M.K. Bharty et al. / Polyhedron 173 (2019) 114125
3
3
. Syntheses
insoluble in common organic solvents but are soluble in DMF
and DMSO.
3
.1. Synthesis of [Mn(ppt) (o-phen)] (1)
2
4.1. IR spectra
A solution of Hppt (0.386 g, 2 mmol) in MeOH (10 mL) was
added to methanol solution (10 mL) of Mn(OAc)
ꢀ4H
0.245 g, 1 mmol) and the reaction mixture was stirred for 3 h at
room temperature. The resulting precipitate obtained was filtered
off and washed with methanol. A methanol solution of o-phen was
added slowly into the methanol suspension of the above com-
pound and stirred for 1 h. A yellow color solution obtained was fil-
tered off and kept for crystallization. Yellow crystals of 1 suitable
for X-ray analyses were obtained by slow evaporation of the
methanol solvent over a period of 15 days. Yield: 65%, m.p.
a
2
2
O
2
The IR spectrum of [Mn(ppt) (o-phen)] (1) shows absorptions
ꢁ1
(
(cm ) due to the stretching modes of NH (3183), C@O (1633),
NAN (1050), C@S (992), respectively. [Mn(ppt) (o-phen)] (1)
2
ꢁ
1
shows the absence of
the ligand) indicating loss of hydrogen from the nitrogen of thioa-
mide group which is supported by a small positive shift of 18 cm
m(NAN). A negative shift of about 35 cm in m(C@O) indicating
m
(NAH) band at ꢂ3224 cm (present in
ꢁ1
ꢁ
1
in
bonding through the carbonyl oxygen to the metal ion [39]. The
ꢁ1
appearance of two new bands at 485 and 419 cm suggest forma-
1
C
83 °C. Anal. Found: C, 62.40; H, 4.60; N, 13.75; S, 8.05%. Calc. for
36MnN (803.85): C, 62.75; H, 4.51; N, 13.93; S, 7.97%.
(NAH) 3183, (CAH) 3051–2924, (C@O) 1633,
(C@S) 992, (MnAN) 485, (MnAO) 419.
tion of MAN and MAO bonds. The IR spectrum of [Mn(aptt)(Cl)(o-
ꢁ1
42
H
8
O
2
S
2
2 2
phen) ]ꢀ2HapttꢀH O (2) shows absorptions (cm ) due to the
ꢁ
1
IR (KBr, cm ):
(NAN) 1050,
m
m
m
stretching modes of NAH (3261), C@N (1587), NAN (1036), C@S
(951), respectively. The occurrence of one OH stretching band in
the spectrum of complex 2 indicates the presence of water mole-
m
m
m
m
cule. The IR spectrum of [Mn(aptt)(Cl)(o-phen)
shows one band at 3261 cm due to m(NH) of triazole NH group
2
]ꢀ2HapttꢀH
2
O (2)
ꢁ1
2
3.2. Synthesis of [Mn(aptt)(Cl)(o-phen) ]ꢀ2HapttꢀH
2
O (2)
2
and the loss of one triazole NH group upon complexation. Thus, it
is clear from the IR data that the ligand acts as a uni-negative mon-
odentate in complex 2, bonding through one triazole thiolato sul-
fur (conversion of thione sulfur to thiolato sulfur). A negative
A solution of Haptt (0.570 g, 3 mmol) in MeOH (10 mL) was
added to a methanol solution (10 ml) of MnCl ꢀ4H O (0.198 g,
2
2
1
mmol) and the reaction mixture was stirred for 3 h at room tem-
ꢁ
1
perature. The resulting precipitate obtained was filtered off and
washed with methanol. A methanol solution of o-phen was added
slowly into the methanol suspension of the above compound and
stirred for 1 h. A yellow color solution obtained was filtered off
and kept for crystallization. Yellow crystals of 2 suitable for X-
ray analyses were obtained over a period of 15 days. Yield: 72%,
m.p. 172 °C. Anal. Found: C, 55.28; H, 3.75; N, 21.42; S, 9.08%. Calc.
shift of 67 cm in
m(C@S) in complex 2 indicates conversion of
C@S bond to CAS. The appearance of new bands near 509 and
ꢁ1
411 cm suggest formation of MAN and MAS bonds in complex
2. In addition, IR spectrum of complex 2 shows four absorptions
ꢁ1
(cm ) due to the stretching modes of NAH (3190), C@N (1609),
NAN (1050) and C@S (951), respectively indicating the presence
of two uncoordinated cocrystallized ligand molecules. The CAH
stretching vibrations of methyl group are observed in the range
for C48
H
41ClMnN16OS
3
(1044.54): C, 55.19; H, 3.95; N, 21.45; S,
(OAH) 3417, (NAH) 3190, 3261, (CAH)
(C@N) 1609,1587; (NAN) 1036,1050; (C@S) 951,
(MnAN) 509, (MnAS) 411.
ꢁ1
ꢁ1
9
3
m
.21%. IR (KBr, cm ):
046–2924,
(CAS) 883,
m
m
m
2724 to 2919 cm in the spectra of the ligands and complexes 1
m
m
m
m
and 2.
m
4.2. Crystal structure descriptions
4
. Results and discussion
The molecular structures of complexes 1 and 2 were obtained
using single crystal X-ray diffraction data. The crystallographic
data and structural refinement details are listed in Table 1. Selected
bond lengths and angles are given in Tables 2 and 3. Hydrogen
bonding parameters for complexes 1 and 2 are given in Tables 4
and 5.
The ligand 4-phenyl (phenyl-acetyl)-3-thiosemicarbazide
Hppt) and 4-amino-5-phenyl-1,2,4-triazole-3-thione (Haptt)
reacts with Mn(OAc) O/MnCl O and forms light yellow
(
2
ꢀ4H
2
2
ꢀ4H
2
precipitates in methanol solution. The above precipitate was
dissolved in methanolic solution of o-phenanthroline to form
octahedral complexes [Mn(ppt)
2
(o-phen)] (1) and [Mn(aptt)(Cl)
O (2), respectively. Acyl thiosemicarbazide
RCONHNHCSNHR) gets cyclized very easily into their correspond-
4.2.1. Crystal structure of [Mn(ppt)
2
(o-phen)] (1)
(
(
o-phen)
2
]ꢀ2HapttꢀH
2
Fig. 1 shows the molecular structure of [Mn(ppt) (o-phen)] (1)
2
together with the atom labeling scheme. The coordination sphere
of complex 1 is fulfilled by two amide carbonyl oxygen and a
deprotonated hydrazine nitrogen atom of two uni-negative biden-
tate ppt ligands and two nitrogen atoms of o-phen; forming three
five membered chelate rings. The bite angles in five membered
chelate rings with ppt {O(1)AMnAN(2) = 74.63(6)°} and o-phen
{N(4)#1AMnAN(4) = 73.18(10)°} ligands exhibit substantial devia-
tion from ideal octahedron angle (90°) suggesting a distorted octa-
hedral geometry around Mn(II) (Table 2). The six-coordinate
geometry at the manganese(II) centre is described as distorted
octahedral on account of the considerable ligand imposed devia-
tions of the cis and trans angles from the idealized octahedral
angles (90 and 180°, respectively). Similarly, the trans angles also
vary significantly O(1)AMnAO(1) (156.07) from an ideal angle of
180°. The hydrazine nitrogen MnAN bonds distances are slightly
shorter than the o-phen nitrogens indicating that the hydrazinic
nitrogen bonds stronger than the o-phen nitrogen atoms [40].
The manganese atom in complex 1 is located on a twofold axis
ing oxadiazoles when treated with weak acid or weak base [36] or
manganese(II) acetate [37] via loss of H S. However, the similar
acyl-thiosemicarbazide treated with strong acid/metal nitrate gets
converted into corresponding thiadiazole via loss of
Scheme 2) instead of oxadiazoles [38]. Often without any reactant
2
2
H O
(
acyl-thiosemicarbazide gets converted into its corresponding oxdi-
azole with due course of time in the presence of air. Thus for the
prevention of self cyclization, freshly prepared acyl-thiosemicar-
bazide should be used for complexation with metal ion [16].
Acyl/aroyl-thiosemicarbazide gets converted into 1,2,4-triazole-3-
thione in the presence of strong base NaOH (Scheme 2) [18,19].
The complex 2 obtained from the tautomerization of the ligand
with subsequent deprotonation. Schemes 3 and 4 depict the forma-
tion of ligand 4-phenyl (phenyl-acetyl)-3-thiosemicarbazide
(
Hppt) and 4-amino-5-phenyl-1,2,4-triazole-3-thiolate (Haptt)
and their complexes [Mn(ppt) (o-phen)] (1) and [Mn(aptt)(Cl)(o-
phen) O (2) containing o-phen as coligand. Complexes
]ꢀ2HapttꢀH
and 2 melt at 184 and 172 °C, respectively. The complexes are
2
2
2
0
1
which passes through the middle of C21AC21 bond. The bond