Inorganic cobaloximes with mixed dioxime equatorial ligands: A convenient one pot synthesis and cis influence studies: X-ray crystal structures of N3CoIII(dmgH)(dpgH)Py and N3CoIII(chgH)(dpgH)Py

Article abstract of DOI:10.1016/S0022-328X(01)00817-8

A simple and general route to the synthesis of cobaloxime with mixed dioxime ligands, XCo(L)(L′)Py, L,L′=dmgH/dpgH and chgH/dpgH; X=Cl, Br, NO₂, N₃, has been described. These compounds are reported for the first time. The synthesis is confirmed by the X-ray structures of N₃Co(dmgH)(dpgH)Py and N₃Co(chgH)(dpgH)Py. The cis and trans effects on these complexes and on XCo(L)₂Py (L=dmgH, chgH, dpgH; X=Cl, Br, NO₂, N₃) complexes have been studied by ¹H-, ¹³C-NMR, UV, and X-ray. For a range of X ligands, a clear trend between the ¹H, ¹³C chemical shifts of the equatorial and axial ligands as well as with the Co-dioxime CT band has been observed. The analysis of the ¹³C values and X-ray data shows that one dioxime wing effects the other dioxime wing in the mixed dioxime complexes.

Full text of DOI:10.1016/S0022-328X(01)00817-8

Journal of Organometallic Chemistry 629 (2001) 83–92
www.elsevier.com/locate/jorganchem
Inorganic cobaloximes with mixed dioxime equatorial ligands: a
convenient one pot synthesis and cis influence studies: X-ray
crystal structures of N3CoIII(dmgH)(dpgH)Py and
N3CoIII(chgH)(dpgH)Py
B.D. Gupta a,*, Usha Tiwari a, T. Barclay b, W. Cordes b
a Department of Chemistry, IIT Kanpur, Kanpur, UP 208016, India
b Department of Chemistry and Biochemistry, Uni6ersity of Arkansas, Fayette6ille, AR, USA
Received 15 February 2001; accepted 29 March 2001
Abstract
A simple and general route to the synthesis of cobaloxime with mixed dioxime ligands, XCo(L)(L%)Py, L,L%=dmgH/dpgH and
chgH/dpgH; X=Cl, Br, NO2, N3, has been described. These compounds are reported for the first time. The synthesis is confirmed
by the X-ray structures of N3Co(dmgH)(dpgH)Py and N3Co(chgH)(dpgH)Py. The cis and trans effects on these complexes and
1
on XCo(L)2Py (L=dmgH, chgH, dpgH; X=Cl, Br, NO2, N3) complexes have been studied by H-, 13C-NMR, UV, and X-ray.
1
For a range of X ligands, a clear trend between the H, 13C chemical shifts of the equatorial and axial ligands as well as with the
Co–dioxime CT band has been observed. The analysis of the 13C values and X-ray data shows that one dioxime wing effects the
other dioxime wing in the mixed dioxime complexes. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Cobalt; Cobaloxime; Dioxime; cis–trans Influence
dioxime moiety. An increase in the bulkiness of L also
lengthens the CoꢀC bond (steric trans influence). The
1. Introduction
The studies on organocobaloximes1 in the past three
decades has provided a considerable amount of struc-
tural, spectroscopic, thermodynamic, and kinetic data
for a wide variety of R and L ligands [1]. The trends in
these properties as a function of the steric and elec-
tronic properties of the axial R and L ligands have been
qualitatively interpreted [2]. Attempts have also been
made to achieve a quantitative rationalization as well
[3]. For example, the weakening of the CoꢀC bond
(steric cis influence) is essentially related to the increase
in the bulkiness of R, which sterically interacts with the
weakening of the CoꢀL bond (electronic trans effect
and influence) has been attributed to the electron do-
nating ability of R as well as to the bulkiness of R,
which through a bending of the dioxime moiety to-
wards L lengthens the CoꢀL bond (steric trans influ-
ence). Also, an increase in the bulkiness of L determines
the lengthening of the CoꢀL bond (steric cis influence).
Most of the above information has come from the
study of cobaloximes (both organic and inorganic) with
dmgH as the equatorial ligand. The studies involving
other oximes with varying steric and electronic proper-
ties such as gH [4], chgH [5] and dpgH [6] have been
few. We have recently shown that the cis influence of
the dioxime ligand in alkyl cobaloximes varies in the
order dpgH\chgH\dmgH [7]. A comparison of the
structural parameters of bis(dioxime) vitamin B12 mod-
els have indicated that lateral compression and the
a-bending angle are related to the steric bulkiness of the
dioxime substituent [8].
* Corresponding author. Tel.: +91-512-598338; fax: +91-512-
597436.
E-mail address: bdg@iitk.ac.in (B.D. Gupta).
1 General formula: RCo(L)2B, where R, an organic group
s
bonded to cobalt; B, axial base trans to the organic group; L, dioxime
ligand (e.g. gH, glyoxime; dmgH, dimethylglyoxime); chgH, 1,2-cy-
clohexanedione dioxime; dpgH, diphenylglyoxime (all monoanions).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)00817-8

84
B.D. Gupta et al. / Journal of Organometallic Chemistry 629 (2001) 83–92
In this paper we report the synthesis and study of
There have been only a very few studies on the effect
complexes of the type trans XCo(L)2Py, L=dmgH,
chgH, dpgH and XCo(L)(L%)Py, with L=dmgH, L%=
dpgH and L=chgH and L%=dpgH; X=Cl, Br, NO2,
N3. The spectroscopic studies (1H, 13C, UV) on these
complexes have been carried out. The aim of the study
of the equatorial ligand field on the axial groups (cis
influence). This is due to the paucity of complexes with
dioximes other than dmgH.
The spectroscopic characteristics of cobaloximes with
dmgH as the equatorial ligand show a systematic varia-
tion with X [9]. Much of the information on the
1
is: (a) to verify if the trends in H-NMR and UV data,
1
reported earlier for dmgH complexes, also apply to
cobaloximes with other dioxime equatorial ligands; (b)
to check if 13C-NMR gives similar or better informa-
correlation study has been derived from the H-NMR
chemical shifts as only a few cobaloximes have been
characterized by both 1H- and 13C-NMR [[6b,10]].
Studies with 13C-NMR are, therefore, lacking.
We believe that a more comprehensive spectroscopic
and structural study of a large number of cobaloximes
with different dioximes and various X ligands (having a
range of sigma and pi donor/acceptor properties) would
enable a more rigorous treatment of the statistical data
with a greater degree of confidence. The present study,
therefore, gains importance in this direction.
1
tion than H-NMR; (c) to check if there is any correla-
1
tion in the H-, 13C-NMR, and UV data; and (d) to
check if one wing of the equatorial dioxime moiety has
any effect on the other wing. Besides, we also report for
the first time the crystal structures of inorganic coba-
loxime with mixed dioxime equatorial ligands,
N3Co(dmgH)(dpgH)Py and N3Co(chgH)(dpgH)Py.
2. Results and discussion
Table 1
Molar distribution (%) in the reaction of (1b) and (5b) with X−
2.1. Synthesis
1a–8a
1c–4c
1b–8b
Inorganic cobaloximes, XCo(dmgH)2Py, have been
well described in the literature [1] [9] [10b]. In general,
two procedures have been used for the preparation of
these complexes: (a) by aerial oxidation of the stoichio-
metric mixture of the reactants [11] and (b) by substitu-
tion of the chloro group in chlorocobaloxime by
another nucleophile [10] [12]. However, very little is
known on the corresponding dpgH [9] and chgH com-
plexes [5c] and a thorough literature survey shows that
inorganic cobaloximes with mixed dioxime ligands,
XCo(L)(L%)Py, have never been synthesized before.
We have successfully utilized the substitution method
for the synthesis of XCo(dmgH)(dpgH)Py and
XCo(chgH)(dpgH)Py. Three products are isolated in
each reaction (see Table 1 for molar distribution, see
Fig. 1). This may indicate that either the chloro group
or the X group has randomized during the reaction. It
is very difficult to comment whether the chloro group
randomizes before its reaction with X− or the random-
ization occurs after the substitution has taken place.
Further studies are underway in this direction.
53.1
24.0
53.0
11.8
25.8
7.8
2.0
27.4
0.7
52.0
5.7
7.4
30.4
17.7
46.9
48.4
46.3
36.2
68.5
84.8
61.7
81.7
7.8
0.5
2.2. Spectroscopy
1
2.2.1. General comments on the H- and 13C-NMR
assignments
1
The H-NMR spectra of these complexes are easily
assigned based on the chemical shifts. The signals are
assigned according to their relative intensities and the
assignment is consistent with those of the related com-
pounds previously described [9] [10] [12].
Since the 13C values have been assigned for only a
few inorganic cobaloximes in the literature [6b] [10],
further comments are needed on its assignment.
Fig. 1. Structure of cobaloximes.

B.D. Gupta et al. / Journal of Organometallic Chemistry 629 (2001) 83–92
85
Table 2
1H-NMR data for compounds 1a–8a, 1b–8b, and 1c–4c
Compound
dmgH (Me)/chgH (C1 and C2)
Pyridine
HꢀOH
Phenyl
a
b
l
1a
2a
3a
4a
5a
6a
7a
8a
1c
2c
3c
4c
1b
2b
3b
4b
5b
6b
7b
8b b
2.40
2.40
2.33
2.41
8.25
8.25
8.32
8.28
8.26
8.25
8.30
8.32
8.59
8.59
8.63
8.64
8.44
8.43
8.49
8.54
8.42
8.41
8.48
8.47
7.26
7.26
7.27
7.23
7.27
7.26
7.24
7.28
7.36
7.41
7.41
7.39
7.73
7.70
7.73
7.70
7.74
7.73
7.72
7.75
7.83
7.84
7.86
7.85
7.77
7.76
7.80
7.78
7.78
7.76
7.81
7.79
18.15
18.12
–
–
–
–
–
–
–
–
–
–
1.65–1.79, 2.78–2.86, 3.04–3.12
1.65–1.77, 2.77–2.85, 3.05–3.14
1.61–1.72, 2.71–2.73, 2.95–2.96
1.65–1.83, 2.74–2.82, 3.06–3.13
–
–
–
–
2.45
2.45
2.39
2.41
17.36
17.35
–
17.55
18.61
18.62
18.45
18.53
–
7.21–7.30
7.20–7.30
7.19–7.33
7.23–7.32
7.18–7.25
7.17–7.33
7.15–7.30
7.23–7.31
7.17–7.27
7.16–7.33
7.14–7.28
7.17–7.28
7.28
a
–
7.34
18.14
18.23
18.01
18.01
17.86
17.93
a
1.68–1.82, 2.82–2.90, 3.08–3.16
1.70–1.79, 2.83–2.91, 3.08–3.16
1.69–1.79, 2.77–2.83, 3.01–3.07
1.71–1.83, 2.78–2.88, 3.06–3.14
7.30
a
7.36
7.32
a Merged with dpgH resonance.
b It is chiral and gives a optical rotation of +14°.
The 13C resonance of dmgH (Me), chgH (C1 and
C2), dpgH2 (C*, Ca, Cb, Cg), Pyb and Pyg are easily
assigned based on their chemical shifts. The assignment
of CꢁN (dmgH or chgH), CꢁN (dpgH) and Pya should
be done with utmost care as these occur very close to
each other. The assigned values match the literature
values, though these are few in number. Our previous
2.3. cis and trans Influence of X
The trans influence of the ligand X can be monitored
through the coordination shift (Dl=lcomplex−lfree py
)
of pyridine (a, b, g). The cis influence of X can be
monitored by the 13C resonance of CꢁN(oximinic) and
1
also by Dl H or Dl 13C of pyridine (a, b, g) when X
assignments
in
ArCH2Co(dpgH)(dioxime)Py
is held constant and the equatorial ligand is changed.
These are separately discussed below.
(dioxime=dmgH, chgH) [13] complexes have been
quite helpful.
1
2.3.1. H chemical shifts
2.2.1.1. XCo(L2)Py (1a–8a and 1c–4c). CꢁN and Pya
resonances occur very close to each other. The peak at
higher ppm (l) value is assigned to CꢁN and the peak
with lower l value is assigned to Pya. In general, CꢁN
has lower intensity as compared to Pya (1a–4a, 1c–4c).
However, in case of 5a–8a CꢁN has slightly higher
intensity than Pya. It is expected that CꢁN should be of
lower intensity as it is a quaternary carbon.
1
2.3.1.1. OꢀH···O resonance. H-NMR (l) values for all
the compounds are given in Table 2. In certain cases we
have not been able to detect the OꢀH···O peak. We
have observed a high upfield shift in chgH complexes,
nearly 0.6 ppm as compared to dmgH complexes and
1.25 ppm as compared to dpgH complexes. OꢀH···O
resonance follows the order dpgH (1c–4c)\dmgH
(1a–4a)\chgH (5a–8a). This may open up the ques-
tion as to how the replacement of two methyl groups by
the cyclohexane ring residue alters the anisotropy of the
cobalt atom or [Co(chgH)2]+ unit so profoundly so as
to merit such a large shift. This is in view of the recent
reports on the dmgH complexes with planar nitrogen
ligands where the magnetic anisotropy of the entire
[Co(L)2]+ moiety [9] or the anisotropy of cobalt atom
2.2.1.2. XCo(dmgH)(dpgH)Py (1b–4b) and XCo(chgH)-
(dpgH)Py (5b–8b). Three peaks are observed in a re-
gion that is very close to each other. The highest
intensity peak with the lowest l value is assigned to
Pya. Between the other two peaks for CꢁN (dpgH) and
CꢁN (dmgH or chgH), the peak with higher l value is
assigned to CꢁN (dpgH) and the other peak to CꢁN
(dmgH or chgH).
1
[10] have been invoked to explain the H-NMR shifts.
The large shift in dpgH complexes compared to dmgH
or chgH may be due to the high ring currents of the
2 See Ref. [9] for numbering in dpgH.

86
B.D. Gupta et al. / Journal of Organometallic Chemistry 629 (2001) 83–92
Table 3
13C NMR data of compounds 1a–8a, 1c–4c and 1b–8b
a
Compound
Ligand
pyridine
dmgH
(Me)
chgH
dpgH
C*
CꢁN b
a
b
g
C1 & C2
Ca
Cg
Cb
1a
2a
3a
4a
5a
6a
7a
8a
1b
2b
3b
4b
5b
6b
7b
8b
1c
2c
3c
4c
152.59
153.02
152.57
152.14
153.54
154.04
153.49
153.12
153.10, 153.10
153.56, 153.45
153.22, 153.04
152.74,152.62
153.95, 153.07
154.32, 153.61
154.06, 153.00
153.44, 152.71
153.58
150.98
150.66
150.57
151.21
151.03
150.70
150.67
151.26
151.04
150.55
150.64
151.05
151.04
150.62
150.55
151.06
151.04
150.65
150.65
151.23
125.73
125.68
125.74
125.71
125.70
125.67
125.70
125.73
125.87
125.97
125.88
125.86
125.91
125.93
125.95
125.89
126.10
126.12
126.08
126.11
139.07
138.90
139.08
138.87
139.04
138.89
139.01
138.85
139.17
139.30
139.20
139.12
139.26
139.22
139.36
139.12
139.43
139.39
139.42
139.28
13.10
13.16
12.83
12.91
–
–
–
–
13.20
13.26
12.99
12.91
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
21.32, 26.13
21.36, 26.25
21.29, 25.95
21.39, 25.99
–
–
–
–
21.18, 26.19
21.18, 26.26
21.10, 26.02
21.11, 25.93
–
–
–
–
129.90
129.98
129.62
129.82
129.92
130.02
129.59
129.79
129.80
129.75
129.82
129.92
129.74
129.66
129.55
129.54
129.73
129.67
129.55
129.56
129.67
129.70
129.68
129.71
129.41
129.36
129.52
129.36
129.35
129.33
129.50
129.31
129.55
129.64
129.30
129.33
127.90
127.90
127.97
127.84
127.88
127.90
127.95
127.83
127.93
127.95
128.01
127.96
–
–
–
–
154.05
153.72
153.34
a See Ref.[6] for nomenclature.
b 1a–4a refer to dmgH (CꢁN), 5a–8a refer to chgH (CꢁN), 1c–4c refer to dpgH (CꢁN). In 1b–8b, the first value is for dpgH and the second is
for dmgH or chgH.
phenyl groups. In the mixed ligand complexes (1b–8b),
OꢀH···O appears in between the values for the pure
complexes 1a–8a and 1c–4c. This may indicate that
both wings of the equatorial ligand contribute to the
overall effect and thus support the model in which it
becomes more appropriate to explain the 1H-NMR
shifts based on the magnetic anisotropy of the entire
[Co(L)2]+ unit.
ligand and applies to all five series of complexes
reported here. However, we believe that one should
be careful in arriving at such a conclusion that is
based on such small variations. The Dl 13C Pya
values, on the other hand, do show larger variation
and lead to a different order of these ligands (see
Section 2.3.2.1 (1)).
3. The trans influence of the X group on pyridine is
correlated with the cis influence on the CꢁN bond
and the methyl protons of the dmgH group in
complexes 1a–4a and 1b–4b. Only the a protons
show a clear trend and Dl 1H Pya has a linear
variation with 13C of CꢁN(oximinic) and l 1H Me
(dmgH). The least-squares equations obtained in the
correlation are given below.3 While plotting, we
2.3.1.2. Pyridine resonance.
1. To observe the cis influence of the X group, we find
that the magnitude of the coordination shift (Dl 1H)
for pyridine (a, b, g) is more for dpgH complexes
(1c–4c) as compared to the dmgH or chgH com-
plexes (1a–8a). The same observation is made in the
13C-NMR chemical shifts (discussed later) and this
is similar to our earlier observation [5c]. Also, the
1
have also included the corresponding Dl H values
for RCo(L)2Py (L=dmgH, chgH and dpgH) [7]
and RCo(L)(L%)Py (L=dmgH or chgH; L%=dpgH
and R=Me, Et, Pr and Bu).4 This is done in order
to see if the correlations in inorganic complexes also
apply to organometallic complexes.
1
coordination shift follows the order Dl H Pyg\Dl
1
1H Pyb\Dl H Pya for all complexes (Table 3).
2. The trans influence of the X group is monitored
1
through the Dl H Pya value. The change in the X
group leads to a small variation in Dl 1H Pya
(B0.05 ppm) and no useful information is antici-
pated from this small shift. However, recently,
Lopez et al. [9] have listed the ligands, based on
Compounds (1a–4a and X=Me, Et, Pr, Bu)
l13C (CꢁN)=150.02 (13)−8.63 (63) Dl 1H Pya
(r2=0.96, estimated S.D.=0.27 ppm)
1
small upfield shifts (B0.05 ppm), of Dl H Pya in
dmgH complexes. We obtain an order Cl:Br\
NO2:N3 that is similar that obtained by Lopez et
al. [9]. This order is independent of the equatorial
3 The program ORIGIN and eight data points have been used for
each correlation.
4 B.D. Gupta, Usha Tiwari, and R. Yamuna, unpublished data.

B.D. Gupta et al. / Journal of Organometallic Chemistry 629 (2001) 83–92
87
Table 4
13C-NMR data (CꢁN) of XCo(L2)Py and XCo(L)(L%)Py
a
X
dmgH
ChgH
dpgH
dpgH
dmgH a
dpgH a
dhgH a
Cl
Br
NO2
N3
Me
Et
152.59
153.02
152.57
152.14
149.89
149.92
149.95
149.89
153.54
154.04
153.49
153.12
150.04
150.07
150.00
150.03
153.58
154.05
153.72
153.34
150.90
150.85
150.70
150.80
153.10
153.56
153.22
152.74
150.57
150.57
150.64
150.63
153.10
153.45
153.04
152.62
150.05
150.05
149.99
150.02
153.95
154.32
154.06
153.44
150.59
150.59
150.68
150.66
153.07
153.61
153.00
152.71
150.18
150.13
150.23
150.21
Pr
Bu
a Unpublished work (the values in italics) from our laboratory.
Compounds (5a–8a and X=Me, Et, Pr, Bu)
l13C (CꢁN)=149.79 (13)−12.95 (62) Dl 1H Pya
(r2=0.99, estimated S.D.=0.24 ppm)
Compounds (1c–4c and X=Me, Et, Pr, Bu)
l13C (CꢁN)=153.97 (24)−8.86 (98) Dl 1H Pya
(r2=0.92, estimated S.D.=0.44 ppm)
compared to the corresponding values in dmgH or
chgH complexes (1a–8a). However, there is no
change in the Pya value. A similar observation is
made in the mixed ligand complexes where l 13C
Pyb and l 13C Pyg occur downfield compared to the
pure complexes (i.e. 1b–4b\1a–4a and 5b–8b\
5a–8a).
Compounds (1b–4b and X=Me, Et, Pr, Bu)
1
l13C (CꢁN)=152.33 (7)−8.65 (44) Dl H Pya (r2=
0.99, estimated S.D.=0.18 ppm)
2.3.2.2. CꢁN resonance. The cis influence of X can be
Compounds (5b–8b and X=Me, Et, Pr, Bu)
followed through the 13C resonance of CꢁN(oximinic)
.
1
l13C (CꢁN)=152.68 (9)−9.94 (52) Dl H Pya (r2=
This is done in two ways (Table 4):
0.99, estimated S.D.=0.24 ppm)
1. On keeping the same X but changing the equatorial
ligand, we observe that the l 13C (CꢁN) values in
dpgH (1c–4c) and chgH (5a–8a) complexes occur
downfield by :1.0 ppm as compared to the values
in dmgH complexes (1a–4a).
Compounds (1a–4a and X=Me, Et, Pr, Bu)
1
l1H (Me)=2.11(1)−0.90 (6) Dl H Pya (r2=0.99,
estimated S.D.=0.03 ppm)
Compounds (1b–4b and X=Me, Et, Pr, Bu)
1
l1H (Me)=2.34(8)+0.81(5) Dl H Pya (r2=0.99,
2. The change in X group within the same series effects
estimated S.D.=0.02 ppm)
l
13C (CꢁN) and it follows the order Br\Cl:
NO2\N3 for all complexes.
2.3.2. 13C-NMR chemical shifts
2.3.2.3. Inorganic cobaloximes 6ersus organocoba-
loximes. The change in X group (from Cl, Br, NO2, N3
to alkyl groups Me, Et, Pr, Bu), within the same series,
effects l 13C for CꢁN, Pya, Pyb, Pyg. All these values
occur downfield by 2–3 ppm in inorganic cobaloximes
(Table 4).
2.3.2.1. Pyridine resonance.
1. The 13C resonance of pyridine on coordination to
the cobaloxime moiety shifts downfield and this
coordination shift (Dl=lcomplex−dfree py) follows
the order D13C Pyg\D13C Pyb\D13C Pya for all
complexes (Table 3). This order is similar to the one
Correlations: The coordination shift of pyridine (Dl
13C Pya, Dl 13C Pyb and Dl 13C Pyg) with the variation
1
observed above in H-NMR studies. This coordina-
in X correlate well with the l 13C of the CꢁNoximinic
.
tion shift can be taken as a measure of the trans
influence of the axial ligand X.
Also, Dl 13C Pya correlates well with the l 13C Me
(dmgH). For all the correlations, the 13C values for
alkyl cobaloximes, RCo(L2)Py (L=dmgH, chgH and
dpgH) [7] and RCo(L)(L%)Py (L=dmgH or chgH and
L%=dpgH) and R=Me, Et, Pr and Bu have also been
included while plotting the values.5
2. The change in X group, within the same series seems
to effect the 13C values for Pya but not Pyb and Pyg.
For example, Dl 13C Pya in 1a–8a and 1c–4c
follows the order N3\Cl\Br]NO2 and in 1b–8b
it follows N3:Cl\Br:NO2. Notice that this or-
Compounds (1a–4a and X=Me, Et, Pr, Bu)
1
der is different to what we observed based on Dl H
l
13C (CꢁN)=1.28 (18) Dl 13C Pya+151.17 (18)
Pya (see Section 2.3.1.2 (2)). However, D13C Pyb and
(r2=0.90, estimated S.D.=0.50 ppm)
Dl 13C Pyg remain similar.
3. To check the cis influence of the X group, we keep
the same X but change the equatorial ligand (L). It
is observed that the l 13C (Pyb and Pyg) in dpgH
complexes 1c–4c move downfield by :0.4 ppm as
5 B.D. Gupta, Veena Singh, R. Yamuna, and Usha Tiwari, unpub-
lished data.

88
B.D. Gupta et al. / Journal of Organometallic Chemistry 629 (2001) 83–92
2.3.2.4. cis Influence of the equatorial dioxime ligand. In
l
13C (CꢁN)=3.77 (31) Dl 13C Pyb+145.07 (52)
(r2=0.96, estimated S.D.=0.31 ppm)
view of our recent study on the cis influence in
organocobaloximes [5c] [7] [8] , the present results allow
us to extend our earlier conclusions further. The extent
of electron density on the Co(dioxime)2 chelate ring for
different dioximes (X and B held constant) can be
understood by comparing 13C chemical shifts of (CꢁN)
of the equatorial dioxime ligand, for example for X=
Cl, Br, NO2, N3, Me, Et, Pr, Bu and B=Py, this
follows the order dpgH]chgH\dmgH\gH. In this
order only three values of the gH complex (X=Cl, Me,
Et) are used [5c].
l
13C (CꢁN)=1.56 (11) Dl 13C Pyg+147.76(11)
(r2=0.96, estimated S.D.=0.28 ppm)
Compounds (5a–8a and X=Me, Et, Pr, Bu)
l
13C (CꢁN)=3.00 (57) Dl 13C Pya+150.04 (45)
(r2=0.83, estimated S.D.=0.86 ppm)
13C (CꢁN)=5.01 (41) Dl 13C Pyb+143.65 (r2=
0.96, estimated S.D.=0.40 ppm)
l
l
13C (CꢁN)=2.08 (13) Dl 13C Pyg+147.16 (r2=
0.99, estimated S.D.=0.31 ppm)
Compounds (1c–4c and X=Me, Et, Pr, Bu)
The cis influence of the dioximes, based on the
coordination shift of the pyridine ring protons or car-
bon, has already been discussed (see Sections 2.3.1.2
and 2.3.2.1).
l
13C (CꢁN)=2.67 (60) Dl 13C Pya+150.53 (48)
(r2=0.76, estimated S.D.=0.81 ppm)
13C (CꢁN)=4.46 (46) Dl 13C Pyb+143.03(95)
(r2=0.94, estimated S.D.=0.40 ppm)
l
l
13C (CꢁN)=1.90 (11) Dl 13C Pyg+146.99 (32)
(r2=0.99, estimated S.D.=0.24 ppm)
2.3.2.5. Effect of one equatorial dioxime wing on the
other dioxime wing. We have considered whether one
equatorial dioxime wing has any effect on the other
dioxime wing, i.e. the effect of dmgH or chgH wing on
Compounds (1b–4b and X=Me, Et, Pr, Bu)
l
13C (CꢁN)=1.64 (26) Dl 13C Pya+151.45 (21)
(r2=0.88, estimated S.D.=0.55 ppm)
13C (CꢁN)=4.58 (24) Dl 13C Pyb+143.25 (45)
(r2=0.99, estimated S.D.=0.19 ppm)
l
1
the dpgH wing. H-NMR data show that the methyl
(dmgH) resonance in 1a–4a appears at 0.05 ppm upfi-
eld as compared to the value in 1b–4b. Similarly, the
cyclohexyl protons in 5b–8b appear at 0.05 ppm
downfield than in 5a–8a (Table 2). A similar observa-
tion is made in 13C-NMR values (Table 5). For exam-
ple, the methyl (dmgH) resonance in 1b–4b appears at
0.1 ppm downfield than in 1a–4a. There is no change in
the chemical shift of the C1 carbon in 5b–8b compared
to 5a–8a, but the C2 carbon appears at 0.15 ppm
upfield in the former as compared to the latter. The
comparison of the 13C values of the phenyl carbons in
1b–14b with 1c–4c also does not give any information
since these are very close to each other.
l
13C (CꢁN)=1.67 (9) Dl 13C Pyg+147.65 (23)
(r2=0.99, estimated S.D.=0.19 ppm)
Compounds (5b–8b and X=Me, Et, Pr, Bu)
l
13C (CꢁN)=3.33 (92) Dl 13C Pya+150.30 (72)
(r2=0.74, estimated S.D.=0.97 ppm)
13C (CꢁN)=5.68 (33) Dl 13C Pyb+141.47 (64)
(r2=0.99, estimated S.D.=0.27 ppm)
l
l
13C (CꢁN)=2.07 (10) Dl 13C Pyg+146.98 (27)
(r2=0.99, estimated S.D.=0.23 ppm)
Compounds (1a–4a and X=Me, Et, Pr, Bu)
l
13C Me(dmgH)=12.37(6)+0.579 (6) Dl 13C Pya
(r2=0.94, estimated S.D.=0.17 ppm)
Table 5
Coordination shift
X
1a–4a
5a–8a
1c–4c
1b–4b
5b–8b
1a–4a
5a–8a
1c–4c
1b–4b
5b–8b
Z
13C Pyh
Z1H Pyh
−0.32
−0.32
−0.25
−0.29
Cl
Br
NO2
N3
1.17
0.84
0.75
1.39
1.21
0.88
0.85
1.44
1.22
0.83
0.85
1.41
1.20
0.73
0.82
1.23
1.22
0.80
0.73
1.24
−0.31
−0.32
−0.27
−0.25
0.02
0.02
0.06
0.07
−0.13
−0.14
−0.08
−0.03
−0.15
−0.16
−0.07
−0.10
Z
13C Pyi
Z1H Pyi
0.21
0.21
0.22
0.18
Cl
Br
NO2
N3
2.00
1.95
2.01
1.98
1.97
1.94
1.97
2.00
2.37
2.39
2.35
2.38
2.14
2.24
2.15
2.13
2.18
2.20
2.22
2.16
0.22
0.21
0.19
0.23
0.31
0.36
0.36
0.34
0.23
–
0.29
–
0.25
–
0.29
0.27
Z
13C Pyk
Z1H Pyk
0.30
0.27
0.30
0.27
Cl
Br
NO2
N3
3.18
3.01
3.19
2.98
3.15
3.00
3.12
2.96
3.54
3.50
3.53
3.39
3.28
3.41
3.31
3.23
3.37
3.33
3.47
3.23
0.31
0.30
0.29
0.32
0.40
0.41
0.43
0.42
0.34
0.33
0.37
0.35
0.35
0.33
0.38
0.36
Free pyridine [5].

B.D. Gupta et al. / Journal of Organometallic Chemistry 629 (2001) 83–92
89
Table 6
umax (CHCl3) (log m) for XCo(L2)Py and XCo(L)(L%)Py
X
dmgH (1a–4a)
chgH (5a–8a)
dpgH (1c–4c)
dmgH/dpgH (1b–4b)
chgH/dpgH (5b–8b)
Cl
Br
NO2
N3
255.2 (3.70)
260.4 (3.57)
253.4 (3.51)
250.4 (3.38)
257.0 (4.30)
260.2 (3.57)
253.8 (4.56)
253.0 (4.20)
245.2 (3.75)
260.0 (3.73)
260.4 (3.77)
255.5 (3.70)
259.0 (4.62)
263.8 (3.52)
259.6 (3.45)
254.4 (3.50)
244.8 (3.78)
258.2 (3.52)
259.2 (3.63)
255.6 (3.36)
The l 13C (CꢁN) seems to be more sensitive to
changes in the equatorial plane. The comparison of l
13C (CꢁN) in 1c–4c with the l 13C (CꢁN) (dpgH) in
1b–4b shows that the latter moves upfield by about 0.5
ppm whereas the l 13C (CꢁN) (dpgH) value moves
downfield by about 0.4 ppm in case of 5b–8b. This
further means that there is a higher charge density on
CꢁN (dpgH) in 1b–4b and lower in 5b–8b as compared
to the pure complexes 1c–4c. We believe that this is due
to the effect of one dioxime wing on the other dioxime
wing. Recently, we have made similar observation in
the BnCo(dmgH)(dpgH)Py and BnCo(chgH)(dpgH)Py
complexes [13]. However, we cannot comment on the
origin of this effect at this stage but it might be due to
the electronic effect of one wing on the other. Studies
are underway to see if it is a general phenomenon and
applies to other mixed dioximes complexes also.
applied to the reflection intensities for these two
compounds.
The structures were isotropically refined by full-ma-
trix least-squares method, using the NRC 386 and the
SHELXL-97 computer programs. The function mini-
mized was [ꢀW(IFoI−IFcI)2]0.5, where W=[|2(Fo2)+
(0.05F2o)2]. The hydrogen atoms of the OH groups were
located on difference map positions (see Table 8 for
OꢀHꢀO distances). The orientations of the methyl H-
atoms were also determined from difference maps and
refined with an overall isotropic temperature factor.
The most outstanding structural parameters of these
two compounds are summarized in Table 8 and the
perspective views of the molecular structures together
with the atom numbering schemes are shown in Figs. 2
and 3.
2.4.2. Description of the structures
2.3.3. UV–6is spectra
The cobalt atom is linked to four nitrogen atoms
belonging to the equatorial plane. Out of this, two
nitrogen atoms belong to dpgH and the other two
belong to dmgH or chgh ligand. The Co-atom displays
an approximately octahedral coordination. The Co-
All the cobaloximes exhibit an intense Co–dioxH CT
band between 245 and 260 nm in chloroform (Table 6).
The umax values for any X group is independent of the
equatorial ligand, i.e. for any particular X the umax
value is almost same for all the equatorial ligands. We
have not been able to achieve any good correlation of
,
atom in compound 4b is 0.037 (2) A out of the mean
plane of the four nitrogen atoms, while it is 0.028(2) A
,
1
umax with Dl H Py or Dl 13C Py values (in all, 30
in compound 8b. The displacement is towards pyridine
in both cases. Pyridine ring is practically planar and
parallel to the glyoxime CꢀC bonds, its conformation
being defined by a twist of 78.79 and 84.2° for the
compounds 4b and 8b, respectively. The CoꢀN6(ax) and
CoꢀN5(ax) bonds are approximately perpendicular (90°)
correlations were tried).
2.4. X-ray crystal structures
2.4.1. Crystal structure determination and refinements
Orange crystals were obtained by slow evaporation
of the solutions of the complexes in methanol. A crystal
of small size (as in Table 7) was selected and mounted
on an Enraf–Nonius CAD-4 diffractometer equipped
with a graphite monochromator. The unit cell parame-
ters were determined for 25 reflections and the cell
parameters were refined by full-matrix least-squares on
F2. Intensities were collected with Mo–Ka radiation,
using the multiscan technique. For compound 4b, 4663
intensities were measured in the range of 3.21–26.00°
and 4663 were considered as observed applying the
condition [I\2|(I)], while 6930 reflections were mea-
sured for compound 8b in the range of 2.65–26.00°,
from which 4815 were considered as observed. Empiri-
cal absorption corrections based on „-scan data were
to the equatorial plane as seen in the N(eq)ꢀCoꢀN(ax)(N3)
,
N(eq)ꢀCoꢀN(ax)(py) and N(ax)(N3)ꢀCoꢀN(ax)(py) bond an-
gles. N1ꢀN2 and N3ꢀN4 equatorial bond distances are
shorter than N2ꢀN3 and N1ꢀN4 bonds. This allows the
location of the oxime bridge hydrogen. The butterfly
bending angle [h] for 4b is higher (3.1°) than in 8b
(1.2°).
trans Effect: The trans effect is seen if we compare
the CoꢀN5 bond distance in 4b vs 1b, 8b vs 5b and also
4a vs 1a [14,16]. The bond is longer in N3 complexes
(4b, 8b and 4a) as compared to their chloro analogs (1b,
5b and 1a) (Table 8).
cis Effect: The cis effect is seen if we hold X and B
and change the equatorial plane. A comparison of
CoꢀN5 in 1a vs 1b, 1c and 5b, shows that the bond is

90
B.D. Gupta et al. / Journal of Organometallic Chemistry 629 (2001) 83–92
Table 7
Crystal data and structure refinement for 4b and 8b
4b
8b
Empirical formula
Formula weight
Temperature (K)
C23H23CoN8O4
534.42
293(2)
C
560.46
293(2)
25H25CoN8O4
,
Wavelength (A)
0.7107
Monoclinic
C2/c
0.7107
Orthorhombic
Pna21
Crystal system
Space group
Unit cell dimensions
,
a (A)
14.5786(9)
9.2287(10)
18.2450(5)
90
104.5505(6)
90
2376.0(3)
4
1.494
18.5677(7)
10.1602(11)
13.7534(7)
90
90
90
2594.6(3)
4
1.435
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
V (A )
3
,
Z
Dcalc (Mg m−3
)
Absorption coefficient
(mm−1
F(000)
0.770
0.709
)
1104
1160
Crystal size (mm)
Index ranges
0.36×0.24×0.20
−175h517, −115k511, −225l521
0.26×0.20×0.06
−225h522, −125k512, −165l516
Completeness to
99.6
99.9
theta=26.00° (%)
Absorption correction
(1998)
Empirical, R.A. Jacobson, Molecular Structure Corp. Empirical, R.A. Jacobson, Molecular Structure Corp.
Max/min transmission
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I\2|(I)]
R indices (all data)
1.00, 0.89
4663/0/335
1.183
R1=0.0526, wR2=0.1210
R1=0.0775, wR2=0.1350
1.00, 0.63
4815/1/345
1.153
R1=0.0713, wR2=0.1741
R1=0.0844, wR2=0.1834
longer in 1b, 1c and 5b. Similarly, the CoꢀN5 bond is
longer in 4b and 8b as compared to 4a.
4. Experimental
Effect of one dioxime wing on the other wing: N1ꢀC1/
N2-C2 in 1b and 5b is shorter than in 1c. Similarly, it is
shorter in 4a and 4b as compared to the distance in 8b.
The N3ꢀC20/N4ꢀC21 distance is shorter in 1a as com-
pared to 1b. These changes are attributed to the effect
of one dioxime wing on the other wing. These results
support the 13C-NMR (CꢁN) values as discussed above.
XCo(dmgH)2Py (1a–4a) (X=Cl, Br, NO2, N3),
XCo(chgH)2Py (5a and 8a) (X=Cl, N3), ClCo(dpgH)2-
Py (1c), ClCo(dmgH)(dpgH)Py (1b) and ClCo(chgH)-
Table 8
,
Selected bond lengths (A)
a
4b
8b a
1b b
5b b
O1···HO4 1.410(5)
1.355(4)
1.140(5)
1.102(4)
1.400(5)
1.873(5)
1.893(5)
1.920(5)
1.919(5)
1.982(4)
2.017(4)
1.284(8)
1.316(8)
1.302(8)
1.272(9)
3. Conclusions
O4ꢀHO4
O2ꢀHO2
1.100(5)
1.170(6)
O3···HO2 1.330(5)
The results described in this paper confirm the previ-
ous findings on the dmgH complexes [9] and allow us to
conclude further that the influence of the group X in
trans-XCo(L2)Py on the spectroscopic properties of
these derivatives can be easily understood as derived
from the changes on the electronic density of the
Co(L2)py+ moiety. A new series of cobaloximes with
mixed dioximes along with two crystals structures have
been described. The spectroscopic data show that one
wing of the dioxime ligand affects the other wing of the
dioxime ligand. Many new correlations have been
obtained.
CoꢀN1
CoꢀN2
CoꢀN3
CoꢀN4
CoꢀN5
CoꢀN6
N1ꢀC1
N2ꢀC8
N3ꢀC20
N4ꢀC21
1.887(2)
1.890(2)
1.912(2)
1.903(2)
1.991(5)
1.963(3)
1.302(4)
1.295(4)
1.288(4)
1.290(4)
1.9655(23)
1.9765(23)
1.283(4)
1.290(4)
1.301(3)
1.312(3)
1.290(4)
1.295(4)
1.303(4)
1.299(4)
a Present study.
b From Ref. [15].

B.D. Gupta et al. / Journal of Organometallic Chemistry 629 (2001) 83–92
91
mmol in 5 ml of water) was added and the solution was
further refluxed for 2 h. At this stage, the solution
became clear. The solvent was evaporated to dryness.
The residue was dissolved in a minimum volume of
CHCl3 and the products were separated by column
chromatography. Three products were isolated [4c
(0.089 g), 8a (0.002 g), 8b (0.340 g)] (Table 1).
4.2. Separation of products: column details
The orange-red powder containing the mixture of
cobaloximes, dissolved in minimum amount of CHCl3,
was loaded on a silica gel (100–200 mesh) column
pre-eluted with CHCl3. The polarity was increased care-
fully with EtOAc. Three distinct bands were visible
with 20% EtOAc. The first band corresponding to the
dpgH complex came out completely with 20% EtOAc.
The mixed ligand complex came out with 40% EtOAc
mixture and the dmgH complex finally came out with
60% EtOAc mixture. Any deviation in these ratios may
give contaminated products.
Fig. 2. ORTEP plot of structure N3Co(dmgH)(dpgH)Py (4b).
Note: The Rf value for certain products is same as
that of chlorocobaloxime and therefore one should be
careful in the column separation. Any impurity of
chlorocobaloxime in the product can be detected only
in the 13C-NMR spectra.
Fig. 3. ORTEP plot of structure N3Co(chgH)(dpgH)Py (8b).
(dpgH)Py (5b) are known compounds and were synthe-
sized either by the literature procedures or by the
methods detailed earlier by us [5c] [9] [10] [12] [13]. The
yields vary between 55 and 83%. All other mixed
dioxime complexes (2b–4b and 6b–8b) were synthesized
by the substitution of Cl by the other inorganic groups.
Three products were formed in each reaction (Table 1).
The other complexes XCo(chgH)2Py (6a and 7a) (X=
Br, NO2) and XCo(dpgH)2Py (2c–4c) (X=Br, NO2,
N3) were synthesized by the substitution reaction. The
complexes XCo(L)2Py (2a–4a, 6a–8a and 2c–4c) were
also obtained as side products during the preparation
of mixed dioxime complexes.
5. Supplementary material
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC nos. 152943 and 152944 for com-
pounds 4b and 8b, respectively. Copies of this informa-
tion may be obtained free of charge from The Director,
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK
(Fax:
+44-1223-336033;
e-mail:
deposit@ccdc.
com.ac.uk or www: http://www.ccdc.cam.ac.uk).
1H- and 13C-NMR spectra were recorded on a JEOL
JNM LA 400 PT NMR Spectrometer (at 400 MHz for
1H and at 100 MHz for 13C) in CDCl3 solution with
TMS as internal standard. UV–vis spectra were
recorded on a Shimadzu 160A spectrometer. The ele-
mental analysis was carried out at the Regional Sophis-
ticated Instrumentation Center, Lucknow. The crystal
structures were analyzed using an Enraf–Nonius CAD-
4 diffractometer.
Acknowledgements
We thank the Department of Science and Technol-
ogy (DST), New Delhi, for funding this project (project
no. SP/S1/F20/99).
References
[1] (a) N. Bresciani-Pahor, M. Forcolin, L.G. Marzilli, L. Randac-
cio, M.F. Summers, P.J. Toscano, Coord. Chem. Rev. 63 (1985)
1 (and references therein);
4.1. General procedure
(b) N. Bresciani-Pahor, E. Zangrando, L.G. Marzilli, Chem. Soc.
Rev. 18 (1989) 225;
(c) L. Randaccio, Comments Inorg. Chem. 21 (1999) 327;
(d) B.T. Golding, J. R. Neth. Chem. Soc. 106 (1987) 342.
A suspension of ClCo(chgH)(dpgH)Py (0.700 g,
1.261 mmol) in methanol (80 ml) was heated to reflux.
To this, an aqueous solution of NaN3 (0.098 g, 1.514

92
B.D. Gupta et al. / Journal of Organometallic Chemistry 629 (2001) 83–92
[6] (a) D. Dodd, M.D. Johnson, B.L. Lockman, J. Am. Chem. Soc.
[2] (a) N. Bresciani-Pahor, E. Zangrando, L. Randaccio, J.P. Char-
land, L.G. Marzilli, Organometallics 5 (1986) 1938;
(b) K.L. Brown, J.M. Haskimi, D.M. Nuss, Y.D. Montejno,
D.W. Jacobson, Inorg. Chem. 23 (1984) 1463;
99 (1977) 3664;
(b) C. Lopez, S. Alvaez, M. Font-Bardia, X. Solans, J.
Organomet. Chem. 414 (1991) 245;
(c) L.G. Marzilli, F. Bayo, M.F. Summers, L.B. Thomas, E.
Zangrando, N. Bresciani-Pahor, L. Randaccio, J. Am. Chem.
Soc. 109 (1987) 6045.
(c) C. Lopez, S. Alvarez, X. Solans, M. Font-Bardia, Polyhedron
11 (1992) 1637;
(d) C. Lopez, S. Alvarez, M. Aguilo, X. Solans, M. Font-Altaba,
Inorg. Chim. Acta 127 (1987) 153;
(e) C. Lopez, S. Alvarez, X. Solans, M. Font-Altaba, Inorg.
Chem. 25 (1986) 2962;
(f) G.N. Schrauzer, L.P. Lee, J.W. Sibert, J. Am. Chem. Soc. 92
(1970) 2997.
[3] (a) D. Datta, G.T. Sharma, J. Chem. Soc. Dalton Trans. (1989)
115;
(b) N. Bresciani-Pahor, S. Geremia, C. Lopez, L. Randaccio, E.
Zangrando, Inorg. Chem. 29 (1990) 1043;
(c) K.L. Brown, S. Satyanarayana, J. Am. Chem. Soc. 114 (1992)
5674;
(d) L. Randaccio, S. Geremia, E. Zangrando, C. Ebert, Inorg.
Chem. 33 (1994) 4641;
[7] B.D. Gupta, Kushal Qanungo, J. Organomet. Chem. 543 (1997)
125.
[8] B.D. Gupta, Kushal Qanungo, T. Barclay, W. Cordes, J.
Organomet. Chem. 560 (1998) 155.
[9] J.M. Gilaberte, C. Lopez, S. Alvarez, M. Font-Bardia, X.
Solans, New J. Chem. 17 (1993) 193.
[10] (a) R.S. Stewart, L.G. Marzilli, Inorg. Chem. 16 (1977) 424;
(b) W.C. Trogler, R.S. Stewart, L.A. Epps, L.G. Marzilli, Inorg.
Chem. 13 (1974) 1564.
[11] G.N. Schrauzer, Inorg. Synth. 11 (1968) 61.
[12] H.A.O. Hill, K.G. Moralle, J. Chem. Soc. A (1969) 554.
[13] B.D. Gupta, Veena Singh, R. Yamuna, Usha Tiwari, T. Barclay,
W. Cordes, J. Organomet. Chem. 627 (2001) 80.
[14] A. Clearfield, R. Gopal, R.J. Kline, M.L. Sipski, L.O. Urban, J.
Coord. Chem. 8 (1978) 5.
[15] B.D. Gupta, Usha Tiwari, Veena Singh, R. Yamuna, unpub-
lished work.
[16] S. Geremia, R. Dreos, L. Randaccio, G. Tauzher, L. Antolini,
Inorg. Chim. Acta 216 (1994) 125.
(e) D.J.A. De Ridder, E. Zangrando, H.B. Burgi, J. Mol. Struct.
374 (1996) 63;
(f) R.S. Drago, Inorg. Chem. 34 (1995) 3543;
(g) R.S. Drago, J. Organomet. Chem. 512 (1996) 61.
[4] (a) P.J. Toscano, T.F. Swider, L.G. Marzilli, N. Bresciani-Pahor,
L. Randaccio, Inorg. Chem. 22 (1983) 3416 (and references
therein);
(b) N. Bresciani-Pahor, L. Randaccio, E. Zangrando, P.J.
Toscano, Inorg. Chim. Acta 96 (1985) 193.
[5] (a) B.D. Gupta, M. Roy, I. Das, J. Organomet. Chem. 397
(1990) 219;
(b) G.N. Schrauzer, E. Deutsch, J. Am. Chem. Soc. 91 (1969)
3341;
(c) B.D. Gupta, Kushal Qanungo, R. Yamuna, V. Vijaikanth,
Veena Singh, T. Barclay, W. Cordes, J. Organomet. Chem. 608
(2000) 106.
.