Synthesis, characterization, molecular and supramolecular structures of nickel(II) complexes derived from α-diketone and α-ketoaldehyde bisaroylhydrazones

Article abstract of DOI:10.1016/j.poly.2009.04.007

A new series of nickel(II) complexes derived from symmetrical diacetyl bisaroylhydrazones [Ni(L¹-R)] and unsymmetric phenylglyoxal bisaroylhydrazones [Ni(L²-R)] have been prepared and characterized. X-ray crystal and molecular struct

Full text of DOI:10.1016/j.poly.2009.04.007

Polyhedron 28 (2009) 2137–2148
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Polyhedron
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Synthesis, characterization, molecular and supramolecular structures
of nickel(II) complexes derived from
bisaroylhydrazones
a-diketone and
a
-ketoaldehyde
Nahed M.H. Salem a, Amal R. Rashad a, Laila El Sayed a, W. Haase b, Magdi F. Iskander a,
*
a Chemistry Department, Faculty of Science, Alexandria University, P.O. Box 426, Ibrahimia, Alexandria 21321, Egypt
b Institut fur Physikalische Chemie, AG Kondensierte Materie, Fachbereich Chemie, Technische Universitat Darmstadt, Petersenstrasse 20, D-64287 Darmstadt, Germany
a r t i c l e i n f o
a b s t r a c t
A new series of nickel(II) complexes derived from symmetrical diacetyl bisaroylhydrazones [Ni(L1-R)] and
unsymmetric phenylglyoxal bisaroylhydrazones [Ni(L2-R)] have been prepared and characterized. X-ray
crystal and molecular structures of [Ni(L1-H)], [Ni(L1-pCH3O)] and [Ni(L1-pNO2)] have been determined.
In these complexes, the Ni(II) is in a distorted square planar environment and the aroylhydrazone acts as
dinegative tetradentate ligand forming a 5,5,5-tricyclic chelate ring. Reaction of [Ni(L1-R)] with aqueous
ammonia afforded the paramagnetic five coordinate [Ni(L1-R)(NH3)] while [Ni(L2-R)] gave the diamag-
netic square planar [Ni(L2-R)(NH3)] complexes. Reaction of [Ni(L1-R)] complexes with imidazole gave
the corresponding paramagnetic octahedral bis(imidazole) adducts. X-ray structures of both [Ni(L1-
H)(HIm)2] and [Ni(L1-pNO2)(HIm)2] suggest a distorted octahedral structure where the bisaroylhydraz-
one occupies the basal plane while the two imidazoles occupy the axial sites. The molecular units are
associated together forming triple stranded helical chains. With imidazole the [Ni(L2-R)] series gave
the corresponding diamagnetic mono(imidazole) [Ni(L2-R)(HIm)] complexes, The X-ray structure of
{Ni(L2-pCH3)(HIm)] suggest square planar arrangement around the Ni(II) where the bisaroylhydrazone
acts as dinegative NNO tridentate ligand forming with the Ni(II) a 5,6-bicyclic chelate ring the fourth
coordination site is occupied by imidazole nitrogen.
Article history:
Received 26 February 2009
Accepted 7 April 2009
Available online 16 April 2009
Keywords:
Bisaroylhydrazones
Nickel(II)complexes
Ammonia and imidazole complexes
X-ray molecular structures
Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction
membered tricyclic chelate ring system. This mode of chelation
was confirmed by X-ray structural analysis of the Ni(II) complexes
The coordination chemistry of tridentate aroylhydrazones
derived from ortho hydroxyaldehydes and ketones [1–11], 2-N-
heterocyclic aldehydes and ketones [12–17], b-diketones [18–23]
with diacetyl bis(benzoylhydrazone) and bis(p-methoxybenzo-
ylhydrazone) [35,37]. Moreover, square planar Ni(II) complex
with diacetyl bisbenzoylhydrazone was found to act as Lewis acid
and its interaction with different types of Lewis bases has been
studied spectrophotometrically [39–42]. Only octahedral bis(pyri-
dine) adduct was isolated and partially characterized [39]. Reac-
tions with bidentate heterocyclic bases, however, proceeded with
the rupture of one of the two coordinated oxygens and eventually
gave the monobase adduct. The bis(aroylhydrazone) ligand acted
as dinegative NNO tridentat anion, forming with the central Ni(II)
a 5,5-membered bicyclic chelate ring [43]. In the present paper, we
describe the synthesis and characterization of a new series of
nickel(II) complexes derived from both symmetric diacetyl bis-
aroylhydrazones (H2L1-R) (1, R1 = R2 = CH3, R3 = C6H5, p-CH3ÁC6H4,
p-CH3OÁC6H4, p-ClÁC6H4 or p-NO2ÁC6H4) and unsymmetric phenyl-
and
a-ketomonooximes [24–28] have been extensively studied.
Besides their interesting coordination chemistry, tridentate aro-
ylhydrazones and their transition metal complexes show a wide
spectrum of biological and pharmacological activities [29–34]. Less
attention, however, was paid for a systematic study on the coordi-
nation chemistry of tetradentate bisaroylhydrazones derived from
a-ketoaldehydes and a-diketones. Some of the diacetyl bis-
aroylhydrazone nickel(II) complexes have been prepared and char-
acterized [35–38]. In these complexes the bis aroylhydrazone
ligand was found to act as a dinegative NNOO tetradentate anion
where the central Ni(II) is coordinated to two imine nitrogens
and the two deprotonated enolimide oxygens forming the 5,5,5-
glyoxal bisaroyl
–
hydrazones (H2L2-R) (1, R1 = H, R2 = C6H5,
R3 = C6H5, p-CH3ÁC6H4, p-OCH3ÁC3H4, p-ClÁC6H4, p-NO2ÁC6H4). The
X-ray crystal and molecular structure of [Ni(L1-pNO2)] has been
determined and compared with the previously reported X-ray
* Corresponding author. Tel.: +20 3 3911794; fax: +20 3 5932488.
E-mail address: m.iskander@link.net (M.F. Iskander).
0277-5387/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2009.04.007

2138
N.M.H. Salem et al. / Polyhedron 28 (2009) 2137–2148
structures of [Ni(L1-H)] and [Ni(L1-pCH3O)] [35,37]. The reactions
of both [Ni(L1-R)] and [Ni(L2-R)] series with ammonia and
imidazole have been also studied aiming to investigate the effect
of the nature of substituents on the C–C backbone of the ligands
on the reactivity of this type of nickel(II) complexes. The X-ray
structures of representative bis- and monoimidazole complexes
obtained, respectively, from the reaction of imidazole with
[Ni(L1-R)] and [Ni(L2-R)] have been determined.
2. Experimental
2.1. Materials
Diacetyl and phenylglyoxal were obtained from Aldrich and
used without further purification. Hydrazine hydrate (99%)
(BDH), imidazole and nickel acetate tetrahydrate (BDH) were also
used without further purification. Aroylhydrazines were prepared,
as previously described [27], by the hydrazinolysis of aromatic car-
boxylic methyl esters in methanol.
[Ni(L1-H)] (2, R1 = R2 = CH3, R3 = C6H5). Yield: 70%. Anal. Calc. for
C18H16N4O2Ni: C, 57.04; H, 4.25; N, 14.78. Found: C, 57.20; H,
4.27; N, 14.74%. IR (KBr) (cmÀ1): 1587 m,
m
m
(C@N–N@C); 1552 m
(N@C–C@N); 1372s, 1297s, amide III (C–N) + (C–O)].
)): 275(4.22); 324(4.19); 390(4.23)
2.2. Preparation of bisaroylhydrazones (1)
[
m
m
UV–Vis(CH2Cl2, kmax/nm (log
e
Bisaroylhydrazones were prepared as previously described by
the condensation of diacetyl or phenylglyoxal with two equimolar
amounts of aroylhydrazine in acidified ethanol [36]. The infrared,
ultraviolet-visible and 1H NMR spectral data of the prepared
bisaroylhydrazones are deposited as Supplementary data.
(L–L*); 628sh, 684(3.13); 752 (2.98) (MLCT). Magnetic moment
(
leff, lb): diamagnetic.
[Ni(L1-pCH3)] (2, R1 = R2 = CH3, R3 = p-CH3ÁC6H4). Yield: 72%. Anal.
Calc. for C20H20N4O2Ni: C, 59.01; H, 4.95; N, 13.76. Found: C, 58.82;
H, 4.99; N, 13.56%. IR (KBr) (cmÀ1): 1608s, 1587s
1552 m, (N@C–C@N); 1386s, 1293s, amide III [ (C–N) +
UV–Vis (CH2Cl2, kmax/nm (log )): 239(4.38); 282(4.20);
330(4.24), 397(4.32) (L–L*); 471(3.33) (LMCT); 623sh; 681(3.19);
m
(C@N–N@C);
(C–O)].
m
m
m
e
748(2.98) (MLCT). Magnetic moment (leff, lb): diamagnetic.
[Ni(L1-pCH3O)] (2, R1 = R2 = CH3, R3 = p-CH3OÁC6H4). Yield: 66%.
Anal. Calc. for C20H20N4O4Ni: C, 54.71; H, 4.59; N, 12.76. Found: C,
54.74; H, 4.58; N, 12.62%. IR (KBr) (cmÀ1): 1603s
m
(C@N–N@C);
(C–N) + (C–O)].
): 252(4.45); 341(4.17); 410(4.39)
(L–L*); 470sh (LMCT); 629sh, 677(3.29); 742(3.07) (MLCT). Mag-
1552 m,
m
(N@C–C@N); 1372s, 1250s, amide III [
m
m
UV–Vis (CH2Cl2, kmax/nm (log
e
netic moment (leff, lb): diamagnetic.
[(Ni(L1-pCl)] (2, R1 = R2 = CH3, R3 = p-ClÁC6H4). Yield: 68%. Anal.
Calc. for C18H14N4O2Cl2Ni: C, 48.27; H, 3.15; N, 12.51. Found: C,
48.30; H, 3.30; N, 12.30%. IR (KBr) (cmÀ1): 1582 m
m
(C@N–N@C);
(C–N) + (C–O)].
UV–Vis (CH2Cl2 (saturated solution), kmax/nm (log )): 242; 282;
328; 390 (L–L*); 468sh (LMCT); 635sh, 681; 752 (MLCT). Magnetic
1550 m,
m
(N@C–C@N); 1382s, 1291s, amide III [
m
m
e
2.3. Preparation of nickel(II) complexes
moment (leff, lb): diamagnetic.
2.3.1. Preparation of [NiL1-R] (2, R1 = R2 = CH3, R3 = C6H5, p-CH3ÁC6H4,
p-CH3OÁC6H4, p-ClÁC6H4 and p-NO2ÁC6H4) and [NiL2-R]ÁnH2O
(2, R1 = H, R2 = C6H5, R3 = p-CH3ÁC6H4, p-CH3OÁC6H4, p-ClÁC6H4
and p-NO2ÁC6H4) complexes
[Ni(L1-pNO2)] (2, R1 = R2 = CH3, R3 = p-NO2ÁC6H4). Yield: 73%. Anal.
Calc. for C18H14N6O6Ni: C, 46.09; H, 3.01; N, 17.92. Found: C, 46.21;
H, 3.14; N, 17.32%. IR (KBr) (cmÀ1): 1603s, 1587s,
m
(C@N–N@C);
(C–N) + (C–O)].
)): 320(4.19); 334sh; 395(4.27)
(L–L*), 470(3.19) (LMCT); 658(2.96); 703(2.97); 771sh (MLCT).
1555sh
m(N@C–C@N); 1343s, 1270s, amide III [
m
m
A hot solution of potassium hydroxide (0.02 mol) in ethanol
UV–Vis (CH2Cl2, kmax/nm (log
e
(15 ml) was added to
a
suspension of the appropriate
bisaroylhydrazone (1, R1 = R2 = CH3, R3 = C6H5, p-CH3ÁC6H4,
p-CH3OÁC6H4, p-ClÁC6H4 and p-NO2ÁC6H4; R1 = H, R2 = C6H5,
R3 = p-CH3ÁC6H4, p-CH3OÁC6H4, p-ClÁC6H4 and p-NO2ÁC6H4)
(0.01 mol) in ethanol (50 ml). To the resulting yellow solution,
a hot solution of nickel(II) acetate tetrahydrate (0.01 mol) in eth-
anol (25 ml) was added. The mixture was then refluxed, with
constant stirring, for 2 h. The isolated complex was then filtered
off, recrystallized from benzene and then dried under vacuum.
Single crystals of [Ni(L1-H)] and [Ni(L1-pCH3O)], suitable for
X-ray diffraction studies were selected from the recrystallised
batches, while crystals of benzene solvate [Ni(L1-pNO2)]Á
1/2C6H6 were isolated from the mother liquor after kept for
1 month.
Magnetic moment (leff, lb): diamagnetic.
[Ni(L2-H)] (2, R1 = H, R2 = C6H5, R3 = C6H5). Yield: 46%. Anal. Calc.
for C22H16N4O2Ni: C, 61.87; H, 3.78; N, 13.12. Found: C, 61.80; H,
3.86; N, 13.08%. IR (KBr) (cmÀ1): 1610 m, 1580 m,
m(C@N–N@C);
1552 m, 1530 m
m
(N@C–C@N); 1390s, 1297s, amide III [ (C–N) +
m
m
(C–O)]. UV–Vis (CH2Cl2 (saturated solution), kmax/nm (log
e
)):
*
240(4.58), 303(4.45), 385sh (L–L ); 425(3.43) (LMCT); 635 (MLCT).
Magnetic moment (leff, lb): diamagnetic.
[Ni(L2-pCH3)]ÁH2O (2, R1 = H, R2 = C6H5, R3 = p-CH3ÁC6H4). Yield:
58%. Anal. Calc. for C24H22N4O3Ni: C, 60.92; H, 4.69; N, 11.84.
Found: C, 60.47; H, 4.40; N, 12.31%. IR (KBr) (cmÀ1): 1609s,
1579s,
m
(C@N–N@C); 1553 m, 1535,
m(N@C–C@N); 1395s, 1369s,
amide III [
m
(C–N) + (C–O)]. UV–Vis (CH2Cl2 (saturated solution),
m

N.M.H. Salem et al. / Polyhedron 28 (2009) 2137–2148
2139
kmax/nm (log
(MLCT). Magnetic moment (leff
e
)): 240(4.58); 303sh (L–L*); 425(3.43) (LMCT); 638
H, 4.31; N, 15.73%. IR (KBr) (cmÀ1): 3360m, 3324m, 3255m,
(NH3); 1655, amide I
m
(N–H)
,
lb): diamagnetic.
[m
(C@O)];1635s d(N–H); 1600s, 1575s,
(C@N–N@C); 1555m, 1535m, (N@C–C@N). UV–Vis (CH2Cl2,
)): 233(4.35), 259sh, 288(4.53), 357(3.94) (L–L*);
Ni(L2-pCH3O)]ÁH2O (2, R1 = H, R2 = C6H5, R3 = p-CH3OÁC6H4). Yield:
60%. Anal. Calc. for C24H22N4O5Ni%: C, 57.06; H, 4.39; N, 11.09.
Found: C, 57.52; H, 4.40; N, 11.65%. IR (KBr) (cmÀ1): 1605s,
m
m
kmax/nm (log
e
442(3.84) (LMCT); 468 (3.83), 655(sh) (MLCT). Magnetic moment
1585s,
(C–N) +
430 (LMCT); 560(3.30); 641(3.08) (MLCT). Magnetic moment (leff
m
(C@N–N@C); 1535,
m
(N@C–C@N); 1373s, 1250s, amide III
(leff, lb): diamagnetic.
[
m
m
(C–O)]. UV–Vis (CH2Cl2, kmax/nm (log
e
)): 363sh (L–L*);
[Ni(L2-pCH3)(NH3)]Á1/2H2O (4, R1 = H, R2 = C6H5, R3 = p-CH3ÁC6H4).
,
Yield: 48%. Anal. Calc. for C24H24N5O2.5Ni%: C, 59.91; H, 5.03; N,
l
b): diamagnetic.
14.55. Found: C, 59.47; H, 4.86; N, 14.64%. IR (KBr) (cmÀ1): 3365,
[Ni(L2-pCl)]Á2H2O (2, R1 = H, R2 = C6H5, R3 = p-ClÁC6H4). Yield: 56%.
3325, 3255, 3115,
1640s, d(N–H), 1603s,
UV–Vis (CH2Cl2, kmax/nm (log
435(3.84) (LMCT); 475(3.85), 655sh (MLCT). Magnetic moment
m
(N–H) (NH3); 1655sh, amide I [
(C@N–N@C), 1555s, 1533s, (N@C–C@N).
)): 285(4.57), 360(3.97) (L–L*);
m(C@O)];
Anal. Calc. for C22H18N4O4Cl2Ni: C, 49.67; H, 3.41; N, 10.53. Found:
m
m
C, 49.14; H, 2.96; N, 10.39%. IR (KBr) (cmÀ1): 1620s, 1597s,
e
m
(C@N–N@C); 1570s, 1550s,
III [ (C–N) + (C–O)]. UV–Vis (CH2Cl2 (saturated solution), kmax/nm
(log
)): 240sh, 309sh; 409 (L–L*); 425sh (LMCT); 644 (MLCT).
Magnetic moment (leff b): diamagnetic.
m(N@C–C@N) 1383s, 1253s, amide
m
e
m
(leff, lb): diamagnetic.
[Ni(L2-pCH3O)(NH3)]Á2H2O (4, R1 = H, R2 = C6H5, R3 = p-CH3
,
l
OÁC6H4). Yield: 56%. Anal. Calc. for C24H27N5O6Ni: C, 53.36; H, 5.04;
N, 12.97. Found: C, 53.85; H, 4.89, N, 12.97%. IR (KBr) (cmÀ1):
2.3.2. Preparation of [Ni(L1-R)(NH3)] complexes
To hot suspension of diacetyl bis(aroylhydrazone)(1,
3377m, 3356m, 3321m, 3247m, 3187m,
amide I [ (C@O)]; 1640s, d(N–H); 1600s, 1570s,
1552m, 1535m, (N@C–C@N). UV–Vis (CH2Cl2, kmax / nm (log
262sh, 288 (4.56), 367 (4.07) (L – L*); 435 (3.92) (LMCT); 475
m
(N–H) (NH3); 1657m
(C@N–N@C);
)):
a
m
m
R1 = R2 = CH3, R3 = p-ClÁC6H4 and p-NO2ÁC6H4) (0.01 mol) in ethanol
(20 ml), a hot solution of nickel(II) acetate tetrahydrate (0.01 mol)
in ethanol (20 ml) was added. The resulting green mixture turned
red upon treating with aqueous ammonia (3 ml of 30% ammonia
solution). The red solution was then stirred for 1/2 h, during which
a reddish brown precipitate separated out, was filtered off and
dried in air. In the case of R3 = C6H5, p-CH3ÁC6H4 and p-CH3OÁC6H4
only the [Ni(L1-R)] complexes were isolated.
m
e
(3.92), 652 (2.08) (MLCT). Magnetic moment (leff, lb): diamagnetic.
[Ni(L2-pCl)(NH3)] (4, R1 = H, R2 = C6H5, R3 = p-ClÁC6H4). Yield: 60%.
Anal. Calc. for C22H17N5O2Cl2Ni: C, 51.51; H, 3.34; N, 13.65. Found:
C, 51.46, H, 3.35, N, 13.54%. IR (KBr) (cmÀ1): 3370m, 3311m,
3155m, 3155m,
d(N–H); 1585s,
(CH2Cl2 saturated solution, kmax/nm (log e
m
(N–H) (NH3); 1660sh, amide I [
(C@N–N@C); 1534m, (N@C–C@N). UV–Vis
)): 225, 288, 365 (L–L*),
b): diamagnetic.
m(C@O)]; 1637s,
m
m
[(Ni(L1-pCl(NH3)]. Yield: 38%. Anal. Calc. For C18H17N5O2Cl2Ni: C,
46.50; H, 3.69; N, 15.06. Found: C, 46.88; H, 3.65; N, 14.60%. IR
435 (LMCT), 470 (MLCT). Magnetic moment (leff, l
(KBr) (cmÀ1): 3320m, 3246m, 3190m,
m
(N–H) (NH3); 1640s
[Ni(L2-pNO2)(NH3)] (4, R1 = H, R2 = C6H5, R3 = p-NO2ÁC6H4). Yield:
60%. Anal. Calc. for C22H17N7O6Ni: C, 49.47; H, 3.21; N, 18.36.
Found: C, 49.45; H, 3.26; N, 18.38%. IR (KBr) (cmÀ1): 3318, 3252,
d(N–H); 1584s,
moment (leff, lb): 2.70.
m(C@N–N@C); 1550sh, m(N@C–C@N). Magnetic
[Ni(L1-pNO2(NH3)]ÁH2O. Yield: 35%. Anal. Calc. For C18H19N7O7Ni:
3186, 3108,
d(N–H); 1595s, 1570s,
Vis (CH2Cl2 saturated solution, kmax/nm (log
(LMCT); 500sh (MLCT). Magnetic moment (leff, l
m
(N–H) (NH3); 1658sh, amide I [
(C@N–N@C); 1535sh, (N@C–C@N). UV–
)): 275 (L–L*), 435
b): diamagnetic.
m(C@O)]; 1643s,
C, 42.89; H, 3.80; N, 19.45. Found: C, 42.74; H, 3.70; N, 18.85%. IR
m
m
(KBr) (cmÀ1): 3375m, 3283m, 3264m, 3237m,
m
(N–H) (NH3);
e
1642s, d(N–H), 1602,
m(C@N–N@C), 1568,
m
(N@C–C@N). Magnetic
moment (leff b): 2.64.
,
l
2.3.4. Preparation of [Ni(L1-R)(HIm)2] (5, R1 = R2 = CH3, R3 = C6H5, p-
CH3 Á C6H4, p-CH3O Á C6H4, p-Cl Á C6H4 and p-NO2 Á C6H4)
2.3.3. Preparation of [Ni(L2-R)(NH3)] (4, R1 = H, R2 = C6H5, R3 = p-
CH3ÁC6H4, p-CH3OÁC6H4, p-ClÁC6H4 and p-NO2ÁC6H4) complexes
The [Ni(L2-R)(NH3)] (4, R1 = H, R2 = C6H5, R3 = C6H5, p-CH3ÁC6H4,
Bis(imidazole) nickel(II) complexes were prepared by adding a
hot suspension of diacetyl bisaroylhydrazone (0.01 mol) in aceto-
nitrile (20 ml) to a hot solution of nickel(II) acetate tetrahydrate
(0.01 mol) in ethanol (20 ml). The resulting green complex was
then treated with a large excess of solid imidazole (0.08 mol) to
give a dark red solution. The resulted solution was filtered and then
evaporated to half its original volume. On cooling, the formed crys-
tals were filtered off and dried in air.
p-CH3OÁC6H4, p-ClÁC6H4 and
p-NO2ÁC6H4) complexes were
prepared using the same procedure described for [Ni(L1-R)(NH3)]
complexes.
[Ni(L2-H)(NH3)] (4, R1 = H, R2 = C6H5, R3 = C6H5). Yield: 41%. Anal.
Calc. for C22H19N5O2Ni: C, 59.50; H, 4.31; N, 15.77. Found: C, 59.52,

2140
N.M.H. Salem et al. / Polyhedron 28 (2009) 2137–2148
[Ni(L1-H)(HIm)2] Á H2O (5, R1 = R2 = CH3, R3 = C6H5). Yield: 58%.
1598s,
1291s, amide III [
(log
): 308(4.50), 367(sh) (L–L*); 475(3.80), 490(3.62) (LMCT);
m
(C@N–N@C); 1570s, 1552m,
m(N@C–C@N); 1366s,
Anal. Calc. for C24H26N8O3Ni: C, 54.06; H, 4.91; N, 21.01. Found:
m
(C–N) + (C–O)]. UV–Vis (DMF), kmax/nm
m
C, 54.21; H, 4.79; N, 21.25%. IR (KBr) (cmÀ1): 3135m,
e
m
m
III [
(N–H); 3049m, 2930m, 2848m [(
(C@N–N@C); 1548m, 1533, (N@C–C@N); 1343s, 1287s, amide
(C–N) + b): 3.22.
m
(N–H) +
m
(C–H)]; 1585m,
570(3.44), 625(3.58) (MLCT). Magnetic moment
(leff, lb):
m
diamagnetic.
m
m
(C–O)]. Magnetic moment (leff
,
l
[Ni(L2-pCH3)(HIm)] (6, R1 = H, R2 = C6H5, R3 = p-CH3 Á C6H4). Yield:
58%. Anal. Calc. for C27H24N6O2Ni: C, 61.98; H, 4.62; N, 16.06.
Found: C, 61.47; H, 4.65; N, 15.55%. IR (KBr) (cmÀ1): 3171s,
[Ni(L1-pCH3)(HIm)2] (5, R1 = R2 = CH3, R3 = p-CH3ÁC6H4). Yield:
55%. Anal. Calc. for C26H28N8O2Ni: C, 57.48; H, 5.20; N, 20.63.
Found: C, 57.24; H, 5.19; N, 20.32%. IR (KBr) (cmÀ1): 3127m,
m
(N–H); 3061, 2967, 2919, 2859 [
amide I, (C@O); 1608s, 1587,
(N@C–C@N); 1396s, 1291s, amide III [
(DMF), kmax/nm (log
): 305(4.48), 367(sh) (L–L*); 477(3.75),
487(3.60) (LMCT); 570(3.37), 620(3.50) (MLCT). Magnetic moment
m
(N–H) +
(C@N–N@C); 1570, 1552,
(C–N) + (C–O)]. UV–Vis
m(C–H)]; 1660s, 1628s,
m
m
(N–H); 3057m, 2951m, 2850m [(
(C@N–N@C); 1570, (N@C–C@N); 1336s, 1288s, amide III
(C–N) +
m
(N–H) +
m(C–H)]; 1601m,
m
m
m
m
m
m
[m
m
(C–O)]. Magnetic moment (leff
,
l
b): 3.30.
e
[Ni(L1-pCH3O)(HIm)2]Á1/2H2O (5, R1 = R2 = CH3, R3 = p-CH3OÁC6H4).
Yield: 55%. Anal.
Calc. for C26H29N8O4.5Ni: C, 53.36; H,
(leff, lb): diamagnetic.
4.99; N, 19.14. Found: C, 53.28; H, 4.90; N, 19.08%. IR (KBr)
(cmÀ1): 3112m,
(N–H); 3050, 2929, 2838 [( (N–H) +
(C–H)]; 1601s, 1582, (C@N–N@C); 1540s, (N@C–C@N); 1349s,
(C–N) + (C–O)]. Magnetic moment (leff b):
[Ni(L2-pCH3O)(HIm)] (6, R1 = H, R2 = C6H5, R3 = p-CH3O Á C6H4).
m
m
Yield: 64%. Anal. Calc. for C27H24N6O4Ni: C, 58.41; H, 4.36; N,
m
m
m
15.14. Found: C, 58.49; H, 4.34; N, 15.06%. IR (KBr) (cmÀ1):
1249s, amide III [
m
m
,
l
3171s,
1628s, amide I,
(N@C–C@N); 1396s, 1291s, amide III [
(DMF), kmax/nm (log
): 305(4.48), 367(sh) (L–L*); 477(3.75),
487(3.60) (LMCT); 570(3.37), 620(3.50) (MLCT). Magnetic moment
m
(N–H); 3061, 2967, 2919, 2859 [
(C@O); 1608s, 1587, (C@N–N@C); 1570, 1552,
(C–N) + (C–O)]. UV–Vis
m(N–H) + m(C–H)]; 1660s,
3.60.
m
m
[Ni(L1-pCl)(HIm)2]Á1/2H2O (5, R1 = R2 = CH3, R3 = p-Cl.C6H4). Yield:
53%. Anal. Calc. for C24H23N8O2.5Cl2Ni: C, 48.60; H, 3.91; N, 18.89.
Found: C, 48.51; H, 3.77; N, 18.98%. IR (KBr) (cmÀ1): 3138m,
m
m
m
e
m
(N–H); 3074m, 2961m, 2925, 2860 [(
m
(N–H) +
m
(C–H)]; 1580m,
(leff, lb): diamagnetic.
m(C@N–N@C); 1540, (N@C–C@N); 1363s, 1292s, amide III,
m
[Ni(L2-pCl)(HIm)] (6, R1 = H, R2 = C6H5, R3 = p-ClÁC6H4). Yield: 62%.
m
(C–N). Magnetic moment (leff
,
lb): 3.15.
Anal. Calc. for C25H18N6O2Cl2Ni: C, 53.24; H, 3.22; N, 14.90. Found:
[Ni(L1-pNO2)(HIm)2] (5, R1 = R2 = CH3, R3 = p-NO2ÁC6H4 ). Yield:
C, 52.79; H, 3.26; N, 15.40%. IR (KBr) (cmÀ1): 3133s,
2968, 2860 [ (N–H) + (C–H)]; 1660m, 1634m, amide I,
1613s, 1594s, (C@N–N@C); 1560, 1535, (N@C–C@N) 1392s,
1297s, amide III [ (C–N) + (C–O)]. UV–Vis (DMF), kmax/nm (log ):
305(4.46), 367(sh) (L–L*); 477(3.70), 481(3.69) (LMCT); 560(3.36),
m(N–H); 3077,
54%. Anal. Calc. for C24H22N10O6Ni: C, 47.63; H, 3.66; N, 23.14.
m
m
m
(C@O);
Found: C, 47.59; H, 3.64; N, 22.74%. IR (KBr) (cmÀ1): 3132m,
m
m
m(N–H); 3060m, 2950m, 2864m [(
m(C@N–N@C); 1535m, (N@C–C@N)1340s, 1286s, amide III,
m(C–N). Magnetic moment (leff b): 3.17.
m
(N–H) +
m
(C–H)]; 1600m,
m
m
e
m
,
l
610(3.47), 652(sh) (MLCT). Magnetic moment
diamagnetic.
(
leff
,
lb):
2.3.5. Preparation of [Ni(L2-R)(HIm)] (6, R1 = H, R2 = C6H5, R3 = p-
CH3ÁC6H4, p-CH3OÁC6H4, p-ClÁC6H4 and p-NO2ÁC6H5)
[Ni(L2-pNO2)(HIm)] (6, R1 = H, R2 = C6H5, R3 = p-NO2ÁC6H4): Yield:
62%. Anal. Calc. for C25H18N8O6Ni: C, 51.29; H, 3.10; N, 19.16.
Found: C, 51.35; H, 3.13; N, 19.02%. IR (KBr) (cmÀ1): 3218s,
To
a hot suspension of phenylglyoxal bisaroylhydrazone
(0.01 mol) in acetonitrile (20 ml), a hot solution of nickel(II) acetate
tetrahydrate (0.01 mol) in ethanol (20 ml) was added. The result-
ing green complex was then treated with a large excess of solid
imidazole (0.05 mol) to give a dark red solution. The resulted solu-
tion was filtered, then evaporated to half its original volume. After
cooling, the formed red crystals were filtered off.
3152m,
1650s, amide I,
(N@C–C@N); 1345s, 1287s, amide III,
UV–Vis (DMF), kmax/nm (log
): 377sh (L–L*); 480(3.95) LMCT,
m
(N–H); 3080, 3050, 2972, 2934
(C@O); 1599m, (C@N–N@C); 1550, 1526,
(C–N) + (C–O)].
[m(N–H) + m(C–H)];
m
m
m
[
m
m
e
495(3.82), 648(3.18) (MLCT). Magnetic moment
(leff, lb):
diamagnetic.
2.4. Physical measurements
The infrared spectra were recorded on a Perkin–Elmer 1430
Data system and/or a Perkin–Elmer (FT-IR) Paragon 1000 PC spec-
trophotometer. Solid samples were examined as KBr discs. The
ultraviolet and visible absorption spectra were recorded on
V-530 UV–Vis. recording spectrophotometer, Jasco, using 10 mm
quartz cells and/or a double beam ratio recording Lambada 4B Per-
kin–Elmer spectrophotometers. 1H NMR spectra were recorded on
Brucker WM 300 using tetramethylsilane (TMS) as an internal
standard. Magnetic susceptibilities of powdered dried samples
were recorded on a Faraday-type magnetometer using a sensitive
computer controlled D-200 Cahn RG microbalance. The magnetic
field applied was ꢀ1.5 T [44]. Experimental susceptibility data
were corrected for the underlying diamagnetism using Pascal’s
constants.
X-ray diffraction data were collected on CrysAlis CCD,
Oxford Diffraction limited, version 1.70.14 (2002), using graphite
monochromated Mo K
a radiation (k = 0.71013 Å). The structures
[Ni(L2-H)(Him)] (6, R1 = H, R2 = C6H5, R3 = C6H5). Yield: 60%. Anal.
were solved by direct method with SHELXS-97 [45]; refinement was
done by full-matrix least squares on F2 using the SHEXL-97 [45].
Drawings of the molecules were produced with ORTEP 3 [46] or
PLATON [47].
Calc. for C25H20N6O2Ni: C, 60.64; H, 4.07; N, 16.97. Found: C, 60.52;
H, 4.05; N, 16.93%. IR (KBr) (cmÀ1): 3131s,
m
(N–H); 3050, 2969,
2932 [
m(N–H) +
m
(C–H)]; 1660sh, 1643, amide I, (C@O); 1616s,
m

N.M.H. Salem et al. / Polyhedron 28 (2009) 2137–2148
2141
be tentatively assigned for these solid complexes, where the four
donor atoms of the dinegative bishydrazone ligand are coordinated
to the Ni(II) forming the equatorial plane while ammonia occupies
the fifth coordination site. It seems that these complexes are stable
only in the solid state. However in solution, complete deammina-
tion occurs and the solution electronic spectra of both
[Ni(L1-pCl)ÁNH3] and [Ni(L1-pNO2)ÁNH3] in dichloromethane are
quite similar to those recorded for the parent square planar
complexes.
3. Results and discussion
3.1. Synthesis and characterization
In ethanol, the reaction of both symmetrical diacetyl bis-
aroylhydrazones, (H2L1-R), and unsymmetrical phenylglyoxal
bisaroylhydrazone (H2L2-R) with nickel(II) acetate tetrahydrate in
the presence of KOH, respectively afforded the corresponding
neutral nickel(II) chelates [Ni(L1-R)] (2, R1 = R2 = CH3 and
R3 = C6H5, p-CH3ÁC6H4, p-CH3OÁC6H4, p-ClÁC6H4, and p-NO2ÁC6H4)
and [Ni(L2-R)]ÁnH2O (2, R1 = H, R2 = C6H5, R3 = p-CH3ÁC6H4,
p-CH3OÁC6H4 or p-ClÁC6H4). The IR spectra of these nickel(II)
complexes lack absorption bands which could be attributed to
The reaction of unsymmetric bisaroylhydrazones H2L2-R with
Ni(CH3COO)2Á4H2O in the presence of aqueous ammonia gave the
corresponding monoammine complexes of the general formula
[Ni(L2-R)ÁNH3]ÁnH2O. Different from [Ni(L1-pCl)ÁNH3] and
[Ni(L1-pNO2)ÁNH3] which are paramagnetic, the prepared nickel(II)
complexes [Ni(L2-R)ÁNH3]ÁnH2O are diamagnetic, suggesting
square planar arrangement around the Ni(II) ion. The electronic
absorption spectra of these complexes in dichloromethane display
three absorptions due to L–L* transitions at ca 220, 270 and
360 nm, besides a strong LMCT absorption band at ca 445 nm.
The spectra also display three MLCT absorption bands within the
range 470–660 nm, confirming a square planar structure. In these
square planar nickel(II) complexes, the bisaroylhydrazone must
act as a dinegative tridentate anion while the NH3 occupies the
fourth coordination site. Thus two coordination modes 3 or 4 can
be proposed for these complexes. The presence of a very intense
m
(N–H), amide(I)
a very intense band at ca. 1625–1580 cmÀ1 due to
The (N@C–C@N) of the diimine residue which appears at ca
m
(C@O) and amide (II) bands, but exhibit instead
m
(C@N–N@C).
m
1610–1570 cmÀ1 in the spectra of metal free ligands are shifted
to lower frequencies, 1550–1535 cmÀ1, in the corresponding Ni(II)
complexes. These spectral data suggest the deprotonation of the
two amide residues of the bisaroylhydrazone ligand and the bis-
aroylhydrazones in these nickel(II) complexes act as dinegative
N2O2 tetradentate ligands [35–37]. At room temperature (298 K),
the prepared monoligand nickel(II) complexes [Ni(L1-R)] and
[Ni(L2-R)]ÁnH2O were found to be diamagnetic, indicating square
planar arrangement with 1A1g ground state. The solution electronic
absorption spectra (UV–Vis) of these complexes in dichlorometh-
ane are in agreement with this assignment [48]. The absorption
bands at ca 239–282 and 321–397 nm can be related to the differ-
ent L–L* transitions of the highly conjugated dinegative ligand
anion. Similar to other square planar nickel(II) complexes [48],
the band located around 410– 71 nm is most probably due to a
LMCT transition(s), while the three absorption bands in the regions
amide I [m
(C@O)] band at 1650–1666 cmÀ1 in the IR spectra of
these complexes suggest the deprotonation of the hydrazone
N–H proton and structure 4 can be tentatively assigned for these
complexes where the bisaroylhydrazone acts as dinegative NNO
tridentate anion and is coordinated to the Ni(II) via deprotonated
enolimine oxygen, imine nitrogen and deprotonated hydrazone
nitrogen forming a 5,6-membered bicyclic chelate system.
In ethanol–acetonitrile mixture, the reaction of complexes
[Ni(L1-R)] complexes with excess solid imidazole (HIm) (8 equiv.)
afforded the corresponding bis(imidazole) nickel(II) complexes
623–658, 681–703 and 742–771 nm can be fairly attributed to the
*
different d(M) ?
p (L) transitions (MLCT) [36]. The recorded
spectra lack weak absorptions due to the different d–d transitions
which are most probably hidden under the very intense LMCT
band. The position of MLCT absorption bands in the spectra of
the square planar nickel(II) complexes [Ni(L1-R)] and [Ni(L2-R)] Á
nH2O were found to be affected by the nature of p-substituents
in the aroylhydrazone residue. The energy of the MLCT bands,
measured in wavenumber (cmÀ1), can be correlated with Ham-
mett’s rp constant and plot of wavenumber against rp gave a
straight line with a negative slope confirming the MLCT origin of
these absorption bands.
[Ni(L1-R)(HIm)2]
(5,
R1 = R2 = CH3,
R = C6H5,
p-CH3ÁC6H4,
p-CH3OÁC6H4, p-ClÁC6H4 or p-NO2ÁC6H4). The IR spectra of these
bis(imidazole) complexes display absorption bands at 3135–
3115 cmÀ1 region due to
m
(N–H) of the coordinated imidazole
besides a series of bands at 3075–3050, 2972–2930 and 2920–
2835 cmÀ1 which can be attributed to [
(C–H) + (N–H)] coupled
m
m
vibrations. Similar to the IR spectra of the parent square planar
complexes [Ni(L1-R)], the spectra of bis(imidazole) complexes
[Ni(L1-R)(HIm)2] do not show any absorptions due to hydrazone
On using aqueous ammonia, the reaction of H2L1-R (1,
R1 = R2 = CH3, R3 = C6H5, p-CH3ÁC6H4, p-CH3OÁC6H4) with Ni(CH3-
COO)2Á4H2O using (1:1) molar ratio in ethanol resulted in the
formation of the diamagnetic square planar neutral complexes
[Ni(L1-R] (2) which are identical to those isolated in the absence
of aqueous ammonia.. In these reactions, aqueous ammonia acts
as proton acceptor which facilitates the deprotonation of the
bishydrazone ligands. However, with bishydrazones having elec-
tron withdrawing substituents (1, R1 = R2 = CH3, R3 = p-ClÁC6H4 or
p-NO2ÁC6H4), the reaction proceeded with the formation of the
monoammine complexes [Ni(L1-R)ÁNH3]. The IR spectra of both
[Ni(L1-pCl)ÁNH3] and [Ni(L1-pNO2)ÁNH3] lack absorptions due to
t
(N–H) and amide I band (
1600–1575 cmÀ1 and 1555–1530 cmÀ1 due to
(N@C–C@N), respectively, confirming the deprotonation of both
m
C@O), but display intense bands at
m
(C@N–N@C) and
m
hydrazone arms and the bis(aroylhydrazone) acts as a dinegative
NNOO tetradentate ligand. The [Ni(L1-R)(HIm)2] complexes were
found to be paramagnetic with magnetic moments (
3.50 b) suggesting octahedral structure (5, R1 = R2 = CH3, R3 =
C6H5, p-CH3ÁC6H4, p-CH3OÁC6H4, p-ClÁC6H4 or p-NO2ÁC6H4). The
octahedral structure of both [Ni(L1-H)(HIm)2] and [Ni(L1-pNO2)
(HIm)2] has been confirmed by X-ray structural analysis.
leff = 3.15–
l
Different from the reaction of [Ni(L1-R)] (2) with imidazole
which gave the bis(imidazole) complexes, [Ni(L1-R)(HIm)2] (5),
the Ni(II) complexes derived from unsymmetric phenylglyoxal
bishydrazones [Ni(L2-R)]ÁnH2O afforded the corresponding
mono(imidazole) complexes [Ni(L2-R)(HIm)] (6, R1 = H, R2 = C6H5,
R3 = p-CH3ÁC6H4, p-CH3OÁC6H4, p-ClÁC6H4 and p-NO2ÁC6H4). The IR
spectral patterns of the mono(imidazole) complexes are more less
similar to those recorded for the analogous mono(ammine) com-
plexes and show a series of absorption bands at 3218–3131,
hydrazone
m(N–H), amide I m(C@O) and amide II, implying the
deprotonation of both aroylhydrazone arms. The spectra, also,
show a series of bands at 3365, 3320, 3245 cmÀ1 due to the differ-
ent vibration modes of coordinated NH3, besides bands at ca. 1640,
1580 and 1550 cmÀ1 due to d(N–H) of NH3,
m(C@N–N@C) and
m
(N@C–C@N) respectively. The solid complexes are paramagnetic
with magnetic moments being within the range 2.60–2.70lb
(298 K). From the stoichiometry, infrared spectral data and mag-
netic measurements, a distorted square pyramidal structure can
1660–1645, 1610–1580 cmÀ1, respectively, due to
coordinated imidazole, amide I [ (C@O)] of the uncoordinated
m(N–H) of the
m

2142
N.M.H. Salem et al. / Polyhedron 28 (2009) 2137–2148
Table 1
Crystal data and structure refinement for [Ni(L1-H)], [Ni(L1-pCH3O)] and [Ni(L1-pNO2)] complexes.
[Ni(L1-H)]
[Ni(L1-pCH3O)]
[Ni(L1-pNO2)]
Empirical formula
Formula weight
Temperature (K)
Wavelength (A)
Crystal system
Space group
Unit cell dimensions
a (Å)
C18H16N4NiO2
379.06
299(2)
0 .7 1073
orthorhombic
Pbca
C20H20N4NiO4
439.11
299(2)
0.71073
monoclinic
C2/c
C21H17N6NiO6
508.12
299(2)
0.71073
monoclinic
P21/n
6.6415(8)
28.430(3)
18.162(2)
90
12.057(1)
19.338(2)
8.765(1)
90
8.6378(9)
11.6264(9)
21.484(1)
90
b (Å)
c (Å)
a
(°)
b (°)
90
90
3429.3(7)
8
1.468
112.24(1)
90
1891.6(3)
4
1.542
1.062
93.375(8)
90
2153.9(3)
4
1.567
0.954
c
(°)
V (Å3)
Z
Dcalc (Mg m-3
)
Absorption coefficient (mmÀ1
F (0 0 0)
)
1.150
1568
912
1044
Crystal size (mm)
h range for data collection (°)
Limiting indices
0.56 Â 0.06 Â 0.04
0.52 Â 0.40 Â 0.08
0.50 Â 0.10 Â 0.10
4.30–26.37
4.14–26.37
4.19–26.37
À8 6 h 6 4, À35 6 k 6 34, À22 6 l 6 22 À15 6 h 6 15, À23 6 k 6 23, À10 6 l 6 5 À10 6 h 6 7, À14 6 k 6 14, À26 6 l 6 26
Reflections collected
22 610
5764
14 858
Independent reflections (Rint
)
3482 (0.1692)
1899 (0.0293)
4340 (0.0423)
Completeness to h
26.37 99.3%
26.37 97.8%
26.37 98.5%
Absorption correction
analytical
analytical
analytical
Maximum and minimum transmission
Refinement method
0.9538 and 0.5531
Full-matrix least-squares on F2
3482/0/226
0.9199 and 0.6082
full-matrix least-squares on F2
1899/0/134
0.9107 and 0.6471
full-matrix least-squares on F2
4340/0/307
Data/restraints/parameters
Goodness-of-fit on F2
1.044
1.077
0.950
Final R indices (I > 2
r
(I))
R1 = 0.0774, wR2 = 0.1351
R1 = 0.2679, wR2 = 0.2053
0.633 and À0.482
R1 = 0.0370, wR2 = 0.1000
R1 = 0.0435, wR2 = 0.1035
0.526 and À0.293
R1 = 0.0430, wR2 = 0.1018
R1 = 0.0838, wR2 = 0.1171
0.337 and À0.268
R indices (all data)
Largest difference in peak and hole (e AÀ3
)
R3-C@O residue, and
m
(C@N–N=@) of the deprotonated aroylhyd-
Ni(II) complexes derived from both mononegative tridentate and
dinegative tetradentate aroylhydrazones. The observed decrease
razone arm. The prepared mono(imidazole) complexes are diamag-
netic indicating square planar arrangement around the central
Ni(II) ion. The recorded electronic absorption spectra, in dichloro-
methane, are in agreement with this assignment.
Table 2
Selected bond distances (Å) and bond angles (°) for [Ni(L1-H)], [Ni(L1-pNO2)] and
[Ni(L1-pCH3O).
[Ni(L1-H)]
[Ni(L1-pNO2)]
[Ni(L1-pCH3O)]
3.2. X-ray molecular and supramolecular structures
Ni–O1
Ni–N1
Ni–N3
Ni–O2
C1–O1
C1–C2
C1–N2
N1–N2
C8–N1
C8–C9
C9–N3
N3–N4
C10–N4
C10–C11
C10–O2
N1–Ni–O1
N1–Ni–N3
N3–Ni–O2
O1–Ni–O2
N1–Ni–O2
N3–Ni–O1
O1–C1–N2
N2–C1–C2
C1–N2–N1
C8–N1–N2
N1–C8–C9
N3–C9–C8
C9–N3–N4
C10–N4–N3
O2–C10–N4
O2–C10–C11
1.874(5)
1.793(6)
1.804(6)
1.884(5)
1.316(9)
1.448(10)
1.334(10)
1.361(8)
1.310(9)
1.489(11)
1.316(9)
1.371(8)
1.349(9)
1.455(10)
1.305(9)
83.5(3)
1.8958(18)
1.805(2)
1.791(2)
1.882(2)
1.303(3)
1.471(4)
1.331(4)
1.373(3)
1.297(3)
1.477(4)
1.290(4)
1.384(4)
1.323(4)
1.471(4)
1.299(3)
83.69(9)
82.94(11)
83.97(10)
109.35(8)
166.83(9)
166.54(11)
124.5(3)
116.6(3)
106.5(2)
124.8(3)
110.6(3)
110.3(3)
124.1(2)
106.3(2)
124.4(3)
118.0(3)
Ni–O1
Ni–N1
Ni–N1#1
Ni–N1#1
C1–O1
C1–C2
C1–N2
N1–N2
C8–N1
1.8814(15)
1.7935(17)
1.7935(17)
1.8814(15)
1.305(3)
1.472(3)
1.329(3)
1.370(2)
1.304(3)
3.2.1. Square planar nickel(II) complexes [Ni(L1-R)] (2, R1 = R2 = CH3
and R3 = C6H5, p-CH3OÁC6H4, and p-NO2ÁC6H4)
The crystal data and structural refinement parameters for
[Ni(L1-H)], [Ni(L1-pCH3O)] and [Ni(L1-pNO2)]Á1/2C6H6 are listed in
Table 1, while selected bond distances (Å) and bond angles (o)
are collected in Table 2. The X-ray structures of [Ni(L1-H)],
[Ni(L1-pCH3O)] have been previously reported [35,37]. The X-ray
structure of the newly prepared [Ni(L1-pNO2)] Á 1/2C6H6 together
with the atomic numbering scheme are, respectively, shown in
Fig. 1. In these complexes the Ni(II) ion is in a distorted square pla-
nar environment where the bisaroylhydrazone ligand in these
complexes acts as a dinegative N2O2 tetradentate ligand, forming
the expected 5,5,5-membered tricyclic chelate ring system
[35–37]. The bond distances of Ni–O1 and Ni–O2 in both [Ni(L1-H)]
and [Ni(L1-pNO2)], and Ni–O1 and Ni–O1# (#, 1 À x, y, Àz + 1/2) in
[Ni(L1-pCH3O)], Table 2, are within the range 1.874–1.896 Å which
are significantly higher than the range (1.83–1.86 Å) reported for
square planar Ni(II) complexes with tridentate and tetradentate
aroylhydrazones having, respectively, 5,6-membered bicyclic and
5,5,6-membered tricyclic chelate rings [3,5,22,21], but are compa-
rable with the range (1.87–1.91 Å) reported for nickel(II) aroylhyd-
razone oxime complexes with 5,5-membered bicyclic chelate
system [26]. This can be related to the steric constraints imposed
by the 5,5,5- membered tricyclic chelate system. The Ni–N1 and
Ni–N3 bond distance range (1.79–1.80 Å), Table 2, is relatively
shorter than the range (1.82–1.84 Å) reported for square planar
C8–C9
1.484(3)
84.29(11)
83.47(7)
N1–Ni1–N1#1
N1–Ni–O1
N1#1–Ni–O1#
N1#1–Ni–O1
N1–Ni–O1#1
O–Ni–O1#1
O1–C1–N2
C1–N2–N1
C8–N1–N2
N1–C8–C9
N1–C8–C8#1
83.47(7)
167.70(7)
167.70(7)
108.80(10)
124.01(19)
105.98(17)
124.65(18)
124.29(19)
110.82
84.9(3)
83.1(3)
109.6(2)
167.9(3)
168.3(3)
122.7(7)
118.6(8)
106.6(6)
124.3(7)
110.4(8)
111.5(7)
125.1(7)
105.5(7)
123.5(8)
118.5(8)
#1 Symmetry transformations used to generate equivalent atoms: -x, y, -z + 1/2.

N.M.H. Salem et al. / Polyhedron 28 (2009) 2137–2148
2143
in both Ni–N1 and Ni–N3 bond distances may be due to apprecia-
ble (Ni–N) -interactions usually observed in coordinated diimine
each molecular unit is linked to four different neighboring molec-
ular units via two pairs of reciprocal C9HÁÁÁO2 (C9ÁÁÁO2 = 3.523 Å)
hydrogen bonds giving rise to a two dimensional stepped sheet
extending parallel to the ac-plane. Each molecular unit, in the
stepped sheet, is stacked from both sides to two adjacent molecu-
lar units of inverted symmetry via two reciprocal edge to face
p
systems. The bond distance ranges for C–N (imide) [C1–N2,
C10–N4] (1.32–1.33 Å) and C–O [C1–O1, C10–O2] (1.29–1.32 Å)
are consistent with the deprotonation of the enolimine tautomer
[11,17,20,21,49]. The ligand C–N (imine) [C8–N1, C9–N3], hydra-
zine [N1–N2, N3–N4], C–N(imide) [C1–N2, C10–N4] and C–O
[C1–O1, C10–O2] are intermediate between formal single and
double bonds indicating delocalization over the 5,5,5-membered
tricyclic chelate system.
CHÁÁÁ
p interactions between the C9HA methyl proton and
(C2–C7) phenyl
p
system [(CH9AÁÁÁCg1) = 2.816 Å, where Cg1 refers
to the phenyl ring centroid] forming a one dimensional array of
stacked molecular units as shown in Fig. 2. The dimensions of this
The structures of these square planar Ni(II) complexes show
interesting supramolecular architectures depending on the nature
of substituents in the hydrazone phenyl rings. No classic hydrogen
bonds are found in the crystal lattice of these complexes. However,
in the unsubstituted complex [Ni(L1-H)], two molecules are inter-
connected by two reciprocal C6HÁÁÁO2 (C6ÁÁÁO2 = 3.487 Å) hydrogen
bonds, forming a hydrogen bonded dimer. While in [Ni(L1-pCH3O)],
CHÁÁÁ
p interaction are consistent with those reported for other sys-
tems [50]. The Ni(II) coordination planes in this stacked array are
parallel to each other and the distance between two successive
planes is 3.36 Å. Both CHÁÁÁO and CHÁÁÁ
p non-covalent interactions
combine to form a three dimensional network of molecular units.
In the crystal lattice of [Ni(L1- pNO2)]Á1/2C6H6, one of the nitro
group oxygens (O4) is engaged in hydrogen bonding with the methyl
Fig. 1. ORTEP representation of [Ni(L1-pNO2)] with labeling atoms.
Fig. 2. CHÁÁÁ
p
non-covalent bond interactions in [Ni(L1-pCH3O)] complex.

2144
N.M.H. Salem et al. / Polyhedron 28 (2009) 2137–2148
Fig. 3. Intra- and Interchain CHÁÁÁO non-covalent bond interactions in [Ni(L1-pNO2)] double chains.
proton (H17B) of the neighboring molecule (CH17BÁÁÁO4,
C17ÁÁÁO4 = 3.19 Å) giving rise to an infinite chain propagating along
b axis. This chain is connected to another adjacent chain of inverted
symmetry by pairs of reciprocal hydrogen bonds between the other
nitro group oxygens (O3) of chain 1 and the phenyl ring H7 protons
of chain 2 (C7HÁÁÁO3 = 3.281 Å) forming an infinite strand of double
chains as shown in Fig. 3. The parameters of (CH17BÁÁÁO4)
[C–H17B = 0.96 Å, H17BÁÁÁO4 = 2.672 Å, C17ÁÁÁO4 = 3.19 Å and
C17–H17B–O4 angle = 114.79o] are in the typical range reported
for such interaction [51,52]. The benzene molecules in the unit cell
do not show any non-covalent intermolecular interactions.
3.2.2. Bis(imidazole) and mono(imidazole) nickel(II) complexes
The crystal data and structural refinement parameters for the
bis(imidazole) nickel(II) complexes, [Ni(L1-H)(HIm)2] Á 1/3H2O,
[Ni(L1-NO2)(HIm)2] and the mono(imidazole) Ni(II) complex
[Ni(L2-pCH3)(HIm)] are, respectively, listed in Table 3. The struc-
tures of [Ni(L1-H)(HIm)2] and [Ni(L1-NO2)(HIm)2] together with
their atomic numbering scheme are, respectively, shown in Figs. 4
and 5. Selected bond distances (Å) and bond angles (o) for [Ni(L1-
H)(HIm)2] Á 1/3H2O and [Ni(L1-NO2)(HIm)2] are listed in Table 4.
The crystal structure of [Ni(L1-H)(HIm)2] Á 1/3H2O consists of three
crystallographically independent molecular units, namely Ni1, Ni2
Table 3
Crystal data and structure refinement for [Ni(L1-H)(HIm)2], [Ni(L1-pNO2)(HIm)2] and [Ni(L2-pCH3)(HIm)] complexes.
[Ni(L1-H)(HIm)2]
[Ni(L1-pNO2)(HIm)2]
[Ni(L2-pCH3)(HIm)]
Empirical formula
Formula weight
T (K)
C72H74N24Ni3O7
1563.68
299(2)
C24H22N10NiO6
605.23
299(2)
C27H24N6NiO2
523.23
296(2)
k (Å)
0.71073
monoclinic
C2/c
0.71073
monoclinic
P21/c
1.54180
monoclinic
P21/c
Crystal system
Space group
Unit cell dimensions
a (Å)
70.257(13)
25.681(1)
12.552(2)
b (Å)
8.493(2)
13.0453(8)
11.616(2)
c (Å)
26.737(9)
8.0847(5)
17.949(3)
a
(°)
90
90
90
b (°)
105.64(3)
92.911(5)
106.26(1)
c
(°)
90
15 363(7)
90
2705.0(3)
90
2512.4(7)
V (Å3)
Z
8
4
4
DCalc (Mg mÀ3
)
1.352
0.796
6512
1.486
0.776
1248
1.383
1.409
1088
Absorption coefficient (mmÀ1
F (0 0 0)
)
Crystal size (mm)
h Range for data collection
Limiting indices
0.44 Â 0.20 Â 0.18
0.60 Â 0.60 Â 0.30
0.475 Â 0.40 Â 0.125
4.08–27.24
4.12–26.37
3.84–66.96
À79 6 h 6 88, À10 6 k 6 10,
À33 6 l 6 34
À32 6 h 6 31, À15 6 k 6 16, À6 6 l 6 10
À14 6 h 6 1, 0 6 k 6 13, À20 6 l 6 21
Reflections collected
64 901
18 657
4691
Independent reflections (Rint
Completeness to h
)
16 399 (0.1074)
27.24 95.5%
5441 (0.0383)
26.37 98.7%
4474 (0.0376)
66.96 99.9 %
Absorption correction
Maximum and minimum transmission
Refinement method
semi-empirical from equivalents
0.9761 and 0.8909
full-matrix least-squares on F2
16 399/2/961
1.002
analytical
empirical
0.8255 and 0.7030
full-matrix least-squares on F2
5441/0/379
0.7364 and 0.5268
full-matrix least-squares on F2
4474/1/380
Data/restraints/parameters
Goodness-of-fit on F2
1.049
1.062
Final R indices I > 2
R indices (all data)
r
(I)
R1 = 0.0969, wR2 = 0.2592
R1 = 0.2095, wR2 = 0.3350
1.172 and À0.573
R1 = 0.0400, wR2 = 0.1041
R1 = 0.0501, wR2 = 0.1093
0.433 and À0.342
R1 = 0.0306, wR2 = 0.1011
R1 = 0.0428, wR2 = 0.1052
0.294 and À0.224
Largest difference in peak and hole (e ÅÀ3
)

N.M.H. Salem et al. / Polyhedron 28 (2009) 2137–2148
2145
and Ni3 molecular units, in addition to one water molecule while
that of [Ni(L1-NO2)(HIm)2] consists of one type of discrete molecu-
lar units. The central Ni(II) in each of the three molecular units of
[Ni(L1-H)(HIm)2]Á1/3H2O as well as in [Ni(L1-NO2)(HIm)2] is six
coordinate in a distorted octahedral geometry, where the dinega-
tive bisaroylhydrazone ligand occupies the equatorial plane while
the two imidazole rings are situated in the two apical positions.
The bite angles in the three molecular units of [Ni(L1-H)(HIm)2]Á
1/3H2O and [Ni(L1-NO2)(HIm)2], Table 4, are less than 90o while
the trans angles in the equatorial planes are much less than 180o.
The axial angles formed between the central Ni and the coordinated
imidazole nitrogens, N5–Ni–N7, N13–Ni–N15, and N21–Ni–N23, in
Ni1, Ni2, and Ni3 molecular units of [Ni(L1-H)(HIm)2]Á1/3H2O are
156.2(3)o, 154.8(3)o and 161.1(3)o, respectively, while the
Fig. 4. ORTEP representation of the three crystallographic independent molecular units of [Ni(L1-H)(HIm)2] with labeling atoms.
Fig. 5. ORTEP representation of [Ni(L1-pNO2)(HIm)2] with labeling atoms.

2146
N.M.H. Salem et al. / Polyhedron 28 (2009) 2137–2148
corresponding angle (N5–Ni–N7) in [Ni(L1-NO2)(HIm)2] is 159.09o.
Hereafter, the imidazole ring in these complexes are designated by
the tertiary nitrogen directly coordinated to the Ni(II).
Ni3 molecular units are also linked to the adjacent Ni2 molecular
units, forming another Ni2–Ni3 chain but of inverted symmetry.
The Ni2–Ni3 chains are connected together by water bridges where
the water H72 protons are involved in hydrogen bond formation
with the enolimine O2 oxygens of the Ni2 molecular units while
the water O7 oxygens form hydrogen bonds with the imidazole
The N–H protons of the two coordinated imidazole rings in both
[Ni(L1-H)Á(HIm)2]Á1/3 H2O and [Ni(L1-NO2)(HIm)2] play a crucial
role in their crystal packing. In [Ni(L1-H)Á(HIm)2]Á1/3 H2O, the
Ni1, Ni2 and Ni3 molecular units are involved in different supra-
molecular assemblies. The N6H proton of the N5 imidazole ring
in Ni1 molecular unit is involved in intermolecular hydrogen bond
formation, N6HÁÁÁO1 (N6ÁÁÁO1 = 2.720 Å), ith the enolimine oxygen
O1 of one adjacent Ni1 molecular unit while the other N8H proton
of the N7 imidazole ring forms N8HÁÁÁN2 (N8ÁÁÁN2 = 2.864 Å) hydro-
gen bond with the hydrazone N2 nitrogen of another adjacent Ni1
molecular units, giving rise to a supramolecular triple stranded
helical chain (Ni1 chain) propagating along b-axis as shown in
Fig. 6a. The Ni2 molecular units are also linked together via
N16HÁÁÁN10 (N16ÁÁÁN10 = 3.080 Å) hydrogen bonds, forming a lin-
ear chain extended along b-axis. In this chain, two successive Ni2
molecular units are further linked to one Ni3 molecular unit via
N14HÁÁÁO6 (N14ÁÁÁO6 = 2.934 Å) and N24HÁÁÁO4 (N24ÁÁÁO4 =
2.75.53 Å) hydrogen bonds, respectively, thus the interconnected
Ni2- and Ni3-molecular units form mono stranded helical chain
(Ni2–Ni3 chain) extended parallel to the b-axis as shown in
N22–H
protons
of
Ni3
molecular
units
(N22HÁÁÁO7,
N22ÁÁÁO7 = 2.839 Å) of the neighboring Ni2–Ni3 chain giving rise
to a two-dimensional sheet of helical chains extending parallel to
bc-plane. In the crystal lattice of [Ni(L1-H) Á (HIm)2] Á 1/3H2O, the
Ni1 molecular units of Ni1 chains are connected from both sides
to Ni2 and Ni3 molecular units by C23ÁÁÁN12 and C52HÁÁÁC12,
respectively. Thus the Ni1 chains are embedded between the two
extended sheets originated from Ni2 and Ni3 molecular units.
In [Ni(L1-NO2)(HIm)2] the molecular units are linked together by
N6HÁÁÁO1 (N6ÁÁÁO1 = 2.763 Å) and a trifurcated hydrogen bond be-
tween N8H imidazole proton and N3 imine nitrogen (N8HÁÁÁN3,
N8ÁÁÁN3 = 2.622 Å), N4 hydrazine nitrogen (N8HÁÁÁN4, N8ÁÁÁN4 =
2.642 Å) and N5 imidazole nitrogen (N8HÁÁÁN5, N8ÁÁÁN5 = 2.559 Å),
giving rise to a supramolecular triple stranded helical chain propa-
gating along the c-axis more or less similar to Ni1 chain in
[Ni(L1-H)(HIm)2]Á1/3H2O. The helical chain is further stabilized by
intrachain C–HÁÁÁ
p interactions between aromatic C16H and N7
Fig. 6b. The Ni2–Ni3 helical chain is stabilized by CHÁÁÁ
actions between the N13 imidazole C43H proton and the
(C49–C54) phenyl system, and between the phenyl (C59–C64)
p
inter-
imidazole
p
system [50]. In the crystal lattice of [Ni(L1-NO2)(HIm)2]
the helical chains are linked together by CHÁÁÁÁN non-covalent bond
interactions between H23A methyl protons of one chain and N2
hydrazine nitrogen of the adjacent chain, forming a sheet of infinite
p
phenyl C63H proton and N23 imidazole
p system. Similarly, the
Table 4
Selected bond distances (Å) and bond angles (°) for [Ni(L1-H)(HIm)2] and [Ni(L1-H)(HIm)2] complexes.
[Ni(L1-H)(HIm)2]
[Ni(L1-pNO2)(HIm)2]
Ni1 Molecular unit
Ni2 Molecular unit
Ni3 Molecular unit
N1–Ni1
O1–Ni1
O2– Ni1
N3– Ni1
N5–Ni1
N7– Ni1
2.029(5)
2.275(5)
2.151(5)
1.995(6)
2.034(6)
2.070(6)
N9–Ni2
O3–Ni2
O4–Ni2
N11–Ni2
N15–Ni2
N13–Ni2
2.002(6)
2.178(5)
2.69(6)
1.997(6)
2.048(7)
2.057(6)
N17–Ni3
O5–Ni3
O6– Ni3
N19–Ni3
N21–Ni3
N23– Ni3
2.015(7)
2.243(7)
2.280(5)
1.999(6)
2.051(7)
2.053(7)
N1–Ni1
O1–Ni1
O2– Ni1
N3– Ni1
N5–Ni1
N7– Ni1
2.0077(18)
2.2397(16)
2.1726(15)
1.9881(18)
2.0725(19)
2.0481(18)
C1–O1
C1–C2
C1–N2
N1–N2
C8–N1
C8–C9
C9–N3
N3–N4
C10–N4
C10–O2
C10–C11
1.271(9)
1.462(11)
1.378(10)
1.405(8)
1.307(9)
1.480(12)
1.281(9)
1.359(8)
1.351(10)
1.277(9)
1.478(12)
C25–O3
1.266(10)
1.495(12)
1.338(10)
1.388(9)
C49–O5
1.290(12)
1.497(14)
1.296(12)
1.368(9)
1.278(10)
1.486(11)
1.298(9)
C1–O1
C1–C2
C1–N2
N1–N2
C8–N1
C8–C9
C9–N3
N3–N4
C10–N4
C10–O2
C10–C11
1.274(3)
1.500(3)
1.328(3)
1.370(3)
1.299(3)
1.475(3)
1.299(3)
1.369(2)
1.343(3)
1.266(3)
1.494(3)
C25–C26
C25–N10
N9–N10
C32– N9
C32–C33
C33–N11
N11–N12
C34–N12
C34–O4
C49–C50
C49–N18
N17–N18
C56–N17
C56–C57
C57–N19
N19 –N20
C58–N20
C58–O6
1.297(9)
1.465(11)
1.310(10)
1.354(9)
1.330(10)
1.275(10)
1.516(13)
1.382(9)
1.332(10)
1.251(10)
1.529(12)
C34–C35
C58–C59
N1–Ni1–O1
N3–Ni1–N1
N7–Ni1–O1
N7–Ni1–O2
N5–Ni1–O2
N3–Ni1–N5
O2–Ni1–O1
N5–Ni1–O1
N5–Ni1–N7
N1–Ni1–O2
72.1(2)
78.3(3)
8 2.3(2)
8 5.0(2)
88.3(2)
N9–Ni2–O3
N11–N2–N9
N13–Ni2–O3
N13–Ni2–O4
N15–Ni2–O4
N11–Ni2–N15
O3–Ni2–O4
O3–Ni2–N15
N15–Ni2–N13
N9–Ni2–O4
74.5(2)
78.6(3)
85.8(2)
86.2(2)
84.3(3)
100.0(3)
134.7(2)
84.3(3)
154.8(3)
150.6(2)
N17–Ni3–O5
N19–Ni3–N17
N23–Ni3–O5
N23–Ni3–O6
N21–Ni3–O6
N17–Ni3–N21
O5–Ni3–O6
N21–Ni3–O5
N21–Ni3–N23
N17–Ni3–O6
73.0(3)
77.8(3)
86.5(3)
83.3(2)
84.3(3)
96.2(3)
135.9(3)
87.6(3)
161.1(3)
151.0(2)
N1–Ni1–O1
N3–Ni1–N1
N7–Ni1–O1
N7–Ni1–O2
N5–Ni1–O2
N3–Ni1–N5
O2–Ni1–O1
N5–Ni1–O1
N5–Ni1–N7
N1–Ni1–O2
73.51(7)
78.27(7)
85.77(7)
87.39(7)
86.01(7)
101.63(7)
133.18(6)
84.36(7)
159.09(7)
153.29(7)
96.2(3)
134.47(19)
8 6.3(2)
156.2(3)
153.4(2)
O1–C1–C2
N2–C1–C2
O1–C1–N2
C1–N2–N1
N2–N1–C8
N1–C8–C9
N3–C9–C8
C9–N3–N4
C10–N4–N3
O2–C10–N4
O2–C10–C11
120.2(7)
113.9(7)
125.9(7)
106.1(6)
118.8(6)
112.5(7)
115.8(7)
121.8(6)
1 0 7.9(6)
126.1(7)
118.3(8)
O3–C25–C26
N10–C25–C26
O3–C25–N10
C25–N10–N9
C32–N9–N10
N9–C32–C33
N11–C33–C32
C33–N11–N12
C34–N12–N11
O4–C34–N12
O4–C34–C35
118.8(7)
114.9(7)
126.2(8)
108.0(6)
122.2(6)
114.1(7)
114. 2(7)
119.5(7)
1 0 9.6(7)
124.7(8)
115.9(8)
O5–C49–C50
N18–C49–C50
O5–C49–N18
C49–N18–N17
C56–N17–N18
N17–C56–C57
N19–C57–C56
C57–N19–N20
C58–N20–N19
O6–C58–N20
O6–C58–C59
116.8(10)
114.7(11)
128.6(9)
107.8(8)
120.0(7)
114.3(7)
112. 9(7)
119.4(6)
108.4(7)
127.9(8)
118.5(8)
O1–C1–C2
N2–C1–C2
O1–C1–N2
C1–N2–N1
N2–N1–C8
N1–C8–C9
N3–C9–C8
C9–N3–N4
C10–N4–N3
O2–C10–N4
O2–C10–C11
118.9(2)
114.3(2)
126.8(2)
108.87(18)
120.67(18)
113.83(19)
113.65 (19)
121.25(18)
108.08(16)
126.62(19)
118.72(19)

N.M.H. Salem et al. / Polyhedron 28 (2009) 2137–2148
2147
chains extended parallel to the bc-plane. The chains in one sheet are
further interconnected to symmetry inverted chains of the adjacent
sheet by C24HCÁÁÁO6, C24HAÁÁÁO5 and C21HÁÁÁO5 interactions, giving
rise to two dimensional arrays of helical chains.
of the phenyl arm, forming a 5,6-membered bicyclic chelate ring.
The ketoamide O2 oxygen of the phenyl arm remains uncoordi-
nated. It is thus apparent that the bis(aroylhydrazone) molecule acts
as a dinegative NNO tridentate ligand rather than the expected
dinegative NNOO tetradentate ligand. The fourth coordination site
is occupied by the N5 imidazole nitrogen [Ni–N5 = 1.899(17) Å].
This unexpected coordination mode can be related to the unsym-
metric nature of the coordinated bis(aroylhydrazone) ligand. The
imidazole N6–H proton is involved in hydrogen bond formation
with the uncoordinated ketoamide O2 oxygen forming, hydrogen
bonded dimer. In this dimer, the two imidazole rings are involved
The structure of the monoimidazole complex, [Ni(L2-pCH3)
(HIm)], together with the atomic numbering scheme is shown in
Fig. 7. Selected bond distances (Å) and bond angles (o) for
[Ni(L2-pCH3)(HIm)] are listed in Table 5. The central nickel (II) in
[Ni(L2-pCH3)(HIm)] is in a distorted square planar geometry, being
coordinated to the imine N1 nitrogen [Ni–N1 = 1.8154(17) Å] and
the deprotonated enolimide O1 oxygen [Ni–O1 = 1.8721(14) Å] of
the aldehydic arm, besides the deprotonated hydrazide N3 nitrogen
in
p–p
stacking interaction [Cg5ÁÁÁCg5 = 4.102 Å]. The hydrogen
Fig. 6. Ni1- and Ni2–Ni3-chains in [Ni(L1-H)(HIm)2] complex: (a) triple stranded helical Ni1-chain and (b) Ni2–Ni3 helical chain.
Fig. 7. ORTEP representation of [Ni(L2-pCH3)(HIm)] with labeling atoms.

2148
N.M.H. Salem et al. / Polyhedron 28 (2009) 2137–2148
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Selected bond distances (Å) and bond angles (°) for [Ni(L2-pCH3)(HIm)] complex.
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Bond distances (Å)
Bond angles (°)
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Ni–N1
Ni–N3
Ni–N5
Ni–O1
1.8154(17)
1.8695(16)
1.8990(17)
1.8721(14)
1.481(3)
1.294(2)
1.312(3)
1.392(2)
1.298(2)
1.432(3)
1.494(2)
1.298(2)
1.352(2)
1.398(2)
1.493(3)
1.224(2)
N1–Ni–O1
N1–Ni–N3
N3–Ni–N5
O1–Ni–N5
N1–Ni–N5
N3–Ni–O1
O1–C1–C2
N2–C1–C2
N2–C1–O1
C1–N2–N1
C9–N1–N2
N1–C9–C10
C9–C10–C11
N4–C10– C11
C10–N4–N3
N4–N3–C17
N3–C17–C18
O2–C17–N3
O2–C17–C18
83.16(6)
92.16(7)
96.63(7)
89.49(7)
C1–C1
165.76(7)
171.09(7)
119.80(18)
117.53(19)
122.67(17)
107.80(16)
115.94(17)
122.41(19)
119.00(17)
115.36(16)
121.79(15)
109.95(14)
120.57(16)
120.02(17)
119.39(17)
C1–O1
C1–N2
N1–N2
C9–N1
C9–C10
C10–C11
C10–N4
N3–N4
C17– N3
C17–C18
C17–O2
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bonded dimers are linked together by two pairs of reciprocal CHÁÁÁ
interactions between the C12H proton of the phenylglyoxal phenyl
(C11–C16) ring and the N5 imidazole -system
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along b-axis. The chain of dimers is further stabilized by C9HÁÁÁC7
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bonded dimers chain are interconnected by reciprocal C23HÁÁÁÁC9
interactions.
p
p
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Appendix A. Supplementary data
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CCDC 721269, 721270, 72171, 721272, 721273 and 721274
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[Ni(L1-pCH3O)],
[Ni(L1-pNO2)] Á 1/2C6H6,
[Ni(L1-H)(HIm)2] Á 1/
3H2O, [Ni(L1-NO2)(HIm)2] and [Ni(L2-pCH3)(HIm)], respectively.
These data can be obtained free of charge via http://www.ccdc.ca-
m.ac.uk/conts/retrieving.html, or from the Cambridge Crystallo-
graphic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK;
fax: (+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk. Sup-
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