Ligating properties of tridentate Schiff base ligands, 2-[[(2-pyridinylmethyl)imino]methyl] phenol (HSALIMP) and 2-[[[2-(2-pyridinyl)ethyl]imino]methyl]phenol (HSALIEP) with zinc(II), cadmium(II), nickel(II) and manganese(III) ions

Article abstract of DOI:10.1016/S0020-1693(00)00010-4

A series of zinc(II), cadmium (II), nickel(II) and manganese (III) complexes with two potentially tridentate (NNO) Schiff base ligands, 2-[[(2-pyridinylmethyl)imino]methyl]phenol (HSALIMP) and 2-[[[2-(2-pyridinyl)ethyl]imino]methyl]phenol (HSALIEP) have been synthesized and structurally characterized through IR, ¹H, ¹³C, and 2-D NMR spectroscopy and in two cases by X-ray crystallography. The Schiff base ligands HSALIMP and HSALIEP are generated from 1 + 1 condensation of salicylaldehyde with 2-aminomethylpyridine and 2(2-aminoethyl)pyridine, respectively. HSALIMP behaves as a tridentate (NNO) or a bidentate (NN) ligand, depending upon the nature of the anion. On reaction with zinc(II) salts HSALIMP gives two types of complexes, (a) [Zn(SALIMP)X]₂·yH₂O (X = NO₃, y = 0 (I); X = I, y = 3 (II) and (b) [Zn(HSALIMP)Cl₂]·H₂O (III). HSALIMP reacts with nickel(II) bromide to form a mononuclear complex [Ni(HSALIMP)₂Br₂] (VIII), in which one metal ion combines with two neutral HSALIMP ligands. However HSALIEP, a similar ligand with one additional carbon atom in the chain, acts as a tridentate ligand (NNO), with the phenolate oxygen deprotonated, irrespective of the nature of the anion, forming dimeric compounds of 1:1 metal:ligand stoichiometry with zinc(II) and cadmium(II) ions, [Zn(SALIEP)X]₂·yH₂O (X = NO₃, y = 0 (IV); X = Cl, y = 2 (V); X = I, y = 1 (VI), [Cd(SALIEP) (NO₃]₂·C₂H₅OH (VII) and a monomeric complex of 1:2 metal:ligand stoichiometry with manganese(III) ion, [Mn(SALIEP)₂](ClO₄) (IX). The single crystal X-ray structures of the [Zn(SALIEP)(NO₃)]₂ (IV) dimer, [Mn(SALIEP)₂](ClO₄) (IX), and [Zn(AMP)₂(NO₃)₂] (X), a minor product obtained from the filtrate of I, have been determined. IV consists of centrosymmetric dimer in which deprotonated phenolates bridge the two five-coordinate metal atoms and link the two halves of the dimer. The structure of IX consists of a centrosymmetric molecule in which the manganese(III) ion is bound to two tridentate SALIEP ligands in a nearly regular octahedral arrangement. The structure of X consists of a centrosymmetric monomer in which the six coordinate octahedral zinc(II) ion is bonded equtorially to two bidentate 2-aminomethylpyridine ligands and axially to two monodentate nitrate groups. (C) 2000 Elsevier Science S.A.

Full text of DOI:10.1016/S0020-1693(00)00010-4

www.elsevier.nl/locate/ica
Inorganica Chimica Acta 300–302 (2000) 683–692
Ligating properties of tridentate Schiff base ligands,
2-[[(2-pyridinylmethyl)imino]methyl] phenol (HSALIMP) and
2-[[[2-(2-pyridinyl)ethyl]imino]methyl]phenol (HSALIEP) with
zinc(II), cadmium(II), nickel(II) and manganese(III) ions. X-ray
crystal structures of the [Zn(SALIEP)(NO3)]2 dimer,
[Mn(SALIEP)2](ClO4), and [Zn(AMP)2(NO3)2]
S.S. Tandon a,b,*, S. Chander b, L.K. Thompson a
a Department of Chemistry, Memorial Uni6ersity of Newfoundland, St. John’s, Newfoundland, Canada, A1B 3X7
b Department of Chemistry, Guru Nanak De6 Uni6ersity, Amritsar-143005, Punjab, India
Received 7 October 1999; accepted 23 November 1999
Abstract
A series of zinc(II), cadmium (II), nickel(II) and manganese (III) complexes with two potentially tridentate (NNO) Schiff base
ligands, 2-[[(2-pyridinylmethyl)imino]methyl]phenol (HSALIMP) and 2-[[[2-(2-pyridinyl)ethyl]imino]methyl]phenol (HSALIEP)
1
have been synthesized and structurally characterized through IR, H, 13C, and 2-D NMR spectroscopy and in two cases by X-ray
crystallography. The Schiff base ligands HSALIMP and HSALIEP are generated from 1+1 condensation of salicylaldehyde with
2-aminomethylpyridine and 2(2-aminoethyl)pyridine, respectively. HSALIMP behaves as a tridentate (NNO) or a bidentate (NN)
ligand, depending upon the nature of the anion. On reaction with zinc(II) salts HSALIMP gives two types of complexes, (a)
[Zn(SALIMP)X]2·yH2O (X=NO3, y=0 (I); X=I, y=3 (II) and (b) [Zn(HSALIMP)Cl2]·H2O (III). HSALIMP reacts with
nickel(II) bromide to form a mononuclear complex [Ni(HSALIMP)2Br2] (VIII), in which one metal ion combines with two neutral
HSALIMP ligands. However HSALIEP, a similar ligand with one additional carbon atom in the chain, acts as a tridentate ligand
(NNO), with the phenolate oxygen deprotonated, irrespective of the nature of the anion, forming dimeric compounds of 1:1
metal:ligand stoichiometry with zinc(II) and cadmium(II) ions, [Zn(SALIEP)X]2·yH2O (X=NO3, y=0 (IV); X=Cl, y=2 (V);
X=I, y=1 (VI), [Cd(SALIEP) (NO3)]2·C2H5OH (VII) and a monomeric complex of 1:2 metal:ligand stoichiometry with
manganese(III) ion, [Mn(SALIEP)2](ClO4) (IX). The single crystal X-ray structures of the [Zn(SALIEP)(NO3)]2 (IV) dimer,
[Mn(SALIEP)2](ClO4) (IX), and [Zn(AMP)2(NO3)2] (X), a minor product obtained from the filtrate of I, have been determined.
IV consists of centrosymmetric dimer in which deprotonated phenolates bridge the two five-coordinate metal atoms and link the
two halves of the dimer. The structure of IX consists of a centrosymmetric molecule in which the manganese(III) ion is bound to
two tridentate SALIEP ligands in a nearly regular octahedral arrangement. The structure of X consists of a centrosymmetric
monomer in which the six coordinate octahedral zinc(II) ion is bonded equtorially to two bidentate 2-aminomethylpyridine ligands
and axially to two monodentate nitrate groups. © 2000 Elsevier Science S.A. All rights reserved.
Keywords: X-ray crystallography; Zinc(II) complexes; Cadmium(II) complexes; Nickel(II) complexes; Maganese(II) complexes; Tridentate Schiff
base ligands
1. Introduction
* Corresponding author. Present address: College of the North
Atlantic, Grand Falls-Windsor Campus, PO Box 413, St.Catherine
synthesis and the ligating properties of the tridentate
Street Grand Falls-Windsor, Newfoundland, A2A 2J8, Canada. Tel.:
+1-709-292 5617; fax: +1-709-489 4180.
E-mail address: santokh.tandon@northatlantic.nf.ca (S.S. Tandon)
In our earlier communications [1–3], we reported the
(N2O) Schiff base ligands, 2-[[(2-pyridinylmethyl)-
imino]methyl]phenol (HSALIMP) and 2-[[[2-(2-
0020-1693/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0020-1693(00)00010-4

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S.S. Tandon et al. / Inorganica Chimica Acta 300–302 (2000) 683–692
pyridinyl)ethyl]imino]methyl]phenol (HSALIEP) with
copper(II) and their saturated counterparts, 2-[[(2-
stirring at 100°C. The colour of the reaction mixture
immediately changed from dark yellow to off white.
The resulting mixture was refluxed for 30 min and
concentrated to about 10 ml under reduced pressure.
An off white solid separated after keeping the concen-
trated mixture at r.t. for 12 h, was filtered off, washed
with dry ethanol (3×5 ml) and dried under vacuum at
60°C for 12 h. Yield: 80%. Anal. Calc. for [Zn(-
SALIMP)(NO3)]2 (I): C, 46.08; H, 3.25; N, 12.41; Zn,
19.35. Found: C, 45.82; H, 3.44; N, 12.08; Zn, 18.46%.
umax.(nm) (m dm3 mol−1 cm−1): 374 (4110), 268 (6750).
pyridinylmethyl)amino]methyl]phenol
(HSALAMP)
and 2-[[[2-(2-pyridinyl) ethyl]amino]methyl]phenol
(HSALAEP) with copper(II), zinc(II) and cadmium(II)
ions. The X-ray crystal structures of [Cu(SALIMP)-
(NO3)],
[Cu(HSALAMP)Cl2]·C2H5OH
[2],
[Zn-
(SALAEP)(NO3)]2 and [Cd(SALAEP)(NO3)]2 were also
reported [1–3]. In these complexes, the Schiff bases
behave either as tridentate (NNO) or bidentate (NN)
ligands, depending upon the nature of the anions
present and the reaction conditions.
In continuation of our interest in the coordinating
behaviour of ligands of this sort we wish to report the
results of our investigations on the ligating properties
of the tripodal [NNO] Schiff base ligands HSALIMP
and HSALIEP with zinc(II), cadmium(II), nickel(II)
and manganese(III) ions. The X-ray crystal structures
of dimeric zinc(II) complex (IV), the monomeric man-
ganese(III) complex (IX) of the ligand SALIEP, and the
monomeric zinc(II) complex (X) of 2-amino methyl-
pyridine are reported.
2.3.2. [Zn(SALIMP)I]2·3H2O (II)
II was obtained, as an off white solid, in a similar
manner to I by replacing Zn(NO3)2 with ZnI2 and
stirring the reaction mixture at ambient temperature for
2 h. Yield: 90%. Anal. Calc. for [Zn(SALIMP)I]2·3H2O
(II): C, 36.24; H, 3.25; Zn, 15.21. Found: C, 35.94; H,
3.31; Zn, 14.57%. umax.(nm) (m dm3 mol−1 cm−1): 372
(7450), 269 (11150).
2.3.3. [Zn(HSALIMP)Cl2]·H2O (III)
III was obtained similarly by replacing ZnI2 with
ZnCl2. Yield: 87%. Anal. Calc. for [Zn(HSALIMP)Cl2]·
H2O (III): C, 42.60; H, 3.85; N, 7.64; Zn, 17.83. Found:
C, 42.85; H, 3.39; N, 7.90; Zn, 17.66%. umax.(nm) (m dm3
mol−1 cm−1): 375 (4650), 318 (2650), 266 (10400).
2. Experimental
2.1. Materials
2.3.4. [Zn(SALIEP)(NO3)]2 (IV)
The solvents were dried by standard procedures.
2-Aminomethyl pyridine and 2(2-aminoethyl)pyridine
were used as supplied by Aldrich. All other chemicals
used were analytical or reagent grade and used without
further purification.
A solution of HSALIEP (1.0 mmol) in dry ethanol
(15 ml) was added dropwise with constant stirring to a
solution of zinc(II) nitrate (1.0 mmol) in the same
solvent (15 ml) at ambient temperature. A pale yellow
solid separated immediately. The resulting mixture was
stirred at ambient temperature for 2 h and the solid was
filtered off, washed with ethanol (2×5 ml) and dried
under vacuum at 60°C for 12 h. Yield: 80%. Anal. Calc.
for [Zn(SALIEP)(NO3)]2 (IV): C, 47.54; H, 3.96; N,
11.88; Zn, 18.50. Found: C, 47.77; H, 3.76; N, 12.04;
Zn, 18.62%. umax.(nm) (m dm3 mol−1 cm−1): 367 (7935),
268 (11020).
2.2. Synthesis of the ligands
2.2.1. 2-[[(2-pyridinylmethyl)imino]methyl]phenol
(HSALIMP) and 2-[[[2-(2-pyridinyl)ethyl]imino]
methyl]phenol (HSALIEP)
The Schiff base ligands HSALIMP and HSALIEP
were obtained by reacting salicylaldehyde (3.1 g, 25
mmol) with 2-aminomethylpyridine (2.7 g, 25 mmol)
and 2-(2-aminoethyl)pyridine (3.05 g, 25 mmol), respec-
tively in absolute ethanol (50 ml) under reflux for about
30 min. They were used immediately to avoid notice-
able degradation, which occurred on standing for ex-
tended periods. HSALIMP and HSALIEP were
characterized through 1H, 13C and 2D NMR spec-
troscopy (Tables 5 and 6).
2.3.5. [Zn(SALIEP)Cl]2·2H2O (V)
V was prepared by the same procedure as used for
the synthesis of IV by replacing zinc nitrate with zinc
chloride. Yield: 86%. Anal. Calc. for [Zn(-
SALIEP)Cl]2·2H2O (V): C, 48.84; H, 4.36; Zn, 19.04.
Found: C, 49.33; H, 4.39; Zn, 19.59%. umax.(nm) (m dm3
mol−1 cm−1): 368 (7205), 268 (10920).
2.3.6. [Zn(SALIEP)I]2·H2O (VI)
2.3. Synthesis of the complexes
VI was obtained similarly by replacing zinc nitrate
with zinc iodide. Yield: 85%. Anal. Calc. for [Zn(-
SALIEP)I]2·H2O (VI): C, 39.40; H, 3.28; N, 6.57; Zn,
15.34. Found: C, 39.29; H, 3.46; N, 6.67; Zn, 15.11%.
umax.(nm) (m dm3 mol−1 cm−1): 368 (5300), 305 (2835),
267 (9690).
2.3.1. [Zn(SALIMP)(NO3)]2 (I)
HSALIMP (1.0 mmol), dissolved in warm dry
ethanol (5 ml), was added dropwise to a solution of
zinc nitrate (1.0 mmol) in dry ethanol (10 ml), with

S.S. Tandon et al. / Inorganica Chimica Acta 300–302 (2000) 683–692
685
2.3.7. [Cd(SALIEP)(NO3)]2·C2H5OH (VII)
2.4. Physical measurements
A solution of HSALIEP (1.0 mmol) in dry ethanol
(20 ml) was added dropwise with constant stirring to a
solution of cadmium nitrate (1.0 mmol) in the same
solvent (10 ml) at ambient temperature. The resulting
mixture was stirred at ambient temperature for 24 h.
Triethylamine (2 mmol) was added and the solution
was concentrated to 5 ml under reduced pressure. The
resulting solution produced a pale yellow solid after
standing at r.t. for 24 h, which was filtered off, washed
with dry ethanol (2×2 ml) and dried under vacuum at
60°C for 8 h. Yield: 75%. Anal. Calc. for [Cd-
(SALIEP)(NO3)]2·C2H5OH (VII): C, 42.52; H, 3.82; Cd,
26.59. Found: C, 43.08; H, 3.75; Cd, 26.78%. umax.(nm)
(m dm3 mol−1 cm−1): 375 (4475), 314 (1125), 269
(8975).
NMR spectra were recorded with a Varian XL-300
and JEOL XL-300 spectrometer (SiMe4 internal stan-
dard) in DMSO (d6), and electronic spectra were
recorded in DMF solution with a Varian DMS 100
UV–Vis spectrometer in the range 200–900 nm. In-
frared spectra were recorded as KBr discs in the range
200–4000 cm−1 using a Pye Unicam SP-300 IR instru-
ment. Microanalyses were carried out by Microanalyti-
cal Service, University of Otago, Dunedin, New
Zealand and zinc, cadmium, manganese, and nickel
were determined volumetrically using EDTA titrations.
Magnetic measurements were carried out by the Gouy
method from room temperature to liquid nitrogen tem-
perature. The apparatus was supplied by Newport In-
struments. The tube was calibrated with [Ni(en)3]S2O3.
2.3.8. [Ni(HSALIMP)2Br2] (VIII)
2.5. Crystallographic data collection and refinement of
the structures
HSALIMP (2.0 mmol), dissolved in dry ethanol (20
ml), was added dropwise to a solution of nickel bro-
mide (1.0 mmol) in the same solvent (10 ml), with
stirring at r.t. After stirring the resulting mixture for
approximately 20 min, a purple coloured solid started
separating and it was stirred further for 2 h. The purple
solid was filtered off, washed with dry ethanol (3×5
ml) and dried under vacuum at 60°C for 8 h. Yield:
66%. Anal. Calc. for [Ni(SALIMP)2Br2] (VIII): C,
48.55; H, 3.73; Ni, 9.13. Found: C, 48.11; H, 3.95; Ni,
9.41%. umax.(nm) (m dm3 mol−1 cm−1): 876 (18), 817
(16), 394 (10975), 269 (21500). veff (300 K)=3.11 BM
and veff (93 K)=3.06 BM.
2.5.1. [Zn(SALIEP)(NO3)]2 (IV)
The crystals of IV are colourless and irregular in
shape. The diffraction intensities of an approximately
0.25×0.25×0.35 mm crystal were collected with
graphite monochromatized Mo Ka radiation using a
Rigaku AFC6S diffractometer at 2691°C and the
ꢀ–2q scan technique to a 2qmax value of 50.1°. A total
of 2862 reflections were measured, of which 2681
(Rint=0.035) were unique and 1826 were considered
significant with Inet\2.0|(Inet). Azimuthal scans of sev-
eral reflections indicated no need for an absorption
correction. The data were corrected for Lorentz and
polarization effects. A correction for secondary extinc-
tion was applied (coefficient=0.19462E-06). The cell
parameters were obtained from the least-squares refine-
ment of setting angles of 24 carefully centered reflections
with 2q in the range 40.12–44.95°.
2.3.9. [Mn(SALIEP)2](ClO4) (IX)
HSALIEP (2.0 mmol), dissolved in dry ethanol (20
ml), was added dropwise to a solution of mangane-
se(III) acetate (1.0 mmol) in the same solvent (10 ml),
with stirring at room temperature. After stirring the
resulting mixture at r.t. for approximately 16 h, sodium
perchlorate (4.0 mm) dissolved in methanol (5 ml) was
added. A deep red solution formed which was left at r.t.
for slow evaporation and after a few hours a reddish
brown crystalline solid separated. It was filtered off,
washed with ethanol (3×5 ml) and methanol (2×1
ml) and dried under vacuum at r.t. for 8 h. Yield: 66%.
Anal. Calc. for [Mn(SALIEP)2](ClO4) (IX): C, 55.40; H,
4.65; N, 9.22; Mn, 9.05. Found: C, 55.52; H, 4.33; N,
9.27; Mn, 8.95%.
The structure was solved by direct methods [4,5]. The
non-hydrogen atoms were refined anisotropically. The
final cycle of full-matrix least-squares refinement was
based on 1826 observed reflections (I\2.00|(I)) and
200 variable parameters and converged with unweighted
and weighted agreement factors of R=SꢀꢀFoꢀ−ꢀFcꢀꢀ/
SꢀFoꢀ=0.034 and Rw=[(Sw(ꢀFoꢀ−ꢀFcꢀ)2/SwFo2)]1/2
=
0.026. The maximum and minimum peaks on the final
difference Fourier map corresponded to 0.27 and
−0.29 e A−3, respectively. Neutral-atom scattering
,
Crystals suitable for X-ray studies were obtained by
the slow evaporation of a solution of the complex in a
mixture of methanol:ethanol (1:1).
factors [6] and anomalous-dispersion terms [7,8] were
taken from the usual sources. All calculations were per-
formed with the TEXSAN [9] crystallographic software
package using a VAX 3100 work station. A summary of
the crystal and other data is given in Table 1 and
selected bond distances and angles are given in Table 2.
Atomic coordinates, anisotropic thermal parameters, a
full listing of bond distances and angles, and a listing of
structure factors are deposited (see Section 5).
2.3.10. [Zn(AMP)2(NO3)2] (X)
X was obtained as a minor product from the filtrate
of I. 2-Aminomethylpyridine found in this complex
could have been produced by the hydrolysis of the
Schiff base ligand HSALIMP.

686
S.S. Tandon et al. / Inorganica Chimica Acta 300–302 (2000) 683–692
Table 1
A summary of crystallographic data for [Zn(SALIEP)(NO3)]2 (IV), [Mn(SALIEP)2](ClO4) (IX) and [Zn(AMP)2(NO3)2] (X)
Compound
IV
IX
X
Chemical formula
Formula weight
Crystal system
Space group
C28H26N6Zn2O8
705.31
monoclinic
P21/c
9.300(5)
18.012(3)
8.699(5)
–
91.46(4)
–
1457(2)
2
C
28H26N4O6ClMn
C12H16N6O6Zn
405.67
monoclinic
P21/c
8.834(2)
8.864(4)
10.188(2)
–
101.36(2)
–
782.1(4)
2
604.93
triclinic
P1
(
,
a (A)
11.406(5)
13.081(4)
11.312(5)
101.37(3)
110.10(4)
111.33(2)
1373(1)
2
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
3
,
V (A )
Z
2qmax (°)
T (K)
50.1
299
50.1
299
50.1
299
,
u (A) (Mo Ka)
0.71069
1.608
17.45
0.034
0.026
0.71069
1.464
6.07
0.059
0.066
0.71069
1.722
16.50
0.026
0.025
Dcalc. (g cm−3
)
v (cm−1
)
a
R
Rw
b
Max. shift/l
F(000)
0.00
720
0.00
624
0.00
416
GOF
1.63
2.76
2.03
Crystal size (mm)
0.25×0.25×0.35
0.35×0.20×0.20
0.35×0.25×0.20
a R=S(ꢀFoꢀ−ꢀFcꢀ)/SꢀFoꢀ.
b Rw=[(Sw(ꢀFoꢀ−ꢀFcꢀ)2/SwFo2)]1/2
.
2.5.2. [Mn(SALIEP)2](ClO4) (IX), [Zn(AMP)2](NO3)2
(X)
Data collection and structure solutions for IX and X
were carried out in a similar manner. Summaries of
crystal and other data are given in Table 1. Selected
bond distances and angles are given in Tables 3 and 4,
respectively. Atomic coordinates, anisotropic thermal
parameters, a full listing of bond distances and angles,
and a listing of structure factors are deposited (see
Section 5).
Table 2
,
Bond distances (A) and angles (°) relevant to the zinc coordination sphere in [Zn(SALIEP)(NO3)]2 (IV)
a
ADC
ADC a
Zn(1)ꢀO(1)
Zn(1)ꢀO(2)
Zn(1)ꢀN(2)
1.994(2)
2.051(3)
2.096(3)
1
1
1
Zn(1)ꢀO(1)
Zn(1)ꢀN(1)
Zn(1)ꢀZn(1)*
2.103(2)
2.087(3)
3.184(1)
3
1
3
O(1)ꢀZn(1)ꢀO(1)
O(1)ꢀZn(1)ꢀN(1)
O(1)ꢀZn(1)ꢀO(2)
78.01(9)
91.6(1)
94.75(9)
O(1)ꢀZn(1)ꢀO(2)
O(1)ꢀZn(1)ꢀN(2)
O(1)ꢀZn(1)ꢀN(1)
129.8(1)
116.8(1)
167.5(1)
a Atom designate code (from ORTEP).
Table 3
,
Bond lengths (A) and angles (°) relevant to the manganese coordination spheres in [Mn(SALIEP)2](ClO4) (IX)
a
ADC
ADC a
Mn(1)ꢀO(1)
Mn(1)ꢀN(1)
Mn(1)ꢀN(2)
1.884(3)
2.019(4)
2.368(4)
1
1
1
Mn(2)ꢀO(2)
Mn(2)ꢀN(3)
Mn(2)ꢀN(4)
1.874(4)
2.021(4)
2.383(4)
1
1
1
O(1)ꢀMn(1)ꢀO(1)
N(1)ꢀMn(1)ꢀN(2)
N(1)ꢀMn(1)ꢀN(2)
180.00
82.1(2)
97.9(2)
O(2)ꢀMn(2)ꢀO(2)
N(3)ꢀMn(2)ꢀN(4)
N(3)ꢀMn(2)ꢀN(4)
180.00
81.3(2)
98.7(2)
a Atom designate code (from ORTEP).

S.S. Tandon et al. / Inorganica Chimica Acta 300–302 (2000) 683–692
687
Table 4
,
Bond lengths (A) and angles (°) relevant to the zinc coordination sphere in [Zn(AMP)2(NO3)2] (X)
a
ADC
ADC a
Zn(1)ꢀO(1)
Zn(1)ꢀN(2)
2.317(2)
2.071(2)
1
1
Zn(1)ꢀN(1)
2.140(2)
1
O(1)ꢀZn(1)ꢀO(1)
O(1)ꢀZn(1)ꢀN(1)
O(1)ꢀZn(1)ꢀN(2)
O(1)ꢀZn(1)ꢀN(1)
O(1)ꢀZn(1)ꢀN(2)
N(1)ꢀZn(1)ꢀN(2)
N(1)ꢀZn(1)ꢀN(2)
N(2)ꢀZn(1)ꢀN(2)
180.00
O(1)ꢀZn(1)ꢀN(1)
O(1)ꢀZn(1)ꢀN(2)
O(1)ꢀZn(1)ꢀN(1)
O(1)ꢀZn(1)ꢀN(2)
N(1)ꢀZn(1)ꢀN(1)
N(1)ꢀZn(1)ꢀN(2)
N(1)ꢀZn(1)ꢀN(2)
89.19(7)
94.34(7)
90.81(7)
85.66(7)
180.00
90.81(7)
85.66(7)
89.19(7)
94.34(7)
79.60(7)
100.40(7)
180.00
100.40(7)
79.60(7)
a Atom designate code (from ORTEP).
3. Results and discussion
a six-coordinate octahedral complex [Ni(SALIMP)2Br2]
(VIII) of 1:2 metal:ligand stoichiometry takes place.
HSALIEP, which has one additional carbon atom in
the chain, and is capable of forming two adjacent six
membered chelate rings, reacts with zinc(II) and Cd(II)
ions to form dimeric 1:1 complexes (IV–VII) and with
manganese(III) ion to form a monomeric 1:2 complex
[Mn(SALIEP)2](ClO4) (IX). In all these complexes,
HSALIEP acts as a deprotonated, tridentate ligand
irrespective of the nature of the anions, as has been
seen with the corresponding saturated analogues. The
difference in the coordination abilities of the two Schiff
base ligands HSALIMP and HSALIEP could be at-
tributed to the difference in the chelate ring sizes which
are formed on coordination.
3.1. Synthesis of the complexes
Two Schiff bases 2-[[(2-pyridinylmethyl)imino]-
methyl]phenol (HSALIMP) and 2-[[[2-(2-pyridinyl)-
ethyl]imino]methyl]phenol (HSALIEP), which are
potentially tridentate (N2O) ligands, capable of forming
two adjacent (6,5) and (6,6) membered chelate rings
respectively on coordination with the same metal ion
have been produced from 1+1 condensation of
salicylaldehyde with 2-aminomethylpyridine and 2-(2-
aminoethyl)pyridine respectively. HSALIMP and
HSALIEP are unstable and were used immediately to
avoid noticeable degradation as evidenced by the isola-
tion of [Zn(AMP)2(NO3)2], (AMP=2-aminomethyl
pyridine) as a minor product from the filtrate of com-
plex I, where AMP is presumed to have been produced
from the hydrolysis of HSALIMP. The coordination
behaviour of HSALIMP, which has one carbon less
than that of (HSALIEP), differs from the latter towards
zinc(II) ion as has already been observed in case of
zinc(II) and cadmium(II) complexes with the reduced
Schiff base ligands [3]. Reactions between HSALIMP
and zinc(II) salts produce two types of complex: (a)
dimeric 1:1 complexes, [Zn(SALIMP)X]2·yH2O (X=
NO3, y=0 (I); X=I, y=3 (II), in which SALIMP acts
as a tridentate (N2O) ligand and the deprotonated
phenolate group links the two zinc(II) ions and the two
halves of the dimer, as in case of (IV); and (b) a 1:1
monomeric complex, [Zn(HSALIMP)Cl2]·2H2O (III), in
which HSALIMP acts as a bidentate (NN) ligand with
no deprotonation of the phenolate oxygen, which re-
mains uncoordinated, as was observed in the case of
[Cu(HSALAMP)Cl2]·C2H5OH [1]. The formation of the
compounds of type a, or b depends on the nature of the
anion. With nitrate and iodide anions, having moderate
to weak coordinating ability, complexes of type a are
3.1.1. Description of the structures of
[Zn(SALIEP)(NO3)]2 (IV), [Mn(SALIEP)2](ClO4) (IX)
and [Zn(AMP)2(NO3)2] (X)
The structure of IV is very similar to the structures of
[Zn(SALAMP)(NO3)]2 and [Cd(SALAEP)(NO3)]2 with
the reduced ligands [3] with the only difference that in
IV nitrate is acting as a monodentate ligand as against
bidentate in the other complexes (Fig. 1). A perspective
view of [Zn(SALIEP)(NO3)]2 (IV) is shown in Fig. 2,
and selected bond distances and angles relevant to the
zinc coordination sphere are given in Table 2. The
structure consists of a centrosymmetric dimer (Fig. 2),
comprising two zinc(II) ions, two monodentate nitrate
anions and two tridentate SALIEP ligands bonded by
the pyridine nitrogen, the imine nitrogen and the phe-
nolate oxygen (N,N,O) atoms of SALIEP. The depro-
tonated phenolate bridges the two zinc atoms and links
the two halves of the dimer together. The geometry
about the five-coordinate zinc atom can best be de-
scribed as slightly distorted trigonal bipyramidal, with
equatorial angles in the range 113–130°, and an axial
angle (O(1)ꢀZn(1)ꢀN(1)) of 167.5°. The O(1) bridge
forms an asymmetric linkage to the zinc atoms with
markedly different zinc-oxygen distances (Zn(1)ꢀO(1)
formed whereas with chloride as anion the type b
complex is formed. With nickel(II) ion the formation of
6

688
S.S. Tandon et al. / Inorganica Chimica Acta 300–302 (2000) 683–692
Mn1, N1, N2, N1* and N2* are nearly coplanar and
the bond angles within the ‘plane’ are significantly
distorted from those of a regular octahedron with
N(1)ꢀMn(1)ꢀN2=97.9 (2)° and N(1)ꢀMn(1)ꢀN*(2)=
82.1(2)°. The angles O(1)ꢀMn(1)ꢀO(1*) (180.0°),
N(1)ꢀMn(1)ꢀN*(1) (180.00°), and N(2)ꢀMn(1)ꢀN*(2)
(180.00°) are linear however. The Mn atom resides in
the N4 plane (angle sum 360°). The Mn(1)ꢀO(1) dis-
,
tance of 1.884 A is much shorter than the metal oxygen
distance found in IV and other zinc(II) and cadmiu-
m(II) complexes of the reduced ligands [3], and can be
attributed to the higher metal oxidation state. However
the manganeseꢀimino nitrogen bond distance of
Fig. 1. HSALIMP and HSALIEP ligands.
,
MnꢀN(1) (2.019 A) is similar to that observed for
,
zinc(II) complex (IV) but the Mn(1)ꢀN(2) (2.368 (4) A)
(pyridine) distance is surprisingly much longer than the
comparable distance observed for complex IV. The
perchlorate group is disordered and is uncoordinated.
The structure of [Zn(AMP)2(NO3)2] (X) is shown in
Fig. 4 and bond distances and angles relevant to the
zinc coordination sphere are given in Table 4. The
molecule is centrosymmetric with the center of inver-
sion at the zinc atom. The coordination around the
pseudo-octahedral zinc atom (N4O2) consists of two
Fig. 2. Perspective view of [Zn(SALIEP)(NO3)]2 (IV).
,
,
1.994 A and O(1)*ꢀZn(1) 2.103 A). The Zn(1)ꢀZn(1)*
,
separation of 3.184 (1) A is significantly longer than
that observed in the analogous zinc(II) complex of the
reduced Schiff base ligand [Zn(SALAMP)(NO3)]2
,
(ZnꢀZn=3.063 A). The nitrate group, acts as a
monodentate ligand with a ZnꢀO distance (Zn(1)ꢀO(2))
,
of 2.051 A, typical for monodentate nitrate. The
zincꢀnitrogen and zincꢀoxygen bond distances of
,
Zn(1)ꢀN(2)=2.096 (pyridine), Zn(1)ꢀN(1)=2.087 A
(imino) and Zn(1)ꢀO(1)=1.994, and Zn(1)ꢀO1*=
Fig. 3. Perspective view of [Mn(SALIEP)2](ClO4) (IX).
,
2.103 A are considered normal, but significantly differ-
ent from those observed for the analogous zinc(II) and
cadmium(II) complexes with reduced ligands [3].
The structure of the cation in [Mn(SALIEP)2](ClO4)
(IX) is shown in Fig. 3 and bond distances and angles
relevant to the manganese coordination sphere are
given in Table 3. Two slightly different molecules each
with inversion symmetry are present in the unit cell.
The structure consists of a centrosymmetric molecule
with the center of symmetry at the manganese atom.
The coordination sphere about the manganese atom
consists of two phenolate oxygens, two pyridine nitro-
gens and two imino nitrogen atoms (N4O2) from two
deprotonated SALIEP ligands. Each SALIEP acts as a
tridentate ligand via a phenolate oxygen, and pyridine
and imino nitrogen atoms. The geometry about the
manganese atom is close to regular octahedral. The
Fig. 4. Perspective view of [Zn(AMP)2(NO3)] (X).

S.S. Tandon et al. / Inorganica Chimica Acta 300–302 (2000) 683–692
689
pyridine nitrogens, two amino nitrogens, and two oxy-
gen atoms from two monodentate nitrate anions. The
Zn, N1, N2, N1* and N2* atoms are coplanar and the
bond angles within the ‘plane’ vary significantly from
each other and from those of a regular octahedron with
ligand to the zinc(II) ion through imino nitrogen. The
signals due to the pyridine hydrogens show minor to
significant shifts (0.01–0.02 (H1), 0.14–0.26 (H2),
0.15–0.29 (H3) and 0.10–0.22 ppm (H4)) in their posi-
tions from those in the free ligand indicating the partic-
ipation of the pyridine nitrogen in coordination with
the metal ion. The phenyl hydrogens also show signifi-
cant shifts (0.17 (H9), 0.27–0.32 (H10), 0.08–0.10
(H11) and 0.16–0.17 ppm (H12)) in their positions
from those in the free ligand suggesting the involvement
of phenolate oxygen in coordination with the metal ion
(I and II) thus supporting the conclusions drawn from
analytical and other spectroscopic data.
N(1)ꢀZnꢀN2=79.60(7)°
and
N(1)ꢀZnꢀN*(2)=
100.60(2)°. Other bond angles are close to those ex-
pected for regular octahedral geometry.
3.2. Spectroscopic properties
All the complexes display an absorption at 1617–
1645 cm−1 which is assigned to the CꢁN stretch of the
coordinated Schiff base ligands [10]. Strong well re-
solved-sharp bands in the regions 1597–1605, 1460–
1485, 1420–1445, 1040–1055 and 1005–1015 cm−1 are
assigned to the coordinated pyridine ring [11]. The
mode of the coordination of the nitrate group can be
determined by infrared spectroscopy, in a region of the
spectrum where combination (w1+w3) bands occur for
coordinated nitrate [12]. In compounds I, IV and X the
single absorption band at 1736–1739 cm−1, is associ-
ated with the monodentate nitrate in agreement with
the structural data for IV and X, which suggests that
compound I has dimeric structure analogous to IV. The
perchlorate w3 band in IX appears at 1084 cm−1 indi-
cating the presence of uncoordinated perchlorate group
in agreement with the X-ray crystal structure of IX.
The electronic spectra of compounds I–VII are char-
acterized by the presence of two to three high energy
transitions which can be assigned to charge transfer
from the ligand to the metal and vice versa. The
transitions of very strong intensity at 367–394 nm and
266–269 nm, have been attributed to the charge trans-
fer from the pyridine and imino nitrogens to the metal
centers [1].
1
Compounds IV, V and VII exhibit very similar H
NMR spectra (Table 5), which differ markedly from
that of VI. In compounds IV, V and VII the hydrogens
of the methylene group (H7) and the enamine hydrogen
(H8) which are present adjacent to the imino group
show significant shifts (0.08–0.17 (H7), 0.15–0.42 (H8)
in their positions compared with the free ligand, and
are clearly influenced by proximity of the coordinated
metal ions. H6 and the hydrogens of the pyridine and
phenyl rings also show small to significant changes in
their positions indicating the coordination of the
SALIEP ligand and the retention of the structures in
DMSO solutions.
In the 13C NMR spectra of the compounds I–VII,
the signal due carbon atoms adjacent to the donor sites
show very significant changes in their positions as com-
pared with the free Schiff base ligands (Table 6) clearly
indicating the coordination of the ligands through these
donor sites and the retention of their structures in the
DMSO solutions. In compounds I–III the signal due to
C6 which is adjacent to the imino nitrogen shows a
drastic upfield shift (20.98–21.17 ppm), whereas the
signal due to C7 shows a relatively small downfield shift
(1.71–2.31 ppm) from their positions in the free ligand,
thus demonstrating the participation of the imino nitro-
gen in coordination with the zinc(II) ions. The signals
due to carbon atoms C1 and C5 which are adjacent to
the pyridine nitrogen also show small (1.02–1.47 ppm
(C1)) to significant upfield shifts (4.17–4.66 ppm (C5))
from their positions in the free ligand, indicating the
participation of pyridine N in coordination to the
zinc(II) ion. In compounds I and II the carbon atom
C13, to which the phenolate oxygen is linked, shows a
very large downfield shift (34.1–34.14 ppm) from its
position in the free ligand showing the participation of
phenolate oxygen in coordination with the zinc(II) ion.
The signal due to C13 in compound III could not be
detected. This may be indicative of nonparticipation of
a protonated phenolate oxygen in coordination and a
monomeric structure for III. The signals due to other
carbon atoms also show small to significant variations
from their positions in the free ligand establishing the
coordination of the ligands to the metal ions and the
retention of the structures in the solutions.
1H, 13C and 2D NMR spectroscopy has been used to
extract information regarding the mode of coordination
of the ligands with the metal ions. The assignments in
proton and 13C NMR spectra have been made on the
basis of hetcore and cosy experiments and comparison
of these data with those of the free, freshly isolated
Schiff base ligands HSALIMP and HSALIEP and the
dimeric zinc(II) complex (IV), for which the single
1
crystal X-ray structure has been determined. H NMR
spectra of compounds I and II are very similar but are
slightly different from that of III (Table 5), pointing to
the fact that the structures of I and II are similar but
different from that of III. In compounds I–III, the
hydrogens of the methylene group (H6) (Fig. 1) adja-
cent to the imino nitrogen of SALIMP, form a singlet
and show a downfield shift (0.13 ppm (I, II), 0.05 ppm
(III)) in its position from that in the free ligand and the
singlet due to H7 (Fig. 1) shows an upfield shift (0.05–
0.10 ppm) (Table 5) compared to its position in the free
ligand, reflecting the coordination of the HSALIMP

690
S.S. Tandon et al. / Inorganica Chimica Acta 300–302 (2000) 683–692
Table 5
1H NMR spectral data with assignments
a
Complex
l(ppm) (DMSO)(d6)
H(SALIMP)
5.01 (2H, s, H6); 7.0 (1H, d, J=7.5 Hz, H12); 7.01 (1H, t, J=7.5 Hz, H10); 7.39 (1H, t, J=6.0 Hz,
H2); 7.44 (1H, t, J=8.1 Hz, H11); 7.49 (1H, d, J=7.8 Hz, H4); 7.59 (1H, d, J=7.2 Hz, H9); 7.88
(1H, t, J=7.8 Hz, H3); 8.65 (1H, d, J=4.2 Hz, H1); 8.83 (1H, s, H7).
H(SALIEP)
3.19 (2H, t, J=6.9 Hz, H6); 4.08 (2H, t, J=6.9 Hz, H7); 6.93–6.98 (2H, m, H11 & H13); 7.29 (1H,
d, J=7.5 Hz, H2); 7.36–7.42 (2H, m, H4 & H12); 7.46 (1H, d, J=8.1 Hz, H10); 7.78 (1H, t, J=7.5
Hz, H3); 8.59 (1H, s, H8); 8.62 (1H, d, J=4.5 Hz,H1).
[Zn(SALIMP)(NO3)]2 (I)
[Zn(SALIMP)I]2·3H2O (II)
[Zn(HSALIMP)Cl2]·H2O (III)
[Zn(SALIEP)(NO3)]2 (IV)
[Zn(SALIEP)Cl)]2·2H2O (V)
5.14 (2H, s, H6); 6.69 (1H, t, J=5.4 Hz, H10); 6.84 (1H, d, J=8.4 Hz, H12); 7.36 (1H, t, J=7.8 Hz,
H11); 7.42 (1H, d, J=7.5 Hz, H9); 7.65 (1H, t, J=6.3 Hz, H2); 7.71 (1H, d, J=8.1 Hz, H4); 8.17
(1H, t, J=7.8 Hz, H3); 8.67 (1H, d, J=5.1 Hz, H1); 8.77 (1H, s, H7).
5.14 (2H, s, H6); 6.69 (1H, t, J=7.0 Hz, H10); 6.83 (1H, d, J=8.7 Hz, H12); 7.35 (1H, t, J=6.9 Hz,
H11); 7.42 (1H, d, J=7.5 Hz, H9); 7.63 (1H, t, J=8.4 Hz, H2); 7.69 (1H, d, J=7.8 Hz, H4); 8.14
(1H, t, J=6.9 Hz, H3); 8.67 (1H, d, J=4.8 Hz, H1); 8.78 (1H, s, H7).
5.06 (2H, s, H6); 6.74 (1H, t, J=7.2 Hz, H10); 6.83 (1H, d, J=8.1 Hz, H12); 7.34 (1H, t, J=7.8 Hz,
H11); 7.42 (1H, d, J=7.5 Hz, H9); 7.53 (1H, t, J=6.0 Hz, H2); 7.59 (1H, d, J=7.5 Hz, H4); 8.03
(1H, t, J=7.8 Hz,H3); 8.66 (1H, d, J=4.5 Hz, H1); 8.73 (1H, s, H7).
3.33 (2H, t, J=4.5 Hz, H6); 3.95 (2H, t, J=4.5 Hz, H7); 6.59 (1H, t, J=7.2 Hz, H11); 6.76 (1H, d,
J=8.7 Hz, H13); 7.29–7.34 (2H, m, H10 & H12); 7.60 (1H, t, J=6.0 Hz, H2); 7.62 (1H, d, J=6.9
Hz, H4); 8.08 (1H, t, J=7.5 Hz, H3); 8.44 (1H, s, H8; 8.81 (1H, d, J=5.0 Hz, H1).
3.38 (2H, t, J=6.9 Hz, H6); 4.00 (2H, t, J=6.9 Hz, H7); 6.52 (1H, t, J=7.5 Hz, H11); 6.66 (1H, d,
J=8.4 Hz, H13); 7.14 (1H, d, J=8.1 Hz, H10); 7.26 (1H, t, J=6.6 Hz, H12); 7.39 (1H, t, J=9.0
Hz, H2); 7.46 (1H, d, J=8.1 Hz, H4); 7.85 (1H, t, J=8.1 Hz, H3); 8.17 (1H, s, H8); 8.69 (1H, d,
J=4.5 Hz, H1).
[Zn(SALIEP)I]2·H2O (VI)
2.60 (2H, t, J=1.8 Hz, H6); 4.04 (2H, bs, H7); 6.87 (2H, bs, H11 & H13); 7.36–7.50 (4H, m, H2, H4,
H10, H12); 7.90 (1H, bs, H1); 8.60 (1H, t, J=3.9 Hz, H3); 8.69 (1H, s, H8).
[Cd(SALAEP)(NO3)]2·C2H5OH
3.30 (2H, t, J=4.8 Hz, H6); 3.91 (2H, t, J=4.8 Hz, H7); 6.48 (1H, t, J=6.9 Hz, H11); 6.59(1H,
(VII) d, J=8.4 Hz, H13); 7.18–7.22 (2H, m, H10 & H12); 7.55–7.61 (2H, m, H2 & H4); 8.04 ( 1H, t,
J=7.2 Hz, H3); 8.32 (1H, s, H8); 8.57 (1H, bs, H1).
a Compounds: I is light brown, II–IV, VI, VII are very pale yellow, V is yellow and VIII is purple. s=singlet, d=doublet, bs=broad singlet,
t=triplet, m=multiplet.
The 13C NMR spectra of compounds IV, V and VII
these sites to the metal ions and pointing to the fact
are very similar (Table 6) and the signals due to carbon
atoms C1, C5, C7, C8 and C14 present in the vicinity of
donor sites show minor to significant changes (0.00–
0.66 (C1), 0.04–0.55 (C5), 0.23–1.6 (C7), 3.95–4.21
(C8) and 11.49–32.89 (C14) ppm) in their positions
from the free ligand indicating the coordination of
that the compounds V and VII have dimeric structures
similar to IV. The signals due to the carbon atoms C1,
C5 and C7 show only minor changes (0.00–1.6 ppm)
in their positions as compared with much larger
changes in corresponding zinc(II) complexes with the
HSALIMP ligand. This has been attributed to more
Table 6
13C NMR spectral data (l (PPM), DMSO (d6) with assignments
I
II
III
IV
V
VI
VII
SALIMP
SALIEP
IC1
C2
C3
C4
C5
C6
C7
C8
C9
C10
C11
C12
C13
C14
147.98
123.75
139.54
123.20
155.99
42.96
169.65
118.62
134.38
119.68
134.72
117.47
191.96
147.85
123.64
139.54
123.04
155.95
42.77
169.76
118.92
133.82
119.63
134.95
117.32
191.99
148.30
123.29
138.78
122.68
156.44
42.87
169.16
118.93
133.42
119.63
134.19
117.36
149.82
122.82
139.83
125.15
160.67
35.70
149.30
121.86
149.13
123.58
137.08
124.35
149.70
123.55
139.64
125.21
161.28
36.93
149.32
122.53
137.02
122.13
160.61
63.94
167.45
118.80
131.85
118.69
132.55
116.54
157.85
149.16
121.51
136.38
123.38
160.73
38.74
124.09
34.26
57.64
58.10
58.60
169.94
118.46
133.76
112.81
135.63
122.31
59.47
57.87
170.04
118.45
133.82
112.95
135.62
122.24
170.52
170.20
119.27
132.88
111.98
136.46
122.84
172.17
165.99
118.60
131.58
118.41
132.21
116.49
159.03
119.60
133.36
117.31
136.55
122.20
191.92

S.S. Tandon et al. / Inorganica Chimica Acta 300–302 (2000) 683–692
691
4. Conclusion
strained structures in complexes with HSALIMP lig-
and, because of the formation of a five-membered
chelate ring in comparison with the formation of a
six-membered chelate ring, leading to less strained
structures. The signals due to C8 and C14 show signifi-
cant to very large upfield shifts (3.95–4.21 ppm (C8),
11.49–32.89 ppm (C14)) in their positions from those
of the free ligand clearly establishing the participation
of imino nitrogen and phenolate oxygen to the metal
Zinc(II) ions react with SALIMP to form two types
of compounds: (a) dimeric, five-coordinate compounds
(I and II) involving an anion and a tridentate ligand
with deprotonated phenolate oxygen, which bridges the
two metal centers and links the two halves of the dimer,
as in the case of IV and (b) a four-coordinate
monomeric complex III involving two coordinated
chloride ions and a bidentate (N2) SALIMP ligand, in
which the phenolate oxygen remains protonated and
uncoordinated. SALIEP reacts with zinc(II) and cadmi-
um(II) ions to form dimeric 1:1 compounds IV–VII in
which SALIEP behaves as tridentate ligand (N2O) with
a deprotonated phenolate oxygen, which bridges two
metal centers, and links the two halves of the dimer as
determined by crystallographically in case of IV. On
reaction with nickel(II) and manganese(III) ions,
HSALIEP forms six-coordinate octahedral complexes
VIII and IX with 1:2 metal:ligand stoichiometry.
1
ions. H and 13C NMR spectra of compound VI are
some what different from those of other three com-
pounds with SALIEP which could be attributed either
to dissociation of the compound in DMSO or a struc-
1
ture different from other three. From the H and 13C
NMR spectral data, compounds I, II, IV, V and VII,
which have very similar structural features, have been
assigned dimeric structures, similar to that of IV, which
has been determined from X-ray crystallography. In
this structure the deprotonated phenolate oxygen links
the two metal centers and the two halves of the dimer.
In compound III, in which the phenolate oxygen of the
HSALIMP remains protonated and uncoordinated, the
ligand seems to coordinate to the zinc(II) ion through
the two nitrogen donors, resulting in the formation of a
single five-membered chelate ring in a four coordinate
arrangement. A similar situation was observed in the
zinc(II) and copper(II) complexes of reduced Schiff
base ligand HSALAMP [1,3].
5. Supplementary material
Tables of atomic coordinates, a complete listing of
bond lengths and bond angles, anisotropic thermal
parameters and calculated and observed structure fac-
tors have been deposited. Copies of this information
may be obtained free of charge from The Director,
CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK
(fax: +44-1223-336-033; e-mail: deposit@ccdc.cam.
ac.uk or www: http://www.ccdc.cam.ac.uk).
The magnetic moment measurements on a powdered
sample of compound VIII were carried out in the
temperature range 300–93 K. The magnetic moment of
3.11 BM at 300 K which remains nearly unchanged
(3.06 BM at 93 K) down to 93 K is consistent with a
six-coordinate octahedral geometry around the nickel
ion and a mononuclear structure [13]. The electronic
spectrum of VIII in DMF solution can be interpreted in
terms of a distorted octahedral stereochemistry around
Acknowledgements
We thank Dr J.N. Bridson and D.O. Miller, Memo-
rial University of Newfoundland, St. John’s, NF,
Canada for X-ray structures. Support for this project
from the University Grants Commission of India, New
Delhi, and Guru Nanak Dev University Amritsar, Pun-
jab, India and the Natural Science and Engineering
3
the nickel center. The A2g“3T2g transition in VIII
appears as a doublet at 876 and 817 nm, with the
splitting most likely caused by a distortion from regular
3
octahedral geometry. The transition due to A2g“3T1g
(F) could not be observed. A strong band at 394 nm
Research
Council
of
Canada
is
gratefully
(m=10975 dm3 mol−1 cm−1) is assigned to a combina-
acknowledged.
3
tion of A2g“3T1g (P) and charge transfer transitions
[14,15]. A very strong band at 269 nm (m=21500 dm3
mol−1 cm−1), which appears nearly at the same posi-
tion (266–269 nm) in Zn(II) and Cd(II) complexes of
SALIMP and SALIEP ligands, is ascribed to a charge
transfer transition. Thus, the electronic spectrum and
magnetic data are indicative of a distorted octahedral
stereochemistry for VIII, in which each HSALIMP acts
as a bidentate ligand through imino and pyridine nitro-
gens and it seems reasonable to assume that the two
axial positions are occupied by bromine atoms.
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