Synthesis, characterization and cis-trans influence in cobaloximes with nioxime

Article abstract of DOI:10.1016/S0022-328X(00)00380-6

A synthetic scheme leading to the (X)(Y)bis(1,2-cyclohexanedionedioximato)cobalt(III) complexes, where X = Cl, N₃, ClCH₂, CH₃, C₂H₅ and Y = PPh₃ and Py is reported. The complexes have been characterized by the usual spectroscopic techniques and have been compared with the reported analogous compounds having other dioximes as the equatorial ligands. The first crystal structure of an inorganic cobaloxime with 1,2-cyclohexanedionedioxime (Nioxime) is reported. For a range of X ligands, a clear trend between ³¹P, ¹³C, ¹H chemical shifts of the equatorial and axial ligands as well as with the Co → chgH charge transfer band has been observed.

Full text of DOI:10.1016/S0022-328X(00)00380-6

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 608 (2000) 106–114
Synthesis, characterization and cis–trans influence in cobaloximes
with nioxime
B.D. Gupta a,*, Kushal Qanungo a, R. Yamuna a, Ashutosh Pandey a, Usha Tewari a,
V. Vijaikanth a, Veena Singh a, T. Barclay b, W. Cordes b
a Department of Chemistry, I.I.T. Kanpur, UP India, Kanpur 208016, India
b Department of Chemistry and Biochemistry, Uni6ersity of Arkansas, Fayette6ille, AR, USA
Received 22 November 1999; received in revised form 2 June 2000
Abstract
A synthetic scheme leading to the (X)(Y)bis(1,2-cyclohexanedionedioximato)cobalt(III) complexes, where X=Cl, N3, ClCH2,
CH3, C2H5 and Y=PPh3 and Py is reported. The complexes have been characterized by the usual spectroscopic techniques and
have been compared with the reported analogous compounds having other dioximes as the equatorial ligands. The first crystal
structure of an inorganic cobaloxime with 1,2-cyclohexanedionedioxime (Nioxime) is reported. For a range of X ligands, a clear
1
trend between 31P, 13C, H chemical shifts of the equatorial and axial ligands as well as with the Co“chgH charge transfer band
has been observed. © 2000 Elsevier Science S.A. All rights reserved.
Keywords: Cis–trans influence; Cobaloximes; Nioxime
monitored spectroscopically, or the structural changes
are followed from their X-ray structures. UV–vis
1. Introduction
[4,23,24], IR [25–27], 1H [28–33], 13C [34–40], 31P
[41,42] and 19F [43–45] spectroscopy have been used as
probes for such studies in cobaloximes. The CoꢀC bond
dissociation energy in organocobaloximes is found to
depend on Y [2] and the dissociation constant of Y
depends on X [2]. The metal–ligand axial bond and the
butterfly bending1 of the dioxime ligands is found to
depend on the steric and electronic properties of the
axial ligands [3]. Several attempts have been made to
correlate the wealth of information available
[23,31,39,46–53].
Most of these studies have involved dmgH as the
dioxime ligand in organocobaloximes. The studies in-
volving other oximes with varying steric and electronic
properties such as gH [54,55], chgH [56,57] and dpgH
[4,58–60] have been few. Recently we have shown that
the cis influence of the dioxime ligand in alkylcoba-
loximes varies dpgH\chgH\dmgH [61] and the same
order is conserved in organobridged [46] as well as in
ligand bridged dicobaloximes [62]. In a separate study,
Cobaloximes, (X)CoIII (dmgH)2(Y), have extensively
been used to mimic the vitamin B12 coenzyme [1–3].
Apart from the structural similarities, the theoretical
calculations have shown a close resemblance between
the m.o.’s of the cobalamins and cobaloximes [4]. This
is reflected in their catalytic abilities for many impor-
tant organic transformations [5–20].
Cis and trans influences, originally defined in square
planar platinum(II) systems, described the bond weak-
ening effect one ligand had on others [21]. The study
now includes investigations of all possible steric and
electronic changes detectable in the cis or trans ligands.
Cobalt(III) complexes [22] and particularly cobaloximes
[2,3], due to their ready availability, are the preferred
systems for cis and trans influence studies in octahedral
systems. Usually either the axial ligand X or the basal
group Y is varied systematically and the changes in the
cis equatorial dioxime ligand or the trans axial ligand is
* Corresponding author: Tel.: +91-512-597730; fax: +91-512-
597436.
E-mail address: bdg@iitk.ac.in (B.D. Gupta).
1 For definition and other details see [3].
0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(00)00380-6

B.D. Gupta et al. / Journal of Organometallic Chemistry 608 (2000) 106–114
107
Table 1
% yields and analytical data for XCo(chgH)2Y
Compound number
Y
X
%Yield
Rf (EtOAc)
C
H
N
1a
1b
2a
2b
3a
3b
4a
4b
5a
5b
PPh3
Py
PPh3
Py
PPh3
Py
PPh3
Py
Cl
Cl
N3
N3
ClCH2
ClCH2
Me
Me
Et
69
73
79
85
47
70
33
69
35
73
0.8
0.8
0.7
0.7
0.9
0.6
0.9
0.7
0.8
0.8
56.2 (56.4)
44.9 (44.8)
55.7 (55.8)
44.1 (44.2)
57.0 (57.0)
46.0 (46.0)
60.2 (60.2)
49.6 (49.7)
60.8 (60.8)
50.6 (50.8)
5.3 (5.2)
5.00 (5.1)
5.2 (5.1)
4.9 (5.0)
5.5 (5.4)
5.3 (5.3)
5.8 (5.9)
6.0 (6.0)
6.1 (6.0)
6.3 (6.3)
8.7 (8.8)
15.4 (15.4)
15.1 (15.2)
24.3 (24.2)
8.7 (8.6)
14.8 (14.9)
9.1 (9.1)
16.0 (16.1)
8.8 (8.9)
15.2 (15.3)
PPh3
Py
Et
we have also reported the trans influence of the axial
ligand [63].
stoichiometric quantity of triphenylphosphine was used
[ClCo(chgH)2(H2O)–PPh3, 1.0/0.60] to avoid the for-
mation of the double complex salt [Co(chgH)2Cl2]-
[Co(chgH)2(PPh3)2] [65].
Azido complexes were synthesized directly from
cobalt acetate and sodium azide (method 2a)(Eq. (3)) or
indirectly by substitution of chloride by azide (method
2b)(Eq. (4)) [66].
All these studies have involved an alkyl s donor
group as one of the axial ligands. In this paper, we
extend our studies to inorganic cobaloximes with s and
p donor ligands. We also address the question of
whether the dioxime moiety has any effect on the
butterfly bending and on the cis and trans influence
order of the axial ligands.
Co(CH3COO)2·4H2O+2chgH2+NaN3+2Y+0.25O2
“N3Co(chgH)2Y+Y·CH3COOH+CH3COONa
2. Results and discussion
+0.5H2O(+4H2O)
(3)
(4)
2.1. Synthesis
ClCo(chgH)2Y+NaN3“N3Co(chgH)2Y+NaCl
The synthesis of XCo(chgH)2Y (X=Cl, N3, ClCH2,
Me, Et) Y=PPh3 (1a–5a); Y=Py (1b–5b) complexes
was accomplished following the well established proce-
dures for the gH [55], dmgH [64], and dpgH [60b,c]
complexes.
Organocobaloximes were prepared essentially by the
same method reported earlier by us [61]. Yields (%), Rf
values (in ethylacetate) and analytical data are tabu-
lated in Table 1.
Refluxing a ethanolic solution of cobalt(II) chloride,
chgH2 and an appropriate base (method 1a) followed
by vigorous aeration yields the desired ClCo(chgH)2Y
complex (Eq. (1)).
2.2. Spectroscopy
The spectroscopic characteristics of cobaloximes with
dmgH as the equatorial ligand show a systematic varia-
tion with X. It is anticipated that a more comprehen-
sive spectroscopic and structural study of a large
number of cobaloximes (having different dioximes) with
various X ligands (having a range of s and p donor/ac-
ceptor properties) would enable a more rigorous treat-
ment of the statistical data with a greater degree of
confidence. The present study, therefore, gains impor-
tance as it indicates that the cis and trans influencing
order of the axial ligand X is independent of the
equatorial ligand in cobaloximes. The following discus-
sion of the trends in the spectroscopic properties illus-
trates this point.
CoCl2(6H2O)+2chgH2+2Y+0.25O2
“ClCo(chgH)2Y+Y·HCl+0.5H2O (+6H2O)
(1)
One equivalent of an inorganic base (NaOH or
KOH) can replace an equivalent amount of the appro-
priate organic base (Py) (methods 1a,b and 2a) without
compromising the yield [25].
One can achieve the following reaction simply by
adding the appropriate base to the aquo complex,
(method 1b) (Eq. (2)) formed in situ, from cobalt(II)
chloride and chgH2 in acetone.
XCo(chgH)2(H2O)+Y“XCo(chgH)2Y+H2O
(2)
The least square method [67] and Microsoft Excel for
Windows 95 version 7.0 have been used for the correla-
tion analysis.
For the synthesis of cobaloximes with Y=PPh3 by a
ligand exchange reaction (method 1b), less than the

108
B.D. Gupta et al. / Journal of Organometallic Chemistry 608 (2000) 106–114
Table 2
1H shifts and Co“dioxH CT band umax in XCo(chgH)2Y a,b
Number
Coꢀ(CH2)ꢀ
Me
Pya
Pyg
Pyb
DPya
DPyg
DPyb
umax (log m)
1a
1b
2a
2b
3a
3b
4a
4b c
5a
246 (4.2)
258 (4.3)
246 (4.3)
253 (4.2)
248 (4.3)
249 (4.4)
246 (4.2)
247 (4.3)
249 (4.4)
246 (4.3)
8.26
8.32
8.58
8.62
8.60
7.72
7.74
7.76
7.73
7.72
7.25
7.26
7.74
7.33
7.32
−0.31
−0.25
0.01
0.29
0.31
0.33
0.30
0.29
0.20
0.21
0.30
0.28
0.27
3.85
3.78
0.86
0.85
1.93
1.77
0.05
0.37
0.37
c
5b
0.03
a 1H of free Py: h=8.57, i=7.05 and k=7.43.
b All compounds show four sets of multiplet in the range of 2.2–2.5, 3.0–3.1, 1.5–1.6 and 1.7–1.8 due to cyclohexane ring protons.
c Values taken from [61].
Table 3
(a) 31P and 13C shifts in 1–5a,b and (b)13C shifts of Pyridine in 1b–5b
Compound number
31PPh3
25.32
23.75
20.50
19.81
20.36
D
31P
CꢁN
C a
C%
C1
C2
1a
1b
2a
2b
3a
3b
30.52
28.95
25.70
25.01
25.56
153.45
153.62
152.65
153.12
150.53
151.12
149.24
150.04
149.06
150.07
26.07
26.12
25.89
25.99
25.41
25.39
25.15
25.05
25.01
25.08
21.04
23.33
21.18
21.45
21.23
21.45
21.37
21.44
21.29
21.60
65.23
4a
4b a
5a
11.56
26.01
15.08
15.82
5b a
Compound number
13C Pya
D
13CPya
13CPyb
D
13Cpyb
13C Pyg
D
13CPyg
1b
2b
151.09
151.30
150.28
149.89
149.89
1.27
1.48
0.46
0.07
0.07
125.66
125.7
125.40
125.09
125.02
1.93
1.97
1.67
1.36
1.29
138.96
138.80
137.91
137.38
137.25
3.07
2.91
2.02
1.49
1.36
3b
4b a
5b a
a 13C shift of Free Py: h=149.82, i=123.73 and k=135.89.
2.3.2. 31P Chemical shifts
2.3. Cis and trans influence of X
2.3.1. UV–6is spectra
All the cobaloximes exhibit an intense Co“dioxH
CT band at :240 nm (Table 2). For the cobaloximes
(1b–5b) the umax values fall in the following order,
Cl\N3\CH2Cl\Me:Et. A similar trend was ob-
served earlier for the dmgH complexes for Y=3,5-lu-
tidine and 2,6-dimethylpyrazine [24].
Furthermore, the umax values in (1b–5b) show a clear
linear trend (discussed later) with the 13C of
CꢁN(oximinic) and the co-ordination shifts of 13C of Pyg
and 1H of Pya. However, for cobaloximes with
triphenylphosphine (1a–5a) no clear correlation
emerges.
Phosphines and phosphites co-ordinated to
cobalt(III) display a broad 31P peak due to a cobalt–
phosphorus Fermi-contact interaction [42]. The 31P res-
onance of PPh3 (−5.2l) shifts downfield to 20–25l
when co-ordinated to the cobaloxime moiety. This is
due to a large decrease in the electron density on the
phosphorus (P“Co(dioxH)2). In case of substituted
phosphines, this co-ordination shift2, has been found to
depend on the phosphine cone angle [42]. Our results
show that the nature of the trans ligand X also influ-
ences the D31P and it follows the order Cl\N3\
2 D31P=31Plcomplex
− .
31Plfree

B.D. Gupta et al. / Journal of Organometallic Chemistry 608 (2000) 106–114
109
CH2Cl\Me:Et (Table 3a). A similar trend was ob-
l13C(CꢁN)
=2.47D13CPya+149.94 (r2=0.95, e.s.d.=0.42 ppm)
good correlation is observed when 13C of
CꢁN(oximinic) in (1a–5a) is compared with (1b–5b)
l13C(CꢁN) PPh3
served in the dmgH complexes with Y=Bu3P and
(Bu3O)3P [42]. This similarity in the trend suggests that
the trans influence order of X is independent of the
dioxime moiety. The electronic cis influence of X in
(1a–5a)3 is apparent from the following trends. D31P
shows a linear trend with 13C resonance of the equato-
rial CꢁN(oximinic) and C2 carbons of the cyclohexane
ring4.
A
=1.18l13C(CꢁN)Py
−27.22 (r2=0.99, e.s.d.=0.18 ppm)
D31P=1.19 l13C(CꢁN)
1
2.3.4. H Chemical shifts
−152.04 (r2=0.94, e.s.d.=0.74 ppm)
The coordination shift of pyridine protons follow the
order D1HPyaBD1HPybBD1HPyg (Table 2) and shows
that there is a increasing order of downfield shift from
a to g. However, only a protons show a clear trend in
D31P=5.05 l13C(C2)
−101.70 (r2=0.91, e.s.d.=0.86 ppm)
However, no correlation is observed between D31P and
the umax of Co“dioxH (MLCT).
D1H. The trans influence of the X group on Ha can be
1
followed by the co-ordination shift6 of the ligating
pyridine and it follows Cl\N3\CH2Cl\Me:Et
(Table 2). This order is similar to the one observed
earlier for umax of Co“dioxH (MLCT), 31P of PPh3,
2.3.3. 13C Chemical shifts
The 13C resonance of pyridine on co-ordination to
the cobaloxime moiety shifts downfield by a few ppm
and this co-ordination shift5 follows the order
D13CPyg\D13CPyb\D13CPya (Table 3b).
13C of Pyg and of CꢁN(oximinic)
.
The D1HPya has a linear variation with umax of
Co“dioxH (MLCT) and 13C of 13CꢁN(oximinic). The
least square equations obtained in the correlation are
The cis and trans influence of the ligand X in (1b–5b)
can be followed by D13C values of pyridine and 13C
resonance of CꢁN(oximinic). It follows the order Cl\
N3\CH2Cl\Me:Et (Table 3a,b). The same trend
was observed in D31P and umax of Co“dioxH (MLCT)
as mentioned earlier. It is also noticed that lCꢁN in
(1a–5a) show an upfield shift as compared to (1b–5b)
indicating a higher charge density on CꢁN in the for-
mer (Table 3a).
umax= −27.37(630)D1HPya
+248.03 (114) (r2=0.91, e.s.d.=2.16 nm)
l13C(CꢁN)=2.47(31)D1HPya
+149.94 (28)
(r2=0.96, e.s.d.=0.42 ppm)
The co-ordination shift of the g carbon of pyridine,
D13CPyg, with variation in X correlates well with the
umax of Co“dioxH (MLCT) as well as with the 13C of
CꢁN(oximinic) indicating a similar origin of the cis influ-
encing ability of X.
Similar trends are observed for gH, dmgH and dpgH
cobaloximes [24, 60c]. However, it is not possible to do
correlation studies in complexes (1a–5a) because of the
difficulty in assigning all the protons.
2.4. Cis and trans influence of the equatorial dioximes
umax=5.94D13CPyg
+237.7 (r2=0.91, e.s.d.=1.73 nm)
In view of our recent study on the cis influence in
organocobaloximes [46,61–63], the present data allows
us to extend our earlier conclusions further. The extent
of electron density on the Co(dioxH)2 chelate ring for
different dioximes (X and Y held constant) can be
understood by comparing the 13C chemical shifts of
(CꢁN) of the equatorial dioxime, for example, for X=
Me, Et or Cl and Y=Py it follows the order gHB
dmgHBchgHBdpgH (Table 4).
l13C(CꢁN)
=2.13D13CPyg+146.98 (r2=0.99, e.s.d=0.17 ppm)
The co-ordination shift of b as well as a carbon of
pyridine also show a linear trend with the 13C of
CꢁN(oximinic)
.
l13C(CꢁN)
The cis influence of the dioximes on the axial ligands
can also be followed by the co-ordination shifts of the
=5.18D13CPyb+143.07 (r2=0.93, e.s.d.=0.51 ppm)
1
a protons of pyridine (D1HPya) and the H resonance
of the axial group (Table 4). For DPya the order is
dmgH:chgHBgHBdpgH (this order is based on the
3 The steric bulk of X is almost similar.
4 For numbering of carbons in the cyclohexane rings see Ref. [61].
6 D1H=1Hlcomplex−1Hlfree
.
5 D13C=13Clcomplex
− .
13Clfree

110
B.D. Gupta et al. / Journal of Organometallic Chemistry 608 (2000) 106–114
1
values for X=Cl, Me, Et)7 and the cis influence order
on the axial X group is dmgH:chgHBgHBdpgH
(this order is based on the (Ca) values for X=Me, Et)
The study shows that the cis influence of the equato-
rial oximes on the axial alkyl group is inter-related as
evinced by the near ideal value of r2 i.e. there is a good
correlation of chgH complexes with other equatorial
oxime complexes (based on H chemical shifts of axial
group).
l1HchgH=1.00(0) l1HgH
−0.16(0)(r2=0.99, e.s.d.=0.00 ppm)
l1HchgH=0.98(1) l1HdmgH
+0.03(1) (r2=0.99, e.s.d.=0.01 ppm)
l1HchgH=0.90(6) l1HdpgH
−0.39(9) (r2=0.99, e.s.d.=0.06 ppm)
Table 4
1H shifts of Pya, X and 13C shifts of CꢁN in different glyoximes
X
dioxH
GH
dmgH
chgH
dpgH
2.4.1. X-ray crystal structure
Dark brown crystals of ClCo(chgH)2PPh3 (1a) was
grown from methanol and was subjected to X-ray
crystallography. The ORTEP plot of 1a is shown in Fig.
1. Pertinent crystal data and refinement parameters and
interatomic distances are compiled in Tables 5 and 6.
Both cyclohexane rings have disorder in the two
outer carbon positions. It was modelled with split car-
bons, which were refined isotropically. The C3ꢀC4 dis-
order is 50–50 in occupancy in the model, and seems to
indicate a disorder with both C’s either above or below
the general plane of the ring. The C9ꢀC10 disorder was
60–40 occupancy, and seems to indicate a twist disor-
der with the bonded pairs each having one atom above
and one atom below. This arrangement appears to
model the disorder fairly well but some of the bond
lengths and angles involved with these atoms suggest
that the real situation is perhaps not quite this simple.
The H atoms for the OH groups were located on
difference maps and were restrained to those difference
map positions.
a
Cl
1H
Pya
DPya
8.28
8.25
−0.32
152.59
8.26 b
−0.31
153.62
8.62 c
0.05
153.69
−0.29
13C CꢁN
1H
140.56 e
N3
Pya
DPya
8.32 b
−0.25
153.12
8.58 b
0.01
13C CꢁN
152.11
ClCH2
1H
Pya
DPya
CH2
3.78
151.12
13C CꢁN
1H
Me
Et
Pya
DPya
CH3
8.67 a
0.10
8.59
0.02
0.82
149.89
8.62 b
0.05
0.85
9.00 a
0.43
1.44
1.02
13C C=N 138.10 e
150.04
150.90
1H
Pya
8.67 a
0.10
1.9
8.56 d
0.01
1.74
0.35
149.92
8.6 c
0.03
1.74
0.37
8.87 d
0.3
2.35
0.81
150.85
D Pya
CH2
CH3
0.53
13C C=N 138.81 e
150.07
a Ref. [55].
b This study.
A comparative study (Table 7) of the bond angles
and bond lengths in compound ClCo(chgH)2(PPh3) (1a)
with that of ClCo(dmgH)2(PPh3) [68], the closest struc-
ture for comparison, shows that the CoꢀP and CoꢀCl
bond length does not change with the change in the
equatorial ligand. The cobalt atom in compound 1a is
c Ref. [59].
d Ref. [61].
e From our lab, unpublished work.
-1
,
0.0742(19) A out of the mean plane of the four nitrogen
atoms that is nearly the same as in the dmgH complex
,
(0.05 A). The bulk of the chgH wings manifests itself in
the increased h value [11.3(3)°] for the chgH complex as
compared to the dmgH complex [6°]. A similar increase
is observed when the gH complex is compared with the
dmgH complex (Table 7) confirming that the increase
in equatorial bulk leads to an increase in h value.
3. Conclusions
The study highlights that a change in X leads to a
systematic variation in the spectroscopic properties in
the dioxime ligands and in the axial ligand Y and the
trans influence order of X is independent of the dioxime
moiety. A systematic change in the steric and electronic
Fig. 1. ORTEP plot of structure ClCo(chgH)2PPh3 (1a).
7 Others can not be compared since the data for all the four sets of
dioximes is not available.

B.D. Gupta et al. / Journal of Organometallic Chemistry 608 (2000) 106–114
111
Table 5
Table 6
,
Crystal data collection and refinement parameters
Interatomic distances (A) and angles (°)
Formula
C30H33ClCoN4O4P
638.97
0.30×0.34×0.36
Brown
On glass fiber with silicone glue
11.058(2)
15.310(2)
17.3122(18)
92.465(12)
2928.1(7)
25
20–21
1.45
P21/n
4
CoꢀCl
CoꢀN1
CoꢀN3
PꢀC13
PꢀC30
O1ꢀHo1
O3ꢀN3
O4ꢀN4
N2ꢀC12
N4ꢀC6
2.2771(13)
1.894(3)
1.883(4)
1.836(5)
1.828(4)
1.188(3)
1.349(4)
1.344(5)
1.291(6)
1.294(6)
1.443(6)
1.469(14)
1.331(18)
1.576(13)
1.497(7)
1.567(11)
1.522(13)
1.521(10)
1.497(6)
1.392(7)
1.380(11)
1.379(8)
1.382(7)
1.374(10)
1.394(7)
1.380(7)
1.366(9)
1.386(7)
CoꢀP
CoꢀN2
CoꢀN4
PꢀC19
O1ꢀN1
O2ꢀN2
O3ꢀHo3
N1ꢀC1
N3ꢀC7
2.3222(13)
1.896(3)
1.892(3)
1.829(4)
1.351(4)
1.336(4)
1.172(3)
1.299(6)
1.292(6)
1.482(7)
1.532(13)
1.338(18)
1.469(14)
1.504(6)
1.458(6)
1.474(15)
1.51(2)
1.542(15)
1.404(8)
1.379(8)
1.370(11)
1.390(6)
1.391(7)
1.347(10)
1.384(7)
1.371(10)
1.395(7)
Formula weight
Crystal size (mm)
Cystal color
Crystal mount
,
a (A)
,
b (A)
,
c (A)
i (°)
3
,
V (A )
C1ꢀC2
Cell detn, reflections
C1ꢀC6
C2ꢀC3x
C3xꢀC4x
C4xꢀC5
C5ꢀC6
Cell detn, 2q range (°)
C2ꢀC3y
C3yꢀC4y
C4yꢀC5
C7ꢀC8
Dcalc (g cm−3
Space group
Z
)
C7ꢀC12
C8ꢀC9y
C9yꢀC10y
C10yꢀC11
C13ꢀC14
C14ꢀC15
C16ꢀC17
C19ꢀC20
C20ꢀC21
C22ꢀC23
C25ꢀC26
C26ꢀC27
C28ꢀC29
F(000)
Radiation
1330.6
C8ꢀC9x
C9xꢀC10x
C10xꢀC11
C11ꢀC12
C13ꢀC18
C15ꢀC16
C17ꢀC18
C19ꢀC24
C21ꢀC22
C23ꢀC24
C25ꢀC30
C27ꢀC28
C29ꢀC30
Mo–Ka, graphite monochromated
0.7107
293
,
u (A)
Temperature (K)
Linear absorbtion
coefficient (mm−1
Diffractometer
Scan technique
Scan width (°)
2q range (°)
0.77
)
Enraf–Nonius CAD-4
q–2q
1.0+0.35 tan q
4–50
h,k,l ranges
−13, 13; 0, 18; 0, 20
Standard reflection indices 1, 1, 3; 4, 0, 6; −4, 1, 6
Drift of stds (%)
Absorption correction
Absorption range
Reflections measured
Unique reflections
R for merge
Reflections in refinement
[I\1.0s(I)]
Solution method
Parameters refined
R(F), Rw(F)
0.5
Analytical
0.75–0.82
5313
5135
0.022
ClꢀCoꢀP
ClꢀCoꢀN2
ClꢀCoꢀN4
PꢀCoꢀN2
177.80(5)
87.14(11)
87.84(11)
92.42(11)
92.60(11)
176.01(15)
81.78(15)
97.87(15)
111.83(15)
103.7(2)
106.3(2)
101.9(3)
115.5(3)
122.8(3)
121.3(3)
116.3(3)
122.6(3)
121.3(3)
113.6(4)
111.5(6)
124.5(10)
123.7(11)
111.7(6)
113.3(4)
122.3(4)
112.8(4)
110.0(5)
110.9(7)
106.9(7)
112.2(5)
113.6(4)
121.3(4)
120.3(4)
120.3(5)
119.7(5)
ClꢀCoꢀN
ClꢀCoꢀN3
PꢀCoꢀN1
PꢀCoꢀN3
N1ꢀCoꢀN2
N1ꢀCoꢀN4
N2ꢀCoꢀN4
CoꢀPꢀC13
188.20(11)
87.82(12)
89.73(11)
94.25(12)
98.37(15)
81.64(15)
174.98(15)
117.07(16)
113.41(14)
103.4(2)
107.4(3)
123.5(3)
120.8(4)
115.5(3)
124.2(3)
119.4(4)
115.9(3)
124.2(4)
122.3(4)
111.2(7)
126.1(11)
121.5(10)
110.8(6)
124.4(4)
125.3(4)
121.9(4)
114.4(6)
110.4(11)
114.5(11)
110.5(6)
125.0(4)
120.7(4)
118.6(4)
120.2(6)
121.2(6)
PꢀCoꢀN4
3627
N1ꢀCoꢀN3
N2ꢀCoꢀN3
N3ꢀCoꢀN4
CoꢀPꢀC19
Direct methods
367
0.052, 0.057
0.041
1.18
0.03
0.00
0.61(9)
CoꢀPꢀC30
C13ꢀPꢀC19
C19ꢀPꢀC30
N3ꢀO3ꢀHo3
CoꢀN1ꢀC1
CoꢀN2ꢀO2
O2ꢀN2ꢀC12
CoꢀN3ꢀC7
CoꢀN4ꢀO4
O4ꢀN4ꢀC6
N1ꢀC1ꢀC6
C1ꢀC2ꢀC3x
C2ꢀC3xꢀC4x
C3xꢀC4xꢀC5
C4xꢀC5ꢀC6
N4ꢀC6ꢀC1
C1ꢀC6ꢀC5
N3ꢀC7ꢀC12
C7ꢀC8ꢀC9x
C8ꢀC9xꢀC10x
C9xꢀC10xꢀC11
C10xꢀC11ꢀC12
N2ꢀC12ꢀC7
C7ꢀC12ꢀC11
PꢀC13ꢀC18
C13ꢀC14ꢀC15
C15ꢀC16ꢀC17
C13ꢀPꢀC30
N1ꢀO1ꢀHo1
CoꢀN1ꢀO1
O1ꢀN1ꢀC1
CoꢀN2ꢀC12
CoꢀN3ꢀO3
O3ꢀN3ꢀC7
CoꢀN4ꢀC6
N1ꢀC1ꢀC2
C2ꢀC1ꢀC6
C1ꢀC2ꢀC3y
C2ꢀC3yꢀC4y
C3yꢀC4yꢀC5
C4yꢀC5ꢀC6
N4ꢀC6ꢀC5
N3ꢀC7ꢀC8
C8ꢀC7ꢀC12
C7ꢀC8ꢀC9y
C8ꢀC9yꢀC10y
C9yꢀC10yꢀC11
C10yꢀC11ꢀC12
N2ꢀC12ꢀC11
PꢀC13ꢀC14
C14ꢀC13ꢀC18
C14ꢀC15ꢀC16
C16ꢀC17ꢀC18
R for I\3.0|(I)
Goodness-of-fit
p, w−1=[2(I)+pI2]/4F2
Largest D
Extinction correction b
Final difference map,
−0.42(8), +0.38(8)
−3
,
(e A)
Programs
NRC386 (PC version of NRCVAX) a
International Tables for
Crystallography, vol 4
Scattering factors
,
H atom treatment
Idealized (CꢀH=0.95 A)
a
NRCVAX — An Interactive Program System for Structure Analy-
sis, E.J. Gabe, Y. Lepage, J.P. Charland, F.L. Lee, and P.S. White, J.
Appl. Cryst. 22, 383 (1989).
b Larson, A.C. Crystallographic Computing, Munksgaard Copen-
hagen 293 (1970).
properties of the dioxime moiety also manifests its cis
influence on the spectroscopic properties of the axial
ligands.
As progressively more spectroscopic, equilibrium and
structural data on the cobaloximes with various
dioximes like gH, chgH and dpgH accumulate, the

112
B.D. Gupta et al. / Journal of Organometallic Chemistry 608 (2000) 106–114
Table 6 (Continued)
95% ethanol (25 ml). The solution was allowed to cool
to r.t. and air was passed through the reaction mixture
for 6 h. The dark brown precipitate was filtered,
washed with ethanol (2×3 ml), ether (2×3 ml), dried
and purified by column chromatography.
C13ꢀC18ꢀC17
PꢀC19ꢀC24
119.9(5)
122.8(3)
120.2(5)
119.6(5)
120.0(5)
119.9(5)
119.7(5)
120.8(4)
118.4(4)
PꢀC19ꢀC20
C20ꢀC19ꢀC24
C20ꢀC21ꢀC22
C22ꢀC23ꢀC24
C26ꢀC25ꢀC30
C26ꢀC27ꢀC28
C28ꢀC29ꢀC30
PꢀC30ꢀC29
118.6(4)
118.5(4)
120.4(5)
121.2(6)
120.9(5)
120.4(5)
120.6(5)
120.8(3)
C19ꢀC20ꢀC21
C21ꢀC22ꢀC23
C19ꢀC24ꢀC23
C25ꢀC26ꢀC27
C27ꢀC28ꢀC29
PꢀC30ꢀC25
(1b) Cobalt chloride hexahydrate (0.74 g, 3.10 mmol)
was dissolved in acetone (40 ml) and 1,2 cyclohexane-
dionedioxime (1.00 g, 7.03 mmol) was added with con-
stant stirring. The reddish orange coloured mixture was
stirred for 0.5 h and pyridine (0.58 g, 7.36 mmol) was
added dropwise. The colour of the reaction mixture
immediately turned brown and then slowly changed to
green. After overnight stirring, a brown precipitate
appeared which was filtered, washed with acetone (2×
3 ml), ether (2×3 ml), dried and purified by column
chromatography.
C25ꢀC30ꢀC29
generalities of the correlations, initially observed in the
dmgH complexes, can be tested further in future.
4. Experimental
Synthesis of ClCo(chgH)2PPh3: The same procedure
was used as above but triphenylphospine was used
instead of pyridine.
Cobalt(II) chloride hexahydrate, cobalt acetate te-
trahydrate, sodium azide, 1,2 cyclohexanedionedioxime,
pyridine, triphenylphospine, methyliodide and ethylio-
dide were obtained from commercial sources (Fluka
AG) and were used as such without further purifica-
tion. All solvents were distilled prior to use.
4.2. Synthesis of N3Co(chgH)2Py
Method (2a) Pyridine (0.267 gm, 3.37 mmol) was
added with constant stirring to a refluxing solution of
cobalt(II) acetate tetrahydrate (0.39 g, 1.59 mmol), 1,2
cyclohexanedionedioxime (0.50 g, 3.51 mmol) in 95%
ethanol (25.0 ml) followed by sodium azide (0.103 g,
1.58 mmol). The solution was allowed to cool to r.t.
and air was passed through the reaction mixture for 3
h. The dark brown precipitate was filtered, washed with
ethanol (2×2.5 ml) dried and purified by column
chromatography.
1H-NMR (400 MHz, CDCl3, Int. Std. TMS), 13C-
NMR (100 MHz, CDCl3) and 31P (162.7 MHz, Ext.
Std. H3PO4) were recorded on a JOEL LA-400 Spec-
trometer. UV–vis spectra were recorded on a Shimadzu
160-A Spectrophotometer in chloroform. X-ray studies
were done on Enraf Nonius CAD-4 diffractometer at
Fayetteville, Arkansas, USA.
4.1. Synthesis of ClCo(chgH)2Py
Half the amount of pyridine or triphenylphosphine
used in the above methods (method 1a,b and 2a) can be
replaced with NaOH or KOH.
Method (1a) Pyridine (0.14 gm, 1.75 mmol) was
added with constant stirring to a refluxing solution of
cobalt(II) chloride hexahydrate (0.41 g, 1.75 mmol) and
1,2 cyclohexanedionedioxime (0.50 g, 3.51 mmol) in
(2b) Sodium azide (0.065 gm, 1.00 mmol) dissolved in
5 ml water was added to a refluxing suspension of
ClCo(chgH)2Py (0.400 g, 0.87 mmol) in 50.0 ml
methanol. The reaction mixture was further refluxed for
2 h and the volume reduced to 10 ml by rotary evapo-
rator. The red–brown solid was filtered, washed with
methanol (2×2.5 ml), pet ether (2×3.0 ml), dried and
purified by column chromatography.
Table 7
a
Comparison of bond lengths and bond angles of XCo(L)2PPh3
LꢁXꢁ
dmgH [68] chgH b
gH [55] dmgH [55,69]
Me Me
Cl
Cl
CoꢀP
CoꢀX
h
2.327(4)
2.277(4)
6
2.3222(13) 2.428(1) 2.418(1)
2.2771(13) 2.033(3) 2.026(6)
4.3. Synthesis of N3Co(chgH)2PPh3
11.3(3)
6
11
D
0.050
0.0742(19) 0.11
0.11
The same procedure as outlined above was used but
triphenylphospine was used instead of pyridine.
CoꢀNeq
N1ꢀCoꢀN1%
N1ꢀCoꢀN2
CoꢀNꢀCox
NꢀCoxꢀC%
NꢀCoxꢀCox
1.89(1)
98.7(2)
81.3(5)
1.89(3)
1.883(2) 1.891(5)
98.12(15)
81.71(15)
115.8(3)
124.7(4)
113.3(6)
97.7(1)
82.0(1)
115.8(2) 116.5(4)
122.7(6)
98.0(2)
81.7(2)
4.4. Synthesis of XCo(chgH)2Y; (X=Me, Et, ClCH2;
Y=Py, PPh3)
113.3(3) 112.7
a
These were prepared by following the procedure re-
ported earlier by us [61].
,
Bond angles (°) and bond lengths (A).
b This study.

B.D. Gupta et al. / Journal of Organometallic Chemistry 608 (2000) 106–114
113
[19] L.D. Arvanitopoulos, M.P. Gruel, H.J. Harwood, Polym. Prepr.
35 (1994) 459.
4.5. Purification by column chromatography
[20] B. Yamada, K. Toda, S. Aoki, Poylm. Bull. (Berl.) 35 (1995)
245.
[21] A. Pidcock, R.E. Richards, L.M. Venanzi, J. Chem. Soc. A
(1966) 1707
[22] J.E. Huheey, Inorganic Chemitry, third ed., Harper International
SI Edition, Harper and Row, New York, 1983, pp. 538–562.
[23] K.L. Brown, D. Lyles, M. Pencovici, R.G. Kallen, J. Am. Chem.
Soc. 97 (1975) 7338.
[24] J.M. Gilaberte, C. Lopez, S. Alvarez, M. Font-Bardia, X.
Solans, New. J. Chem. 17 (1993) 193.
[25] N. Yamazaki, Y. Hohokabe, Bull. Chem. Soc. Jpn. 44 (1971) 63.
[26] N. Yashida, A. Furusaki, M. Fujimato, J. Chem. Soc. Dalton
Trans. (1991) 453
[27] S. Nie, P.A. Marzilli, L.G. Marzilli, N.T. Yu, J. Am. Chem. Soc.
112 (1990) 608.
[28] H.A.O. Hill, K.G. Moralee, R.E. Collis, Chem. Commun. (1967)
888
[29] H.A.O. Hill, K. G. Moralee, J. Chem. Soc. Sec. A (1969) 554
[30] W.C. Trogler, R.C. Stewart, L.A. Epps, L.G. Marzilli, Inorg.
Chem. 13 (1974) 1564.
All the complexes were purified using a silica gel
column 100–200 mesh using chloroform–ethylacetate
as the eluent.
5. Supplementary material
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC no. 137919 for compound 1a.
Copies of this information may be obtained free of
charge from The Director, CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK (fax: +4-1223-336033; e-
mail: deposit@ccdc.cam.ac.uk or www: http://
www.ccdc.cam.ac.uk).
[31] L.G. Marzilli, P. Politzer, W.C. Trogler, R.C. Stewart, Inorg.
Chem. 14 (1975) 2389.
[32] H.M. McConell, J. Chem. Phys. 27 (1957) 226.
[33] (a) C. Bied-Charreton, A. Gaudemer, Tetrahedron Lett. (1969)
4189. (b) C. Bied-Charreton, B. Septe, A. Gaudemer, Org. Mag.
Res. 7 (1975) 116
[34] L.G. Marzilli, P.J. Toscano, L. Randaccio, N. Bresciani-Pahor,
M. Calligaris, J. Am. Chem. Soc. 101 (1979) 6754.
[35] R.B. Silverman, D. Dolphin, J. Am. Chem. Soc. 95 (1973) 1686.
[36] P.J. Toscano, L.G. Marzilli, Inorg. Chem. 18 (1979) 421.
[37] J.P. Charland, E. Zangrando, N. Bresciani-Pahor, L. Randaccio,
L.G. Marzilli, Inorg. Chem. 32 (1993) 4256.
[38] R.C. Stewart, L.G. Marzilli, Inorg. Chem. 16 (1977) 424.
[39] K.L. Brown, S. Satyanarayana, J. Am. Chem. Soc. 114 (1992)
5674.
[40] P.L. Gauss, A.L. Crumbliss, Inorg. Chem. 15 (1976) 2080.
[41] G.R. Tauszik, G. Pellizer, G. Costa, J. Inorg. Nucl. Chem. 37
(1975) 1532.
[42] J.A. Kargol, R.W. Crecely, J.L. Burmiester, P.J. Toscano, L.G.
Marzilli, Inorg. Chim. Acta 40 (1980) 79.
[43] D. Dodd, M.D. Johnson, C.W. Fong, J. Chem. Soc. Dalton
Trans. (1974) 58
[44] C.W. Fong, M.D. Johnson, J. Chem. Soc. Perkin Trans. 2 (1973)
986.
Acknowledgements
This work is supported by a grant from DST (SP/S1/
F20/99) and CSIR 01(1545)/98/EMR-II, New Delhi,
India. We thank Professor D. Kundu, Department of
Mathematics, IIT Kanpur for useful discussion.
References
[1] F.A. Cotton, G. Wilkinson, C.A. Murrillo, M. Bochmann, Ad-
vanced Inorganic Chemistry, sixth ed., Wiley-Interscience, New
York, 1999, p. 829.
[2] N. Bresciani-Pahor, M. Forcolin, L.G. Marzilli, L. Randaccio,
M.F. Summers, P.J. Toscano, Coord. Chem. Rev. 63 (1985) 1
and refs. therein.
[3] L. Randaccio, N. Bresciani-Pahor, E. Zangrando, L.G. Marzilli,
Chem. Soc. Rev. 18 (1989) 225.
[4] G.N. Schrauzer, L.P. Lee, J.W. Sibert, J. Am. Chem. Soc. 92
(1970) 2997.
[5] D. Dodd, M.D. Johnson, J. Organomet. Chem. 52 (1973) 1.
[6] B. Giese, Radicals in Organic Synthesis: Formation of Car-
bonꢀCarbon Bonds, Pergamon, Oxford, 1986.
[45] K.L. Brown, L.Y. Lu, Inorg. Chem. 20 (1981) 4178.
[46] B.D. Gupta, K. Qanungo, T. Barclay, W. Cordes, J. Organomet.
Chem. 534 (1997) 213.
[7] R. Scheffold, G. Rytez, L. Walder, in: S. Scheffold (Ed.), Transi-
tion Metals in Organic Synthesis, Wiley, Chichester, 1983, p. 3.
[8] B.P. Branchaud, R.M. Slade, Tetrahedron Lett. (1994) 4071
[9] A.K. Ghosh, Y. Chen, Tetrahedron Lett. (1995) 505
[10] W.M. Wright, T.L. Smalley Jr., M.E. Welker, A.L. Rheingold, J.
Am. Chem. Soc. 116 (1994) 6777.
[11] M.W. Wright, M.E. Welker, J. Org. Chem. 61 (1996) 133.
[12] B.D. Gupta, V. Singh, K. Qanungo, V. Vijaikanth, R.S. Sengar,
J. Organomet. Chem. 582 (1999) 279.
[13] B.D. Gupta, V. Dixit, I. Das, J. Organomet. Chem. 572 (1999)
49.
[14] T. Brown, A. Dronsfield, A. Jablonski, A.S. Wilkinson, Tetrahe-
dron Lett. 37 (1996) 5413.
[15] G.B. Gill, G. Pattenden, G.A. Roan, Tetrahedron Lett. 37
(1996) 9369.
[16] J.L. Gage, B.P. Branchaud, Tetrahedron Lett. 40 (1997) 7007.
[17] M. Kijima, K. Nakazato, T. Sato, Chem. Lett. (1994) 347
[18] D.M. Haddelton, J.C. Padget, G.C. Overbeek, PCT Intl. Appl,
WO 95, 04, 767
[47] K.L. Brown, A.W. Awtrey, Inorg. Chem. 17 (1978) 111.
[48] D. Datta, G.T. Sharma, J. Chem. Soc. Dalton Trans. (1989) 11
[49] L.G. Marzilli, F. Bayo, M.F. Summers, L.B. Thomas, E. Zan-
grando, N. Bresciani-Pahor, M. Mari, L. Randaccio, J. Am.
Chem. Soc. 109 (1987) 6045.
[50] RC. Stewart, L.G. Marzilli, J. Am. Chem. Soc. 100 (1978) 817.
[51] N. Bresciani-Pahor, S. Gerimia, C. Lopez, L. Randaccio, E.
Zangrando, Inorg. Chem. 29 (1990) 1043.
[52] E. Zangrando, N. Bresciani-Pahor, L. Randaccio, J.P. Charland,
L.G. Marzilli, Organometallics 5 (1986) 1938.
[53] L. Randaccio, S. Geremia, E. Zangrando, C. Ebert, Inorg.
Chem. 33 (1994) 4641.
[54] N. Bresciani-Pahor, L. Randaccio, E. Zangrando, P.J. Toscano,
Inorg. Chim. Acta 96 (1985) 193.
[55] P.J. Toscano, T.F. Swider, L.G. Marzilli, N. Bresciani-Pahor, L.
Randaccio, Inorg. Chem. 22 (1983) 3416.
[56] B.D. Gupta, M. Roy, I. Das, J. Organomet. Chem. 397 (1990)
219.
[57] G.N. Schrauzer, E. Deutsch, J. Am. Chem. Soc. 91 (1969) 3341.

114
B.D. Gupta et al. / Journal of Organometallic Chemistry 608 (2000) 106–114
[58] D. Dodd, M.D. Johnson, B.L. Lockman, J. Am. Chem. Soc.
99 (1977) 3664.
[63] B.D. Gupta, K. Qanungo, V. Singh, J. Shobini, Ind. J. Chem.
37A (1998) 707.
[59] C. Lopez, S. Alvaez, M. Font-Bardia, X. Solans, J.
Organomet. Chem. 414 (1991) 245.
[64] G.N. Schrauzer, Inorg. Synth. 11 (1968) 61.
[65] G. Costa, G. Tauhzer, A. Puxeddu, Inorg. Chim. Acta
(1969) 45.
[66] W. Beck, T. Kemmerich, H. Bohme, Z. Natureforsch
Anorg. Org. Chem. 34B (1979) 200.
[67] N.R. Draper, H. Smith, Applied Regression Analysis, Wiley,
New York (1966) pp. 13–21
3
[60] (a) C. Lopez, S. Alvarez, X. Solans, M. Font-Bardia, Polyhe-
dron 11 (1992) 1637. (b) C. Lopez, S. Alvarez, M. Aguilo, X.
Solans, M. Font-Altaba, Inorg. Chim. Acta. 127 (1987) 153.
(c) C. Lopez, S. Alvarez, X. Solans, M. Font-Altaba, Inorg.
Chem. 25 (1986) 2962
B
[61] B.D. Gupta, K. Qanungo, J. Organomet. Chem. 543 (1997)
125.
[68] S. Bruckner, L. Randaccio, J. Chem. Soc. Dalton Trans.
(1974) 1017
[62] B.D. Gupta, K. Qanungo, J. Organomet. Chem. 557 (1998)
243.
[69] N. Bresciani-Pahor, M. Calligaris, L. Randaccio, L.G.
Marzilli, Inorg. Chim. Acta 32 (1979) 181.
.