Synthesis, spectral and structural studies of a Mn(II) complex of [N′-(pyridine-4-carbonyl)-hydrazine]-carbodithioic acid ethyl ester and Mn(II) and Ni(II) complexes of [N′-(pyridine-4-carbonyl)-hydrazine]-carbodithioic acid methyl ester

Article abstract of DOI:10.1016/j.poly.2010.02.038

The new complexes [Mn(Hpchce)₂(o-phen)], {2[Mn(pchcm)(o-phen)₂]}·7H₂O and [Ni(Hpchcm)(o-phen)₂]Cl·CH₃OH with [N′-(pyridine-4-carbonyl)-hydrazine]-carbodithioic acid ethyl ester (H₂pchce) and [N′-(pyridine-4-carbonyl)-hydrazine]-carbodithioic acid methyl ester (H₂pchcm) have been synthesized, containing o-phenanthroline (o-phen) as a coligand. These ligands and their complexes have been characterized by elemental analyses, IR, magnetic susceptibility and single crystal X-ray data. H₂pchce (2), [Mn(Hpchce)₂(o-phen)] (3) {2[Mn(pchcm)(o-phen)₂]}·7H₂O (4) and [Ni(Hpchcm)(o-phen)₂]Cl·CH₃OH (5) crystallized in the monoclinic system, space group Pc, C2/c, P21/n and P21/n, respectively. The (N, O) donor sites of the bidentate ligands chelate the Mn(II) and Ni(II) centers forming a five-membered CN₂OM ring. The resulting complexes are paramagnetic and have a distorted octahedral geometry.

Full text of DOI:10.1016/j.poly.2010.02.038

Polyhedron 29 (2010) 1902–1909
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Synthesis, spectral and structural studies of a Mn(II) complex
of [N0-(pyridine-4-carbonyl)-hydrazine]-carbodithioic acid ethyl ester and Mn(II)
and Ni(II) complexes of [N0-(pyridine-4-carbonyl)-hydrazine]-carbodithioic
acid methyl ester
a
a
b
b
N.K. Singh a, , M.K. Bharty , S.K. Kushawaha , U.P. Singh , Pooja Tyagi
*
a Department of Chemistry, Banaras Hindu University, Varanasi 221 005, India
b Department of Chemistry, Indian Institute of Technology, Roorkee, Uttarakhand 247 667, India
a r t i c l e i n f o
a b s t r a c t
Article history:
The new complexes [Mn(Hpchce)2(o-phen)], {2[Mn(pchcm)(o-phen)2]}ꢀ7H2O and [Ni(Hpchcm)(o-
phen)2]ClꢀCH3OH with [N0-(pyridine-4-carbonyl)-hydrazine]-carbodithioic acid ethyl ester (H2pchce)
and [N0-(pyridine-4-carbonyl)-hydrazine]-carbodithioic acid methyl ester (H2pchcm) have been synthe-
sized, containing o-phenanthroline (o-phen) as a coligand. These ligands and their complexes have been
characterized by elemental analyses, IR, magnetic susceptibility and single crystal X-ray data. H2pchce
(2), [Mn(Hpchce)2(o-phen)] (3) {2[Mn(pchcm)(o-phen)2]}ꢀ7H2O (4) and [Ni(Hpchcm)(o-phen)2]ClꢀCH3OH
(5) crystallized in the monoclinic system, space group Pc, C2/c, P21/n and P21/n, respectively. The (N, O)
donor sites of the bidentate ligands chelate the Mn(II) and Ni(II) centers forming a five-membered
CN2OM ring. The resulting complexes are paramagnetic and have a distorted octahedral geometry.
Ó 2010 Elsevier Ltd. All rights reserved.
Received 25 July 2009
Accepted 26 February 2010
Available online 15 March 2010
Keywords:
Carbodithioic acid ester
Mn(II) complexes
Ni(II) complexes
o-Phenanthroline
Metalloaromaticity
1. Introduction
2. Experimental
Metal complexes of sulfur–nitrogen chelating ligands derived
from S-alkyl esters of dithiocarbazic acid have been studied over
the past two decades [1–10], not only because of their intriguing
coordination chemistry, but also because of their pronounced bio-
logical activities against microbes, viruses and cancer cells [2–4].
Some Schiff bases of S-alkyl esters of dithiocarbazic acid and their
complexes were found to display antifungal and antibacterial
properties [5–7]. Although several papers on the syntheses and
spectral characterization of metal complexes of dithiocarbazates
have been reported [1–10], there is no work on the dithioester
of N-acyl hydrazide, RC(O)NH–NH–C(S)SR, which also contains
an NH–C@S moiety as the S-alkyl ester of dithiocarbazic acid. Fol-
lowing our interest in the coordination properties of ligands con-
taining the H–N–C@S moiety and with the aim of elucidating the
coordination geometry of this class of biologically important li-
gands, [N0-(pyridine-4-carbonyl)-hydrazine]-carbodithioic acid
methyl (H2pchcm) and ethyl (H2pchce) esters have been synthe-
sized, and the present paper reports the syntheses, spectral
characterization and X-ray crystallography of H2pchce, [Mn
(Hpchce)2(o-phen)], {2[Mn(pchcm)(o-phen)2]}ꢀ7H2O and [Ni(Hp
chcm)(o-phen)2]ClꢀCH3OH (o-phen = o-phenanthroline).
2.1. Materials and methods
Commercial reagents were used without further purification
and all experiments were carried out in the open atmosphere.
Isonicotinic acid hydrazide (Sigma Aldrich), CS2 (S D Fine Chem-
icals, India) and KOH (Qualigens) were used as received. All the
solvents were purchased from Merk Chemicals, India and used
after purification.
2.2. Preparations of [K+(H2L)ꢁ]
The potassium N-(pyridine-4-carbonyl)-hydrazine carbodithio-
ate [K+(H2L)ꢁ] was prepared by adding CS2 (1.5 ml, 20 mmol) drop-
wise to
a suspension of isonicotinic acid hydrazide (2.7 g,
20 mmol) in methanol (30 ml) in the presence of potassium
hydroxide (1.2 g, 20 mmol). The reaction mixture was stirred con-
tinuously for 30 min and the yellow solid [K+(H2L)ꢁ] which sepa-
rated was filtered, washed with EtOH and dried. Yield: 77%. M.p.
578 K. 1H NMR (DMSO-d6; d ppm): 10.60 (s, 2H, NH), 8.65, 7.85
(m, 4H, pyridine ring). 13C NMR (DMSO-d6; d ppm): 203.03
(>C@S), 163.88 (>C@O), 131.77 (C3), 150.56 (C6), 140.27 (C5),
121.01 (C4), 118.63 (C7). IR (
cmꢁ1, KBr):
(C@O) 1676s; (N–N) 1062s; m(C@S) 993s; pyridine ring 667. Anal.
m
m(NH) 3289m, 3182m;
* Corresponding author. Tel.: +91 542 6702452.
E-mail addresses: nksingh@bhu.ac.in, singhnk_bhu@yahoo.com (N.K. Singh).
m
m
0277-5387/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2010.02.038

N.K. Singh et al. / Polyhedron 29 (2010) 1902–1909
1903
Calc. for C7H6N3OS2K (251.36): C, 33.45; H, 2.41; N, 16.72; S, 25.51.
Found: C, 33.40; H, 2.35; N, 16.76; S, 25.45%.
2.2.3. Preparation of [Mn(Hpchce)2(o-phen)] (3)
Mn(OAc)2ꢀ4H2O (0.244 g, 1 mmol) and H2pchce (2) (0.482 g,
2 mmol) were dissolved separately in 20 ml methanol, mixed to-
gether and stirred for 1 h. The yellow solid which separated was fil-
tered, washed successively with an ethanol–water mixture (50:50)
and air dried. A methanol solution of o-phen (0.20 g, 1 mmol) was
added to the methanol suspension of the above compound and
stirred for 3 h. The resulting clear yellow solution was filtered
and kept for crystallization. Pale yellow single crystals of 3 suitable
for X-ray analyses were obtained by slow evaporation of its meth-
anol solution over a period of 14 days. Yield 58%. M.p. 489 K.
2.2.1. Synthesis of N0-(pyridine-4-carbonyl)-hydrazinecarbodithioic
acid methyl ester (1)
The
N0-(pyridine-4-carbonyl)-hydrazinecarbodithioic
acid
methyl ester (H2pchcm) was synthesized by the dropwise addition
of methyl iodide (1 ml, 8 mmol) to a suspension of freshly prepared
potassium [N0-(pyridine-4-carbonyl) hydrazine] carbodithioate
[K+(H2L)ꢁ] (2 g, 8 mmol) in methanol (15 ml), and the reaction
mixture was stirred continuously for 2 h at room temperature
and filtered to remove the residue. On evaporation of the solvent
and acidification of the product with dilute CH3COOH (20% v/v),
a yellow precipitate was obtained. This was suction filtered,
washed with water and dried in vacuo. The yellow solid was crys-
tallized from MeOH. Yield (70%). M.p. 443 K. Anal. Calc. for
C8H9N3OS2 (227.30): C, 42.27; H, 3.99; N, 18.48; S, 28. 21. Found:
l
eff = 5.9 BM. Anal. Calc. for C30H28MnN8O2S4 (715.78): C, 50.29;
H, 3.91; N, 15.64; S 17.88. Found: C, 50.10; H, 3.98; N, 15.81; S,
17.62%. IR (cmꢁ1, KBr):
(NH) 3132m; (C@O) 1614s; (N–N)
1097; (C@S) 905; pyridine ring 969, 662.
m
m
m
m
2.2.4. Preparation of {2[Mn(pchcm)(o-phen)2]}ꢀ7H2O (4)
A solution of H2pchcm (1) (0.454 g, 2 mmol) in MeOH (10 ml)
was added to
MeOH solution (10 ml) of Mn(OAc)2ꢀ4H2O
C, 42.20; H, 4.05; N, 18.36; S, 28.30%. IR (
m
cmꢁ1, KBr):
(C@S) 908m; pyr-
m(NH)
3241m, 3199m; (C@O) 1691s; (N–N) 1062s;
m
m
m
a
idine ring 681; (CH3) 2926. 1H NMR (DMSO-d6; d ppm): 11.55,
11.75 (m, 2H, –NH), 7.8, 8.9 (4H, pyridine ring), 1.5 (s, 3H, –CH3).
13C NMR (DMSO-d6; d ppm): 138.82 (C3), 121.36 (C4), 150.62
(C5), 150.49 (C6), 121.28 (C7), 164.04 (>C2@O), 204.11 (>C1@S),
16.92 (C8).
(0.244 g, 1 mmol). This mixture was magnetically stirred for 3 h
at room temperature. The resulting precipitate was filtered off,
washed thoroughly with EtOH and air dried. This was suspended
in MeOH to which o-phen (0.400 g, 2 mmol) was added and mag-
netically stirred for 2 h at room temperature. The resulting clear
red solution was filtered off and kept for crystallization. Light red
single crystals of 4 suitable for X-ray analysis were obtained by
slow evaporation of the above methanolic solution over a period
2.2.2. Synthesis of N0-(pyridine-4-carbonyl)-hydrazinecarbodithioic
acid ethyl ester (2)
The N0-(pyridine-4-carbonyl)-hydrazinecarbodithioic acid ethyl
ester (H2pchce) was synthesized by the dropwise addition of
ethyl iodide (1 ml, 8 mmol) to a suspension of freshly prepared
potassium [N0-(pyridine-4-carbonyl) hydrazine] carbodithioate
[K+(H2L)ꢁ] (2 g, 8 mmol) in methanol (15 ml), and the reaction
mixture was stirred continuously for 2 h at room temperature.
The resulting yellow solution was filtered off. On evaporation of
the solvent and acidification of the residue with acetic acid (20%
v/v), the solid obtained was washed twice with portions of an eth-
anol–water mixture (50:50) and finally dried in vacuo. Colorless
needle shaped crystals of the compound suitable for X-ray analyses
were obtained by slow evaporation of its methanol solution over a
period of 12 days. Yield 62%. M.p. 438 K; Anal. Calc. for C9H11N3S2O
(241.33): C, 44.75; H, 4.55; N, 17.40; S 26.51. Found: C, 44.30; H,
of 12 days. Yield 58%. M.p. 493 K.
C64H60Mn2N14O9S4 (1407.38): C, 54.62; H, 4.29; N, 13.97; S, 9.11.
Found: C, 54.79; H, 4.30; N, 13.58; S, 9.10%. IR (
cmꢁ1, KBr):
(>C@N) 1591s; (N–N) 1096; (>C@S) 908; pyridine ring 636;
leff = 6.00 BM. Anal. Calc. for
m
m
m
m
CH3 2962. The structure was further confirmed by XRD.
2.2.5. [Ni(Hpchcm)(o-phen)2]ClꢀCH3OH (5)
NiCl2ꢀ6H2O (0.237 g, 1 mmol) and H2pchcm (1) (0.454 g,
2 mmol) were dissolved separately in 20 ml methanol, mixed to-
gether and stirred for 1 h. The brown solid which separated was fil-
tered, washed successively with an ethanol–water mixture (50:50)
and air dried. A methanol solution of o-phen (0.400 g, 2 mmol) was
added to the methanol suspension of the above compound and
stirred for 2 h. The resulting clear brown solution was filtered
and kept for crystallization. Brown single crystals of 5 suitable
for X-ray analyses were obtained by slow evaporation of its meth-
anol solution over a period of 10 days. Yield 60%. M.p. 503 K.
4.62; N, 17.65; S, 26.36%. IR (cmꢁ1, KBr):
m(NH) 3281m, 3169m;
m
(C@O) 1688s; (N–N) 1061;
m
m
(C@S) 909; pyridine ring 692. 1H
NMR (DMSO-d6; d ppm): 7.8, 8.8 (m, 4H pyridine ring), 11.60 (s,
2H, NH), 1.2 (t, 3H, J = 5.4 Hz), 3.25 (q, 2H, J = 6.3 Hz). 13C NMR
(DMSO-d6; d ppm): 203.12 (>C@S), 163.90 (>C@O), 150.88 (C1),
121.41 (C2), 150.47 (C3), 139.36 (C4), 119.65 (C5), 28.55 (C8),
14.33 (C9). MS (FAB) m/z = 242 [M]+ꢀ. The structure was further
confirmed by XRD.
l
eff = 2.87 BM. Anal. Calc. for C33H28ClN7NiO2S2 (712.90): C,
55.54; H, 3.92; N, 13.74; S, 8.97. Found: C, 55.55; H, 3.90; N,
13.75; S, 8.96%. IR ( (OH) 3427; (NH) 3169;
cmꢁ1, KBr):
(>C@O) 1676s; (N–N) 1062; (>C@S) 993. The structure was fur-
ther confirmed by XRD.
m
m
m
m
m
m
Fig. 1a. ORTEP diagram of H2pchce (2) with ellipsoids at the 30% probability level. H atoms are omitted for clarity.

1904
N.K. Singh et al. / Polyhedron 29 (2010) 1902–1909
Fig. 1b. Packing diagram of H2pchce (2) along the b axis.
2.3. Physical measurements
DMF and DMSO. The ligands 1 and 2 and the complexes 3, 4 and
5 melt at 443, 438, 489, 493 and 503 K, respectively.
Carbon, hydrogen and nitrogen contents were estimated on a
Carlo Erba 1108 model microanalyser. Magnetic susceptibility
measurements were performed at room temperature on a Cahn
Faraday balance using Hg[Co(NCS)4] as the calibrant. Electronic
spectra were recorded on a CARY 100 Varian EL 01055314 UV–
Vis spectrophotometer in MeOH. IR spectra were recorded in the
4000–400 cmꢁ1 region as KBr pellets on a Varian 3100-FT IR spec-
trophotometer. 1H and 13C NMR spectra were recorded in DMSO-d6
on a JEOL AL 300 FT NMR spectrometer using TMS as an internal
reference. The FAB mass spectra were recorded on a Jeol SX 102/
Da-600 mass spectrometer/data system using Argon/Xenon (6 kV,
10 m A0) as the FAB gas and m-nitro benzyl alcohol (NBA) as the
matrix.
4.1. IR spectra
The IR spectra of the ligands N0-(pyridine-4-carbonyl)-hydra-
zinecarbodithioic acid esters (1) and (2) show absorptions due to
the stretching modes of NH (3241–3281, 3199–3169 cmꢁ1), C@O
(1691–1688 cmꢁ1), C@S (908–909 cmꢁ1
)
and N–N (1061–
1062 cmꢁ1). The IR spectrum of complex 3 shows a band at
3132 cmꢁ1, indicating the presence of one NH group upon com-
plexation. The appearance of two new bands for
and 497 cmꢁ1 suggests bonding of Mn(II) with o-phen and one
hydrazinic nitrogen after loss of a proton. The (C@O) and (N–
N) bands suffer negative and positive shifts of 74 and 36 cmꢁ1
m(Mn–N) at 441
m
m
,
respectively, indicating that H2pchce is acting as a uninegative
bidentate ligand, bonding through the carbonyl oxygen and hydra-
zinic nitrogen atoms in complex 3. In complex 4, the absence of
3. Crystal structure determination
Data for the structures of 2 and 5 were obtained at 173(2) and
296(2) K, respectively on a Bruker three-circle diffractometer
equipped with SMART 6000 CCD software whereas those of 3
and 4 were obtained at 293(2) and 150(2) K, respectively on an Ox-
ford Diffraction Gemini diffractometer equipped with CrysAlis Pro.,
m
(N–H) bands at 3241 and 3199 cmꢁ1 shows the loss of both
hydrazinic protons, and the appearance of a new band due to
(C@N of NCO) at 1591 cmꢁ1 in place of
(C@O), suggests bonding
through the enolic oxygen and one hydrazinic nitrogen atom. Fur-
m
m
thermore, the appearance of two new bands due to
m
m
(Mn–N) at 436
(N–N) suggest
using a graphite mono-chromated Mo Ka (k = 0.71073 Å) radiation
and 452 cmꢁ1 and a positive shift of 34 cmꢁ1 in
source. The structures were solved by direct methods (SHELXL-97)
and refined against all data by full matrix least-squares on F2 using
anisotropic displacement parameters for all non-hydrogen atoms.
All hydrogen atoms were included in the refinement at geometri-
bonding of Mn(II) with the o-phen nitrogen and one hydrazinic
nitrogen atom. The IR spectrum of [Ni(Hpchcm)(o-phen)2]Clꢀ-
CH3OH (5) shows two bands at 3427 and 3169 cmꢁ1 for
m(OH) of
CH3OH and
the appearance of a new band for
bonding of Ni(II) with one hydrazinic nitrogen atom after the loss
of a proton. The (C@O) and (N–N) bands suffer negative and po-
m
(NH). The absence of one
m(NH) band together with
cally ideal positions and were refined with
a
riding model
m
(Ni–N) at 474 cmꢁ1 suggests
[11,12]. The MERCURY package and ORTEP-3 for Windows program
were used for generating the structures [13,14]. In the case of
H2pchce, having two molecules in the asymmetric unit, the ethyl
group of one molecule is disordered but the overall structure is
unambiguous.
m
m
sitive shifts, indicating bonding through the carbonyl oxygen and
one hydrazinic nitrogen atom. Thus, H2pchcm acts as an uninega-
tive bidentate ligand in complex 5 and as dinegative bidentate li-
gand in complex 4, bonding through the carbonyl/enolic oxygen
and one hydrazinic nitrogen atom [15].
4. Results and discussion
The ligands [N0-(pyridine-4-carbonyl)-hydrazine]-carbodithioic
acid methyl (H2pchcm) and ethyl (H2pchce) esters react with
Mn(OAc)2ꢀ4H2O to form yellow and red precipitates, respectively,
which dissolve in methanolic solutions of o-phen yielding
[Mn(H2pchce)2(o-phen)] (3) and {2[Mn(pchcm)(o-phen)2]}ꢀ7H2O
4.2. 1H and 13C NMR spectra
The 1H NMR spectrum of H2pchcm (1) exhibits two signals at d
11.75 and 11.55 ppm for the amide and thioamide protons,
respectively, and one signal at 1.5 ppm due to methyl protons.
Four protons of the pyridine ring appear as a multiplet between
d 7.8–8.9 ppm. The 13C NMR spectrum of 1 shows 8 signals for
(4).
[N0-(pyridine-4-carbonyl)-hydrazine]-carbodithioic
acid
methyl ester (H2pchcm) reacts with NiCl2ꢀ6H2O and o-phen to
yield [Ni(Hpchcm)(o-phen)2]ClꢀCH3OH (5). These complexes are
stable towards air and moisture. Scheme 1 depicts the formation
of the complexes which contain [pchcm]2ꢁ and [Hpchce]ꢁ as li-
gands and o-phen as the coligand. The ligands 1 and 2 are soluble
in methanol and ethanol while compounds 3, 4 and 5 dissolve in
eight carbon atoms, of which the signals at
d 204.11 and
164.04 ppm are due to the >C@S and >C@O, carbons, respectively.
The signal for the >CH3 carbons are observed at d 16.92 ppm. The
pyridine ring carbons appear at C3: 138.82, C4: 121.36, C5:
150.62, C6: 150.49 and C7: 121.28 ppm. The 1H NMR spectrum

N.K. Singh et al. / Polyhedron 29 (2010) 1902–1909
1905
O
S
H
N
EtOH
+
+
KOH
CS2
NH2
N
N
H
N
SK
N
H
RI
N
S
H
N
S
.
(i) Mn (OAc)2 4H2O
H3CH2CS
H
N
O
N
(ii) o-phen
N
N
O
MeOH
SR
Mn
H
N
N
N
N
(i) Mn(OAc)2.4H2O
H
N
N
MeOH
S
(ii) o-phen
MeOH
(i) NiCl2.6H2O
H3CH2CS
3
(ii) o-phen
N
O
N
+
N
O
N
N
3.5H2O
Mn
N
N
Cl- MeOH
HN
N
·
S
Ni
N
H3CS
N
S
N
H3CS
4
N
5
R= CH3 (1)/ C2H5 (2)
Scheme 1. Preparation of the ligands and the complexes.
of H2pchce in DMSO-d6 shows signals at d 11.60 (s, 2H), 1.2 (t,
3H, J = 5.4 Hz) and 3.25 (q, 2H, J = 6.3 Hz) ppm due to NH, CH3
and CH2 protons, respectively. The pyridine ring protons appear
as a multiplet between 7.8 and 8.8 (m, 4H) ppm. The 13C NMR
spectrum of H2pchce shows signals at d 203.12, 163.90, 28.55
and 14.33 ppm due to >(C@S), >(C@O), >CH2 and >CH3 carbons,
Table 1
Crystallographic data for H2pchce (2), [Mn(Hpchce)2 (o-phen)] (3), {2[Mn((pchcm) (o-phen)2]}ꢀ7H2O (4) and [Ni(Hpchcm) (o-phen)2]ClꢀCH3OH (5).
Compound
2
3
4
5
Empirical formula
Formula weight
T (K)
C9H11N3OS2
241.33
173(2)
C30H28MnN8O2S4
715.78
293(2)
C64H60Mn2N14O9S4
1407.38
150(2)
C33H28ClN7NiO2S2
712.90
296(2)
k (Å)
0.71073
0.71073
0.71073
0.71073
Crystal system
Space group
a (Å)
b (Å)
c (Å)
monoclinic
Pc
9.690(3)
9.125(2)
13.420(3)
97.658
1176.1(5)
4
1.363
0.430
504
monoclinic
C2/c
monoclinic
P21/n
monoclinic
P21/n
18.066(6)
11.211(3)
17.262(2)
109.266(19)
3300.4(14)
4
1.441
0.695
1476
16.671(3)
11.0491(17)
19.045 (4)
114.01(2)
3204.7(10)
2
1.460
0.595
1444
16.6963(14)
10.8245(10)
19.0139(17)
113.430(3)
3153.0(5)
4
1.502
0.877
1472
b (°)
V (Å3)
Z
qcalcd (g cmꢁ3
)
l
(mmꢁ1
F(0 0 0)
)
Crystal size (mm)
h Range for data collection (°)
Index ranges
0.66 ꢂ 0.41 ꢂ 0.29
2.12–29.47
ꢁ13 6 h 6 10, ꢁ12 6 k 6 11,
ꢁ18 6 l 6 18
0.33 ꢂ 0.26 ꢂ 0.21
3.00–25.00
ꢁ21 6 h 6 21, ꢁ13 6 k 6 13,
ꢁ20 6 l 6 20
14 342
0.33 ꢂ 0.28 ꢂ 0.25
3.06–32.62
ꢁ24 6 h 6 25, ꢁ15 6 k 6 16,
ꢁ27 6 l 6 28
38 509
0.20 ꢂ 0.18 ꢂ 0.17
1.38–28.30
ꢁ18 6 h 6 22, ꢁ14 6 k 6 12,
ꢁ25 6 l 6 24
7839
Number of reflections collected 8479
Number of independent 5100(0.0243)
reflections(Rint
2907(0.0463)
10 618(0.1814)
4546(0.0632)
)
Number of data/restraints/
parameters
5100/15/290
2907/0/208
10 618/0/425
7839/0/408
Goodness-of-fit (GOF) on F2
1.062
1.111
0.756
1.509
a,b
R1, wR2 [(I > 2
r
(I))]
0.0518, 0.1248
0.0676, 0.1334
0.574 and ꢁ0.416
0.0470, 0.1195
0.0677, 0.1334
0.808 and ꢁ0.547
0.0492, 0.0800
0.2416, 0.0999
0.619 and ꢁ0.395
0.1342, 0.2473
0.0697, 0.2473
0.265 and ꢁ0.877
a,b
R1, wR2 (all data)
Largest difference in peak and
hole (e Åꢁ3
)
P
P
a
R1
=
||Fo| ꢁ |Fc|| |Fo|.
P
P
R2 = [ w(|Fo2| ꢁ |F2c |)2/ w|F2o|2]1/2
.
b

1906
N.K. Singh et al. / Polyhedron 29 (2010) 1902–1909
z = 242 corresponds to [M+H]+ꢀ. Other important peaks at m/
z = 208 (29% intensity), 180 (91%) and 136 (48%) correspond to
the fragments formed from [M+H]+ꢀ after release of H2S (34),
HSC2H5 (62) and HCS2CH2CH3 (105), respectively.
Table 2
Selected bond lengths (Å) and angles (°) for H2pchce (2).
Bond lengths
S(1A)–C(7A)
S(1A)–C(8A)
S(2A)–C(7A)
O(1A)–C(6A)
N(2A)–C(6A)
N(2A)–N(3A)
N(3A)–C(7A)
C(1A)–C(6A)
C(8A)–C(9A)
1.743(4)
1.812(18)
1.662(3)
1.219(4)
1.346(4)
1.394(3)
1.331(4)
1.496(4)
1.468(19)
S(1BA)–C(7B)
S(1BB)–C(8BB)
S(2BA)–C(7B)
O(1B)–C(6B)
N(2B)–C(6B)
N(2B)–N(3B)
N(3B)–C(7B)
C(1B)–C(6B)
C(8BA)–C(9BA)
1.778(4)
1.811(19)
1.672(5)
1.217(4)
1.335(4)
1.385(3)
1.341(4)
1.505(4)
1.468(19)
4.4. Electronic spectra and magnetic moments
[Mn(Hpchce)2(o-phen)] (3) shows
a magnetic moment of
5.9 BM which indicates the presence of five unpaired electrons.
It shows one low intensity absorption at 15 220 cmꢁ1 assigned
to the 6A1g ? 4T1g transition, characteristic of a distorted octahe-
dral Mn(II) complex. The other two bands observed at 28 170 and
38 160 cmꢁ1 may be assigned to intraligand/charge transfer tran-
sitions [17]. The magnetic moment of 6.00 BM for {2[Mn(pchcm)
(o-phen)2]}ꢀ7H2O (4) suggests a high spin Mn(II) center with five
unpaired electrons. Its electronic spectrum shows a band at
25 510 cmꢁ1, which may be assigned to a charge transfer transi-
Bond angles
C(7A)–S(1A)–C(8A)
C(6A)–N(2A)–N(3A)
C(7A)–N(3A)–N(2A)
O(1A)–C(6A)–N(2A)
O(1A)–C(6A)–C(1A)
N(2A)–C(6A)–C(1A)
N(3A)–C(7A)–S(2A)
N(3A)–C(7A)–S(1A)
S(2A)–C(7A)–S(1A)
C(9A)–C(8A)–S(1A)
102.5(18)
118.4(2)
122.3(3)
121.8(3)
121.7(3)
116.3(3)
119.2(3)
113.5(2)
127.2(2)
112.3(16)
C(7B)–S(1BB)–C(8BB)
C(8BB)–S(1BB)–C(9BB)
C(6B)–N(2B)–N(3B)
C(7B)–N(3B)–N(2B)
O(1B)–C(6B)–N(2B)
O(1B)–C(6B)–C(1B)
N(2B)–C(6B)–C(1B)
N(3B)–C(7B)–S(2BB)
N(3B)–C(7B)–S(1BA)
S(2BA)–C(7B)–S(1BA)
C(9BA)–C(8BA)–S(1BB)
105.3(4)
112.2(17)
119.2(2)
120.2(3)
122.6(3)
121.8(3)
115.6(3)
128.7(3)
108.0(2)
126.7(3)
112.4(16)
tion.
A magnetic moment of 2.87 BM for [Ni(Hpchcm)(o-
phen)2]ClꢀCH3OH (5) and the presence of a band at 17 200 cmꢁ1
,
assigned to the 3A2g ? 3A1g(F) transition, suggests a distorted
octahedral geometry for the complex.
4.5. Crystal structure description of H2pchce (2)
Table 3
Hydrogen bonds for H2pchce [Å and °] (2).
The crystallographic data and structural refinement details
are given in Table 1 and selected bond distances and bond an-
gles are given in Table 2. Hydrogen bonding parameters of the
ligand are given in Table 3. Fig. 1a shows the ORTEP diagram
of the H2pchce (2) ligand with the atomic numbering scheme
and Fig. 1b shows the packing diagram of the ligand along the
b axis. The structure of H2pchce is stabilized by intermolecular
N–HꢀꢀꢀN and N–HꢀꢀꢀO hydrogen bonding, responsible for produc-
ing a three dimensional structure (Fig. 1b). In addition to this,
there is a C–HꢀꢀꢀO weak interaction between the carbonyl oxygen
and pyridine ring hydrogen at position 3. The distances and an-
gles for H2pchce are close to those reported earlier [18,19]. The
N–HꢀꢀꢀN hydrogen bonds are formed between the pyridine nitro-
gen and hydrazinic hydrogen, and N–HꢀꢀꢀO hydrogen bonds are
formed between the hydrazinic hydrogen and carbonyl oxygen.
D–HꢀꢀꢀA
d(D–H)
d(HꢀꢀꢀA)
d(DꢀꢀꢀA)
\(DHA)
N(2A)H(2AB)ꢀꢀꢀO(1B)#1
N(3A)H(3AB)ꢀꢀꢀN(1A)#2
N(2B)–H(2BB)ꢀꢀꢀO(1A)
N(3B)H(3BB)ꢀꢀꢀN(1B)#3
0.88
0.88
0.88
0.88
1.93
2.06
1.95
2.01
2.754(4)
2.850(4)
2.744(4)
2.793(4)
155.1
149.3
149.8
148.0
#1 x ꢁ 1, y, z; #2 x, ꢁy + 3, z ꢁ 1/2; #3 x, ꢁy + 2, z ꢁ 1/2.
respectively. The pyridine ring carbons appear at C1: 150.88, C2:
121.41, C3: 150.47, C4: 139.36 and C5: 119.65 ppm [16].
4.3. Mass spectrometry
The ligand H2pchce is identified by its FAB mass spectrum
which shows many peaks due to various fragments. A peak at m/
Fig. 2. ORTEP diagram of the Mn(II) complex 3 with ellipsoids at the 30% probability level. H atoms are omitted for clarity.

N.K. Singh et al. / Polyhedron 29 (2010) 1902–1909
1907
The C–S bond distances of 1.743(4) and 1.662(3) Å (Table 2) in
H2pchce agree well with those in related compounds, being
intermediate between 1.82 Å for a C–S single bond and 1.56 Å
for a C@S double bond [20].
carbonyl oxygen in coordination with Mn(II). Compound 3 is
quite stable in the solid state due to electron delocalization
and weak intermolecular C–HꢀꢀꢀS interactions between the thioe-
ther sulfur of one molecule and a methyl hydrogen atom of a
nearby molecule. The crystal structure in turn is stabilized by
intramolecular and intermolecular hydrogen bonding.
p
4.6. Crystal structure description of [Mn(Hpchce)2 (o-phen)] (3)
4.7. Crystal structure description of {2[Mn(pchcm)(o-phen)2]}ꢀ7H2O
(4)
Fig. 2 shows the ORTEP diagram of complex 3 with the atomic
numbering scheme. The structural refinement data related to
complex 3 are listed in Table 1 and selected bond distances and
bond angles are listed in Table 4. The metal center in complex
3 is coordinated in a N4O2 core by two uninegative bidentate li-
gands using hydrazine nitrogen (N1, after loss of a proton) and
carbonyl oxygen atoms. The manganese atom in complex 3 is lo-
cated on a twofold axis which passes through the middle of the
C15–C150 bond. The distances found within the chelate rings
are intermediate between single and double bond lengths and
are also longer or shorter than the corresponding bond lengths
in H2pchce (2). The average bond lengths in complex 3 are: O1–
C6 = 1.241(4) (L), N2–C6 = 1.322(4) (S), N2–N3 = 1.391(4) (S),
N3–C7 = 1.329(4) (S) Å (L = longer, S = shorter), and these suggest
considerable delocalization of charge [21]. The (N, O) donor sites
of the bidentate ligand chelates the Mn(II) center to form a five-
membered CN2OMn ring. The resulting complex has a distorted
octahedral geometry. The Mn–O bond length in (3) is 2.173 Å
and the Mn–N bond lengths are 2.257 and 2.270 Å for Mn–N
(hydrazinic) and Mn–N (o-phen), respectively. The shorter Mn–
N (hydrazinic) bond length as compared to Mn–N (o-phen) indi-
cates that the hydrazinic nitrogen bonds more strongly than the
o-phen nitrogen. The bond angles N(4)–Mn–N(3) 162.83(9)° and
N(4)–Mn–N(4) 73.70(13)° indicate distortion from an ideal octa-
hedral geometry [22]. In the complex 3 the C(7)–N(3) and C(6)–
N(2) bond distances show partial double bond character due to
Fig. 3a shows an ORTEP diagram of complex 4 together with the
atom numbering scheme. The structural refinement data related to
complex 4 are listed in Table 1 and selected bond distances and
bond angles are listed in Table 5. For complex 4, the multiplicities
of O1W, O2W and O4W refined to values close to 1 while for O3W
the value refined too close to 0.5. Therefore O3W is in partial occu-
pancy. The (N, O) donor sites of the dinegative bidentate ligand
chelate the Mn(II) center to form a five-membered CN2OMn ring.
The average bond lengths in complex 4 are: O1–C2 = 1.301(12)
delocalization of
p electrons throughout the whole chelate ring
[23]. Both metal chelate rings present in complex 3 exhibit some
degree of metalloaromaticity [24,25]. Both chelate rings around
Mn(II) formed by (Hpchce)ꢁ are almost orthogonal to each other,
forming a dihedral angle of 88.62°. In the complex the chelate
rings and the pyridine rings lie nearly in the same plane, forming
a dihedral angle of 14.44°. Due to the deprotonation of the hydra-
zinic hydrogen, the intermolecular hydrogen bonding present be-
tween the pyridine nitrogen and hydrazinic hydrogen in the
ligand of 2 disappears in complex 3. The N–HꢀꢀꢀO intermolecular
hydrogen bonding is also absent due to involvement of the
Fig. 3a. ORTEP diagram of compound 4. Hydrogen atoms and solvent molecules are
not shown.
Table 5
Selected bond lengths (Å) and angles (°) for {2[Mn((pchcm)(o-phen)2]}ꢀ7H2O (4).
Bond lengths
Mn1–O1
Mn1–N1
Mn1–N4
Mn1–N6
Mn1–N7
Mn1–N5
S1–C1
2.152(7)
2.169(9)
2.247(10)
2.275(8)
2.289(10)
2.292(9)
1.711(10)
1.801(11)
S2–C32
O1–C2
N1–C1
N1–N2
N2–C2
N3–C6
N3–C5
N4–C8
1.794(11)
1.301(12)
1.293(11)
1.414(11)
1.309(12)
1.336(14)
1.342(16)
1.313(13)
Table 4
Selected bond lengths (Å) and angles (°) for [Mn((Hpchce)2(o-phen)] (3).
Bond lengths
Mn1–O1
Mn1–N4
Mn1–N3
S1–C7
S2–C7
N2–C6
2.173(2)
2.257(3)
2.270(3)
1.685(3)
1.768(4)
1.322(4)
N2–N3
N3–C7
N4–C10
N4–C14
O1–C6
C8–C9
1.391(4)
1.329(4)
1.328(4)
1.352(4)
1.241(4)
1.453(7)
S2–C1
Bond angles
O1–Mn1–N1
O1–Mn1–N4
N1–Mn1–N4
N1–Mn1–N6
N4–Mn1–N6
O1–Mn1–N7
N1–Mn1–N7
N4–Mn1–N7
N6–Mn1–N7
O1–Mn1–N5
N1–Mn1–N5
N4–Mn1–N5
N6–Mn1–N5
N7–Mn1–N5
C1–S2–C32
73.67(3)
101.68(3)
104.51(3)
109.47(3)
92.87(3)
91.30(3)
96.49(4)
157.68(3)
72.77(3)
88.72(3)
161.58(3)
73.27(3)
88.96(3)
89.13(4)
103.21(5)
C2–O1–Mn1
C1–N1–N2
C1–N1–Mn1
N2–N1–Mn
C2–N2–N1
C6–N3–C5
C19–N4–Mn1
C17–N5–Mn1
C18–N5–Mn1
N1–C1–S1
N1–C1–S2
S1–C1–S2
O1–C2–N2
O1–C2–C3
N2–C2–C3
111.77(6)
114.61(8)
129.94(7)
114.54(5)
110.52(8)
115.77(9)
116.09(7)
127.85(9)
114.83(6)
121.28(8)
117.48(8)
121.24(5)
126.33(9)
117.83(8)
115.83(9)
Bond angles
O1–Mn1–O1
O1–Mn1–N4
O1–Mn1–N4
N4–Mn1–N4
O1–Mn1–N3
O1–Mn1–N3
N4–Mn1–N3
N4–Mn1–N3
N3–Mn1–N3
C7–S2–C8
176.01(12)
92.51(8)
90.68(9)
73.70(13)
73.53(9)
103.73(9)
162.83(9)
96.07(10)
96.93(14)
106.0(2)
119.3(3)
113.1(3)
C7–N3–Mn1
N2–N3–Mn1
C10–N4–Mn1
C14–N4–Mn1
C6–O1–Mn1
O1–C6–N2
O1–C6–C5
N2–C6–C5
N3–C7–S1
138.2(2)
108.23(19)
126.6(2)
115.29(20)
116.0(2)
121.7(3)
120.8(3)
117.5(3)
126.2(3)
109.8(2)
123.9(2)
113.6(4)
N3–C7–S2
S1–C7–S2
C9–C8–S2
C6–N2–N3
C7–N3–N2

1908
N.K. Singh et al. / Polyhedron 29 (2010) 1902–1909
Fig. 3b. Triangular arrangement of the three water molecules in the crystal structure of complex 4.
Fig. 4. Ortep diagram of compound 5. Hydrogen atoms and solvent molecules are not shown.
(L), N2–C2 = 1.309(12) (S), N1–N2 = 1.414(11) (L), N1–
C1 = 1.293(11) (S) Å (L = longer, S = shorter), which suggest consid-
erable delocalization of charge [23]. A large increase in the C–O
bond length as compared to complex 3 suggests a change of C@O
double bond to C–O single bond on account of enolization and
the subsequent release of a proton for the formation of a chelate
ring with Mn(II). The resulting complex has a distorted octahedral
geometry. Masui suggested that if active electron delocalization
within a metal-N-heterocyclic chelate ring is present, it would ex-
hibit some degree of metalloaromaticity [24,25]. In the complex
the chelate rings and the pyridine rings lie nearly in the same
plane, forming a dihedral angle of 19.97°. The bond distances for
Mn–O, Mn–N and Mn–N(phen) are 2.152(7), 2.179(9) and
2.275(8) Å, respectively, which are comparable to the bond lengths
reported for [Mn3(O2CCH3)6(N–N)2] (where N–N = o-phen) [26]
and [Mn2(phen)(Hdcbi)]n (Hdcbi = 4,5-dicarboxyimidazole) [27].
Three of the four water molecules present in the lattice form a tri-
angular structure out of which one water molecule links the com-
plex through O–HꢀꢀꢀS and another by O–HꢀꢀꢀO (carbonyl)
intermolecular hydrogen bonding to form
a supramolecular
arrangement (Fig. 3b). The fourth water molecule is linked to the
pyridine nitrogen of one unit and a CH3 hydrogen of another unit.
4.8. Crystal structure description of [Ni (Hpchcm) (o-phen)2]ClꢀCH3OH
(5)
Fig. 4 shows the ORTEP diagram of complex 5 together with the
atom numbering scheme. The structural refinement data related to
complex 5 are listed in Table 1 and selected bond distances and
bond angles are listed in Table 6. In compound 5, the chlorine atom
(Cl1) and the atoms of methanol (C33 and O2) were found to be
disordered over two positions with occupancies of 0.57:0.43,

N.K. Singh et al. / Polyhedron 29 (2010) 1902–1909
1909
Table 6
m)(o-phen)2]ClꢀCH3OH (5). These data can be obtained free of
charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or
from the Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk.
Selected bond lengths (Å) and angles (°) for [Ni(Hpchcm)(o-phen)2]ClꢀCH3OH.
Bond lengths
Ni1–O1
Ni1–N5
Ni1–N3
Ni1–N1
Ni1–N2
Ni1–N4
S1–C26
S2–C26
2.037(3)
2.094(4)
2.081(4)
2.108(4)
2.112(4)
2.118(4)
1.690(5)
1.799(5)
S2–C25
O1–C27
N5–C26
N6–C27
N6–N5
N7–C30
N7–C31
C33–O2
1.805(5)
1.300(5)
1.312(5)
1.297(5)
1.405(5)
1.337(7)
1.304(7)
1.407(15)
Acknowledgements
Authors are thankful to Prof. Ray. J. Butcher, Department of
Chemistry, Howard University, 525 College Street NW, Washing-
ton, DC 20059, USA for his help in solving the crystal structure of
compound 2 and to Prof. P. Mathur, Department of Chemistry,
I.I.T, Bombay, Powai, Mumbai, India for analyzing the crystal struc-
tures of compounds 3 and 4.
Bond angles
O1–Ni1–N1
O1–Ni1–N5
O1–Ni1–N3
O1–Ni1–N2
O1–Ni1–N4
N3–Ni1–N5
N3–Ni1–N1
N3–Ni1–N2
N5–Ni1–N2
N1–Ni1–N2
N3–Ni1–N4
N5–Ni1–N4
N1–Ni1–N4
170.76(14)
78.39(13)
95.83(14)
92.21(14)
89.23.(13)
98.32(14)
93.39(14)
167.78(15)
92.29(14)
78.58(15)
79.46(14)
167.8(14)
91.82(14)
N2–Ni1–N4
C26–S2–C25
C27–O1–Ni1
C26–N5–N6
C26–N5–Ni1
N6–N5–Ni1
C27–N6–N5
N5–C26–S1
N5–C26–S2
S1–C26–S2
O1–C27–C28
N6–C27–O1
N6–C27–C28
91.50(14)
103.7(3)
109.3(3)
114.1(4)
135.9(3)
109.6(2)
112.9(3)
123.6(4)
115.0(3)
121.4(2)
118.3(4)
125.6(4)
116.0(4)
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0.95:0.05 and 0.41:0.59, respectively. The (N, O) donor sites of the
uninegative bidentate ligand chelate the Ni(II) center to form a
five-membered CN2ONi ring. The resulting complex has a distorted
octahedral geometry. The average bond lengths in complex 5 are:
O1–C27 = 1.300(5), N6–C27 = 1.297(5), N5–N6 = 1.405(5), N5–
C26 = 1.312(5) Å, which suggest considerable delocalization of
charge [23]. Complex 5 is stable in the solid state due to
p electron
delocalization and weak intermolecular C–HꢀꢀꢀCl interactions be-
tween CH3 and the phenyl ring hydrogens as well as by O–HꢀꢀꢀO
interactions between the OH of methanol and the carbonyl oxygen
from the chelate ring.
5. Conclusions
Two new ligands [N0-(pyridine-4-carbonyl)-hydrazine]-carbo-
dithioic acid methyl (H2pchcm) (1) and ethyl (H2pchce) (2) esters
and their [Mn(Hpchce)2(o-phen)] (3), {2[Mn(pchcm)(o-phen)2]}ꢀ
7H2O (4) and [Ni(Hpchcm)(o-phen)2]ClꢀCH3OH (5) complexes have
been synthesized. The crystal structure of complex 3 is stabilized
through weak intermolecular C–HꢀꢀꢀS interactions between the thi-
oether sulfur of one molecule and a methyl hydrogen atom of a
nearby molecule. The crystals of 3, 4 and 5 are stabilized by inter-
molecular and intramolecular hydrogen bonding.
6. Supplementary data
CCDC 682361, 682360, 715927 and 737839 contain the sup-
plementary crystallographic data for H2pchce (2), [Mn(Hpchce)2
(o-phen)] (3) {2[Mn((pchcm)(o-phen)2]}ꢀ7H2O (4) and [Ni(Hpchc-
[26] S.G. Baca, Y. Sevryugina, R. Clerac, I. Malaestean, N. Gerbeleu, M.A. Petrukhina,
Inorg. Chem. Comm. 8 (2005) 474.
[27] X. Zhang, D. Huang, F. Chen, C. Chen, Q. Liu, Inorg. Chem. Comm. 8 (2004) 662.