, which was then stirred for another 1 h and filtered. Yellow
prismatic crystals of complex (II) were formed after 3 d. The band at
ꢃ
Acta Cryst. (2008). C64, m190–m193
Xue and Liu
[Ni(C16H13N2O2)2(CH4O)2] and [Ni(C16H13N2O2)2(C5H5N)2] m191

metal-organic compounds
3255 cmꢁ1 in the IR spectrum of the free cinnamaldehyde salicy-
Table 1
Comparative Ni—N(hydrazine) bond lengths (A) in nickel complexes.
˚
´
loylhydrazone ligand was assigned to ꢁ(NH) (Casabo et al., 1989).
This absorption of ꢁ(NH) is absent in the IR spectra of the two title
nickel complexes, suggesting that the diazine N atom in the two
complexes is coordinated to an NiII centre and that the hydrazone
ligand is monoanionic. The bands at 3051 cmꢁ1 in (I) and 3055 cmꢁ1
in (II) are due to ꢁ(OH) of the phenol (Ding et al., 2006). Two bands
at 1521 and 1563 cmꢁ1 in the spectrum of (II) are assigned to
ꢁ[C N—N C(Oꢁ)] of the hydrazone and the coordinated pyridine
N atom (Hu et al., 2006). The thermogravimetric and differential
thermal analysis curves of complex (II) show that the decomposition
of the mixed-ligand complex occurs in two regions. Loss of two
pyridine molecules takes place in the first region between 436 and
531 K with a mass loss of 21.96% (calculated 21.14%). The second
stage between 556 and 773 K corresponds to decomposition of the
ligands with a mass loss of 68.43% (calculated 70.90%). The complex
finally degraded completely to NiO with a mass of 9.01% (calculated
9.99%).
Complex
Ni—N(hydrazine)
(I)a
(II)a
2.0845 (15)
2.082 (2)
1.988 (2)
1.995 (2)
b
Ni(C12H14N3O3)(C2H3O2)(C5H5N)2
[Ni(C5H5N)3(C14H10N2O3)]ꢀ-
1.5C5H5Nc
d
Ni(C14H12N3O2)2
1.983 (2)
References: (a) this work; (b) Gao et al. (2005); (c) Hu et al. (2005); (d) Dang et al.
(2006).
Table 2
Comparative Ni—O(methanol) bond lengths (A) in nickel complexes.
˚
Complex
Ni—O(methanol)
(I)a
2.0970 (14)
2.0661 (7)
2.112 (2)
2.148 (3)
[Ni(C3H4NO3)2(CH3OH)2]ꢀ2CH3OHe
f
Ni(C14H9N2O2)2(CH3OH)2
Ni(C24H18N4O3)(C10H8N2)(CH3OH)g
Compound (I)
References: (a) this work; (e) Lampeka et al. (1994); (f) Angulo-Cornejo et al. (2000); (g)
Hu et al. (2006).
Crystal data
3
˚
[Ni(C16H13N2O2)2(CH4O)2]
Mr = 653.36
Orthorhombic, Pbca
V = 3207.2 (17) A
Z = 4
Table 3
Comparative Ni—N(pyridine) bond lengths (A) in nickel complexes.
˚
Mo Kꢂ radiation
ꢃ = 0.66 mmꢁ1
T = 293 (2) K
˚
a = 17.536 (5) A
Complex
Ni—N(pyridine)
˚
b = 8.016 (2) A
˚
c = 22.814 (8) A
0.31 ꢄ 0.25 ꢄ 0.20 mm
(II)a
Ni(C12H14N3O3)(C2H3O2)(C5H5N)2
Ni3(C11H11N2O3)2(C5H5N)4
i
Ni(C7H7N4O3)2(C5H5N)2
2.1487 (19)
b
2.140 (2), 2.154 (2)
2.149 (3)
2.1652 (18)
h
Data collection
Rigaku R-AXIS RAPID Imaging
Plate diffractometer
Absorption correction: multi-scan
(TEXRAY; Molecular Structure
Corporation, 1999)
27936 measured reflections
3677 independent reflections
2696 reflections with I > 2ꢄ(I)
Rint = 0.046
References: (a) this work; (b) Gao et al. (2005); (h) Yang et al. (2003); (i) Ho¨rner et al.
(2002).
Table 4
Hydrogen-bond geometry (A, ) for (I).
Tmin = 0.721, Tmax = 0.906
ꢂ
˚
Refinement
D—Hꢀ ꢀ ꢀA
D—H
Hꢀ ꢀ ꢀA
Dꢀ ꢀ ꢀA
D—Hꢀ ꢀ ꢀA
R[F2 > 2ꢄ(F2)] = 0.035
wR(F2) = 0.102
S = 1.06
206 parameters
H-atom parameteꢁrs3 constrained
O1—H1ꢀ ꢀ ꢀN1
0.95
0.95
1.61
1.73
2.496 (2)
2.657 (2)
154
165
O3—H18ꢀ ꢀ ꢀO1i
˚
Áꢅmax = 0.25 e A
ꢁ3
˚
3677 reflections
Áꢅmin = ꢁ0.42 e A
Symmetry code: (i) x; y ꢁ 1; z.
Compound (II)
Table 5
Hydrogen-bond geometry (A, ) for (II).
ꢂ
˚
Crystal data
[Ni(C16H13N2O2)2(C5H5N)2]
Mr = 747.48
Triclinic, P1
ꢇ = 79.00 (3)ꢂ
V = 896.6 (10) A
Z = 1
Mo Kꢂ radiation
ꢃ = 0.59 mmꢁ1
T = 293 (2) K
D—Hꢀ ꢀ ꢀA
D—H
Hꢀ ꢀ ꢀA
Dꢀ ꢀ ꢀA
D—Hꢀ ꢀ ꢀA
3
˚
O1—H1ꢀ ꢀ ꢀN1
0.97
1.71
2.573 (3)
146
˚
a = 7.699 (6) A
˚
b = 9.814 (5) A
˚
c = 12.412 (7) A
ꢂ = 78.02 (2)ꢂ
ꢆ = 82.59 (3)ꢂ
0.20 ꢄ 0.20 ꢄ 0.11 mm
The H atom of the phenol OH group in (I) and (II) and the H atom
of the methanol OH group in (I) were located in difference Fourier
maps and then allowed to ride on their parent O atoms, with Ueq(H) =
˚
1.5Ueq(O) and an O—H distance between 0.948 and 0.975 A. The
other H atoms in (I) and (II) were placed in idealized positions and
˚
treated as riding, with C—H = 0.93 A and Uiso(H) = 1.2Ueq(C) for
˚
aromatic, and C—H = 0.96 A and Uiso(H) = 1.5Ueq(C) for methyl
groups.
Data collection
Rigaku R-AXIS RAPID Imaging
Plate diffractometer
8839 measured reflections
4060 independent reflections
3177 reflections with I > 2ꢄ(I)
Rint = 0.041
Refinement
For both compounds, data collection: TEXRAY (Molecular
Structure Corporation, 1999); cell refinement: TEXRAY; data
reduction: TEXSAN (Molecular Structure Corporation, 1999);
program(s) used to solve structure: SHELXS97 (Sheldrick, 2008);
R[F2 > 2ꢄ(F2)] = 0.042
wR(F2) = 0.100
S = 1.00
241 parameters
H-atom parameteꢁrs3 constrained
˚
Áꢅmax = 0.55 e A
ꢁ3
˚
4060 reflections
Áꢅmin = ꢁ0.37 e A
ꢃ
m192 Xue and Liu [Ni(C16H13N2O2)2(CH4O)2] and [Ni(C16H13N2O2)2(C5H5N)2]
Acta Cryst. (2008). C64, m190–m193

metal-organic compounds
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molecular graphics: ORTEX (McArdle, 1995); software used to
prepare material for publication: SHELXL97.
The authors are grateful for financial support from the
National Natural Science Foundation of China (grant Nos.
20431010 and 20171012).
¨
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ꢃ
Acta Cryst. (2008). C64, m190–m193
Xue and Liu
[Ni(C16H13N2O2)2(CH4O)2] and [Ni(C16H13N2O2)2(C5H5N)2] m193