Preparation of an aquocobaloxime 1,3-dienyl complex and its Diels-Alder reactions in water and organic solvents

Article abstract of DOI:10.1021/om040010z

Cobaloxime complex [(H₂O)(dimethylglyoxime)₂Co(I)] (generated in situ) reacts with an allenic electrophile to produce 1,3-butadien-2-yl(H₂O)bis(dimethylglyoximato)cobalt(III). This dienyl complex (which has also been characterized by X-ray crystallography) reacts with a number of dienophiles in both water and organic solvents.

Full text of DOI:10.1021/om040010z

Organometallics 2004, 23, 2257-2262
2257
P r ep a r a tion of a n Aqu ocoba loxim e 1,3-Dien yl Com p lex
a n d Its Diels-Ald er Rea ction s in Wa ter a n d Or ga n ic
Solven ts
Carmen J . Tucker, Mark E. Welker,* Cynthia S. Day, and Marcus W. Wright
Department of Chemistry, Wake Forest University, P.O. Box 7486,
Winston-Salem, North Carolina 27109
Received J anuary 21, 2004
Cobaloxime complex [(H2O)(dimethylglyoxime)2Co(I)] (generated in situ) reacts with an
allenic electrophile to produce 1,3-butadien-2-yl(H2O)bis(dimethylglyoximato)cobalt(III). This
dienyl complex (which has also been characterized by X-ray crystallography) reacts with a
number of dienophiles in both water and organic solvents.
In tr od u ction
to allow the formation of η3-butadienyl cobaloxime com-
plexes or even possibly insertion chemistry. We report
our investigation of both of those possibilities.
Our group1 and the Tada group2 independently re-
ported the preparation and Diels-Alder reactions of
pyridine cobaloxime dienyl complexes over 10 years ago.
Since that time, we have reported a number of synthetic
routes to these and other related types of cobalt dienyl
complexes as well as their subsequent cycloaddition and
demetalation chemistry,3,4 and other groups have now
made use of the cycloadducts thus prepared5 as well as
the methodology.6 We have not previously prepared one
of these complexes that had enough water solubility to
permit Diels-Alder chemistry of these complexes to be
explored in that solvent. Here, we report an optimized
preparation of 1,3-butadien-2-yl(H2O)bis(dimethylgly-
oximato)cobalt(III) (1) as well as its X-ray crystal-
lographic characterization and Diels-Alder chemistry.
We first prepared aquocobaloxime 1,3-diene (1) by
generating the cobaloxime anion in situ in aqueous
methanol followed by treatment of that anion with
4-tosyl-1,2-butadiene.1 The red, air-stable aquo dienyl
complex (1) could be isolated, but the yield was dis-
appointing (15%), and a side product (9%) resulting from
the nucleophilic addition of a dimethylglyoxime hy-
droxyl to the allenic electrophile (with resulting dis-
placement of the tosylate) (CH3C(dNOH)C(dNOCH2-
CHdCdCH2)CH3) was also isolated. We soon discovered
that running these reactions in aqueous methanol with
the addition of alkylamines resulted in much higher
isolated yields of the aquo complex 1 and eliminated side
product formation. Isolated yields of complex 1 were
27% and 36%, respectively, when diethyl- and diisoprop-
ylamines were used as the additives and reproducibly
improved to nearly 50% when triethylamine was used.
It should be pointed out that the aquo dienyl complex 1
crystallizes from the aqueous methanol upon standing
at 0 °C, so the isolated yields reported require no
purification other than a simple filtration.
Resu lts a n d Discu ssion
Alkyl-substituted aquocobaloxime complexes were
first prepared in the 1960s.7 They were reported to have
moderate water solubility, and while the methyl aquo-
cobaloxime complex could be dehydrated without de-
composition, water removal from higher alkyl homo-
logues did not prove as facile. The water ligand in these
complexes was easily replaced by phosphines, nitrogen
heterocycles, and sulfides. We became interested in the
preparation of an aquocobaloxime 1,3-dienyl complex for
two reasons. We believed this complex might have
enough water solubility to allow cobaloxime dienyl
complex Diels-Alder reactions to be performed in water,
and we thought the water ligand might be labile enough
* Corresponding author. E-mail: welker@wfu.edu. Fax: (336)-758-
4321.
(1) Smalley, T. L.; Wright, M. W.; Garmon, S. A.; Welker, M. E.;
Rheingold, A. L. Organometallics 1993, 12, 998-1000.
(2) Tada, M.; Shimizu, T. Bull. Chem. Soc. J pn. 1992, 65, 1252-
1256.
(3) Pickin, K. A.; Kindy, J . M.; Day, C. S.; Welker, M. E. J .
Organomet. Chem. 2003, 681, 120-133.
(4) Welker, M. E. Curr. Org. Chem. 2001, 5, 785-807.
(5) Miyaki, Y.; Onishi, T.; Ogoshi, S.; Kurosawa, H. J . Organomet.
Chem. 2000, 616, 135-139.
The 1H and 13C NMR characteristics of the diene
fragment of this aquo dienyl complex were similar to
those of pyridine and substituted pyridine cobaloxime
dienes we have reported previously.8-12 The X-ray
crystallographic data of diene 1 shows a diene torsional
(6) Chai, C. L. L.; J ohnson, R. C.; Koh, J . Tetrahedron 2002, 58,
975-982.
(7) Windgassen, G. N. S. R. J . J . Am. Chem. Soc. 1966, 88, 3738-
3743.
10.1021/om040010z CCC: $27.50 © 2004 American Chemical Society
Publication on Web 04/16/2004

2258 Organometallics, Vol. 23, No. 10, 2004
Tucker et al.
F igu r e 1. View of a molecule of Co[C4H7N2O2]2(C4H5)-
(H2O) from the crystal structure showing the numbering
scheme employed. Anisotropic atomic displacement el-
lipsoids for the non-hydrogen atoms are shown at the 50%
probability level. Hydrogen atoms are displayed with an
arbitrarily small radius. Hydrogen bonding interactions are
represented by double dashed lines.
F igu r e 2. View of a molecule of Co[C4H7N2O2]2(C9H9O3)-
(EtOH) from the crystal structure showing the numbering
scheme employed. Anisotropic atomic displacement el-
lipsoids for the non-hydrogen atoms are shown at the 50%
probability level. Hydrogen atoms are displayed with an
arbitrarily small radius. Hydrogen bonding interactions are
represented by double dashed lines.
Ta ble 1. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for Co[C4H7N2O2]2(C4H5)(H2O)
case is shown. The major citraconic anhydride regio-
isomer was also characterized by X-ray crystallography
(Figure 2; selected bond lengths and angles, Table 3).
The regiochemistry of the major cycloadduct from the
reaction with methyl vinyl ketone was proven by NMR
spectroscopy. The fact that the citraconic anhydride
cycloaddition was somewhat regioselective (Co&Me
meta:Co&Me para 1.6:1) is unusual given the fact that
other electron-rich organic dienes, such as substituted
furans, have been reported to react with citraconic
anhydride to yield 1:1 mixtures of regioisomers.14,15
Similary, a thermal cycloaddition between isoprene and
citraconic anhydride performed in our laboratory pro-
duced a 1.05:1 mixture of meta:para regioisomers.
One of the original rationales for making these com-
plexes (other than their water solubility and ability to
participate in aqueous Diels-Alder chemistry) was the
hope that the water ligand would prove labile enough
to allow η3-dienyl complex isolation or insertion chem-
istry. The isolation of the ethanol complex from the etha-
nol recrystallization of the citraconic anhydride adduct
4 also gave us cause to attempt dehydration of the
dienyl complex 1 as well as the maleic anhydride 2 and
dimethyl fumarate 3 cycloadducts. A variety of methods
(heating in a variety of solvents with different dehy-
drating agents such as sieves of differing sizes, MgSO4,
Co-C10
C9-C10
C11-C12
1.962(3)
1.471(10)
1.325(9)
Co-O5
C10-C11
C10-Co-O5
2.026(2)
1.313(11)
177.7(4)
C11-C10-Co
C10-C11-C12
119.2(6)
126.4(7)
C9-C10-Co
C11-C10-C9
118.9(5)
121.7(4)
angle of 30.0° and a Co-C bond length of 1.962(3) Å.
The Co-carbon bond in this complex is short compared
to most of the other dienyl complexes we have reported
previously,13 and this manifests itself in a diene torsion
angle smaller than any we have noted previously. The
ORTEP of this complex is provided in Figure 1, and a
partial listing of bond lengths and angles is provided
in Table 1.
If the solid state diene torsion angle parallels the
solution angle, then one would predict these dienes to
be quite reactive in Diels-Alder chemistry. We found
this to be true. We screened four different dienophiles,
maleic anhydride, dimethyl fumarate, citraconic anhy-
dride, and methyl vinyl ketone, in [4 + 2] cycloaddition
chemistry (Table 2). All four reacted to produce high
yields of cycloadduct in organic solvents, and the non-
anhydride dienophiles also cyclized well in water. Maleic
anhydride and dimethyl fumarate cyclized to produce
the single diastereomers shown. Citraconic anhydride
and methyl vinyl ketone cyclized to produce regio-
isomers, and the major regioisomer produced in each
i
CF3CO2 Pr) were attempted for removal of the coordi-
nated water from 1 and attempted isolation of an η3-
dienyl complex, but none produced a new complex. The
aquo dienyl complex 1 was reisolated in all cases. Like-
wise, heating the water coordinated cycloadducts 2 and
3 under CO or ethylene failed to yield any new com-
plexes.
(8) Stokes, H. L.; Welker, M. E. Organometallics 1996, 15, 2624-
2632.
(9) Richardson, B. M.; Welker, M. E. J . Org.Chem. 1997, 62, 1299-
1304.
(10) Wright, M. W.; Welker, M. E. J . Org. Chem. 1996, 61, 133-
141.
(11) Stokes, H. L.; Richardson, B. M.; Wright, M. W.; Vaughn, S.
M.; Welker, M. E.; Liablesands, L.; Rheingold, A. L. Organometallics
1995, 14, 5520-5532.
(12) Wright, M. W.; Smalley, T. L.; Welker, M. E.; Rheingold, A. L.
J . Am. Chem. Soc. 1994, 116, 6777-6791.
(13) Pickin, K. A.; Day, C. S.; Wright, M. W.; Welker, M. E. Acta
Crystallogr. Sect. C 2003, 59, M193-M195.
In summary, a new water-soluble cobaloxime 1,3-
dienyl complex (1) has been prepared and characterized
(14) Murali, R.; Rao, H. S. P.; Scheeren, H. W. Tetrahedron 2001,
57, 3165-3174.
(15) Beusker, P. H.; Aben, R. W. M.; Seerden, J . P. G.; Smits, J . M.
M.; Scheeren, H. W. Eur. J . Org. Chem. 1998, 2483-2492.

Aquocobaloxime 1,3-Dienyl Complex
Organometallics, Vol. 23, No. 10, 2004 2259
Ta ble 2. Diels-Ald er Ch em istr y of Com p lex 1
Ta ble 3. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for Co[C4H7N2O2]2(C9H9O3)(EtOH)
were obtained using a Bruker 300 MHz spectrometer operating
at 75.48 MHz. All spectra were referenced to the residual
proton or carbon signals of the respective deuterated solvents.
Infrared (IR) spectra were obtained on a Mattson Genesis II
FT IR. Melting points were recorded using a Mel-Temp
apparatus and are reported uncorrected. All elemental analy-
ses were performed by Atlantic Microlabs, Inc. in Norcross,
GA. High-resolution mass spectrometry was performed at the
Duke University Mass Spectrometry Facility in Durham, NC.
Microwave reactions were carried out using a Discover micro-
wave system from CEM Corporation. All reactions were
performed under a dry nitrogen atmosphere. Tetrahydrofuran
was distilled under nitrogen from sodium/benzophenone im-
mediately prior to use. Pentane was distilled under nitrogen
from calcium hydride, prior to use. Dimethylglyoxime was
purchased from Aldrich and recrystallized from 95% ethanol
(12 mL/g) prior to use. Sodium borohydride, isopropyl trifluo-
roacetate, maleic anhydride, dimethyl fumarate, citraconic
anhydride, and methyl vinyl ketone were purchased from
Aldrich. Amines were purchased from Aldrich or Fisher. Cobalt
acetate tetrahydrate and cobalt chloride hexahydrate were
purchased from Strem. Allenic tosylate, 4-tosyl-1,2-butadiene,
was prepared according to a known literature procedure.12,16
Syn t h esis of 1,3-Bu t a d ien -2-yl(w a t er )b is(d im et h yl-
glyoxim a to)coba lt(III) (1). Cobalt acetate tetrahydrate (1.56
g, 6.25 mmol) and dimethylglyoxime (dmg) (1.45 g, 12.5 mmol)
were stirred under a dry nitrogen atmosphere in degassed
methanol (25 mL) for 1 h. Potassium hydroxide (0.715 g, 12.75
mmol) in degassed water (2.14 mL) was added, and the
Co-C10
1.947(10)
1.340(13)
1.488(12)
1.443(14)
1.537(16)
1.484(15)
0.83(8)
Co-O8
2.051(7)
C9-C10
C10-C11
C12-C17
C12-C15
C13-C14
O8-H8O
C9-C14
1.493(14)
1.658(15)
1.506(15)
1.458(17)
1.413(12)
178.4(4)
C11-C12
C12-C13
C13-C16
O8-C18
C10-Co-O8
C16-O5-C15
C9-C10-C11
C11-C10-Co
C17-C12-C13
C13-C12-C15
C13-C12-C11
C16-C13-C14
C14-C13-C12
O6-C15-O5
111.3(11)
C10-C9-C14
C9-C10-Co
123.7(10)
122.5(7)
109.3(8)
116.3(9)
121.1(8)
117.8(11)
106.2(11)
111.8(8)
110.9(11)
117.4(10)
120.5(16)
105.8(13)
127(2)
C10-C11-C12
C17-C12-C15
C17-C12-C11
C15-C12-C11
C16-C13-C12
C13-C14-C9
O6-C15-C12
O7-C16-O5
109.5(10)
105.9(10)
104.8(9)
104.4(12)
105.9(10)
133.6(19)
121.2(16)
112.2(14)
O5-C15-C12
O7-C16-C13
O5-C16-C13
by a variety of spectroscopic techniques in addition to
X-ray crystallography. This dienyl complex reacts with
a variety of dienophiles in Diels-Alder reactions in
organic solvents as well as in water.
Exp er im en ta l Section
Gen er a l P r oced u r es. Proton nuclear magnetic resonance
(1H NMR) spectra were obtained using a Bruker Avance 300
MHz spectrometer operating at 300.1 MHz or a Bruker 500
MHz spectrometer operating at 500.1 MHz. 13C NMR spectra
(16) Chapman, J . J .; Welker, M. E. Organometallics 1997, 16, 747-
755.

2260 Organometallics, Vol. 23, No. 10, 2004
Tucker et al.
reaction mixture was cooled in an ice bath. After the contents
of the flask were chilled, 4-tosyl-1,2-butadiene (1.54 g, 6.88
mmol) was added. Sodium borohydride (0.150 g, 3.96 mmol)
and potassium hydroxide (0.013 g, 0.22 mmol) in degassed
water (5 mL) was added dropwise over 1 h. The reaction
mixture was filtered, and the filtrate volume was reduced by
one-half on a rotary evaporator. The mixture was diluted back
up to full volume with degassed water and stored at ap-
proximately 4 °C overnight. Filtration of the reaction mixture
revealed a mixture of red crystals (1) and white solid. The
white solid was removed via chloroform in which the red
crystals were not soluble, and it proved to have NMR char-
acteristics consistent with the product of the nucleophilic
addition of a dimethylglyoxime hydroxyl to the allenic elec-
trophile (with resulting SN2 displacement of the tosylate)
(CH3C(dNOH)C(dNOCH2CHdCdCH2)CH3): 1H NMR (CD-
Cl3): 5.37 (p, J ) 6.8 Hz, 1H), 4.82 (dt, J ) 6.6, 2.4 Hz, 2H),
4.67 (dt, J ) 7.0, 2.4 Hz, 2H), 2.08 (s, 3H), 2.02 (s, 3H). 13C
NMR (CDCl3): 209.6, 155.6, 153.7, 87.3, 75.8, 72.2, 10.1, 9.3.
The red crystals (1) were collected and dried under vacuum
Hz, 1H), 2.50 (d, J ) 16.5 Hz, 1H), 2.38 (ddd, J ) 14.7, 7.5,
1.6 Hz, 1H), 2.15 (s, 6H), 2.12 (s, 6H), 2.10 (m, 1H), 1.69 (m,
1H). 13C NMR (d8-THF): 175.4, 174.8, 152.1, 151.8, 138.9,
128.6, 42.2, 42.2, 31.0, 26.5, 12.0, 11.7. IR (NaCl): 3405, 1776,
1681, 1193 cm-1. Anal. Calcd for C16H23CoN4O8: C, 41.93; H,
5.06. Found: C, 41.27; H, 5.21. FAB HRMS (m/z) calcd for
C
16H22CoN4O7 (M - H2O + H+), 441.0820, found (M - H2O +
H+), 441.0824.
Syn th esis of Diels-Ald er Ad d u ct 2 a t Room Tem p er -
a tu r e. 1,3-Butadien-2-yl(water)bis(dimethylglyoximato)cobalt-
(III) (1) (0.300 g, 0.833 mmol) was added to distilled, degassed
THF (9 mL) and allowed to stir for several minutes. Maleic
anhydride (0.109 g, 1.110 mmol) was added, and the reaction
mixture was allowed to stir for 6 h at room temperature, under
an atmosphere of dry nitrogen. Solvent was removed using a
rotary evaporator, and the orange solid was washed with
several portions of pentane/anhydrous diethyl ether (50:50) to
remove excess, unreacted maleic anhydride. The solid was
dried under vacuum (0.371 g, 0.809 mmol, 97% yield) and was
identical by spectroscopic comparison to the material isolated
above.
1
(0.328 g, 0.91 mmol, 15.0% yield). Mp: 140 °C dec. H NMR
(d8-THF): 18.50 (bs, 2H), 6.23 (dd, J ) 16.9, 10.5 Hz, 1H),
4.73 (dd, J ) 16.7, 2.8 Hz, 1H), 4.39 (dd, J ) 10.5, 3.1 Hz,
1H), 4.23 (s, 1H), 3.89 (bs, 1H), 2.54 (bs, 2H), 2.15 (s, 12H).
13C NMR (d8-THF): 151.4, 145.9, 114.7, 107.6, 11.8. IR
(NaCl): 3010, 2359, 2341, 1201, 1145 cm-1. Anal. Calcd for
Syn th esis of Diels-Ald er Ad d u ct 2 by Micr ow a ve. 1,3-
Butadien-2-yl(water)bis(dimethylglyoximato)cobalt(III) (1) (0.050
g, 0.139 mmol) was dissolved in distilled, degassed THF (3 mL)
in a microwavable tube. Maleic anhydride (0.027 g, 0.277
mmol) was added, and the tube was sealed under an atmo-
sphere of dry nitrogen. The reaction mixture was run in the
microwave at 75 °C for 5 min. Solvent was removed by rotary
evaporation, and the remaining red-orange solid was washed
with several portions of a pentane/anhydrous diethyl ether
solution (50:50). The product was placed under high vacuum
to dry (0.060 g, 0.131 mmol, 96% yield) and was identical by
spectroscopic comparison to the material isolated above.
Diels-Ald er Ad d u ct of 1 fr om Dim eth yl F u m a r a te
Dien op h ile: Ad d u ct 3. 1,3-Butadien-2-yl(water)bis(dimeth-
ylglyoximato)cobalt(III) (1) (0.100 g, 0.278 mmol) was added
to distilled, degassed THF (5 mL) in a thick walled pressure
tube. Dimethyl fumarate (0.080 g, 0.555 mmol) was added, and
the pressure tube was sealed with the reaction mixture under
an atmosphere of dry nitrogen. The tube was heated to 100
°C for 24 h in a silicon oil bath. The solvent was removed via
rotary evaporation, and the remaining red-orange solid was
washed with several portions of a pentane/anhydrous diethyl
ether solution (50:50). The product was dried under vacuum
(0.133 g, 0.264 mmol, 94% yield). Mp: 205 °C dec. 1H NMR
(d8-THF): 18.44 (bs, 2H), 4.83 (bs, 1H), 3.54 (s, 3H), 3.51 (s,
3H), 2.56 (td, J ) 10.8, 5.1 Hz, 1H), 2.48 (td, J ) 10.9, 5.8 Hz,
1H), 2.25 (m, 1H), 2.23 (m, 1H), 2.17 (s, 12H), 2.07 (m, 1H),
1.74 (m, 1H). 13C NMR (d8-THF): 175.4, 175.1, 151.6, 151.5,
123.3, 51.4, 51.4, 44.5, 42.9, 35.5, 30.7, 11.8. IR (NaCl): 3732,
2359, 2341, 1684, 1204 cm-1. Anal. Calcd for C18H29CoN4O9:
C, 42.86; H, 5.80. Found: C, 42.84; H, 5.89.
Syn th esis of Diels-Ald er Ad d u ct 3. 1,3-Butadien-2-yl-
(water)bis(dimethylglyoximato)cobalt(III) (1) (0.100 g, 0.278
mmol) was added to distilled, degassed THF (5 mL) in a thick
walled pressure tube. Dimethyl fumarate (0.080 g, 0.555 mmol)
was added, and the tube was sealed. The reaction was allowed
to stir under a dry nitrogen atmosphere for 3 days. The solvent
was removed by rotary evaporation, and the solid was washed
with several portions of a pentane/anhydrous diethyl ether
solution (50:50). The red-orange product was dried under
vacuum (0.139 g, 0.276 mmol, 97% yield) and was identical
by spectroscopic comparison to the material reported above.
Syn t h esis of Diels-Ald er Ad d u ct 3 Usin g Wa t er a s
Solven t . 1,3-Butadien-2-yl(water)bis(dimethylglyoximato)-
cobalt(III) (1) (0.050 g, 0.139 mmol) was added to distilled,
degassed H2O (2 mL) in a microwavable tube. Dimethyl
fumarate (0.042 g, 0.291 mmol) was added, and the tube was
sealed under an atmosphere of dry nitrogen. The reaction
mixture was run in the microwave at 100 °C for 15 min.
Solvent was removed by lyophilization. The remaining solid
C
12H21CoN4O5: C, 40.01; H, 5.88. Found: C, 40.22; H, 5.94.
Im p r oved Syn th esis of 1,3-Bu ta d ien -2-yl(w a ter )bis-
(d im eth ylglyoxim a to)coba lt(III) (1). A flame-dried round-
bottom flask and stir bar were cooled, and methanol (6 mL)
was added and degassed with dry nitrogen. Cobalt chloride
hexahydrate (0.531 g, 2.23 mmol) was added and was allowed
to stir for several minutes. Dimethylglyoxime (0.518 g, 4.46
mmol) was added, and the mixture was again allowed to stir
for several minutes. Sodium hydroxide (0.178 g, 4.46 mmol)
in degassed water (297 µL) was added dropwise over 5 min.
Triethylamine (1.55 mL, 11.15 mmol) was also added dropwise,
over 5 min. The reaction mixture was allowed to stir for 20
min at room temperature and was then cooled to -10 °C in
an ethylene glycol/dry ice bath. Sodium hydroxide (0.089 g,
2.23 mmol) in degassed water (297 µL) was added very slowly,
followed by sodium borohydride (0.023 g, 0.595 mmol) in
degassed water (297 µl), which was added slowly over 5 min
to avoid heating the mixture. The reaction mixture turned
green, indicating the presence of the cobalt anion. 4-Tosyl-1,2-
butadiene (0.500 g, 2.23 mmol) was added rapidly, and the
mixture was allowed to warm to room temperature slowly,
overnight. The reaction volume was reduced to a fourth of the
original volume via rotary evaporation. Triethylamine (0.257
mL, 1.85 mmol) in degassed water (8.82 mL) was chilled in
an ice-bath and then added to the reaction mixture, which was
also being chilled in an ice-bath. After approximately 30 min
to 1 h, the reaction mixture was filtered and the bright red-
orange solid was collected and dried under vacuum (0.375 g,
1.04 mmol, 47% yield), identical by spectroscopic comparison
to the material reported above.
Diels-Ald er Ad d u ct of 1 fr om Ma leic An h yd r id e Di-
en op h ile: Ad d u ct 2. 1,3-Butadien-2-yl(water)bis(dimethyl-
glyoximato)cobalt(III) (1) (0.050 g, 0.139 mmol) was added to
distilled, degassed tetrahydrofuran (THF) (4 mL). Maleic
anhydride (0.027 g, 0.277 mmol) was added, and the reaction
mixture was refluxed for 3 h under an atmosphere of dry
nitrogen. The solution was allowed to cool to room tempera-
ture, and the solvent was removed via rotary evaporation. The
remaining orange solid was purified by dissolving in a minimal
amount of methylene chloride and slowly adding pentane until
precipitation was complete. The solution was chilled in an ice-
bath for approximately 10 min, and the product was collected
by vacuum filtration and dried under vacuum (0.046 g, 0.100
mmol, 70% yield). Mp: 165 °C dec. 1H NMR (d8-THF): 5.27
(m, 1H), 3.10 (td, J ) 9.4, 1.9 Hz, 1H), 3.07 (td, J ) 9.3, 1.5

Aquocobaloxime 1,3-Dienyl Complex
Organometallics, Vol. 23, No. 10, 2004 2261
was washed with a pentane/anhydrous diethyl ether solution
(50:50). The product was placed under high vacuum to dry
(0.053 g, 0.105 mmol, 76% yield) and was identical by
spectroscopic comparison to the material reported above.
Diels-Ald er Ad d u ct of 1 fr om Citr a con ic An h yd r id e
Dien op h ile: Ad d u ct 4. 1,3-Butadien-2-ylwaterbis(dimeth-
ylglyoximato)cobalt(III) (1) (0.100 g, 0.278 mmol) was added
to distilled, degassed THF (5 mL) in a thick walled pressure
tube. Citraconic anhydride (0.062 g, 0.555 mmol) was added,
and the pressure tube was sealed with the reaction mixture
under an atmosphere of dry nitrogen. The tube was heated to
100 °C for 24 h in a silicon oil bath. The solvent was removed
via rotary evaporation, and the remaining rust-red solid was
washed with several portions of a pentane/anhydrous diethyl
ether solution (50:50). The product was dried under vacuum
(0.131 g, 0.277 mmol, 99% yield) and was found to have a ratio
was run in the microwave at 125 °C for 20 min. Solvent was
removed by rotary evaporation, and the remaining orange-
brown solid was washed with several portions of a pentane/
anhydrous diethyl ether solution (50:50). The product was
placed under high vacuum to dry (0.059 g, 0.137 mmol, 97%
yield) and was identical by spectroscopic comparison to the
material reported above.
Syn t h esis of Diels-Ald er Ad d u ct 5 Usin g Wa t er a s
Solven t . 1,3-Butadien-2-yl(water)bis(dimethylglyoximato)-
cobalt(III) (1) (0.051 g, 0.142 mmol) was added to distilled,
degassed H2O (1.5 mL) in a microwavable tube. Methyl vinyl
ketone (0.020 g, 0.285 mmol) was added, and the tube was
sealed under an atmosphere of dry nitrogen. The reaction
mixture was run in the microwave at 125 °C for 20 min.
Solvent was removed by lyophilization. The remaining solid
was washed with a pentane/anhydrous diethyl ether solution
(50:50). The product was placed under high vacuum to dry
(0.054 g, 0.125 mmol, 89% yield) and was identical by
spectroscopic comparison to the material above.
X-r a y Exp er im en ta l In for m a tion for Co[C4H7N2O2]2-
(C4H5)(H2O) (1). An orange-red parallelepiped-shaped crystal
of C12H21CoN4O5, approximate dimensions 0.09 mm × 0.10 mm
× 0.20 mm, was used for the X-ray crystallographic analysis.
The X-ray intensity data were measured at 193(2) K on a
Bruker SMART APEX CCD area detector system equipped
with a graphite monochromator and a Mo KR fine-focus sealed
tube (λ ) 0.71073 Å) operated at 1.75 kW power (50 kV, 35
mA). The detector was placed at a distance of 6.00 cm from
the crystal. A total of 1800 frames were collected with a scan
width of 0.30° in ω and an exposure time of 25 s/frame. The
frames were integrated with the Bruker SAINT software
package using a narrow-frame integration algorithm. The
integration of the data using a monoclinic cell yielded a total
of 7829 reflections to a maximum θ angle of 30.51° (0.70 Å
resolution), of which 4347 were independent, completeness )
97.2%, Rint ) 4.65%, Rsig ) 8.07% and 3424 were greater than
>2σ(I)σ(F2). The final cell constants of a ) 11.657(2) Å, b )
14.044(3) Å, c ) 9.6042(19) Å, â ) 92.228(3)°, volume )
1571.1(5) Å3 are based upon the refinement of the XYZ-
centroids of 1800 reflections above 20σ(I) with 8.494° < 2θ <
54.430°. Analysis of the data showed negligible decay during
data collection. Data were corrected for absorption effects using
the multiscan technique (SADABS). The ratio of minimum to
maximum apparent transmission was 0.8459. The structure
was solved and refined using the Bruker SHELXTL (Version
6.1) Software Package, using the space group Cc, with Z ) 4
for the formula unit, Co[C4H7N2O2]2(C4H5)(H2O). Successful
refinement of the structure required the application of a
racemic twinning model in which the twinning ratio refined
to a value of 0.44(3). The final anisotropic full-matrix least-
squares refinement on F2 with 221 variables converged at R1
) 5.59% for the 3424 observed data and wR2 ) 13.92% for all
4347 data. The goodness-of-fit was 1.058. The largest peak on
the final difference electron density synthesis was 1.026 e-/Å3,
and the largest hole was -0.394 e-/Å3 with an rms deviation
of 0.106 e-/Å3. The top six peaks in the final difference Fourier
map were within 0.90 Å of the cobalt atom. On the basis of
the final model, the calculated density was 1.523 g/cm3 and
F(000), 752 e-.
1
of 1.6:1.0, meta to para. Mp: 145 °C dec. H NMR (d8-THF):
Major isomer: 5.30 (m, 1H), 2.78 (m, 1H), 2.46 (m, 1H), 2.42
(m, 1H), 2.12 (s, 12H), 2.12 (m, 1H), 1.49 (d, J ) 16.5 Hz, 1H),
1.18 (s, 3H). Minor isomer: 5.25 (m, 1H), 2.72 (m, 1H), 2.50
(m, 1H), 2.34 (m, 1H), 2.14 (s, 12H), 1.91 (m, 1H), 1.78 (m,
1H), 1.21 (s, 3H). 13C NMR (d8-THF): Major isomer: 178.1,
177.5, 152.1, 151.8, 130.0, 128.8, 49.2, 47.6, 23.0, 12.0, 11.7.
Major/minor CH2’s: 40.4, 35.6, 31.2, 26.3. Minor isomer: 174.0,
173.8, 152.1, 151.8, 130.0, 128.8, 49.2, 47.6, 23.4, 12.0, 11.7.
IR (NaCl): 3331, 1778, 1680, 1202 cm-1. Anal. Calcd for C17H25
CoN4O8: C, 43.23; H, 5.33. Found: C, 42.82; H, 5.21.
-
Th er m a l Diels-Ald er Rea ction betw een Isop r en e a n d
Citr a con ic An h yd r id e. Isoprene (2.00 g, 29.36 mmol) and
citraconic anhydride (0.165 g, 1.47 mmol) were added to
degassed, distilled THF (7 mL) in a sealable pressure tube.
The reaction mixture was placed under dry nitrogen and
heated to 100 °C for 24 h. Once cooled, the solvent was
removed via rotary evaporation, and the thick, milky liquid
left behind was triturated with pentane (2 × 5 mL) and dried
via high vacuum (0.223 g, 1.24 mmol, 84.2%) (meta:para 1.05:
1). 1H NMR (CDCl3): Major isomer (meta): 5.58 (m, 1H), 2.99
(dd, J ) 7.0, 2.3 Hz, 1H), 2.56 (app dd, J ) 16.0, 2.1 Hz, 1H),
2.46 (d, J ) 16.2 Hz, 1H), 2.28 (m, 1H), 1.97 (d, J ) 16.2 Hz,
1H), 1.77 (s, 3H), 1.45 (s, 3H). Minor isomer (para): 5.61 (m,
1H), 2.93 (dd, J ) 7.4, 2.1 Hz, 1H), 2.64 (dd, J ) 6.2, 1.4 Hz,
1H), 2.53 (app d, J ) 16.0 Hz, 1H), 2.25 (m, 1H), 2.00 (m, 1H),
1.74 (s, 3H), 1.45 (s, 3H). EI HRMS (m/z) calcd for C10H12O3,
(M+), 180.0786; found, 180.0788.
Diels-Ald er Ad d u ct of 1 fr om Meth yl Vin yl Keton e
Dien op h ile: Ad d u ct 5. 1,3-Butadien-2-yl(water)bis(dimeth-
ylglyoximato)cobalt(III) (1) (0.100 g, 0.278 mmol) was added
to distilled, degassed THF (5 mL) in a thick walled pressure
tube. Methyl vinyl ketone (0.039 g, 0.555 mmol) was added,
and the pressure tube was sealed with the reaction mixture
under an atmosphere of dry nitrogen. The tube was heated to
100 °C for 24 h in a silicon oil bath. Solid was removed via
rotary evaporation, and the remaining orange-brown solid was
washed with several portions of a pentane/anhydrous diethyl
ether solution (50:50). The product was dried under vacuum
(0.107 g, 0.248 mmol, 89% yield) and was found to have a ratio
1
of 5.1:1.0, para to meta. Mp: 150 °C dec. H NMR (d8-THF):
Major isomer: 18.43 (bs, 2H), 4.78 (m, 1H), 2.59 (bs, 2H), 2.28
(m, 1H), 2.15 (s, 6H), 2.14 (s, 6H), 2.10 (m, 1H), 1.99 (m, 1H),
1.95 (s, 3H), 1.75 (m, 1H), 1.75 (m, 1H), 1.58 (m, 1H), 1.37
(ddd, J ) 24.3, 11.7, 5.3 Hz, 1H). Minor isomer (ketone methyl
protons): 1.94 (s, 3H). 13C NMR (d8-THF): 209.7, 151.2, 123.7,
48.7, 33.1, 30.2, 28.4, 27.5, 11.7. IR (NaCl): 3393, 2360, 2341,
1686, 1203 cm-1. Anal. Calcd for C16H27CoN4O6: C, 44.66; H,
6.32. Found: C, 44.73; H, 6.20.
Syn th esis of Diels-Ald er Ad d u ct 5 by Micr ow a ve. 1,3-
Butadien-2-yl(water)bis(dimethylglyoximato)cobalt(III) (1) (0.050
g, 0.139 mmol) was dissolved in distilled, degassed THF (2 mL)
in a microwavable tube. The tube was sealed under an
atmosphere of dry nitrogen, and methyl vinyl ketone (0.020
g, 0.278 mmol) was added via syringe. The reaction mixture
X-r a y Exp er im en ta l In for m a tion for Co[C4H7N2O2]2-
(C9H9O3)(EtOH) (4, L ) EtOH). An orange ellipsoidal-shaped
crystal of C19H29CoN4O8, approximate dimensions 0.01 mm ×
0.06 mm × 0.22 mm, was used for the X-ray crystallographic
analysis. The X-ray intensity data were measured at 193(2)
K on a Bruker SMART APEX CCD area detector system
equipped with a graphite monochromator and a Mo KR fine-
focus sealed tube (λ ) 0.71073 Å) operated at 1.75 kW power
(50 kV, 35 mA). The detector was placed at a distance of 6.00
cm from the crystal. A total of 1256 frames were collected with
a scan width of 0.30° in ω and an exposure time of 10 s/frame.
The frames were integrated with the Bruker SAINT software

2262 Organometallics, Vol. 23, No. 10, 2004
Tucker et al.
package using a narrow-frame integration algorithm. The
integration of the data using a monoclinic cell yielded a total
of 8360 reflections to a maximum θ angle of 21.97° (0.90 Å
resolution), of which 2783 were independent, completeness )
99.6%, Rint ) 9.95%, Rsig ) 15.28% and 1478 were greater than
>2σ(I)σ(F2). The final cell constants of a ) 14.40(4) Å, b )
10.82(3) Å, c ) 14.95(4) Å, â ) 101.78(6)°, volume ) 2280(10)
Å3 are based upon the refinement of the XYZ-centroids of 487
reflections above 20σ(I) with 4.41° < 2θ < 31.73°. Analysis of
the data showed negligible decay during data collection. Data
were corrected for absorption effects using the multiscan
technique (SADABS). The structure was solved and refined
using the Bruker SHELXTL (Version 6.1) Software Package,
using the space group P21/n, with Z ) 4 for the formula unit,
largest hole was -0.349 e-/Å3 with an rms deviation of 0.078
e-/Å3. On the basis of the final model, the calculated density
was 1.458 g/cm3 and F(000), 1048 e-.
Ack n ow led gm en t. We thank the National Science
Foundation for their support of this work (CHE-
0104083) and the NMR and X-ray instrumentation used
to characterize the compounds reported here. The Duke
University Center for Mass Spectrometry performed
high-resolution mass spectral analyses.
Su p p or tin g In for m a tion Ava ila ble: Tables giving de-
tails of the X-ray structure determinations, atomic coordinates
and isotropic thermal parameters, bond lengths and angles,
and anisotropic displacement parameters for 1 and 4 (L )
EtOH). This material is available free of charge via the
Internet at http://pubs.acs.org.
C
19H29CoN4O8. The final anisotropic full-matrix least-squares
refinement on F2 with 269 variables converged at R1 ) 6.97%
for the observed data and wR2 ) 18.45% for all data. The
goodness-of-fit was 1.007. The largest peak on the final
difference electron density synthesis was 0.457 e-/Å3, and the
OM040010Z