VIKRAM et al.
–
000–400 cm . The room temperature magnetic sus-
1
–1 –1
about 13000 cm for CuO to about 18000 cm for
4
ceptibility measurements were carried out with a
6
CuN [13]. The copper(II) complex reported here
6
–
1
Gouy balance using Hg[Co(SCN) ] as a calibrant.
4
shows a d–d transition around 14200 cm which
shows the involvement of nitrogen and oxygen donor
sites in coordination.
The solid state electronic absorption spectra of the
complexes in Nujol mull were recorded on a
Shimadju UV-vis 240 A spectrophotometer in the
range 200–800 nm.
The infrared spectra of hydrazinium metal sulfite
dihydrates are similar to that of sulfate complexes.
These complexes show a band in the region
The simultaneous TG-DTA of the complexes in
air were carried out using a STA 1500 system. The
thermal experiments in nitrogen atmosphere were
also carried out for comparison. The heating rate em-
–
1
990–1000 cm for N–N stretching of coordinated
ions [16]. The presence of bidentate and bridg-
ing sulfite ions [17] are shown by the broadening and
N H
2 5
–
1
–1
ployed was 10°C min and aluminium cups were
used to hold about 5–10 mg of the sample.
splitting of bands in the region 1000–1200 cm .
These complexes showed three or four bands in the
–
1
region 3200–3500 cm indicating the presence of
both N–H and O–H stretching of N H or H O groups.
2
5
2
Results and discussion
Thermal degradation
Hydrazinium metal sulfite dihydrates were prepared
by either decomposing the respective anhydrous
metal hydrazinecarboxylates in aqueous solution con-
taining sulfur dioxide gas or by the aqueous reaction
between hydrazinium sulfite monohydrate and re-
spective metal nitrate hydrates. These complexes are
insoluble in water, alcohol and other organic solvents
and decompose in dilute acids with the liberation of
sulfur dioxide which is the characteristic reaction of
metal sulfites. The composition of the complexes, on
the basis of metal and hydrazine analyses, were as-
signed as (N H ) M(SO ) (H O) where M=Fe, Co,
2 5 2 3 2 2 2
Ni, Cu and Zn (Table 1).
The room temperature magnetic moments of iron,
cobalt, nickel and copper complexes are found to be
5.32, 5.02, 3.45 and 1.95, respectively, which indicate
the high spin octahedral nature of these metal ions
The iron complex decomposes in air in a single step in
the temperature range 200–300°C as shown by the
TG curve to give the mixture of ferrous sulfate and
ferric oxide as the residues. The DTA shows a doublet
at 260 and 280°C. The TG mass loss corresponds to
the product in 1:1 ratio.
The hydrazinium cobalt sulfite dihydrate shows
multi-step decomposition. The first stage is dehydra-
tion in the temperature range 30–80°C showing the
non-coordination of water molecules. DTA shows an
endotherm at 52°C corresponding to this dehydration.
The mass loss is found to be 12% which is in accor-
dance with the theoretical mass loss. Then the anhy-
drous complex decomposes in four stages to give co-
balt sulfate as the final product below 300°C. The in-
termediates proposed for these stages are given in the
Table 2. The DTA shows one endotherm and three
exotherms at 190, 227, 233 and 295°C, respectively.
The nickel complex undergoes dehydration in
two stages in the temperature range 50–165°C as
shown by TG curve. The DTA shows two endotherms
at 65 and 150°C for the dehydration. The anhydrous
complex undergoes decomposition slowly up to
525°C and then sharply between 525 and 570°C to
give nickel sulfate as the final residue. The DTA
curve shows a broad exotherm from 200–500°C and
then the sharp exotherm at 540°C, respectively.
[
10–12]. The zinc complex is diamagnetic as expected.
The electronic spectrum of iron(II) complex ex-
–
hibits a band at 11200 cm which is assigned to the
1
5
5
E ® T transition. The cobalt complex shows two
g
2g
–
1
–1
bands at 9400 cm and 19380 cm which are as-
4
signed to T (F)® T and T (F)® T (P) transi-
4
4
4
1
g
2g
1g
1g
tions, respectively [13]. The nickel complex exhibits
three bands characteristic of octahedral geometry at
–
0210 , 17670 and 27700 cm which are assigned to
1
1
3
3
3
3
3
3
A ® T , A ® T (F) and A ® T (P) transi-
2
g
2g
2g
1g
2g
1g
tions, respectively [14, 15]. The T ®E separation in
2
g
g
the regular octahedral copper(II) complex varies from
Table 1 Analytical data
Metal/%
found
Hydrazine/%
Complex
Colour
m
eff/B.M.
calc.
found
calc.
(N
2
(N
2
(N
2
(N
2
(N
2
H
5
H
5
H
5
H
5
H
5
)
)
)
)
)
2
2
2
2
2
Fe(SO
3
)
2
(H
(H
(H
(H
(H
2
O)
O)
O)
O)
O)
2
light green
pink
17.0
17.8
18.0
18.9
19.5
17.56
18.35
18.29
19.50
19.95
19.5
19.7
19.1
19.0
20.1
20.15
19.96
19.97
19.67
19.56
5.32
5.02
3.45
1.95
Co(SO
3
)
2
2
2
Ni(SO
3
)
2
2
2
green
Cu(SO
3
)
2
2
2
blue
Zn(SO
3
)
2
2
2
colourless
diamagnetic
522
J. Therm. Anal. Cal., 89, 2007