Spectroscopic and thermal studies of bis(N,N′-dimethylethylenediamine) and bis(N,N-dimethylethylenediamine)saccharinato complexes of Co(II), Ni(II), and Cu(II)

Article abstract of DOI:10.1081/SIM-120016874

The mixed-ligand saccharin (Hsac) complexes of Co(II), Ni(II) and Cu(II) with N,N′-dimethylethylenediamine (dmen), and N,N-dimethylethylenediamine (ndmen) (Figure 1) were synthesized and characterized by elemental analysis, magnetic susceptibility, spectr

Full text of DOI:10.1081/SIM-120016874

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Spectroscopic and Thermal Studies of
bis(N,N′‐Dimethylethylenediamine) and
bis(N,N‐Dimethylethylenediamine)saccharinato
Complexes of Co(II), Ni(II), and Cu(II)
Okan Z. Yeşilel a , Hasan İçbudak a , Halis Ölmez a & Panče Naumov b
a Department of Chemistry , Ondokuz Mayıs University , 55139, Samsun, Turkey
b Faculty of Sciences, Institute of Chemistry , Sv. Kiril i Metodij University , POB 162,
MK‐1001, Skopje, Macedonia
Published online: 15 Aug 2006.
To cite this article: Okan Z. Yeşilel , Hasan İçbudak , Halis Ölmez & Panče Naumov (2003) Spectroscopic and Thermal Studies
of bis(N,N′‐Dimethylethylenediamine) and bis(N,N‐Dimethylethylenediamine)saccharinato Complexes of Co(II), Ni(II), and
Cu(II), Synthesis and Reactivity in Inorganic and Metal-Organic Chemistry, 33:1, 77-90, DOI: 10.1081/SIM-120016874
To link to this article: http://dx.doi.org/10.1081/SIM-120016874
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SYNTHESIS AND REACTIVITY IN INORGANIC AND METAL-ORGANIC CHEMISTRY
Vol. 33, No. 1, pp. 77–90, 2003
Spectroscopic and Thermal Studies of
bis(N,N’-Dimethylethylenediamine) and
bis(N,N-Dimethylethylenediamine)saccharinato
Complexes of Co(II), Ni(II), and Cu(II)
1
1,
1
*
¨
˙
Okan Z. Yes¸ilel, Hasan Ic¸budak, Halis Olmez,
and Pancˇe Naumov2
1Department of Chemistry, OndokuzMayıs University,
Samsun, Turkey
2Faculty of Sciences, Institute of Chemistry, Sv. Kiril i
Metodij University, Skopje, Macedonia
ABSTRACT
The mixed-ligand saccharin (Hsac) complexes of Co(II), Ni(II) and
Cu(II) with N,N’-dimethylethylenediamine (dmen), and N,N-dimethyl-
ethylenediamine (ndmen) (Figure 1) were synthesized and characterized
by elemental analysis, magnetic susceptibility, spectral (UV-Vis and FT-
IR) methods, and simultaneous TG, DTG and DTA techniques. The
complexes have pseudooctahedral geometries with two dimethylethyl-
enediamine molecules coordinated to the metal ions as chelating ligands
*
˙
Correspondence: Hasan Ic¸budak, Department of Chemistry, Ondokuz Mayıs
University, 55139 Samsun, Turkey; E-mail: icbudak@omu.edu.tr.
77
DOI: 10.1081/SIM-120016874
0094-5714 (Print); 1532-2440 (Online)
www.dekker.com
Copyright D 2003 by Marcel Dekker, Inc.

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78
Yes¸ilel et al.
through their two nitrogen atoms and two monodentate saccharinato
ligands in the trans positions for the complexes of the type [M(sac–
O)2(dmen)2] (M = Co(II), Ni(II)), and [M(sac-N)2(ndmen)2] (M = Co(II),
Ni(II), Cu(II)) and two aqua ligands in the trans positions in
[Cu(H2O)2(dmen)2](sac)2. (sac–O; sac–N = the saccharinato ligand
may be coordinated to the metal ions through their carbonyl oxygen or
their nitrogen atom, respectively). The decomposition mechanism and
thermal stability of the solid complexes are interpreted in terms of their
structures. The thermal stability order of the investigated complexes is
Cu(II) > Co(II) > Ni(II) while the bis(N,N’,-dimethylethylenediamine)
complexes are thermally less stable than those of bis(N,N-dimethyl-
ethylenediamine). The final decomposition products—the respective
metal oxides—were identified by FT-IR spectroscopy.
Key Words: Saccharinato complexes; N, N’-Dimethylethylenediamine;
ve N, N-Dimethylethylenediamine; Thermal analysis.
INTRODUCTION
Saccharin (Hsac, also known as o-benzosulfimide, 2,3-dihydro-3-oxo-
benzisosulfonazole, 1,2-benzisothiazol-3(2H)-one 1,1-dioxide) is widely
used as food additive, artificial sweetener and electroplating brightener.
However, the suspected carcinogenic nature of saccharin has resulted in
much scientific attention and in studies of the saccharinates of various me-
tals. Because of the biological significance of saccharin, there has been
increased interest in metal complexes, especially first-row transition metals.
A suggestion has been made that the importance of saccharin complexes lies
in the potential use of saccharin as an antitode for metal poisoning; the 1,10-
phenantroline chelator may act as potential antitumor agent. The biological
activities of many metal complexes are found to vary with small changes in
their composition and configuration.[1,2] Ethylenediamine chelator is an N-
CH2 CH2
CH2 CH2
H
H
H3C
H3C
H
H
N
N
N
N
O
O
H3C
CH3
O
C
S
N
-
sac
dmen
ndmen
Figure 1. Structures of the ligands: sac = deprotonated saccharin; dmen = N,N’-
dimethylethylenediamine; ndmen = N,N-dimethylethylenediamine.

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Saccharinato Complexes
79
donor ligand like 1,10-phenantroline. In the last two decades, the synthesis
and spectroscopic properties,[3–7] particularly, systematic vibrational pro-
perties[8–12] of the metal saccharinates and metal complexes including
saccharin and various N-donor ligands (mono- or bidentate) have been
intensively studied by many investigators. A number of crystal structures of
metal saccharinate complexes have been determined.[13–17] The thermal
properties of the metal saccharinates and mixed-ligand complexes have also
been investigated.[18–21]
In the present paper, we report the synthesis, spectroscopic, and ther-
mal properties of some new mixed-ligand complexes of Co(II), fNi(II)
and Cu(II) containing saccharin, N,N’-dimethylethylenediamine, and N,N-
dimethylethylenediamine. The structures of the ligands are shown in
Figure 1.
EXPERIMENTAL
Materials and Instrumentation
All chemicals used were analytical regent products. Sodium sac-
charinate was used in the preparations of the complexes. Elemental analyses
¨ ˙
for C, H, and N were carried out at the TUBITAK Marmara Research
Centre. Magnetic susceptibility measurements at room temperatures were
performed using a Sherwood Scientific MXI model Gouy magnetic balance.
UV-Vis spectra were obtained for the aqueous solutions of the complexes
with a Unicam UV2 spectrometer in the range 900–190 nm. IR spectra
were recorded in the 4000–200 cm ꢀ 1 region with a Mattson 1000 FT-IR
spectrometer using KBr pellets. Thermal analysis curves (TG-DTG and
DTA) were recorded simultaneously in a static air atmosphere with a Ri-
gaku TG8110 thermal analyser. The heating rate was 10 °C min ꢀ 1 and the
DTG sensitivity was 0.05 mg s ꢀ 1
.
Synthesis of [M(sac)2(H2O)4]ꢁ2H2O Complexes
A solution of sodium saccharinate (1.025 g, 5 mmol) in distilled water
(50 mL) was added drop wise with stirring at 80 °C to a solution of
MSO4ꢁxH2O (2.5 mmol; M =Co(II), 0.703 g; Ni(II), 0.657 g; and Cu(II),
0.624 g; x = 7, 6, and 5, respectively) in distilled water (50 mL). The
mixture was stirred for 4 h at 80 °C and then cooled to room temperature.
The crystals formed were filtered and washed with 10 mL of cold distilled
water and dried in vacuo.[2]

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80
Yes¸ilel et al.
Synthesis of Mixed-Ligand Complexes
A solution of dmen or ndmen (0.176 g, 2 mmol) in distilled water (30
mL) was added drop-wise with stirring to a solution of [M(sac)2(H2O)4]ꢁ-
2H2O (1.0 mmol; M =Co(II), 0.531 g; Ni(II), 0.530 g; and Cu(II), 0.535 g) in
hot distilled water (50 mL). The solutions were heated to 80 °C in a
temperature-controlled bath and stirred for 4 h. The reaction mixture was then
cooled to room temperature. The crystals formed were filtered and washed
with 10 mL of cold distilled water and acetone and dried in vacuo. In the case
of the Co(II) complexes butanol was used as a solvent.
RESULTS AND DISCUSSION
Synthesis and Structures of the Complexes
The mixed-ligand complexes were prepared according to the following
equations:
MSO4 þ 2sacNa þ 6H2O ! ½MðsacÞ2ðH2OÞ4Š ꢁ 2H2O þ Na2SO4
½MðsacÞ2ðH2OÞ4Š ꢁ 2H2O þ 2dmen ! ½MðsacÞ2ðdmenÞ2Š þ 6H2O
ðM ¼ CoðIIÞ; NiðIIÞÞ
½CuðsacÞ2ðH2OÞ4Šꢁ2H2O þ 2dmen !½CuðH2OÞ2ðdmenÞ2ŠðsacÞ2 þ 4H2O
½MðsacÞ2ðH2OÞ4Š ꢁ 2H2O þ 2ndmen ! ½MðsacÞ2ðndmenÞ2Š þ 6H2O
ðM ¼ CoðIIÞ; NiðIIÞ; CuðIIÞÞ
Analytical results and the compositions of the complexes are listed
in Table 1. The complexes were synthesized in good yields and with
high purity. The results of elemental analyses show that two ligand mole-
cules have been incorporated into the M(II) saccharinates. The [Cu(H2O)2-
(dmen)2](sac)2 complex contains 2.0 water molecules per formula unit. The
presence of aqua ligand was confirmed by the IR spectra and the weight
loss and endotherms in the temperature range 68–148 °C in the TG and
DTA curves. The complexes have pseudooctahedral geometries with two

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Saccharinato Complexes
81

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82
Yes¸ilel et al.
dimethylethylenediamine molecules (dmen or ndmen) coordinated to the
metal ions as chelating ligands through their two N atoms and two
monodentate saccharinato ligands in the trans positions for the complexes
of the type [M(sac-O)2(dmen)2] (M = Co(II), Ni(II)), and [M(sac-
N)2(ndmen)2] (M =Co(II), Ni(I), Cu(II)), and two aqua ligands in the trans
positions for [Cu(H2O)2(dmen)2](sac)2. sac-O and sac-N means that the
saccharinato ligand is coordinated to the metal ions through the carbonyl
oxygen or the nitrogen atom, respectively. The elemental analysis data in
Table 1 confirm the proposed formulae of the complexes.
UV-Vis Spectra
The lmax values of the various absorption bands, Do values of d–d
transitions displayed by the complexes, assignment of d–d transitions, and
the effective magnetic moment values of the complexes are given in Table 2.
The assignments of the d–d transitions corresponded to an octahedral
coordination geometry of the metal ions and the values of the Do parameter
were found using Tanabe and Sugano diagrams.[22] The lmax values of the
absorption bands in the spectra of [Co(sac)2(dmen)2] and [Co(sac)2(ndmen)2]
Table 2. Electronic spectra and magnetic moments of the metal complexes.
Assignment
of d–d
transitions
lmax
(nm)
e
Do
meff
(B.M.)
Complex
(cm ꢀ 1M ꢀ 1
)
(cm ꢀ 1
)
4
[Co(sac)2(dmen)2]
368
513
–
863
131
–
4T1g ! T1g (P)
4
–
4T1g ! A2g
4.41
4
4T1g ! T2g
3
[Ni(sac)2(dmen)2]
366
600
900
563
41
24
23
96
3A2g ! T1g (P)
3
3A2g ! T1g (F)
2.82
1.49
3
11,110
17,760
3A2g ! T2g
2
[Cu(H2O)2(dmen)2]-
(sac)2
[Co(sac)2(ndmen)2]
2Eg ! T2g
4
375
518
–
242
157
–
4T1g ! T1g (P)
4
–
4T1g ! A2g
4.65
4
4T1g ! T2g
3
[Ni(sac)2(ndmen)2]
[Cu(sac)2(ndmen)2]
371
611
900
565
33
25
3A2g ! T1g (P)
3
3A2g ! T1g (F)
3.02
1.45
3
22
164
11,110
17,700
3A2g ! T2g
2
2Eg ! T2g

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Saccharinato Complexes
83
are 368, 513 and 375, 518 nm, respectively. These values were assigned to
4
4
4
the following d–d transitions: n3: T1g ! T1g (P); n2: 4T1g ! A2g. The n1:
4
4T1g ! T2g transition was not observed since n1 is of very low energy and
shifts to the IR region. The Do values for cobalt compounds could not be
calculated since Do = n2 ꢀ n1 for d7 complexes. The lmax values of
[Ni(sac)2(dmen)2] and [Ni(sac)2(ndmen)2] are 366, 600, 900 and 371, 611,
3
910 nm, respectively. These values were assigned to n3: 3A2g ! T1g (P); n2:
3
3
3
3A2g ! T1g (F), and n1: A2g ! T2g d–d transitions. The Do values for
[Ni(sac)2(dmen)2] and [Ni(sac)2(ndmen)2] were calculated as 11,110 cm ꢀ 1
since Do = n1 for d8 complexes. The lmax values of [Cu(H2O)2(dmen)2](sac)2
and [Cu(sac)2(ndmen)2] are 563 and 565 nm, respectively. These values
2
2
were assigned to the Eg ! T2g transition. The Do values for [Cu(H2O)2-
(dmen)2](sac)2 and [Cu(sac)2(ndmen)2] were calculated as 17,760 and 17,700
cm ꢀ 1, respectively, since there is only one transition for d9 complexes.
It is seen that the Do values increase from the Ni to the Cu–dmen and
ndmen complexes separately. The metal complexes are of the high-spin type
and paramagnetic. These values suggest octahedral coordination around the
metal ions.
FT-IR Spectra
The main IR group frequencies of the metal complexes are presented
in Table 3. The IR spectra of all the complexes resemble each other and
show the characteristic C =O and O = S= O absorption bands of the sac
moiety. The stretching modes of the carbonyl and sulfonyl groups are used
most frequently for structural studies of various saccharinates.[5,6,21] The
coordination mode of the saccharin entities in the complexes is reflected in
the stretching frequencies of the carbonyl groups, the respective band(s)
being blue-shifted for N-coordination and red-shifted for O-coordination
relatively to the saccharin ion.[4] Strong absorption bands in the range of
1615–1638 cm ꢀ 1 characterize the C =O group of the sac moiety in the
complexes. These vibrational frequencies are lower than in saccharin itself
(1725 cm ꢀ 1) owing to the partially ionic character of the M–sac bond, the
lowering being dependent on the bond ionicity.[8,21] The existence of only
one carbonyl stretching band in the spectra of the complexes would indicate
the existence of a single type of saccharinato ligand, although this corre-
lation is not always straightforward. The strong band at 1623 cm ꢀ 1 as-
signed to the CO stretching vibration in [Cu(H2O)2(dmen)2](sac)2 is shifted
to 1615 and 1618 cm ꢀ 1 for [Co(sac)2(dmen)2] and [Ni(sac)2(dmen)2], res-
pectively. This fact can be attributed to the O-coordination of the sac ligand
in the Co(II) and Ni(II) complexes. For [Co(sac)2(ndmen)2], [Ni(sac)2-

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84
Yes¸ilel et al.
Table 3. FT-IR spectraa of the metal complexes.
Vibrational frequency (cm ꢀ 1
)
Complex
n(NH)
n(NH2) n(C = O) nas(SO2) ns(SO2) nr(CH2)
[Co(sac)2(dmen)2]
[Ni(sac)2(dmen)2]
3343 w
3311 m
–
1615 vs 1285 vs 1155 vs 856 m
1618 vs 1287 vs 1157 vs 863 m
1623 vs 1266 vs 1146 vs 864 m
–
–
[Cu(H2O)2(dmen)2]- 3348 m
(sac)2
[Co(sac)2(ndmen)2]
[Ni(sac)2(ndmen)2]
[Cu(sac)2(ndmen)2]
–
–
–
3336–
1638 vs 1265 vs 1148 vs 854 m
1632 vs 1289 vs 1155 vs 892 m
1630 vs 1276 vs 1146 vs 899 m
3250 m
3329–
3249 s
3323–
3245 m
aAbbreviations: m-medium; w-weak; s-strong; vs-very strong.
(ndmen)2] and [Cu(sac)2(ndmen)2] this vibration is larger than 1623 cm ꢀ 1
(1638, 1632 and 1630 cm ꢀ 1, respectively) as a result of coordination of the
sac ligand via the nitrogen atom. The saccharin behaves as the O- and N-
bonded ligand, and the counter-ion in the outer-sphere of the mixed-ligand
saccharin complexes.[13,14,16]
The frequencies of the SO2 stretching vibrations in metal saccharinates
are also lower than that of the saccharin molecule.[8] The frequencies of the
nas(SO2) and the ns(SO2) modes in the studied complexes range from 1289
to 1265 cm ꢀ 1 and from 1157 to 1146 cm ꢀ 1, respectively. These nas(SO2)
frequencies are by 66–90 cm ꢀ 1 lower than the corresponding mode in
saccharin itself (1355 cm ꢀ 1), while the lowering of the ns(SO2) frequencies
is 23–34 cm ꢀ 1 as compared to the value of 1180 cm ꢀ 1 in saccharin. The
frequency of the antisymmetric SO2 stretching vibration is more sensitive to
external influences than the symmetric SO2 mode.[21]
The vibrational frequencies of the CH2 groups in the dmen and ndmen
ligands of the complexes range from 899 to 854 cm ꢀ 1 and are in
agreement with coordinated ethylenediamine in the complexes.[5] The M–N
stretching frequencies of the studied complexes were observed in the range
of 484–460 cm ꢀ 1
.
The symmetric and asymmetric stretching vibration of the NH2
groups of ndmen occurred at 3336–3245 cm ꢀ 1 in the ndmen complexes,
whereas the stretching vibrations of the secondary amine ligands appeared
at 3348–3311 cm ꢀ 1 in the dmen complexes, as expected.
The IR spectrum of [Cu(H2O)2(dmen)2](sac)2 has an additional strong
and sharp band at 3553 cm ꢀ 1 which is assigned to n(OH) of the aqua ligand.

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Saccharinato Complexes
85
Thermal Properties
[M(sac)2(dmen)2] (M = Co(II), Ni(II)) and [Cu(H2O)2(dmen)2](sac)2
Complexes
The Co(II) and Ni(II) complexes are thermally stable up to about 200
and 252 °C, respectively, and decompose in five steps as shown by DTG.
Thermal analysis curves of Co(II) complex are given in Figure 2 as an
example. The first weight loss (WL) decomposition stages of these com-
plexes, in the range of 200–246 °C for the Co(II) complex and 252–277 °C
for the Ni(II) complex, are exothermic and related to the decomposition of
the neutral dmen ligands. This type of behavior of neutral ligands has been
reported earlier.[20] These WL processes were also verified by the IR
spectra. The IR spectra of the intermediate products formed in the 250 and
280 °C interval for the Co(II) and Ni(II) complex, respectively, showed that
the intensity of the vibration bands of CH2 and NH groups of the dmen
ligand decreased. The second WL process of the two complexes is en-
dothermic and related to the partial decompositions of the ionic sac ligand.
The IR spectrum of the intermediate product obtained in this step showed
that the saccharinato ligand decomposes to release SO2. Furthermore, the IR
spectra of the intermediate products formed in the 416–462 °C interval are
similar. The third WL process of the Co(II) complex and the fourth WL
process of the Ni(II) complex are exothermic and the values of DTGmax are
534 and 465 °C, respectively. The strong exothermic peaks are associated
with the burning of the organic residue, characteristic for the decomposi-
tion of sac complexes[19] and leading finally to the corresponding metal
Figure 2. DTA, TG, and DTG curves of [Co(sac)2(dmen)2].

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86
Yes¸ilel et al.
oxides. The endothermic peak at 913 °C is related to the conversion of
Co3O4 to CoO.
The Cu(II) complex included 2 molecules of water which makes it
different from the Co(II) and Ni(II) complexes, exhibiting five steps of
decompositions. The first WL process, in the temperature range 74–125 °C,
corresponds to the loss of 2.0 moles of aqua ligands in a single step and the
frequency of the CO vibration of the Cu(II) complex (1623 cm ꢀ 1) is
shifted to 1628 and 1654 cm ꢀ 1. The vibration at 1628 cm ꢀ 1 is indicative
of the saccharin ion outside of the coordination sphere, while the vibration
at 1654 cmꢀ 1 is indicative of the N-coordinated saccharinato ligand. The
anhydrous Cu(II) complex is thermally stable up to 197 °C and begins to
decompose with melting at 216 °C (DTA curve). This complex behaviour
was not observed for the other two complexes. Probably, one mol of dmen
ligand is removed (exp. weight loss is 13.75% which is close to the
calculated weight loss of 13.96%) and the geometry of the Cu(II) complex
changes from octahedral to square-planar at this stage. This second stage
consists of three overlapping thermal steps and the DTGmax values of these
steps are 208, 228 and 249 °C. In the endothermic third and exothermic
fourth stages (DTGmax =380 and 481 °C, respectively), one mole of dmen
and two moles of sac ligands are removed and the final decomposition
product is CuO.
Based on the initial DTGmax temperatures, the thermal stabilities of the
dmen complexes follow the sequence: Cu(II); 97 °C >Co(II); 233 °C >
Ni(II); 266 °C.
[M(sac)2(ndmen)2] Complexes (M = Co(II), Ni(II), Cu(II))
The Co(II) and Ni(II) complexes are thermally stable up to about 220
and 270 °C, respectively. The decomposition of the ndmen ligand at the
first step is exothermic for the two complexes [DTGmax =245 °C for Co(II)
and 288 °C for Ni(II)]. The characteristic exothermic decomposition pro-
cess of the sac ligand takes place at 533 and 486 °C (DTGmax) for the
Co(II) and Ni(II) complexes, respectively.
The Cu(II) complex is thermally stable up to 171 °C and begins to
decompose with melting at 177 °C (DTA curve). The DTGmax values of
the successive processes in the second WL stage are 302, 333 and 377 °C.
The WL process at 486 °C (DTGmax) is highly exothermic and CuO is
found to be the final decomposition product. The final decomposition
products, namely CoO, NiO and CuO, were identified by IR spectroscopy
with the corresponding spectra obtained under the same conditions as the
pure oxides.

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Saccharinato Complexes
87
O
N
O
S
C
O
O
S
C
H
O
N
CH3
O
N
H
H3C
H
H
H3C
CH3
N
N
N
N
N
CH2
CH2
H2C
H2C
M
CH2
H2C
H2C
M
CH2
N
N
H
CH3
H
H3C
O
C
H3C
CH3
H
C
H
O
N
S
O
N
O
S
O
O
[M(sac)2(dmen)2]
(M=Co(II), Ni(II))
[M(sac)2(ndmen)2]
(M=Co(II), Ni(II), Cu(II))
H
H
H
O
CH3
H3C
H
O
C
N
N
N
N
CH2
CH2
H2C
H2C
Cu
O
N
S
O
O
H
H
CH3
H
H
H3C
2
[Cu(H2O)2(dmen)2](sac)2
Figure 3. Suggested structures of the complexes.

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Yes¸ilel et al.
Based on to the initial DTGmax temperatures, the thermal stabilities
of the ndmen complexes follow the sequence: Cu(II); 191 °C> Co(II);
245 °C >Ni(II); 288 °C.
It is evident that the thermal stability sequences of the dmen and
ndmen complexes are the same; however, the thermal stabilities of the
ndmen complexes are higher than those of the dmen complexes. This
stability behaviour can be attributed to the ligand basicity.[23] This stability
difference between the dmen and ndmen complexes was not observed
clearly in the spectroscopic studies.
The structures of the synthesized complexes which are presented
Figure 3, are consistent with the chemical, thermal and spectroscopic pro-
perties which were determined.
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Received June 12, 2001
Accepted September 3, 2002
Referee I: M. M. Jones
Referee II: S. J. Slattery