Electrochemical synthesis and structural characterization of heteroleptic cobalt(II) complexes of N-2-pyridyl sulfonamide ligands

Article abstract of DOI:10.1016/j.poly.2006.03.004

Neutral heteroleptic cobalt complexes [CoL₂L′] (L′ = 2,2′-bipyridine or 1,10-phenanthroline) with the anionic form of a series of methyl-substituted N-2-pyridylsulfonamide ligands (HL) have been synthesized by the electrochemical oxidation of the metal in an acetonitrile solution of the sulfonamide ligand and the corresponding coligand L′. The compounds were characterized by microanalysis, vibrational and electronic spectroscopy and some examples by single-crystal X-ray diffraction. The crystal structures of the compounds show the metal in a distorted octahedral geometry, [N6] or [N4O2], that depends on the position of the substituent on the pyridine ring.

Full text of DOI:10.1016/j.poly.2006.03.004

Polyhedron 25 (2006) 2673–2682
www.elsevier.com/locate/poly
Electrochemical synthesis and structural characterization of
heteroleptic cobalt(II) complexes of N-2-pyridyl sulfonamide ligands
a
a,
b
a
*
´
´
´
´
´
Inmaculada Beloso , Jesus Castro , Jose A. Garcıa-Vazquez , Paulo Perez-Lourido ,
b
b
Jaime Romero , Antonio Sousa
a
Departamento de Quı´mica Inorga´nica, Universidade de Vigo, Campus de As Lagoas-Marcosende, Edificio de Ciencias Experimentais,
E-36310 Vigo, Pontevedra(Galicia), Spain
b
Departamento de Quı´mica Inorga´nica, Universidade de Santiago de Compostela, E-15782 Santiago, Galicia, Spain
Received 19 January 2006; accepted 10 March 2006
Available online 18 April 2006
Abstract
Neutral heteroleptic cobalt complexes [CoL2L0] (L0 = 2,20-bipyridine or 1,10-phenanthroline) with the anionic form of a series of
methyl-substituted N-2-pyridylsulfonamide ligands (HL) have been synthesized by the electrochemical oxidation of the metal in an ace-
tonitrile solution of the sulfonamide ligand and the corresponding coligand L0. The compounds were characterized by microanalysis,
vibrational and electronic spectroscopy and some examples by single-crystal X-ray diffraction. The crystal structures of the compounds
show the metal in a distorted octahedral geometry, [N6] or [N4O2], that depends on the position of the substituent on the pyridine ring.
ꢀ 2006 Elsevier Ltd. All rights reserved.
Keywords: Electrochemical synthesis; Cobalt complexes; Sulfonamide ligands; Crystal structures
1. Introduction
ence of bulky substituents on these ligands stabilises the
metal complexes. Moreover, these ligands are very versatile
in terms of their coordination modes; they can act as
anionic monodentate systems via the nitrogen pyridine
atom (I) [9], amide nitrogen atom (II) [10], as chelate sys-
tems (III [11,12] and IV [13,14]) or as a bridge between
two metal atoms (V) [15,16], (VI) [17] and (VII) [17]. In this
way these complexes have variable nuclearities and great
structural diversity (Scheme 2).
Given the information outlined above, we studied a ser-
ies of N-2-pyridyl-sulfonamide ligands with different sub-
stituents on the pyridine and/or benzene rings (Scheme 3)
with the aim of investigating whether the position of the
substituent has any influence on the coordinative behavior
of these ligands and, consequently, on the structure of the
corresponding amido cobalt complexes.
The coordination chemistry of metal complexes contain-
ing pyridine-functionalized amide ligands (Scheme 1) has
received a great deal of attention [1–7].
One particular class of ligands of this type is represented
by the pyridine sulfonamide ligands (Scheme 2). Interest in
the synthesis of metal complexes with these ligands arises,
in part, from the fact that they can easily be made due
the electron-withdrawing effect of the sulfonyl substituent,
which increases the acidic character of the NH group and
makes the process of ligand deprotonation easier [8]. Fur-
thermore, variation of the substituents in these ligands is
facile. This latter feature provides the possibility of tailor-
ing the bite angle and degree of steric hindrance present
in the ligand and, in addition, it is believed that the pres-
The complexes were prepared using an electrochemical
procedure in which the metal was the anode of a cell con-
taining an acetonitrile solution of differently substituted
N-2-pyridylsulfonamide ligands and the corresponding
*
Corresponding author. Tel.: +34 986812278; fax: +34 986813798.
E-mail addresses: jesusc@uvigo.es (J. Castro), qiansoal@usc.es (A.
Sousa).
0277-5387/$ - see front matter ꢀ 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2006.03.004

2674
I. Beloso et al. / Polyhedron 25 (2006) 2673–2682
products and were used as supplied. Cobalt (Aldrich) was
used as 2 · 2 cm plates.
R=CH3
R'=H, SiMe3
R
R'
N
N
2.1. Preparation of ligands
Scheme 1.
Ligands were prepared by reaction of the corresponding
amine and the sulfonyl chloride in 1:1 ratio following a pre-
viously described method [14]. Analytical and spectro-
scopic data for the ligands are given below.
R
R
R
SO2R'
SO2R'
I
SO2R'
III
N
N
N
N
N
N
M
M
M
II
2.1.1. HMs6mepy
Anal. Calc. for C15N2H18O2S: C, 62.1; H, 6.2; N, 9.6; S,
11.0. Found: C, 62.3; H, 6.4; N, 9.5; S, 10.9%. H NMR
(CDCl3, ppm) 2.24(s), 3H, CH3(p-tolyl); 2.37(s), 3H,
CH3(py); 2.69(s) 6H, CH3(o-tolyl); 6.55(d), 1H, py;
6.74(d), 1H, py; 6.88(s), 2H, tolyl; 7.37(d), 1H, py;
9.40(b), 1H, NH. IR (KBr, cmꢀ1): 3236(w), 2931(w),
1616(vs), 1533(m), 1362(vs), 1136(vs). EI MS: m/z: 291
(4%, M+); 108 (13%, M+ꢀ{O2S-mesityl}).
O
S R'
O
1
R
R
SO2R'
V
N
N
N
N
N
M
M
M
M
IV
O
S R'
O
O
S R'
O
R
R
N
N
N
M
M
M
2.1.2. HTs6mepy
Anal. Calc. for C13N2H14O2S: C, 59.5; H, 5.4; N, 10.7; S,
12.2. Found: C, 58.8; H, 5.6; N, 10.6; S, 12.3%. H NMR
VI
VII
Scheme 2.
1
(CDCl3, ppm) 2.41(s), 3H, CH3(py); 2.36(d), 3H, CH3(tolyl);
6.60(d), 1H, py; 7.46(dd), 1H, py; 7.06(d), 1H, py; 7.22(d),
2H, tolyl; 7.79(d), 2H, tolyl; 9.95(b), 1H, NH. IR
(KBr, cmꢀ1): 3231(w), 2958(w), 1612(vs), 1534(m),
1369(s), 1134(s). EI MS: m/z: 262 (6%, M+); 108 (3%,
M+ꢀ{O2S-tolyl}).
Code
R'
R
HTs3mepy
HMs3mepy
HTs6mepy
HMs6mepy
4-MeC6H4
2,4,6-Me3C6H2
4-MeC6H4
3-Me
R
3-Me
6-Me
6-Me
SO2R'
N
H
N
2,4,6-Me3C6H2
2.1.3. HTs3mepy
Anal. Calc. for C13N2H14O2S: C, 59.5; H, 5.4; N, 10.7; S,
12.2. Found: C, 58.7; H, 5.7; N, 10.2; S, 11.8%. H NMR
Scheme 3.
1
coligand, 2,20-bipyridine or 1,10-phenanthroline. The pres-
ence in the electrolytic cell of the two species allows the syn-
thesis of mixed compounds in one step.
(CDCl3, ppm) 2.15(s), 3H, CH3(py); 2.35(d), 3H, CH3(tolyl);
6.50(d), 1H, py; 7.40(d), 1H, py; 7.49(d), 1H, py; 7.85(d), 2H,
tolyl; 7.21(d), 2H, tolyl; 12.14(b), 1H, NH. IR (KBr, cmꢀ1):
3248(m), 2951(w), 1594(s), 1544(s), 1342(s), 1126(s). EI MS:
m/z: 262 (8%, M+); 108 (20%, M+ꢀ{O2S-tolyl}).
2. Experimental
2.1.4. HMs3mepy
Acetonitrile, dichloromethane, 2-amino-3-picoline,
2-amino-6-picoline, p-toluenesulfonyl chloride, 2-mesityle-
nesulfonyl chloride, 2,20-bipyridine, 1,10-phenanthroline
monohydrate and all other reagents were commercial
Anal. Calc. for C15N2H18O2S: C, 62.1; H, 6.2; N, 9.6;
S, 11.0. Found: C, 61.3; H, 6.0; N, 9.3; S, 11.2%. 1H
NMR (CDCl3, ppm) 2.15(s), 3H, CH3(py); 2.25(s), 3H,
Table 1
Experimental conditions for the electrochemical synthesis
Compound expected
Proligand HL
Coligand L0
Amount of
HL (g)
Amount of
L0 (g)a
Initial
Voltaje (V)b
Metal
dissolved (mg)
Electrochemical
efficiency (mol Fꢀ1
)
[Co(Ts3mepy)2bipy]
[Co(Ts3mepy)2phen]
[Co(Ms3mepy)2bipy]
[Co(Ms3mepy)2phen]
[Co(Ts6mepy)2bipy]
[Co(Ts6mepy)2phen]
[Co(Ms6mepy)2bipy]
[Co(Ms6mepy)2phen]
a
HTs3mepy
HTs3mepy
HMs3mepy
HMs3mepy
HTs6mepy
HTs6mepy
HMs6mepy
HMs6mepy
bipy
phen
bipy
phen
bipy
phen
bipy
phen
0.150
0.150
0.165
0.165
0.150
0.150
0.165
0.165
0.045
0.052
0.045
0.052
0.045
0.052
0.045
0.052
8
7
10
11
8
7
8
7
14.4
15.9
15.3
15.9
15.9
15.1
18.4
16.8
0.44
0.48
0.46
0.48
0.48
0.45
0.56
0.50
Plus [NMe4]ClO4 (ca. 20 mg).
b
Voltage to produce a current of 10 mA.

I. Beloso et al. / Polyhedron 25 (2006) 2673–2682
2675
CH3(p-tolyl); 2.71(s), 6H, CH3(o-tolyl); 6.47(d), 1H, py;
6.89(s), 2H, tolyl; 7.36(d), 1H, py; 7.42(d), 1H, py;
12.33(b), 1H, NH. IR (KBr, cmꢀ1): 3222(m), 2940(w),
1595(s), 1544(s), 1338(s), 1098(s). EI MS: m/z: 291 (100%,
M+); 108 (10%, M+ꢀ{O2S-mesityl}).
2.2. Preparation of complexes: general procedure
The complexes were obtained by an electrochemical pro-
cedure [18]. A solution of a mixture of the sulfonamide and
the coligand, with a small amount of tetraethylammonium
perchlorate (ca. 10 mg) as a current carrier, was electro-
lyzed using a platinum wire as the cathode and a cobalt
plate (suspended from another platinum wire) as the sacri-
ficial anode. The cell was a 100 mL tall-form beaker fitted
with a rubber bung through which the electrochemical
leads entered. Direct current was obtained from a pur-
pose-built d.c. power supply. Applied voltages of 5–15 V
allowed sufficient current flow for smooth dissolution of
the cobalt metal. The current was maintained at 10 mA
during one hour. In all cases, hydrogen was evolved at
the cathode. These cells can be summarized as Co(+)
/
CH3CN + HL + L0/Pt(ꢀ), where L and L0 represent the
corresponding sulfonamide and coligand, respectively. On
completion of the electrolysis the colored solutions were fil-
tered to remove any possible metal particle and then left to
concentrate. This procedure yielded crystalline products.
The solids were washed with acetonitrile and diethyl ether
and dried at room temperature. The solution compositions
and experimental conditions are given in Table 1.
2.3. Physical measurements
The C, N, H and S contents of the compounds (Table 2)
were determined on a Carlo-Erba EA 1108 microanalyser.
IR spectra (Table 2) were recorded as KBr mulls on a
1
Bruker Vector-22 spectrophotometer. The H NMR spec-
tra of the ligands were recorded on a Bruker ARX-
400 MHz spectrometer using CDCl3 as solvent. Solid state
electronic spectra were recorded on a Shimadzu UV 3101
PC. EI mass spectra were recorded on a Micromass instru-
ment (70 eV, 250 ꢁC). LSI mass spectra were recorded on a
VG Autospec-M Micromass instrument using 2-nitroben-
zyl alcohol (2-NBA) as the matrix material.
2.4. Crystal structure determination
The data collections were taken on a SIEMENS Smart
CCD area-detector diffractometer with graphite-mono-
chromated Mo Ka radiation. Absorption corrections were
carried out using SADABS [19]. All of the structures were
solved by direct methods and refined by full-matrix least-
squares based on F2 [20]. All non-hydrogen atoms were
refined with anisotropic displacement parameters. Hydro-
gen atoms were included in idealised positions and refined
with isotropic displacement parameters. Atomic scattering

Table 3
Summary of crystal data and structure refinement
Compound
[Co(Ts3mepy)bipy]
[Co(Ts3mepy)phen]
[Co(Ms3mepy)phen]
[Co(Ts6mepy)2bipy]
[Co(Ts6mepy)2phen]
[Co(Ms6mepy)2phen]
Empirical formula
Formula weight
Temperature (K)
C
737.74
293(2)
36H34CoN6O4S2
C42H40CoN8O4S2
843.86
293(2)
C44H45CoN7O4S2
858.92
293(2)
C36H34CoN6O4S2
737.74
173(2)
C40H37CoN7O4S2
802.82
173(2)
C42H42CoN6O4S2
817.87
293(2)
˚
Wavelength (A)
0.71073
orthorhombic
Pna21
0.71073
orthorhombic
Pcca
0.71073
monoclinic
P21
0.71073
orthorhombic
Pbc21
0.71073
triclinic
0.71073
monoclinic
P21/c
Crystal system
Space group
Unit cell dimensions
ꢀ
P1
˚
a (A)
11.3095(18)
18.324(3)
17.178(3)
16.0317(9)
14.2467(8)
18.3541(10)
14.8657(11)
8.6577(6)
17.2097(13)
22.9894(16)
14.3933(10)
10.4728(7)
90
90
90
3465.4(4)
4
1.414
0.664
1532
0.32 · 0.18 · 0.09
1.67–28.04
ꢀ29 6 h 6 30,
ꢀ17 6 k 6 19,
ꢀ13 6 l 6 12
19945
10.1462(15)
13.535(2)
15.889(2)
110.013(3)
90.021(3)
101.344(3)
2004.8(5)
2
1.330
0.581
834
0.34 · 0.13 · 0.05
1.37–28.07
ꢀ13 6 h 6 13,
ꢀ17 6 k 6 11,
ꢀ17 6 l 6 20
10985
17.4668(11)
11.6772(7)
19.7359(12)
90
103.4120(10)
90
3915.6(4)
4
1.387
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
90
90
109.628(2)
3
˚
Volume (A )
3559.9(10)
4
1.377
0.647
1532
0.25 · 0.18 · 0.08
1.62–28.18
ꢀ14 6 h 6 14,
ꢀ16 6 k 6 24,
ꢀ22 6 l 6 22
18774
4192.1(4)
4
1.337
0.560
2086.2(3)
2
1.367
0.563
Z
Dcalc (Mg/m3)
Absorption coefficient (mmꢀ1
F(000)
)
0.596
1708
1756
898
Crystal size (mm3)
0.42 · 0.36 · 0.32
2.21–28.04
ꢀ20 6 h 6 19,
ꢀ18 6 k 6 13,
ꢀ24 6 l 6 24
22657
0.35 · 0.21 · 0.14
1.45–28.05
ꢀ19 6 h 6 19,
ꢀ11 6 k 6 10,
ꢀ22 6 l 6 19
12882
0.50 · 0.45 · 0.45
2.04–27.99
ꢀ22 6 h 6 15,
ꢀ15 6 k 6 14,
ꢀ25 6 l 6 24
21441
h Range for data collection (ꢁ)
Index ranges
Reflections collected
Independent reflections (Rint
Completeness to h (%)
)
7482 (0.1211)
96.8
4940 (0.0341)
97.0
7955 (0.0481)
94.9
7548 (0.0856)
98.3
7722 (0.0756)
79.3
8699 (0.0462)
92.0
Maximum and minimum transmission
Data/restraints/parameters
Goodness-of-fit on F2
0.950 and 0.682
7482/1/446
0.723
0.836 and 0.617
4940/0/260
1.065
0.924 and 0.751
7955/1/523
0.799
0.942 and 0.707
7548/1/446
0.787
0.971 and 0.797
7722/0/492
0.87 4
0.765 and 0.488
8699/0/504
0.850
Final R indices [I > 2r(I)]
R1 = 0.0526,
wR2 = 0.0704
R1 = 0.1912,
wR2 = 0.0914
R1 = 0.0461,
wR2 = 0.1195
R1 = 0.0836,
wR2 = 0.1287
R1 = 0.0459,
wR2 = 0.0753
R1 = 0.0968,
wR2 = 0.0854
0.024(15)
R1 = 0.0526,
wR2 = 0.0620
R1 = 0.1306,
wR2 = 0.0747
0.096(16)
0.904 and ꢀ0.437
R1 = 0.0766,
wR2 = 0.1907
R1 = 0.2139,
wR2 = 0.2349
R1 = 0.0455,
wR2 = 0.0952
R1 = 0.1016,
wR2 = 0.1075
R indices (all data)
Absolute structure parameter
Largest difference in peak and hole (e A
ꢀ3
˚
)
0.292 and ꢀ0.482
0.402 and ꢀ0.280
0.473 and ꢀ0.264
1.569 and ꢀ0.398
0.399 and ꢀ0.375

I. Beloso et al. / Polyhedron 25 (2006) 2673–2682
2677
factors and anomalous dispersion corrections for all atoms
were taken from International Tables for X-ray Crystallog-
raphy [21]. Details of crystal data and structural refinement
are given in Table 3.
the atomic numbering scheme. Selected bond lengths and
angles are given in Table 4.
[Co(Ts3mepy)2phen] crystallized with two molecules of
acetonitrile, which are not shown in the figure since they
do not interact with the complex molecule to any signifi-
cant degree.
3. Results and discussion
Both complexes consist of discrete molecules with the
six-coordinate cobalt atoms coordinated by a 2,20-bipyri-
dine or 1,10-phenanthroline, which act as N,N0-bidentate
ligands, and two anionic sulfonamide ligands acting as
The analytical results (Table 2) show that the electro-
chemical procedure described above is an effective method
for the synthesis of cobalt complexes with these sulfonamide
ligands and the method represents a simple alternative to
other standard chemical procedures. The compounds are
of the general formula [CoL2L0]. The electrochemical effi-
ciency value (Table 1) is defined as the amount of metal dis-
solved per Faraday of charge and was close to 0.5 mol Fꢀ1
in all cases. This fact, along with the evolution of hydrogen
gas at the cathode, is compatible with a reaction mechanism
involving the anodic oxidation to cobalt(II) and the depro-
tonation of the ligand at the cathode.
Table 4
˚
Selected bond lengths (A) and angles (ꢁ) for [Co(Ts3mepy)2bipy] and
[Co(Ts3mepy)2phen]
[Co(Ts3mepy)2bipy]
[Co(Ts3mepy)2phen]
Co–O(11)
Co–O(21)
Co–N(11)
Co–N(21)
Co–N(31)
Co–N(32)
2.040(5)
2.113(4)
2.189(5)
2.158(5)
2.166(6)
2.136(6)
Co–O(11)
Co–O(11i)
Co–N(11)
Co–N(21)
Co–N(11i)
Co–N(21i)
2.0751(16)
2.0751(16)
2.1483(19)
2.171(2)
2.1483(19)
2.171(2)
Anode: Co ! Co2+ + 2eꢀ
Cathode: 2HL + 2eꢀ ! 2Lꢀ + H2
O(11)–Co–O(21)
O(11)–Co–N(32)
O(21)–Co–N(32)
O(11)–Co–N(21)
O(11)–Co–N(31)
O(21)–Co–N(31)
O(21)–Co–N(21)
O(11)–Co–N(11)
N(32)–Co–N(21)
N(32)–Co–N(11)
N(21)–Co–N(11)
O(21)–Co–N(11)
N(21)–Co–N(31)
N(31)–Co–N(11)
N(32)–Co–N(31)
93.46(19)
169.3(2)
96.7(2)
86.5(2)
94.2(2)
172.0(2)
85.1(2)
85.7(2)
97.6(2)
91.3(2)
169.6(2)
88.4(2)
93.0(2)
94.5(2)
75.8(2)
O(11i)–Co–O(11)
O(11i)–Co–N(21)
O(11)–Co–N(21)
O(11i)–Co–N(11)
O(11i)–Co–N(21i)
O(11)–Co–N(21i)
O(11)–Co–N(11i)
O(11i)–Co–N(11i)
N(12i)–Co–N(21)
N(11)–Co–N(21)
N(11)–Co–N(11i)
O(11)–Co–N(11)
N(11i)–Co–N(21i)
N(12)–Co–N(21i)
N(21)–Co–N(21i)
94.71(10)
170.99(8)
94.29(7)
87.73(7)
94.29(7)
170.99(8)
87.73(7)
86.19(7)
94.42(7)
92.62(7)
171.03(10)
86.19(7)
92.62(7)
94.42(7)
76.71(11)
Overall: Co + 2HL + L0 ! [CoL2L0] + H2
where L0 is 2,20-bipyridine or 1,10-phenanthroline.
The sulfonamide compounds were obtained by air con-
centration of the resulting acetonitrile solution. These com-
pounds are air stable compounds that are soluble in
common organic solvents.
3.1. Description of the structures
3.1.1. Crystal structure of [Co(Ts3mepy)2bipy] and
[Co(Ts3mepy)2phen]
The molecular structures of [Co(Ts3mepy)2bipy] and
[Co(Ts3mepy)2phen] are shown in Fig. 1 together with
Symmetry transformations used to generate equivalent atoms: i: ꢀx, y,
1/2 ꢀ z.
Fig. 1. The molecular structures of [Co(Ts3mepy)2bipy] and [Co(Ts3mepy)2phen].

2678
I. Beloso et al. / Polyhedron 25 (2006) 2673–2682
Npy,O-bidentate systems. The coordination polyhedron
around the metal is best described as an octahedron, with
the oxygen atoms in cis positions and the pyridine nitrogen
atoms in trans positions. Such an arrangement implies a
two-fold axis, which is crystallographic in [Co(Ts3mepy)2-
phen]. In the case of [Co(Ts3mepy)2bipy] the arrangement
is more distorted and, for example, the dihedral angle
between the two pyridine rings in the bipyridine moiety is
9.7(4)ꢁ. In the case of [Co(Ts3mepy)2phen], the phenan-
throline moiety forms a dihedral angle of only 0.94(5)ꢁ with
the equatorial plane, whereas in [Co(Ts3mepy)2bipy] this
angle is 7.6(2)ꢁ. For symmetry reasons, the best equatorial
plane contains the cobalt atom in [Co(Ts3mepy)2phen] and
all in the range expected for hexacoordinated cobalt(II)
complexes. The Co–N bond lengths are very similar to
those found in the octahedrally coordinated complexes
with four pyridine nitrogen donor atoms and two oxygen
atoms in cis positions [23,24]. The average Co–O bond
˚
length is 2.076 A for [Co(Ts3mepy)2(bipy)], which is virtu-
˚
ally the same as the symmetry imposed value of 2.075(2) A
for [Co(Ts3mepy)2(phen)]. These values are very close to
the Co–O bond length found for the cationic aquo complex
[Co(H2O)2(phen)2]2+, 2.077(3) A (average) [23], but are
˚
slightly shorter than that found in the neutral DMF com-
˚
plex [Co(Tspy)2(DMF)2], 2.1635(14) A [11], or in the tri-
˚
flate complex [Co(triflate)2(phen)2], 2.215(4) A [25].
˚
the defining atoms are only 0.005(1) A out of this plane
(RMS, 0.005). However, in [Co(Ts3mepy)2bipy] the best
3.1.2. Description of the structure of [Co(Ms3mepy)2phen]
The molecular structure of [Co(Ms3mepy)2phen] is
shown in Fig. 2 together with the atomic numbering
scheme. Selected bond lengths and angles are given in
Table 5.
˚
plane (RMS, 0.0563) is at 0.008(3) A from the cobalt(II)
˚
atom and the defining atoms are up to 0.061(2) A out of
the plane. The distortion of an octahedron can also be
measured using the values of the dihedral angles a between
bidentate coordination planes (related by a three-fold axis
in a regular octahedron). The average values for the angle a
are 84.9(2)ꢁ and 86.92(7)ꢁ in [Co(Ts3mepy)2bipy] and
[Co(Ts3mepy)2phen], respectively, and these are not very
far from 90ꢁ [22].
The pyridine ring plane and the benzene ring plane of
the sulfonamide ligand form dihedral angles of 75.6(1)ꢁ
for [Co(Ts3mepy)2phen] and 51.4(3)ꢁ and 75.9(2)ꢁ for
[Co(Ts3mepy)2bipy]. These angles again highlight the dif-
ferences found in the latter complex but are not signifi-
cantly different from those found in the free ligand [10].
The Co–N bond distances, which range from 2.136(6) to
[Co(Ms3mepy)2phen] crystallized with an acetonitrile
solvent molecule, which is not shown in the figure since it
does not interact significantly with the complex molecule.
The structure of [Co(Ms3mepy)2phen] is similar to those
described above, with the sulfonamide ligands acting as
Npy,O-bidentate donors and the neutral ligand as an N,N
bidentate system. However, the dispositions of the ligands
are different, as in this case the oxygen atoms are in an axial
disposition and the pyridine nitrogen atoms of the sulfon-
amide ligands are in a cis disposition. This arrangement
allows a p,p-stacking interaction between one of the mesit-
ylene rings and the phenanthroline moiety, with a dihedral
˚
˚
˚
2.189(5) A, and the Co–O distances, 2.040(5)–2.113(4) A,
also show the greater level of distortion in [Co(Ts3mepy)2-
bipy] than [Co(Ts3mepy)2phen]. These values are, however,
angle of 1.4(1)ꢁ and distances between rings of about 3.6 A.
The pyridine ring plane and the benzene ring plane of
this sulfonamide ligand form dihedral angles of 89.3(1)ꢁ
Fig. 2. The molecular structure of [Co(Ms3mepy)2phen].

I. Beloso et al. / Polyhedron 25 (2006) 2673–2682
2679
˚
Table 5
Selected bond lengths (A) and angles (ꢁ) for [Co(Ms3mepy)2phen]
2.084(3) and 2.114(3) A, are slightly longer than those
found in the previously described complexes, but are still
shorter than those described in the literature [25].
˚
Co–O(11)
Co–N(21)
Co–N(32)
2.084(3)
2.133(4)
2.154(4)
Co–O(21)
Co–N(31)
Co–N(11)
2.114(3)
2.149(3)
2.157(4)
3.1.3. Description of the structures of [Co(Ts6mepy)2bipy],
[Co(Ts6mepy)2phen] and [Co(Ms6mepy)2phen]
O(11)–Co–O(21)
O(21)–Co–N(21)
O(11)–Co–N(31)
N(21)–Co–N(31)
O(11)–Co–N(32)
O(11)–Co–N(11)
N(32)–Co–N(11)
N(31)–Co–N(32)
172.46(12)
83.13(13)
80.33(12)
97.30(14)
99.82(13)
85.98(13)
92.01(14)
77.00(14)
O(11)–Co–N(21)
N(21)–Co–N(11)
O(21)–Co–N(31)
N(21)–Co–N(32)
O(21)–Co–N(32)
O(21)–Co–N(11)
N(31)–Co–N(11)
89.62(13)
96.27(13)
98.49(12)
167.87(14)
87.10(12)
96.83(13)
160.60(14)
The molecular structures of these compounds are
shown in Figs. 3–5, respectively, together with the atomic
numbering schemes. Selected bond lengths and angles for
the molecules are given in Tables 6 and 7. Once more,
[Co(Ts6mepy)2phen] crystallized with an acetonitrile sol-
vent molecule, which is not shown in the figure since it
does not interact with the complex molecule to any signif-
icant degree.
The coordination behavior of the anionic ligands in
these complexes is quite different from the previous exam-
ples described in this paper. In these cases, the sulfonamide
anionic ligands are Npy,Namide-bidentate ligands. A neutral
2,20-bipyridine or 1,10-phenanthroline, both of which act
as N,N-donors, completes the coordination sphere of the
metal. Consequently, the coordination polyhedron around
the cobalt(II) is best described as a highly distorted octahe-
dron [CoN6]. However, some differences can be found
between the structures in terms of the disposition of the
ligands around the metal. In all cases, the pyridine nitrogen
atoms are in cis positions and in the same equatorial plane
as the bipyridine moiety. The small chelate angles of the
sulfonamide ligands are the main source of distortion, with
angles ranging from 62.04(7)ꢁ to 62.9(3)ꢁ. The axial angles
(theoretical value of 180ꢁ) range from 156.72(14)ꢁ to
165.62(14)ꢁ.
Some staking interactions
N(32)–C(17)
C(18)–C(310)
3.456(5)
3.491(7)
3.640(7)
C(19)–C(38)
C(110)–C(37)
C(112)–C(36)
3.579(8)
3.562(7)
3.574(6)
C(111)–C(37)
and these are larger than those found in the free ligand [14]
or in the other ligand [74.8(1)ꢁ in the complex]. A p,p-stacking
interaction has already been found in similar complexes of
copper, zinc and cadmium, but only when the ligand con-
tains a mesitylene ring. This is probably due to the elec-
tron-donating effect of the three methyl groups in the ring
as well as the increase in the overall size of the group.
The average value for the angle a (vide supra) is
81.61(12)ꢁ, which deviates significantly from regularity
towards a trigonal prism. In addition, the best equatorial
plane defined by the four nitrogen donor atoms has an
RMS deviation of 0.231, with the N32 atom up to
˚
0.255(2) A out of the plane. The cobalt atom is, however,
˚
only 0.047(2) A out of this plane.
In [Co(Ts6mepy)2bipy] the average value for the angle a
(vide supra) is 85.5(1)ꢁ and this is close to the theoretical 90ꢁ.
Another measurement of the distortion of the octahedron is
The Co–N bond distances, which are in the range
˚
2.133(4)–2.157(4) A, are very similar to those found in
the previously described complexes. The Co–O distances,
Fig. 3. Molecular structure of [Co(Ts6mepy)2bipy].

2680
I. Beloso et al. / Polyhedron 25 (2006) 2673–2682
Fig. 4. Molecular structure of [Co(Ts6mepy)2phen].
Fig. 5. Molecular structure of [Co(Ms6mepy)2phen].
the angle /, defined as the twist angle between the two trian-
gles of nitrogen atoms perpendicular to a trigonal axis
(Scheme 4). Unfortunately, in this compound these triangu-
lar planes are not parallel and they form dihedral angles of
20.2(2)ꢁ, 18.1(2)ꢁ and 15.5(2)ꢁ. If we consider the latter two
triangles, we have N31, N21 and N12 and N32, N22 and
N11 – i.e., one sulfonamide nitrogen atom, one pyridine
nitrogen atom from a different ligand and a bipyridine nitro-
gen atom – and the values for the angle / are ꢀ39.3(2)ꢁ,
ꢀ39.5(2)ꢁ and ꢀ45.2(2)ꢁ.
The planarity of the equatorial plane can also be a crite-
rion to assess the distortion of the octahedron. The best
calculated plane formed by the pyridine nitrogen atoms
and the nitrogen atoms of the bypiridine moiety shows
an RMS deviation of 0.3898, and the atom N32 is up to
˚
0.431(2) A out of the plane. The cobalt(II) atom is
˚
0.014(2) A out of the plane.
In the case of [Co(Ts6mepy)2phen], the arrangement of
the ligands around the metal gives rise to an a angle with
an average value of 82.4(3)ꢁ, which shows greater distortion

I. Beloso et al. / Polyhedron 25 (2006) 2673–2682
2681
Table 6
The coordination polyhedron around the cobalt(II) in
[Co(Ms6mepy)2phen] is, once again, best described as an
octahedron, with dihedral a angles between bidentate coor-
dination planes (related by three-fold axis in a regular octa-
hedron) of 88.90(8)ꢁ, 84.49(6)ꢁ and 85.52(7)ꢁ, average
86.30(8)ꢁ, which is close to the theoretical 90ꢁ [22]. The
angles /, defined as above, have values of 38.94(8)ꢁ,
41.45(8)ꢁ and 39.07(9)ꢁ. The planarity of the equatorial
plane is better than in the last two complexes, with an
RMS deviation of 0.2981, and the N31 atom is
˚
Selected bond lengths (A) and angles (ꢁ) for [Co(Ts6mepy)2bipy] and
[Co(Ts6mepy)2phen]
[Co(Ts6mepy)2bipy]
[Co(Ts6mepy)2phen]
Co–N(11)
Co–N(12)
Co–N(21)
Co–N(22)
Co–N(31)
Co–N(32)
2.216(4)
2.131(4)
2.122(3)
2.163(4)
2.088(4)
2.117(3)
2.194(7)
2.121(7)
2.137(6)
2.149(7)
2.120(6)
2.101(7)
N(31)–Co–N(32)
N(31)–Co–N(21)
N(32)–Co–N(21)
N(31)–Co–N(12)
N(32)–Co–N(12)
N(21)–Co–N(12)
N(31)–Co–N(22)
N(32)–Co–N(22)
N(21)–Co–N(22)
N(12)–Co–N(22)
N(31)–Co–N(11)
N(32)–Co–N(11)
N(21)–Co–N(11)
N(12)–Co–N(11)
N(22)–Co–N(11)
78.28(14)
103.98(13)
158.10(14)
96.41(13)
97.24(14)
104.06(14)
91.11(14)
96.28(13)
62.09(13)
165.62(14)
156.72(14)
94.90(13)
90.67(13)
62.06(14)
111.86(15)
78.3(3)
158.2(3)
101.6(3)
97.7(2)
97.4(2)
104.1(3)
96.4(2)
99.0(3)
62.9(3)
157.0(2)
92.2(2)
159.9(3)
97.7(2)
61.9(3)
99.6(3)
˚
0.327(1) A out of the plane. The cobalt(II) atom is only
˚
0.004(1) A out of the plane.
Once again, significant intermolecular ‘‘p–p stacking’’
stabilization is produced between the 1,10-phenanthroline
unit and the benzene rings of both sulfonamide ligands.
This interaction does not appear to occur in an intermolec-
ular manner. The dihedral angles between the rings
involved in these interactions are 0.74(12)ꢁ and 3.77(13)ꢁ
and several short distances are shown in Table 7. It is
worth noting the difference found between this compound
and the complex [Cu(Ms6mepy)2phen]; in the copper com-
pound the distances in the axis N12–Cu–N22 are longer
than those in the equatorial plane and the angle is nearer
to 180ꢁ [average 171.2(2)ꢁ]. In the cobalt compound, the
distances in the axis N12–Co–N22 are similar to those in
the equatorial plane and the angle shows more distortion,
157.61(8)ꢁ.
Table 7
˚
Selected bond lengths (A) and angles (ꢁ) for [Co(Ms6mepy)2phen]
Co–N(11)
Co–N(12)
Co–N(21)
2.1514(18)
2.1905(18)
2.192(2)
Co–N(22)
Co–N(31)
Co–N(32)
2.124(2)
2.117(2)
2.1236(19)
Dihedral angles between the pyridine ring and the mes-
ytilene ring for each ligand are 77.48(8)ꢁ and 81.69(8)ꢁ, val-
ues similar to those found in the free ligand.
N(31)–Co–N(32)
N(31)–Co–N(22)
N(32)–Co–N(22)
N(31)–Co–N(12)
N(32)–Co–N(12)
N(31)–Co–N(21)
N(32)–Co–N(21)
N(12)–Co–N(21)
78.05(8)
101.75(8)
96.93(8)
95.22(7)
100.82(7)
163.51(7)
99.24(8)
101.26(8)
N(31)–Co–N(11)
N(32)–Co–N(11)
N(22)–Co–N(11)
N(22)–Co–N(12)
N(11)–Co–N(12)
N(22)–Co–N(21)
N(11)–Co–N(21)
95.75(7)
161.49(7)
101.43(8)
157.61(8)
62.04(7)
62.19(8)
91.47(8)
˚
˚
The average Co–Npy [2.169(7) A], Co–Namide [2.146(7) A]
˚
and Co–Nphen or Co–Nbipy [2.111(7) A] bond lengths are
similar in all of the complexes and are very close to those
found in other octahedral cobalt(II) complexes with pyridine
˚
and amide nitrogen donor ligands; for example, 2.150 (9) A
is the average value for CoL2 (HL = 1-[(4-methylphenyl)-
sulfonamido]-2-[(2-pyridylmethyleneamino)benzene]) [26].
Some staking interactions
C(19)–C(37)
C(211)–C(38)
C(28)–C(35)
C(211)–C(37)
3.576(4)
C(211)–C(36)
C(110)–C(37)
C(111)–C(34)
C(112)–C(35)
3.796(4)
3.586(4)
3.647(3)
3.479(3)
3.699(5)
3.609(3)
3.673(4)
3.2. Spectroscopic studies
The IR spectra of these complexes (Table 2) do not con-
tain the band observed in the ligand at 3248–3222 cmꢀ1
,
which is attributed to m(N–H) stretching. This observation
indicates that the ligand is in the anionic amidate form in
the complex. The spectra also show bands in the aromatic
region due to m(C@N) (1615–1590 cmꢀ1) and m(C@C)
(1459–1413 cmꢀ1). These bands appear in similar positions
to those for the free ligand in the complexes with
Ts3Mepyꢀ and Ms3Mepyꢀ but are shifted to lower fre-
quencies in the Ts6Mepyꢀ and Ms6mepyꢀ complexes as
result of coordination through the sulfonamide nitrogen
atom. The spectra also show bands in the region 1342–
1319 cmꢀ1, which are attributed to mas(S@O), and bands
in the range 1178–1081 cmꢀ1, which are attributed to the
φ
Scheme 4.
than the former complex, and values for the / angle of
ꢀ35.4(3)ꢁ, ꢀ38.2(3)ꢁ and ꢀ36.2(3)ꢁ. The increase in the dis-
tortion is probably due to packing reasons and also to a
twist in the N22–S2 bond. However, when the planarity
of the equatorial plane is considered, the RMS deviation
m
sym(S@O) vibrations. A band is also observed at 2938–
2918 cmꢀ1 and this corresponds to m(CH3). In addition,
˚
is 0.3324 and the N31 atom is 0.372(4) A out of the plane.
The cobalt(II) atom is 0.045(4) A out of the plane.
˚
the IR spectra show absorptions typical of coordinated

2682
I. Beloso et al. / Polyhedron 25 (2006) 2673–2682
2,20-bipyridine (769–766 and 736–734 cmꢀ1) [27] and 1,10-
[4] L.M. Engelhardt, M.G. Gardiner, C. Jones, P.C. Junk, C.L. Raston,
A.H. White, J. Chem. Soc., Dalton Trans. (1996) 3053.
[5] C.L. Raston, B.W. Skelton, V.A. Tolhurst, A.H. White, Polyhedron
17 (1998) 935.
[6] A. Spannenberg, P. Arndt, R. Kempe, Angew. Chem., Int. Ed. 37
(1998) 832.
[7] A. Spannenberg, H. Fuhrmann, P. Arndt, W. Baumann, R. Kempe,
Angew. Chem., Int. Ed. 37 (1998) 3363, and references therein.
[8] C.A. Otter, S.M. Couchman, J.C. Jeffery, K.L.V. Mann, E. Psillakis,
M.D. Ward, Inorg. Chim. Acta 278 (1998) 178.
phenanthroline (1519–1517, 853–844 and 728–726 cmꢀ1
[27,28].
)
The solid state electronic spectra between 20000 and 5000
cmꢀ1 of all the heteroleptic complexes [Co(Me3mepy)2L0]
contain three bands in the regions 8700–9500 and 18900-
4
21000 cmꢀ1, assigned to 4T1g(F) ! T2g(m1) and 3T1g(F) !
4T2g(m3) transitions, respectively, in a distorted octahedral
4
4
field. A band assignable to T1g(F) ! A2g(m2) [except for
the [Co(Me3mepy)2bipy] (14500 cmꢀ1)] was not observed,
probably because such a band must be very weak and
obscured by the m3 transition [29].
´
´
[9] S. Cabaleiro, J. Castro, J.A. Garcıa-Vazquez, J. Romero, A. Sousa,
Acta Crystallogr., Sect. C 56 (2000) 293.
´
´
´
[10] I. Beloso, J. Castro, J.A. Garcıa-Vazquez, P. Perez-Lourido, J.
Romero, A. Sousa, Polyhedron 22 (2003) 1099.
´
´
[11] S. Cabaleiro, J. Castro, J.A. Garcıa-Vazquez, J. Romero, A. Sousa,
Polyhedron 19 (2000) 1607.
[12] S. Cabaleiro, J. Castro, E. Vazquez-Lopez, J.A. Garcıa-Vazquez, J.
Acknowledgements
´
´
´
´
Romero, A. Sousa, Polyhedron 18 (1999) 1669.
[13] I. Beloso, J. Castro, J.A. Garc´ıa-Va´zquez, P. Pe´rez-Lourido, J.
Romero, A. Sousa, Z. Anorg. Allg. Chem. 629 (2003) 275.
This work was supported by the Xunta de Galicia
(Spain) (Grant PGIDT00PXI20305PR) and by the Minis-
´
´
´
´
[14] I. Beloso, J. Borras, J. Castro, J.A. Garcıa-Vazquez, P. Perez-
Lourido, J. Romero, A. Sousa, Eur. J. Inorg. Chem. (2004)
635.
´
terio de Ciencia y Tecnologıa (Spain) (Grant BQU2002-
01819) and the Universidade de Vigo, under the Grant
C221 122F 64102. We thank fergus.uvigo.es (http://fergus.
uvigo.es/) for X-ray solution and refinement facilities.
[15] C.-F. Lee, S.-M. Peng, J. Chin. Chem. Soc. (Taipei) 38 (1991) 559.
[16] H.-Y. Cheng, P.-H. Cheng, C.-F. Lee, S.-M. Peng, Inorg. Chim. Acta
181 (1991) 145.
´
´
´
´
[17] S. Cabaleiro, J. Castro, E. Vazquez-Lopez, J.A. Garcıa-Vazquez, J.
Romero, A. Sousa, Inorg. Chim. Acta 294 (1999) 87.
[18] D.G Tuck, Pure Appl. Chem. 51 (1979) 2005.
[19] G.M. Sheldrick, SADABS: An Empirical Absorption Correction Pro-
gram for Area Detector Data, University of Go¨ttingen, Go¨ttingen,
Germany, 1996.
Appendix A. Supplementary material
The atomic positions, full list of bond lengths and angles
and other crystallographic data are available on request to
J.C. Crystallographic data have been deposited in the Cam-
bridge Crystallographic Data Centre, and can be obtained
free of charge at www.ccdc.cam.ac.uk/conts/retriev-
ing.html [or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; Fax:
(intrnat.) +44 1223 336 033; e-mail: deposit@ccdc.cam.a-
c.uk] quoting the deposition numbers CCDC 295055–
295060. Supplementary data associated with this article
can be found, in the online version, at doi:10.1016/j.poly.
2006.03.004.
[20] G.M. Sheldrick, SHELX-97: Program for the Solution and Refinement
of Crystal Structures, University of Go¨ttingen, Go¨ttingen, Germany,
1997.
[21] International Tables for X-ray Crystallography, vol. C, Kluwer,
Dordrecht, 1992.
[22] P.B. Donaldson, P.A. Tasker, N.W. Alcock, J. Chem. Soc., Dalton
Trans. (1977) 1160.
[23] R. Carballo, B. Covelo, E.M. Vazquez-Lopez, E. Garcıa-Martınez, Z.
´
´
´
´
Anorg. Allg. Chem. 629 (2003) 244.
[24] A. Moghimi, R. Alizadeh, A. Shokrollahi, H. Aghabozorg, M.
Shamsipur, A. Shockravi, Inorg. Chem. 42 (2003) 1616.
[25] M.-T. Youinou, R. Ziessel, J.-M. Lehn, Inorg. Chem. 30 (1991)
2144.
References
[26] A. Sousa, M.R. Bermejo, M. Fondo, A. Garcia-Deibe, A. Sousa-
Pedrares, O. Piro, New J. Chem. 25 (2001) 647.
[27] A.A. Schilt, R.C. Taylor, J. Inorg. Nucl. Chem. 9 (1959) 211.
[28] R.G. Inskeep, J. Inorg. Nucl. Chem. 24 (1963) 763.
[29] A.B.P. Lever, Inorganic Electronic Spectroscopy, 2nd ed., Elsevier,
Amsterdam, 1984.
[1] R. Kempe, Eur. J. Inorg. Chem. (2003) 191, and references therein.
[2] M. Polamo, M. Leskel, J. Chem. Soc., Dalton Trans. (1996) 4345.
[3] R. Clerac, F.A. Cotton, K.R. Dunbar, C.A. Murillo, I. Pascual, X.
Wang, Inorg. Chem. 38 (1999) 2655.