Mn(II) complexes of N0-(2-methoxybenzoyl)hydrazine carbodithioic acid ethyl ester: Synthesis, spectral and structural characterization

Article abstract of DOI:10.1007/s11243-012-9640-1

Two new Mn(II) complexes [Mn(Hmbhce)2- (o-phen)] (1) and [Mn(Hmbhce) ₂(bpy)] (2) based on N0-(2- methoxybenzoyl)hydrazine carbodithioic acid ethyl ester (H2mbhce) have been synthesized by reacting Mn(OAc)2- 4H2O with H2mbhce in the presence of

Full text of DOI:10.1007/s11243-012-9640-1

Transition Met Chem
DOI 10.1007/s11243-012-9640-1
0
Mn(II) complexes of N -(2-methoxybenzoyl)hydrazine
carbodithioic acid ethyl ester: synthesis, spectral
and structural characterization
Mamata Singh
Aarti Singh Sujata Kashyap
Nand K. Singh
•
Manoj K. Bharty
•
•
•
Udai P. Singh
•
Received: 22 May 2012 / Accepted: 30 July 2012
Ó Springer Science+Business Media B.V. 2012
Abstract Two new Mn(II) complexes [Mn(Hmbhce)2-
0
participate in redox changes [1]. The complexes of manga-
nese are of great current interest because of its rich bio-
chemistry [2, 3] and remarkable magnetic properties [4–6].
Molecules containing manganese can function as nanoscale
magnetic materials/nanoscale magnets below a critical
temperature. Such single-molecule magnets (SMMs) can
display magnetization hysteresis, quantum tunneling of
magnetization (QTM) and quantum phase interference
(QPI), and as such they are promising new materials for data
storage and quantum computing. Manganese clusters often
display abnormally large spin ground states as compared to
other 3d transition metal clusters, and this coupled with a
large zerofield splitting parameter (D) (derived from the
(
o-phen)] (1) and [Mn(Hmbhce) (bpy)] (2) based on N -(2-
2
methoxybenzoyl)hydrazine carbodithioic acid ethyl ester
(
H mbhce) have been synthesized by reacting Mn(OAc) ꢀ
2
2
4
H O with H mbhce in the presence of o-phen/bpy. The
2 2
complexes have been characterized by elemental analyses,
magnetic susceptibility measurement, IR, UV–Vis and
single crystal X-ray data. Both complexes [Mn(Hmbhce)2-
(
o-phen)] and [Mn(Hmbhce) (bpy)] crystallize in mono-
2
clinic system with space group P 21/c and P 21/n,
respectively. The single crystal X-ray structures of 1 and 2
-
show that the Mn(II) center is bonded with two (Hmbhce)
through carbonyl oxygen and deprotonated hydrazinic
nitrogen, plus two nitrogen atoms from one o-phen/bpy co-
ligand. The crystal structures of complexes 1 and 2 are
stabilized by weak intramolecular N–HꢀꢀꢀO hydrogen
bonding and C–Hꢀꢀꢀp interactions giving supramolecular
architectures.
3
?
presence of Jahn–Teller distorted Mn ions) gives rise to
the superparamagnetic-like property of a barrier to magne-
tization relaxation [6]. The most important natural role of
manganese is in the oxidation of water in green plant pho-
tosynthesis, where its presence in photosystem II is essential
[
7, 8]. The manganese complexes containing N-heterocyclic
0
bases (o-phen, 2,2 -bpy) are often employed to mimic the
function and structure of the active sites of enzymes where
manganese is predominantly coordinated by N,O donors
from amino acid side chains [9]. The dithiocarbazates and
their substituted derivatives remain of interest to researchers
because of their wide variation in structure and properties.
Their complexes have tunable electronic behavior that may
result in nonlinear optical (NLO) materials with unique
magnetic and electrochemical properties [10, 11] and show
selective biological activity [12–14]. Substituted dithiocar-
bazates containing heteroatoms behave as bidentate [10, 11],
tridentate [12, 13] or multidenate [14] chelating agents.
Some work has been done on the carbodithioic acid esters
Introduction
The chemistry of manganese is the subject of current interest
due to its involvement in a number of enzymes, such as
superoxide dismutase, peroxidase and dioxygenase that
M. Singh ꢀ M. K. Bharty ꢀ A. Singh ꢀ N. K. Singh (&)
Department of Chemistry, Banaras Hindu University,
Varanasi 221005, India
e-mail: singhnk_bhu@yahoo.com
[
15–17], containing the –NH–C(S)– moiety as is the case of
S. Kashyap ꢀ U. P. Singh
S-alkyl esters of dithiocarbazate. Following our interest
in the potential chelating ability of ligands containing the
Department of Chemistry, Indian Institute of Technology,
Roorkee 247667, Uttarakhand, India
123

Transition Met Chem
–
NH–C(S)– and–NH–C(O)– groups toward biological
Preparation of [Mn(Hmbhce)
(bpy)] (2)
2
metals, we have synthesized and structurally characterized
0
the Mn(II) complexes of N -(2-methoxy benzoyl)hydra-
Mn(OAc) (0.244 g, 1 mmol) and
2
ꢀ4H
2
O
H mbhce
2
zinecarbodithioic acid ethyl ester containing o-phenanthroline
0
(0.540 g, 2 mmol) were dissolved separately in 20 ml
methanol, mixed together and stirred for 1 h. The yellow
solid that separated was filtered off, washed successively
with ethanol–water mixture (50:50) and suspended in
(o-phen) and 2,2 -bipyridyl (bpy) as the co-ligands.
0
Experimental section
methanol to which a methanol solution of 2,2 -bipyridyl
(0.20 g, 1 mmol) was added and stirred for 3 h at room
Commercial reagents and solvents were used without fur-
ther purification. All experiments were carried out in open
atmosphere. Methyl 2-methoxy-benzoate was purchased
from Sigma Aldrich and used as such. Carbon disulfide and
hydrazine hydrate (SD Fine Chemicals, India) and the
solvents (Merck Chemicals, India) were used in the syn-
theses. Carbon, hydrogen, nitrogen and sulfur contents
were estimated on a CHN Model CE-440 Analyser and on
an Elementar Vario EL III Carlo Erba 1108. Following
standard procedures, the complexes were analyzed for their
metal content, after decomposition with a mixture of con-
centrated HNO and HCl, followed by concentrated H SO
4
temperature. The resulting clear yellow solution was fil-
tered and kept for crystallization. Yellow single crystals of
2 suitable for X-ray analyses were obtained by slow
evaporation of the above methanol solution over a period
of 5 days. Yield 58 %; m.p. 185 °C, leff = 5.9 BM. Anal.
Calc. for C32
H34MnN O S (749.87): C, 51.2; H, 4.5; N,
6 4 4
11.2; S 17.1; Mn, 7.3. Found: C, 51.3; H, 4.4; N, 11.3; S,
-
1
16.9; Mn, 7.3 %. IR (cm , KBr): m(NH) 3147 m, m(C=O)
1598 s, m(N–N) 1098, m(C=S) 903. UV–Vis [kmax, DMSO,
nm]: 242, 296, 347.
Crystal structure determination and refinement
3
2
[
18]. Magnetic susceptibility measurement was performed
at room temperature on a Cahn Faraday balance using
Hg[Co(NCS)4-] as the calibrant. Electronic spectra were
recorded on a Shimadzu 1700 UV–Vis spectrophotometer
as Nujol mulls. The IR spectra were recorded in the
Crystals suitable for X-ray analyses of the complexes 1 and 2
were grown at room temperature. The X-ray data collection
and processing for 1 and 2 were performed on a Bruker
Kappa Apex-CCD diffractometer using graphite mono-
-
1
˚
4
,000–400 cm region as KBr pellets on a Varian Excal-
chromated Mo Ka radiation (k = 0.71073A) at 296 K.
ibur 3100 FT-IR spectrophotometer.
Crystal structures were solved by direct methods. Structure
solution, refinement and data output were carried out with the
SHELXTL program [19, 20]. All non-hydrogen atoms were
refined anisotropically. Hydrogen atoms were placed at
geometrically calculated positions by using a riding model.
The DIAMOND and ORTEP-3 for windows program were
used for generating structures [21, 22]. Hydrogen bonding
interactions in the crystal lattice were calculated with both
SHELXTL and MERCURY [23] (Tables 1, 2).
Synthesis of H mbhce
2
0
The preparation and characterization of N -(2-methoxy-
benzoyl)hydrazine carbodithioic acid ethyl ester is dis-
cussed elsewhere [16].
Synthesis of [Mn(Hmbhce) (o-phen)] (1)
2
The complex 1 was prepared by stirring a solution of
H mbhce (0.540 g, 2 mmol) in MeOH and CHCl (25 ml,
Results and discussion
2
3
0
5
0 v/v) with a solution of Mn(OAc) ꢀ4H O (1 mmol) in
The ligand N -(2-methoxybenzoyl)hydrazine carbodithioic
2
2
MeOH for 2 h at room temperature followed by the addi-
tion of o-phen (1 mmol) that yielded a clear yellow solu-
tion. This solution was filtered and kept for crystallization
for 15 days, which gave yellow transparent crystals of 1.
Yield 61 %; m.pt. 245 °C, leff = 6.10 BM. Anal. Calcd. for
C H MnN O S (773.89): C, 52.8; H, 4.4; N, 10.9; S,
acid ethyl ester (H
4H O to form yellow precipitates that dissolve in methanolic
solutions of o-phen/bpy yielding [Mn(Hmbhce) (o-phen)]
(1) and [Mn(Hmbhce) (bpy)] (2). The complexes are stable
2
mbhce) ester reacts with Mn(OAc)
2
ꢀ
2
2
2
toward air and moisture. Scheme 1 depicts the formation of
-
the complexes that contain [Hmbhce] as ligand and o-phen/
3
4
34
6 4 4
1
6.6; Mn, 7.1. Found : C, 52.6; H, 4.4; N, 10.6; S, 16.5;
bpy as the coligand. The complexes 1 and 2 are soluble in
methanol and other solvents such as DMF and DMSO and
melt at 245 and 185 °C, respectively.
The complexes were fully characterized by magnetic
susceptibility measurements, IR, UV–Vis and X-ray spec-
troscopies. The analytical data for the complexes
-
1
Mn, 7.1 %. IR (m cm , KBr): 3,180 m(NH) m; 1,613
m([C=O) s; 1501 thioamide I [b(NH) ? m(CN)] s; 1,300
thioamide II [m(CN) ? b(NH)] s; 1,101 m(N–N) m; 963
m([C=S); 2,933 m(CH ); 2,870 m(CH ); UV–Vis [kmax,
3
2
DMSO, nm]: 629, 393, 220.
1
23

Transition Met Chem
˚
Table 1 Crystallographic data and structure refinement for com-
plexes 1 and 2
Table 2 Selected molecular dimensions (A and °) in
[Mn(Hmbhce)
2
(o-phen)] (1)
Empirical formula
Formula weight
T(K)
C
34
H
34
N
6
O
4
S
4
Mn
C
32
H
34MnN
6
O
4
S
4
Bond length
Bond angle
773.89
296(2)
749.87
Mn(1)–N(1)
Mn(1)–N(2)
Mn(1)–N(3)
Mn(1)–N(5)
Mn(1)–O(1)
Mn(1)–O(2)
S(1)–C(21)
S(2)–C(22)
S(2)–C(21)
S(3)–C(32)
S(4)–C(33)
S(4)–C(32)
N(3)–N(4)
2.279(9)
2.281(8)
2.254(7)
2.291(8)
2.189(6)
2.164(6)
1.662(10)
1.728(16)
1.785(9)
1.700(10)
1.697(17)
1.731(11)
1.401(9)
1.274(10)
1.263(10)
1.342(10)
1.439(10)
N(1)–Mn(1)–N(5)
N(2)–Mn(1)–N(1)
N(2)–Mn(1)–N(5)
N(3)–Mn(1)–N(1)
N(3)–Mn(1)–N(2)
N(3)–Mn(1)–N(5)
O(1)–Mn(1)–N(1)
O(1)–Mn(1)–N(2)
O(1)–Mn(1)–N(3)
O(1)–Mn(1)–N(5)
O(2)–Mn(1)–N(1)
O(2)–Mn(1)–N(2)
O(2)–Mn(1)–N(3)
O(2)–Mn(1)–N(5)
O(2)–Mn(1)–O(1)
C(20)–O(1)–Mn(1)
C(31)–O(2)–Mn(1)
110.3(3)
71.8(3)
296(2)
˚
k (Mo Ka) (A)
0.71073
0.71073
Monoclinic
P 21/n
102.0(3)
101.7(3)
107.3(3)
142.0(3)
87.7(3)
Crystal system
Space group
Monoclinic
P 21/c
˚
a (A)
15.069(7)
18.380(9)
13.744(7)
98.295(18)
3767(3)
4
10.6611(5)
27.1457(12)
12.4914(5)
102.848(2)
3524.5(3)
4
˚
b (A)
˚
c (A)
159.3(3)
72.8(2)
b (°)
3
˚
V (A )
88.1(3)
Z
155.0(3)
83.2(3)
q
calc/(mg/m)
1.365
1.413
-
1
)
l (mm
F(000)
0.617
0.657
86.2(3)
1,604
1,556
O(2)–C(31)
O(1)–C(20)
O(3)–C(14)
O(3)–C(13)
73.5(3)
3
Crystal size (mm )
0.27 9 0.25x0.23 0.23 9 0.21x0.19
117.3(2)
117.6(5)
118.1(6)
h range for data
collections (°)
Index ranges
1.37–25.00
1.50–26.43
-17 B h B 17
-13 B h B 13
-33 B k B 33
-15 B l B 13
49,431
-
21 B k B 21
16 B l B 16
-
-1
is supported by positive shifts of 12–15 cm in m(N–N) in
both complexes [24].
No of reflections collected 57,881
No of independent
reflections
6,635
7,256
The magnetic moment values of 6.10–5.90 B.M. for
complexes 1 and 2 suggest the presence of high spin Mn(II)
with five unpaired electrons. The electronic spectrum of the
complex 1 shows a d–d band at 629 nm, which may be
No of parameters
427
428
2
Goodness-of-fit on F
a
1.791
1.137
b
R
1
, wR
2
[(I [ 2r(I)]
(all data)
0.1139, 0.2995
0.2263, 0.3475,
1.599, 0.771
0.0553, 0.1617
0.980, 0.1881
0.749, -0.618
6
4
a
R
b
assigned to the A ? T for a six coordinated high spin
1
g
1g
1
, wR
2
Mn(II) center possessing distorted octahedral geometry
[25]. The high energy bands at 393 and 220 nm are due to
intraligand transitions. The complex 2 shows only high
energy bands at 242, 296 and 347 nm, which are due to
intraligand or charge transfer transitions.
Largest difference in peak
-
3
)
˚
and hole (eA
a
R
1
= RkF
o
| - |F
2
c
k/R |F
o
|; I
o
o
[ 2 r (I )
b
2 2
2 2 1/2
wR = [R w(F - F ) /R w(F ) ]
2
o c o
(
see ‘‘Experimental section’’) corroborated well with their
Description of crystal structure of (1)
respective formulations.
The ligand H mbhce contains the –NH–C(S)– group that
2
Figure 1 shows
a
DIAMOND view of the
[Mn(Hmbhce) (o-phen)] complex together with the het-
may adopt either the thione –NH–C(S)– or thiol –N=C(–SH)
form. However, the ligand adopts the thione form in the free
state as well as in the complexes. This is evident by the
2
eroatom numbering scheme. The metal center in complex 1
is coordinated by a N O core from two uninegative
4
2
-1
-
absence of the m(SH)bandin the regionca. 2,500 cm and by
bidentate ligands (Hmbhce) using hydrazinic nitrogens
(N3 and N5, after loss of a proton from each ligand) and
carbonyl oxygens (O1 and O2). The deprotonated hydra-
-1
the presence of m(NH) at 3,180 and 3,147 cm in complexes
and 2, respectively. Comparison of the main vibrational
bands of H mbhce was used to establish its ligating behavior
1
-
zinic nitrogen and carbonyl oxygen of (Hmbhce) form a
2
in complexes 1 and 2. The IR spectra of both complexes show
five membered chelate ring around the Mn(II) center,
which is also chelated by two N atoms of the o-phen co-
ligand. The two ligands are coordinated to the Mn(II)
center in opposite directions with respect to each other to
minimize the steric hindrance due to similar groups
(Fig. 2). The angle O1–Mn1–O2 = 117.2(2) involving
the carbonyl oxygen of both ligands indicates notable
-1
bands in the region of 3,180–3,147 and 1,613–1,598 cm
assigned to m(NH) and m(CO), respectively. A negative shift of
-
1
3
2–47 cm in m(C=O) and the appearance of two new bands
-1
for m(Mn–N) at 520–585 cm suggests bonding of Mn(II)
with bpy/o-phen and one hydrazinic nitrogen after loss of a
proton. Theinvolvementofthehydrazinicnitrogeninbonding
123

Transition Met Chem
O
O
S
NH2
H
EtOH
N
N
H
+
CS
2
+ KOH
N
H
SK
OCH
3
OCH
3
2 5
C H I
H
3
CO
S
H
O
N
S
(i) Mn (OAc) O
.4H
2 2
H
H
3
CH
2
CS
O
N
N
(
ii) o-phen
N
H
SCH CH
3
O
2
MeOH
Mn
N
OCH
3
N
H
N
N
S
OCH
3
(i) Mn(OAc) .4H O
2 2
MeOH
(
ii) bpy
H CH CS
3
2
H
3
CO
1
S
H
N
H
3
CH
2
CS
O
N
O
N
Mn
N
H
N
S
N
OCH
3
H CH CS
3 2
2
Scheme 1 Synthesis of ligand and complexes 1 and 2
deviation from theoretical value of 90° and suggests dis-
tortion from an octahedral geometry. The bond angles
formed by coordination of the ligands range between
7
2.6(2)° (O1–Mn1–N3) and 73.5° (N5–Mn1–O2) for cis
angles and 142.1(2)° (N3–Mn1–N5) and (O1–Mn1–
O2) = 117.2(2)° for trans angles. The planar o-phen ring
bound to the Mn(II) center provides a five membered Mn–
N2–C9–C5–N1 chelate ring. The bite angle (N2–Mn1–N1)
of 71.7(3)° formed by the coordination of o-phen is found
to be smaller than the reported value of 74.1(3)° for the
complex [Mn(l-Cl) (o-phen)] [26] and is significantly
2
n
smaller than the ideal value of 90°. Various bond distances
found within the chelate rings are intermediate between
single and double bond lengths and shorter or longer than
the corresponding bond lengths in comparison with the free
ligand. The average bond lengths in complex 1 are as
˚
follows: Mn1–O2 = 2.162(5)A, O2–C31 = 1.268(8)A,
˚
˚
˚
C31–N6 = 1.299(9)A, N6–N5 = 1.399(9)A, N5–Mn1 =
˚
.293(6)A for the chelate ring Mn1O2C31N6N5 and Mn1–
2
˚
O1 = 2.190(5)A, O1–C20 = 1.263(8)A, C20–N4 =
˚
˚ ˚ ˚
.325(19)A, N4–N3 = 1.400(8)A, N3–Mn1 = 2.250(6)A
1
Fig. 1 Molecular structure of complex 1. For clarity, hydrogen atoms
are omitted except H1, H4, H6 and H12, showing unusual intramo-
lecular C–Hꢀꢀꢀp interactions with Mn(II) chelate ring and N–HꢀꢀꢀO
intramolecular hydrogen bonding
for chelate ring Mn1O1C20N4N3, which suggest consid-
erable delocalization of charge in the chelate ring [27].
CHꢀꢀꢀp interactions are the weakest hydrogen bonds that
1
23

Transition Met Chem
SF ,i gy .e 2l lo Ow ;n eM dn i,mg er ne se ino ;n Ca lg ,c hb al ai nc kin complex 1 formed through C–Hꢀꢀꢀp interactions (black dotted line). Color code: C, gray; N, blue; O, red;
operate between a soft acid CH and a soft or intermediate
base p system that plays significant roles in crystal packing,
host–guest chemistry, self-assembly and chiral recognition.
The soft base p system, which acts as a CH acceptor, is
comprised not only of an organic moiety such as a double
bond, a triple bond or a delocalized aromatic ring, but also
of a metal chelate ring of suitable transition-metal com-
plexes. On the basis of the reported metalloaromaticity of
benzoquinonediimine ruthenium complex [28], this kind of
CHꢀꢀꢀp (planar chelate ring) interaction in complex 2 is
thought to be a kind of structural evidence for the metal-
loaromaticity of such planar chelate rings. The orientation
of the ortho hydrogen atom of o-phen toward both chelate
rings causes intramolecular C–Hꢀꢀꢀp interaction in the
molecule [15] (Fig. 1). Transition metal complexes in
which bonding of the ligand takes place through carbonyl
oxygen and nitrogen and also bonded with N-heterocyclic
˚
Table 3 Hydrogen bond parameters [A and °] in [Mn(Hmbhce)
(o-phen)] (1)
2
D–HꢀꢀꢀA
d(D–H)
d(HꢀꢀꢀA)
d(DꢀꢀꢀA)
\(DHA)
N6–H6ꢀꢀꢀO4
0.850
0.860
0.930
0.959
0.930
0.930
0.930
1.997
1.982
2.926
2.671
2.895
2.646
2.288
2.626
2.655
3.797
3.562
3.797
3.435
3.125
130.16
132.54
156.42
154.68
156.42
143.15
149.56
N4–H4ꢀꢀꢀO3
C17–H17ꢀꢀꢀS3
C24–H24CꢀꢀꢀO2
C15–H15ꢀꢀꢀC27
C26–H26ꢀꢀꢀC20
C11–H11ꢀꢀꢀH23A
[Mn(Hmbhce)
[Mn(Hmbhcd)
]
[16], [Mn(Hmbhcd) (o-phen)], and
2
2
n
0
(2,2 -bpy)(l-OAc) ] [17]. Similarly, the
2
˚
bond distances Mn–O [2.162–2.190(5)A], Mn–N [2.285(7)–
˚
2.293(6)A], and Mn–Nphen (2.288–2.292A) are almost equal
2
˚
to the bond lengths reported for [Mn
(where N–N = o-phen) [31] and [Mn
(O
CCH
(phen)(Hdcbi)]
)
(N–N)
]
3
2
3
6
2
0
bases such as o-phen or 2,2 -bpy are prone to exhibit me-
talloaromaticity [29–33] (Fig. 1). The Mn–Ocarbonyl
2
n
=
(Hdcbi = 4,5-dicarboxyimidazole) [32]. There are two types
˚
.162(5)A,
˚
2.190(5)A
˚
Mn–Nhy = 2.293(6)A,
2
2
and
of intermolecular hydrogen bonding, that is, C17–
˚
˚
.250(6)A are comparable to the bond lengths found for
˚
H17ꢀꢀꢀS3 = 2.926A and C24–H24ꢀꢀꢀO2 = 2.671A (Fig. 3).
˚
recently reported compounds [Mn(Hpchc) (o-phen)] [15],
2
The SꢀꢀꢀH hydrogen bonding distance of 2.926A is
Fig. 3 The crystal packing of
[Mn(Hmbhce) (o-phen)]
2
showing intermolecular
hydrogen bonding
˚
H17ꢀꢀꢀS3 = 2.926A,
˚
H24ꢀꢀꢀO2 = 2.671A and short
contacts C26–H26ꢀꢀꢀC20 and
C11–H11ꢀꢀꢀH23A
123

Transition Met Chem
Fig. 4 Double strand chain of complex 1 due to H17ꢀꢀꢀS3 hydrogen bonding between thione sulfur and 2-methoxyphenyl hydrogen
Fig. 5 ORTEP plot of
Mn(Hmbhce) (bpy)] showing
[
2
atomic numbering scheme with
ellipsoids of 30 %
probability.(Hydrogen atoms
are omitted for clarity)
comparable to that reported for [Mn(Hpchc) (o-phen)] and
2
remaining part of the complex [Mn(Hmbhce) ] is embedded
2
˚
Mn(Hpchce) (o-phen)] (2.935–2.995A) [15, 34]. Similarly,
[
(Fig. 3).
2
C24–H24ꢀꢀꢀO2 is also comparable to the value of C–HꢀꢀꢀO
˚
hydrogen bonding (2.641A) [15]. The weak C–HꢀꢀꢀC =
Description of crystal structure of (2)
Figure 5 shows an ORTEP diagram of the complex
g
˚
˚
3
.028A is close to the value of C–Hꢀꢀꢀp = 3.00A (Fig. 2)
[
28]. The C–Hꢀꢀꢀp interactions between two molecules of
[Mn(Hmbhce) (o-phen)] gives a one dimensional chain
2
[Mn(Hmbhce) (bpy)] (2) together with the atom number-
2
(
Fig. 2) and provides stability to the crystal packing. Each
molecule of the complex is also stabilized by the intramo-
lecular N–HꢀꢀꢀO hydrogen bonding (Fig. 1, Table 3). The
hydrogen bonding and short contacts link the one dimensional
chains into three dimensional arrays (Fig. 4). In the crystal
ing scheme. In complex 2, Mn(II) has distorted octahedral
coordination with pronounced distortion (Table 4). The
complex 2 contains a pair of monodeprotonated ligands
coordinated to Mn(II) via hydrazinic nitrogen and carbonyl
oxygen. Selected bond distances and bond angles of com-
plex 2 are compiled in Table 4. Hydrogen bonding
parameters of the complex 2 are given in Table 5. The
packing of [Mn(Hmbhce) (o-phen)], o-phen rings lie at top of
2
the structure forming two layers in which the skeleton of the
1
23

Transition Met Chem
˚
Table 4 Selected molecular dimensions (A and °) in [Mn(Hmbhce)
bpy)] (2)
2
-
bond lengths in complex 2 are as follows: O1–
C18 = 1.238(4), N3–C18 = 1.333(4), N3–N4 = 1.397(4),
(
˚
N4–C19 = 1.312(4)A, which suggest considerable delo-
Bond length
Bond angle
calization of charge [27]. The (N, O) donor sites of the
bidentate ligand chelate the Mn(II) center to form a five
Mn(1)–O(3)
Mn(1)–O(1)
Mn(1)–N(6)
Mn(1)–N(4)
Mn(1)–N(1)
Mn(1)–N(2)
S(1)–C(19)
S(2)–C(20)
S(2)–C(19)
S(3)–C(30)
S(4)–C(31)
S(4)–C(30)
O(1)–C(18)
O(3)–C(29)
N(3)–N(4)
2.190(2)
2.194(2)
2.244(3)
2.248(3)
2.274(3)
2.306(3)
1.675(4)
1.767(4)
1.775(4)
1.682(4)
1.765(5)
1.773(4)
1.238(4)
1.248(4)
1.397(4)
O(3)–Mn(1)–O(1)
O(3)–Mn(1)–N(6)
O(1)–Mn(1)–N(6)
O(3)–Mn(1)–N(4)
O(1)–Mn(1)–N(4)
N(6)–Mn(1)–N(4)
O(3)–Mn(1)–N(1)
O(1)–Mn(1)–N(1)
N(6)–Mn(1)–N(1)
N(4)–Mn(1)–N(1)
O(3)–Mn(1)–N(2)
O(1)–Mn(1)–N(2)
N(6)–Mn(1)–N(2)
N(4)–Mn(1)–N(2)
N(1)–Mn(1)–N(2)
114.3(9)
72.5(10)
89.7(10)
84.8(10)
72.2(9)
membered CN OMn ring. The Mn–O bond length in (2) is
2.194A, and the Mn–N bond lengths are 2.244 and 2.306A
2
˚ ˚
for Mn–N (hydrazinic) and Mn–N (bpy), respectively. The
shorter Mn–N (hydrazinic) bond length as compared to
Mn–N (bpy) indicates that the hydrazinic nitrogen bonds
more strongly than the bpy nitrogen. The bond angles
N(2)–Mn–N(4) 100.24(11)° and N(2)–Mn–N(1) 71.04(10)°
indicate distortion from an ideal octahedral geometry [35].
In the complex 2, the C(18)–N(3) and C(19)–N(4) bond
distances show partial double bond character due to delo-
calization of p electrons throughout the whole chelate ring
[36]. In view of available information, both metal chelate
rings present in complex 2 exhibit some degree of metal-
loaromaticity [37]. The chelate rings around Mn(II) formed
142.2(11)
87.2(10)
158.4(10)
95.7(11)
113.3(11)
157.9(10)
87.5(10)
112.1(11)
100.2(11)
71.0(10)
-
by the (Hmbhce) are almost orthogonal to each other,
forming a dihedral angle of 69.25°. The bond distances for
˚
Table 5 Hydrogen bond parameters [A and °] in [Mn(Hmbhce)
2
(bpy)]
Mn–O, Mn–N and Mn–N(bpy) are 2.194(2), 2.244(3) and
˚
(2)
2.306(3)A, respectively, which are comparable to the bond
D–HꢀꢀꢀA
d(D–H)
d(HꢀꢀꢀA)
d(DꢀꢀꢀA)
\(DHA)
0
lengths reported for [Mn(Hmbhcd) (2,2 -bpy)(l-OAc) ]
2
2
[
20]. The delocalized charge in the chelate ring forms an
N3–H2ꢀꢀꢀO3
C11–H11BꢀꢀꢀS3
C2–H2ꢀꢀꢀC31
0.859
0.960
0.930
2.039
2.894
2.285
2.660
3.832
3.903
128.48
165.97
164.90
unusual intramolecular C–Hꢀꢀꢀp interaction with the ortho
0
hydrogen of the adjacent phenyl ring of 2,2 -bpy (Fig. 6)
˚
having distances of 3.000 and 2.837A [27, 28]. In the
complex, the chelate rings and the phenyl rings lie nearly in
the same plane, forming a dihedral angle of 6.83°. The
values of the dihedral angles suggest that the extended
coplanar ring systems of the two ligands approach each
other orthogonally and shows an unsymmetrical coordi-
nation of the two ligands. The complex 2 is quite stable in
the solid state due to p electron delocalization and weak
intermolecular N–HꢀꢀꢀO interaction between hydrazine
hydrogen and methoxy oxygen (Fig. 7). In addition, com-
˚
plex 2 is stabilized by C–HꢀꢀꢀS (SꢀꢀꢀH = 2.894A) interac-
tions between the thione sulfur of one molecule and
methoxy hydrogen atom of a neighboring molecule (Fig. 7,
Table 3).
Conclusion
Two new mixed ligand complexes [Mn(Hmbhce) (o-phen)]
2
Fig. 6 Crystal packing of complex 2 showing C–Hꢀꢀꢀp interaction
metal center in complex 2 is coordinated in an N O core
(
1) and [Mn(Hmbhce) (bpy)] (2) of N-(2-methoxyben-
2
zoyl)hydrazine carbodithioic acid ethyl ester have been
synthesized and characterized by spectroscopic and single
crystal X-ray techniques. Both complexes involve delocal-
ization in the chelate ring and show an unusual intramolec-
ular C–Hꢀꢀꢀp (chelate ring) interaction, providing structural
support for metalloaromaticity. The crystal structures of the
4
2
by two uninegative bidentate ligands using hydrazine
nitrogen (N1, after loss of proton) and carbonyl oxygen.
The distances found within the chelate rings are interme-
diate between single and double bond lengths. The average
123

Transition Met Chem
Fig. 7 N–HꢀꢀꢀO and C–HꢀꢀꢀS hydrogen bonding in complex 2 leading to linear chain structure
complexes are stabilized by intermolecular and intramolec-
ular hydrogen bonding.
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0.1107/S0108270186093071
0. Zhou H-P, Li D-M, Wang P, Cheng L-H, Gao Y-H, Zhu Y-M,
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Supplementary material
1
2. Tarafder MTH, Ali AM, Wee DJ, Azahari K, Silong S, Crouse
KA (2000) Transition Met Chem 25:456. doi:10.1023/A:10070
Crystallographic data for the structural analysis have been
deposited with the Cambridge Crystallographic Data Cen-
ter, 719089 and 874035 for 1 and 2. Copies of this infor-
mation may be obtained free of charge at www.ccdc.
cam.ac.uk/conts/ retrieving.html [or from the Cambridge
Crystallographic Data Center, 12, Union Road, Cambridge
CB2 1EZ, UK]. Fax: C44 1223 336 066. Email: deposit@
ccdc.cam.ac.uk.
6
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