Organocobaloximes with mixed dioxime equatorial ligands: A convenient one-pot synthesis. X-ray structures and cis-trans influence studies

Article abstract of DOI:10.1021/om030089s

A simple and general route to the synthesis of organocobaloxime with mixed dioxime ligands, RCo(L)(dpgH)Py [L = dmgH and chgH] (R = Me-Dec), has been described. The crystal structure of four complexes, ClCo(L)(dpgH)Py and MeCo(L)(dpgH)Py [L = dmgH and chgH], is reported. The structural study reveals that both the nonclassical C-H... as well as the classical O-H...O intermolecular hydrogen bonding is present and leads to the formation of one-dimensional dimeric or polymeric structures. ¹H and ¹³C NMR coordination shifts in the axial pyridine ligand show clear correlations with the chemical shift of the equatorial ligand. These correlations can be rationalized with the aid of the ring current model.

Full text of DOI:10.1021/om030089s

2670
Organometallics 2003, 22, 2670-2678
Or ga n ocoba loxim es w ith Mixed Dioxim e Equ a tor ia l
Liga n d s: A Con ven ien t On e-P ot Syn th esis. X-r a y
Str u ctu r es a n d Cis-Tr a n s In flu en ce Stu d ies
B. D. Gupta,*,† Veena Singh,† R. Yamuna,† T. Barclay,‡ and W. Cordes‡
Chemistry Department, Indian Institute of Technology, Kanpur, U.P. India 208016, and
Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas
Received February 7, 2003
A simple and general route to the synthesis of organocobaloxime with mixed dioxime
ligands, RCo(L)(dpgH)Py [L ) dmgH and chgH] (R ) Me-Dec), has been described. The crystal
structure of four complexes, ClCo(L)(dpgH)Py and MeCo(L)(dpgH)Py [L ) dmgH and chgH],
is reported. The structural study reveals that both the nonclassical C-H‚‚‚O as well as the
classical O-H‚‚‚O intermolecular hydrogen bonding is present and leads to the formation
1
of one-dimensional dimeric or polymeric structures. H and 13C NMR coordination shifts in
the axial pyridine ligand show clear correlations with the chemical shift of the equatorial
ligand. These correlations can be rationalized with the aid of the ring current model.
In tr od u ction
that the Costa model is a closer electrochemical mimic
of B12 than the cobaloxime.2b
Organocobaloximes (general formula RCo(L)2B, where
R, an organic group σ bonded to cobalt; B, axial base
trans to the organic group; L, dioxime ligand, e.g., gH,
glyoxime, dmgH, dimethylglyoxime; chgH, 1,2-cyclo-
hexanedione dioxime; dpgH, diphenylglyoxime (all
monoanions)) have extensively been used to mimic the
vitamin B12 coenzyme.1 Apart from the structural
similarities, the theoretical calculations have shown a
close resemblance between the MO calculations of
cobalamin and cobaloximes.2a This is reflected in their
catalytic abilities for many important chemical trans-
formations.3-8 Finke et al., however, have suggested
Many papers have appeared in the recent past that
described the spectral and structural properties of
cobaloximes. Despite this wealth of information a great
deal of interest has been devoted to the study of
correlations between NMR spectral data and molecular
structure of these complexes.1a-c The driving force
behind all this work is to obtain a clear relationship
between all the properties. This would help to system-
atize the large amount of chemical information currently
available and it might lead to successful design of novel
derivatives with desired properties. Several studies with
this aim have appeared in the literature.9,10,11 For
instance, the reported trends in the 1H NMR chem-
ical shifts in RCo(dmgH)2B are related to the mutual
cis and trans influence of the ligands.9,10d,11 The reported
* Corresponding author. Tel: +91-512-2597046. Fax: +91-512-
2597436. E-mail: bdg@iitk.ac.in.
† Indian Institute of Technology.
‡ University of Arkansas.
1
studies also include the multilinear correlation of H
(1) (a) Bresciani-Pahor, N.; Forcolin, M.; Marzilli, L. G.; Randaccio,
L.; Summers, M. F.; Toscano, P. J . Coord. Chem. Rev. 1985, 63, 1, and
references therein. (b) Randaccio, L.; Bresciani-Pahor, N.; Zangrando,
E.; Marzilli, L. G. Chem. Soc. Rev. 1989, 18, 225. (c) Randaccio, L.
Comments Inorg. Chem. 1999, 21, 327. (d) Tada, M. Rev. Heteroat.
Chem. 1999, 20, 97.
NMR chemical shifts of B with the wavelength of the
Co-dioxH charge transfer band.11 These spectral cor-
relations were initially rationalized on the basis of the
(2) (a) Schrauzer, G. N.; Lee, L. P.; Sibert, J . W. J . Am. Chem. Soc.
1970, 92, 2, 2997. (b) Elliott, C. M.; Hershenhart, E.; Finke, R. G.;
Smith, B. L. J . Am. Chem. Soc. 1981, 103, 5558.
(8) Yamada, B.; Toda, K.; Aoki, S. Polym. Bull. (Berlin) 1995, 35,
245.
(9) (a) Marzilli, L. G.; Bayo, F.; Summers, M. F.; Thomas, L. B.;
Zangrando, E.; Bresciani-Pahor, N.; Mari, M.; Randaccio, L. J . Am.
Chem. Soc. 1987, 109, 6045. (b) Brown, K. L.; Satyanarayana, S. J .
Am. Chem. Soc. 1992, 114, 5674. (c) Datta, D.; Sharma, G. T. J . Chem.
Soc., Dalton Trans. 1989, 115. (d) Zangrando, E.; Bresciani-Pahor, N.;
Randaccio, L.; Charland, J . P.; Marzilli, L. G. Organometallics 1986,
5, 1938. (e) Bresciani-Pahor, N.; Geremia, S.; Lopez, C.; Randaccio,
L.; Zangrando, E. Inorg. Chem. 1990, 29, 1043. (f) Trogler, W. C.;
Stewart, R. C.; Epps, L. A.; Marzilli, L. G. Inorg. Chem. 1974, 13, 1564.
(g) Randaccio, L.; Geremia, S.; Zangrando, E.; Ebert, C. Inorg. Chem.
1994, 33, 4641. (h) Stewart, R. C.; Marzilli, L. G. Inorg. Chem. 1977,
16, 424.
(10) (a) Trogler, W. C.; Marzilli, L. G. Inorg. Chem. 1975, 14, 2942.
(b) Hill, H. A. O.; Morallee, K. G. J . Chem. Soc. A 1969, 554. (c) Bied-
Charreton, C.; Gaudemer, A. Bull. Soc. Chim. Fr. 1972, 861. (d)
Gilaberte, J . M.; Lopez, C.; Alvarez, S. J . Organomet. Chem. 1988, 342,
C13.
(3) (a) Giese, B. Radicals in Organic Synthesis: Formation of
Carbon-Carbon Bonds; Pergamon Press: Oxford, 1986. (b) Scheffold,
R.; Rytez, G.; Walder, L. In Transition Metals in Organic Synthesis;
Scheffold, S., Ed.; Wiley: Chichester, 1983; Vol. 3. (c) Branchaud, B.
P.; Slade, R. M. Tetrahedron Lett. 1994, 35, 4071. (d) Ghosh, A. K.;
Chen, Y. Tetrahedron Lett. 1995, 36, 505. (e) Wright, W. M.; Smalley,
T. L., J r.; Welker, M. E.; Rheingold, A. L. J . Am. Chem. Soc. 1994,
116, 6777. (f) Wright, M. W.; Welker, M. E. J . Org. Chem. 1996, 61,
133. (g) Welker, M. E. Curr. Org. Chem. 2001, 5, 785. (h) Gupta, B.
D.; Singh, V.; Qanungo, K.; Vijaikanth, V.; Sengar, R. S. J . Organomet.
Chem. 1999, 582, 279. (i) Gupta, B. D.; Dixit, V.; Das, I. J . Organomet.
Chem. 1999, 572, 49.
(4) (a) Brown, T.; Dronsfield, A.; J ablonski, A.; Wilkinson, A.-S.
Tetrahedron Lett. 1996, 37, 5413. (b) Gill, G. B.; Pattenden, G.; Roan,
G. A. Tetrahedron Lett. 1996, 37, 9369. (c) Gage, J . L.; Branchaud, B.
P. Tetrahedron Lett. 1997, 38, 7007.
(5) Kijima, M.; Nakazato, K.; Sato, T. Chem. Lett. 1994, 347.
(6) Haddelton, D. M.; Padget, J . C.; Overbeek, G. C. PCT Intl. Appl.
WO 95,04,767.
(7) Arvanitopoulos, L. D.; Gruel, M. P.; Harwood, H. J . Polym. Prepr.
1994, 35, 459.
(11) (a) Lopez, C.; Alvarez, S.; Solans, X.; Font-Altaba, M. Inorg.
Chem. 1986, 25, 2962. (b) Lopez, C.; Alvarez, S.; Solans, X.; Font-
Altaba, M. Inorg. Chim. Acta 1986, 111, L19. (c) Gilaberte, J . M.; Lopez,
C.; Alvarez, S.; Font-Bardia, M.; Solans, X. New J . Chem. 1993, 17,
193.
10.1021/om030089s CCC: $25.00 © 2003 American Chemical Society
Publication on Web 05/24/2003

Organocobaloximes with Dioxime Ligands
Organometallics, Vol. 22, No. 13, 2003 2671
Ta ble 1. H1 NMR a n d λm a x of 1b-10b
pyridine
λ
max(log ꢀ)
(methanol)
compd
O-H- -O
R
â
γ
dmgH
dpgH
Co-CH2
rest of alkyl chain
methyl
1b
2b
3b
4b
5b
6b
7b
8b
9b
10b
18.49
18.43
18.43
18.42
18.43
18.43
18.41
18.43
18.43
18.43
8.78, 7.39, 7.79
8.77, 7.38, 7.78
8.76, 7.37, 7.77
8.76, 7.38, 7.78
8.76, 7.38, 7.77
8.76, 7.38, 7.77
8.76, 7.37, 7.77
8.76, 7.37, 7.77
8.76, 7.37, 7.77
8.76, 7.37, 7.79
2.18
2.19
2.18
2.18
2.18
2.17
2.17
2.17
2.17
2.18
7.06-7.10, 7.18-7.22
7.05-7.11, 7.17-7.29
7.04-7.10, 7.17-7.26
7.04-7.10 7.18-7.29
7.04-7.07, 7.18-7.29
7.04-7.10, 7.18-7.23
7.04-7.11, 7.17-7.29
7.04-7.11, 7.18-7.29
7.01-7.10, 7.18-7.29
7.00-7.10, 7.18-7.30
1.14
0.61
0.89
0.87
0.83
0.85
0.86
0.86
0.83
0.87
447.7 (3.38)
459.9 (3.41)
460.0 (3.23)
457.1 (3.39)
460.5 (3.50)
460.4 (3.40)
459.4 (3.32)
460.9 (3.35)
458.1 (3.36)
457.0 (3.37)
2.05
1.92
1.94
1.93
1.93
1.93
1.93
1.93
1.93
1.20-1.26
1.14-1.22 1.25-1.36
1.20-1.31
1.16-1.29
1.19-1.28
1.17-1.27
1.23-1.27
1.23-1.27
cobalt anisotropy,9 but more recently the ring current
formalism has been preferred.11 As per this model, a
ring current resulting from a 12 π delocalized electron
system of the cobaloxime would affect the nuclei in
different ways, depending on their relative position to
the metallabicycle, shielding those on top and deshield-
ing those at the sides of the ring. Most of the above
information has, however, come from the study of dmgH
complexes only. Studies involving other oximes with
varying steric and electronic properties such as gH,12
chgH,13 and dpgH2,14 have been few. Much of the
information on the correlation study has been derived
from 1H NMR chemical shifts, as only a few cobal-
oximes have been characterized by both 1H and 13C
NMR.1a,9h,11c,12d,15 The in-depth study with 13C on equa-
torial ligands other than dmgH is, therefore, lacking.
and (e) to test the validity of the recently proposed ring
current model.
We also report the crystal structure of four cobal-
oximes with mixed dioxime equatorial ligands, MeCo-
(dmgH)(dpgH)Py, MeCo(chgH)(dpgH)Py, ClCo(dmgH)-
(dpgH) Py, and ClCo(chgH)(dpgH)Py.
Exp er im en ta l Section
ClCoIII(L)2Py [L ) dmgH, chgH, dpgH] were synthesized
by the literature procedure.13b,14c,16 The synthesis of ClCoIII
-
(dmgH)(dpgH)Py and ClCoIII(chgH)(dpgH)Py has been detailed
earlier by us.15e The alkyl halides dimethylglyoxime, diphenyl-
glyoxime, and nioxime were purchased from Aldrich and were
used as received. Silica gel (100-200 mesh) and distilled
solvents were used in all chromatographic separations.
1H and 13C spectra were recorded on a J EOL J NM 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 degassed solvent was used for recording spectra. The
elemental analysis was carried out at the Regional Sophisti-
cated Instrumentation Center, Lucknow. A J ulabo UC-20 low-
temperature refrigerated circulator was used to maintain the
desired temperature.
1
Efforts to correlate H and 13C resonance were made,
but the results were rather poor.9h,15b
Keeping the above discussion in mind, we report the
synthesis and study of a new class of alkyl cobaloximes
with two dissimilar dioxime wings, RCo(L)(L′)Py, in the
same molecule where L ) dmgH or chgH, L′ ) dpgH,
and R ) alkyl group. All these compounds are new and
have been reported for the first time. The spectroscopic
studies (1H, 13C, UV-vis) on these complexes have been
carried out. The aim of the study is (a) to verify if the
trends in 1H NMR and UV data reported earlier for
alkyl cobaloximes also apply to alkyl mixed dioxime
cobaloximes, (b) to see if 13C gives similar or better
information than 1H NMR, (c) to see if there is any
correlation in 1H, 13C, and UV-vis data, (d) to see if
one equatorial wing transmits its electronic effect to the
other dioxime wing and thus affects the chemical shifts,
Cr ysta l Str u ctu r e Deter m in a tion a n d Refin em en ts.
Orange crystals were obtained by slow evaporation of solutions
of the complexes in methanol. A small crystal size (as in Table
5) was selected and mounted on an Enraf-Nonius CAD-4
diffractometer (Nonius Kappa CCD for compound 22b) equipped
with a graphite monochromator. The unit cell parameters were
determined from 25 reflections (39 366 reflections for 22b) (2θ
range 16-18 for 1b and 21b, 2-50 for 22b, 19-20 for 11b),
and the cell parameters were refined by least-squares. Intensi-
ties were collected with Mo KR radiation, using the θ-2θ, 2
deg phi and omega scan techniques. For compound 21b, 4562
intensities were measured in the range 4-51 and 4375 were
considered as observed applying the condition I > 0.0σ(I), while
4837 reflections were measured for compound 11b in the same
range, from which 4681 were considered as observed. For
compound 22b 39 366 intensities were measured in the range
4-50, from which 4353 were considered as observed applying
the above condition, while 4348 reflections were measured for
compound 1b in the same range, from which 4167 were
considered as observed applying the condition I > 1.0σ(I).
Absorption corrections based on scan data were applied to the
reflection intensities for these four compounds.
(12) (a) Toscano, P. J .; Swider, T. F.; Marzilli, L. G.; Bresciani-Pahor,
N.; Randaccio, L. Inorg. Chem. 1983, 22, 3416, and references therein.
(b) Bresciani-Pahor, N.; Randaccio, L.; Zangrando, E.; Toscano, P. J .
Inorg. Chim. Acta 1985, 96, 193. (c) Lopez, C.; Alvarez, S.; Solans, X.;
Font-Altaba, M. Inorg. Chim. Acta 1986, 121, 71. (d) Gupta, B. D.;
Yamuna, R.; Veena, S.; Usha, T. Organometallics 2003, 22, 226.
(13) (a) Gupta, B. D.; Roy, M.; Das, I. J . Organomet. Chem. 1990,
397, 219. (b) Gupta, B. D.; Kushal, Q.; Yamuna, R.; Pandey, A.; Usha,
T.; Vijaikanth, V.; Veena, S.; Barclay, T.; Cordes, W. J . Organomet.
Chem. 2000, 608, 106. (c) Dodd, D.; J ohnson, M. D.; Lockman, B. L. J .
Am. Chem. Soc. 1977, 99, 3664. (d) Gupta, B. D.; Qanungo, K.; Barclay,
T.; Cordes, W. J . Organomet. Chem. 1998, 560, 155.
(14) (a) Lopez, C.; Alvarez, S.; Font-Bardia, M.; Solans, X. J .
Organomet. Chem. 1991, 414, 245. (b) Lopez, C.; Alvarez, S.; Solans,
X.; Font-Bardia, M. Polyhedron 1992, 11, 1637. (c) Lopez, C.; Alvarez,
S.; Aguilo, M.; Solans, X.; Font-Altaba, M. Inorg. Chim. Acta 1987,
127, 153.
(15) (a) Moore, S. J .; Lachicotte, R. J .; Sullivan, S. T.; Marzilli, L.
G. Inorg. Chem. 1999, 38, 383. (b) Kargol, J . A.; Crecely, R. W.;
Burmeister, J . L.; Toscano, P. J .; Marzilli, L. G. Inorg. Chim. Acta 1980,
40, 79. (c) Bied-Charreton, C.; Septe, B.; Gaudemer, A. Org. Magn.
Reson. 1975, 7, 116. (d) Gupta, B. D.; Tiwari, U.; Barclay, T.; Cordes,
W. J . Organomet. Chem. 2001, 629, 83. (e) Gupta, B. D.; Yamuna, R.;
Singh, V.; Tiwari, U.; Barclay, T.; Cordes, W. J . Organomet. Chem.
2001, 627, 80.
The structures were isotropically refined by full-matrix
least-squares method, using the NRC386, NRCVAX, and the
SHELXL-93 computer programs.17 The function minimized
was [∑[w(|Fo| - |Fc|)2]0.5], where w ) [σ2(Fo2) + (0.05Fo2)2].
(16) Schrauzer, G. N. Inorg. Synth. 1968, 11, 61.
(17) (a) NRCVAX-An Interactive program system for Structure
Analysis. Gabe, E. J .; Lepage, Y.; Charland, J . P.; Lee, F. L.; White,
P. S. J . Appl. Crystallogr. 1989, 22, 383. (b) Sheldrick, G. M.
SHELXL93, Program for the Refinement of Crystal Structures;
University of Gottingen: Germany, 1993. (c) NRC386 (PC version of
NRCVAX).

2672 Organometallics, Vol. 22, No. 13, 2003
Ta ble 2. H1 NMR a n d λm a x of 11b-20b
chgH
Gupta et al.
pyridine
rest of
λmax(logꢀ)
compd O-H‚‚‚O
R
â
γ
C2 ortho
C1 para
dpgH
Co-CH2 alkyl chain methyl (methanol)
11b
12b
13b
14b
15b
16b
17b
18b
19b
20b
18.25
18.18
18.19
18.18
18.19
18.18
18.18
18.18
18.18
18.17
8.79 7.40, 7.80 1.56-1.74 2.55-2.67, 7.02-7.12, 7.16-7.26
1.15
0.61
0.90
0.87
0.84
0.85
0.85
0.86
0.86
0.87
445.0 (3.21)
461.0 (3.37)
461.7 (3.24)
462.0 (3.50)
462.1 (3.43)
461.9 (3.47)
460.1 (3.44)
462.0 (3.49)
459.3 (3.43)
463.6 (3.33)
2.75-2.87
8.77 7.39, 7.79 1.59-1.71 2.56-2.66, 7.02-7.11, 7.16-7.26
2.05
1.94
1.95
1.94
1.95
1.97
1.95
1.95
1.95
2.76-2.84
8.77 7.38, 7.78 1.57-1.75 2.54-2.67, 7.02-7.10, 7.16-7.28
1.18-1.30
1.15-1.39
1.19-1.31
1.16-1.31
1.17-1.33
1.17-1.28
1.17-1.30
1.23-1.27
2.73-2.86
8.77 7.38, 7.78 1.57-1.75 2.56-2.66, 7.02-7.10, 7.16-7.26
2.75-2.85
8.77 7.38, 7.77 1.61-1.74 2.56-2.67, 7.02-7.12, 7.17-7.26
2.76-2.84
8.77 7.38, 7.78 1.61-1.71 2.56-2.63, 7.02-7.10, 7.17-7.28
2.76-2.84
8.77 7.38, 7.78 1.59-1.75 2.56-2.63, 7.01-7.10, 7.16-7.29
2.76-2.84
8.77 7.38, 7.78 1.57-1.74 2.56-2.67, 7.01-7.12, 7.15-7.28
2.74-2.86
8.77 7.38, 7.78 1.57-1.74 2.53-2.67, 7.01-7.10, 7.14-7.26
2.76-2.86
8.77 7.38 7.80 1.61-1.69 2.56-2.66, 7.02-7.10, 7.17-7.29
2.76-2.84
Ta ble 3. 13C NMR of 1b-10b
1b
2b
3b
4b
5b
6b
7b
8b
9b
10b
dmgH
CdN(dpgH)
PyR
CdN(dmgH)
12.17
150.57
150.05
149.36
125.39
137.74
130.25
129.56
127.82
128.72
12.15
150.57
150.05
149.33
125.32
137.62
130.31
129.50
127.81
128.67
12.18
150.64
149.99
149.40
125.32
137.63
130.30
129.50
127.81
128.67
35.72
12.18
150.63
150.02
149.37
125.31
137.62
130.35
129.48
127.83
128.66
12.18
150.61
150.03
149.36
125.31
137.60
130.34
129.45
127.81
128.66
12.17
150.61
150.03
149.35
125.30
137.60
130.36
129.49
127.83
128.66
12.18
12.20
150.59
150.00
149.34
125.31
137.62
130.34
129.48
127.82
128.66
33.40
31.87
30.74
30.71
29.45
29.31
22.69
14.13
12.17
12.18
150.60
150.02
149.34
125.31
137.61
130.35
129.49
127.82
128.66
33.43
31.92
30.73
29.67
29.62
29.57
29.50
29.38
22.70
150.61
150.03
149.35
125.31
137.61
130.35
129.49
127.83
128.66
150.60
150.01
149.35
125.31
137.62
130.34
129.48
127.82
128.69
33.42
31.93
30.79
30.72
29.61
29.49
29.31
22.68
14.13
Pyâ
Pyγ
C*
CR
Câ
Cγ
C1
C2
C3
C4
C5
C6
C7
C8
C9
C10
16.00
23.94
15.02
33.11
23.74
14.04
32.93
30.37
22.52
14.10
31.72
30.70
30.42
22.68
14.09
31.91
30.74
29.70
29.17
22.65
14.15
14.13
Ta ble 4. 13C NMR of 11b-20ba
11b
12b
13b
14b
15b
16b
17b
18b
19b
20b
CdN (dpgH)
CdN (chgH)
PyR
Pyâ
Pyγ
C*
150.53
149.93
150.09
125.36
137.70
130.20
129.50
127.71
128.65
25.23
150.59
150.13
150.13
125.32
137.62
130.32
129.53
127.82
128.67
25.27
150.68
150.23
150.05
125.32
137.62
130.33
129.54
127.84
128.68
25.32
150.66
150.21
150.05
125. 32
137.62
130.37
129.49
127.83
128.65
25.31
150.64
150.19
150.05
125. 32
137.61
130.36
129.49
127.83
128.64
25.31
21.51
33.39
32.89
30.38
22.54
14.09
150.64
150.19
150. 05
125. 32
137.61
130.36
129.49
127.83
128.64
25.31
21.51
33.48
31.75
30.71
30.39
22.66
14.11
150.64
150.19
150. 05
125. 32
137.61
130.37
129.53
127.77
128.64
25.31
21.51
33.48
31.88
30.70
29.70
29.18
22.66
14.16
150.64
150.18
150. 05
125. 32
137.61
130.38
129.53
127.82
128.63
25.27
21.51
33.46
31.89
30.73
29.47
29.32
29.26
22.70
150.64
150.17
150. 05
125.34
137.60
130.38
129.49
127.81
128.63
25.31
21.51
33.47
31.94
30.73
30.70
29.60
29.49
29.34
150.65
150.18
150.12
125.32
137.60
130.38
129.50
127.82
128.64
25.31
21.51
33.50
31.93
30.74
30.70
29.63
29.53
29.46
29.40
22.71
14.13
CR
Câ
Cγ
C1 (chgH)
C2 (chgH)
C1
21.39
12.72
21.52
21.52
35.81
23.95
15.06
21.50
C2
C3
C4
C5
C6
C7
C8
C9
16.06
33.17
23.74
14.08
14.11
22.68
14.13
C10
a
C*: phenyl carbon attached to -CdN. CR, Câ, Cγ: phenyl carbons.
The hydrogen atoms of the OH groups were located on
difference maps and constrained to the difference map posi-
tions. The orientations of the methyl H atoms were also
determined from difference maps and refined with an overall
isotropic temperature factor. The cyclohexane group of 11b and
22b has disorder with 70-30 occupancies (a and b atoms) and

Organocobaloximes with Dioxime Ligands
Organometallics, Vol. 22, No. 13, 2003 2673
Ta ble 5. Cr ysta l Da ta a n d Str u ctu r e Refin em en t P a r a m eter s for 21b, 22b, 1b, a n d 11b
21b
22b
1b
11b
formula
fw
CoClO4N5C23H23
527.85
CoClO4N5C25H25
553.88
CoO4N5C24H26
507.43
CoO4N5C26H28
533.47
cryst size, mm
cryst color
0.16 × 0.36 × 0.40
0.25 × 0.35 × 0.55
0.36 × 0.38 × 0.40
0.24 × 0.36 × 0.56
orange
orange
orange
orange
a, Å
b, Å
c, Å
9.130(2)
9.4271(14)
14.581(3)
83.788(14)
88.899(15)
71.181(14)
1180.8(4)
25
16-18
1.48
P1h
2
15.334(1)
9.332(1)
17.806(1)
9.0192(13)
9.6727(15)
14.589(2)
83.313(13)
78.701(12)
72.286(12)
1186.7(3)
25
16-18
1.42
P1h
2
15.165(4)
9.481(2)
17.933(6)
R, deg
â, deg
103.11(1)
102.75(2)
γ, deg
V, Å3
2481.6(3)
39,366
2-50
1.48
P21/n
4
2514.8(12)
25
19-20
1.41
P21/n
4
cell detn, reflns
cell detn, 2θ range, deg
d(calcd), g cm-3
space group
Z
F000
545.1
1146.0
528.8
1111.75
radiation
λ, Å
temp, K
Mo KR, graphite monochromated
0.7107
293
0.7107
298
0.7107
0.7107
293
293
0.72
linear abs coeff, mm-1
diffractometer
scan technique
2θ range, deg
h, k, l ranges
drift of stds, %
absorption correction
absorption range
no. of reflns measd
no. of unique reflns
R for merge
no. of reflns in refinement,
I > 0.0σ(I)
0.88
0.84
0.76
Enraf-Nonius CAD-4
Nonius Kappa CCD
2° phi and omega scans
Enraf-Nonius CAD-4
Enraf-Nonius CAD-4
θ-2θ
4-51
θ-2θ
4-50
θ-2θ
4-51
-18, 18; 0, 11; 0, 21
1.6
analytical
0.75-0.86
4837
4681
0.019
4-50
-11, 11; -11, 11; -17, 0
-18, 18; -11, 11; -21, 21
-10,10;-11,11; -17, 0
1.4
1.0
none
2.2
analytical
0.54-0.87
4562
4375
0.020
analytical
0.74-0.79
4348
4167
0.015
39 366
4353
0.030
4353
4375
I > 1.0σ(I) 3396
4681
no. of params refined
R(F), Rw(F)
R for I > 3.0σ(I)
GOF
307
0.059, 0.064
0.039
0.94
0.05
0.00
none
327
308
0.040, 0.053
0.035
1.26
0.03
0.00
0.04(3)
-0.25(5), +0.42(5)
323
0.069, 0.068
0.039
0.93
0.05
0.00
0.053, 0.079
0.036
1.20
0.05
0.00
P, w-1) [σ2(I) + pI2]/4F2
largest ∆/σ
extinction corr
none
-0.53(9), +0.55(9)
final diff map, e Å-3
-0.49(10), +0.79(10)
-0.29(8), +1.02(8)
50-50 occupancies, respectively, in the model with all four
carbons refined using isotropic displacement parameters. The
pertinent crystal data and refinement parameters are compiled
in Table 5.
Syn th esis of a lk ylCo(d m gH)(d p gH)P y (1b-10b). These
were synthesized by two methods. The general procedure is
outlined below.
Meth od a . NaOH (1 pellet dissolved in 1.0 mL of water)
was added to a suspension of ClCoIII(dmgH)2Py (0.201 g, 0.5
mmol) and ClCoIII(dpgH)2Py (0.326 g, 0.5 mmol) in methanol
(10 mL), and the reaction mixture was thoroughly purged with
argon for 15 min. The temperature was brought down to 0 °C
by a J ulabo refrigerator circulator. The reaction mixture
turned deep blue after the addition of NaBH4 (0.048 g, 1.27
mmol in 1 mL of water). Methyl iodide (0.213 g, 1.5 mmol) in
methanol (5 mL) was added dropwise. The reaction mixture
was stirred for 3 h in the dark, during which it was brought
to ambient temperature, and the contents were poured into
water. The orange-red solid was filtered, dried, and chromato-
graphed on a silica gel column with ethyl acetate/chloroform
as eluent, yielding three products: 1a (0.257 g, 65%), 1b (0.024
g, 8%), and 1c (0.065 g, 27%). The products 1a and 1c were
compared with the authentic samples from our laboratory.
preparation of 1b was used. Now a mixture of ClCoIII(chgH)2-
Py (0.230 g, 0.5 mmol) and ClCoIII(dpgH)2Py (0.326 g, 0.5
mmol) was used. Three products were isolated and purified
by column chromatography: 11a (0.235 g, 59%), 11b (0.031
g, 9%), and 11c (0.085 g, 32%). The products 11a and 11c were
compared with the authentic samples from our laboratory.
Met h od b. The same procedure as outlined above for
the preparation of 1b (method b) was used except that
ClCoIII(chgH)(dpgH)Py (0.277 g, 0.5 mmol) was used as the
starting cobaloxime. Only two products were isolated and
purified by column chromatography: 11a (0.006 g, 4%) and
11b (0.145 g, 96%).
Sep a r a tion of P r od u cts: Colu m n Deta ils. The orange-
red powder containing the mixture of cobaloximes, dissolved
in a minimum amount of chloroform, was loaded on a silica
gel (100-200 mesh) column pre-eluted with chloroform. The
polarity was increased carefully with ethyl acetate. Three
distinct bands were visible with 10% ethyl acetate in chloro-
form. The first band corresponding to the dpgH complex eluted
out completely with 10% ethyl acetate. The mixed ligand
complex eluted out with a 10-50% ethyl acetate/chloroform
mixture, and the dmgH complex finally came out with a 50-
100% ethyl acetate/chloroform mixture. Any deviation in these
ratios gave the contaminated products.
Meth od b. The same procedure as outlined in method a
was used except that ClCoIII(dmgH)(dpgH)Py (0.529 g, 1 mmol)
was used as the starting cobaloxime. Three products were
isolated and purified by column chromatography: 1a (0.037
g, 10%), 1b (0.241 g, 84%), and 1c (0.014 g, 6%).
Crystallographic data for the structural analysis (torsion
angle, µ(i,j) values, atomic parameters, bond lengths, and bond
angles) have been deposited with the Cambridge Crystal-
lographic Data Centre, CCDC number for (1b, 11b, 21b, and
22b) as 145905, 145906, 145907, and 145908, respectively.
Copies of the data can be obtained free of charge from the
Syn t h esis of a lk ylCo(ch gH )(d p gH )P y (11b-20b ).
Meth od a . The same procedure as outlined above for the

2674 Organometallics, Vol. 22, No. 13, 2003
Gupta et al.
these findings and the fact that oxidative alkylation of
cobaloxime(I) by alkyl halides finds a much wider use
in the synthesis, we have, first, carried out the reaction
of alkyl halide with a 1:1 mixture of CoI (dmgH)2Py and
CoI (dpgH)2Py under strict inert conditions. Three
products were formed, but the yield of the desired alkyl
mixed ligand complexes 1b-10b was very poor (as given
in the Supporting Information). Similar results were
obtained in the reaction of a 1:1 mixture of CoI(chgH)2-
Py and CoI(dpgH)2Py with alkyl halides. RCo(dpgH)2Py
(1a -10a ) was found to be the major product in all these
reactions. We have made no attempt to study the details
of the extent of formation of each product with time.
The basic aim was to improve the yield of the mixed
ligand complex, and we were able to achieve this by the
reaction of alkyl halide with CoI(L)(dpgH)Py [ L )
dmgH, chgH], generated in situ by the sodium boro-
hydride reduction of ClCo(L)(dpgH)Py [L ) dmgH or
chgH]. The desired complexes were formed in high yield
(67-84%). In all, 20 new alkyl mixed ligand complexes
(1b-20b) were synthesized. In all these reactions the
side products, 1a -10a and 1c-20c, were formed in less
than 10% yield. The spectral characteristics of the
compounds 1b-20b are given in Tables 1-4. The
elemental analysis and the Rf values of compounds 1b-
20b are given in the Supporting Information. The
spectral characteristics of complexes 1a -10a and 1c-
20c have been described before.19 The synthesis of
compounds was confirmed by X-ray structures on
MeCo(dmgH)(dpgH)Py and MeCo(chgH)(dpgH)Py.
We have made no attempt to study its mechanism in
detail. However our results support the earlier observa-
tion by J ohnson et al. that the randomization of the
dioxime ligand along with the alkyl transfer in the
presence of cobaloxime(I) is taking place.13c
Director, CCDC, 12 Union Rd., Cambridge CB2 1EX, UK (fax
+44-1223-336033; e-mail: deposit@ccdc.com.ac.uk or www:
http:/www.ccdc.cam.ac.uk).
Resu lts a n d Discu ssion
1H, 13C, and λmax of alkyl cobaloximes 1a -10a and
1c-20c have previously been reported by us.19 These
have been helpful in the assignment of 1H NMR values
in 1b-20b. 13C values have been assigned for only a
few organocobaloximes in the literature.1a,9h,11c,14a The
following information might be useful in the assignment
of 13C shifts in 1b-20b.
Syn th esis. Organocobaloximes, RCo(L2)B, have been
synthesized by a number of methods; however organo-
cobaloximes with mixed dioxime ligands, RCo(L)(L′)B,
have virtually been unknown until recently.15e
Schrauzer et al. have reported the following reaction
and proposed that the reaction undoubtedly proceeds
by stepwise displacement of the dmgH2 ligand and the
reaction does not involve an ionic intermediate like
CH3-Co2+. However, they could not isolate the inter-
mediate mixed ligand complex, MeCo(dmgH)(chgH)B (B
) Py or H2O).18
The 13C resonances of dmgH (Me), chgH (C1 and C2),
dpgH (C*, CR, Câ, Cγ), Co-CH2, and Pyâ and Pyγ are
easily assigned on the basis of their chemical shifts. The
assignment is consistent with those of the related and
previously described alkylcobaloximes.19 However, the
assignment of CdN (dmgH or chgH), CdN (dpgH), and
PyR has been difficult since these occur very close to each
140 °C
1
other. The assignment has been confirmed by H-13C
MeCo(dmgH)2H2O + chgH2 toluene, Py8
correlation experiments.
MeCo(chgH)2Py
1H and 13C NMR spectra of complexes 1b-20b
(Tables 1-4) show some general trends that are de-
scribed below. We have recently shown that six-
coordinate octahedral organocobaloximes are the ideal
systems for the study of cis and trans influence.12d,13b,d,19
It was observed, on the basis of the spectral studies, that
the cis influencing ability in alkyl cobaloximes followed
the order dpgH > chgH >dmgH. 1H and 13C NMR
studies showed that O-H- - -O and PyR were the most
affected, followed by Pyγ. The present study on alkyl
mixed dioxime complexes throws further light on this
phenomenon.
Later, J ohnson et al. reported the kinetics and
mechanistic study of the apparent alkyl transfer from
alkylcobaloximes to cobaloxime(I), cobaloxime(II), and
cobaloxime(III) reagents.13c They have proposed the
formation of mixed ligand species, RCo(dmgH)(chgH)B,
in solution. However, they did not isolate the spe-
cies. Only solution NMR values of the mixtures are
reported.
We have recently published the synthesis of benzyl
cobaloximes with mixed dioxime ligands.15e In view of
(18) Schrauzer, G. N.; Windgassen, R. J . J . Am. Chem. Soc. 1966,
88, 3738.
(19) Gupta, B. D.; Kushal, Q. J . Organomet. Chem. 1997, 543, 125.

Organocobaloximes with Dioxime Ligands
Organometallics, Vol. 22, No. 13, 2003 2675
The chemical shift values of O-H- - -O in 1b -10b
and 11b-20b lie between their parent cobaloximes,
RCo(L)2Py [L ) dmgH, chgH, dpgH],19 and the chemical
shifts in 11b-20b are consistently upfield as compared
to the value in 1b-10b. Overall, O-H- - -O resonance
follows the order dpgH > dmgH-dpgH > chgH-dpgH ≈
dmgH > gH12d > chgH. The value, however, remains
almost the same within the same series in all the
complexes. We have observed a high downfield shift for
the O-H- - -O resonance, nearly 0.6 ppm in chgH/dpgH
cobaloximes compared to the value in the parent chgH
cobaloxime. This difference can be explained by taking
into account the presence of a phenylic ring in the
neighborhood of the axial ligands and thus producing
deshielding of its nuclei.
and 1c-10c. This is an expected observation since the
present systems have dmgH and dpgH wings and their
shielding/deshielding effect operates in the opposite
direction. Since the overall effect shows deshielding, it
may mean that the effect of the dpgH wing is more
predominant than the dmgH wing. The same observa-
tion was noticed in the PyR shift. This, once again,
supports the ring current model.
1
The H and 13C resonances of pyridine in 1b-20b on
coordination to the cobaloxime moiety shift downfield,
and this coordination shift (∆δ ) δ complex - δ free
py15e) follows the order ∆δ13C Pyγ g ∆δ13C Pyâ > ∆δ13C
PyR (given in the Supporting Information). The same
1
order follows based on the H NMR values.
A change in alkyl group from MefDec within the
same series causes no effect on 1H and 13C values for
PyR,â,γ, CdN, and dmgH (Me) (see Tables 1-4). Also,
there is hardly any change in PyR,â,γ and CdN values
in 1b-10b and 11b-20b.
If the downfield shift, relative to the free ligand, of
the signals corresponding to the HR or CR atoms of the
axial ligand (Co-CH2) is used as a measure of the
cobaloxime ring current intensity, the following series
can be established:
We have observed that δ1H PyR in 1b-20b consist-
ently shifts downfield by about 0.2 ppm compared to free
PyR. This may appear to be at variance to the reported
work in XCo(dmgH)2Py, where δ1H PyR either shifts
upfield on coordination to the cobaloxime moiety (X )
inorganic group) or remains constant (when X is an
alkyl group).11a,15d,19 An opposite situation occurs in the
analogous dpgH compounds, where δ1H PyR either
occurs downfield by 0.3-0.4 ppm (X ) alkyl) or remains
almost constant (X ) inorganic group).15d,19 Does it
mean that the ring current operates differently in dmgH
and dpgH complexes? This may be understood keeping
the following information in mind. Cobaloxime is a
bicyclic system with 12 π electrons, eight from the CdN
bonds and four from the metal dxz and dyz orbitals. MO
calculations of the EH type show that these electrons
occupy six π type orbitals delocalized throughout the
planar cobaloxime moiety, with topologies analogous to
those reported previously for L2MC4H4 metallacycles.
A ring current resulting from the delocalized electron
system of the cobaloxime would affect nuclei in differ-
ent ways, and many of the spectral correlations in
XCo(dmgH)2B have now been rationalized with the aid
of this ring current formalism.11 Apparently, the situ-
ation appears quite opposite in the analogous com-
pounds with dpgH, where the axial ligand signals are
not very sensitive to coordination. This difference has
been explained by taking into account the presence of
a phenylic ring in the neighborhood of the axial ligands
and thus producing deshielding of its nuclei. In effect,
the values of the shielding constants, as determined by
J ohnson and Bovey,20 indicate that the presence of a
phenylic group should produce a shift of =+0.2 ppm on
the signals of the R proton of the axial ligands. It is
concluded, therefore, that the same effect operates on
both dmgH and dpgH, producing an upfield shift on the
axial ligand signal, and this effect is compensated in
the case of dpgH by a long-range effect of the phenyl
substituent on the equatorial ligand. Since organo-
cobaloximes 1b-20b have two dissimilar equatorial
wings, the downfield shift of 0.2 ppm observed in PyR is
justified and supports the ring current model.
dpgH > dmgH-dpgH ≈ chgH-dpgH > dmgH ≈ chgH
A comparison of δ13C in inorganic cobaloximes versus
organocobaloximes is made. The change in axial R group
from an organic (Me, Et, Pr, Bu) to an inorganic group
(Cl, Br, NO2, N3)15d within the same series affects δ13C
for CdN, PyR, Pyâ, and Pyγ. However, CdN is the most
effected and occurs upfield by 2-3 ppm in organo-
cobaloximes (Tables 3 and 4).
It is likely that the electronic effect of one wing may
transmit to the other wing. This, in turn, will effect the
ring current in the metallabicycle as a whole unit and
affect the chemical shifts. We have, therefore, made an
attempt to study the effect of the dpgH wing on the
dmgH/chgH wing and vice versa. It is difficult to
comment whether this effect operates through bond or
through space. A careful study of 1H and 13C NMR
spectra gives the following information.
1H NMR. The δ dmgH (Me) resonance in 1b-10b
appears consistently downfield by 0.06-0.1 ppm as
compared to the corresponding value in 1c-10c. This
shift may appear to be small, but Lopez et al. have
arranged the ligand X in XCo(dmgH)2Py complexes
based on such small upfield shifts (<0.05 ppm) in PyR.11c
We, however, cannot obtain similar information in
11b-20b since δ1H chgH appears as a multiplet.
Similarly, we cannot study the effect of dmgH or chgH
on the dpgH wing since the phenyl group appears as a
multiplet.
13C NMR. The δ13C dmgH (Me) in 1b-4b appears
downfield by about 0.3-0.4 ppm as compared to the
corresponding value in 1c-4c. This supports the finding
in the 1H NMR study. Similarly C1 (chgH carbon) in
11b-14b appears downfield by 0.2 ppm than the value
in 11c-14c. A comparison of the 13C value in the phenyl
ring in 1b-4b versus 1a -4a shows that the C* carbon
in the former occurs about 0.2-0.3 ppm downfield as
compared to the corresponding value in the latter. 13C
It has been observed earlier that the 1H chemical shift
of Co-CR in 1c-10c complexes appears upfield by about
1
0.6 ppm when compared with 1a -10a .19 The H chemi-
cal shift of Co-CR in 1b-10b lies between the corre-
sponding value in 1a -10a and 1c-10c. Similar is the
case in 11b-20b, and the value lies between 11a -20a
1
(20) J ohnson, C. E.; J R.; Bovey, F. A. J . Chem. Phys. 1958, 29, 1012.
NMR information supports the finding in H NMR.

2676 Organometallics, Vol. 22, No. 13, 2003
Gupta et al.
F igu r e 2. Diamond picture of structure MeCo(chgH)-
(dpgH)Py (11b) (for clarity, most of the hydrogen atoms
are omitted).
F igu r e 1. Diamond picture of structure MeCo(dmgH)-
(dpgH)Py (1b) (for clarity, most of the hydrogen atoms are
omitted).
Ta ble 6. Selected Bon d Len gth s (Å) a n d Bon d
An gles (d eg)
21b
22b
1b
11b
Co-Cl
Co-Me
Co-N5
Co-N1
Co-N2
Co-N3
Co-N4
C1-C8
C21-C20
N1-O1
N5-Co-Cl 179.25(7)
N1-Co-N5 90.35(10)
N2-Co-Cl 89.26(8)
N1-Co-N2 81.75(9)
2.2215(9)
2.2322(9)
1.997(3)
1.992(3)
1.9655(23) 1.9765(23) 2.060 (2)
1.8930(22) 1.8869(24) 1.878(2)
1.8792(22) 1.8922(22) 1.871(2)
1.9029(23) 1.9028(24) 1.884(2)
1.9118(23) 1.9148(22) 1.891(2)
1.474(4)
1.468(4)
1.330(3)
2.0624(24)
1.8759(24)
1.8749(24)
1.8824(24)
1.8886(25)
1.478(4)
1.475(4)
1.445(4)
1.345(3)
178.16(7)
90.04(9)
87.68(7)
81.89(10)
2.491(3)
2.492(3)
2.477(3)
2.878(3)
2.478(3)
2.879(3)
1.10(13)
87.43(8)
1.477(4)
1.465(4)
1.342(3)
F igu r e 3. Diamond picture of structure ClCo(dmgH)-
(dpgH)Py (21b) (for clarity, most of the hydrogen atoms
are omitted).
1.451(4)
1.351(3)
179.19(12) 179.33(11)
91.77(10)
87.54(12)
81.72(10)
2.472(3)
2.475(3)
2.452(3)
2.867(3)
2.434(3)
2.851(3)
3.76(18)
88.6(4)
90.92(10)
88.22(12)
81.67(10)
2.491(3)
2.489(3)
2.453(3)
2.848(3)
2.453(3)
2.851(3)
1.14(10)
87.43(8)
O1-O4
O2-O3
N1-N2
N1-N4
N3-N4
N2-N3
Ra
2.503(3)
2.483(3)
2.469(3)
2.902(3)
2.451(3)
2.872(3)
1.42(10)
88.45(9)
τb
a
Butterfly bending angle. b Twist angle of pyridine with respect
to the line joining the midpoints of C1-C8 and C20-C21
.
F igu r e 4. Diamond picture of structure ClCo(chgH)-
(dpgH)Py (22b) (for clarity, most of the hydrogen atoms
are omitted).
Τhe δ (CdN) is known to be sensitive to any change
in the axial or equatorial environment in cobaloximes.
We have, therefore, monitored the change in the δ13C
(CdN) value to see the effect of the dpgH wing on the
dmgH or chgH wing or vice versa. It is found that the
δ13C (CdN) dmgH in 1b-4b appears upfield by about
0.6 ppm as compared to the value in 1c-4c. However,
the effect of the dpgH wing on the chgH wing is almost
negligible [compare δ13C (CdN) chgH in 11b-14b
versus 11c-14c.
To see the effect of the dmgH/chgH wing on the dpgH
wing, we find that δ13C (CdN) dpgH in 1b-10b and
11b-20b appears upfield by about 0.2 ppm as compared
to the δ13C (CdN) dpgH value in 1a -10a (see Support-
ing Information).
X group on Py correlates well with the cis one experi-
enced by methyl groups of the equatorial dmgH ligands
in complexes 1b-4b. While plotting, we have also
included the corresponding inorganic cobaloximes (R )
Cl, Br, NO2, N3).15d
δ1H (dmgH) ) 2.34(1) - 0.81(5) (∆δ1H PyR)
(r2 ) 0.98, esd ) 0.02 ppm)
When considering the equatorial methyl groups, one
would expect the magnetic anisotropy from the closer
CdN double bonds to be more important than that from
the cobalt atom. The fact that the chemical shifts of the
axial protons, affected by the cobalt electrons, correlate
with those of the equatorial methyl, affected by the Cd
N bonds, indicates electronic delocalization throughout
the CoN4C4 system. According to the above equation,
the influence of R on the chemical shifts of cis (Me of
dmgH) and trans (HR of Py) ligands is opposite in sign
but is of the same magnitude (the slope of the least-
So it seems that there is only a small but significant
effect of the one wing on the other, and the effect of the
dpgH wing on the dmgH wing is more than the reverse
case.
Cor r ela tion s
(Eight values are taken for each correlation (X ) Me,
Et, Pr, Bu, Cl, Br, NO2, N3.)) The trans influence of the

Organocobaloximes with Dioxime Ligands
Organometallics, Vol. 22, No. 13, 2003 2677
Ta ble 7. C-H‚‚‚O a n d O-H‚‚‚O In ter a ction s in 21b, 22b, a n d 11b
distance (Å)
angle (deg)
D-H‚‚‚A
bond
Da-H
H‚‚‚Ab
D‚‚‚A
symmetry
Compound 21b
3.3781
C4-H4-O1
O3-H100-O3
0.9557
1.1143
2.5153
2.3481
150.20
100.75
-x, 2-y, 1-z
1-x, 1-y, -z
2.7804
Compound 22b
3.3523
C16-H16-O3
C25-H25B-O2
0.9459
0.9552
2.5818
2.5549
138.84
144.30
3/2-x, -1/2+y, 1/2-z
3/2-x, 1/2+y, 1/2-z
3.3769
Compound 11b
C18-H18-O3
0.9511
2.5617
3.3450
139.81
3/2-x, -1/2+y, 1/2-z
a
D ) donor atom. bA ) acceptor atom
F igu r e 5. C-H- -O and O-H- -O interactions in (a) ClCo(dmgH)(dpgH)Py (21b); C-H- -O interaction in (b) ClCo(chgH)-
(dpgH)Py (22b) and (c) MeCo(chgH)(dpgH)Py (11b). Co ) cyan, Cl ) violet, O ) red, N ) blue, C ) green, H ) white.
(Phenyl rings, disordered carbon atoms in cyclohexane ring, and all other hydrogen atoms are not shown for clarity.)
squares line is ca. -1.0). This fact is in sharp contrast
with the usual trends in the NMR spectra of transition
metal complexes or organometallic compounds, for
which trans influences are much more important than
the cis. This difference can be explained by considering
that in most complexes the cis and trans influences on
the chemical shifts arise from an inductive effect,
whereas in the present case the prevailing effect seems
to be the existence of a ring current associated with an
aromatic-like metallabicyclic system.11a,b Similarly, δ1H
(dmgH) correlate well with the coordination shift of
pyridine (∆δ1H Pyâ).
the ∆δ1H PyR is observed.
δ13C(dmgH) ) 12.78(1) - 3.13(8) (∆δ1H PyR)
(r2 ) 0.99, esd ) 0.03 ppm)
This means one can get the same information using
1
either H or 13C chemical shifts. The chemical shifts 13C
CdN (dmgH) and 13C CdN (dpgH) correlate well with
the coordination shift of pyridine (∆δ1H PyR). δ13C
(dmgH) correlate well with the coordination shift of
pyridine (∆δ13C Pyâ and ∆δ13C Pyγ) (Supporting Infor-
mation with the author).
UV-Vis Sp ectr a . The complexes 1b-10b and 11b-
20b show a Co-C CT band between 447-460 nm and
445-463 nm, respectively, with intensity (log ꢀ) in the
range 3.20-3.50 (Tables 1 and 2). The position of the
CofC CT band depends on the dioxH ligand. The
δ1H (dmgH) ) 3.12(16) - 2.81(53) (∆δ1H Pyâ)
(r2 ) 0.87, esd ) 0.05 ppm)
A fairly good correlation between the δ13C (dmgH) with

2678 Organometallics, Vol. 22, No. 13, 2003
Gupta et al.
variation observed in λCo-C in [Co(dioxH)2(CH3)(Py)]
(405.0, 440.8, 445.0, 445.8, 447.7, 473 nm for dioxH )
gH, dmgH, chgH-dpgH, chgH, dmgH-dpgH, dpgH, re-
spectively)2,19 can be explained in terms of the electron-
donating ability of the dioxH ligand.
in the Co-C and Co-Cl bond lengths in 1b, 11b, 21b,
and 22b when compared with the previously known
structures 1a ,14a 1c,21a 11c,13d ClCo(dmgH)2Py,21b and
ClCo(dpgH)2Py.14c
The butterfly bending angle (R) in 1b is 3.76°, while
it is 1.42°, 1.10°, and 1.14° in 21b, 22b, and 11b
respectively.
X-r a y Cr ysta llogr a p h ic Stu d ies. Descr ip tion of
th e Str u ctu r es 1b, 11b, 21b, a n d 22b. The diamond
diagrams of complexes 1b, 11b, 21b, and 22b are shown
in Figures 1-4. Selected bond distances and angles are
presented in Table 6. The cobalt atom is linked to four
nitrogen atoms belonging to the equatorial plane. Out
of this, two nitrogen atoms belong to the diphenyl-
glyoximato (dpgH) ligand and the other two to the
dimethylglyoximato (dmgH) or 1,2-cyclohexanedione-
dioximato (chgH) ligand. The Co atom deviates 0.0509(13)
Å from the mean equatorial CoN4 plane toward the
neutral pyridine ligand in 1b, while the deviation is
0.0454(13), 0.0218(13), and 0.0276(13) Å in the com-
pounds 11b, 21b, and 22b, respectively. The displace-
ment is toward pyridine in all cases. A methyl or chloro
group and nitrogen of the pyridine ligand occupy the
axial positions, thus completing the octahedral coordi-
nation sphere of the cobalt atom.
The pyridine ring is practically planar and parallel
to the glyoxime C-C bonds, its conformation being
defined by a twist of 88.6(4)°, 87.14(9)°, 88.45(9)°, and
87.43(8)° in the complexes 1b, 11b, 21b, and 22b
respectively.
The Co-C24 (Co-Cl for the compounds 21b and 22b)
and Co-N5 axial bonds are perpendicular (90°) to the
equatorial plane, as seen in the Neq-Co-C24, Neq-Co-
Nax, and C24-Co-Nax bond angles (Table 6). The Co-
N5 bond distance in 21b and 22b is similar to the
corresponding value in ClCo(L)2Py (1.959(2) and 1.965(3)
Å for L ) dmgH and dpgH, respectively),14c,21b but it is
slightly shorter than in 1b and 11b. The Co-Neq bond
distance in compounds 21b and 22b is somewhat longer
than those in 1b and 11b. There is no significant change
The structures of compounds 21b, 22b, and 11b show
some interesting properties. In structure 21b, the
dimeric structure is formed due to C-H‚‚‚O nonclassical
intermolecular hydrogen bonding. This propagates fur-
ther as a one-dimensional polymeric sheet through
O-H‚‚‚O (though the bond angle is acute, bond lengths
are within the range)21c classical intermolecular hydro-
gen bonding. Structures 22b and 11b propagate as a
one-dimensional zigzag polymeric sheet through C-H‚‚‚O
nonclassical intermolecular hydrogen bonding. The
importance and the nature of the nonclassical inter-
molecular hydrogen bonding have recently been de-
scribed by Desiraju.21d,e The hydrogen bonding param-
eters are given in Table 7. The intermolecular C-H‚‚‚O
and O-H‚‚‚O interactions in these structures are shown
in Figure 5. This kind of intermolecular interaction in
the cobaloxime complexes has been observed for the first
time.
Ack n ow led gm en t. We thank the Department of
Science and Technology, New Delhi, India, for funding
this project (Project No. SP/S1/F20/99).
Su p p or tin g In for m a tion Ava ila ble: This material is
available free of charge via the Internet at http://pubs.acs.org.
OM030089S
(21) (a) Bigotto, A.; Zangrando, E.; Randaccio, L. J . Chem. Soc.,
Dalton Trans. 1976, 96. (b) Geremia, S.; Dreos, R.; Randaccio, L.;
Tauzher, G.; Antolini, L. Inorg. Chim. Acta 1994, 216, 125. (c) Desiraju,
G. R.; Steiner, T. The Weak Hydrogen Bond; Oxford University Press:
New York, 1999. (d) Desiraju, G. R. Acc. Chem. Res. 2002, 35, 565. (e)
Desiraju, G. R. Acc. Chem. Res. 1991, 24, 270.