Synthesis and characterization of diphenylglyoximato cobalt(III) complexes. The molecular structures of trans-bis(diphenylglyoximato)(alkyl)(pyridine)cobalt(III), with alkyl = CH 2SiMe3, CH2CMe3 and CF3

Article abstract of DOI:10.1016/S0277-5387(03)00408-X

A series of Co(III) diphenylglyoximato (dpgh) complexes, pyCo(dpgh) ₂R, with R = Cl (2a), CH₃ (3a), CH₂Me (4a), (CH₂)₂Me (5a), (CH₂)₃Me (6a), CHMe₂ (7a), CH₂SiMe₃ (8a), CH ₂CMe₃ (9a), CH₂CH=CH₂ (10a), CH ₂Ph (11a), and CF₃ (12a) were prepared, using Co(dpgh)(dpgh₂)Cl2 (1a) as an entry to this system. The compounds were thoroughly characterized by ¹H and ¹³C NMR spectroscopy, the spectra of which were compared to the corresponding Co(III) dimethylglyoximato (DH) complexes, pyCo(DH)₂R (2b-12b). The NMR results suggest that the dpgh ligand is less electron-donating than DH. X-ray diffraction studies of complexes 8a, 9a and 12a demonstrate that subtle, but detectable structural changes occur upon substitution of dpgh for DH, due to increased interactions of the axial alkyl ligand with the equatorial ligand set.

Full text of DOI:10.1016/S0277-5387(03)00408-X

Polyhedron 22 (2003) 2809ꢁ2820
/
www.elsevier.com/locate/poly
Synthesis and characterization of diphenylglyoximato cobalt(III)
complexes. The molecular structures of trans-
bis(diphenylglyoximato)(alkyl)(pyridine)cobalt(III), with alkylꢀ
/
CH2SiMe3, CH2CMe3 and CF3
Paul J. Toscano a,*, Linda Lettko a, E. James Schermerhorn a, John Waechter a,
Kevin Shufon a, Shuncheng Liu a, Evgeny V. Dikarev a, Jon Zubieta b
a Department of Chemistry, University of Albany, State University of New York, Albany, NY 12222, USA
b Department of Chemistry, Syracuse University, Center for Science and Technology, Syracuse, NY 13244, USA
Received 12 December 2002; accepted 17 June 2003
Abstract
A series of Co(III) diphenylglyoximato (dpgh) complexes, pyCo(dpgh)2R, with Rꢀ
/Cl (2a), CH3 (3a), CH2Me (4a), (CH2)2Me
(5a), (CH2)3Me (6a), CHMe2 (7a), CH2SiMe3 (8a), CH2CMe3 (9a), CH2CHÄ
/
CH2 (10a), CH2Ph (11a), and CF3 (12a) were prepared,
1
using Co(dpgh)(dpgh2)Cl2 (1a) as an entry to this system. The compounds were thoroughly characterized by H and 13C NMR
spectroscopy, the spectra of which were compared to the corresponding Co(III) dimethylglyoximato (DH) complexes, pyCo(DH)2R
(2bꢁ12b). The NMR results suggest that the dpgh ligand is less electron-donating than DH. X-ray diffraction studies of complexes
/
8a, 9a and 12a demonstrate that subtle, but detectable structural changes occur upon substitution of dpgh for DH, due to increased
interactions of the axial alkyl ligand with the equatorial ligand set.
# 2003 Elsevier Ltd. All rights reserved.
Keywords: Cobalt(III) complexes; Cobaloximes; Diphenylglyoximato ligands; Dimethylglyoximato ligands; NMR spectroscopy; Crystal structures
1. Introduction
(dpgh)2CH2Me [4], and [MeCH2Co(dpgh)2]2(m-pyra-
zine) [7]. These reports have allowed for some beginning
structural comparisons to the more extensively studied
trans-bis(dimethylglyoximato)cobalt(III) system, LCo-
(DH)2X, where DH is the monoanion of dimethylglyox-
ime [11,12]. We note that Gupta and coworkers have
also studied cobaloxime derivatives containing mixed
equatorial ligand sets, that include one dpgh ligand and
either a DH or 1,2-cyclohexanedione dioximato ligand
Recently, there has been a resurgence of interest in the
preparation and the NMR spectroscopic characteriza-
tion of derivatives in the trans-bis(diphenylglyoxima-
to)cobalt(III) system, LCo(dpgh)2X, where dpgh is the
monoanion of diphenylglyoxime and L and X are
neutral and monoanionic ligands, respectively [1ꢁ
addition, a few X-ray structural characterizations have
been determined, including LCo(dpgh)2Cl (Lꢀpyridine
(py) [2], p-toluidine [2], or PBu3 [10]), pyCo(dpgh)2CH3
[3], 4-MepyCo(dpgh)2CH2Cl [4], P(OMe)3Co-
/9]. In
/
[13ꢁ15].
/
We have previously reported on investigations invol-
ving the effect of peripheral substitutions in the equa-
torial dioximato ligand set [16,17], as well as the effect of
perfluorination of the axial alkyl ligand [18ꢁ22], on the
chemistry and structural properties of organocobalox-
/
* Corresponding author. Tel.: ꢂ
3462.
/
1-518-442-3127; fax: ꢂ1-518-442-
/
E-mail address: ptoscano@csc.albany.edu (P.J. Toscano).
imes. In order to test whether a steric cis-influence might
0277-5387/03/$ - see front matter # 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/S0277-5387(03)00408-X

2810
P.J. Toscano et al. / Polyhedron 22 (2003) 2809ꢁ2820
/
be observable for pyCo(dpgh)2R, we felt that the R
group would either have to be large in size or have a
then cooled. The precipitated product was collected on a
filter and washed with water and diethyl ether to give
golden brown product (8.61 g, 89%). 1H NMR (CDCl3):
d 8.60 (d, 2H, a-H py), 7.83 (t, 1H, g-H py), 7.36 (t, 2H,
b-H py), 7.25 (m, 20H, dpgh phenyl). 13C NMR
very short CoꢁC bond due to electron deficiency.
/
Herein, we report on observations on improving the
yields for the preparation of pyCo(dpgh)2R complexes,
including examples where the steric and electronic
properties of the alkyl ligand R are varied more greatly
than in the previous studies. The complexes were
(CDCl3): d 153.57 (CÄN), 151.11 (a-C py), 139.33 (g-
/
C py), 129.81 (o-C dpgh), 129.65 (p-C dpgh), 129.58
(ipso-C dpgh), 127.93 (m-C dpgh), 126.04 (b-C py). The
1H and 13C NMR spectra of this compound were in
good agreement with literature values [2,3].
1
thoroughly characterized by H and 13C NMR spectro-
scopy for comparison to their DH analogs. In addition,
we have determined the solid-state structures of com-
plexes where R is either the bulky CH2SiMe3 or
CH2CMe3 ligands or the highly electron deficient CF3
ligand.
2.4. Preparation of pyCo(dpgh)2R (Rꢀ
(CH2)2Me, (CH2)3Me, CHMe2, CH2SiMe3,
CH2CMe3, CH2CHÄCH2, CH2Ph; 3aꢁ11a)
/CH3, CH2Me,
/
/
2. Experimental
Complex 2a (1.00 g, 1.53 mmol) was suspended in
methanol (50 ml) and NaOH (0.104 g, 2.60 mmol)
dissolved in water (3 ml) was added. Nitrogen was
bubbled through the resulting dark brown solution for
20 min. Then NaBH4 (0.983 g, 2.60 mmol) dissolved in
water (3 ml) was added by syringe; the solution turned
dark blue. An excess of alkylating agent (5.00 mmol; the
2.1. Materials and physical methods
1H, 13C and 19F NMR spectra were obtained with a
Varian XL-300 spectrometer at 299.9, 75.4, and 282.2
MHz, respectively. Spectra obtained in CDCl3 solution
were referenced to internal Me4Si (1H and 13C) or
internal CFCl3 (19F). We have used the designations
ipso-C dpgh (carbon atom of the phenyl substituent that
is bonded to the oxime carbon atom of the dpgh ligand),
o-C dpgh (ortho), m-C dpgh (meta), and p-C dpgh
(para) for the four types of carbon atoms in the dpgh
phenyl groups in the assignments for the 13C NMR
spectra.
corresponding alkyl iodide was employed for Rꢀ
CH2SiMe3, and CH2CMe3, while the corresponding
alkyl bromide was used for RꢀCH2Me, (CH2)2Me,
(CH2)3Me, CHMe2, CH2CHÄCH2 and CH2Ph) was
added by syringe and the solution turned light orangeꢁ
brown. After stirring for approximately 10ꢁ30 min,
/
CH3,
/
/
/
/
depending upon the identity of R, the reaction mixture
was exposed to air, and acetone (5 ml) and water (10 ml)
Diphenylglyoxime (Aldrich Chemicals), anhydrous
cobalt(II) chloride (Aldrich Chemicals), methanol and
n-butanol were used as received without further pur-
were added. Reactions times were shorter (ca. 10ꢁ
min) for the more reactive alkyl halides (RꢀCH3,
CH2CHÄCH2, and CH2Ph), in an intermediate range
(ca. 15ꢁ20 min) for less reactive cases (RꢀCH2Me,
(CH2)2Me and (CH2)3Me), and longest (ca. 25ꢁ30 min)
/
15
/
/
ification. Elemental analysis of the crystals of 12a×
/
/
/
0.125C6H6 was determined by Atlantic Microlabs (Nor-
cross, GA).
/
for the bulkier alkyl groups (CH2Me, CH2SiMe3 and
CH2CMe3). Concentration of the reaction mixture on a
2.2. Preparation of Co(dpgh)(dpgh2)Cl2 (1a)
rotary evaporator provided the orange or brownꢁ
/
orange product. Yields and NMR spectroscopic data
for the complexes follow.
A modification of the literature method [23] was
employed. Diphenylglyoxime (9.62 g, 40.1 mmol) was
placed in n-butanol (400 ml). Anhydrous cobalt(II)
chloride (2.64 g, 20.3 mmol) was added and the mixture
was heated and stirred overnight in the presence of air.
The resulting dark brown solution was concentrated on
a rotary evaporator. The dark residue was thoroughly
washed with water and ethanol and air dried to give
brown product (10.7 g, 88%).
Rꢀ
CH3 (3a); yield 0.822 g (84.9%); 1H NMR
/
(CDCl3): d 8.92 (d, 2H, a-H py), 7.83 (t, 1H, g-H py),
7.44 (t, 2H, b-H py), 7.22 and 7.11 (m, 20H, dpgh
phenyl), 1.44 (s, 3H, Coꢁ
/
CH3). 13C NMR (CDCl3): d
150.78 (CÄN), 149.99 (a-C py), 137.99 (g-C py), 129.94
/
(ipso-C dpgh), 129.60 (o-C dpgh), 128.94 (p-C dpgh),
127.83 (m-C dpgh), 125.58 (b-C py).
Rꢀ
CH2Me (4a); yield 0.692 g (69.9%); 1H NMR
/
(CDCl3): d 8.92 (d, 2H, a-H py), 7.83 (t, 1H, g-H py),
7.44 (t, 2H, b-H py), 7.22 and 7.10 (m, 20H, dpgh
/
2.3. Preparation of pyCo(dpgh)2Cl (2a)
phenyl), 2.34 (q, 2H, Coꢁ
/
CH2CH3), 0.82 (t, 3H, Coꢁ
Complex 1a (9.00 g, 14.8 mmol) was heated and
stirred in 80% methanol/water (240 ml:60 ml). When
dissolution was complete, pyridine (2.40 g, 30.4 mmol)
was added. The mixture was heated and stirred for 1 h,
CH2CH3). 13C NMR (CDCl3): d 150.80 (CÄ
/
N), 150.10
(a-C py), 137.86 (g-C py), 130.09 (ipso-C dpgh), 129.62
(o-C dpgh), 128.91 (p-C dpgh), 127.83 (m-C dpgh),
125.51 (b-C py), 16.16 (CH2CH3).

P.J. Toscano et al. / Polyhedron 22 (2003) 2809ꢁ
/2820
2811
1
(CH2)2Me (5a); yield 0.767 g (75.8%); H NMR
Rꢀ
/
7.41 (t, 2H, b-H py), 6.90ꢁ
/
7.35 (complex, 25H, dpgh
CH2). 13C NMR
(CDCl3): d 8.92 (d, 2H, a-H py), 7.84 (t, 1H, g-H py),
phenyl and CH2Ph), 3.44 (s, 2H, Coꢁ
/
7.44 (t, 2H, b-H py), 7.22 and 7.09 (m, 20H, dpgh
(CDCl3): d 151.01 (CÄN), 150.16 (a-C py), 147.33 (ipso-
/
phenyl), 2.22 (m, 2H, Coꢁ
CH2CH2CH3), 0.99 (t, 3H, Coꢁ
NMR (CDCl3): d 150.85 (CÄN), 150.04 (a-C py),
/
CH2), 1.46 (m, 2H, Coꢁ
/
C benzyl), 137.93 (g-C py), 129.93 (ipso-C dpgh), 129.66
(o-C dpgh), 129.13 (o-C benzyl), 128.89 (p-C dpgh),
128.29 (m-C benzyl), 127.65 (m-C dpgh), 125.52 (b-C
py), 124.71 (p-C benzyl).
/
CH2CH2CH3). 13C
/
137.85 (g-C py), 130.08 (ipso-C dpgh), 129.62 (o-C
dpgh), 128.91 (p-C dpgh), 127.83 (m-C dpgh), 125.49 (b-
C
py), 24.07 (Coꢁ
CH2CH2CH3).
Rꢀ(CH2)3Me (6a); yield 0.809 g (78.3%); H NMR
/
CH2CH2CH3), 15.20 (Coꢁ
/
2.5. Preparation of pyCo(dpgh)2CF3 (12a)
1
/
To a solution of 2a (2.00 g, 3.07 mmol) and NaOH
(0.40 g, 10.0 mmol) in degassed methanol (100 ml) under
nitrogen was added NaBH4 (0.370 g, 9.74 mmol)
dissolved in water (3 ml). The solution was stirred for
10 min, followed by the addition of degassed acetone (5
ml). After 5 min, CF3Br was briefly bubbled through the
solution three times. The solution turned from dark blue
to brown and was stirred for 20 min after the last CF3Br
addition. The reaction mixture was then opened to air
and acetone (15 ml) and water (10 ml) were added. The
solution volume was concentrated on a rotary evapora-
tor and the product was collected. The crude material
was dissolved in acetone (40 ml) to which was added
pyridine (5 drops) and water (15 ml). Slow evaporation
in air gave the purified product (1.10 g, 52%). 1H NMR
(CDCl3): d 8.86 (d, 2H, a-H py), 7.91 (t, 1H, g-H py),
7.49 (t, 2H, b-H py), 7.25 and 7.11 (m, 20H, dpgh
(CDCl3): d 8.92 (d, 2H, a-H py), 7.84 (t, 1H, g-H py),
7.44 (t, 2H, b-H py), 7.22 and 7.09 (m, 20H, dpgh
/
phenyl), 2.23 (m, 2H, Coꢁ
CH2CH2CH2CH3), 0.93 (t, 3H, Coꢁ
13C NMR (CDCl3): d 150.84 (CÄ
N), 150.06 (a-C py),
/
CH2), 1.41 (br m, 4H, Coꢁ
/
CH2CH2CH2CH3).
/
137.86 (g-C py), 130.11 (ipso-C dpgh), 129.60 (o-C
dpgh), 128.90 (p-C dpgh), 127.85 (m-C dpgh), 125.50 (b-
C py), 33.25 (Coꢁ
CH2CH2CH2CH3), 14.10 (Coꢁ
Rꢀ
CHMe2 (7a); yield 0.716 g (72.4%); 1H NMR
/
CH2CH2CH2CH3), 23.80 (Coꢁ
/
/CH2CH2CH2CH3).
/
(CDCl3): d 8.91 (d, 2H, a-H py), 7.79 (t, 1H, g-H py),
7.40 (t, 2H, b-H py), 7.21 and 7.09 (m, 20H, dpgh
/
phenyl), 2.63 (septet, 1H, Coꢁ
/
CH), 0.89 (d, 6H, Coꢁ
CHMe2). 13C NMR (CDCl3): d 151.08 (CÄ
/N), 149.91
(a-C py), 137.78 (g-C py), 130.14 (ipso-C dpgh), 129.50
(o-C dpgh), 128.86 (p-C dpgh), 127.84 (m-C dpgh),
125.42 (b-C py), 26.42 (Coꢁ
/
CHMe2).
phenyl). 13C NMR (CDCl3): d 152.60 (CÄ
N), 149.96 (a-
/
1
RꢀCH2SiMe3 (8a); yield 0.744 g (68.9%); H NMR
/
C py), 138.90 (g-C py), 129.53 (o-C dpgh), 129.49 (p-C
dpgh), 129.41 (ipso-C dpgh), 127.96 (m-C dpgh), 125.90
(CDCl3): d 8.86 (d, 2H, a-H py), 7.81 (t, 1H, g-H py),
7.41 (t, 2H, b-H py), 7.22 and 7.09 (m, 20H, dpgh
/
(b-C py). 19F NMR (CDCl3): d ꢃ
/31.82 (s, CF3).
phenyl), 1.07 (s, 2H, Coꢁ
/
CH2), 0.11 (s, 9H, Coꢁ
CH2SiMe3). 13C NMR (CDCl3): d 151.35 (CÄ
/N),
149.55 (a-C py), 137.99 (g-C py), 129.97 (ipso-C
dpgh), 129.68 (o-C dpgh), 128.94 (p-C dpgh), 127.81
2.6. Preparation of pyCo(DH)2R (Rꢀ
CH2Me, (CH2)2Me, (CH2)3Me, CHMe2, CH2SiMe3,
CH2CMe3, CH2CHÄCH2, CH2Ph, CF3; 3aꢁ12a)
/Cl, CH3,
(m-C dpgh), 125.47 (b-C py), 1.22 (Coꢁ
/
CH2SiMe3).
1
/
/
RꢀCH2CMe3 (9a); yield 0.753 g (71.4%); H NMR
/
(CDCl3): d 8.89 (d, 2H, a-H py), 7.81 (t, 1H, g-H py),
7.41 (t, 2H, b-H py), 7.20 and 7.06 (m, 20H, dpgh
These organocobalt complexes were prepared by
standard literature procedures [19,24,25]. Full NMR
spectroscopic data follow.
phenyl), 2.34 (s, 2H, Coꢁ
/
CH2), 1.10 (s, 9H, Coꢁ
/
CH2CMe3). 13C NMR (CDCl3): d 151.68 (CÄ
/
N),
Rꢀ
/
Cl (2b); H NMR (CDCl3): d 8.27 (d, 2H, a-H
1
149.51 (a-C py), 137.84 (g-C py), 130.15 (ipso-C
dpgh), 129.53 (o-C dpgh), 128.90 (p-C dpgh), 127.83
(m-C dpgh), 125.38 (b-C py), 38.05 (Co-CH2CMe3),
31.08 (CoCH2CMe3).
py), 7.72 (t, 1H, g-H py), 7.24 (t, 2H, b-H py), 2.40 (s,
12H, DHꢁ N),
CH3). 13C NMR (CDCl3): d 152.58 (CÄ
151.04 (a-C py), 138.97 (g-C py), 125.67 (b-C py), 13.09
(DHꢁCH3).
RꢀCH3 (3b); H NMR (CDCl3): d 8.61 (d, 2H, a-H
py), 7.73 (t, 1H, g-H py), 7.33 (t, 2H, b-H py), 2.13 (s,
12H, DHꢁCH3), 0.81 (s, 3H, Coꢁ
CH3). 13C NMR
(CDCl3): d 150.06 (a-C py), 148.98 (CÄN), 137.48 (g-C
py), 125.21 (b-C py), 11.98 (DHꢁCH3).
CH2Me (4b); H NMR (CDCl3): d 8.60 (d, 2H,
a-H py), 7.71 (t, 1H, g-H py), 7.32 (t, 2H, b-H py), 2.13
(s, 12H, DHꢁCH3), 1.74 (q, 2H, CoꢁCH2CH3), 0.36 (t,
3H, Coꢁ
CH2CH3). 13C NMR (CDCl3): d 150.10 (a-C
py), 149.01 (CÄN), 137.34 (g-C py), 125.16 (b-C py),
15.91 (CH2CH3), 11.95 (DHꢁCH3).
/
/
/
1
Rꢀ
/
CH2CHÄ
/
CH2 (10a); yield 0.850 g (84.3%); 1H
/
NMR (CDCl3): d 8.88 (d, 2H, a-H py), 7.82 (t, 1H, g-H
py), 7.43 (t, 2H, b-H py), 7.23 and 7.11 (m, 20H, dpgh
/
/
phenyl), 6.07 (m, 1H, CHÄ
CHÄCH2), 2.91 (d, 2H, Coꢁ
d151.15 (CÄN), 150.18 (a-C py), 144.35 (CHÄ
/
CH2), 5.30 (complex, 2H,
CH2). 13C NMR (CDCl3):
CH2),
/
/
/
/
1
/
/
Rꢀ
/
137.95 (g-C py), 130.17 (ipso-C dpgh), 129.65 (o-C
dpgh), 128.94 (p-C dpgh), 127.79 (m-C dpgh), 125.55 (b-
/
/
C py), 112.08 (CHÄ
RꢀCH2Ph (11a); yield 0.551 g (50.8%); H NMR
(CDCl3): d 8.86 (d, 2H, a-H py), 7.81 (t, 1H, g-H py),
/CH2).
/
1
/
/
/

2812
P.J. Toscano et al. / Polyhedron 22 (2003) 2809ꢁ2820
/
Rꢀ
a-H py), 7.71 (t, 1H, g-H py), 7.31 (t, 2H, b-H py), 2.12
(s, 12H, DHꢁCH3), 1.62 (m, 2H, CoꢁCH2), 0.98 (m,
2H, CoꢁCH2CH2CH3), 0.79 (t, 3H, CoꢁCH2CH2CH3).
13C NMR (CDCl3): d 149.96 (a-C py), 149.10 (CÄ
N),
137.35 (g-C py), 125.13 (b-C py), 23.88 (Coꢁ
CH2CH2CH3), 14.82 (CoꢁCH2CH2CH3), 12.02 (DHꢁ
CH3).
Rꢀ
a-H py), 7.72 (t, 1H, g-H py), 7.32 (t, 2H, b-H py), 2.13
(s, 12H, DHꢁCH3), 1.64 (m, 2H, CoꢁCH2), 1.19 (m,
2H, CoꢁCH2CH2CH2CH3), 0.89 (m, 2H, Coꢁ
CH2CH2CH2CH3), 0.80 (t, 3H, CoꢁCH2CH2CH2CH3).
13C NMR (CDCl3): d 149.96 (a-C py), 149.12 (CÄ
N),
137.39 (g-C py), 125.16 (b-C py), 33.01 (Coꢁ
CH2CH2CH2CH3), 23.69 (CoꢁCH2CH2CH2CH3),
13.97 (CoꢁCH2CH2CH2CH3), 12.02 (DHꢁCH3).
RꢀCHMe2 (7b); H NMR (CDCl3): d 8.59 (d, 2H,
a-H py), 7.69 (t, 1H, g-H py), 7.29 (t, 2H, b-H py), 2.13
(s, 12H, DHꢁCH3), 1.94 (septet, 1H, CoꢁCH), 0.47 (d,
6H, Coꢁ
CHMe2). 13C NMR (CDCl3): d 150.01 (a-C
py), 149.30 (CÄN), 137.21 (g-C py), 125.04 (b-C py),
26.33 (CoꢁCHMe2), 12.00 (DHꢁCH3).
RꢀCH2SiMe3 (8b); H NMR (CDCl3): d 8.55 (d,
2H, a-H py), 7.69 (t, 1H, g-H py), 7.29 (t, 2H, b-H py),
2.12 (s, 12H, DHꢁCH3), 0.45 (s, 2H, CoꢁCH2), ꢃ0.15
(s, 9H, Coꢁ
CH2SiMe3). 13C NMR (CDCl3): d 149.68
(a-C py), 149.59 (CÄN), 137.42 (g-C py), 125.14 (b-C
py), 12.10 (DHꢁCH3), 0.54 (CoꢁCH2SiMe3).
RꢀCH2CMe3 (9b); H NMR (CDCl3): d 8.56 (d,
2H, a-H py), 7.69 (t, 1H, g-H py), 7.28 (t, 2H, b-H py),
2.11 (s, 12H, DHꢁCH3), 1.73 (s, 2H, CoꢁCH2), 0.78 (s,
9H, Coꢁ
CH2CMe3). 13C NMR (CDCl3): d 149.54 (a-C
py), 149.94 (CÄN), 137.84 (g-C py), 125.05 (b-C py),
36.84 (CoꢁCH2CMe3), 30.64 (CoꢁCH2CMe3), 12.04
(DHꢁCH3).
RꢀCH2CHÄ
(d, 2H, a-H py), 7.71 (t, 1H, g-H py), 7.30 (t, 2H, b-H
py), 5.67 (m, 1H, CHÄCH2), 4.92 (complex, 2H, CHÄ
CH2), 2.30 (d, 2H, CoꢁCH2), 2.15 (s, 12H, DHꢁCH3).
13C NMR (CDCl3): d 150.17 (a-C py), 149.41 (CÄ
N),
145.17 (CHÄCH2), 137.45 (g-C py), 125.22 (b-C py),
110.54 (CHÄCH2), 12.41 (DHꢁCH3).
RꢀCH2Ph (11b); H NMR (CDCl3): d 8.55 (d, 2H,
a-H py), 7.69 (t, 1H, g-H py), 7.28 (t, 2H, b-H py), 6.95ꢁ
7.15 (complex, 5H, CH2Ph), 2.85 (s, 2H, CoꢁCH2), 1.95
(s, 12H, DHꢁ
CH3). 13C NMR (CDCl3): d 150.27 (a-C
py), 149.33 (CÄN), 147.41 (ipso-C benzyl), 137.40 (g-C
py), 128.71 (o-C benzyl), 127.42 (m-C benzyl), 125.17
(b-C py), 124.09 (p-C benzyl), 11.91 (DHꢁCH3).
Rꢀ
CF3 (12b) [19]; 1H NMR (CDCl3): d 8.54 (d, 2H,
a-H py), 7.78 (t, 1H, g-H py), 7.35 (t, 2H, b-H py), 2.20
(s, 12H, DHꢁ
CH3). 13C NMR (CDCl3): d 151.38 (CÄ
N), 149.82 (a-C py), 138.44 (g-C py), 125.54 (b-C py),
12.24 (DHꢁ 32.34 (s,
CH3). 19F NMR (CDCl3): d ꢁ
CF3).
/
(CH2)2Me (5b); 1H NMR (CDCl3): d 8.60 (d, 2H,
2.7. X-ray crystallography
/
/
Orange octahedral prisms of compounds 8a and 9a
were obtained by slow evaporation of saturated acet-
/
/
/
oneꢂ
/
water solutions at 0ꢁ5 8C. Under the same condi-
/
/
tions, compound 12a invariably produced twinned
crystals. In one crystallization attempt, a small amount
of benzene was serendipitously added to an acetoneꢂ
water solution of 12a. The crystals of 12a obtained at 0ꢁ
5 8C were a benzene solvate. Subsequent X-ray crystal
studies (vide infra) and elemental analyses established
that approximately 1/8 (one-eighth) of a benzene
molecule was present for each molecule of 12a in the
crystals. Anal. Calc. for C34H27CoF3N5O4Co×
0.125C6H6: C, 60.03; H, 4.02; N, 10.07. Found: C,
60.28; H, 4.21; N, 10.10%.
X-ray intensity data for 8a and 9a were measured at
173(2) K (Bruker KRYOꢁ
APEX CCD-based X-ray diffractometer system
˚
equipped with a Mo-target X-ray tube (lꢀ0.71073 A)
operated at 1800 W power. The detector was placed at a
distance of 6.14 cm from the crystals.
/
/
/
/
(CH2)3Me (6b); 1H NMR (CDCl3): d 8.59 (d, 2H,
/
/
/
/
/
/
/
/
/
/
/
/
1
/
/
FLEX) on a Bruker SMART
/
/
/
/
/
/
/
A total of 1850 frames were collected for each crystal
with a scan width of 0.38 in v and an exposure time of
20 s/frame. The frames were integrated with the Bruker
SAINT software package using a narrow-frame integra-
tion algorithm. The final unit cell constants are based
upon the refinement of the XYZ-centroids of 9966 and
6950 reflections above 20s(I) for 8a and 9a, respectively.
The unit cells of 8a and 9a were found to be isomor-
phous. Analysis of the data showed negligible decay
during data collection for both compounds. Data were
corrected for absorption effects using the empirical
multiscan method (SADABS). The structures of 8a and
9b were solved by Patterson methods and refined by full
1
/
/
/
/
/
/
/
/
1
/
/
/
/
/
/
/
/
matrix least-squares procedures on jF2j with SHELXTL
-
1
/
/
CH2 (10b); H NMR (CDCl3): d 8.56
97, version 6.12 [26]. All non-hydrogen atoms were
refined anisotropically. All hydrogen atoms were lo-
cated and refined. Crystal data and further data collec-
tion parameters are summarized in Table 1.
/
/
/
/
/
X-ray intensity data for 12a×
sured on a Bruker R3m diffractometer in the v ꢁ
mode with variable scan speed (3ꢁ
208 minꢃ1) and
/
0.125C6H6 were mea-
/
/
2u
/
/
/
1
/
graphite monochromated Mo Ka radiation (lꢀ
/
˚
0.71073 A). Data were corrected for background,
/
/
attenuators, Lorentz and polarization effects in the
usual fashion, but not for absorption [27]; atomic
scattering factors were taken from the literature [28].
Structure solution via Patterson methods and full-
matrix least-squares refinements on jFj were accom-
plished with the SHELXTL PLUS package of programs.
The space group was determined to be C2/c rather than
Cc via successful solution in the former. The asymmetric
/
/
/
/
/
/
unit for 12a×
/
0.125C6H6 contains two crystallographi-
/
/
cally independent molecules of pyCo(dpgh)2CF3. In
addition, a benzene molecule is situated at a center of

P.J. Toscano et al. / Polyhedron 22 (2003) 2809ꢁ
/2820
2813
Table 1
Crystallographic data and parameters for 8a, 9a and 12a×
/0.125C6H6
8a
9a
12a×
/
0.125C6H6
Formula
Formula weight
Crystal color
C37H38CoN5O4Si
703.7
C38H38CoN5O4
687.7
C34H27CoF3N5O4×0.125C6H6
/
1390.6
orange
plate
orange
octahedral prism
orange
octahedral prism
Habit
Crystal dimensions (mm3)
Temperature (K)
Crystal system
Space group
0.16ꢄ
173(2)
monoclinic
/
0.19ꢄ
/
0.20
0.20ꢄ
173(2)
monoclinic
/
0.50ꢄ
/
0.70
0.20ꢄ
293(2)
monoclinic
/
0.25ꢄ0.60
/
P21/n (No. 14)
P21/n (No. 14)
C2/c (No. 15)
Unit cell dimensions
˚
a (A)
˚
11.4436(5)
20.2746(9)
14.6975(6)
90
11.4843(6)
19.9348(11)
14.6643(8)
90
51.27(2)
11.246(2)
26.763(7)
90
b (A)
˚
c (A)
a (8)
b (8)
g (8)
99.1580(10)
90
99.0310(10)
90
120.54(2)
90
3
˚
V (A )
3366.6(3)
4
1.388
3315.6(3)
4
1.378
13290(7)
16
Z
Dcalc (g cmꢃ3
)
1.390
0.574
438
m (Mo Ka) (mmꢃ1
F(000)
)
0.594
1472
0.567
1440
umax (8)
28.28
29175
28.28
28666
25.0
12891
Reflections collected
Independent reflections
Observed reflections
Tmin/Tmax
7928 (Rint
ꢀ
2.0s(I))
/
2.08%)
7804 (Rint
ꢀ
/
3.18%)
11205 (Rint
ꢀ/0.96%)
7059 (Iꢀ
0.891/0.911
585
/
6295 (I ꢀ
0.915/0.967
585
/
2.0s(I))
5463 (Fꢀ 6.0s(F))
n/a
523
/
Number of parameters
R1 a, wR2 (I ꢀ
b
/2.0s(I))
0.0337, 0.0931
0.0379, 0.0958
n/a
0.0424, 0.1029
0.0565, 0.1099
n/a
n/a
n/a
R1 a, wR2 (all data)
b
c
R
wR
0.0756
0.0939
2.50 f
d
n/a
1.057 e
n/a
1.035 e
GOF
a
R1ꢀ
/
SjjFojꢃ
wR2ꢀ
[S w(Fo2ꢃ
Rꢀ
SjjFojꢃ
wRꢀ
[S w(jFojꢃ
GOFꢀ
GOFꢀ
/
jFcjj/SjFoj.
b
c
d
e
f
/
/
Fc2)2/S w(Fo2)2]1/2; wꢀ
/
1/[s2(Fo2)ꢂ
/
(aP)2ꢂ
bP].
/
/
/
jFcjj/SjFoj.
/
/
jFcj)2/S wjFoj2]1/2; wꢀ
/
1/s2(Fo)ꢂg(Fo)2.
/
/
[S w(Fo2ꢃFc2)2/(Nobs Nparams)]1/2, based on F2 for all data.
ꢃ
[S w(jFojꢃ
/
/
/
/ jFcj)2/(Nobs
ꢃ
Nparams)]1/2, based on F for all data.
/
symmetry (the benzene ring centroid is at (1/2, 0, 0)).
The three crystallographically independent carbon
atoms of the benzene molecule at this site were modelled
at only one half occupancy, in accord with the empirical
formula derived from elemental analysis of the crystals
of 12a (vide supra). Thus, the unit cell of these crystals
contains sixteen cobalt complexes of 12a and two
benzene solvates (that is, four benzene molecules at
half occupancy each). Thus, we arrive at the empirical
hydrogen atom positions for the disordered benzene
solvate and for the oxime groups were neither located
nor calculated. Crystal data and further data collection
parameters are summarized in Table 1.
3. Results and discussion
3.1. Synthesis
formula, pyCo(dpgh)2CF3×
/
0.125C6H6. All non-hydro-
gen atoms in the dpgh chelate rings, the pyridine ligand
and the CF3 ligand, as well as the cobalt atom, for both
We chose Co(dpgh)(dpgh2)Cl2 (1a) as our entry into
the bis(diphenylglyoximato)cobalt(III) series by analogy
to the successful application of Co(DH)(DH2)Cl2 (1b) as
a convenient starting material for bis(dimethylglyoxi-
mato)cobalt(III) complexes [24]. We prepared 1a by a
modification of the literature method [23]. Complex 1a
was converted to pyCo(dpgh)2Cl (2a) by a procedure
that was straightforwardly derived from the correspond-
crystallographically independent molecules of 12a×
/
0.125C6H6 were refined anisotropically. Carbon atoms
in the phenyl substituents of the dpgh ligands were
refined as rigid groups. Hydrogen atom positions for
12a×
/
0.125C6H6 were calculated geometrically, fixed at a
˚
CꢁH distance of 0.96 A, and not refined, except that the
/

2814
P.J. Toscano et al. / Polyhedron 22 (2003) 2809ꢁ2820
/
ing dimethylglyoximato chemistry [24]. We note that 2a
has previously been prepared by direct air oxidation of
CoCl2 in the presence of diphenylglyoxime and pyridine
in n-butanol [23], as well as by addition of pyridine to
(H2O)Co(dpgh)2Cl [2].
shifts within the equatorial ligand sets, then proceed to
consider chemical shifts for the axial pyridine and alkyl
ligands.
3.2.1. Equatorial ligands
For the DH series of compounds, pyCo(DH)2R, it has
1
been noted previously that the H NMR chemical shift
The syntheses of pyCo(dpgh)2R, where Rꢀ
CH2Me (4a), (CH2)2Me (5a), (CH2)3Me (6a), CHMe2
(7a), CH2SiMe3 (8a), CH2CMe3 (9a), CH2CHÄCH2
/CH3 (3a),
/
of the DHꢁCH3 group moves to lower field as the
/
(10a), and CH2Ph (11a), involved reduction of 2a with
excess NaBH4 to form the [pyCo(dpgh)2]ꢃ anion,
followed by the addition of the corresponding alkyl
bromide or iodide and differed only in minor respects to
the previously reported method for the preparation of
electron-donating ability of the axial anionic ligand
decreases [11]. This trend is evident here for compounds
2b (Rꢀ
/
Cl), 10b (Rꢀ
/
CH2CHÄ
/
CH2) and 12b (Rꢀ
/
CF3). There is little change in the chemical shift of this
resonance for DH complexes having axial hydrocarbyl
ligands, with the exception of compound 11b, where
pyCo(dpgh)2R (Rꢀ
isolated yields were reproducibly in the good to excellent
range (70ꢁ85%), with the exception of RꢀCH2Ph
/CH3, CH2Me) [3]. However, our
1
CH2Ph. Here, an anomalously high field H NMR
Rꢀ
/
/
/
resonance for the DHꢁ
/
CH3 groups is observed, due to
(51%), and were significantly higher in most cases than
those previously reported in preparations of py-
ring-current effects originating from the coordinated
benzyl ligand.
1
The H NMR spectra of the organometallic diphe-
Co(dpgh)2R (Rꢀ
/
CH3, CH2Me, (CH2)2Me, (CH2)3Me,
67% [3,6]; RꢀCH2Ph: 70% [29]).
We found that prolonged reaction times in the presence
CHMe2; range: 19ꢁ
/
/
nylglyoximato cobalt(III) complexes 3aꢁ
Co(dpgh)2R, generally have pair of complex
multiplets in the region of d 7.05ꢁ7.25 that are
assignable to the dpgh phenyl protons [2,3,6,14]. The
only exception was nonorganometallic complex 2a (Rꢀ
/
12a, py-
a
of the excess NaBH4 led to the undesired reduction of
/
the
organometallic
product
to
reform
the
[pyCo(dpgh)2]ꢃ anion, as evinced by the reappearance
of the blue color of the reduced cobalt intermediate. The
desired organometallic compounds could be reobtained
by the addition of more alkylating agent; however, the
need for such action was avoided by judiciously
quenching the reaction with acetone after shorter
reaction times in order to avoid the undesired reduction.
Attempts to prepare pyCo(dpgh)2CF3 (12a) by meth-
ods analogous to those that worked well for py-
Co(DH)2CF3 [19], viz. reduction of 2a with less than
stoichiometric amounts of NaBH4 in order to prevent
replacement of fluorine by hydrogen in the coordinated
alkyl ligand of the organometallic product, were un-
successful. The product so obtained under these condi-
tions was contaminated by considerable amounts of
paramagnetic impurities as judged by extremely broad
1H NMR resonances for the product. Instead, we chose
to reduce 2a with an excess of NaBH4 and quench the
unreacted NaBH4 with acetone after the formation of
the blue, reduced cobalt intermediate. Subsequent addi-
tion of CF3Br, followed by recrystallization of the crude
product, gave pure 12a in respectable yield (52%).
/
Cl), for which both dpgh phenyl multiplets overlap each
other at about d 7.25. This suggests that the upfield
multiplet for 2a is shifted approximately 0.16 ppm
downfield from the average value for the same reso-
nance in the organometallic dpgh derivatives, 3aꢁ12a.
/
Previously, the multiplet at higher field was assigned to
the ortho protons (o-H) of the dpgh phenyl groups [2,3].
The observed downfield shift of this resonance for 2a
lends credence to this notion, since the displacement is in
the same direction as the somewhat larger downfield
change (ca. 0.27 ppm) that is observed for the 1H NMR
chemical shift for the DHꢁ
2b versus compounds 3bꢁ
series of compounds 3aꢁ12a, however, there was very
/
CH3 resonance of compound
/9b (vida supra). Within the
/
little variation in the chemical shifts of either dpgh
multiplet as a function of the axial alkyl ligand (R),
surprisingly even for Rꢀ
/
CH2CHÄ/CH2 (10a) or CF3
(12a). Presumably, no variation was observed here for
the putative dpgh o-H multiplet due to the relative
remoteness of the dpgh o-H atoms from the axial alkyl
ligand.
Assignments for the 13C NMR resonances for the
dpgh phenyl groups were based upon previous determi-
nations for diphenylglyoximato cobalt(III) complexes
[3], as well as a close examination of the 13C chemical
shifts for substituted benzene molecules [30]. The 13C
chemical shift for the dpgh ipso-C fell in the range d
3.2. NMR spectroscopic comparisons
1
Full H and 13C NMR spectral data can be found in
the Experimental Section for the diphenylglyoximato
cobalt(III) complexes 2aꢁ/12a, as well as for the
analogous dimethylglyoximato series 2bꢁ
/
12b. Spectra
were remeasured if complete data were not available in
130.059
except 2a (Rꢀ
resonance appeared at higher field. In the DH series,
the DHꢁ13
CH3 resonance occurs at d 12.0090.10 for
most of the organometallic complexes, with the excep-
/
0.12 for all the diphenylglyoximato complexes,
/
Cl) and 12a (RꢀCF3), where this
/
the literature. In general, good agreement with pre-
viously reported spectral values was observed [1ꢁ
3,6,11,14]. We will discuss first the trends in chemical
/
/
/

P.J. Toscano et al. / Polyhedron 22 (2003) 2809ꢁ
/2820
2815
tion of those for 10b (Rꢀ
/
CH2CHÄ
/
CH2) and 11b (Rꢀ
/
that are slightly different than the other organometallic
complexes with the b-H(py) and g-H(py) shifts approxi-
mately 0.06 and 0.10 ppm to lower field from the typical
ranges, respectively.
CH2Ph), probably due to ring-current and anisotropy
effects. For the chloro derivative (2b) and other com-
plexes with poor electron-donating alkyl groups, such as
CF3 (12b), the DHꢁ13
/
CH3 resonance is observed at
Interestingly, however, the changes in 1H chemical
shift for the a-H(py), b-H(py) and g-H(py) of the
pyridine ligand for each pair of corresponding com-
plexes in the dpgh and DH series are virtually constant
as a function of R. More specifically, the replacement of
the DH equatorial ligand set with the dpgh ligand set
produces downfield shifts for the a-H(py), b-H(py) and
/
lower fields [11]. At this time, we have no explanation
for the reversal of the trends for the cis-influence of R
on dpgh ipso-13C versus equatorial DHꢁ13
CH3 chemical
/
shifts.
We also observed rather little variation in the 13C
chemical shifts for the dpgh o-C (d 129.5990.09), dpgh
m-C (d 127.8290.04), and dpgh p-C atoms (d 128.909
/
/
/
g-H(py) resonances of 0.329
/
0.01, 0.129
/
0.02 and 0.119
0.03) as a function of R for the majority of the
pyCo(dpgh)2R complexes. Notable values outside of
0.02 ppm, respectively, no matter the identity of R. The
downfield shifts, particularly those for the remote g-H
atom of the pyridine ligand where ring-current effects
from the phenyl substituents of the dpgh ligands should
be minimal, can be taken as tentative evidence for less
electron donation by the dpgh ligand set versus the DH
ligand set.
these ranges include: (a) 2a (RꢀCl) where the dpgh
/
o-13C, dpgh m-13C, and dpgh p-13C resonances were
approximately 0.20, 0.10 and 0.75 ppm downfield from
the above ranges, respectively, (b) 11a (RꢀCH2Ph)
/
where the dpgh m-13C resonance is approximately 1.0
ppm downfield and the dpgh p-13C resonance is at
The 13C chemical shift for the a-C(py) was virtually
unchanged upon substitution of dpgh for DH. However,
the 13C resonances for the b-C(py) and particularly the
g-C(py), which has been employed as an indicator for
electron-donating ability of the trans ligand [10],
slightly lower field, and (c) 12a (RꢀCF3) where the
/
dpgh m-13C and dpgh p-13C chemical shifts are
approximately 0.14 and 0.60 ppm downfield. It appears
that both electronic and through-space ring current
effects are responsible for these results.
appeared respectively at 0.359
ppm to lower field for the dpgh derivatives (with the
exception of RꢀCl in the case of the g-C(py)). These
/
0.03 and 0.529
/
0.06
Within both series of cobalt complexes, the 13C
chemical shift for the oxime (CÄ
/N) carbon of the
/
equatorial ligand set appears to be affected by both
electronic and steric effects [11]. For all axial anionic
observations are similar to those involving the 1H
chemical shifts for the pyridine ligand in these two
series and again suggest poorer electron donation by the
dpgh ligand set. Further, we can likely exclude ring
current effects, at the very least for the g-13C resonance
of the pyridine ligand, since we would expect these
carbon atoms to be well-distanced from the dpgh phenyl
substituents.
ligands except Rꢀ
/
Cl and CF3, the 13C resonance for
the CÄN moiety in the dpgh ligand set occurs 1.749
/
/
0.06
ppm downfield from the position observed in the
corresponding DH series. The reasons for the anom-
alous chemical shifts for RꢀCl and CF3 are not known,
/
but the behavior is not surprising in view of the behavior
of other 13C NMR resonances in the equatorial ligand
set for these two axial anionic ligands (vide supra).
Finally, we consider NMR chemical shifts for the
axial alkyl ligand in the organometallic complexes. It
has previously been observed for a smaller number of
complexes that a substitution of dpgh for DH caused
3.2.2. Axial ligands
We now consider NMR chemical shifts for the axial
pyridine ligand. In both the dpgh and DH series of
complexes, little variation in chemical shift is observed
0.599
/
0.05 and 0.4690.02 ppm downfield shifts for the
/
1H resonances of hydrogen atoms attached to the a-C
and b-C atoms of the alkyl chain, respectively [3]. We
have found that these ranges generally hold true for
alkyl ligands having vastly different substituents, with
some small exceptions. We also observe that the shift to
lower field for the dpgh derivatives decreases as the
hydrogen atom in question is more remotely located
along the alkyl chain; for the hydrogen atoms on the g-C
atoms of the chain, the dpgh derivatives resonate only
1
within each series for the H NMR resonances of the a-
H(py), b-H(py) and g-H(py) of the coordinated pyridine
ligand. For the diphenylglyoximato complexes 3aꢁ
/
11a,
0.03, 7.429
0.03, respectively, while for the DH
series, compounds 3bꢁ11b, they occur at d 8.5890.04,
7.3090.03 and 7.7190.02, respectively. The only com-
the shifts for these protons occur at d 8.899
/
/
0.02 and 7.819
/
/
/
/
/
pounds that do not conform to these chemical shift
ranges are once again the chloro derivatives (2a and 2b)
and the CF3 derivatives (12a and 12b). In the chloro
complexes, the chemical shifts for the a-H(py) and the b-
H(py) are approximately 0.30 and 0.06 ppm upfield,
respectively, from the ranges for the other compounds in
the two series. The CF3 complexes have 1H NMR shifts
approximately 0.269
their DH analogs, excluding CH2CHÄ
slightly out of this range. In the one case where there are
protons on a d-C (Rꢀ(CH2)3Me), the methyl resonance
for the dpgh compound is 0.13 ppm to lower field than
that for the corresponding resonance in the DH com-
plex. Curiously, the difference in 19F chemical shifts for
/
0.06 ppm further downfield than
/CH2 which is
/

2816
P.J. Toscano et al. / Polyhedron 22 (2003) 2809ꢁ2820
/
the complexes with Rꢀ
/
CF3 in the two series also nearly
respective cobalt complex (Figs. 1 and 2). As such,
bond lengths and angles within the coordination spheres
of 8a and 9a correspond quite closely (Table 2). Bond
lengths and angles within the equatorial dpgh ligand sets
conforms to the range found for hydrogen atoms.
Unfortunately, the 13C NMR resonance for the a-C
of the axial alkyl ligand could not be observed accu-
rately due to broadening by the 59Co quadrupole. In
general, the b-13C, g-13C and d-13C resonances of the
alkyl ligands were at lower field in the dpgh compounds
as compared to the DH complexes. One notable
exception was the allyl complexes (11a and 11b), where
the b-C resonance was 0.82 ppm to higher field for the
dpgh complex, while the g-C resonance was 1.54 ppm to
lower field. The ipso-13C resonance for the benzyl ligand
in the dpgh series was also slightly upfield to that of the
corresponding DH complex. Presumably, we are again
observing the effect of p-electron anisotropies on the
chemical shifts. Further excellent discussion and insights
on variations in the chemical shifts for alkyl ligands in
the dpgh series have been reported [6,14].
are unexceptional and within expected ranges [2ꢁ
As expected, the axial CoꢁC bonds in 8a and 9a are
significantly longer than the CoꢁCH3 bond lengths
found for pyCo(dpgh)2CH3 (1.997(4) A; [3]) and 4-
/4,7,10].
/
/
˚
˚
MepyCo(dpgh)2CH2Cl (2.011(6) A; [4]). The axial Coꢁ
/
N(py) bond lengths for 8a and 9a are comparable to
those observed for these same two previously studied
compounds [3,4].
We now turn to structural comparisons of the
diphenylglyoximato cobalt(III) complexes 8a and 9a to
the corresponding dimethylglyoximato cobalt(III) com-
plexes 8b and 9b [31]. Along the axial direction, there is
relatively little difference in bond lengths or angles
involving the Co atom and the axial py and alkyl
ligands, with the exception of the CoꢁN(py) axial bond
/
length being somewhat shorter for 8a versus 8b (Table
3).
3.3. Structural studies
However, the maintenance of these structural para-
meters involving the axial ligands apparently comes at a
slight cost. For the dimethylglyoximato complexes 8b
and 9b, the Co atom is essentially situated in the plane
defined by the four nitrogen donor atoms of the oxime
ligands, while there is a slight bending of the dimethyl-
glyoximato chelate planes away from the bulky alkyl
The solid-state structures of compounds 8a, 9a, and
12a were studied via single crystal X-ray diffraction
methods. These compounds were chosen because either
the alkyl ligands have significant steric bulk (8a and 9a)
or because a very short CoꢁC bond was expected (12a).
/
In either case, we hoped to maximize potential steric
interactions between the equatorial dpgh ligand set and
the axial alkyl ligand. Previous structural determina-
tions on bis(diphenylglyoximato) cobalt(III) complexes
have involved relatively small, anionic ligands, such as
ligands (Table 3). The projection of the Coꢁ
the alkyl ligand for 8b and 9b on the equatorial ligand
plane is coincident with a CoꢁN(oxime) bond, while the
/C bond of
/
plane defined by the py ligand nearly bisects the Oꢀ ꢀ ꢀO
vectors of the dioximato ligands [31]. These latter
observations are quite usual for pyCo(DH)2R com-
Cl, CH3, CH2Me and CH2Cl [2ꢁ4,7,10].
The asymmetric units of 8a and 9a, which are
isomorphous, contain one discrete molecule of the
/
Fig. 1. Molecular structure and atom numbering scheme for 8a. Hydrogen atoms have been omitted for clarity.

P.J. Toscano et al. / Polyhedron 22 (2003) 2809ꢁ
/2820
2817
Fig. 2. Molecular structure and atom numbering scheme for 9a. Hydrogen atoms have been omitted for clarity.
plexes containing the Coꢁ/CH2X moiety, where X is an
so that the projection of the CoꢁC bond is now
/
alkyl substituent [11,12]. Indeed, the plane of the
pyridine ligand bisects the Oꢀ ꢀ ꢀO vectors of the diphe-
nylglyoximato ligands for pyCo(dpgh)2CH3 [3] and 4-
MepyCo(dpgh)2CH2Cl [4] also.
coincident with the plane of the axial py ligand. The
chelate ring on the side of the diphenylglyoximato
complexes, under which the substituent of the alkyl
ligand resides (defined by N(1), C(7), C(8), and N(2)), is
On the other hand, for the diphenylglyoximato
complexes 8a and 9a, the py ligand is rotated approxi-
bent somewhat more towards the py ligand (ꢃ
and ꢁ4.1(1)8 for 8a and 9a, respectively) than the other
chelate ring (defined by N(3), C(21), C(22) and N(4); ꢃ
2.8(1) and ꢃ2.1(1)8 for 8a and 9a, respectively) as
judged by the dihedral angles made by these planes to
the equatorial plane. The cobalt atom moves slightly out
of the equatorial plane towards the alkyl group and the
overall bending of the dpgh chelate rings away from the
alkyl ligand increases slightly (Table 3). The implication
is that the large alkyl ligands sterically interact with the
equatorial ligand set in the diphenylglyoximato series
/
4.5(1)
/
mately 17ꢁ
vectors of the dioximato ligands; further, the alkyl
ligand is rotated away from the CoꢁN(oxime) bonds
/
18(1)8 from the plane that bisects the Oꢀ ꢀ ꢀO
/
/
/
Table 2
Selected bond lengths (A) and bond angles (8) for 8a and 9a
˚
8a
9a
Bond lengths
Co(1)ꢁ
Co(1)ꢁ
Co(1)ꢁ
Co(1)ꢁ
Co(1)ꢁ
Co(1)ꢁ
/
N(1)
N(2)
N(3)
N(4)
N(5)
C(34)
1.896(1)
1.887(1)
1.877(1)
1.874(1)
2.059(1)
2.037(1)
1.892(2)
1.885(2)
1.882(1)
1.871(1)
2.079(2)
2.078(2)
/
/
Table 3
/
Structural comparisons between pyCo(dpgh)2CH2SiMe3 (8a)/py-
Co(DH)2CH2SiMe3 (8b) and pyCo(dpgh)2CH2CMe3 (9a)/py-
Co(DH)2CH2CMe3 (9b)
/
/
Bond angles
N(1)ꢁCo(1)ꢁ
N(1)ꢁCo(1)ꢁ
N(1)ꢁCo(1)ꢁ
N(1)ꢁCo(1)ꢁ
N(1)ꢁCo(1)ꢁ
N(2)ꢁCo(1)ꢁ
N(2)ꢁCo(1)ꢁ
N(2)ꢁCo(1)ꢁ
N(2)ꢁCo(1)ꢁ
N(3)ꢁCo(1)ꢁ
N(3)ꢁCo(1)ꢁ
N(3)ꢁCo(1)ꢁ
N(4)ꢁCo(1)ꢁ
N(4)ꢁCo(1)ꢁ
N(5)ꢁCo(1)ꢁ
a
Parameter
8a
8b
9a
9b a
/
/
N(2)
N(3)
N(4)
N(5)
C(34)
N(3)
N(4)
N(5)
C(34)
N(4)
N(5)
C(34)
N(5)
C(34)
C(34)
81.40(5)
179.31(5)
98.76(5)
89.86(5)
95.17(5)
98.31(5)
178.78(5)
89.83(5)
90.65(6)
81.51(5)
89.51(5)
85.46(5)
88.96(5)
90.53(6)
174.96(5)
81.38(6)
178.03(7)
99.11(6)
89.14(5)
96.83(5)
98.07(5)
178.43(5)
90.21(5)
91.04(6)
81.40(5)
88.98(5)
85.06(5)
88.30(5)
90.38(6)
174.02(5)
/
/
˚
N(py), (A)
˚
C (A)
Coꢁ
/
2.059(1)
2.091(5)
2.079(2)
2.081(4)
2.060(6)
174.7(2)
127.38(8) b 127.7(7) b 129.8(1) c 130.3(4) c
/
/
Coꢁ
/
2.037(1)
2.031(6)
2.078(2)
/
/
N(py)ꢁ
/
Coꢁ
/
C (8) 174.96(5)
174.1(2)
174.02(5)
/
/
Coꢁ
d
/
Cꢁ
/X (8)
d
e
/
/
˚
(A)
ꢃ
/
0.028
0.00
1.2
ꢃ
/
0.015
0.00
5.2
/
/
a
(8)
ꢃ
/
7.3
ꢃ/
ꢃ
/
6.2
ꢃ/
/
/
a
b
c
/
/
Ref. [31].
XꢀSi.
XꢀC.
Displacement of the Co atom out of the plane defined by the four
/
/
/
/
/
/
d
/
/
/
/
equatorial oxime nitrogen atoms; positive values indicate displacement
towards the py ligand.
/
/
e
/
/
Interplanar angle between the planes defined by the dioximato
chelate rings; positive values indicate bending away from the py ligand.

2818
P.J. Toscano et al. / Polyhedron 22 (2003) 2809ꢁ2820
/
Table 4
peripheral phenyl substituents (Fig. 3 depicts molecule 1
of the asymmetric unit). In addition, the asymmetric
unit contains half of a benzene molecule, which was
modelled at half site occupancy (see Section 2). Because
of the fair quality of the crystallographic data, due in
part to the presence of the benzene solvate, discussion
on the 12a molecules will be limited. Bond lengths and
angles within the coordination spheres (Table 4) and
within the dpgh ligand sets of both molecules are
˚
Selected bond lengths (A) and bond angles (8) for 12a×
/
0.125C6H6
Molecule 1
Molecule 2
Bond lengths
Co(1)ꢁ
Co(1)ꢁ
Co(1)ꢁ
Co(1)ꢁ
Co(1)ꢁ
Co(1)ꢁ
/
N(1)
N(2)
N(3)
N(4)
N(5)
C(34)
1.867(7)
1.882(7)
1.891(6)
1.870(7)
2.040(9)
1.926(14)
1.883(8)
1.894(8)
1.886(8)
1.904(8)
2.049(8)
1.948(13)
/
/
/
/
/
comparable and are as expected [2ꢁ
/
4,7,10,19]. The short
Bond angles
N(1)ꢁCo(1)ꢁ
N(1)ꢁCo(1)ꢁ
N(1)ꢁCo(1)ꢁ
N(1)ꢁCo(1)ꢁ
N(1)ꢁCo(1)ꢁ
N(2)ꢁCo(1)ꢁ
N(2)ꢁCo(1)ꢁ
N(2)ꢁCo(1)ꢁ
N(2)ꢁCo(1)ꢁ
N(3)ꢁCo(1)ꢁ
N(3)ꢁCo(1)ꢁ
N(3)ꢁCo(1)ꢁ
N(4)ꢁCo(1)ꢁ
N(4)ꢁCo(1)ꢁ
N(5)ꢁCo(1)ꢁ
CoꢁC bond lengths are accompanied by an elongation
of the tetrahedra around C(34) (independent molecule 1)
and C(34?) (independent molecule 2) as evinced by the
/
/
/
N(2)
N(3)
N(4)
N(5)
C(34)
N(3)
N(4)
N(5)
C(34)
N(4)
N(5)
C(34)
N(5)
C(34)
C(34)
82.3(3)
179.5(4)
98.6(3)
87.0(3)
90.5(4)
97.6(3)
179.1(3)
90.1(4)
89.6(4)
81.5(3)
92.5(3)
90.0(4)
90.1(4)
90.3(4)
177.5(4)
81.4(4)
178.7(5)
99.2(4)
88.9(3)
88.8(4)
97.8(4)
179.2(3)
90.4(3)
90.5(5)
81.5(3)
90.1(3)
92.3(4)
89.3(3)
89.8(5)
177.3(4)
/
/
/
/
summation of the Fꢁ
/
Cꢁ/F and the summation of the
/
/
CoꢁCꢁF bond angles, respectively (Table 5). These
/
/
/
/
/
/
observations have been interpreted as arising from a
combination of electrostatic and hybridization altera-
tions due to the electronegative fluorine substituents
[32,33]. The situation is entirely analogous to that found
for 12a [19].
/
/
/
/
/
/
/
/
/
/
/
/
Comparisons of relevant bonding parameters (Table
5) for the two independent molecules of 12a versus 12b
[19] reveal that there are some small differences between
the diphenylglyoximato and dimethylglyoximato com-
plexes. The cobalt atom has moved from slightly
towards the py ligand out of the equatorial ligand plane
for 12b to slightly on the alkyl side of this plane for the
12a molecules; concurrently, the equatorial ligand set
bends away from the alkyl ligands for both 12a
molecules, rather than away from the py ligand as for
12b. The py ligands for both molecules of 12a are
rotated slightly (ca. 5(1)8) from the plane that bisects the
Oꢀ ꢀ ꢀO vectors of the dioximato ligands. Otherwise, there
are no major differences and the remainder of the
important bonding parameters are comparable for
both 12a and 12b.
/
/
/
/
/
/
somewhat more than in the dimethylglyoximato series,
leading to these subtle, but detectable structural differ-
ences. While crystal packing effects on these structural
parameters can not be entirely excluded [11,12], we note
that the molecules appear to be well separated; for
instance, there are no long range intermolecular inter-
actions between phenyl substituents in 8a and 9a.
The asymmetric unit of 12a×
crystallographically independent molecules of 12a, that
differ only slightly in the rotational configurations of the
/0.125C6H6 contains two
Fig. 3. Molecular structure and atom numbering scheme for crystallographically independent molecule 1 for 12a. The numbering scheme for
independent molecule 2 of 12a is identical, except that a ‘prime’ is attached to the atom labels. Hydrogen atoms have been omitted for clarity.

P.J. Toscano et al. / Polyhedron 22 (2003) 2809ꢁ
/2820
2819
Table 5
Structural comparisons between pyCo(dpgh)2CF3 (12a)/py-
Co(DH)2CF3 (12b)
of the axial py ligands and increases in the bending of
the equatorial chelate rings. Much less dramatic, but still
similarly detectable structural alterations occur for 12a
12a (molecule 1) 12a (molecule 2) 12b a
(RꢀCF3). Such steric effects involving diphenylglyox-
/
Parameter
imato vis-a`-vis dimethylglyoximato cobalt(III) com-
plexes likely have some impact on the more favorable
˚
N(py) (A)
Coꢁ
Coꢁ
/
2.040(9)
1.926(14)
2.049(8)
1.948(13)
2.043(3)
1.949(4)
˚
C (A)
/
exo/endo selectivity observed in DielsꢁAlder reactions
/
N(py)ꢁ
S CoꢁCꢁ
CꢁF (8)
/
Coꢁ
/
C (8) 177.5(4)
350.8
302.9
177.3(4)
344.1
311.1
177.4(2)
346.0
308.9
of bis(diphenylglyoximato)cobalt-substituted diene
complexes [34], as well as on increased rates of oxygen
insertion [29] and increased rates of ligand substitution
/
/
F (8)
S Fꢁ
/
/
b
c
˚
d
(A)
(8)
ꢃ0.004
/
ꢃ0.010
/
ꢂ
/
0.002
a
ꢃ2.9
/
ꢃ3.6
/
ꢂ
/
3.0
for complexes of dpgh [35ꢁ37].
/
a
Ref. [19].
Displacement of the Co atom out of the plane defined by the four
b
equatorial oxime nitrogen atoms; positive values indicate displacement
towards the py ligand.
5. Supplementary material
c
Interplanar angle between the planes defined by the dioximato
chelate rings; positive values indicate bending away from the py ligand.
Crystallographic data for the structural analysis,
including atomic coordinates, bond lengths and angles
and anisotropic thermal parameters have been deposited
with the Cambridge Crystallographic Data Centre,
CCDC Nos. 199118, 199119 and 199120 for compounds
4. Conclusions
8a, 9a and 12a×
information may be obtained free of charge from
The Director, CCDC, 12 Union Road, Cambridge,
CB2 1EZ, UK (fax:
deposit@ccdc.cam.ac.uk or www: http://www.ccdc.cam.
ac.uk).
/
0.125C6H6, respectively. Copies of this
In summary, we can conclude that the diphenylglyox-
imato cobalt(III) complexes are not optimal for the
elucidation of cis and trans influences in this class of
cobalt complex by NMR techniques, since there are a
number of mitigating factors, such as ring current and
electronic effects, that can contribute to the observed
chemical shifts as discussed by Gupta and coworkers [6].
However, the NMR data suggest that no unusually large
steric interactions occur between the dpgh phenyl
substitutents and the axial ligands. For example, many
NMR resonances for the pyridine ligand shift downfield
in the dpgh series vs. the DH series by exactly the same
amount, regardless of the steric or electronic nature of
the trans anionic ligand. The same is true in a general
sense for the chemical shift trends for the axial alkyl
ligands. While ring current contributions to the chemical
shifts can not be ignored, it appears overall that the
dpgh ligand is not as good an electron-donating ligand
as DH, as judged by the shift to lower fields for many
comparable resonances in the axial and equatorial
ligands in the dpgh series as compared to the DH
analogs that should not be affected appreciably by ring
currents.
ꢂ44-1223-336033; e-mail:
/
Acknowledgements
We thank the University at Albany Faculty Research
Award Program (P.J.T.) for partial financial support.
P.J.T. and E.V.D. thank the National Science Founda-
tion for funding the CCD diffractometer (CHE-
0130985) at the University at Albany.
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