Reactivity studies of aryl cobaloximes with molecular oxygen and electrophiles

Article abstract of DOI:10.1016/j.jorganchem.2010.12.008

The reactivity of aryl cobaloximes, ArCo(dmgH)₂Py [Ar = Phenyl, 1-naphthyl, 2-naphthyl, 4-NMe₂C₆H₄, 2-thienyl] with molecular oxygen and electrophiles (Br₂ and 2,4- dinitrobenzenesulfenyl chloride) has been investigated. All these complexes do not show any affinity toward molecular oxygen and the reaction with electrophiles either leads to ring substitution and/or the Co-C bond cleavage. The molecular structures of two new aryl cobaloximes and two ring substituted organometallic products have been determined crystallographically. The C-H?O intermolecular hydrogen bonding interactions in the crystal packing lead to different superstructural motifs.

Full text of DOI:10.1016/j.jorganchem.2010.12.008

Journal of Organometallic Chemistry 696 (2011) 2280e2286
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Reactivity studies of aryl cobaloximes with molecular oxygen and electrophiles
*
Kamlesh Kumar, B.D. Gupta
Department of Chemistry, Indian Institute of Technology, Kanpur 208 016, India
a r t i c l e i n f o
a b s t r a c t
Article history:
The reactivity of aryl cobaloximes, ArCo(dmgH)2Py [Ar ¼ Phenyl, 1-naphthyl, 2-naphthyl, 4-NMe2C6H4,
2-thienyl] with molecular oxygen and electrophiles (Br2 and 2,4-dinitrobenzenesulfenyl chloride) has
been investigated. All these complexes do not show any affinity toward molecular oxygen and
the reaction with electrophiles either leads to ring substitution and/or the CoeC bond cleavage. The
molecular structures of two new aryl cobaloximes and two ring substituted organometallic products
have been determined crystallographically. The CeH/O intermolecular hydrogen bonding interactions
in the crystal packing lead to different superstructural motifs.
Received 4 November 2010
Received in revised form
30 November 2010
Accepted 6 December 2010
Keywords:
Aryl cobaloximes
Reactivity
Ó 2010 Elsevier B.V. All rights reserved.
Electrophiles
Structure elucidation
1. Introduction
The aim of the present work, therefore, is to study the reac-
tivity of aryl cobaloximes (a) with molecular oxygen under visible
In recent years, the description, spectroscopic data, structuree
property relationship and their correlation to the CoeC bonds in
organocobaloximes have been most emphasized [1e9]. In an on-
going effort to understand the CoeC stability/reactivity we have
published a number of organocobaloximes with different dioximes
like gH, dmgH, chgH, dpgH, dmestgH, dSPhgH [1e4,10e13]. The
study has shown that the cis influence (effect of dioxime on
the CoeC bond) plays an important role. We have recently studied
the effect of dioxime and the aryl ring size on the CoeC bond in aryl
cobaloximes by spectral and structural studies [14].
The inherently weak CoeC bond in the alkyl/benzyl cobaloximes
undergoes homolytic cleavage with visible light, similar to the
activation of vitamin B12 by apoenzyme [15e18] and the insertion
of molecular oxygen into the CoeC bond has extensively been used
to test the reactivity of these compounds [19e26]. The benzyl- and
(heteroaromatic methyl) cobaloximes have also been shown to be
susceptible toward electrophiles and undergo either CoeC bond
cleavage and/or ring substitution [27e36], but no such studies have
been done on the aryl cobaloximes.
light (b) with Br2 and 2,4-dinitrobenzenesulfenyl chloride under
electrophilic conditions and (c) to study the crystal packing in
these complexes to look for supramolecular structures.
2. Result and discussion
2.1. Synthesesand characterization of ArCo(dmgH)2Py (1e5, Chart 1)
Synthesis and characterization of aryl cobaloximes 1e3 have
been reported recently from our laboratory and two new complexes
4 and 5 have been synthesized and purified by the published
procedure for 1e3 [14]. The complexes 4 and 5 are air-stable, yellow
crystalline solids, soluble in CH2Cl2, CHCl3 and sparingly soluble in
Ar
H
CH3
H3C
O
N
O
N
Co
N
O
N
O
Despite the large number of crystal structures of cobaloximes
and their related compounds, very little information is known on
the weak interactions in the crystal packing [5,6,9,13,37].
H
H3C
CH3
N
Ar = Phenyl, 1-naphthyl, 2-naphthyl, 4-NMe2C6H4, 2-thienyl (1-5)
* Corresponding author. Present address: Bahra University, Shimla Hills, Solan,
India. Tel.: þ91 512 2597046; fax: þ91 512 2597436.
E-mail address: bdg@iitk.ac.in (B.D. Gupta).
Chart 1. Aryl cobaloximes [ArCo(dmgH)2Py].
0022-328X/$ e see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2010.12.008

K. Kumar, B.D. Gupta / Journal of Organometallic Chemistry 696 (2011) 2280e2286
2281
Table 1
Crystal data and structure refinement details for compounds 4, 5, 12 and 13.
Parameters
4
5
12
13
Empirical formula
Formula weight
Diffractometer
Temp (K)
C21H29CoN6O4
488.43
Bruker Apex CCD
100(2)
C18H26Cl2CoN5O4S
538.33
Bruker Apex CCD
100(2)
C31H45CoN8O11
796.74
Bruker Apex CCD
100(2)
S
C23H24CoN7O8S2
649.54
Bruker Apex CCD
100(2)
Crystal system
Space group
Unit cell dimension
a (Å)
b (Å)
c (Å)
Triclinic
Pꢀ1
Monoclinic
C2/c
Monoclinic
P21/c
Triclinic
Pꢀ1
9.752(3)
11.928(2)
13.229(3)
14.869(3)
90.000
107.31(3)
90.000
2240.0(8)
4
1.596
8.108(5)
9.191(5)
14.216(4)
16.738(5)
88.161(5)
88.796(5)
72.323(5)
2209.6(10)
4
30.005(5)
14.826(5)
90.000(5)
91.764(5)
90.000(5)
3605(3)
12.650(5)
13.385(5)
69.863(5)
82.251(5)
78.345(5)
1427.4(11)
2
a
b
g
(ꢁ)
(ꢁ)
(ꢁ)
V (Å3)
Z
r
4
(calc), g/cm3
(Mo-K
) (mmꢀ1
1.468
0.818
1.468
0.604
1.507
0.806
m
a
)
1.134
F (000)
1024
1112
1672
664
Crystal size (mm3)
Index ranges
0.26 ꢂ 0.20 ꢂ 0.18
ꢀ11 ꢃ h ꢃ 10
ꢀ15 ꢃ k ꢃ 17
ꢀ20 ꢃ l ꢃ 20
11,904
0.43 ꢂ 0.32 ꢂ 0.23
ꢀ15 ꢃ h ꢃ 10
ꢀ16 ꢃ k ꢃ 17
ꢀ19 ꢃ l ꢃ 19
7040
0.30 ꢂ 0.26 ꢂ 0.22
ꢀ9 ꢃ h ꢃ 8
ꢀ35 ꢃ k ꢃ 35
ꢀ15 ꢃ l ꢃ 17
18,262
0.27 ꢂ 0.23 ꢂ 0.21
ꢀ12 ꢃ h ꢃ 12
ꢀ21 ꢃ k ꢃ 13
ꢀ19 ꢃ l ꢃ 20
9263
No. of rflns collected
No. of indep rflns
GOOF on F2
8061
1.054
2725
1.095
6300
1.053
6662
1.148
Final R indices (I > 2
s
(I))
R1 ¼ 0.0495
wR2 ¼ 0.1249
R1 ¼ 0.0619
wR2 ¼ 0.1387
8061/0/587
R1 ¼ 0.0618
wR2 ¼ 0.1566
R1 ¼ 0.0796
wR2 ¼ 0.1937
2725/1/156
R1 ¼ 0.0695
wR2 ¼ 0.1773
R1 ¼ 0.0867
wR2 ¼ 0.1917
6300/0/477
R1 ¼ 0.0593
wR2 ¼ 0.1430
R1 ¼ 0.0831
wR2 ¼ 0.1943
6662/0/379
R indices (all data)
Data/restraints/param
acetone, CH3OH and CH3CN. The new aryl cobaloximes (4 and 5)
have been characterized by elemental analyses, NMR and also by
X-ray crystallography.
The deviations of the cobalt atoms from mean equatorial 4N plane
and the butterfly
are ꢀ0.0191(5), ꢀ0.0076(5), ꢀ0.0044(4)
Å
bending angles are ꢀ9.04, ꢀ4.37, ꢀ3.10ꢁ in 4-A, 4-B and 5 respec-
tively. The deviation is toward the axial aryl group and the bending
of dioxime units is toward base, pyridine. The CoeC bond distances
are 1.966(2), 1.972(2),1.952(4) Å and the CoeNPy bond distances are
2.062(2), 2.058(2), 2.034(2) Å in 4-A, 4-B and 5.
2.2. Molecular structures of 4 and 5
The pertinent crystal data and refinement parameters for 4 and
5 are given in Table 1 and the selected bond lengths, bond angles
and structural parameters are given in Table 2. The molecular
structures with selected numbering schemes are shown in Figs. 1
and 2. The geometry around the central cobalt atom is distorted
octahedral with four nitrogen atoms of the dioxime in the equa-
torial plane and pyridine and 4-N,N-dimethylaminophenyl
(4-NMe2C6H4) or 2-thienyl are axially coordinated. The crystal
structure of 4 contains two molecules in its asymmetric unit and
since there is a structure variation, they are numbered as 4-A and
4-B and the crystal data is given separately in Table 2.
There are some significant differences in structural parameters
of 4-A and 4-B and it is believed that these differences arise due to
the crystal packing. The packing diagrams of 4-A and 4-B show the
presence of intermolecular CeH/O hydrogen bonding leading to
the formation of a tetramer structural motif (Figure S1). There are
two types of CeH/O hydrogen bonds (C20AeH20F/O2 ¼ 2.686
(2) and C8A-H8A1/O3 ¼ 2.382(2) Å) between 4-A and 4-B.
2.3. Reaction of 1e5 with O2, Br2 and 2,4-dinitrobenzenesulfenyl
chloride
The Co(dmgH)2 unit in organocobaloximes undergoes geomet-
rical deformations, due to flexibility, which is roughly represented
by the displacement of cobalt out of 4-nitrogen plane (d) [38] and
In spite of the fact that the CoeC bond length in aryl cobaloximes
is similar to the alkyl and benzyl cobaloximes, these complexes
do not show any affinity toward molecular oxygen even under
by the butterfly bending angle between two dioxime units (a) [38].
Table 2
Selected bond lengths, bond angles and other relevant structural parameters.
Parameters
4
5
12
13
4-A
4-B
CoeC (Å)
1.966(2)
2.062(2)
1.972(2)
2.058(2)
1.952(4)
2.034(2)
180.00
1.960(4)
2.050(3)
1.940(4)
2.029(4)
CoeNpy (Å)
CeCoeNpy (ꢁ)
179.46(11)
ꢀ9.04
178.41(11)
ꢀ4.37
179.29(15)
þ2.95
178.20(16)
ꢀ4.24
a
s
(ꢁ)
(ꢁ)
ꢀ3.10
81.61(22)
ꢀ0.0191(5)
2.458(3) 2.487(3)
86.80(25)
ꢀ0.0076(5)
2.468(2) 2.481(2)
81.08(7)
ꢀ0.0044(4)
2.496(3)
86.72(13)
þ0.0135(6)
2.588(4) 2.459(4)
86.41(85)
ꢀ0.0105(7)
2.495(3) 2.487(3)
d (Å)
O/O (Å)

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K. Kumar, B.D. Gupta / Journal of Organometallic Chemistry 696 (2011) 2280e2286
exclusive organic products formed in the reaction and the bro-
mocobaloxime, BrCo(dmgH)2Py is the inorganic product. These
products are formed due to the cleavage of the CoeC bond. On the
other hand, 2-thienylcobaloxime (5) on reaction with Br2 under
identical conditions gives the 5-bromo-substituted organome-
tallic compound (10).
Unlike the above, the reaction of 4 with 2,4-dinitrobenzene-
sulfenyl chloride (RSCl) gives both the organic (11) [39] and the ring
substituted organometallic products (12) in a 43:57 molar ratio1.
Similarly, the complex 5 exclusively forms 5-substituted organo-
metallic compound (13). The latter does not react further with more
RSCl butit forms 14 on reactionwithBr2 [40]. Thecomplexes 1e3 and
10 do not react with RSCl under similar conditions. However,
complex 10 affordedunidentifiable mixture ofproducts with Br2. The
reaction results are shown in Table 3.
Blank reaction: The reaction of 2-bromothiophene with RSCl
does not form 14 under identical conditions.
The formation of ring substituted products (10, 12 and 13) is
a very significant result as it affords a useful synthetic procedure
where an organocobaloxime can be used as a precursor for the
formation of a new and modified organocobaloxime. Furthermore,
we have also been able to substitute two dis-similar groups on the
same thiophene ring which is difficult to obtain from the conven-
tional organic transformation on thiophene.
Fig. 1. Molecular structure of 4. All hydrogen atoms have been omitted for clarity
(hydrogen atoms involved in the intramolecular hydrogen-bonding interactions are
shown).
2.4. Molecular structures of 12 and 13
Molecular structures of the complexes 12 and 13 have been
determined crystallographically. Details about data collection,
refinement, and structure solution are summarized in Table 1 and
selected geometrical parameters are given in Table 2. Molecular
structures are shown in Figs. 3 and 4. The deviations of the central
cobalt atom (d) from the mean equatorial 4N plane are þ0.0135(6)
and ꢀ0.0105(7) Å respectively for 12 and 13. The butterfly bending
angle in 12 is þ2.95ꢁ while it is ꢀ4.24ꢁ in 13. The bending of
dioxime units in the former is opposite while in the latter it is
similar to their corresponding precursors 4 and 5, respectively. All
other structural parameters in these derivatives do not change
much from their corresponding precursors.
irradiation for 5 h in CH2Cl2 and with the result these are very stable
in solution. It seems that the ability of h1 aryls to have both
s
donation as well as
p-back bonding through the filled aryl
p-orbitals
and empty
complexes.
p
* antibonding orbitals provides stability to these
The reaction with the electrophiles, however, is more encour-
aging but its reactivity varies drastically with the nature of the
electrophile as well as on the aryl ring. The complexes 1e4 react
with Br2 in CHCl3 under nitrogen atmosphere. The reactions are
done with very low concentration of Br2 to avoid the higher order
reactions in Br2. The corresponding bromoarenes (6e9) are the
These substituted derivatives also show some interesting prop-
erties in crystal packing and form different superstructural motifs
through intermolecular CeH/O hydrogen bonding. The metric
parameters for theseweakinteractions are given inTable 4. Complex
12 self-assembles via CeH/O interactions resulting two-dimen-
sional supermolecular helices. A left-handed helix is formed along
the two-fold screw axis through C10eH10A/O8 [2.511(4) Å] and
C11eH11A/O7 [2.548(4) Å] bonds (Fig. 5A and B). Furthermore, this
helical structure is connected to another helix and forms a two-
dimensional network through three CeH/O interactions
[C4eH4B/O1
C20eH20B/O8 ¼ 3.118(4) Å] (Figure S2).
¼
3.079(3), C5eH5B/O3
¼
3.047(3) and
The crystal-packing diagram of compound 13 shows a dimer
structural motif involving two CeH/O hydrogen bond interactions
[C9eH9/O8 ¼ 2.562(4) Å] shown in Figure S3. Another interesting
aspect of crystal packing of 13 is that it shows a two-dimensional
lamellar network involving four CeH/O type intermolecular
contacts. A one-dimensional double-chain polymeric network is
formed due to two CeH/O hydrogen bonds [C8eH8B/O8 ¼ 2.702
(4) and C10eH10/O6 ¼ 2.561(3) Å]. Two such 1-D double chains
are connected through two more weak CeH/O hydrogen bonds
[C1eH1B/O2 ¼ 2.965(3) and C4eH4C/O2 ¼ 3.620(2) Å] to form
a 2-D lamellar network (Figure S4).
Fig. 2. Molecular structure of 5. All hydrogen atoms and solvent molecule have been
omitted for clarity (hydrogen atoms involved in the intramolecular hydrogen-bonding
interactions are shown).
1
Product ratio based on isolated yield (isolation 90%).

K. Kumar, B.D. Gupta / Journal of Organometallic Chemistry 696 (2011) 2280e2286
2283
Table 3
Products of the reactions of O2, Br2 and 2,4-dinitrobenzenesulfenyl chloride with ArCo(dmgH)2Py.
3. Conclusion
4. Experimental section
4.1. Syntheses of aryl cobaloximes (1e5)
In summary, we have studied the reactivity of aryl cobaloximes
with molecular oxygen, Br2 and 2,4-dinitrobenzenesulfenyl chlo-
ride. These complexes have no affinity toward molecular oxygen
even though the CoeC bond length is similar to the alkyl/benzyl
cobaloximes. The reaction with electrophiles leads to the CoeC
bond cleavage and/or aryl ring substituted organometallic products
depending on the nature of aryl ring. The X-ray structure and
crystal packing exhibit some weak interactions to form different
types of supramolecular structural motifs.
Aryl cobaloximes 1e3 have already been reported earlier and
the complexes 4 and 5 were synthesized and purified by the pub-
lished procedure for 1e3 [14].
4.1.1. 4-N,N-dimethylaminophenylCo(dmgH)2Py (4)
Yield: 0.357 g (73%).1H NMR (500 MHz, CDCl3,
d
ppm): Pya ¼ 8.74
(2H, d, J ¼ 4.72 Hz), Pyb ¼ 7.34 (2H, t, J ¼ 6.86 Hz), Pyg ¼ 7.73 (1H, t,

2284
K. Kumar, B.D. Gupta / Journal of Organometallic Chemistry 696 (2011) 2280e2286
Table 4
Metric parameters of intermolecular CeH/O interactions for 4, 12 and 13.
Bond
Distance (Å)
CeH
Angle (ꢁ)
CeH/O
C/O
CeH/O
Compound 4
C8AeH8A1/O3
C20AeH20F/O2
0.960(3)
0.959(3)
2.382(2)
2.686(2)
3.115(4)
3.341(4)
132.79(18)
125.92(22)
Compound 12
C4eH4B/O1
C5eH5B/O3
C20eH20B/O8
C10eH10A/O8
C11eH11A/O7
0.959(4)
0.960(4)
0.959(6)
0.930(4)
0.930(4)
3.079(3)
3.047(3)
3.118(4)
2.511(4)
2.548(4)
4.007(6)
3.860(6)
4.025(7)
3.391(6)
3.252(6)
163.16(29)
143.28(29)
158.33(36)
157.92(30)
132.73(29)
Compound 13
C8eH8B/O8
C10eH10/O6
C9eH9/O8
C1eH1B/O2
C4eH4C/O2
0.979(4)
0.949(5)
0.950(4)
0.980(5)
0.980(4)
2.702(4)
2.561(3)
2.562(4)
2.965(3)
3.620(2)
3.243(6)
3.128(6)
3.314(6)
3.943(6)
4.529(5)
115.19(30)
118.56(30)
136.26(31)
175.76(31)
155.41(29)
J ¼ 4.9 Hz), 6.87e6.88 (1H, m), 6.64 (1H, d, J ¼ 3.7 Hz),
Fig. 3. Molecular structure of 12. All hydrogen atoms have been omitted for clarity
(hydrogen atoms involved in the intramolecular hydrogen-bonding interactions are
shown).
OeH/O ¼ 18.45 (s). 13C NMR (125 MHz, CDCl3,
d ppm): 150.77
(C]N, Cq), 150.08 (Pya), 138.10 (Pyg), 129.39, 126.73, 126.18, 125.45
(Pyb), 12.35. Anal. Calcd for C17H22CoN5O4S: C, 45.23; H, 4.91;
N, 15.52. Found: C, 45.01; H, 4.83; N, 15.62.
J ¼ 7.70 Hz), 7.17 (2H, d, J ¼ 9.0 Hz), 6.48 (2H, d, J ¼ 8.56 Hz), dmgH
(Me) ¼ 2.03 (12H, s), 2.82 (6H, s), OeH/O ¼ 18.47 (s). 13C NMR
(125 MHz, CDCl3,
d ppm): 150.19 (C]N, Cq), 150.12 (Pya), 147.83,
137.59 (Pyg),134.60,125.21 (Pyb),112.58, 40.87,12.19. Anal. Calcd for
C21H29CoN6O4: C, 51.64; H, 5.98; N,17.21. Found: C, 51.48; H, 5.89; N,
17.29.
4.1.2. 2-ThienylCo(dmgH)2Py (5)
Yield: 0.343 g (76%).1H NMR (500 MHz, CDCl3,
(2H, d, J ¼ 4.9 Hz), Pyb ¼ 7.36 (2H, t, J ¼ 7.0 Hz), Pyg ¼ 7.78 (1H, t,
J ¼ 7.6 Hz), dmgH(Me) ¼ 2.11 (12H, s), thienyl protons ¼ 7.15 (1H, d,
d
ppm): Pya ¼ 8.68
Fig. 4. Molecular structure of 13. All hydrogen atoms have been omitted for clarity
(hydrogen atoms involved in the intramolecular hydrogen-bonding interactions are
shown).
Fig. 5. (A) 1-D helical assembly resulting from CeH/O interactions in 12. (B) Space-
filling view of the left-handed helix of 12. All of the hydrogen atoms, except those
involved in hydrogen bonding, have been omitted for clarity.

K. Kumar, B.D. Gupta / Journal of Organometallic Chemistry 696 (2011) 2280e2286
2285
4.2. Reaction of aryl cobaloximes with Br2: general procedure
complexes 4 (CHCl3/CH3OH), 5 (CH2Cl2/CH3OH), 12 (EtOH/CH3OH/
CH2Cl2) and 13 (CHCl3/CH3OH). Single-crystal X-ray data were
A solution of Br2 (0.2 mmol in 10 mL dry CHCl3) was added drop
wise to a solution of organocobaloxime (0.2 mmol in 25 mL dry
CHCl3) in dark at 0 ꢁC under nitrogen atmosphere. On completion of
reaction, the solvent was evaporated under vacuum and the
resulting solid was washed with ether (3 ꢂ 5 mL). The ethereal
washings were evaporated to obtain organic product. The solid
inorganic part was further purified by column chromatography on
silica gel. The complexes 1e4 on reaction with bromine formed the
corresponding bromoarenes (6e9). These were characterized by 1H
NMR and mass spectrometry. However, complex 5 led to the
formation of 5-bromo-2-thienylCo(dmgH)2Py (10).
collected using graphite-monochromated Mo-K
a
radiation
(l
¼ 0.71073 Å) on “Bruker SMART APEX CCD diffractometer” at
100 K. The linear absorption coefficients, scattering factors for the
atoms and the anomalous dispersion corrections were taken from
the International Tables for X-ray Crystallography [41]. The program
SMART [42] was used for collecting frames of data, indexing
reflections, and determining lattice parameters. The data integra-
tion and reduction were processed with SAINT software [42]. An
empirical absorption correction was applied to the collected
reflections with SADABS [43] using XPREP [44]. All the structures
were solved by the direct method using the program SHELXS-97
[45] and were refined on F2 by the full-matrix least-squares
technique using the SHELXL-97 [45] program package. All non-
hydrogen atoms were refined with anisotropic displacement
parameters in all the structure. The hydrogen atom positions or
thermal parameters were not refined but were included in the
structure factor calculations. The thiophene ring in complex 5 was
found to be orientationally disordered and was modeled satis-
factorily. The ‘SQUEEZE’ option in PLATON was used to remove
disordered solvent molecule from the overall intensity data in
complex 13.
4.2.1. 5-Bromo-2-thienylCo(dmgH)2Py (10)
Yield: 0.056 g (53%). 1H NMR (500 MHz, CDCl3,
d
ppm): Pya ¼ 8.62
(2H, d, J ¼ 6.1 Hz), Pyb ¼ 7.35 (2H, t, J ¼ 6.4 Hz), Pyg ¼ 7.76 (1H, t,
J ¼ 7.6 Hz), dmgH(Me) ¼ 2.12 (12H, s), thienyl protons ¼ 6.72 (1H, d,
J ¼ 3.7 Hz), 6.36 (1H, d, J ¼ 3.7 Hz), OeH/O ¼ 18.35 (s). 13C NMR
(125 MHz, CDCl3, d ppm): 151.02 (C]N, Cq), 150.06 (Pya), 138.22 (Pyg),
130.70, 129.49, 125.51 (Pyb), 109.36, 12.42. Anal. Calcd for C17H21BrCo-
N5O4S: C, 38.50; H, 3.99; N, 13.21. Found: C, 38.66; H, 3.89; N, 13.09.
4.3. Reaction of aryl cobaloximes with 2,4-dinitrobenzenesulfenyl
chloride: general procedure
Acknowledgment
A solution of 2,4-dinitrobenzenesulfenyl chloride (0.2 mmol in
4 mL dry CH2Cl2) was added drop wise to a solution of aryl coba-
loxime (0.2 mmol in 10 mL dry CH2Cl2) in dark at 0 ꢁC under
nitrogen atmosphere. The reaction was stirred at 0 ꢁC for 1 h and
then slowly brought to room temperature and stirred further for
3 h. After completion of reaction, the solvent was evaporated under
vacuum to obtain crude products which were purified by column
chromatography on silica gel. Complexes 1e3 did not react with
2,4-dinitrobenzenesulfenyl chloride. However, complex 4 formed
11 and 12 and the complex 5 afforded 13.
This work has been supported by a grant from CSIR, New Delhi,
India. K. K. thanks UGC, New Delhi, India for Senior Research
Fellowship.
Appendix A. Supplementary material
CCDC 762046, 762047, 762048 and 762049 contains the
supplementary crystallographic data for this paper. These data can
be obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
4.3.1. 3-(2,4-dinitrobenzenesulfenyl)-4-NMe2C6H4Co(dmgH)2Py (12)
Yield: 0.078 g (57%). 1H NMR (500 MHz, CDCl3,
d ppm): 9.07 (1H,
Appendix. Supplementary data
d, J ¼ 2.2 Hz) Pya ¼ 8.65 (2H, d, J ¼ 6.2 Hz), Pyg ¼ 7.75
(1H, t, J ¼ 7.55 Hz), 7.94 (1H, dd, J ¼ 10.3 Hz, 1.4 Hz), 7.42 (1H, dd,
J ¼ 8.25 Hz, 2.05 Hz), 7.33e7.36 (3H, m), 6.84 (1H, d, J ¼ 8.95 Hz), 6.77
Supplementary data related to this article can be found online at
doi:10.1016/j.jorganchem.2010.12.008.
(1H, d,
J
¼
8.95 Hz), 2.62 (6H, s), dmgH (Me)
¼
2.04
(12H, s), OeH/O ¼ 18.34 (s). 13C NMR (125 MHz, CDCl3,
d
ppm):
References
153.30,150.53 (C]N, Cq),150.26,150.21 (Pya),143.98,143.58,143.05,
138.58, 138.07 (Pyg), 128.94, 125.89, 125.54 (Pyb), 121.56, 120.77,
119.09, 45.05,12.39. Anal. Calcd for C27H31CoN8O8S: C, 47.23; H, 4.55;
N, 16.32. Found: C, 47.31; H, 4.49; N, 16.35.
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4.3.2. 5-(2,4-dinitrobenzenesulfenyl)-2-thienylCo(dmgH)2Py (13)
Yield: 0.083 g (64%). 1H NMR (500 MHz, CDCl3,
d ppm):
Pya ¼ 8.63 (2H, d, J ¼ 5.2 Hz), Pyb ¼ 7.39 (2H, t, J ¼ 6.6 Hz),
Pyg ¼ 7.80 (1H, t, J ¼ 7.8 Hz), dmgH(Me) ¼ 2.17 (12H, s), aromatic/
thienyl protons ¼ 9.03 (1H, d, J ¼ 2.0 Hz), 8.09 (1H, dd, J ¼ 8.8 Hz,
2.0 Hz), 7.11 (1H, d, J ¼ 3.2 Hz), 7.06 (1H, d, J ¼ 9.2 Hz), 6.74 (1H, d,
J ¼ 2.8 Hz), OeH/O ¼ 18.35 (s). 13C NMR (125 MHz, CDCl3, d ppm):
151.18 (C]N, Cq),150.75,149.99 (Pya),144.05, 143.38,138.42,138.36
(Pyg), 132.46, 129.08, 126.60, 125.64 (Pyb), 124.45, 121.07, 12.48.
Anal. Calcd for C23H24CoN7O8S2: C, 42.53; H, 3.72; N, 15.09. Found:
C, 42.18; H, 3.80; N, 15.14.
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a and d indicates bending towards R and displacement toward
base and vice versa.
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CDCl3,
d
ppm): 9.07 (1H, d, J ¼ 2.2 Hz), 8.10 (1H, dd, J ¼ 9.04 Hz, 2.2 Hz), 7.37
(2H, d, J ¼ 8.8 Hz), 7.04 (1H, d, J ¼ 9.04 Hz), 6.78 (2H, d, J ¼ 9.04 Hz), 3.06 (6H,
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40.19.
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NMR (500 MHz, CDCl3,
d
ppm): 9.10 (1H, d, J ¼ 2.3 Hz), 8.28e8.25 (1H, m),
7.26 (1H, d, J ¼ 4 Hz), 7.22e7.21 (1H, m), 7.07 (1H, d, J ¼ 3.45 Hz). 13C NMR
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d ppm): 145.04, 143.98, 139.79, 139.13, 137.94, 132.22,
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