Second sphere coordination in binding large size anions: Synthesis, characterisation and X-ray structure determination of [trans-Co(en)2Cl2]C6NO2SO3H3Cl and [trans-Co(en)2Cl2]2S4O6

Article abstract of DOI:10.1016/j.molstruc.2006.02.054

In an effort to explore [trans-Co(en)₂Cl₂]⁺ as anion receptor for large size anions, 2-chloro,5-nitrobenzenesulphonate and tetrathionate ion, green coloured single crystals of [trans-Co(en)₂Cl₂]C₆NO₂SO₃H₃Cl I and [trans-Co(en)₂Cl₂]₂S₄O₆ II have been obtained by slowly mixing the separately dissolved trans-dichlorobis(ethylenediamine)cobalt(III) chloride with metal salts of 2-chloro,5-nitrobenzenesulphnic acid and tetrathionic acid in aqueous medium in 1:1 and 2:1 molar ratio, respectively. The newly synthesized complex salts were characterized on the basis of elemental analyses and spectroscopic techniques (IR, UV/visible, ¹H and ¹³C NMR). Single crystal X-ray structure determinations revealed that I crystallizes in the monoclinic space group P2₁/c and II crystallizes in the triclinic space group P over(1, ?). Supramolecular hydrogen bonding networks between ionic groups: oxygen atoms of 2-chloro,5-nitrobenzenesulphonate or tetrathionate and NH groups of coordinated ethylenediamine molecules, i.e. N-H?O^- interactions by second sphere coordination besides electrostatic forces of attraction have been observed. This suggests that [trans-Co(en)₂Cl₂]⁺ is a promising anion receptor for the weakly coordinating sulphonate and tetrathionate ions. The solubility product measurements indicate that the affinity of cationic cobaltammine [trans-Co(en)₂Cl₂]⁺ is greater for 2-chloro,5-nitrobenzenesulphonate than tetrathionate ion.

Full text of DOI:10.1016/j.molstruc.2006.02.054

Journal of Molecular Structure 794 (2006) 303–310
www.elsevier.com/locate/molstruc
Second sphere coordination in binding large size anions: Synthesis,
characterisation and X-ray structure determination of [trans-Co(en)2Cl2]
C6NO2SO3H3Cl and [trans-Co(en)2Cl2]2S4O6
a
a
b
Raj Pal Sharma a, , Rajni Sharma , Ritu Bala , L. Pretto , V. Ferretti
*
b,**
a Department of Chemistry, Panjab University, Sector 14, Chandigarh 160014, India
b Centro di Strutturistica Diffrattometrica and Dipartimento di Chimica, University of Ferrara via L. Borsari 46, I-44100 Ferrara, Italy
Received 7 January 2006; accepted 23 February 2006
Available online 24 April 2006
Abstract
In an effort to explore [trans-Co(en)2Cl2]C as anion receptor for large size anions, 2-chloro,5-nitrobenzenesulphonate and tetrathionate ion,
green coloured single crystals of [trans-Co(en)2Cl2]C6NO2SO3H3Cl I and [trans-Co(en)2Cl2]2S4O6 II have been obtained by slowly mixing the
separately dissolved trans-dichlorobis(ethylenediamine)cobalt(III) chloride with metal salts of 2-chloro,5-nitrobenzenesulphnic acid and
tetrathionic acid in aqueous medium in 1:1 and 2:1 molar ratio, respectively. The newly synthesized complex salts were characterized on the basis
of elemental analyses and spectroscopic techniques (IR, UV/visible, 1H and 13C NMR). Single crystal X-ray structure determinations revealed that
ꢀ
I crystallizes in the monoclinic space group P21/c and II crystallizes in the triclinic space group P1. Supramolecular hydrogen bonding networks
between ionic groups: oxygen atoms of 2-chloro,5-nitrobenzenesulphonate or tetrathionate and NH groups of coordinated ethylenediamine
molecules, i.e. N–H/OK interactions by second sphere coordination besides electrostatic forces of attraction have been observed. This suggests
that [trans-Co(en)2Cl2]C is a promising anion receptor for the weakly coordinating sulphonate and tetrathionate ions. The solubility product
measurements indicate that the affinity of cationic cobaltammine [trans-Co(en)2Cl2]C is greater for 2-chloro,5-nitrobenzenesulphonate than
tetrathionate ion.
q 2006 Elsevier B.V. All rights reserved.
Keywords: Cobalt(III); Second sphere coordination; Tetrathionate; Chloronitrobenzenesulphonate; Hydrogen bonding; X-ray crystallography
1. Introduction
complexes [5], Pd(II) receptor [6] and Cu(II) based receptor [7].
Recently Fe(II) complexes have been utilized as receptors for
chloride ion binding [8]. However, the preparation of such type
of receptors can often be synthetically challenging, a fact that
prompted us to look for alternative means of arranging hydrogen
bonddonatinggroupsinspace. Itoccurredtousthatsomeeasyto
prepare metal ligand complexes could be exploited [9]. As
compared to the relatively simple design principles for cation
receptors (electronic interaction and sizes), there are more
factors that can influence the effectiveness of the artificial anion
receptors. Due tothefact that anionsare larger thanisoelectronic
cations and thus have a smaller charge to radius ratio,
electrostatic interactions are less effective for anions than their
corresponding isoelectronic cations. Solvation effects are also
more prominent for anions than their isoelectronic cations. To
achieve the desired sensitivity and selectivity, the combination
of electrostatic interaction, hydrogen bonding and stacking
effects all need to be taken into consideration when designing an
artificial anionic host or sensor. Two fundamental points in the
design [10] of any architecture, are the physical features of the
units to be assembled and the means by which these items are to
The coordination of anionic guest species by hydrogen bond
donating receptors is an area of supramolecular chemistry that
continues to attract attention [1] because of the crucial role
anions play in biological processes, medicine, catalysis and
molecular assembly. Additionally, various pollutant anions are
believed to have deleterious effects on the environment.
A high proportion of the anion receptors reported so far are
organic based such as the cationic polyamines [2] but sporadic
reports are available with cationic transition metal complexes
based anion receptors, i.e. alkoxide-bridged dinuclear Zn(II)
complex [3], urea based Pt(II) receptor [4], bipyridine Ru(II)
*
**
Corresponding authors. Tel.: C91 172 2544433; fax: C91 172 2545074.
Tel.: C39 0532 291132; fax: C39 0532 240709.
E-mail addresses: rpsharma@yahoo.co.in (R.P. Sharma), frt@unife.it (V.
Ferretti).
0022-2860/$ - see front matter q 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2006.02.054

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R.P. Sharma et al. / Journal of Molecular Structure 794 (2006) 303–310
be held together. A reliable synthon to act as anion receptor
(binding agent) for molecular recognition in supramolecular
chemistry refers to molecular couples, typically functional
groups or faces of molecules, which have a high degree of
complimentarity with respect to intermolecular interactions.
Given the inherent intermolecular nature of these inter-
actions, their implementation as a means of assembling metal
complexes is a logical extension of chemistry of discrete
species. We chose to study cationic cobaltammines due to their
ease of synthesis and possibility of the NH hydrogen involving
itself in potential NH/O (anion) hydrogen bonding. We have
undertaken an extensive research programme to explore
cationic cobaltammines [Co(en)2X2]C (XZNO2 or N3) [11]
as anion receptors in continuation of our interest in cobalt(III)
complex salts [12]. This is because these cationic metal
complexes could be easily synthesized in excellent yields from
readily available materials and stored for months without any
noticeable decomposition. This paper reports the utility of
[trans-Co(en)2Cl2]C present in [trans-Co(en)2Cl2]Cl as anion
receptor for large size anions: weakly coordinating anions, i.e.
C6NO2SO3H3Cl and S4O26K. Recovery of these anions is
biologically and commercially important [13]. 2-Chloro,5-
nitrobenzene sulphonate belongs to the class of commercially
important organosulphonates, which have longstanding indus-
trial applications as surfactants, dyes, fuel and lubricant,
detergents or antioxidants [14]. They have been studied as
potential liquid crystalline [15] and non-linear optical materials
[16,17] besides pharmaceutical salt preparation [18]. Sulpho-
nate anions are a relatively unexplored class of ligands for the
construction of coordination framework because of the
misconception that sulphonate group is a poor ligand,
incapable of forming stable coordinate bond with the metal
ions [19]. Thionates and tetrathionates have traditionally been
very useful for precipitating coordination cations and useful
also for structural work. Tetrathionate salts are used as
pesticides. Therefore, the search for new and efficient anion
receptors for sulphonate and tetrathionate ion. We have
recently reported the utility of [trans-Co(en)2Cl2]C as an
anion receptor for small anion, i.e. synthesis, spectroscopic
characterisation and crystal structure of [trans-Co(en)2Cl2]N3
[20]. This is the first crystal structure of a salt containing
2-chloro,5-nitrobenzenesulphonate ion.
mulls in KBr plates. 1H and 13C NMR were recorded in
DMSO-d6 using JEOL AL 300 MHz FT NMR spectrometer
with TMS as internal reference. UV/visible spectra were
recorded using Hitachi 330 spectrometer in H2O as solvent.
2.3. Synthesis of [trans-Co(en)2Cl2]C6NO2SO3H3Cl (I)
An aqueous solution of 1 g (0.003 mol) of [trans-Co(en)2-
Cl2]Cl in 25 ml water was taken and filtered. This was added to
an equimolar quantity of (0.96 g) potassium 2-chloro,5-
nitrobenzene sulphonate dissolved in minimum amount
of water. The green crystals of [trans-Co(en)2Cl2]C6NO2SO3-
H3Cl appeared within half an hour of mixing the two reactants,
which were collected by drawing off the mother liquor and air-
dried (yield 80%). The complex is soluble in water and DMSO
but insoluble in ethanol and acetone. The newly formed
complex salt I decomposes at 212 8C. The elemental analysis is
consistent with the composition [trans-Co(en)2Cl2]C6NO2SO3-
H3Cl. Found: C, 24.8; H, 3.7; N, 14.2; Co, 12.0 (%). Calculated
C, 24.6; H, 3.9; N, 14.3; Co, 12.1. Solubility: 0.6 g/100 ml at
25 8C, KspZ1!10K4
.
2.4. Synthesis of [trans-Co(en)2Cl2]2(S4O6) (II)
One gram (0.003 mol) of [trans-Co(en)2Cl2]Cl was
dissolved in 25 ml water. In another beaker 0.47 g
(0.001 mol) of Na2S4O6 was dissolved in 10 ml of water at
room temperature. Both the solutions were mixed. The green
crystals of [trans-Co(en)2Cl2]2(S4O6) appeared within half an
hour of mixing the two reactants, which were collected by
drawing off the mother liquor and air-dried (yield 70%). The
complex is soluble in water as well as DMSO and stable in air
but insoluble in acetone and ethanol. The newly formed
complex salt II decomposes at 180 8C. The elemental analysis
is consistent with the composition [trans-Co(en)2Cl2]2(S4O6).
Found: (%) C, 13.3; H, 4.3; N, 15.5; Co, 8.0. Calculated
C, 13.2; H, 4.4; N, 15.4; Co, 8.1. Solubility: 1.2 g/100 ml at
25 8C, KspZ2!10K4
.
2.5. X-ray crystallography
Prismatic green coloured single crystals of [trans-Co(en)2-
Cl2]C6NO2SO3H3Cl (I) and [trans-Co(en)2Cl2]2(S4O6) (II)
suitable for X-ray diffraction studies were grown from water by
slow evaporation method. A single crystal with dimension
0.30!0.24!0.12 mm3 in I and 0.29!0.22!0.14 mm3 in II
were mounted along the largest dimension and used for data
collection. The data for structures I and II were collected on a
Nonius Kappa CCD diffractometer at room temperature using
2. Experimental
2.1. Materials
Analytical grade reagents were used without any further
purification. [trans-Co(en2)Cl2]Cl has been prepared according
to literature method [21].
˚
graphite-monochromated Mo Ka radiation (lZ0.71073 A)
with a 4 scan followed by u scan to fill the sphere. All
intensities were corrected for Lorentz, polarization and
absorption [23] effects. The structures were solved by direct
methods with the SIR97 program [24] and refined on F2 by
full-matrix least-squares methods with anisotropic non-H
atoms. All H atoms of structures I were found in the difference
Fourier map and refined isotropically, while in compound II to
2.2. Instruments
Cobalt was determined by standard method [22]. C, H, N
were estimated microanalytically by automatic Perkin–Elmer
2400 CHN elemental analyzer. Infrared spectrum was recorded
using Perkin–Elmer spectrum RX FT-IR system by using Nujol

R.P. Sharma et al. / Journal of Molecular Structure 794 (2006) 303–310
305
Table 1
Crystal data and structure refinement parameters for I and II
I
II
Chemical formula
Formula weight
[Co(en)2Cl2]C6NO2SO3H3Cl
[Co(en)2Cl2]2S4O6
724.32
486.64
Cell setting, space group
Unit cell dimensions
Monoclinic, P21/c
˚
Triclinic, PK1
˚
aZ13.4874(3) A
aZ9.1570(2) A, aZ79.895(1)8
˚
˚
bZ7.4501(2) A, bZ80.56 (1)8
bZ12.0630(2) A, bZ87.048(1)8
cZ12.7150(2) A, gZ71.2990(9)8
1309.71(4)
˚
˚
cZ12.0231(3) A
1146.59(5)
3
˚
Volume (A )
Z
4
2
Dx (Mg mK3
)
1.802
1.837
M (Mo Ka) (mmK1
Crystal form, colour and size (mm3)
Absorption correction
)
1.553
2.035
Prismatic, green 0.30!0.24!0.12
Empirical (SORTAV)
3.0–29.0
Prismatic, green 0.29!0.22!0.14
Empirical (SORTAV)
2.63–28.0
q Range (8)
No. of measured, independent and observed
reflections
14252, 4652, 3559
17539, 6260, 5257
Criterion for observed reflections
Rint
IO2s(I)
0.034
F2
IO2s(I)
0.035
F2
Refinement on
R[F2O2s(F2)], wR(F2), Goodness of fit
No. of observed reflections/no. of parameters
Weighting scheme
0.034, 0.080, 1.036
0.035, 0.089, 1.055
4652/302
6260/410
wZ1=½s2ðFo2ÞCð0:0509PÞ C1:5086Pꢀ, where P
wZ1=½s2ðFo2ÞCð0:0974PÞ C0:5528Pꢀ, where P
2
2
ZðFo2 C2Fc2Þ=3
ZðFo2 C2Fc2Þ=3
those belonging to the C atoms of ethylendiamine ligands or
the disordered part were given calculated positions. All other
calculations were accomplished using SHELX97 [25], WINGX [26]
and PARST [27]. Crystal data are given in Table 1 and a selection
of bond distances and angles is reported in Table 2. ORTEPIII
[28] views of the structures I and II are shown in Figs. 1 and 2,
respectively. A total of three inorganic structures containing
tetrathionate anion [29] have been retrieved from the Inorganic
Crystal Structure Database (Version 2005-01, FIZ Karlsruhe,
Germany and The National Institute of Standards and
Technology, USA) and a total of ten metallorganic structures
containing tetrathionate anion [30] have been retrieved from
the Cambridge Crystallographic Database (November 2004
version) [31].
The chemical composition of the complex salts, I and II
were initially indicated by elemental analysis. On the basis of
chloride ion test, the chloride ion was found to be absent and so
based on these studies, we proposed that the abovesaid ionic
structures may be present. These are green coloured solids and
are stable in air and light.
3.2. Measurement of solubility product
Solubility of ionic salts in water differs to a great extent
and on the basis of solubility criterion, the salts are classified
into three categories (a) solubilityO0.1 M (soluble), (b)
solubility between 0.01 and 0.1 M (slightly soluble) and (c)
solubility!0.01 M are (sparingly soluble). The solubility
measurements at room temperature show that both the
salts [trans-Co(en)2(Cl)2]C6NO2SO3H3Cl and [trans-
Co(en)2(Cl)2]2S4O6 are slightly soluble in water but it is
more for the former. [trans-Co(en)2(Cl)2]Cl is readily soluble
in water. The solubility products of [trans-Co(en)2(Cl)2]C6-
NO2SO3H3Cl and [trans-Co(en)2(Cl)2]2S4O6 are 1.0!10K4
and 2.0!10K4, which indicates that the affinity or binding of
cationic cobaltammine [trans-Co(en)2Cl2]C is greater for
2-chloro,5-nitrobenzenesulphonate ion than tetrathionate ion,
which is obviously more as compared to that of chloride, i.e.
in the order C6NO2SO3H3ClOS4O6OCl. As reported in
Section 2, when the appropriate amounts of the reactants
were mixed in minimum amount of water the crystals
3. Results and discussion
3.1. Synthesis
trans-dichlorobis(ethylenediamine)cobalt(III)chloride has
been known for a long time in the history and has played a
pivotal role in the development of coordination chemistry.
The preparation of normal trans-dichlorobis(ethylenedia-
mine)cobalt(III) salts are often difficult because of hydrolysis.
In the present work, [trans-Co(en)2Cl2]Cl and potassium
2-chloro,5-nitrobenzenesulphonate or sodium tetrathionate
were reacted in appropriate molar ratio in water with the
following expectation.
H2O
½trans-CoðenÞ2Cl2ꢀCl CKC6NO2SO3H3Cl $$% ½trans-CoðenÞ2Cl2ꢀC6NO2SO3H3Cl CKCl
ð1Þ
ðGreenÞ
ðGreenÞ
H2O
2½trans-CoðenÞ2Cl2ꢀCl CNa2S4O6 $$% ½trans-CoðenÞ2Cl2ꢀ2ðS4O6Þ C2NaCl
ð2Þ
ðGreenÞ
ðGreenÞ

306
R.P. Sharma et al. / Journal of Molecular Structure 794 (2006) 303–310
Table 2
˚
Selected bond distances (A) and angles (8) for I and II
I
II
Co1–N1
1.945(2)
1.966(2)
1.957(2)
1.965(2)
2.259(1)
2.234(1)
1.393(3)
1.384(3)
1.375(4)
1.372(3)
1.379(3)
1.381(3)
1.794(2)
1.447(2)
1.455(2)
1.450(2)
1.729(2)
1.468(3)
1.235(3)
1.219(3)
179.2(1)
89.5(1)
Co1–Cl6
2.256(1)
1.945(2)
1.960(2)
2.248(1)
1.957(3)
1.955(2)
2.256(1)
1.948(3)
1.946(2)
2.236(1)
1.959(3)
1.964(2)
2.121(1)
1.442(2)
1.443(3)
1.447(2)
2.126(1)
1.434(2)
1.432(2)
1.444(2)
2.019(1)
89.3(1)
Co1–N2
Co1–N14
Co1–N3
Co1–N18
Co1–N4
Co2–Cl5
Co1–Cl1
Co2–N15
Co1–Cl2
Co2–N17
C5–C6
Co3–Cl8
C6–C7
Co3–N13
C7–C8
Co3–N16
C8–C9
Co4–Cl11
C9–C10
Co4–N23
C5–C10
Co4–N24
C5–S1
S7–S12
S1–O3
S7–O19
S1–O4
S7–O20
S1–O5
S7–O25
Cl3–C6
S9–S10
N5–C9
S9–O22
O1–N5
S9–O34
O2–N5
S9–O27
Fig. 1. ORTEP III view and atom numbering scheme for compound I. The
displacement ellipsoids are drawn at 40% probability.
Cl1–Co1–Cl2
Cl1–Co1–N1
Cl1–Co1–N2
Cl1–Co1–N3
Cl1–Co1–N4
Cl2–Co1–N1
Cl2–Co1–N2
Cl2–Co1–N3
Cl2–Co1–N4
N1–Co1–N2
N1–Co1–N3
N1–Co1–N4
N2–Co1–N3
N2–Co1–N4
N3–Co1–N4
O3–S1–O4
O3–S1–O5
O3–S1–C5
O4–S1–O5
O4–S1–C5
O5–S1–C5
S10–S12
Cl6–Co1–N14
Cl6–Co1–N18
N14–Co1–N18
Cl5–Co2–N15
Cl5–Co2–N17
N15–Co2–N17
Cl8–Co3–N13
Cl8–Co3–N16
N13–Co3–N16
Cl11–Co4–N23
Cl11–Co4–N24
N23–Co4–N24
S12–S7–O19
S12–S7–O20
S12–S7–O25
O19–S7–O20
O19–S7–O25
O20–S7–O25
S10–S9–O22
S10–S9–O34
S10–S9–O27
O22–S9–O34
O22–S9–O27
O34–S9–O27
S9–S10–S12
S7–S12–S10
90.4(1)
89.3(1)
90.0(1)
86.2(1)
90.5(1)
89.2(1)
at 1513 cmK1 is assigned to nas (aromatic NO2) and a band at
1343 cmK1 is assigned to ns (NO2). The peak at 2953 cmK1 is
due to the ring n (C–H) vibrations. The strong absorption bands
at 1219, 1116, 618 cmK1 and a weak band at 686 cmK1 are
assigned to nas ð–SOK3 Þ, ns ð–SOK3 Þ, das ð–SOK3 Þ and n (C–S),
respectively. These bands appear at 1202, 1112, 602 and
666 cmK1 in Tl(m-NO2C6H4SO3) [34]. Tetrathionate is an
analogue of or is structurally similar to thiosulfate. The strong
absorption bands at 1113, 1003 and 641 cmK1 are assigned to
90.6(1)
90.2(1)
88.8(1)
86.2(1)
89.9(1)
91.0(1)
90.3(1)
89.1(1)
85.8(2)
86.7(1)
178.7(1)
93.0(1)
90.5(1)
90.5(1)
95.4(1)
84.8(1)
178.5(1)
85.8(1)
107.3(1)
107.3(1)
98.0(1)
113.3(1)
113.2(1)
105.4(1)
112.9(1)
105.4(1)
105.7(1)
112.6(1)
114.6(1)
115.5(1)
106.8(1)
98.9(1)
107.5(1)
115.3(2)
111.8(2)
115.1(2)
105.5(1)
105.8(1)
appeared almost immediately resulting in the formation of
title complex salts. This is because ionic products are greater
than solubility products, Ksp.
3.3. Spectroscopy
Infrared spectra of the newly synthesized complex salts
have been recorded in the region 4000–400 cmK1 and tentative
assignments have been made on the basis of earlier reports in
literature [32]. The IR band at 887 cmK1 is assigned to CH2
rocking region and a band at 1595 cmK1 to dNH2 [33] in I. The
corresponding bands appear at 886 and 1591 in II. The IR band
Fig. 2. ORTEP III view and atom numbering scheme for compound II. The
displacement ellipsoids are drawn at 40% probability. For the sake of clarity,
only two cations are shown.

R.P. Sharma et al. / Journal of Molecular Structure 794 (2006) 303–310
307
va ðSO3Þ vs ð–SOK3 Þ and 1n1 (S–S), respectively, which are
close to these frequencies in the sodium salt of the free S2OK32
ion (1120, 999 and 667) [35,36]. The lowering in stretching
frequency of S–O bond in complex salt II may be due to N–
H/O type of hydrogen bonding, which weakens S–O bond.
The electronic spectra of the newly synthesized complex
salts have been recorded in H2O. The solution state UV/visible
absorption spectra of the title complex salts show absorption at
614, 454 and 247 nm in I and at 616, 454, 246 in II. These
absorptions correspond to d–d transitions typical for octahedral
low spin cobalt(III) [37]. These values are comparable with
those of [trans-Co(en)2Cl2]SCN and [trans-Co(en)2Cl2]N3
[20], which are 618, 302, 247 nm and 612, 302, 246,
Scheme 1. Molecular structure of chloro,nitrobenzenesulphonate.
Table 3
Hydrogen bonding parameters (A, 8) for I and II
˚
1
D–H/A
D–H
D/A
H/A
!D–H/A
respectively. These transitions are from A1g ground state of
1
cobalt(III) to singlet state T1g (low energy) and from A1g
1
I
1
ground state to T2g (higher energy). In the complexes of the
N2–H2A/O3
0.85(3)
0.86(3)
0.97(3)
0.85(3)
0.94(3)
0.85(3)
3.016(2)
2.869(2)
3.053(2)
3.186(2)
3.387(2)
3.372(2)
2.17(3)
2.03(3)
2.09(3)
2.57(3)
2.63(3)
2.75(3)
172(3)
167(2)
171(2)
130(2)
138(2)
131(3)
N1–H1A/O5i
N4–H4A/O4i
N4–H4B/O1ii
N2–H2B/Cl1iii
N3–H3A/Cl1iv
II
1
type CoA4B2 (cis or trans) the T1g state is split, the splitting
[38] in trans isomer being more, thus justifying the three
absorption peaks in the title complex salts.
NMR spectra of the newly synthesized complex salts are
recorded in DMSO-d6. The chemical shift values are expressed
as d value (ppm) downfield from tetramethylsilane as an
internal standard. In 1 NMR, the signal at 5.30 ppm is attributed
to nitrogen protons of ethylenediamine while CH2 protons of
ethylenediamine [39] group are observed at 2.86 ppm in I. The
signals at 7.7, 8.2 and 8.6 in I are attributed to proton bonded to
C-5, C-6 and C-2, respectively. The 13C NMR spectrum shows
the characteristic signal at 44.8 ppm for carbons [40] of
ethylenediamine group in I. In the chloronitrobenzene
sulphonate group signals at 123.0 ppm are ascribed for C-2,
124.0 for C-5, 132.1 ppm for C-4, 137.8 for C-6, 145.5 for C-1
and 146.3 for C-3 as shown in Scheme 1. In II, the signal at
5.22 ppm is attributed to nitrogen protons of ethylenediamine
while CH2 protons of ethylenediamine group are observed at
N13–H13A/O27
N24–H24A/O34
N16–H16A/Cl5v
N14–H14A/O22vi
N14–H14B/O19vi
N13–H13B/O25vii
N15–H15A/O20vii
N23–H23A/Cl6viii
N17–H17A/O22ix
N17–H17B/Cl8xi
0.87(3)
0.98(5)
0.75(3)
0.82(4)
0.79(4)
0.82(3)
0.83(4)
0.72(5)
0.88(4)
0.83(3)
3.060(3)
3.165(4)
3.384(2)
2.986(3)
3.058(4)
2.995(3)
3.057(3)
3.264(3)
2.968(4)
3.385(2)
2.22(4)
2.34(5)
2.71(3)
2.20(3)
2.29(3)
2.20(3)
2.35(4)
2.55(5)
2.21(4)
2.63(3)
162(3)
141(4)
150(3)
160(3)
163(3)
161(3)
144(3)
173(5)
144(3)
151(3)
Symmetry transformations used to generate equivalent atoms: (i) x, yC1, z; (ii)
1Kx, yC1/2, 1/2Kz; (iii) 2Kx, 1Ky,Kz; (iv) 2Kx, yK1/2, 1/2Kz; (v) Kx,
1Ky, 1Kz; (vi) 1Kx, 1Ky, Kz; (vii) 1Kx, Ky, 1Kz; (viii) Kx, 2Ky, Kz; (ix)
xK1, y, z
Fig. 3. Packing diagram of [trans-Co(en)2Cl2]C6NO2SO3H3Cl.

308
R.P. Sharma et al. / Journal of Molecular Structure 794 (2006) 303–310
given in Table 2. The tetrathionate anion in II has an ‘elicoidal’
conformation with a S–S–S–S torsion angle of K97.0(1)8. This
conformation is conserved in all the structures retrieved from
CSD and ICSD, where the same torsion angle ranges from 91 to
1078. We also examined the Crystal Structure Database, which
does not list a single entry of X-ray structure of 2-chloro,5-
nitrobenzenesulfonate salt and therefore this is the first X-ray
structural report of a salt with this anion.
Scheme 2. Different bonding modes of sulphonate ion.
2.80 ppm. The 13C NMR spectrum shows the characteristic
signal at 44.8 ppm for carbons of ethylenediamine group in I.
3.4.2. Packing
In both structures the different units interact with each other
through intermolecular N–H/O and N–H/Cl hydrogen
bonds (Table 3). The packing pattern of I is easy to describe
by using the graph set approach [42], taking into account only
the strongest hydrogen bonds. Anions and cations are linked by
two N–H/O hydrogen bonds to form R22 (8) rings, which, in
turn, are connected in C22 (8) chains running along the b
direction by the N2–H/O3 hydrogen bond, as shown in Fig. 3.
These chains are connected along a by N4–H/O1 longer
contacts (see Table 3). The packing pattern of II is conversely
quite complicated. Each tetrathionate anion links four Co
complexes by not very strong N–H/O hydrogen bonds; these
supramolecular moieties are connected by the N13 atom, which
uses its hydrogens to form H-bonds with O25 and O27
belonging to different asymmetric units. The result is a
complicated 3D H-bonding network. This packing pattern
can be compared with the structure of a similar compound
retrieved from CSD, i.e. bis(ethylenediamine)-ammonio-
bromo-cobalt tetrathionate [30a]. Even in this case,
the tetrathionate is linked to four Co-complexes cations by
N–H/O hydrogen bond whose N/O distances are strictly
3.4. Crystal structure
3.4.1. Coordination geometry and bonding
The X-ray crystal structures of the title complex salts have
been unambiguously determined by single crystal X-ray
crystallography. The complex salt I crystallizes in monoclinic
space group P21/c and II crystallizes in triclinic space group
ꢀ
P1. ORTEPIII views of title complex salt and numbering
scheme employed are shown in Figs. 1 and 2.
The cobalt(III) cations in both structures are coordinated to
two chloride and two ethylenediamine molecules in trans
position. The geometry of the complexes is slightly distorted
octahedral because of the bite of the chelating ethylenediamine
ligands, for which N–Co–N angles are less than 908. The
counterion of the cobalt complex in I is 2-chloro,5-
nitrobenzenesulfonate in 1:1 ratio, while the asymmetric unit
of II is quite complicated, being formed by four Co complexes
positioned on an inversion centre and one tetrathionate
counterion in general position. The (C28–C33) moiety
belonging to one ethylenediamine linked to Co1 is disordered
over two almost equivalent positions (refined occupancies:
0.48 and 0.52). Co–N and Co–Cl distances of both compounds
˚
comparable with those of Table 3, ranging from 2.95 to 3.04 A.
˚
are in the range 1.945(2)–1.966(2) and 2.234(1)–2.259(1) A,
Out of the various types of structural motifs found by CSD
survey [43], two types of structural motifs are observed in the
title complex salt I. One of the simplest and most commonly
respectively, in agreement with the reported mean values [41]
for this kind of bonds. The selected bond lengths and angles are
Table 4
A comparison of bond lengths and bond angles for cation and anion in I and II
Formula of the salt
Bond lengths
Co–N
Bond angles
N–Co–N
Ref.
Co–Cl
C–N
C–C
Co–N–C
N–Co–Cl
Cation
[trans-Co(en)2Cl2]Cl
[trans-Co(en)2Cl2]NO3
[trans-Co(en)2Cl2]ClO4
[trans-Co(en)2Cl2]CoCl4
[trans-Co(en2)Cl2][trans-Co(en)2
(S2O3)2]
1.99
2.22
1.47
1.54
90
105
90
[47a]
[47c]
[47d]
[47b]
[11e]
1.99
2.26
1.46
1.59
85.6
109
–
1.95(3)
1.92(2)
1.95(17)
2.24(1)
2.24(5)
2.33(5)
1.48(6)
–
1.49(7)
–
86.2(2)
90(7)
85.7(7)
109.6(3)
–
89.9(1)
90
1.48(3)
1.50(3)
109.2(13)
89.9(5)
[trans-Co(en)2Cl2]C6NO2SO3H3Cl
1.94(2)
1.94(2)
2.23(1)
2.21(1)
1.48(3)
1.48(1)
1.50(3)
1.51(4)
85.8(1)
85.7(1)
–
–
89.2(5)
90.5(7)
This work
This work
[trans-Co(en)2Cl2] S4O6
2
Formula of the salt
S4O6
S–S
Ref.
S–O
S–S–S
O–S–S
O–S–O
Anion
K[Co(tren)(NH3)(SO4)]S4O6
[cis-Co(NH3)Br]S4O6
Cu(C20H16N4)S4O6
Na2 S4O6
2.06(2)
2.06(2)
2.12 (2)
2.11(1)
2.12(1)
1.43(4)
1.43(4)
1.45(5)
–
103.8(8)
103.4(4)
–
106.7(2)
106.2(2)
107.1(3)
–
–
[30c]
114.0(3)
114.0(3)
–
[30a]
[30b]
103.9(1)
105.5(1)
[46]
[trans-Co(en)2Cl2]C6NO2SO3H3Cl
1.44(3)
107.3(1)
113.8(1)
Present work

R.P. Sharma et al. / Journal of Molecular Structure 794 (2006) 303–310
309
occurring motifs formed between sulphonate oxygen atoms
References
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resulting in a six membered hydrogen bonded ring R12 (6)
as shown in Scheme 2b.
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