Mixed ligand complexes of nickel (II) dialkyldithiophosphates with 2-acetylpyridine semicarbazone and 2-acetylpyridine benzoylhydrazone

Article abstract of DOI:10.1080/10426500307924

Dialkyldithiophosphates nickel (II) complexes react with Apsc and HApBH to yield mixed ligand complexes of the types [Ni{(RO)₂PS₂}₂(Apsc)] and [Ni{(RO)₂PS₂}(ApBH)] where R = methyl, ethyl or propyl; A

Full text of DOI:10.1080/10426500307924

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Mixed Ligand Complexes of Nickel (II)
Dialkyldithiophosphates with 2-Acetylpyridine
Semicarbazone and 2-Acetylpyridine Benzoylhydrazone
Amna S. A. Zidan a
a Assiut University , Assiut, Egypt
Published online: 27 Oct 2010.
To cite this article: Amna S. A. Zidan (2003) Mixed Ligand Complexes of Nickel (II) Dialkyldithiophosphates with 2-
Acetylpyridine Semicarbazone and 2-Acetylpyridine Benzoylhydrazone, Phosphorus, Sulfur, and Silicon and the Related
Elements, 178:3, 567-582
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Phosphorus, Sulfur and Silicon, 2003, Vol. 178:567–582
C
Copyright 2003 Taylor & Francis
1042-6507/03 $12.00 + .00
DOI: 10.1080/1042650039017023
MIXED LIGAND COMPLEXES OF NICKEL (II)
DIALKYLDITHIOPHOSPHATES WITH
2-ACETYLPYRIDINE SEMICARBAZONE AND
2-ACETYLPYRIDINE BENZOYLHYDRAZONE
Amna S. A. Zidan
Assiut University, Assiut, Egypt
(Received May 10, 2002; accepted August 12, 2002)
Dialkyldithiophosphates nickel (II) complexes react with Apsc
and HApBH to yield mixed ligand complexes of the types
[Ni{(RO)2PS2}2(Apsc)] and [Ni {(RO)2PS2}(ApBH)] where R = methyl,
ethyl, or propyl; Apsc = 2-Acetylpyridine semicarbazone; HApBH = 2-
Acetylpyridine benzoylhydrazone. From the elemental analysis and UV,
IR, and mass spectra the composition and structures of the complexes
and the ligand (HApBH) were determined. TG and DTG techniques
were used to investigate the thermal behavior of HApBH and the com-
plexes. The IR spectra show that Apsc acts in a neutral bidentate fashion
and HApBH behaves in all cases as a mononegative tridentate ligand.
The electronic spectral data suggest an octahedral structure of these
complexes. Also the biological activity for some of the complexes and
HApBH was recorded against some bacteria and fungi. The HApBH
ligand has a high toxicity against bacteria and fungi under study; this
may be due to presence of the pyridyl ring and hydroxyl group of the
compound.
Keywords: 2-Acetylpyridine benzoylhydrazone; 2-acetylpyridine semi-
carbazone; mixed ligand complexes; nickel (II) dialkyldithiophos-
phates; spectroscopic characterization; thermal analysis
INTRODUCTION
Semicarbazones and hydrazones are very biologically active and most
importantly, nitrogen/oxygen donor ligands. The activity increases on
5
complexation with metal ions.1
The real impetus for developing
the coordination chemistry of these potential ligands was probably
Address correspondence to Amna S. A. Zidan, Chemistry Department, Faculty of
Science, Assiut University, Assiut, Egypt. E-mail: amna@aun.edu.eg
567

568
A. S. A. Zidan
provided by the remarkable antiviral,6 antimalarial, and antituberculo-
sis effects.7 9 The antituberculous activity of hydrazides was described
for their ability to form more or less stable chelates with the transition
metal ions.10
The reaction of arylhydrazones with transition metal ions can pro-
ceed according to two pathways attaining the ketonic (I) or enolic (II)
structure for the hydrazide part of the molecule.
The mode of bonding was found to depend on the nature of both the
ligand and metal ions.11,12
Moreover, the dialkyldithiophosphates are biologically important13
and later used as antioxidant on vegetable oil for lubricant
application.14 In continuation of our previous studies on mixed lig-
and complexes of nickel (II) dialkyldithiophosphates with nitrogen
donor ligands,15 we describe here the synthesis, spectral and ther-
mal analyses, and mass spectra of some mixed ligand complexes of 2-
acetylpyridine semicarbazone and 2-acetylpyridine benzoylhydrazone
with bis (dialkyldithiophosphato) Ni(II).

Mixed Ligand Complexes of Nickel (II) Dialkyldithiophosphates
569
EXPERIMENTAL
All chemicals were of analytical grade; hydrazine hydrate, 2-acetyl-
pyridine, and semicarbazide hydrochloride were Merck grade. They
were used without further purification.
Bis (dialkyldithiophosphato) nickel (II),16 benzoylhydrazine,17 and
2-acetylpyridine semicarbazone5 were prepared according to literature
methods.
PHYSICAL MEASUREMENTS
The elemental analysis data were obtained by Analytischer Funktion-
stest vario EL Fab-Nr. 11982027 apparatus. The infrared spectra were
recorded on a 470 Shimadzu infrared spectrophotometer. The electronic
absorption spectra measurements were carried out on an UV-2101 PC
Shimadzu spectrophotometer. JEOL-JMS600 apparatus recorded the
mass spectra. The thermogravimetric analyses were determined using
an electrobalance of the type sartorius 200 MP converted to a ther-
mobalance by the addition of a small furnace and sample holder. The
temperature was measured using a Chromal-Alumal thermocouple at-
tached to a digital multimeter type Soar ME-550, the heating rate was
1
adjusted to be 8 C min
.
Preparation of 2-Acetylpyridine Benzoylhydrazone
(HApBH)
The ligand was prepared by refluxing equimolar mixtures of 12.10 g
2-acetylpyridine (0.2 mmol) and 12.00 g benzoylhydrazine (0.2 mmol)
in 50 ml absolute ethanol on a water bath for 8 h. After cooling the
reaction mixture, white crystals were isolated. The product was filtered
off and washed with ethyl alcohol, recrystallized from absolute ethanol,
and finally dried in a desiccator over anhydrous calcium chloride (yield
70% m.p 165 ).
Preparation of the Complexes
The mixed ligand complexes were prepared by adding 0.1 mmol of
2-acetylpyridine semicarbazone (0.36 g) or 0.48 g of 2-acetylpyridine
benzoylhydrazone in 20 ml hot ethanol to a solution of 0.1 mmol of bis
(dialkyldithiophosphato) nickel (II) (0.74 g of dimethyldithiophosphato
Ni(II), 0.85 g of diethyldithiophosphato Ni(II) and 0.96 g of dipropy-
ldithiophosphato Ni(II)) in 20 ml hot chloroform with continuous
stirring. The color of the mixture becomes green or yellowish green.

570
A. S. A. Zidan
The solid crystals were separated after three days, filtered and
washed with diethyl ether several times, and dried over calcium
chloride.
RESULTS AND DISCUSSION
The complexes are partially soluble in ethanol and common organic
solvents; they have good solubility in DMF and DMSO. Analytical data,
color, and melting or decomposition points are tabulated in Table I.
The mixed ligand complexes are formed according to the following
equations:
[Ni{(RO)2PS2}2] + Apsc → [Ni{(RO)2PS2}2(Apsc)]
[{Ni(RO)2PS2}2] + HApBH → [Ni{(RO)2PS2}(ApBH).] + (RO)2PS2H
(1)
(2)
Where
R = CH3, C2H5, or n-C3H7-dithiophosphate.
IR Spectra
The main spectral bands of the ligand 2-acetylpyridine benzoylhy-
drazone (HApBH) and the prepared complexes are listed in Table II.
TABLE I Analytical Data and Physical Properties of HApBH and the
Complexes
C%
H%
N%
S%
Dec.
No.
Complex
Color
(calc.) (calc.) (calc.)
(calc.) P.C
1
[Ni{(MeO)2PS2}2(Apsc)] Green
26.20
(26.15) (4.02) (10.16) (23.27)
31.70 4.95 9.25 21.15
(31.64) (4.98) (9.23) (21.12)
36.15 5.80 8.50 19.40
(36.21) (5.77)
70.26 5.50
4.00
10.17
23.30
180
210
200
165
180
190
190
2
3
[Ni{(EtO)2PS2}2(Apsc)]
[Ni{(PrO)2PS2}2(Aspc)]
HApBH
Green
Green
White
(8.44) (19.33)
17.54
(70.28) (5.48) (17.56)
42.25 4.05 9.20
(42.32) (4.00)
44.90 4.54
(44.84) (4.60)
47.15 5.20
(47.08) (5.14)
—
14.20
4
5
6
[Ni{(MeO)2PS2}(ApBH)] Brown
(9.25) (14.12)
8.77 13.40
(8.71) (13.30)
[Ni{(EtO)2PS2}(ApBH)]
[Ni{(PrO)2PS2}(ApBH)]
Brown
Greenish
yellow
8.18
(8.24)
12.50
12.57

571

572
A. S. A. Zidan
1. The IR spectra of 2-acetylpyridine semicarbazone complexes (1–3)
1
show two bands in the ranges 3370–3390 cm 1 and 3445–3460 cm
which are assigned to the symmetric and asymmetric stretching
modes of NH2, indicating the noninvolvement of this group in coordi-
nation. A strong band appears in the region 1585-1590 cm 1; suggest-
ing that Apsc ligand coordinates through the nitrogen atom of azome-
thine group.5 Bands of strong intensities around 1665–1680 cm 1 in
the spectra of the above complexes may be attributed to (C = 0).
1 18
The frequency lowering of this band from 1760 cm
in the ligand
1
to 1665–1680 cm in the spectra of the complexes demonstrates
the participation of the carbonyl group in coordination.5 Moreover,
bands observed in the region 3250–3285 cm 1 are attributed to NH
of the imino group, confirming its nonparticipation in coordination.
Thus, the 2-acetylpyridine semicarbazone is found to act as neutral
bidentate ligand in complexes (1), (2), and (3); coordinating through
oxygen of the carbonyl group (ketoform) and nitrogen atom in the
azomethine group.5
2. In the IR spectrum of 2-acetylpyridine-benzoylhydrazone ligand
1
(HApBH), the band at 3200 cm
may be assigned to NH of
the imino group and the sharp bands located at 1600, 1645, and
980 cm 1, may be attributed respectively to the
,
O and
C
N
C N
N
modes.19,20 Moreover, there are some bands appear at 1540, 1040,
1
660, and 440 cm are attributed to
of the pyridyl ring.21
C
C+C Np
Two tautomeric forms, the keto form structure (III) and the enol
form structure (IV), can represent HApBH.
3. The comparative study of the infrared spectra of the mixed com-
plexes and the free ligand can be performed only on the main bands
(Table II). The IR spectra for the complexes (4–6) exhibit a band
1
at 1580–1585 cm due to
N. This is shifted to lower frequency,
C
suggesting that this group takes part in coordination. The coordina-
tion of nitrogen to the metal atom would be expected to reduce the
electron density on the azomethine link and thus cause a shift in
the
band. The small shift to higher frequency of the band at
C
N
1
22
(1015–1020 cm 1) and (980 cm in the ligand) due to
can be
taken as additional evidence for the participation of the azomethine
N
N

Mixed Ligand Complexes of Nickel (II) Dialkyldithiophosphates
573
group in bonding. All these changes in amide group vibrations reveal
the involvement of the amide oxygen in coordination by loss of one
proton. This result is confirmed by the presence of a new band at
23,24
535–540 cm 1, ascribed to
.
However, the intensity of NH
M
O
band decreased in the complexes (4–6); the new band appears at
1
1430–1440 cm and may be due to
.
C
O
From IR spectra for the complexes (4–6) we can conclude that
HApBH behaves as mononegative tridentate ligand, coordinating
through carbonyl oxygen in the enol form, azomethine nitrogen, and
acetylpyridine ring nitrogen,25 which was confirmed from the shift
of
to higher frequency.
C
Np
4. There are some bands in the IR spectra of all the complexes
(1–6) characteristic of dithiophosphate group: (a) Two bands ap-
pear in the two regions 590–600 and 680–690 cm 1; these bands are
assignable to the symmetric and asymmetric stretching frequencies
of P S band,15,26 (b) The P O stretching frequency occurs at 930–
1020 cm 1, this band was observed as one or two bands.15
Support of the above interpretation is the appearance of the ab-
23,24
27
26
sorption frequencies
,
1
,
and
at 535–555,
(M O)
(M N)
(M S)
415–430, and 485–510 cm respectively.
ELECTRONIC SPECTRA
The electronic spectra for all the complexes are recorded in DMF and
listed in Table III. The electronic spectra of all complexes (1–6) are simi-
lar, where they consist of three types of transition. (1) Two d-d transition
TABLE III Electronic Spectral Bands of the
1
Complexes and their Assignments (cm
)
d
d
Charge transfer Intraligand
No.
Transition
Transition
Transition
1
11,455,
16,148
11,712,
15,173
12,360,
15,310
11,830,
14,920
11,730,
16,550
11,330
16,180
26,182,
32,734
25,640,
32,250
25,710,
32,780
25,600,
32,460
25,700,
33,220
25,570,
32,780
37,595
2
3
4
5
6
38,763
37,590
37,730
37,730
37,920

574
A. S. A. Zidan
1
bands appear in two regions 11,330–12,360 and 14,920–16,550 cm
3
3
assignable to 3A2g → T2g
(
1) and 3A2g → T1g (F) ( 2) transition respec-
tively. These transitions correspond to an octahedral structure around
Ni(II) in the complexes. The six-coordination geometry may be attained
through molecular association in the complexes. (2) The second type of
1
transitions occurs with high intensity in the range 25,570–33,220 cm
and is assigned to charge-transfer28 transitions. (3) The intraligand
transitions are located in the range 37,595–38,763 cm 1; they may cor-
respond to n- transitions.29
From the forgoing data, the following structures can be postulated
for the complexes
THERMAL ANALYSIS
The thermogravimetric analysis behavior of the complexes 1–6 is di-
vided according to the second ligand:
(a) The first type represented by complex 2 (Figure 1). The TG and
DTG thermograms for this complex consist of two stages. The
first weight loss occurs at 105 C, correlated to 18.2% and is
attributed to elimination of four ethylene molecules (calc. 18.5%)

Mixed Ligand Complexes of Nickel (II) Dialkyldithiophosphates
575
FIGURE 1 TG (—) and DTG (----) thermograms of [Ni {(EtO)2PS2}2 (Apsc)].
from diethyldithiophosphate moiety forming the unstable com-
pound [Ni{(OH)2PS2}2(Apsc)]. The last complex decomposes at
270 C forming Ni2O3 as the final product. Elimination of alkenes
from dialkyldithiophosphate is known previously.30 The mechanism
of this thermal decomposition could be proposed as follows:
[Ni{(RO)2PS2}2Apsc] alke→ne [Ni{(OH)2PS2}2Apsc]
(3)
where
R = ethyl or n-propyl.
(b) An examination of the TG and DTG curves (Figure 2) of the lig-
and 2-acetylpyridine benzoylhydrazone (HApBH) indicates that the
curve consists of three decomposition steps at 260, 325, and 465 C.
The first step seems to be associated with the expulsion of the radi-
cal C7H8N3 (calc. 56.0%, found 56.1%), which may take H forming
C7H9N3 molecule. The second step is small and the mass loss cor-
relates well with the evolution of carbon monoxide molecule (calc.
11.7%, found 11.8%) leaving a phenyl radical C6H6 which decom-
poses in final stage.
It is of interest to note that the thermal decomposition of the lig-
and (HApBH) beers some resemblance to the fragmentation pattern

576
A. S. A. Zidan
FIGURE 2 TG (—) and DTG (----) thermograms of HApBH.
of its mass spectrum and the mechanism of this thermal decompo-
sition may be represented as:
(c) The second type of the complexes according to the behavior of ther-
mal analysis can be represented by complex 6 (Figure 3). The TG
and DTG thermograms of compound 6 contain three decomposi-
tion steps. The first (150 C) and second (240 C) steps recorded are

Mixed Ligand Complexes of Nickel (II) Dialkyldithiophosphates
577
FIGURE 3 TG (—) and DTG (----) thermograms of [Ni {(EtO)2PS2} (ApBH)].
related to elimination of 2 CH2 CH2 molecules and C7H7N2 radical
(calc. 36.5% found 37%) to form an unstable complex which decom-
poses at 330 C with nickel oxide as the end product. The rupture of
N N bond during thermal decomposition of hydrazones is known
in literature.31
The mechanism of the thermal decomposition for complex 6 could be
suggested as following
MASS SPECTROMETRY
The mass spectral fragmentation pattern of [Ni{(EtO)2PS2}2(Apsc)] is
depicted in Scheme 1. One branch (a) of this scheme represents a series
FIGURE 4 Proposed thermal decomposition of the complex [Ni-
{(EtO)2}PS2(ApBH)].

578
A. S. A. Zidan
SCHEME 1
of fragments, corresponding to fragmentation of 2-acetylpyridine semi-
carbazone that loses a [NH2 CO.]+ forming the species [C7H8N3]+
m/z = 134. This ion represents the base peak indicating its higher
stability; finally the fragment ions [C CH3]+ with m/z = 27 (23.4%)

Mixed Ligand Complexes of Nickel (II) Dialkyldithiophosphates
579
and pyridine [C5H4N]+ m/z = 78 (41.3%) are formed. The other
branch (b) includes a nickel(II)bis(diethyldithiophosphate) fragment
ion [NiC8H20O4P2S4]+ of m/z = 426 (73%) which losses four ethylene
molecules leading to the formation of [Ni{(OH)2PS2}2]+(30) with m/z =
314 (14.8%) and the final fragment ion [PS2]+ of m/z = 95 (9.6%) is
formed.
The mass spectrum of the ligand (HApBH) exhibits the molecular
ion [M+] with intensity (27.6%) and m/z = 239. The mass spectral
fragmentation of the ligand is recorded in Scheme 2. We suggest two
fragmentation pathways, which are followed by this molecular ion. First
one [A] includes a strong intensity peak at m/z = 134(100%). This can
be ascribed to the fragment ion (a) resulting from the elimination of
benzoyl fragment (b) which is characterized by m/z = 105 and (74%).
The second pathway [B] includes the cleavage occurring on N C
and C N25 by elimination of the diazo group. This can be attributed
to formation of the fragment ion (b) m/z = 105 (74%) and (c) m/z = 106
(94%) as shown in Scheme 2. Some fragments were detected for similar
compounds in the literature.25
SCHEME 2

580

Mixed Ligand Complexes of Nickel (II) Dialkyldithiophosphates
581
MICROBIOLOGICAL SCREENING
The biological activities of the two organic ligands (Apsc and HApBH),
some related complexes and Erythromycine (as a reference compound)
were tested against a number of bacteria and fungi. The used bacteria
were B. cereus G+ve, M. luteus G+ve, and Streptonyces G+ve; the tested
fungi were Asperrgillus flovus, Fusarium oxysporium, Chrysosporium
tropicm, and A. fumig. var. albus. The culture media used were nu-
tritent agar (N.A.) media supplemented with one GM yeast/liter. The
antimicrobial activity of each compound was evaluated by the classi-
cal filter paper disc technique. Each of the compounds was dissolved
in dimethylformamide (DMF) and a solution with the concentration
0.5-mg ml 1was prepared. The organic compound (HApBH) shows a
high degree of activity against bacteria and fungi (Table IV). This ac-
tivity may be due to the pyridyl ring and OH group in the compound
(Enol form); which play an important role in the antibacterial25 and
antifungal activity.
CONCLUSION
The spectroscopic data show that the 2-acetylpyridine semicarbazone
(Apsc) acts in the complexes [Ni{(RO)2PS2}2(Apsc)] (R=methyl, ethyl,
or n-propyl) as a bidentate ligand through C N nitrogen and oxygen
of C O group. However, 2-acetylpyridine benzoylhydrazone (HApBH)
coordinates as a mononegative tridentate ligand in the complexes
[Ni{(RO)2PS2}(ApBH)] where the coordination occurs through enolic
oxygen, azomethine nitrogen, and acetylpyridine ring nitrogen. An oc-
tahedral structure for all the complexes was postulated.
The thermoanalytical results of the first type of the complexes prove
that the main feature of the first decomposition step is the evolution of
alkene molecules and the final product is Ni2O3. However the TG and
DTG thermograms of the HApBH ligand consist of three decomposition
steps. The first and second steps are associated with the expulsion of
C7H8N3 radical and carbon monoxide respectively. Moreover, the be-
havior of thermal analysis of the second type of the complexes shows
that the weight loss of the first step is related to elimination of alkenes
and C7H7N2radical and the final product is Ni2O3.
The mass spectral fragmentation pattern of [Ni{(EtO)2PS2}2(Apsc)]
exhibit fragmentation of Apsc and [Ni{(EtO)2PS2]+ fragment ion. How-
ever, the mass spectrum of the HApBH gave the molecular ion of the
ligand [M+], which decomposed to two main fragments. The HApBH
ligand has a high toxicity against the bacteria and fungi under study;

582
A. S. A. Zidan
this may be due to presence of pyridyl ring and hydroxyl group in the
compound.
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