Synthesis, characterization, and structural studies of nickel(II) complexes of some new substituted acid hydrazides

Article abstract of DOI:10.1080/15533174.2010.492555

The syntheses, spectroscopic, magnetic, and antimicrobial and theoretical studies of a new series of hydrazides; RCOCH₂CONHNH₂ (R = CH₃, C₃H₇, C₆H₅) variously described as acetoacetic (AAAH), butyrylacetic (BUTAH) and benzoylacetic (BENZAH) acid hydrazides and its nickel(II) complexes are reported. Microanalyses, room temperature magnetic susceptibility measurements infrared and electronic reflectance spectra are consistent with a distorted six coordinate octahedral geometry for the complexes. The modeled compounds using semi-empirical method PM3 and density functional theory (DFT) shows a good correlation of crystallographic data. The compounds show appreciable activity against gram +ve and gram-ve bacteria. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/15533174.2010.492555

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Synthesis and Reactivity in Inorganic, Metal-Organic,
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Synthesis, Characterization, and Structural Studies
of Nickel(II) Complexes of Some New Substituted
Acid Hydrazides
F. A. Adekunle a , J. A. O. Woods b , O. O. E. Onawumi a & O. A. Odunola a
a Department of Pure and Applied Chemistry , Ladoke Akintola University of
Technology , Ogbomoso, Nigeria
b Department of Chemistry , University of Ibadan , Ibadan, Nigeria
Published online: 13 Jul 2010.
To cite this article: F. A. Adekunle , J. A. O. Woods , O. O. E. Onawumi & O. A. Odunola (2010) Synthesis,
Characterization, and Structural Studies of Nickel(II) Complexes of Some New Substituted Acid Hydrazides, Synthesis and
Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 40:6, 430-437
To link to this article: http://dx.doi.org/10.1080/15533174.2010.492555
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Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 40:430–437, 2010
Copyright © Taylor & Francis Group, LLC
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2010.492555
Synthesis, Characterization, and Structural Studies of
Nickel(II) Complexes of Some New Substituted Acid
Hydrazides
F. A. Adekunle,1 J. A. O. Woods,2 O. O. E. Onawumi,1 and O. A. Odunola1
1Department of Pure and Applied Chemistry, Ladoke Akintola University of Technology, Ogbomoso,
Nigeria
2Department of Chemistry, University of Ibadan, Ibadan, Nigeria
CH3, C3H7, and C6H5) and their nickel(II) complexes. These
complexes are new and represent the first systematic studies on
these series of hydrazides.
The syntheses, spectroscopic, magnetic, and antimicro-
bial and theoretical studies of a new series of hydrazides;
RCOCH2CONHNH2 (R = CH3, C3H7, C6H5) variously described
as acetoacetic (AAAH), butyrylacetic (BUTAH) and benzoylacetic
(BENZAH) acid hydrazides and its nickel(II) complexes are re- EXPERIMENTAL
ported. Microanalyses, room temperature magnetic susceptibility
Materials
Reagent grade ethylacetoacetate, ethylbutyrylacetate, ethyl-
measurements infrared and electronic reflectance spectra are con-
sistent with a distorted six coordinate octahedral geometry for the
complexes. The modeled compounds using semi-empirical method
PM3 and density functional theory (DFT) shows a good correlation
of crystallographic data. The compounds show appreciable activity
against gram +ve and gram-ve bacteria.
benzoylacetate, hydrazine hydrate, nickel(II) acetate tetrahy-
drate, nickel(II) chloride hexahydrate, nickel(II) sulphate
hexahydrate and nickel(II) nitrate hexahydrate were purchased
from the British Drug House Chemicals Ltd (BDH) and Aldrich
Chemicals Co., and were used without further purification. Nu-
trient agar was obtained from Antec Diagnostic Products, United
Kingdom.
Keywords synthesis, hydrazides, structure, spectroscopic
INTRODUCTION
The interest associated with hydrazides, its analogues and
their metal complexes continue to grow due to their analytical
applications, pharmaceutical properties, and ubiquitous biologi-
cal activities.[1−7] The metal complexes of hydrazides have been
established from test microbes to have more enhanced biolog-
ical activities than the free ligands.[1,4] Subsequently, the syn-
theses of new hydrazides, their derivatives, factors influencing
their isolation, varied bonding, and stereochemical possibilities
offered by these compounds continue to be of interests.[8−12]
A survey of the literature shows that hydrazides-RCONHNH2
where R = alkyl or aryl group have been studied extensively,
whereas the alkyloxyl- and aryloxyl-RCOCH2CONHNH2 and
their metal complexes have not been investigated.[13−15] In this
paper, we present our report on the syntheses, spectroscopic,
magnetic and biological activities of RCOCH2CONHNH2(R =
Preparation of the Ligands
Preparation of acetoacetic acid hydrazide (AAAH)
19.40 mL (400 mmoles) hydrazine hydrate in a 250 mL
quick–fit conical flask fitted with a reflux condenser was stirred
with gentle heating while ethylacetoacetate (400 mmoles,
51 mL) was added portion wise. The orange colored suspension
obtained was refluxed for 15 min, after which 170 mL ethanol
was added to give a clear yellow solution. The resultant solution
was refluxed for an additional 4 hours. The ethanol was distilled
off and the remaining solution was transferred into a beaker
and left overnight at room temperature. The precipitates
obtained were filtered by suction, washed with deionized water,
and dried over calcium chloride in a desiccator. (Yield 17.2 g,
37%).
Preparation of butyrylacetic acid hydrazide (BUTAH).
Received 12 November 2009; accepted 4 May 2010.
9 mL (9.33 g; 190 mmoles) hydrazine hydrate was transferred
to a 250 mL quick–fit conical flask fitted with a reflux condenser.
30 mL (29.5 g, 190 mmoles) ethyl butyrylacetate was added
portion wise. On addition of about 20 mL of the ester, an off–
white colored paste was observed. The remaining 10 mL was
The authors are grateful to Ladoke Akintola University of Technol-
ogy for financial support and Dr. Banjo Semire for useful discussions.
Address correspondence to O. A. Odunola, Department of Pure and
Applied Chemistry, Ladoke Akintola University of Technology, P.M.B.
4000, Ogbomoso, Nigeria. E-mail: odunola@yahoo.com
430

SYNTHESIS AND STRUCTURAL STUDIES OF HYDRAZIDES
431
added and mixture heated under reflux for 15 min, after which in the metal complexes was determined using complexomet-
140 mL ethanol was added, which dissolved the paste and gave ric titration using EDTA17. Infrared spectra were recorded on a
a faint yellow solution. Refluxing continued for an additional 4 Nicolet Avatar 330 FT-IR spectrophotometer using KBr discs.
hours after which the ethanol was distilled off. The remaining Electronic reflectance spectra of the ligands and complexes were
peach colored suspension was transferred to a 250 mL beaker recorded using Genesys 10 Scanning Spectrophotometer made
where on cooling, formed crystalline cream precipitates. The by Thermo Electron Corporation. Magnetic measurements were
precipitates were filtered by suction, washed with deionized carried out using the Faraday method on an instrument by Sher-
water and dried in a desiccator over calcium chloride. (Yield wood Scientific, Cambridge.
16.6 g, 62%).
Biological Assay
Preparation of benzoylacetic acid hydrazide (BENZAH).
The microorganisms used are Escherichia coli, Pseudomonas
aeruginosa, Bacillus cereus, Staphylococcus aureus, Kleb-
siella pneumoniae, Micrococous acidophilus, Pseudomonas
putrifaciens(A1), Streptococcus bovis, Proteus sp., Salmonella
30 mL (33.3 g, 170 mmoles) ethyl benzoylacetate solution in
ethanol was added portion wise to 8 mL (8.67 g, 170 mmoles)
hydrazine hydrate in a 250 mL quick–fit conical flask. The light
peach solution obtained was refluxed with gentle heating for 15
typhi, Pseudomonas putrifaciens(Q), Serratia marcescens.
min, after which 150 mL ethanol was added and refluxing con-
The media was prepared by dissolving 28 g of the nutrient
tinued for additional 4 hours. The ethanol was distilled off and
agar in 1000 mL deionized water. The solution was sterilized at
the remaining solution was transferred to a 250 mL beaker where
121◦C for 15 mins in an autoclave.
it was left overnight. The cream colored crystalline precipitates
Concentrations of 10 µg/mL, 100 µg/mL and 1000 µg/mL
of the benzoylacetic acid hydrazide formed were filtered by suc-
of each of the complexes were made in dimethylsulphox-
tion, washed with deionized water and then dried in a desiccator
over calcium chloride (Yield 21.5 g, 70%).
ide. The dimethylsulphoxide was used as the negative control
while gentamycin solution in DMSO was used as the positive
control.
Preparation of the Nickel(II) Complexes
The twelve bacterial isolates were tested for sensitivity
to some of the compounds by means of a disc diffusion
Preparation of Ni(BENZAH)3(OAc)2.
Ni(OAc)2.4H2O (2.10 g, 8.4 mmol) dissolved in 40 mL
method.[14−15]
of 40% methanol was stirred while 3.00 g (16.9 mmol) ben-
zoylacetic acid hydrazide suspension in 10 mL methanol was
added dropwisely. Light green precipitates were observed im-
Computational Methods
The complexes chosen for these studies are Ni[AAAH]3Cl2,
mediately, and the mixture was stirred for one hour before it
Ni[BUTAH]3Cl2 and Ni[BENZAH]3Cl2 since the outer- sphere
was filtered by suction, washed with 40% methanol, deion-
ions have the least probability of interaction with the complex
ized water and dried over calcium chloride (Yield 2.84 g,
ion in the crystal lattice. Geometries of the Ni (II) complexes
63%). The same procedure was used in the preparation of all the
ions were initially optimized by the PM3[18] method and the
other nickel(II) benzoylacetic acid hydrazide complexes except
resulting structures were further optimized using hybrid func-
for Ni(BENZAH)3(NO3)2 where precipitation was not observed
tional three-parameter Becke exchange Lee-Yang-Parr corre-
until the pH was raised to 9 with ammonia solution.
lation (DFT-B3LYP) with 6-31G* basis set because of its per-
Preparation of Ni(AAAH)3(NO3)2
ceived better accuracy. All calculations were performed with the
Spartan 06.[19] The spin occupied molecular orbitals (SOMO)
of the complexes ions were also displaced in order to know the
effect of changing ‘R’ (RCOCH2CONHNH2; R = CH3, C3H7
and C6H5) on the molecular properties as it affects electronic
transitions. The calculations were carried out on a 4.0 GHz Dell
PC, with 1 Gb RAM and 120 Gb HD, under the windows 2007
operational system.
4.37 g (15 mmol) of Ni(NO3)2.6H2O was dissolved in
10 mL of 40% methanol and stirred in a 250 mL beaker while
acetoacetic acid hydrazide (3.48 g, 30 mmoles) dissolved in
10 mL methanol was added dropwisely. Precipitation occurred
after the pH was raised to 9. Stirring continued for additional
1hr after which the light green precipitates formed were filtered,
washed with 40% methanol and deionized water and was dried
over calcium chloride in a dessicator. (Yield 4.4 g, 54%). A sim-
ilar procedure was used to isolate the other nickel(II) complexes
of acetoacetic acid hydrazides.
RESULTS AND DISCUSSION
The nickel(II) complexes of butyrylacetic acid hydrazides
were similarly prepared as described above.
Preparation of the Compounds
Acetoacetic, butyrylacetic, benzoylacetic were prepared
from their ethyl esters by refluxing equimolar amounts of the
hydrazine hydrate and their respective ethyl esters for 4 hrs. The
Physical Measurements
Elemental analyses for C, H, and N were determined using a hydrazides were obtained in reasonable yields (60–70%) ex-
Perkin- Elmer 240 C elemental analyzer. The percentage nickel cept acetoacetic acid hydrazides, which gave a 37% yield. The

432
F. A. ADEKUNLE ET AL.
representative equation for the formation of the hydrazide is the electron density on the hydrazide moiety. In this series, a
given below:
bathochromic shift was observed in the ‘amide’ values which
were more pronounced in the butyrylacetic acid hydrazide than
acetoacetic acid hydrazide.
RCOCH2COORꢀ + H2NNH2→ RCOCH2CONHNH2+RꢀOH
R CH3, C3H7, C6H5andRꢀ C2H5
Electronic Spectra
The electronic reflectance spectra of the compounds studied
(Table 2) have been assigned by critically comparing those of
the ligands with the complexes and those of previous work done
on similar system.[10,12,15]
The nickel(II) complexes prepared by reacting the metal salts
with the respective hydrazides gave a composition of 1:3 mole
ratio as given below:
In the ultraviolet region of the compounds studied, the band
observed between 45,050–51,810 cm−1 have been assigned to
n → σ∗ transitions presumably due to the excitation of a nitro-
gen lone pair of electron to antibonding σ-orbital of the amino
group. Some additional bands observed in this region between
42,200–30030 cm−1 have been assigned to a combination of
π → π∗ and π → n transitions of the carbonyl groups.[1,22]
This observation shows significant π → π∗ interactions in the
complexes and have often been correlated with the involvement
of N and O atoms from the ligand in coordination that strength-
ens the C=O and the –NH2 bonds involved in the charge transfer
process22.
NiX2. xH2O + 3RCOCH2CONHNH2 →
Ni(RCOCH2CONHNH2)3(X)2
where X Cl, NO3, CH3COO or 1/2 SO4; R CH3, C3H7
and C6H5
The result of the C, H, N and metal analyses showed a fairly
good agreement between the observed and calculated values
(Table 1). The elemental analyses showed that the acid hy-
drazide reacted with the nickel(II) salts in ratio 3:1. The nickel
complexes display various shades of blue and green color and
exhibited marked insolubility in common organic solvents mak-
ing the growing of a single crystal for X-ray impossible. This is
typical of acid hydrazides metal complexes.[8,14−15]
In the visible absorption spectra of Ni(II) octahedral com-
plexes, three spin-allowed transitions are normally observed.[17]
3
3
These absorptions are ν1 3A2g → T2g (F), ν2 3A2g → T1g
(F), and ν3 3A2g → T1g (P), which generally fall in the range
3
7000–13,000, 11,000-20,000 and 19,000-27000 cm−1, respec-
tively.
Infrared
The
visible
spectra
of
Ni(AAAH)3(NO3)2,
The selected infrared vibrational frequencies of the com-
pounds are listed in Table 2. These vibrational frequencies
are very consistent with the structural features of the com-
pounds studied. In the studies of spectra of hydrazides and
their metal complexes, three related vibrations are often used
to infer coordination of the metals to the ligands.[14,15,20] These
are the carbonyl stretching frequency [νs(C O)] or the ‘amide
1’, the in-plane bending deformation and stretching frequency
for cyanate [δ(N-H) +νs(C-N)] or the ‘amide II’ and the amino
stretching vibrations νs(NH2). In the ligands reported here, the
amino stretching frequency νs(NH2) observed between 3539–
3452 cm−1 became weaker and was lowered to 3195–3375 cm−1
on coordination to the metal suggesting the participation of the
amino group in the bonding. The vibrations between 1626–1618
cm−1 and 1600–1544 cm−1 in the ligands are assigned to ‘amide
I’ and ‘amide II’ bands, respectively. These bands are lowered
to 1618–1569 cm−1 and 1594–1473 cm−1on coordination to
nickel(II) metal ion. As expected, the highest values for the
‘amide I’ and ‘amide II’ vibrations were observed for benzoy-
lacetic acid hydrazides (BENZAH) ligands and their complexes.
This is due to the inductive (–I) electron withdrawing effect of
Ni(AAAH)3(OAc)2 and Ni(AAAH)3SO4, which displayed a
band each between 15,773 – 15,873 cm−1 region have been
3
3
assigned to the A2g → T1g(F) transition. Ni(AAAH)3Cl2
3
3
showed the 3A2g → T2g and 3A2g → T1g(P) transitions, re-
spectively, at 13,699 cm−1 and 20,833 cm−1. The butyrylacetic
acid hydrazide complexes showed the 3A2g → T1g(F) transi-
3
tion for Ni(BUTAH)3(NO3)2 and Ni(BUTAH)3SO4 at 16,313
cm−1, and 15,385 cm−1, respectively. Ni(BUTAH)3(OAc)2 had
two absorption bands at 15,385 cm−1 and 25,000 cm−1, which
3
3
3
3
is assignable to the A2g → T1g(F) and A2g → T1g(P).
Ni(BUTAH)3Cl2 had 3A2g → 3T2g at 9,390 and 3A2g →
3T1g(P) at 20,661 cm−1
.
In the benzoylacetic acid hydrazides complex series, only
3
the 3A2g → T1g(F) transition was observed between 15,625–
16,077 cm−1. These observations and assignments of the tran-
sitions in the complexes are consistent with a six coordinate
nickel(II) in an octahedral environment.[23]
Magnetic Moment
Generally, for tetrahedral nickel(II) complexes, effective
the benzoyl group, which reduces the electron available on the magnetic moments of (µeff) lie between 3.2–4.1 BM, while for
hydrazide moiety resulting in increase in the force constants of octahedral complexes, the values range between 2.9–3.3 BM.
the bond. Conversely, the acetoacetic acid and butyrylacetic acid Deviations from the ‘spin-only’ magnetic moment of 2.83 B.M
hydrazides that have electron donating substituents increases are attributed to orbital contributions to the magnetic moments

SYNTHESIS AND STRUCTURAL STUDIES OF HYDRAZIDES
433
TABLE 1
Analytical data for the compounds
Formula
Yield M.p.
Compounds µeff
(empirical formula)
Analyzed
(calculated)
Weight
Color
(%)
(◦C)
C
H
N
Ni
—
(B.M.)
AAAH
(C4H8N2O2)
116.12
503.15
531.09
478.08
525.17
144.18
587.31
615.25
562.24
609.33
178.19
689.36
717.30
664.29
711.38
cream
lt. green
lt. green
green
61
64
54
70
45
62
69
69
65
34
70
70
71
65
63
217-219
134
41.22
(41.37)
29.31
(28.65)
27.01
(27.14)
32.88
(30.15)
36.39
(36.59)
49.66
(49.99)
36.67
(36.81)
35.30
(35.14)
38.63
(38.45)
43.41
(43.37)
60.44
(60.66)
47.21
(47.04)
45.26
(45.21)
49.00
(48.82)
52.46
6.86
(6.94)
4.81
(4.81)
4.60
(4.56)
4.68
(5.06)
5.66
(5.76)
8.32
(8.39)
6.25
(6.18)
5.72
(5.90)
6.22
(6.45)
6.49
(6.95)
5.62
(5.66)
4.10
(4.39)
4.28
(4.22)
4.66
(4.55)
5.25
23.68
(24.13)
15.72
(16.70)
20.45
(21.10)
15.64
(17.58)
15.83
(16.00)
19.31
(19.43)
14.44
(14.31)
18.36
(18.21)
15.11
(14.95)
13.90
(13.79)
15.66
(15.72)
12.02
(12.19)
15.82
(15.62)
12.69
(12.65)
11.82
Ni(AAAH)3SO4
(C12H24N6O10SNi)
Ni(AAAH)3(NO3)2
(C12H24N8O12Ni)
Ni(AAAH)3Cl2
(C12H24N6O6Cl2Ni)
Ni(AAAH)3(OAc)2
(C16H30N6O10Ni)
BUTAH
15.33
(11.67)
11.34
(11.05)
16.11
(12.28)
11.04
(11.18)
—
3.40
3.26
3.30
3.16
120
146
lt. green
cream
130
218–220
262
(C6H12N2O2)
Ni(BUTAH)3SO4
(C18H36N6O10SNi)
Ni(BUTAH)3(NO3)2
(C18H36N8O12Ni)
Ni(BUTAH)3Cl2
(C18H36N6O6Cl2Ni)
Ni(BUTAH)3(OAc)2
(C22H42N6O10Ni)
BENZAH
blue
10.22
(10.00)
9.67
(9.54)
10.15
(10.44)
9.52
3.09
2.97
3.20
3.15
lt. green
green
254
166–168
224
lt. green
white
(9.64)
—
156–158
152
(C9H10N2O2)
Ni(BENZAH)3SO4
(C27H30N6O10SNi)
Ni(BENZAH)3(NO3)2
(C27H30N8O12Ni)
Ni(BENZAH)3Cl2
(C27H30N6O6Cl2Ni)
Ni(BENZAH)3(OAc)2
(C31H36N6O10Ni)
green
8.50
(8.52)
8.18
(8.18)
8.56
(8.84)
8.04
(8.25)
3.17
3.26
3.19
2.94
lt. green
green
148–150
156–158
160–162
lt. green
(52.34)
(5.10)
(11.81)
and depends very much on the stereochemistry. Thus, the tetra- bition against Staphylococcus aureus and Pseudomonas putrifa-
hedral and octahedral Ni(II) complexes have no clear-cut dis- ciens (A1), while NI[BENZAH]3Cl2 showed moderate growth
tinction in the magnetic moments, and unusual moments of inhibition against Serratia Marcescens. The other complexes
2.97 B.M and 3.78 B.M, respectively, have been reported.[24] displayed very low inhibition against the tested bacteria. Gen-
The room temperature magnetic moments for the Ni(II) com- erally, the activities of the acid hydrazides were enhanced by
plexes studied were observed between 2.94–3.40 B.M. (Table coordination to the nickel(II) ions.
1), which falls in the range normally observed for octahedral
nickel(II) complexes.[24]
Computational Studies
Geometries and structural data
Antimicrobial Activities
The modeled molecular structures consist of a mononuclear,
The acid hydrazides and their nickel(II) complexes showed six-coordinated Ni(II) complexed with three units of hydrazides.
measurable activities against the test organisms by the mod- The coordination to the metal is through the carbonyl oxygen
erate to high growth inhibition exhibited by some of the of the amide and the nitrogen of the amino group of each unit
compounds.[25] Ni[BUTAH]3(OAc)2 displayed a very high inhi- of the hydrazide. The geometry around the nickel(II) is best

434
F. A. ADEKUNLE ET AL.
TABLE 2
Some infrared frequencies and electronic spectral transitions for the compounds (cm−1
)
Compounds
amide I
amide II
νNH2
Electronic bands (× 103)
AAAH
1612(m)
1570(s)
1570(s)
1569(m)
1570(s)
1618(m)
1570(s)
1570(s)
1572(m)
1572(s)
1626(m)
1612(w)
1594(s)
1618(m)
1618(s)
1544(w)
1556(w)
1556(w)
—
3539(w)
3345(w)
3557(w)
3375(w)
3339(w)
3460(m)
3356(w)
3356(m)
3195(w)
3206(w)
3452(w)
3369(m)
3357(w)
3235(m)
3326(m)
51.28, 37.18
15.87
40.00, 36.50, 34.96, 15.77
20.83, 13.70
Ni(AAAH)3SO4
Ni(AAAH)3(NO3)2
Ni(AAAH)3Cl2
Ni(AAAH)3(OAc)2
BUTAH
Ni(BUTAH)3SO4
Ni(BUTAH)3(NO3)2
Ni(BUTAH)3Cl2
Ni(BUTAH)3(OAc)2
BENZAH
1513(w)
1592(w)
1476(s)
1473(s)
1505(s)
1476(s)
1600(s)
1579(w)
1553(m)
1594(s)
1594(s)
48.78, 40.49, 36.50, 32.57, 15.77
45.05
15.39
42.02, 35.34, 33.22, 16.31
20.66, 9.39
25.00, 15.39
49.75, 41.49, 38.61
51.81, 37.31, 33.22, 15.63
35.09, 30.03, 15.92
48.78, 36.90, 33.56, 16.08
51.02, 36.90, 31.65, 15.70
Ni(BENZAH)3SO4
Ni(BENZAH)3(NO3)2
Ni(BENZAH)3Cl2
Ni(BENZAH)3(OAc)2
s = strong; m = medium; w = weak
described as distorted octahedral. The calculated bite angles for going no distortion. For the three complexes, there is a larger
Ni(AAAH)3Cl2using B3LYP/6-31G* for O(1)-Ni-(N1), O(2)- deviation from ‘an ideal 180◦’ for the trans octahedral angles
Ni-N(3) and O(3)-Ni-N(5) are 90.17, 94.46, and 92.86◦, re- of O(1)-Ni-N(3), O(2)-Ni-N(5), and O(3)-Ni-N(1), which ex-
spectively. While the same bite angles for Ni(BUTAH)3Cl2and perienced a variation of between 18in the three complexes
Ni(BENZAH)3Cl2 are 90.81, 92.47, 92.53, and 90.95, 93.43, using both calculation methods. These observations are similar
92.35, respectively. While the two methods of calculations are to those obtained experimentally from our previous studies.[15]
closer in this respect, there is a small variation of less than The bond distances for Ni-O and Ni-N are affected by changing
4◦ from the ‘ideal value’ of 90◦ for a nickel complex under- ‘R’ (from acetyl, butyl and benzyl), although the differences
FIG. 1. Graphical representation of the SOMO orbitals for (a) Ni[AAAH]23+ ion, (b) Ni[AAAH]3Cl2, (c) Ni[BUTAH]3Cl2and (d) Ni[BENZAH]3Cl2.

SYNTHESIS AND STRUCTURAL STUDIES OF HYDRAZIDES
435
TABLE 3
◦
˚
Selected bond distances (A) and bond angles ( ) of Ni[AAAH]3Cl2, Ni[BUTAH]3Cl2, and Ni[BENZAH]3Cl2 calculated at PM3
and B3LYP/6-31G* levels
Ni[AAAH]3Cl2
Ni[BUTAH]3Cl2
Ni[BENZAH]3Cl2
Numbering
PM3
B3LYP/6-31G∗
PM3
B3LYP/6-31G∗
PM3
B3LYP/6-31G∗
Ni-O1
Ni-O2
Ni-O3
Ni-N1
Ni-N3
Ni-N5
C1-O1
C2-O2
C3-O3
C1-N2
C2-N4
C3-N6
N1-N2
N3-N4
N5-N6
O1-Ni-O2
O1-Ni-O3
O2-Ni-O3
N1-Ni-N3
N1-Ni-N5
N3-Ni-N5
O1-Ni-N1
O1-Ni-N3
O1-Ni-N5
O2-Ni-N1
O2-Ni-N3
O2-Ni-N5
O3-Ni-N1
O3-Ni-N3
O3-Ni-N5
C1-O1-Ni
C2-O2-Ni
C3-O3-Ni
O1-C1-N2
O2-C2-N4
O3-C3-N6
N2-N1-Ni
N4-N3-Ni
N6-N5-Ni
C1-N2-N2
C2-N4-N3
C3-N6-N5
1.888
1.845
1.867
1.872
1.871
1.854
1.284
1.351
1.337
1.357
1.470
1.514
1.455
1.440
1.344
83.89
83.82
82.05
91.14
88.05
90.89
91.75
175.65
92.44
97.18
92.54
173.69
175.56
93.25
92.47
106.42
107.89
107.38
118.64
112.23
114.09
100.06
99.45
106.58
119.76
112.77
115.74
1.922
1.925
1.942
1.956
1.985
1.955
1.297
1.356
1.346
1.381
1.478
1.526
1.479
1.442
1.352
86.06
89.42
89.15
91.89
91.97
86.42
90.17
170.67
89.70
102.08
94.46
169.30
198.93
91.55
92.86
107.19
106.45
112.66
119.91
115.03
121.56
103.07
101.01
108.77
120.63
114.87
116.62
1.887
1.845
1.868
1.871
1.871
1.855
1.285
1.349
1.335
1.357
1.468
1.512
1.454
1.441
1.345
83.77
83.71
82.22
91.09
87.98
90.63
91.78
175.46
92.98
97.32
92.38
173.85
175.49
93.41
92.26
106.80
107.93
107.39
118.68
112.36
113.93
100.20
99.20
106.54
119.69
119.52
115.52
1.942
1.926
1.941
1.955
1.987
1.954
1.296
1.352
1.344
1.381
1.474
1.533
1.477
1.439
1.350
85.19
90.06
89.92
91.82
90.99
86.47
90.81
171.21
89.24
100.94
92.47
172.80
197.88
92.97
92.53
107.05
109.44
110.32
119.14
116.04
121.18
102.75
103.80
108.74
121.01
119.29
117.82
1.881
1.836
1.898
1.858
1.874
1.851
1.283
1.365
1.256
1.365
1.476
1.422
1.462
1.435
1.382
81.38
82.38
83.72
91.43
88.36
90.86
92.37
173.49
94.53
97.09
92.90
173.30
174.52
93.94
90.50
108.01
107.43
106.45
117.23
112.57
119.80
101.04
98.81
105.79
119.53
112.93
115.85
1.932
1.945
1.968
1.937
1.988
1.954
1.295
1.376
1.246
1.392
1.484
1.441
1.468
1.423
1.386
83.59
90.06
89.71
91.34
92.78
87.02
90.95
171.28
92.91
101.38
93.43
169.59
198.44
90.66
92.35
108.58
109.78
112.01
119.93
117.21
120.87
102.74
102.15
109.53
121.31
116.03
116.98

436
F. A. ADEKUNLE ET AL.
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˚
˚
ranged from 0.002A to 0.024A. Generally, the Ni-Nand Ni-
O calculated at PM3 are shorter than that of B3LYP/6-31G*.
The correct values may be in between the two values per-
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