Complexation behaviour of hexadentate ligands possessing N 2O4 and N2O2S2 cores: Differential reactivity towards Co(II), Ni(II) and Zn(II) salts and structures of the products

Article abstract of DOI:10.1039/b305313j

Reactions of divalent metal salts of Co, Ni and Zn with 1,2-di(salicylaldimino-o-phenylthio)ethane (H₂L¹) and 1,2-di(naphthaldimino-o-phenylthio)ethane (H₂L²), having N₂O₂S₂ cores, and 1,2-di(O-salicylaldimino-o- hydroxyphenyl)ethane (H₂L³), having a N₂O ₄ core, have been explored. Out of the three ligands and the nine products obtained from the corresponding reactions, two ligands and seven products were crystallographically characterized. However, all the ligands and the products were characterized by analytical and spectral methods. Reaction of H₂L¹ and H₂L² with Co(II) salts results in oxidative cleavage of the C-S bond to produce a CO(III) product bound to two dissimilar tridentate ligands formed as a result of the cleavage. The reaction of H₂L¹ and H₂L² with Co(III)acac in the presence of methanolic NaOH also shows cleavage of the C-S bond to give compounds similar to those obtained by reacting H₂L ¹ and H₂L² with Co(II) salts in the absence of additional external base. However, the reaction of Co(II) salt with H ₂L³ did not lead to any C-O bond cleavage; rather it produced an octahedral CO(II) complex of the hexadentate H₂L ³. Reactions of all these three ligands with Ni(II) salt resulted in octahedral complexes of the corresponding hexadentate ligands. In the case of Zn(II), while H₂L³ with a N₂O₄ core resulted in an octahedral complex, H₂L¹ and H ₂L², both with a N₂O₂S₂ core, produced pseudo-octahedral complexes whose Zn-S bond lengths are rather long. The conformations of both the 5-membered and 6-membered chelate rings formed in the products were evaluated. The extent of distortion exhibited in the geometry of these octahedral complexes was computed and appropriately compared.

Full text of DOI:10.1039/b305313j

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P A P E R
Complexation behaviour of hexadentate ligands possessing N2O4 and
N2O2S2 cores: differential reactivity towards Co(II), Ni(II) and
Zn(II) salts and structures of the products
Gudneppanavar Rajsekhar,a Chebrolu P. Rao,*a Pauli Saarenketo,b
b
b
¨
Kalle Nattinen and Kari Rissanen
a
Bioinorganic Laboratory, Department of Chemistry, Indian Institute of Technology Bombay,
Mumbai 400 076, India. E-mail: cprao@chem.iitb.ac.in
Department of Chemistry, University of Jyvaskyla, Jyvaskyla SF - 40351, Finland
b
Received (in Montpellier, France) 8th May 2003, Accepted 9th September 2003
First published as an Advance Article on the web 30th October 2003
Reactions of divalent metal salts of Co, Ni and Zn with 1,2-di(salicylaldimino-o-phenylthio)ethane (H2L1)
and 1,2-di(naphthaldimino-o-phenylthio)ethane (H2L2), having N2O2S2 cores, and 1,2-di(O-salicylaldimino-
o-hydroxyphenyl)ethane (H2L3), having a N2O4 core, have been explored. Out of the three ligands and the nine
products obtained from the corresponding reactions, two ligands and seven products were crystallographically
characterized. However, all the ligands and the products were characterized by analytical and spectral methods.
Reaction of H2L1 and H2L2 with Co(II) salts results in oxidative cleavage of the C–S bond to produce a Co(III)
product bound to two dissimilar tridentate ligands formed as a result of the cleavage. The reaction of H2L1 and
H2L2 with Co(III)acac in the presence of methanolic NaOH also shows cleavage of the C–S bond to give
compounds similar to those obtained by reacting H2L1 and H2L2 with Co(II) salts in the absence of additional
external base. However, the reaction of Co(II) salt with H2L3 did not lead to any C–O bond cleavage; rather it
produced an octahedral Co(II) complex of the hexadentate H2L3. Reactions of all these three ligands with Ni(II)
salt resulted in octahedral complexes of the corresponding hexadentate ligands. In the case of Zn(II), while H2L3
with a N2O4 core resulted in an octahedral complex, H2L1 and H2L2, both with a N2O2S2 core, produced
pseudo-octahedral complexes whose Zn–S bond lengths are rather long. The conformations of both the
5-membered and 6-membered chelate rings formed in the products were evaluated. The extent of distortion
exhibited in the geometry of these octahedral complexes was computed and appropriately compared.
studying their reactivity and coordination chemistry using
Introduction
three divalent metal ions, viz., Co(II), Ni(II) and Zn(II) and four
different Co(II) salts as well as one acetylacetonate (acac) com-
pound of Co(III). In the process, the reaction product in each
case was isolated, purified and characterized. Structures of
several of these products, including the precursor ligands, were
established by single crystal X-ray diffraction (XRD). The
results of all these studies are reported in this paper in a
comparative way.
Molecules possessing O, N and S donor sites are important in
the development of coordination chemistry as well as in the
bio-mimetic chemistry of a number of metal ions, particularly
the transition metals. Among these, non-cyclic hexadentate
ligands with N2O4 and N2O2S2 binding cores are well-suited
for the coordination of transition metal ions with a high pre-
ference towards the later ones.1 A non-cyclic ligand of the
N2O2S2 type, 1,2-di(salicylaldimino-o-phenylthio)ethane (H2L1),
generated interesting chemistry with oxidative cleavage of
the ligand when it was reacted with a Co(II) salt, rather than
Results and discussion
forming
a
simple complex.2 However, an earlier work
All the compounds reported in Scheme 1, except those of Ni(II)
(2, 5 and 8), were characterized by 1H and 13C NMR and
all were characterized by FAB-MS, UV-Vis and magnetic
moment measurements. Except for H2L2, 4 and 2, all other
ligands and complexes were structurally characterized by
single crystal XRD.
reported the formation of only a simple cobalt complex from
the same reaction but the product was not subjected to
NMR or X-ray studies.3 C–S bond cleavage is not an unusual
phenomenon, particularly with cobalt group elements in the
presence of cyclic thioether ligands as well as with some non-
cyclic ones,4 but this is not the case for the ligands in this
paper. In the literature,4 the suitable size for the cleavage of
thia-chelates was addressed and in such cases the C–H bond
is activated by a base, such as Et3N or NaOH/KOH. The pre-
sent study differs even in this context. All these points aroused
great interest in our group to understand what happens to the
cleavage reaction when (a) the sulfur is replaced by oxygen, (b)
Co(II) is replaced by Ni(II) or Zn(II), (c) the counter ion of the
Co(II) salt is varied and (d) Co(II) is replaced by a Co(III) salt.
These aspects were addressed in a systematic manner by devel-
oping three types of hexadentate ligands (H2L1, H2L2 and
H2L3), having either an N2O4 core or an N2O2S2 core, and
1. Reactions of H2L1–H2L3 with Co(II)
While the reaction of Co(II) salts (acetate, chloride, sulfate and
acetylacetonate) with H2L1 or H2L2 having an N2O2S2 core
results in the oxidative cleavage of the C–S bond, the reaction
of H2L3 having an N2O4 core produces only a simple Co(II)
complex.
C–S bond cleavage with H2L1 and H2L2. The reactions
of H2L1 or H2L2 with Co(acetate)2ꢀ4H2O in a 1:1 ratio in
T h i s j o u r n a l i s Q T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 4
N e w . J . C h e m . , 2 0 0 4 , 2 8 , 7 5 – 8 4
75

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Scheme 1 Schematic representation of the synthesis of the ligands and their Co(III), Co(II), Ni(II) and Zn(II) complexes. (i) Dry ethanol and Na;
(ii) aqueous NaOH; (iii) MeOH, RT, stirring; (iv) MeOH, RT, stirring; (v) EtOH, reflux for 6 h; (vi) Co(OAc)2ꢀ4H2O, argon/Co(acac)3/NaOH;
(vii) oxygen; (viii) Ni(OAc)2ꢀ4H2O/Zn(OAc)2ꢀ2H2O; (ix) Co(OAc)2ꢀ4H2O, argon, oxygen/Co(acac)3 , NaOH; (x) Ni(OAc)2ꢀ4H2O/
Zn(OAc)2ꢀ2H2O; (xi) Co(OAc)2ꢀ4H2O/Ni(OAc)2ꢀ4H2O/Zn(OAc)2ꢀ2H2O.
dichloromethane–methanol yielded [Co(III)(L1a)(L1b)] (1) and
[Co(III)(L2a)(L2b)] (4), respectively. In both the cases the
ligands H2L1 and H2L2 are cleaved at a C–S bond to result
in two non-equivalent parts, viz., L1a and L1b or L2a and
L2b, and these in turn are still bound to the Co(III) center as
tridentate ligands, as shown in Scheme 1.
the reaction mixture after O2 purging. Similarly, in the case
of 4 the absorption spectrum measured from the isolated pro-
duct exhibited a broad band, which upon de-convolution
represents two less resolved bands positioned at 480 and
510 nm.
From the FTIR spectra of 1 and 4, it was possible to deduce
the binding of the –Oꢁ
The reactions were initially allowed to proceed under Ar
atmosphere and later on under O2 . During this process, the
reaction mixture goes through a color change from orange-
red to dark brown. The reaction of H2L1 with Co(acetate)2ꢀ
4H2O was monitored in solution by UV-Vis absorption spec-
tra as a function of time. It was noticed that when the reac-
tion mixture was maintained under Ar atmosphere, the
orange-red complex remains stable, but when the reaction
was purged with O2 , it quickly converted to a dark brown
Co(III) complex with cleavage of H2L1 as shown in Scheme
1. Thus, under Ar atmosphere the reaction mixture exhibited
a ligand ! metal charge transfer band at 425 nm in the
absorption spectra and this band was found to grow in inten-
sity as a function of time; this peak is reminiscent of a Co(II)
center. When the reaction mixture was bubbled with O2 , the
spectra exhibited a very broad band, which upon de-convolu-
tion represents two least resolved bands positioned at 440
and 475 nm, respectively, with almost equal absorbance, indi-
cating the formation of a more positive Co(III) center, favor-
ing a better charge transfer from the thiolate moiety that was
generated by cleavage (L1a). Similarly, the band observed at
300 nm under Ar atmosphere shifts to 285 nm when purged
with O2 . Even the absorption spectrum measured from the
dichloromethane solution of the isolated product exhibited
a spectrum that is exactly identical to that obtained from
group owing to the disappear-
phenolate
ance of the corresponding nOH vibration that is otherwise
present in the precursor ligand spectra. Involvement of the
=
–C N– moiety in binding the metal ion center is evident based
on the shift (8–20 cmꢁ1) observed in the stretching frequency
of this group in the complexes. Both the complexes exhibited
=
a strong nC C vibration arising from the –S–HC CH2 moiety
=
formed as a result of the C–S bond cleavage in L1 and L2 at
1525 and 1532 cmꢁ1, respectively. The molecular weights of
the ligands as well as the complexes were confirmed based
on the molecular ion peaks observed in their respective FAB
mass spectra. The results are consistent with mononuclear
complexes. Both the complexes were found to be diamagnetic
from their magnetic susceptibility measurements, supporting
the þ3 oxidation state of the cobalt.
Molecular structure of H2L1. H2L1crystallizes in the monocli-
nic system with P21/c space group. The molecule sits on a crys-
tallographic center of symmetry and hence each asymmetric
unit cell possesses two halves of the molecule. The molecule
exhibits an ‘S’-like structure. Such a molecular structure is
stabilized via the presence of a strong intramolecular 6-atom
O–Hꢀ ꢀ ꢀN type interaction between the phenolic–O–H and
=
the –N C– moieties and another weak intramolecular 9-atom
O–Hꢀ ꢀ ꢀS type interaction between the phenolic–O–H and the
Ph–S–CH2– moieties.
T h i s j o u r n a l i s Q T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 4
76
N e w . J . C h e m . , 2 0 0 4 , 2 8 , 7 5 – 8 4

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Table 1 Conformation of the chelates present in the complexes 1, 7, 5,
Crystal structure of 1 and the role of the anion of the Co(II)
salt. The crystal structure of the reaction product, [Co(III)-
(L1a)(L1b)] (1) shown in Fig. 1 reveals the presence of two
ligands, viz., L1a (dianionic) and L1b (monoanionic), formed
upon cleavage of a C–S bond, both acting as tridentate ligands
by extending the ONS binding core. This results in the forma-
tion of two 5-membered and two 6-membered chelate rings to
give a distorted octahedral Co(ONS)2 core. The conformations
of the various chelates present in the complex are shown in the
Table 1. The octahedral coordination geometry is much less
distorted compared with the regular octahedron geometry as
shown by the observed narrower bite angles, 88.3(1)ꢂ–
95.8(1)ꢂ, and the trans angles: 175.6(1)ꢂ, 175.6(1)ꢂ and
177.9(2)ꢂ. Selected bond lengths are given in Table 2 and the
bond angles in Table 3. The metric data is fully supported
by the cleavage of H2L1 in order to form the ethylene moiety
8, 3, 6 and 9
Complex
1
Chelate
Conformationa
Co1–N9a–C10a–C15a–S16a
Co1–S16b–C15b–C10b–N9b
Co1–O1b–C2b–C7b–C8b–N9b
Co1–O1a–C2a–C7a–C8a–N9a
Co18–N8–C7–C2–O1
Cs
C2
Skew boat
Boat
Cs
7
5
Co18–O16–C17–C17_2–O16_2
Co18–N8–C9–C10–C15–O16
Ni1–S23–C22–C21–S20
A
Skew boat
C2
Cs
Ni1–S20–C19–C14–N13
Ni1–S23–C24–C29–N30
C2
Skew boat
Ni1–N30–C31–C32–C41–O42
Ni1–N13–C12–C11–C2–O1
Ni18–O1–C2–C7–N8
Boat
Cs
˚
˚
=
C17b C18b (1.302 A) and Co–Sthiolate (2.227 A) and Co–
˚
Sthioether (2.238 A) bonds. No abnormal bond lengths were
observed in the structure.
8
3
Ni18–O16–C17–C17_2–O16_2
Ni18–N8–C9–C10–C15–O16
Zn1–S16–C17–C18–S19
A
Skew boat
C2
C2
A similar reaction carried out with another salt of Co(II),
CoCl2ꢀ6H2O, and H2L1 resulted in a product whose composi-
tion and crystal structure were found to be the same as that of
Zn1–S16–C15–C10–N9
Zn1–S19–C20–C25–N26
Zn1–N26–C27–C28–C33–O34
Zn1–N9–C8–C7–C2–O1
Cs
Skew boat
Skew boat
1
[Co(III)(L1a)(L1b)]. Based on FAB mass and H NMR studies,
it was found that the reaction carried out using Co(SO4)2ꢀ
7H2O and Co(acac)2ꢀ2H2O also resulted in the same product
and thereby exhibited C–S bond cleavage. Thus, in these four
cases the final product was found to be same, irrespective
of the anion of the Co(II) salt used.
6
9
Zn1–S20–C21–C21_2–S20_2
Zn1–S20–C19–C14–N13
Zn1–N13–C12–C11–C2–O1
Zn18–O1–C2–C7–N8
A
Cs
Skew boat
C2
Zn18–N8–C9–C10–C15–O16
Zn18–O16–C17–C17_2–O16_2
Skew boat
A
1H and 13C NMR studies. The absence of paramagnetic shifts
in the 1H NMR spectrum of 4 supports the presence of a
Co(III) center formed by the oxidation of Co(II). XRD supports
the Co being present in its 3þ state as well as the presence of
the C–S bond-cleaved fragments (L1a and L1b) bound to the
metal ion center as reported in this paper. This was further
supported by the 1H NMR spectrum of 1. The spectrum of
4 also clearly supports the formation of two ligands, L2a and
L2b, formed by the cleavage of a C–S bond in the reaction
between Co(II) acetate and H2L2: the imine proton peaks are
doubled and new signals from vinylic protons arise, as shown
in Fig. 2(a). The same information is also revealed through the
spectral changes observed in case of the aromatic protons.
These features are vividly highlighted when the spectrum of
4 is compared with that of the precursor ligand, H2L2, given
in Fig. 2(b). The peak observed at 3.195 ppm due to the
bridging –S–CH2–CH2–S– moiety in H2L2 disappears in the
spectrum of 4 and two new multiplets appear in the region
of 5.574–5.957 ppm, which are due to the vinyl protons (–S–
a
C2 ¼ half-chair form; Cs ¼ envelop form; A ¼ planar
CH CH2), the assignment of which is made using 1H–1H
=
COSY as shown by the cross peak in Fig. 3(a). Based on the
1H–13C HMQC experiments [Fig. 3(b)], the 13C peaks
observed at 128.8 and 126.9 ppm were assigned to S–CH ¼
=
CH2 and –S–CH CH2 , respectively. The peak doubling for
imine protons was further confirmed through the 1H–13C
HMQC experiment shown in Fig. 3(a).
Non-cleavage of the C–O bond in H2L3. Unlike the reactions
of H2L1and H2L2, the reaction of H2L3 with Co(acetate)2ꢀ
4H2O in a 1:1 ratio in dichloromethane–methanol yielded
[Co(L3)] (7) with no cleavage of the C–O bond (Scheme 1).
The elemental compositions of H2L3 and [Co(L3)] yielded
satisfactory results. The peak at 3423 cmꢁ1 due to nOH in the
FTIR spectrum of H2L3was found to disappear in the spec-
trum of 7 and furthermore the peak due to nCH N was shifted
=
from 1619 cmꢁ1 in the ligand to 1598 cmꢁ1 in the complex,
indicating the binding of cobalt through –Oꢁ and CH N,
=
respectively. The spectrum of crystals of 7 exhibited nC O at
=
1700 cmꢁ1 and two sharp peaks for nCH at 2924 and 2853
cmꢁ1. When these crystals were crushed, washed with diethyl
ether and dried in vacuo, the peaks at 1700, 2924 and 2853
cmꢁ1 disappeared, indicating the loss of acetic acid otherwise
present in the lattice. The molecular weight of H2L3 and
[Co(L3)] were confirmed based on their FAB mass spectra.
The observed magnetic moment value for 7 (mobs ¼ 4.899
BM) arises from the cobalt in its þ2 oxidation state along with
orbital contribution expected to arise from a high-spin d7 sys-
1
tem. In the H NMR spectrum of the ligand, H2L3, only the
peaks arising from one-half of the molecule were observed
owing to the symmetry. On the other hand, the 1H NMR spec-
trum of 7 exhibited paramagnetically shifted bands in the
region ꢁ25 to þ25 ppm.
Molecular structure of H2L3 and 7. Both the structures of H2L3
and 7 possess a center of symmetry and have only one-half of
the molecule in their asymmetric unit cells. The ORTEP plots
Fig. 1 Molecular structure with atom labeling for 1.
T h i s j o u r n a l i s Q T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 4
N e w . J . C h e m . , 2 0 0 4 , 2 8 , 7 5 – 8 4
77

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˚
Table 2 Selected bond distances (A) in the primary coordination sphere of complexes 1, 3, 5, 6, 7, 8 and 9
[Co(III)(L1a
)
[Co(L3)]ꢀ
[Ni(L2)]ꢀ
[Ni(L3)]ꢀ
[Zn(L3)]ꢀ
Bond
(L1b)] (1)
CH3COOH (7)a
0.5CH3OH (5)
CH3COOH (8)a
[Zn(L1)] (3)
[Zn(L2)] (6)a
2.073(2)
CH3OH (9)a
M–N
1.913(3)
1.926(2)
1.894(2)
1.914(2)
–
2.066(2)
2.007(2)
2.028(3)
2.028(3)
2.008(3)
2.014(3)
–
2.018(4)
2.010(4)
2.095(3)
2.101(4)
1.980(3)
2.009(3)
–
2.151(2)
2.020(2)
M–Ophenolate
1.978(2)
M–Oether
M–Sether
2.217(2)
–
2.178(3)
–-
–
2.692(1)
2.328(2)
–
2.227(1)
2.238(1)
2.413(2)
2.459(2)
2.582(2)
2.675(2)
a
Molecule possessing a center of symmetry.
of H2L3 and 7 are shown in Figs. 4 and 5, respectively. The
molecule of H2L3 is folded due to one C–Hꢀ ꢀ ꢀO (5-atom) type
intramolecular hydrogen bond interaction present between the
2. Reactions of H2L1 and H2L2 with Co(III)
Reactions of H2L1 and H2L2 with Co(acac)3 in 1 : 1 ratio at
room temperature as well as under reflux conditions in dichloro-
methane–methanol did not yield any products. But the same
reactions, when carried out in the presence of 2 equiv. of
methanolic NaOH, resulted in the formation of 1 and 4,
respectively, as confirmed by 1H NMR studies. Thus, the alkali
activates the thioether group while deprotonating the phenolic
–OH groups. This observation is in agreement with that
reported in the literature.4i
=
–CH N– and the Ph–O–CH2– moieties and one O–Hꢀ ꢀ ꢀN
(5-atom) type interaction present between the phenolic–O–H
=
and the –CH N– moieties. In the structure of 7, the cobalt
is present in a distorted octahedral geometry bound through
two phenolic moieties, two imine moieties and two ether oxy-
gens, resulting in a neutral mononuclear complex with a
Co(II)–N2O4 core. Thus, the X-ray structure clearly shows an
intact C–O bond and supports the specificity of Co(II) salts
towards the cleavage of C–S bonds rather than the C–O bond.
Among the coordinating atoms the imine nitrogens occupy
axial positions and the remaining four oxygen atoms occupy
the equatorial positions. The octahedral geometry is more dis-
torted than the regular octahedron geometry as shown by their
wider range of bite angles, 75.0(1)ꢂ to 112.5(2)ꢂ, and trans
angles, 155.7(1)ꢂ and 179.5(2)ꢂ. The conformations of the che-
lates found in 7 are given in Table 1. Selected bond lengths and
bond angles are given in Tables 2 and 3, respectively. However,
no abnormalities were found with the bond length data of
H2L3 and 7. The M–N and M–Ophenolate distances observed
in 7 with Co(II) are considerably longer, by about 0.15 and
3. Reaction of H2L1–H2L3 with Ni(II)
Reactions of H2L1–H2L3 with Ni(CH3COO)2ꢀ4H2O resulted in
the formation of the hexacoordinated Ni(II) complexes 2, 5 and
8, respectively, as shown in Scheme 1. In none of these final
products were either the C–S or the C–O bonds broken upon
reaction with Ni(II) salt, though C–S bond cleavage was
reported in the literature in the case of a thioether complex
of nickel.4j Thus, Ni(II) behaves quite differently from Co(II),
where the latter is stabilized in the þ3 oxidation state when
cleaving the C–S bond with H2L1 and H2L2, while with
H2L3 the final product is in the same þ2 oxidation state
and the C–O bond is intact. In the FTIR spectra of 2, 5
˚
0.10 A, respectively, when compared with similar bond lengths
observed in the structure of 1 with Co(III), due to the difference
in the oxidation states.
and 8 the observed decrease in nCH N (8–19 cmꢁ1) and the
=
Table 3 Selected bond angles (ꢂ) in the coordination sphere of complexes 1, 3, 5, 6, 7, 8 and 9
[Co(L3)]ꢀ
[Ni(L2)]ꢀ
[Ni(L3)]ꢀ
[Zn(L3)]ꢀ
[Co(III)(L1a)(L1b)] (1)
CH3COOH (7)
0.5CH3OH (5)
CH3COOH (8)
[Zn(L1)] (3)
[Zn(L2)] (6)
CH3OH (9)
Ophe–M–Ophe.
Ophe–M–N
87.89(9)
84.93(10)
95.81(10)
95.23(10)
86.25(10)
175.64(7)a
92.28(7)a
94.07(7)b
175.64(7)b
–
112.53(12)
81.99(9)
98.26(9)
93.67(12)
88.45(13)
90.28(13)
89.49(13)
88.33(13)
90.38(10)
170.90(9)
170.62(9)
90.23(8)
–
106.0(2)
96.11(16)
82.78(16)
104.25(13)
91.82(12)
99.45(13)
96.68(12)
90.07(12)
168.21(10)
86.03(9)
90.50(9)
162.64(9)
–
103.01(11)
88.33(8)
100.22(8)
111.57(11)
82.75(8)
104.07(8)
O
phe–M–S
–
–
162.82(5)
89.35(6)
–
O
phe–M–Oether
155.66(8)
88.30(8)
–
161.37(14)
89.29(14)
–
–
88.75(8)
156.60(7)
–
N–M–S
90.72(8)a
89.13(8)b
88.25(8)b
89.69(8)b
–
97.98(11)
83.55(11)
82.99(9)
99.17(10)
–
80.66(10)
88.94(10)
89.01(10)
78.99(10)
–
77.63(6)
91.94(6)
N–M–Oether
82.65(9)
96.99(9)
179.54(14)
–
96.41(15)
85.02(15)
178.2(2)
–
–
89.43(8)
81.04(8)
168.06(12)
–
N–M–N
S–M–S
177.94(12)
86.07(3)
–
177.44(14)
87.02(4)
–
165.31(13)
80.38(4)
–
166.33(11)
81.38(3)
–
Oether–M–Oether
74.96(10)
78.12(18)
74.35(10)
a
b
Co(III) bound to thioether. Co(III) bound to thiolate.
T h i s j o u r n a l i s Q T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 4
78
N e w . J . C h e m . , 2 0 0 4 , 2 8 , 7 5 – 8 4

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Fig. 2 1H-NMR spectra in DMSO-d6 of (a) complex 4 and (b) ligand
H2L2.
disappearance of nOH vibrations support the binding through –
Oꢁ and –CH N– moieties. The analytical and FAB mass data
=
fits with the mononuclear complexes shown in Scheme 1. The
experimental magnetic moments were found to be 2.841, 3.049
and 2.812 BM, respectively, for 2, 5 and 8 at room tempera-
ture. The 1H NMR spectra of these complexes exhibited broad
and shifted bands due to their paramagnetic nature, as sup-
ported by the magnetic moments. In the absorption spectra
of the Ni(II) complexes 2, 5 and 8, bands corresponding to
3
3
3
3A2g ! T1g(F) and A2g ! T1g(P) transitions are observed
at 567–624 and 445–471 nm, respectively, and a third band
3
3
due to A2g ! T2g at 879–908 nm supports the octahedral
geometry around the Ni(II) center.
Fig. 3 (a) 1H–1H HMQC spectrum of 4: (i) represents cross peak cor-
responds to the coupling of (–CH ¼ CH2) and (–CH ¼ CH2) protons,
(ii) represents cross peaks due to aromatic protons. (b) 1H–13C HMQC
spectrum of 4: (i) and (ii) correspond to the carbon resonances of two
Molecular structures of 5 and 8. The crystal structures of
both complexes 5 and 8 showed a distorted octahedral geome-
try around the Ni(II) center, in which Ni(II) is bound through
the N2O2S2 core in 5 and the N2O4 core in 8; both the corre-
sponding ligands act as hexadentate ones. The asymmetric unit
cell in 8 contains half of the molecule due to the center of sym-
metry. In 5, the asymmetric unit contains one molecule of the
complex and half a methanol molecule. The molecular struc-
ture of 5 is shown in Fig. 6. In the structures of 5 and 8, both
the nitrogens are disposed trans to each other. The observed
distortion in the geometry around the Ni(II) center in 5 is less
than that observed in 8 as judged based on the spread of the
bite angles [83.0(1)ꢂ–98.0(1)ꢂ] and the trans angles [170.6(1)ꢂ,
170.9(1)ꢂ and 177.4(2)ꢂ] in the case of 5, while these are
78.1(2)–106.0(2)ꢂ and 161.4(2)ꢂ, 161.4(2)ꢂ and 178.2(2)ꢂ,
respectively, for 8. In both the nickel complexes, the nickel(II)
exhibits five chelates, of which three are five-membered and
=
different –CH N groups.
two are six-membered ones (Table 1). The selected bond
lengths are given in Table 2 and the selected bond angles are
given in Table 3.
Hydrogen bonding in 5 and 8. In 5, there is one O–Hꢀ ꢀ ꢀO type
of hydrogen bond interaction between the solvent methanol
and the main compound, O1S–H1S to O1, where ‘S’ refers
to the solvent. In the case of 8, the lattice acetic acid forms
three hydrogen bonds with two different molecules of 8, in
which two are of the C–Hꢀ ꢀ ꢀO type while the third one is of
Oꢀ ꢀ ꢀHꢀ ꢀ ꢀO type. The molecule also forms intermolecular
hydrogen bonds through C–Hꢀ ꢀ ꢀO types of interaction.
T h i s j o u r n a l i s Q T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 4
N e w . J . C h e m . , 2 0 0 4 , 2 8 , 7 5 – 8 4
79

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Fig. 4 ORTEP drawing for the molecular structure of H2L3. The
molecule sits on a center of symmetry.
Fig. 6 Molecular structure for 5 as an ORTEP plot.
in Fig. 7. In all three structures the corresponding ligand acts
as a doubly negative one and extends six coordinating sites to
the Zn(II) center, resulting in neutral mononuclear
complexes. All three complexes have highly distorted octahe-
dral Zn(II) centers, as can be judged from the spread in their
observed bite angles and trans angles: 79.0(1)ꢂ–104.3(1)ꢂ and
162.6(1)ꢂ, 165.3(2)ꢂ and 168.2(1)ꢂ in the case of 3; 77.6(1)ꢂ–
103.0(1)ꢂ and 162.8(1)ꢂ, 162.8(1)ꢂ and 166.3(1)ꢂ for 6;
74.4(1)ꢂ–111.6(1)ꢂ and 156.6(1)ꢂ, 156.6(1)ꢂ and 168.1(1)ꢂ in
the case of 9. Among the three complexes, the Zn(II) center
in 9 with an N2O4 core is more distorted than in 3 and 6 having
an N2O2S2 core. In all cases both nitrogen atoms are disposed
trans to each other. The conformation of the three 5-mem-
bered and two 6-membered chelate rings formed by the Zn(II)
center in each case is given in Table 1 and selected bond angles
in the coordination sphere are given in Table 3.
4. Reactions of H2L1–H2L3 with Zn(II)
The products 3,
6 and 9 are obtained by reacting
Zn(CH3COO)2ꢀ2H2O with H2L1, H2L2 and H2L3, respectively.
The product formulations were supported by the observed
satisfactory elemental analysis data as well as the molecular
weight obtained through the molecular ion peak in the FAB
mass spectra. For these diamagnetic Zn(II) complexes, the
1H NMR spectra exhibited peaks corresponding to half of
the ligand, suggesting retention of the ligand symmetry even
in the bound state. The 1H NMR peaks arising from the
–S–CH2–CH2–S– moiety in the case of 3 and 6 are found
to be overlapped by the broad peak arising from water in
DMSO-d6 . On the other hand the peak arising from
–O–CH2–CH2–O– in 9 was observed at 4.384 ppm. Disappear-
ance of the peak due to phenolic –OH and an upfield shift
The bond lengths observed in 9, Zn–Oether ¼ 2.328(2), Zn–
=
observed in the peak for the –CH N proton both indicate that
the Zn(II) is bound through the azomethine and phenolic
groups in 3, 6 and 9.
˚
Ophenolic ¼ 2.020(2) and Zn–N ¼ 2.151(2) A, are quite normal
when compared with the corresponding distances reported in
the literature and the metric parameters fit well with an octahe-
dral geometry around the Zn(II) center. The observed Zn–Oether
distances in the present case are well within the range reported
Molecular structures of 3, 6 and 9. Lattices of 6 and 9 have
a center of symmetry. From the crystal structures of all three
Zn(II) complexes it was observed that neither the C–S nor
C–O bond is cleaved. The ORTEP structure for 9 is shown
Fig. 5 Molecular structure for 7 as an ORTEP plot. Co(II) sits on
a center of symmetry.
Fig. 7 Molecular structure for 9 as an ORTEP plot. Zn(II) sits on
a center of symmetry.
T h i s j o u r n a l i s Q T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 4
80
N e w . J . C h e m . , 2 0 0 4 , 2 8 , 7 5 – 8 4

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5a
˚
for a Zn(II)-crown ether complex (2.34–2.60 A). Recently,
we reported a weak interaction of the pyranose oxygen with
5b
˚
the Zn(II) center, resulting in a Zn–O distance of 2.759 A.
On the other hand, in the case of 3 and 6 the bond lengths,
˚
Zn–Ophenolic ¼ 1.978(2)–2.009(1)
A
and Zn–N ¼ 2.073(1)–
˚
2.101(1) A, are well within the covalent bond distances for
the corresponding pairs, while the Zn–S distances are in the
˚
range of 2.582(1)–2.692(1) A, well within the sum of the van
der Waals radii. In the literature, the Zn–S distances in thio-
˚
lates are observed to be around 2.300–2.360 A for terminal
5c
˚
bonds and 2.400–2.450 A for bridging ones. The Zn–S dis-
tances observed in the present case are somewhat longer than
˚
that observed in the crown thioether (2.497 A) and shorter
than that observed in the complex of dithiaalkyl-substituted
The Zn(II) exhibits
5d,1c
˚
triazine 1-oxide (2.649–2.720 A).
pseudo-octahedral geometry. However, when these two Zn–S
interactions are disregarded the resulting ZnN2O2 core does
not fit well with a tetrahedral geometry, strongly suggesting
that the coordination sphere is more of a distorted octahedral
rather than tetrahedral. The selected bond lengths of the coor-
dination sphere are given in Table 2.
Conclusions and comparisons
The complexes of Co(III), Co(II), Ni(II) and Zn(II) with H2L1–
H2L3 reported in this paper are all neutral and found to have
distorted octahedral geometries, however, 3 and 6 have a
pseudo-octahedral geometry. The present study clearly
demonstrates the formation of two tridentate ligands from
the precursor hexadentate ligands (N2O2S2 , H2L1 and H2L2)
via C–S bond cleavage as a result of the oxidation of Co(II).
Such C–S bond cleavage was found to occur with the Co(II)
salts of chloride, sulfate, acetate and acetylacetonate. On the
other hand, H2L3, possessing a N2O4 core, does not exhibit
cleavage of the C–O bond under the same conditions. On going
from Co(III) (1) to the Co(II) (7) complex, the corresponding
bond lengths in the primary coordination sphere are consider-
ably increased, consistent with the change in the oxidation state
of cobalt.
Fig. 8 Stereo views of the primary coordination spheres for the
complexes (a) 7 (CoN2O4), (b) 8 (NiN2O4) and (c) 9 (ZnN2O4).
Experimental details
General remarks
1,2-Dibromoethane was procured from Spectrochem Pvt.
Ltd.; o-hydroxynapthaldehyde and 1,2-di(2-aminophenylthio)-
ethane were synthesized as per the reported procedures.6a,6b
Ethylene-2-20-(dioxydibenzaldehyde) was synthesized as per
the reported procedure but with some modifications.6c All
the solvents were purified and dried immediately before use.
Elemental analysis was carried out on a CE Instruments Flash
EA 1112 series apparatus; FTIR spectra were recorded on
Nicolet Magna IR 550; UV-Vis spectra were recorded on a
UV-2101PC spectrophotometer. FAB mass spectra were
recorded on a JEOL SX 102/DA-6000 mass spectrometer data
system using argon–xenon (6 kV, 10 mA) as the FAB gas. The
accelerating voltage was 10 kV and the spectra were recorded
at room temperature with m-nitrobenzyl alcohol (NBA) as the
matrix. GC-mass spectra were recorded on a 5989 B MS
engine model from Hewlett Packard. 1H NMR spectra were
recorded on a Varian VXR 300S. 13C spectra were recorded
on a Bruker Avance DRX 500 spectrometer.
To observe the role of the metal ion, we extended these stu-
dies using Ni(II) and Zn(II) salts. Combining the present studies
with what is known in the literature, the following aspects are
relevant for bond cleavage: (a) the presence of ‘S’ instead of
‘O’, (b) the metal ion should support various oxidation states
and (c) the thioether chelate should be 5-membered.
In all the complexes the two imine nitrogens are trans- to
each other. On going from a trivalent complex (1, Co3þ) to
divalent complexes (Co2þ: 7; Ni2þ: 5 and 8; Zn2þ: 3, 6 and
9) the primary coordination distances, viz., M–N, M–Ophenolate
˚
or M–S, generally increase by 0.1 A or more owing to the
change in size of the corresponding metal ion center. These
distances increase further in the case of the Zn2þ complexes
as compared to the Ni2þ or Co2þ complexes, owing to expan-
sion of the coordination sphere of Zn2þ from its commonly
observed tetrahedral geometry to the pseudo-octahedral
one.
The Co(II), Ni(II) and Zn(II) complexes derived from H2L3
are more distorted than the Co(III), Ni(II) and Zn(II) complexes
derived from the other two ligands, viz., H2L1 and H2L2. The
extent of distortion observed about the metal ion coordination
sphere in these complexes follows a trend, Zn(II) > Co(II) >
Ni(II), as can be deduced from the corresponding bond lengths
and bond angles. This can also be seen from the stereo views
of the complexes 7, 8 and 9 given in Fig. 8. Among all the
complexes, 1 with Co(III) has the least distortion due to
cleavage of the hexadentate ligand into two tridentate ligands.
The conformation of the 5-membered rings can be half chair
(C2), envelope (Cs) or planar (A), while the six-membered rings
exhibit boat or skew boat conformations.
Syntheses
Ethylene-2-20-(dioxydibenzaldehyde). A solution of sodium
hydroxide (11.25 g, 279 mmol) in water (78 ml) was slowly
added over a period of 30 min to a mixture of salicylaldehyde
(30.53 g, 250 mmol) and 1,2-dibromoethane (72.8 g, 387 mmol)
at its boiling point. After an additional 20 h of boiling, the
reaction mixture was cooled to room temperature. The organic
phase was separated and the aqueous phase was extracted with
dichloromethane (2 ꢃ 40 ml), then combined with the original
organic phase. The organic layer was then washed with 10%
sodium hydroxide (20 ml) and dried over MgSO4 . The
dichloromethane was removed by rotary evaporation and the
T h i s j o u r n a l i s Q T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 4
N e w . J . C h e m . , 2 0 0 4 , 2 8 , 7 5 – 8 4
81

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resulting residue was cooled at 4 ꢂC overnight. The solid thus
separated was filtered and was washed with diethyl ether and
then dried under vacuum. The colorless solid was further crys-
tallized from acetone or hot petroleum ether (5.5 g, 16%). M.p.
110–112 ꢂC. 1H-NMR (300 MHz, CDCl3) d: 4.520 (s, 4H,
–OCH2CH2O–), 7.031–7.842 (m, 8H, aromatic H), 10.412
1435, 1249, 1177, 1143, 927, 747. UV-Vis (DMSO) lmax/nm
(e/molꢁ1 L cmꢁ1): 475 (10 800), 440 (10 700), 285 (57 800).
FAB-MS m/z: 541 [M]þ (85%). Anal. found: C 62.32, H
3.75, N 5.00, S 11.31%; calcd for C28H21CoN2O2S2 : C 62.22,
H 3.92, N 5.18, S 11.86%.
(s, 2H, –CH O). FTIR (KBr) u/cmꢁ1: 2946, 2866, 1687, 1597,
[Ni(L1)], 2. To a CH2Cl2–CH3OH (9.5:0.5 v/v) solution of
H2L1 (0.485 gm, 1 mmol), Ni(CH3COO)2ꢀ4H2O (0.249 gm,
1 mmol) was added and the mixture stirred for 6 h. The clear
solution resulting at the end was layered with diethyl ether to
get dark red colored crystals (0.300 g, 55%). M.p. > 250 ꢂC.
FTIR (KBr) u/cmꢁ1: 1604, 1570, 1518, 1438, 1388, 1139,
755. UV-Vis (DMSO) lmax/nm (e/molꢁ1 L cmꢁ1): 879 (26),
567 (142), 455 (9300), 309 (10 040). FAB-MS m/z: 541 [M]þ
(100%). Anal. found: C 61.73, H 3.89, N 4.95%; calcd for
C28H22NiN2O2S2 : C 62.13, H 4.10, N 5.18%.
=
1485, 1452, 1242, 1061, 834, 754. GC-MS m/z: 270 [M]þ. Anal.
found: C 70.89, H 4.97%; calcd for C16H14O4 : C 71.10, H
5.22%.
1,2-Di(salicylaldimino-o-phenylthio)ethane,
H2L1.
This
ligand was synthesized in 85% yield as per the procedure
reported earlier.3a The compound was crystallized from a mix-
ture of CHCl3 and EtOH and the structure was established by
single crystal XRD. M.p. 189–190 ꢂC. 1H-NMR (300 MHz,
[D6]DMSO) d: 3.207 (s, 4H, –SCH2CH2S–), 6.948–7.663
[Zn(L1)], 3. This complex was synthesized by adopting the
procedure used for 2, with Zn(CH3COO)2ꢀ2H2O (0.220 gm,
1 mmol) in place of nickel acetate. The clear solution was con-
centrated to give bright yellow-colored crystals (0.220 g, 40%).
M.p. > 250 ꢂC. 1H-NMR (300 MHz, [D6]DMSO) d: 6.364–
=
(m, 16H, aromatic H), 8.913 (s, 2H, –CH N), 12.984 (s, 2H,
–OH). 13C-NMR (300 MHz, [D6]DMSO) d: 30.6
=
(–SCH2CH2S–), 163.0 (–CH N), 116.6–160.2 (aromatic C).
FTIR (KBr) u/cmꢁ1: 3000, 1612, 1573, 1561, 1468, 1279,
1181, 907, 753. UV-Vis (CH2Cl2) lmax/nm (e/molꢁ1 L cmꢁ1):
351 (26 900), 272 (52 100), 234 (54 800). FAB-MS m/z: 485
[M]þ (70%). Anal. found: C 69.82, H 4.91, N 5.38, S 12.74%;
calcd for C28H24N2O2S2 : C 69.39, H 4.99, N 5.78, S 13.23%.
=
7.682 (m, 16H, aromatic H), 8.708 (s, 2H, –CH N). FTIR
(KBr) u/cmꢁ1: 1611, 1560, 1465, 1370, 1276, 1180, 752.
FAB-MS m/z: 548 [M]þ (15%). Anal. found: C 61.10, H
4.29, N 5.25%; calcd for C28H22N2O2S2Zn: C 61.37, H 4.05,
N 5.11%.
1,2-Di(naphthaldimino-o-phenylthio)ethane,
H2L2.
This
ligand was synthesized by adopting the procedure used for
H2L1 but with o-hydroxynapthaldehyde in place of salicylalde-
hyde (2.8 g, 95%). M.p. 198–200 ꢂC. 1H-NMR (300 MHz,
[D6]DMSO) d: 3.195 (s, 4H, –SCH2CH2S–), 7.023–8.522 (m,
[Co(III)(L2a)(L2b)], 4. This complex was synthesized by
adopting the procedure used for 1, with H2L2 (0.580 gm,
0.991 mmol) in place of H2L1. The reaction mixture was fil-
tered and the filtrate was layered with diethyl ether to get the
dark brown colored solid, which was dried in vacuo (0.500 g,
79%). M.p. > 200 ꢂC. 1H-NMR (300 MHz, [D6]DMSO) d:
=
20H, aromatic H), 9.630 (s, 2H, –CH N), 15.384 (s, 2H,
–OH). 13C-NMR (300 MHz, [D6]DMSO) d: 30.0
=
(–SCH2CH2S–), 155.9 (–CH N), 118.4–136.3 (aromatic C).
FTIR (KBr) u/cmꢁ1: 3400, 1620, 1553, 1460, 1326, 1168,
816, 743. UV-Vis (DMSO) lmax/nm (e/molꢁ1 L cmꢁ1): 471
(18 900), 439 (25 700), 398 (36 800), 320 (35 700). FAB-MS
m/z: 585 [M]þ (100%). Anal. found: C 73.07, H 4.66, N
4.64%; calcd for C36H28N2O2S2 : C 73.95, H 4.83, N 4.79%.
5.574–5.957 (s, 3H, –SCH CH2), 6.621–8.583 (m, 20H, aro-
=
=
matic H), 9.347 (s, 1H, –CH N), 9.384 (s, 1H, –CH N).
=
13
=
C-NMR (300 MHz, [D6]DMSO) d: 126.9 (–SCH CH2),
=
=
=
128.8 (– SCH CH2), 153.0 (–CH N), 155.3 (–CH N), 115–
137 (aromatic C). FTIR (KBr) u/cmꢁ1: 1600, 1572, 1532,
1515, 1423, 1385, 1183, 747. UV-Vis (DMSO) lmax/nm
(e/molꢁ1 L cmꢁ1): 510 (15 500), 480 (20 100), 446 (17 100), 341
(33 700), 284 (88 400). FAB-MS m/z: 641 [M]þ (100%). Anal.
found: C 67.15, H 3.86, N 4.15%; calcd for C36H25CoN2O2S2 :
C 67.50, H 3.93, N 4.37%.
1,2-Di(O-salicylaldimino-o-hydroxyphenyl)ethane, H2L3. A
25 ml ethanolic solution containing ethylene-2-2’-(dioxydiben-
zaldehyde) (1.25 g, 4.629 mmol) and o-aminophenol (1.07 g,
9.820 mmol) was refluxed for 6 h; then the contents of the flask
were cooled to room temperature, yielding yellow-colored
needles suitable for single crystal XRD (1.78 g, 85%). M.p.
122–124 ꢂC. 1H-NMR (300 MHz, CDCl3) d: 4.519 (s, 4H,
–OCH2CH2O–), 6.737–8.145 (m, 16H, aromatic H), 9.083
[Ni(L2)], 5. This compound was synthesized by adopting the
procedure used for 2 with H2L2 (0.585 gm, 1 mmol) and
Ni(CH3COO)2ꢀ4H2O (0.249 gm, 1 mmol). The clear reaction
mixture was layered with diethyl ether to yield dark red
colored crystals (0.385 g, 60%). M.p. > 250 ꢂC. FTIR (KBr)
u/cmꢁ1: 1608, 1569, 1530, 1389, 1266, 1177, 828, 747. UV-
Vis (DMSO) lmax/nm (e/molꢁ1 L cmꢁ1): 881 (66), 599 (276),
471 (56 700), 445 (43 800), 334 (46 500), 279 (91 400). FAB-
MS m/z: 641 [M]þ (100%). Anal. found: C 66.93, H 4.37, N
3.97%; calcd for C36H26NiN2O2S2 : C 67.41, H 4.09, N 4.37%.
(s, 2 H, –CH N). FTIR (KBr) u/cmꢁ1: 3423, 1619, 1593,
=
1489, 1449, 1374, 1221, 1047, 748. UV-Vis (DMSO) lmax/nm
(e/molꢁ1 L cmꢁ1): 391 (16 750), 354 (36 800), 323 (30 050).
FAB-MS m/z: 453 [M]þ (65%). Anal. found: C 73.90, H 5.06,
N 5.74%; calcd for C28H24N2O4 : C 74.32, H 5.35, N 6.19%.
[Co(III)(L1a)(L1b)], 1. To a CH2Cl2–CH3OH (9.5:0.5 v/v)
solution of H2L1 (0.480 gm, 0.989 mmol), Co(CH3-
COO)2ꢀ4H2O (0.253 gm, 1.02 mmol) was initially allowed to
react under Ar atmosphere and then followed by purging O2
for 8 h. During this time, the reaction mixture went through
a color change from orange red to dark brown. The reaction
mixture was filtered. The residue was washed with diethyl ether
and dried in vacuo. The filtrate was layered with diethyl ether
to get dark brown colored crystals suitable for single crystal
XRD (0.470 g, 86%). M.p. > 250 ꢂC. 1H-NMR (300 MHz,
[Zn(L2)], 6. This compound was synthesized by adopting the
procedure used for 2 using H2L2 (0.585 gm, 1 mmol) and
Zn(CH3COO)2ꢀ2H2O (0.220 gm, 1 mmol). The clear reaction
mixture obtained was concentrated to give bright yellow-
colored crystals (0.290 g, 48%). M.p. > 250 ꢂC. 1H-NMR
(300 MHz, [D6]DMSO) d: 6.566–8.229 (m, 20H, aromatic
H), 9.363 (s, 2H, –CH N). FTIR (KBr) u/cmꢁ1: 1608, 1567,
=
1531, 1394, 1362, 1177, 832, 747. FAB-MS m/z: 648 [M]þ
(85%). Anal. found: C 66.90, H 3.90, N 4.15%; calcd for
C36H26N2O2S2Zn: C 66.72, H 4.04, N 4.32%.
=
[D6]DMSO) d: 5.572–5.889 (s, 3H, –SCH CH2), 6.423–8.476
=
(m, 16H, aromatic H), 8.805 (s, 1H, –CH N), 8.934 (s, 1H,
=
–CH N). 13C-NMR (300 MHz, [D6]DMSO) d: 159.4
(–CH N), 162.2 (–CH N), 113.5–166.0 (aromatic C and
=
[Co(L3)], 7. To a CH2Cl2–CH3OH (20:10 v/v) solution of
H2L3 (0.894 gm, 1.974 mmol), Co(CH3COO)2ꢀ4H2O (0.523
=
=
–CH CH2). FTIR (KBr) u/cmꢁ1: 1604, 1573, 1519, 1525,
T h i s j o u r n a l i s Q T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 4
82
N e w . J . C h e m . , 2 0 0 4 , 2 8 , 7 5 – 8 4

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Table 4 Summary of crystallographic data for H2L1, H2L3, 1, 3, 5, 6, 7, 8 and 9
Compounds
H2L1
H2L3
1
3
5
6
7
8
9
Empirical
formula
Formula
weight
C28H24
-
C14H12NO2
226.25
C28H21
-
C28H22
-
C36.5H28
-
C18H13
-
C16H15
-
C16H15
-
C15H15
NO3Zn0.5
289.96
-
N2O2S2
484.61
CoN2O2S2
540.52
N2O2S2Zn
547.97
N2O2.5S2Ni
657.44
NOS Zn0.5
648.08
Co0.50NO4
314.75
Ni0.5O4
314.64
T/K
Crystal
173(2)
173(2)
Monoclinic Orthorhombic Monoclinic Tetragonal
150(2)
173(2)
173(2)
Triclinic
173(2)
Monoclinic
173(2)
Tetragonal
173(2) 173(2)
Tetragonal Tetragonal
system
Space group
P21/c
Pbcn
Cc
P41
P1
C2/c
P42/n
P42/n
P42/n
˚
a/A
10.716(1)
16.811(1)
13.097(1)
17.254(1)
8.395(1)
15.994(1)
15.279(1)
12.807(1)
12.191(1)
11.383(1)
11.383(1)
18.347(1)
10.750(1)
12.299(1)
12.656(1)
84.38(1)
67.41(1)
70.99(1)
1460.0(2)
2
22.994(1)
7.612(1)
17.980(2)
13.929(2)
13.929(2)
14.231(1)
13.925(2)
13.925(2)
14.181(3)
13.925(2)
13.925(2)
14.181(3)
˚
b/A
˚
c/A
a/ꢂ
b/ꢂ
g/ꢂ
104.23(1)
94.51(1)
110.55(1)
3
˚
U/A )
2287.0(3)
4
2316.7(1)
8
2378.1(3)
4
2377.3(3)
4
2946.8(5)
4
2761.1(1)
8
2749.8(8)
8
2749.8(8)
8
Z
m/mmꢁ1
Reflections
collected
Independent
reflections
Rint
0.263
12 704
0.087
9192
0.927
6743
1.239
8877
0.848
5901
1.012
4626
0.680
17 104
0.765
18 110
0.939
17 541
4014
1496
3542
3546
4324
2501
2620
2594
2496
0.0281
0.0501
0.0660
0.1532
0.0939
0.1711
0.0317
0.0276
0.0624
0.0303
0.0636
0.0485
0.0375
0.072
0.0357
0.0507
0.1099
0.0750
0.1229
0.0311
0.0339
0.0664
0.0529
0.0726
0.1015
0.0439
0.0924
0.0787
0.1060
0.1233
0.0746
0.1695
0.1044
0.1863
0.1048
0.0382
0.0708
0.0756
0.0818
R1 [I > 2s(I)] 0.0634
wR2 [I > 2s(I)] 0.1619
R1 (all data) 0.0744
wR2 (all data) 0.1712
0.0477
0.0737
gm, 2.1 mmol) was added; O2 was purged into the reaction
mixture while stirring for 6 h. The residue was filtered and
the filtrate was concentrated to give red-colored crystals
(0.900 g, 80%). M.p. > 200 ꢂC. FTIR (KBr) u/cmꢁ1: 1598,
1583, 1469, 1390, 1305, 1284, 1141, 734. UV-Vis (DMSO)
Structure determination
Single crystal X-ray diffraction data were collected for all the
compounds on a Nonius Kappa CCD diffractometer in the
f scan þ o scan mode using Mo-Ka of wavelength 0.71073
˚
A. All the structures were solved using direct methods with
l
max/nm (e/molꢁ1 L cmꢁ1): 446 (26 700), 312 (33 700).
SIR-92 (H2L1 and 3) and SHELXS-97 (H2L3, 1, 5, 7, 8
and 9) and were refined using the SHELXL-97 program.7,8
The diagrams were generated using ORTEP3.9 Full-matrix
least-squares refinement with anisotropic thermal parameters
for all non-hydrogen atoms was used. In case of the ligand
structures, –OH hydrogen positions were recovered from the
difference Fourier map. The hydrogen atoms were treated as
riding atoms with fixed thermal parameters. The empirical
absorption correction was applied in the case of 1 and 3. In
other structures there was no absorption correction employed.
The crystals are found to be stable and other details of data
collection and structure refinement are provided in Table 4.y
FAB-MS m/z: 509 [M]þ (10%). Anal. found: C 65.90, H
4.43, N 5.25%; calcd for C28H22CoN2O4 : C 66.02, H 4.35,
N 5.50%.
[Ni(L3)], 8. To a CH2Cl2–CH3OH (20:10 v/v) solution of
H2L3 (0.880 gm, 1.943 mmol), Ni(CH3COO)2ꢀ4H2O (0.530
gm, 2.129 mmol) was added and the mixture stirred for 6 h.
The residue was filtered and the filtrate concentrated to give
dark red colored crystals (0.750 g, 76%). M.p. > 200 ꢂC. FTIR
(KBr) u/cmꢁ1: 1600, 1583, 1469, 1279, 1241, 742, 500. UV-
Vis (DMSO) lmax/nm (e/molꢁ1 L cmꢁ1): 908 (50), 624 (230),
471 (33 950), 343 (19 600), 314 (36 350). FAB-MS m/z: 509
[M]þ (45%). Anal. found: C 65.54, H 4.81, N 5.06%; calcd
for C28H22NiN2O4 : C 66.05, H 4.36, N 5.50%.
Acknowledgements
CPR acknowledges financial support from the Council of
Scientific and Industrial Research (CSIR), New Delhi, and
the Department of Science and Technology, New Delhi. GR
acknowledges an SRF fellowship from CSIR.
[Zn(L3)], 9. To a CH2Cl2–CH3OH (20:10 v/v) solution of
H2L3 (0.900 gm, 1.987 mmol), Zn(CH3COO)2ꢀ2H2O (0.470
gm, 2.136 mmol) was added and the mixture stirred for 6 h.
The reaction mixture was filtered and the filtrate was concen-
trated and layered with diethyl ether to give a dark yellow-
colored solid. This was separated by filtration and the residue
was washed with diethyl ether. The compound was recrystal-
lised from methanol to give bright yellow-colored crystals
suitable for a single crystal XRD study (0.719 g, 70%). M.p.
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175–80 ꢂC. H-NMR (300 MHz, [D6]DMSO) d: 4.384 (s, 4H,
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C
C 65.19, H 4.30, N 5.43%.
64.89,
H 4.34, N 5.29%; calcd for C28H22N2O4Zn:
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N e w . J . C h e m . , 2 0 0 4 , 2 8 , 7 5 – 8 4
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C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 4
84
N e w . J . C h e m . , 2 0 0 4 , 2 8 , 7 5 – 8 4