The synthesis of two new isonitrosoacetophenone derivatives and investigation of their ni(ii), Co(II), Cu(II), and Zr(IV) complexes

Article abstract of DOI:10.1134/S0036023612090124

In the present study, two new ligands, 4-chlorobenzal-azino- isonitrosoacetophenone (L₁), 4- methylbenzal-azino- isonitrosoacetophenone (L₂) and their metal complexes were synthesized using ace- tophenone as a starting material. The

Full text of DOI:10.1134/S0036023612090124

ISSN 0036ꢀ0236, Russian Journal of Inorganic Chemistry, 2012, Vol. 57, No. 9, pp. 1227–1231. © Pleiades Publishing, Ltd., 2012.
COORDINATION COMPOUNDS
The Synthesis of Two New Isonitrosoacetophenone Derivatives
and Investigation of Their Ni(II), Co(II), Cu(II),
and Zr(IV) Complexes1
Nuriye Koçaka, Mustafa Sahinb, and H. Ismet Ucanb
a Department of Science Education, Faculty of Education, Selcuk University, 42031, Konya Turkey
b Department of Chemistry, Faculty of Science, Selcuk University, Konya, 42075 Turkey
eꢀmail: nuriye42@gmail.com
Received March 29, 2010
Abstract—In the present study, two new ligands, 4ꢀchlorobenzalꢀazinoꢀisonitrosoacetophenone (L1), 4ꢀ
methylbenzalꢀazinoꢀisonitrosoacetophenone (L2) and their metal complexes were synthesized using aceꢀ
tophenone as a starting material. The coloured complexes were prepared by the addition of chloride salts of
Ni(II), Co(II), Cu(II) and Zr(IV) ions to a solution of ligands. In conclusion, the structures of the obtained
1
ligands and their complexes were characterized by FTꢀIR, and H NMR spectra, AAS (atomic absorption
spectrum) analysis, magnetic susceptibilities as well as elemental analysis.
DOI: 10.1134/S0036023612090124
1
Recently, due to the increasing use of the coordinaꢀ tural properties of ligands and their complexes were
investigated.
tion compound in analytical, bioinorganic, pigment
and medicinal chemistry, many researchers have studꢀ
ied these topics, especially, the important role of the
complexes of oximes in coordination chemistry [1–6].
Oximes and hydrazones are two important classes of
inorganic ligands owing to their wide application in
industry, medicine, detection and determination of
various metal ions [7, 8]. Schiff base hydrazone derivꢀ
atives and their complexes have been studied for their
antifungal and antibacterial activity, and as antiviral
drugs [9].
EXPERIMENTAL
All reagents were purchased from Merck and used
without further purification. Isonitrosoacetophenone
were prepared according to the procedures reported in
literature [1, 4]. 1H NMR spectra and elemental analyses
were carried out at laboratories of the Scientific and
Technical Research Council of Turkey (TUBITAK).
IR spectra were recorded on a PerkinꢀElmer 1605 FTꢀ
IR spectrophotometer as KBr pellets. pH of solutions
was monitored with a WTW 537 pH meter. Magnetic
Susceptibilities of metal samples were determined
using a Sheerwood Scientific MX Gouy magnetic susꢀ
ceptibility apparatus, and magnetic measurements
were carried out by the Gouy method using
Oximes are amphoteric materials containing weak
acidic –OH groups and basic >C=N– groups. Generꢀ
ally, the geometrical isomers of oximes and their derivꢀ
atives are syn and anti structures. However, 1,2–
dioximes have three isomers which are syn, anti and
amphi forms [10, 11], Usually, the stability order of
them is anti > amphi > syn configuration, but there are
some exceptions [12, 13]. The high stability of the
complexes prepared with vicꢀdioxime ligands has been
extensively used for various purposes including model
compounds for vitamin B12 or trace metal analysis.
The successful design and synthesis of ligands capable
of forming heteronuclear complexes has been receivꢀ
ing attention for their magnetic, optical and electrical
properties [14].
Hg Co(SCN)4] as calibrant. Metal contents in comꢀ
[
plexes were determined with a Unicamꢀ929 AAS
(atomic absorption spectrometer).
Synthesis of Isonitrosophenylhydrazine (Fig. 1). A
solution of isonitrosoacetophenone (2.98 g, 20 mmol)
in 20 mL of ethanol was added dropwise to a stirred
solution of hydrazinehydrate (4 g, 80 mmol) in 20 mL
of ethanol at –5 C followed by addition of acetic acid
(pH 8.5). Then the mixture was diluted with distilled
water and allowed to stand 2 days in the refrigerator.
°
The precipitate was filtered, dried in a vacuum at 65
and weighed 2.75 g in 77% yield, m.p. 114
1H NMR (DMSOꢀ
6, 300 MHz) : 5.92 (s, 2H),
= 7.3 Hz, 5H), 8.15 (s, 1H), 11.32 (s,
: 3460, 3000, 1640, 1610, 1460 cm–1
°
C
In the present study, two new imino oximes were
synthesized, and their complexes with Cu(II), Ni(II),
Co(II) and Zr(IV) ions were prepared. Besides, strucꢀ
°C;
d
δ
7.45–7.90 (m,
1H); IR (KBr)
J
ν
1
The article is published in the original.
.
1227

1228
KOÇAK et al.
then filtered, washed with distilled water, ethanol and
diethyl ether, and dried in vacuum at 60 . The prodꢀ
uct was obtained as a light green solid in 74% yield
NH2
N
°C
H+
O
+
NH2NH3OH
(0.092 g). m.p. 237
°
C
(with degradation); IR (KBr)
ν
:
.
3520, 2940, 1615, 1645, 1663, 1410, 960, 515, 430 cm–1
H
NOH
H
NOH
Anal. calcd. for C30H22Cl2N6O2Ni: C 57.36, H 3.52, N
13.37 Ni 9.34; found C 57.17, H 3.25, N 13.67 Ni 9.18.
Fig. 1. Synthesis of isonitrosophenylhydrazine.
Preparation of Cu(II) complex of L1. This comꢀ
pound was prepared by the procedure mentioned for
the preparation of (L1)2Ni. The product was obtained
Anal, calcd. for C8H9N3O: C 58.85, H 5.58, N 25.76;
found C 58.67, H 5.39, N 25.54.
as a green solid in 83% yield (0.105 g). m.p. 227 C
°
(with degradation); IR (KBr) : 3500, 2950, 1617,
ν
Synthesis of 4ꢀchlorobenzalꢀhydrazine (Fig. 2). To a
1645, 1665, 1465, 1000, 520, 440 cm–1. Anal. calcd.
for C30H22Cl2N6O2Cu: C 56.92, H 3.50, N 13.27 Cu
10.04; found C 56.62, H 3.39, N 13.06 Cu9.95.
stirred solution of hydrazinehydrate (1 g, 80 mmol) in
20 mL ethanol at –5 C was added dropwise to a soluꢀ
°
tion of pꢀchlorobenzaldehyde (2.8 g, 20 mmol) in
20 mL ethanol. Then the mixture was diluted with disꢀ
tilled water (20 mL) and allowed to stand two days in
the refrigerator. The precipitate was filtered, dried in a
Preparation of Co(II) complex of L1. Complexes of
L1 with Co(II) ion was prepared by the procedure
above mentioned for the preparation of (L1)2Ni. The
product was obtained as a grey solid in 78% yield
vacuum at 65
yield, m.p. 145oC; 1H NMR (DMSOꢀ
4.84 (s, 2H), 7.54–7.81 (m, = 8.4 Hz, 4H), 8.42 (s,
1H); IR (KBr)
: 3380, 3290, 1650, 1610, 760 cm–1
°C
and afforded 2.51 g of product in 81%
d6, 300 MHz) :
δ
(0.098 g). m.p. 214
°
C
(with degradation); IR (KBr) :
ν
J
3620, 2940, 1619, 1650, 1664, 1420, 975, 528, 435 cm–1
.
ν
.
Anal. calcd. for C30H22Cl2N6O4Co: C 57.34, H 3.53,
N 13.37 Co 9.38; found C 57.30, H 3.45, N 13.30,
Co 9.31.
Anal. calcd. for C7H7ClN2: C 54.36, H 4.57, N 18.13;
found C 54.22, H 4.46, N 17.95.
Synthesis of 4ꢀchlorobenzalꢀazinoꢀisonitrosoaceꢀ
tophenone (L1) (Fig. 3). 4–chlorobenzalhydrazine
(0.77 g, 5 mmol) was dissolved in 20 mL ethanol, then
a solution of isonitrosoacetophenone (0.69 g, 5 mmol)
in 20 mL ethanol was added dropwise to above soluꢀ
tion. After K2CO3 (0.69 g, 5 mmol) was added to reacꢀ
tion mixture, it was refluxed for 1 h. Then mixture was
left to cool to r.t. Distilled water was added to mixture
with stirring until precipitate was formed. After 2 h,
precipitated solid was filtered off, washed with water,
Preparation of Zr(IV) complex of L1. Complexes of
L1 with Zr(IV) ion was prepared by the procedure
above mentioned for the preparation of
product was obtained as a yellow solid in 89% yield
(0.118 g). m.p. 269 (with degradation); IR (KBr)
3500, 2960, 1618, 1640, 1670, 1460, 950, 535, 420 cm–1
(L1)2Ni. The
°C
ν:
.
Anal. calcd. for C30H22Cl2N6O2ZrCl2: C 49.25,
H 3.03, N 11.49, Zr 12.47; found C 49.00, H 2.97,
N 11.50 Zr 12.35.
dried in vacuum at 65 C and afforded 0.90 g of prodꢀ
°
Synthesis of 4ꢀmethylbenzalꢀazinoꢀisonitrosoaceꢀ
tophenone (L2) (Fig. 4). A solution of isonitrosopheꢀ
nylhydrazine (0.815g, 5 mmol) in 20 mL of ethanol
was added slowly to a solution of 4ꢀmethylbenzaldeꢀ
hyde (0.6 g, 5 mmol) in 20 mL of ethanol. The mixture
was refluxed for 1 h and then diluted with distilled
water. The mixture was stirred for 2 h and precipitate
was filtered, washed with water, dried in vacuum at
uct as a light yellow solid in 63% yield. The final prodꢀ
uct was soluble in dioxane, chloroform, diethylether
and DMF. m.p. 209
300 MHz) : 7.08–8.29 (m,
°
C; 1H NMR (DMSOꢀd6
,
δ
J
= 8.2 Hz, 9H), 8.58 (s,
: 3560,
1H), 8.77 (s, 1H), 11.65 (s, 1H); IR (KBr)
ν
3020, 1612, 1642, 1656, 1470, 920 cm–1. Anal. calcd.
for C15H12ClN3O: C 63.05, H 4.23, N 14.70; found
C 62.86, H 3.99, N 14.59.
60–70 C. The final product was weighed 1.06 g as a
°
Preparation of Ni(II) complex of L1: 4ꢀchlorobenzalꢀ yellow solid in 80% yield. The final product was soluꢀ
azinoꢀisonitrosoacetophenone (0.057 g, 0.2 mmol) was ble in ethanol, chloroform, acetone, DMSO, and
1
dissolved in 20 mL of dioxane. Then, 10 mL of aqueꢀ DMF. m.p. 133
ous solution of NiCl2 6H2O (0.12 g, 0.5 mmol) was
°
C; H NMR (DMSOꢀ
d
6, 300 MHz)
= 7.7 Hz, 9H), 9.34
: 3440
⋅
δ
: 2.50 (s, 3H), 7.06–8.80 (m,
J
added dropwise to above solution by stirring. The pH (s, 1H), 9.57 (s, 1H), 12.16 (s, 1H); IR (KBr)
ν
,
of the reaction mixture was adjusted to 5.0–5.5 by 3000, 1610, 1635, 1660, 1460, 975 cm–1. Anal. calcd.
adding an aqueous solution of NaOH (1%, wt). Precipiꢀ for C16H15N3O: C 72.43, H 5.69, N 15.83; found
tated solid was kept on a water bath at 60°C for 30 min, C 72.29, H 5.48, N 15.45.
+
NH2NH3OH
Cl
CHO
Cl
N NH2
Fig. 2. Synthesis of 4ꢀchlorobenzalꢀhydrazine.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 57 No. 9 2012

THE SYNTHESIS OF TWO NEW ISONITROSOACETOPHENONE DERIVATIVES
1229
Cl
+
O
N
N NH2
N
H
NOH
H
NOH
Cl
Fig. 3. Synthesis of 4ꢀchlorobenzalꢀazinoꢀisonitrosoacetophenone (L ).
1
NH2
+
H3C
CHO
N
N
N
H
NOH
H
NOH
CH3
Fig. 4. Synthesis of 4ꢀmethylbenzalꢀazinoꢀisonitrosoacetophenone (L ).
2
Preparation of Ni(II) complex of L2. 4ꢀmethylbenzalꢀ N 14.30 Ni 9.99; found C 65.28, H 4.66, N 14.12
Ni 9.96.
azinoꢀisonitrosoacetophenone (0.052 g, 0.2 mmol) was
dissolved in 20 mL of ethanol. Then, 10 mL of aqueꢀ
ous solution of NiCl2 · 6H2O (0.12 g, 0.5 mmol) was
added dropwise to above solution by stirring. The pH
of the reaction mixture was adjusted to 5.0–5.5 by
adding an aqueous solution of NaOH (1%, wt). Precipiꢀ
Preparation of Cu(II) complex of L2. Complexes of
L2 with Cu(II) ion was prepared by the procedure
above mentioned for the preparation of (L2)2Ni. The
product was obtained as a green solid in 83% yield
(0.096 g). m.p. 228
°C
(with degradation); IR (KBr) :
ν
3490, 2920, 1614, 1630, 1663, 1490, 980, 530, 448 cm–1
.
tated solid was kept on a water bath at 60
then filtered, washed with distilledꢀwater, ethanol and
diethyl ether, and dried in vacuum at 60 . The prodꢀ
uct was obtained as a pale red solid in 90% yield (0.104 g).
°C for 30 min,
Anal. calcd. for C32H28N6O2Cu: C 64.90, H 4.76,
N 14.19 Cu 10.73; found C 64.66, H 4.57, N 13.95,
Cu 10.70.
°C
m.p. 198
°
C
(with degradation); IR (KBr)
ν
: 3440
,
;
Preparation of Co(II) complex of L2. Complex of L2
with Co(II) ion was prepared by the procedure above
2900, 1612, 1640, 1665, 1420, 900, 536, 450 cm–1
Anal. calcd. for C32H28N6O2Ni: C 65.44, H 4.80, mentioned for the preparation of (L2)2Ni. The product
Table 1. Magnetic moment and the FTꢀIR spectral data of ligands and their metal complexes (cm–1) (KBr pellets)
C=Na C=Nb C=Nc
B.M.d
–
Compounds O–H
C–H (ar)
C–H (aliph) N–O
M–N
M–O
L1
–
–
–
–
3020
2940
1612
1615
1642
1645
1656
1663
1470
1410
920
960
–
–
1 Ni
515
430
Dia
L2
1 Cu
2950
2940
1617
1619
1645
1650
1665
1664
1465
1420
1000
975
520
528
440
435
1.90
2.43
L2
1 Co
L2
1 ZrCl2
–
Weak
3000
2900
1618
1610
1612
1640
1635
1640
1670
1660
1665
1460
1460
1420
950
975
900
535
–
420
–
Dia
–
L2
L2
3240
2 Ni
–
–
–
536
450
Dia
L2
2 Cu
2920
2940
2920
1614
1620
1618
1630
1645
1640
1663
1666
1670
1490
1490
1450
980
960
950
530
540
538
448
442
445
1.85
2.65
Dia
L2
2 Co
L2
2 ZrCl2
–
L2
a
Oxime (C=N).
Azomethine (C=N).
Azine (C=N).
b
c
d
Magnetic moment per metal atom.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 57 No. 9 2012

1230
KOÇAK et al.
X
X
N
N
Cl
Zr
Cl
O N
H
O N
H
M
H
N O
H
N O
N
X
N
X
square plane
octahedral
R
X =
N
R = Cl, CH3
M = Cu(II), Ni(II), Co(II)
Fig. 5. The suggested geometries of complexes.
was obtained as a brown solid in 91% yield (0.105 g). hyde and 4ꢀmethylbenzaldehyde. These compounds
m.p. 233
°
C
(with degradation); IR (KBr)
ν
: 3620
,
are derivatives of Schiff base and oxime. Transition
2940, 1620, 1645, 1666, 1490, 960, 540, 442 cm–1. Anal. metal complexes of them with Cu(II), Ni(II), Co(II)
calcd. for C32H28N6O2Co: C 65.41, H 4.80, N 14.30 and Zr(IV) ions were prepared. Structures of ligands
Co 10.03; found C 64.94, H 4.70, N 14.08, Co 9.97.
and their complexes were confirmed by IR, 1H NMR
spectra AAS and elemental analysis as well as physical
methods.
Preparation of Zr(IV) complex of L2. Complex of L2
with Zr(IV) ion was prepared by the procedure above
mentioned for the preparation of (L2)2Ni. The product
was obtained as a yellow solid in 92% yield (0.112 g).
In the IR spectra of the ligands (Table 1), C=Na
stretching in L2 was appeared at region of 1610 cm–1
,
while C=Na stretching in L1 at 1612 cm–1. C=Nb
stretching in L2 were appeared at region of 1635 cm–1
m.p. 189
°
C
(with degradation); IR (KBr) : 3500,
ν
2920, 1618, 1640, 1670, 1450, 950, 538, 445 cm–1. Anal.
calcd. for C32H28N6O2ZrCl2: C 55.64, H 4.09,
N 12.17, Zr 13.21; found C 55.60, H 4.05, N 12.13,
Zr 13.19.
,
while C=Nb stretching in L1 at 1642 cm–1. In the IR
spectra of the ligands, C=Nc stretching in L2 were
appeared at region of 1660 cm–1, while C=Nc stretchꢀ
ing in L1 at 1656 cm–1. O–H and C–H (ar) stretchings
in L2 give sharp peaks. Due to the existence of chloride
group bound to benzene ring in Li, peaks of O–H and
C–H (ar) interfere with each other. C–H (ar) frequenꢀ
cies range from 3000 to 3200 cm–1. O–H frequencies
RESULTS AND DISCUSSION
In this study, acetophenone was used as a starting
material. Isonitrosoacetophenone was prepared
according to published methods [1, 4]. Isonitrosopheꢀ
nylhydrazine was prepared by the coupling reaction of
isonitrosoacetophenone with hydrazine hydrate.
Then, 4ꢀchloroꢀbenzalꢀazinoꢀisonitrosoacetopheꢀ
none (L1) and 4ꢀmethylꢀbenzalꢀazinoꢀisonitrosoaceꢀ
tophenone (L2) were synthesized from the reaction of
isonitrosophenylhydrazine with 4ꢀchlorobenzaldeꢀ
belonging to oxime were appeared at 3400–3620 cm–1
.
These values are in agreement with literature [21]. In
the IR spectra of the complexes, Cu(II), Ni(II) and
Co(II) complexes demonstrated weaker C=N absorpꢀ
tion than that of the ligands and no changes in N–O
bonds. In all complexes, the bands in the region of
534–461 and 461–420 cm–1 can be attributed to the
M–N and M–O stretching modes [15].
The magnetic susceptibility of the complexes
(Table 1) was measured at room temperature. The
magnetic moments of the nickel(II) complex of the L1
and L2 have got four coordination of d8 configuration
and the diamagnetic nature of the compounds shows
that it acquires an square planner structure [16]. It has
been observed that the complexes of Co(II) and
Cu(II) have got paramagnetic properties. The magꢀ
neticness of the Co(II) complexes having d7 configuꢀ
ration was measured and found as 2.35–2.65 B.M. These
1
Table 2. Data of the H NMR spectra of the ligands in
DMSOꢀd6
(δ, ppm)
Comꢀ
pounds
O–Ha C–H* C–H*
H (ar)
CH3
–
L1
11.65
8.77
8.58
7.08–8.29
m (10H)
s (1H) s (1H) s (1H)
L2
12.16 9.57 9.34
s (1H) s (1H) s (1H)
7.06–8.80
m (10H) s (3H)
2.50
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 57 No. 9 2012

THE SYNTHESIS OF TWO NEW ISONITROSOACETOPHENONE DERIVATIVES
1231
3. J. V. Burakevich, A. M. Lore, and G. P. Volpp, J. Org.
Chem. 36 (5), 1 (1971).
4. H. I. Ucan and R. Mirzaoglu, Synth. React. Inorg.
Met.ꢀOrg. Chem. 20 (4), 437 (1990).
5. I. Karatas, H. I. Ucan, and G. Irez, Synth. React.
Inorg. Met.ꢀOrg. Chem. 28 (33), 1 (1998).
6. A. Gul and O. Bekaroglu, J. Chem. Soc. Dalton Trans.,
No. 20, 2537 (1983).
values are within the normal range (2.20–2.70 B.M.)
reported for square planar geometry [17]. The magꢀ
neticness of the Cu(II) complexes having d9 configuꢀ
ration was measured and found as 1.83–1.90 B.M.
These data show that the complexes has a square planꢀ
ner structures [18]. The magnetic moment of comꢀ
plexes of the Zr(IV) has got diamagnetic properties and
shows that it acquires an octahedral structure [19]. These
data are in agreement with the literature [2, 20–22].
7. H. I. Ucan and I. Karatas, Synth. React. Inorg. Met.ꢀ
Org. Chem., 23, 1781 (1993).
The synthesized ligands have been characterized
1
8. R. Gup and B. Kirkan, Spectrochim. Acta Pt. A 62
,
using H NMR (Table 2) spectroscopy. Chemical
1188 (2005).
shifts of O–H groups in L1 and L2 were appeared at
11.65 and 12.16 ppm, respectively. The chemical shift
changes result from the effects of the electronꢀwithꢀ
drawing and donating of substituents. Due to the existꢀ
ence of chlorine group in L1 signal of O–H is shifted.
Likewise, the downfield shift of O–H signal in L2 is
due to the existence of methyl group. Two different
9. F. J. BarrosꢀGarcia, A. BernalteꢀGarcia, F. Lunaꢀ
Giles, et al., Polyhedron 24 (10), 1125 (2005).
10. P. A. S. Smith, The Chemistry of OpenꢀChain Organic
Nitrogen Compounds (New York, 1966), pp. 29–68.
11. A. N. Nesmeyanov and N. A. Nesmeyanov, Fundamenꢀ
tal of Organic Chemistry, 2nd ed. (1976), II, p. 167.
12. S. Serin and O. Bekaroglu, Anorg. Allgem. Chem. 496
C⎯H signals were observed in two ligands. Proton sigꢀ
(1), 197 (1983).
nal of C–H adjacent to benzene ring bound methyl
group in L2 is more obvious than that of oxime group.
Aromatic protons in ligands were appeared at approxꢀ
imately expected regions. The chemical shift of
methyl substituent in L2 was observed at 2.5 ppm as a
singlet. Also, peaks at 11–12 ppm were disappeared
when the ligands were treated with D2O. This show
that these values belong to protons of O–H.
1H NMR spectra of complexes could not be taken
because they have not good solubility in common organic
solvents. Thus, their structures were confirmed by IR
spectra, AAS and elemental analysis. As seen from the
results, it was determined that coordination geometries of
complexes are square plane and octahedral. The sugꢀ
gested structures are given in Fig. 5.
13. I. Karatas, G. Irez, M. Sezgin, et al., Synth. React.
Inorg. Met. Org. Chem. 21 (6–7), 1031 (1991).
14. C. Celik, Z. Ulukanli, M. Tumer, and S. Serin, Specꢀ
trosc. Lett. 36 (1–2), 51 (2003).
15. M. Tumer, H. Koksal, M. K. Sener, and S. Serin, Trans.
Met. Chem. 24 (4), 414 (1999).
16. K. S. Bharathi, A. K. Rahiman, K. Rajesh, et al., Polyꢀ
hedron 25 (15), 2859 (2006).
17. D. Kumar, P. K. Gupta, and A. Syamal, J. Chem. Sci.
117 (3), 247 (2005).
18. M. ElꢀBehery and H. ElꢀTwigry, Spectrochim. Acta,
Pt. A 66 (1), 28 (2007).
19. C. L. Liang, C. W. Yang, M. Y. Chiang, et al., J. Orgaꢀ
nomet. Chem. 679 (1), 135 (2003).
·
20. A. Hüseyinzade and G.
I
rez, Synth. React. Inorg.
Met.ꢀOrg. Chem. 21 (2), 301 (1991).
21. M. Sahin, N. Koçak, H. I., Uçan and M. Deveci, Russ.
J. Coord. Chem. 33 (9), 680 (2007).
22. A. N. Sing, R. P. Sing, J. G. Mohanty, and A. Chakraꢀ
REFERENCES
1. L. Tschugaeff, Ber. 40, 3498, (1907).
2. A. Chakravorty, Coord. Chem. Rev. 13 (1), 46 (1974).
vorty, Inorg. Chem. 16, (10), 2597 (1977).
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 57 No. 9 2012