Synthesis and characterisation of [(en)2Co]3+ complexes coordinated by substituted thiourea ligands

Article abstract of DOI:10.1071/CH13150

Substituted thiourea ligands bind in a bidentate manner forming a four-membered ring through the sulfur atom and a deprotonated thiourea nitrogen atom when reacted with [(en)₂Co(OSO2CF3)₂]+ in tetramethylene sulfone. Reaction of unsymmetrical ligands results in the formation of coordination isomers, some of which can be separated by column chromatography using Sephadex SPC-25. Coordination isomers are easily distinguishable based on visible and 1H NMR spectroscopy . Twelve para-substituted and one meta-substituted ligands were studied: N,N′-dibenzylthiourea (1a); N-(R)phenyl-N′-benzylthiourea R≤H (2a), NO2 (2b), CH3 (2c); N-(R)phenyl-N′-(R′)phenylthiourea R, R′: H, H (3a), H, CH3 (3b), OCH3, NO2 (3c), CH3, NO2 (3d); N-methyl-N′-(R)phenylthiourea R≤H (4a), CH3 (4b), OCH3 (4c), NO2 (4d), 3-CH3 (4e). The solid state structure (X-ray) of one isomer of Co-4a as its perchlorate salt confirms the coordination mode suggested by 1H NMR spectroscopy and shows that the Co-N bond trans to the coordinated thiourea sulfur induces a structural trans effect of 0.019A.

Full text of DOI:10.1071/CH13150

CSIRO PUBLISHING
Aust. J. Chem. 2013, 66, 944–951
Full Paper
http://dx.doi.org/10.1071/CH13150
Synthesis and Characterisation of [(en)2Co]31 Complexes
Coordinated by Substituted Thiourea Ligands
A B C D F
, , , ,
A
A
Lee Roecker,
Mohammed Aiyegbo, Aladdin Al-Haddad,
A
A
A
B
C
Emily Fletcher, Ravi Kc, Jason Hurst, Timothy Lane, Ryan Larsen,
A
A
A
E F
,
Nicholas Noinaj, Say Lee Teh, Samuel K. Wade, and Sean Parkin
A
Department of Chemistry, Berea College, Berea, KY 40404, USA.
B
Department of Chemistry, Gettysburg College, Gettysburg, PA 17325, USA.
C
Department of Chemistry, Bates College, Lewiston, ME 04240, USA.
D
Department of Chemistry, Northern Michigan University, Marquette, MI 49855, USA.
Department of Chemistry, University of Kentucky, Lexington, KY 40506, USA.
Corresponding authors. Email: lroecker@nmu.edu; s.parkin@uky.edu (crystallographic work)
E
F
Substituted thiourea ligands bind in a bidentate manner forming a four-membered ring through the sulfur atom and a
deprotonated thiourea nitrogen atom when reacted with [(en)2Co(OSO2CF3)2]þ in tetramethylene sulfone. Reaction of
unsymmetrical ligands results in the formation of coordination isomers, some of which can be separated by column
chromatography using Sephadex SPC-25. Coordination isomers are easily distinguishable based on visible and 1H NMR
spectroscopy . Twelve para-substituted and one meta-substituted ligands were studied: N,N0-dibenzylthiourea (1a);
N-(R)phenyl-N0-benzylthiourea {R ¼ H (2a), NO2 (2b), CH3 (2c)}; N-(R)phenyl-N0-(R0)phenylthiourea {R, R0: H, H (3a),
H, CH3 (3b), OCH3, NO2 (3c), CH3, NO2 (3d)}; N-methyl-N0-(R)phenylthiourea {R ¼ H (4a), CH3 (4b), OCH3 (4c),
NO2 (4d), 3-CH3 (4e)}. The solid state structure (X-ray) of one isomer of Co-4a as its perchlorate salt confirms the
coordination mode suggested by 1H NMR spectroscopy and shows that the Co–N bond trans to the coordinated thiourea
˚
sulfur induces a structural trans effect of 0.019 A.
Manuscript received: 1 April 2013.
Manuscript accepted: 29 April 2013.
Published online: 27 May 2013.
Introduction
on one complex confirms the binding mode and shows that the
Co–N bond trans to the coordinated thiourea sulfur atom
is lengthened.
The interaction of substituted thiourea ligands with metal ions
has been of interest for several reasons. N-alkyl- and N-dialkyl-
N0-acyl(aroyl)thioureas have been evaluated as monitoring
ligands for platinum group metals in waste effluent streams.[1]
Thiourea derivatives of acridine complexed to AuI show activity
against Mycobacterium tuberculosis[2] and possess antitumour
activity when complexed to PtII[3–5] and RhIII.[6] The antifungal
properties of N-benzoyl-N0-dialkylthiourea derivatives com-
plexed to CoIII have been evaluated[7,8] and N-(antipyridynil)-
N0-(2-methoxyphenyl)thiourea has been fabricated into a sensor
that detects CoII.[9] In addition, the coordination chemistry of
urea,[10–12] thiourea,[13] and substituted urea ligands[14–16] has
been of general interest over many years. Continuing our interest
in the coordination of sulfur-containing ligands to CoIII[17–19] we
examined the coordination of the N,N0-substituted thiourea
ligands shown in Fig. 1 to the robust [(en)2Co]3þ fragment. All
of the ligands bond to CoIII in a bidentate manner through the
thiourea sulfur and a deprotonated nitrogen atom forming a four-
membered ring. Two coordination isomers are formed from the
reaction of unsymmetrical ligands. Reported here are details of
the reaction of thirteen ligands and characterisation of their
cobalt adducts by NMR spectroscopy and electrospray mass
spectrometry. Results from single-crystal X-ray diffraction
Results and Discussion
Synthesis
Syntheses of the complexes were accomplished by the reaction
of substituted thiourea ligands with cis-[(en)2Co(OSO2CF3)2]þ
in tetramethylenesulfone as illustrated in Scheme 1. The triflato
ion is readily substituted under mild conditions and these pre-
parations are another example of the synthetic versatility of
labile trifluoromethanesulfonato complexes.[6,16,19–24] Isolated
product yields ranged from 15 to 50 % and are significantly
lower than the nearly quantitative yields often reported for
similar reactions. The most prevalent side product is cis-
[(en)2Co(H2O)2]3þ which forms when unreacted cis-[(en)2Co
(OSO2CF3)2]þ is exposed to water before and during chroma-
tography. The yields, however, are similar to those reported for
the reaction of cis-[(en)2Co(OSO2CF3)2]þ with substituted urea
ligands[16] and are probably low due to the need to deprotonate
the ligand.
Symmetrical thiourea ligands (1 and 3a) react with cis-
[(en)2Co(OSO2CF3)2]þ to produce a single thiourea-containing
Journal compilation Ó CSIRO 2013
www.publish.csiro.au/journals/ajc

[(en)2Co]3þ Complexes Coordinated by Thiourea Ligands
945
product while unsymmetrical ligands have the potential to
produce coordination isomers. Isomers of the benzyl (2) and
methyl derivatives (4) are separable on Sephadex SPC-25 with
0.2 M NaClO4 while those of the diphenyl derivatives (3) are
not. When isomers can be separated, the first 2þ band to elute is
coordinated through the thiourea sulfur and the deprotonated
urea nitrogen next to the phenyl ring (endo isomer) while the
second 2þ band removed is coordinated through the thiourea
sulfur and the deprotonated urea nitrogen adjacent to the benzyl
or methyl group (exo isomer) (Fig. 2).
derivatives. Visible spectra of sealed aqueous solutions of
Co-4b (both isomers) are unchanged after sitting for one year
in the dark and NMR spectra of several different solid samples
(both isomers) after seven years of storage are identical to those
originally obtained. Isomerisation was observed with the
3-methyl derivative (4e). After cleanly separating the isomers
by chromatography, NMR spectra of the isolated crystals of the
exo isomer (filtered two weeks after chromatography) were
clearly contaminated with a small amount of the endo isomer
(Fig. 3).
When the phenyl substituent is a nitro group (2b, 3c, 3d, 4d)
more of the endo isomer is usually formed as might be expected
from the increased acidity of the –NH closest to the nitro group.
Aside from this, product distributions are variable and appear to
depend on reaction time. In one investigation four identical
experiments were set up with 4b and analysed after 2, 3, 14, and
21 days of stirring. Short reaction times (2 and 3 days) favoured
the endo isomer while the exo isomer predominated at longer
reaction times (14 and 21 days) suggesting that the exo isomer is
formed from the isomerisation of the endo isomer in tetramethy-
lene sulfone. There is no evidence of isomerisation, however, in
aqueous solution or in the solid state for the para-substituted
In addition to their elution characteristics on Sephadex
SPC-25, the 2þ charge of the complexes is confirmed by
elemental analysis and electrospray mass spectrometry. Nine
complexes were examined using the electrospray technique.
All show the presence of [(en)2Co(thiourea)]ClOþ4 , [(en)2Co
(thiourea)]2þ, and [(en)Co(thiourea)]ClOþ4 . For 1 the masses of
these complexes appear at 533, 217, and 473, respectively.
Results were identical for pairs of isomers run separately
(Co-4a and Co-4c) and are not complicated by the presence of
two isomers in a single sample (Co-3c). Finally, single-crystal
X-ray crystallography of the endo isomer of Co-4a confirms the
structure illustrated in Fig. 2.
S
2ϩ
N
H
N
H
NH2
H
H2N
H2N
S
1
N
CH2X
Co
R
N
S
NH2
N
H
N
H
R
2
Band 1 (endo isomer)
R
RЈ
S
2ϩ
N
N
NH2
H
H
H
3
H2N
H2N
S
N
R
Co
N
R
S
NH2
CH3
CH2X
N
N
H
H
4
Band 2 (exo isomer)
Fig. 1. Ligands in this study. The substituents (R, R0) are as follows: 2: 2a
H, 2b NO2, 2c CH3; 3: 3a H, H, 3b H, CH3, 3c OCH3, NO2, 3d CH3, NO2;
4: 4a H, 4b CH3, 4c OCH3, 4d NO2, and 4e CH3 (meta).
Fig. 2. Structures of the coordination isomers illustrated for ligands 2
(X ¼ C6H5) and 4 (X ¼ H).
ϩ
2ϩ
2ϩ
S
Y
X
NH2
Co
NH2
Co
NH2
Co
N
H
N
H
X
Y
H2N
H2N
S
N
H2N
H2N
OSO2CF3
OSO2CF3
H2N
H2N
S
N
ϩ
NH
(1)
NH
NH2
NH2
NH2
Y
X
Scheme 1.

946
L. Roecker et al.
Spectroscopic Characterisation
Visible Spectroscopy
Isomers are easily distinguishable withthe visible spectrumofthe
endo isomer showing a lmax at 513 nm followed by a higher
energy shoulder at 450nm before rising into the UV region.
Complexes of the exo isomer rise to the UV region more quickly
and have no shoulder at 450nm and the lower energy transition is
closer to 503nm. Solutions of the endo isomers are maroon in
colour while solutions of the exo isomers, while still maroon,
have a purplish cast.
Fig. 4 illustrates the visible spectra of the isomers of Co-4a
in water; these are representative of all complexes examined.
NMR Spectroscopy
1H NMR spectroscopy clearly identifies the mode of
thiourea coordination to the [(en)2Co]3þ fragment due to the
disappearance of the appropriate –NH resonance of the free
ligand upon coordination. Fig. 3 presents the 1H NMR spectra
for 4e and its coordination isomers from 6.8 to 9.8 ppm. The
–NH resonances in the uncoordinated ligand (upper spectrum)
appear as broad singlets with the thiourea hydrogen adjacent to
the aromatic ring being more downfield at 9.5 ppm. In the endo
isomer (middle spectrum) coordination through the deproto-
nated urea nitrogen adjacent to the phenyl ring is indicated by
the disappearance of the –NH resonance at 9.5 ppm and the
sharpening of the signal arising from the –NH adjacent to the
methyl group into a quartet at 7.5 ppm. In the exo isomer (lower
spectrum) the broad signal at 7.5 ppm is absent consistent with
coordination through –NCH3 while the resonance at 9.5 ppm is
now a sharp singlet. As mentioned earlier, the exo isomer of
Co-4e undergoes a small amount of isomerisation into the endo
isomer – this is evidenced in Fig. 3 by the residual quartet at
7.5 ppm in the spectrum of the exo isomer. The portion of each
spectrum below 7 ppm (not shown) is consistent with the
discussion that follows regarding Fig. 5.
9.5
9.0
8.5
8.0
7.5
7.0
The 1H NMR spectra for Co-1 and Co-3a in Fig. 5 illustrate
additional features that were consistently observed in all com-
plexes. The –CH2NH2 resonances of the coordinated ethylene-
diamine ligands appear as a group of overlying signals centred at
,2.5 ppm, but when the ligand is coordinated though a nitrogen
adjacent to a phenyl group as in Co-3a (middle spectrum) one of
the hydrogen signals shifts upfield to 1.5 ppm. COSY and
HMQC experiments clearly show that this signal is due to a
–CH of an ethylenediamine ligand. Location of the –CH2NH2
resonances of the coordinated ethylenediamines also vary
depending on the coordination mode of the ligand. When the
deprotonated urea nitrogen adjacent to a phenyl group is
coordinated as in Co-3a, the eight amine hydrogens appear over
a range of 3 to 6 ppm, but when the coordinated N is not adjacent
to a phenyl group as in Co-1 (lower spectrum) the signals are
bunched closer together over a range of only 1.2 ppm. The sharp
singlet observed in all spectra at 3.4 ppm is due to water. The
four benzylic hydrogens in Co-1 are also found in the amine
hydrogen region. Those adjacent to the coordinated, deproto-
nated urea nitrogen appear as an AB quartet at 4.1 ppm while
those next to the non-coordinated, protonated urea nitrogen
appear as a doublet at 4.5 ppm. The hydrogen attached to the
uncoordinated urea nitrogen appears downfield from the aro-
matic hydrogens of the phenyl or benzyl rings. In Co-1 this
resonance appears as a triplet at 8.3 ppm while in Co-3a it
appears as a sharp singlet at 9.8 ppm – each of these signals
integrate as a single hydrogen and are shifted only slightly from
their location in the non-coordinated ligand.
δ [ppm]
Fig. 3. 1H NMR spectra of 4e (upper) and its coordination isomers when
bonded to the [(en)2Co]3þ fragment: the endo isomer of Co-4e (middle) and
the exo isomer of Co-4e (lower) in d6-DMSO.
(a)
350
450
550
650
λ [nm]
(b)
350
450
550
650
λ [nm]
The upper spectrum in Fig. 5 is that of the main product
produced from the reaction of the unsymmetrical ligand 2b.
Coordination through the endo position is indicated in three
Fig. 4. Visible spectra of the complexes of 4a in water. (a) Band 1: endo
isomer. (b) Band 2: exo isomer.

[(en)2Co]3þ Complexes Coordinated by Thiourea Ligands
947
9
8
7
6
5
4
3
2
δ [ppm]
Fig. 5. 1H NMR spectra of Co-1 (lower), Co-3a (middle), and Co-2b (upper) in d6-DMSO.
ways. First, the –NH(C6H5) resonance present in the free ligand
is gone while the –NHCH2(C6H5) resonance remains as a triplet
at 8.5 ppm. Second, the amine hydrogens are spread over the
region from 6.0 to 3.5 ppm and this total area integrates as 10
hydrogens – eight due to –NH2CH2 and two due to –CH2(C6H5)
which appear as an AB quartet at 4.4 ppm. Third, a single
–CH2NH2 appears at 1.6 ppm and the remaining seven appear
in the cluster at 2.5 ppm.
Fig. 6 presents 13C-APT NMR spectra for the same three
complexes used to generate Fig. 5. The symmetry present in
symmetrical ligands 1 and 3a is broken upon coordination. For
example, the benzylic peak at 47.1 ppm and the quaternary
carbon peak at 139.3 ppm in non-coordinated 1 each split into
two peaks in Co-1: 48.4 and 45.3 ppm and 138.7 and 138.3 ppm,
respectively. The three peaks due to aromatic –CHs in 3a (124 to
129 ppm) appear as six peaks in Co-3a over the same region and
the single peak due to the quaternary carbon in 3a at 140.1 ppm
appears as two peaks at 136.7 and 141.0. When non-symmetrical
ligands coordinate (Co-2b) the same overall pattern of peaks
observed for the free ligand is retained, but some peaks are
shifted due to interaction with the CoIII. In all cases, signals due
to –CH2NH2 appear as three overlapping or as four distinct
peaks around 45 ppm, always downfield of the solvent peak
(d6-DMSO) centred at 39.5 ppm.
10 peaks between 122 and 132 ppm while the remaining three
quaternary carbon peaks appear as six peaks between 134 and
142 ppm. The same pattern was observed in each of the com-
plexes formed from reaction of four unsymmetrical substituted
diphenyl ligands. Integration of the –NHX resonances allows
calculation of the isolated amounts of each isomer. In Co-3b,
for example, the isomers are isolated in roughly a 50 : 50
distribution while for Co-3d the distribution is 60 : 40
(endo –CH3 compared with endo –NO2). No additional attempts
were made to resolve the isomers.
Crystallographic Investigations
Single-crystal X-ray diffraction analysis of the perchlorate salt
of the endo isomer of Co-4a confirms the bidentate coordination
of the ligands to CoIII through the thiourea sulfur and a depro-
tonated thiourea nitrogen atom forming a four-membered ring
(Fig. 7). Selected bond lengths and angles are given in Table 1.
Coordination of the substituted thiourea to CoIII significantly
alters bond lengths about the thiourea carbon atom compared
with the non-coordinated ligand. The C–S bond length compiled
from twenty structures of thiourea ligands[25–28] averages
III
˚
1.68 (1) A. Upon coordination of 4a to Co the C–S bond
III
lengthens to 1.740 (3) A. In Co complexes coordinated by
thioether ligands[17,29] the average C–S distance is 1.82 (1) A;
˚
˚
Isomers formed from reaction of ligands 3b–3d are not
separable on Sephadex SPC-25, but do co-crystallise. Peaks
are doubled in the 13C NMR and both –NHX resonances are
˚
thus the C–S bond length found here of 1.740 (3) A is about
halfway between that of a C–S double and a C–S single bond
length. As the C–S bond lengthens, the C–N bonds decrease to
1
present in the H NMR spectra. The single peaks at 21.1 and
˚
1.317 (4) (endo) A and 1.329 (4) (exo) A from an average of
˚
1.36 (1) A in the free ligands due to delocalisation arising from
deprotonation of the ligand. Structural determinations have also
˚
180.2 in the ligand 3b are split into two peaks: 21.1 and 21.2 and
173.5 and 173.8, respectively, in the isolated cobalt product.
Also in 3b, the five CH resonances of the free ligand spilt into

948
L. Roecker et al.
˚
Table 1. Selected bond lengths [A] and angles [deg.] for the cation
[Co-4a]21 (endo isomer)
Standard deviations are in parentheses; refer to Fig. 7 for the numbering
scheme
Bond lengths
Co(1)–N(2)
Co(1)–N(3)
Co(1)–N(4)
S(1)–C(1)
1.934(3)
1.957(3)
1.976(3)
1.740(3)
1.453(4)
Co(1)–N(5)
Co(1)–N(6)
Co(1)–S(1)
N(1)–C(1)
N(2)–C(1)
1.957(2)
1.962(2)
2.2848(10)
1.329(4)
1.317(4)
N(1)–C(2)
Bond angles
N(5)–Co(1)–N(3)
N(2)–Co(1)–S(1)
C(1)–S(1)–Co(1)
C(1)–N(2)–C(3)
C(3)–N(2)–Co(1)
N(2)–C(1)–S(1)
177.15(11)
72.26(8)
77.14(12)
124.5(3)
133.8(2)
109.2(2)
N(2)–Co(1)–N(6)
N(4)–Co(1)–S(1)
C(1)–N(1)–C(2)
C(1)–N(2)–Co(1)
N(2)–C(1)–N(1)
N(1)–C(1)–S(1)
169.44(11)
168.28(8)
122.7(3)
101.4(2)
127.0(3)
123.8(3)
The common binding mode of N-benzoyl-N0-alkylthiouruea
ligands is coordination through the acyl oxygen atom and
thiourea sulfur to form a six-membered ring while substituted
thiourea ligands lacking an acyl group generally bind to the metal
in a monodentate manner through the thiourea sulfur atom. The
average C–S distance in the structures referenced above is
˚
1.74 (2) A and is not dependent on the coordination mode or the
metal and is identical to that observed in this work. In the cobalt
complex, Co(MTCB)3 (MTCB ¼ N-(morpholinothiocarbonyl)
benzamide)[8] the Co–S distance of 2.213(6) A is shorter than the
˚
˚
2.285 (1) A found here. By way of comparison, the range of
Co–S(thioether) bond lengths is 2.217 (2) to 2.301 (1) A.[29] That
˚
the bond in the coordinated thiourea complexes studied here is
not shorter (expected due to charge delocalisation in the depro-
tonated ligand compared with neutral thiourea or thioether
ligands) could be a consequence of distortions arising from
coordination of the four-membered ring.
170
160
150
140
130
120
50
40
δ [ppm]
Fig. 6. 13C-APT NMR spectra of Co-1 (lower), Co-3a (middle) and Co-2b
(upper) in d6-DMSO.
The four-membered ring has bond angles of 72.26 (8)8,
77.1 (1)8, 109.2 (2)8, and 101.4 (2)8. This arrangement is
facilitated by deformation of the trigonal planar environment
about the thiourea carbon atom (C1) with bond angles of
109.2 (2)8, 127.0 (3)8, and 124.8 (3)8 and lengthening of the
bond between the S and C1. The bite angle of the coordinated
thiourea ligand, 72.26 (8)8, is smaller than the bite angle of
85.4 (4)8 generated by the coordinated ethylenediamines which
form five-membered rings. The small bite angle contributes to
the overall distorted octahedral geometry about the Co.
The Co–N(en) bond distance trans to the thiourea sulfur,
C9
N3
C10
C6
C5
C7
C4
N4
C8
C3
Co1
N2
N6
˚
1.976 (3) A, is longer than those of the Co–N(en) bonds which
˚
are trans to each other, 1.957 (3) A. Thus, there is a small, but
N1
observable structural trans effect (STE) induced by the thiourea
˚
C1
sulfur of 0.019 A. S-bonded thiourea ligands coordinated to
RuIII[6] and thioether ligands coordinated to CoIII[29] both induce
N5
C11
˚
a STE of 0.02 A. Greater effects are induced by coordinated
sulfur atoms possessing a negative formal charge as in thiolato
complexes of CoIII where an average STE of 0.044 (2) A was
˚
C12
S1
C2
found.[34,35] A more significant STE would be expected in the
complex examined given the negative formal charge the thio-
urea sulfur develops due to delocalisation in the deprotonated,
coordinated ligand. The lack of a significant STE induced by the
deprotonated N atom of the thiourea ligand is also unexpected
Fig. 7. Ellipsoid plot of a cation of Co-4a (endo isomer). Hydrogen atoms
have been omitted for clarity.
been reported with disubstituted thiourea ligands bonded to
PtII,[1,3,5] RhIII,[1,6] RhI,[30] CoIII,[8] ZnII,[31] HgII,[32] and CuI.[33]
The mode of coordination observed here has been reported
previously – twice in complexes of PtII[1,5] and once with RhI.[30]
˚
given that effects as large as 0.03 A have been observed in
two structures containing deprotonated urea ligands.[16,36]

[(en)2Co]3þ Complexes Coordinated by Thiourea Ligands
949
Unpublished work on related structures (J. Krause and
L. Roecker, unpubl. data) suggests that the STE induced by
deprotonated, coordinated thiourea ligands are much larger than
observed in the structure reported here. We are currently
obtaining additional crystallographic data to confirm this unpub-
lished work.
Compound 3c: dC (300 MHz, d6-DMSO) 20.8, 56.0, 114.1,
124.5, 126.5, 129.5 (CH, CH3); 132.1, 134.1, 137.2, 156.5,
182.5 (C).
Compound 4a: dH (300 MHz, d6-DMSO) 2.93 (d, J 4.5, 3H),
7.14 (t, J 6.0, 1H), 7.32 (m, 4H), 7.68 (s, 1H), 9.56 (s, 1H).
dC (300 MHz, d6-DMSO) 32.1, 123.1, 124.9, 129.2 (CH, CH3);
139.1, 181.2 (C).
Compound 4b: dH (300 MHz, d6-DMSO) 2.28 (s, 3H), 2.91
(d, J 4.5, 3H), 7.14 (d, J 7.8, 2H), 7.23 (d, J 7.8, 2H), 7.55 (s, 1H),
9.45 (s, 1H). dC (300 MHz, d6-DMSO) 21.1, 31.8, 124.3, 129.8
(CH, CH3); 134.2, 137.0, 181.7 (C).
Compound 4c: dH (300 MHz, d6-DMSO) 2.88 (d, J 4.5, 3H),
3.75 (s, 3H), 6.90 (d, J 6.9, 2H) 7.19 (d, J 6.9, 2H), 7.44 (s, 1H),
9.33 (s, 1H). dC (300 MHz, d6-DMSO) 31.8, 56.0, 114.6, 126.8
(CH, CH3); 132.0, 157.2, 182.0 (C).
Compound 4d: dH (300 MHz, d6-DMSO) 2.97 (d, J 4.5, 3H),
7.81 (d, J 8.7, 2H) 8.18 (d, J 8.7, 2H), 8.24 (s, 1H), 10.21 (s, 1H).
dC (300 MHz, d6-DMSO) 31.7, 120.9, 125.1 (CH, CH3); 142.3,
147.0, 181.4 (C).
Conclusion
The reaction of [(en)2Co(OSO2CF3)2](CF3SO3) with symmet-
rical thiourea ligands results in the formation of a single
cobalt(III) complex while the reaction with unsymmetrical
ligands results in the formation of two isomeric complexes. The
coordination isomers are easily distinguishable by either visible
or 1H NMR spectroscopy. Using these well characterised
complexes as a starting point, understanding more complicated
interactions of substituted thiourea ligands that serve as bridging
ligands between cobalt(III) ions is possible (L. Roecker et al.,
unpubl. data).
Compound 4e: dH (400 MHz, d6-DMSO) 2.28 (s, 3H), 2.91
(d, J 3.9, 3H), 6.93 (d, J 7.5, 1H) 7.17 (m, 3H), 7.61 (s, 1H), 9.49
(s, 1H). dC (400 MHz, d6-DMSO) 21.05, 31.28, 120.40, 123.78,
125.46, 128.56 (CH, CH3); 138.04, 138.87, 180.94 (C).
Experimental
General Data
All chemicals were reagent grade and used as received with the
exception of tetramethylene sulfone which was vacuum-
distilled before use. Cis-[(en)2Co(OSO2CF3)2](CF3SO3) was
prepared following a reported procedure.[24] Visible spectra
were obtained with a Perkin–Elmer Lambda 3B spectropho-
tometer. 1H and 13C NMR spectra were recorded with a JOEL
JNM-FX-200 at Berea College or with a Bruker 400 at Bates
College in DMSO-d6 with TMS as an internal reference. Mass
spectra were recorded on a Thermo Finnigan LCQ Deca Max.
Elemental analyses were performed by Galbraith Laboratories,
Knoxville, TN, USA.
Preparation of CoIII Complexes Coordinated
by Substituted Thiourea Ligands
All cobalt complexes were prepared by the reaction between the
thiourea ligand with cis-[(en)2Co(OSO2CF3)2](CF3SO3) in tet-
ramethylene sulfone. A typical reaction is described here for the
reaction with 4e to produce Co-4e. Ligand 4e (0.30 g,
1.62 mmol) was dissolved in 10 g of tetramethylene sulfone and
[(en)2Co(OSO2CF3)2](CF3SO3) (1.00 g, 1.59 mmol) was added.
The reaction mixture was sealed and stirred. After 3 days the
reaction solution was diluted with 300 mL of water and stirred
for 20 min before filtering to remove unreacted ligand. The
solution was sorbed onto Sephadex SPC-25 (2 cm ID ꢀ 20 cm)
and loaded as a dark maroon band. After washing with water,
elution with 0.1 M NaClO4 removed a minor pink band of
[(en)2Co(O2CO)]þ. Continued elution with 0.2 M NaClO4
moved a maroon band that broadened and separated into two
distinct bands which were the desired products. These were
followed by an orange band of [(en)2Co(OH2)2]3þ. After
removing the first maroon band with 0.2 M NaClO4, the top of
the column containing the diaquo complex was removed and
then the second maroon band was removed with 0.5 M
Ba(ClO4)2. Evaporation and/or refrigeration over several days
yielded crystalline samples of each product: Band 1 (endo iso-
mer) (0.29 g, 33 % yield), Band 2 (exo isomer) (0.16 g, 18 %
yield). All complexes were characterised by visible, 1H NMR,
and 13C NMR (APT) spectroscopy; many were also char-
acterised by the 2D NMR experiments HMQC or COSY along
with electrospray mass spectrometry.
Preparation of Ligands
Ligands were prepared by the reaction of an amine with the
appropriate isothiocyanate. A typical preparation is described
here for the preparation of 3b. Methylisothiocyanate (5.0 g,
68 mmole) was slowly added to a stirred solution of p-toluidine
(7.3 g, 68 mmol) that had been dissolved in 50 mL of absolute
ethanol. The mixture was heated to reflux; cooling to room
temperature deposited a white solid that was then isolated by
vacuum filtration and recrystallised twice from 150 mL of hot
absolute ethanol (9.8 g, 80 % yield). All ligands were char-
acterised by 1H and 13C NMR (APT) spectroscopy; many were
also characterised by the 2D experiments HMQC or COSY to
help determine which hydrogen atoms were connected to which
carbon atoms.
Compound 1: dH (400 MHz, d6-DMSO) 4.71 (s, 4H), 7.33
(m, 10H), 7.96 (s, 2H). dC (400 MHz, d6-DMSO) 126.2, 127.60,
128.25 (CH, CH3); 47.07, 139.25 (C, CH2); C¼S not observed.
Compound 2a: dH (300 MHz, d6-DMSO) 4.80 (d, J 7.5, 2H),
7.14 (t, J 7.5, 1H), 7.42 (m, 9H), 8.25 (s, 1H), 9.69 (s, 1H). dC
(400 MHz, d6-DMSO) 123.31, 124.29, 126.87, 127.43, 128.27,
128.64 (CH); 47.22, 139.00, 139.16, 180.78 (C, CH2).
Caution: Although we have not experienced any explosions,
perchlorate salts are potentially explosive and should be handled
only in very small quantities.
Complex Co-1: dH (400 MHz, d6-DMSO) 2.4 (br m, 8 H),
3.90 (br s, 2H), 4.14 (q, J 47.5, 15.5, 2H), 4.40 (m, 5H), 4.59
(s, 1H), 4.75 (s, 1H), 4.95 (s, 1H) 7.30 (m, 10 H), 8.33 (t, J 6.1,
1 H). dC (400 MHz, d6-DMSO) 126.77, 127.04, 127.26, 128.22,
128.43 (CH); 43.99, 44.17, 44.65, 44.91, 45.31, 48.43, 138.29,
138.71, 174.94 (C, CH2). m/z (z ¼ þ1) 533, 473; (z ¼ þ2) 217.
Anal Calc. for CoSC19H31N6Cl2O8ꢁ2H2O (633.5): Co 8.80,
Cl 10.59. Found: Co 8.76, Cl 10.63 %.
Compound 3a: dH (300 MHz, d6-DMSO) 7.14 (t, J 7.5, 2H),
7.37 (t, J 7.5, 4H), 7.49 (d, J 7.5, 4H), 9.81 (s, 2H). dC (300 MHz,
d6-DMSO) 124.25, 125.03, 129.05 (CH); 140.09, 180.15 (C).
Compound 3b: dH (300 MHz, d6-DMSO) 2.29 (s, 3H), 7.14
(m, 3H), 7.35 (m, 5H), 7.50 (d J 8.5, 1H), 9.72 (s, 2H).
dC (300 MHz, d6-DMSO) 21.1, 124.2, 124.5, 124.9, 129.0,
129.5 (CH, CH3); 134.3, 137.4, 140.1, 180.2 (C).

950
L. Roecker et al.
Complex Co-2a Band 1: dH (400 MHz, d6-DMSO) 1.57
3.80 (s, 1H), 4.45 (s, 1H), 4.70 (s, 3H), 5.05 (s, 1H), 5.25 (s, 1H),
6.95 (d, J 8.4, 2H), 7.28 (d, J 8.4, 2H), 7.42 (q, J 4.5, 1H). dC
(300 MHz, d6-DMSO) 27.1, 55.3, 115.1, 127.6 (CH, CH3); 43.3,
44.6, 44.7, 44.8, 133.0, 157.2, 175.4 (C, CH2). m/z (z ¼ þ1) 473,
413; (z ¼ þ2) 187. Calc. MW 573.3.
(s, 1H), 2.5 (br, 7 H), 3.30 (s, 1H), 3.90 (s, 1H), 4.35 (q,
J 55.5, 14.6, 2H), 4.50 (s, 1H), 4.60 (s, 1H), 4.70 (s, 1H), 4.80
(s, 1H), 5.15 (s, 1H), 5.35 (s, 1H), 7.35 (m, 10 H), 8.20 (t, J 5.4,
1H). dC (400 MHz, d6-DMSO) 126.04, 126.33, 126.99, 127.29,
128.23, 129.95 (CH); 43.36, 44.22, 44.70, 44.80, 45.00, 138.72,
140.86, 174.81 (C, CH2). m/z (z ¼ þ1) 519, 459; (z ¼ þ2) 209.
Calc. MW 619.4.
Complex Co-2b Band 1: dH (400 MHz, d6-DMSO) 1.67
(s, 1H), 2.5 (m 7 H), 3.61 (s, 1H), 3.85 (s, 1H), 4.38 (q, J 55.5,
14.6, 2H), 4.50 (s, 1H), 4.95 (s, 3H), 5.21 (2, 1H), 5.50 (s, 1H),
7.28 (d J 8.7, 1H), 7.42 (m, 4H), 7.50 (d J 8.7, 2H), 8.27 (d J 8.7,
2H), 8.52 (t, J 5.4, 1H). dC (400 MHz, d6-DMSO) 125.2, 127.15,
127.40, 127.54, 128.29 (CH); 43.97, 44.48, 44.68, 44.88,
138.15, 144.61, 148.56, 176.42 (C, CH2).
Complex Co-2c Band 1: dH (400 MHz, d6-DMSO) 1.61
(s, 1H), 2.25 (s, 3H), 2.5 (br, 7 H), 3.28 (s, 1H), 3.90 (s, 1H),
4.30 (q, J 55.5, 14.6, 2H), 4.45 (s, 1H), 5.10 (s, 1H), 5.30 (s, 1H),
5.50 (s, 1H), 5.70 (s, 1H), 5.80 (s, 1H), 7.30 (m, 9 H), 8.20 (t,
J 5.4, 1H). dC (400 MHz, d6-DMSO) 20.65, 126.16, 126.96,
127.27, 128.21, 130.50 (CH, CH3); 43.37, 44.15, 44.66, 44.80,
44.90, 135.33, 138.02, 138.75, 174.71 (C, CH2).
Complex Co-3a: dH (400 MHz, d6-DMSO) 1.61 (s, 1H), 3.30
(s, 1H), 3.88 (s, 1H), 4.45 (s, 1H), 4.88 (s, 3H), 5.13 (s, 1H), 5.39
(s, 1H), 7. 28 (t, J 6.0, 1H), 7.35 (m, 9H). dC (400 MHz,
d6-DMSO) 124.01, 125.25, 126.07, 126.25, 128.43, 129.96
(CH); 43.32, 44.72, 44.90, 136.68, 140.97, 173.07 (C, CH2).
m/z (z ¼ þ1) 505, 445; (z ¼ þ2) 203. Calc. MW 605.4.
Complex Co-3b (mixture of isomers): dC (300 MHz,
d6-DMSO) 21.1, 21.4, 124.3, 124.7, 125.4, 126.2, 126.7,
126.8, 129.0, 129.5, 130.5, 131.0 (CH, CH3); 43.8, 45.2, 45.4,
133.5, 134.2, 135.3, 136.5, 138.2, 141.2, 173.5, 173.8 (C, CH2).
Complex Co-3c (mixture of isomers): m/z (z ¼ þ1) 580, 520;
(z ¼ þ2) 241. Calc. MW 680.4.
Complex Co-4c Band 2: dH (300 MHz, d6-DMSO) 2.50 (br,
8H), 2.68 (s, 3H), 4.00 (s, 1H), 4.30 (s, 3H), 4.58 (s, 1H), 4.78
(s, 2H), 4.76 (s, 1H), 6.96 (d, J 8.4, 2H), 7.27 (d, J 8.4, 2H), 9.42
(s, 1H). dC (300 MHz, d6-DMSO) 33.0, 55.8, 114.2, 126.0 (CH,
CH3); 44.9, 45.2, 45.3, 46.0, 130.1, 157.6, 171.7 (C, CH2). m/z
(z ¼ þ1) 473, 413; (z ¼ þ2) 187. Calc. MW 573.3.
Complex Co-4e Band 1: dH (400 MHz, d6-DMSO) 1.61
(s, 1H), 2.32 (s, 3H), 2.50 (m, 7H), 2.68 (d, J 4.6, 3H), 3.25
(s, 1H), 3.87 (s, 1H), 4.48 (s, 1H), 4.65 (s, 1H), 4.78 (s, 2H), 5.10
(s, 1H), 5.30 (s, 1H), 7.03 (m, 2H), 7.12 (d, J 7.3, 1H), 7.27 (t,
J 7.8, 1H), 7.49 (q, J 4.5, 1H). dC (400 MHz, d6-DMSO) 20.98,
27.22, 123.27, 126.68, 129.73 (CH, CH3); 43.40, 44.69, 44.93,
139.41, 140.71, 175.21 (C, CH2).
Complex Co-4e Band 2: dH (400 MHz, d6-DMSO) 2.32
(s, 3H), 2.56 (m, 8H), 2.72 (s, 3H), 4.42 (m, 3H), 4.50 (s, 1H),
4.89 (s, 1H), 5.12 (s, 2H), 5.27 (s, 1H), 6.99 (d, J 7.4, 1H), 7.23
(m, 3H), 9.47 (s, 1H). dC (400 MHz, d6-DMSO) 21.05, 32.64,
119.91, 123.22, 125.27, 128.45 (CH, CH3); 44.22, 44.49, 44.77,
45.35, 137.00, 137.87, 170.49 (C, CH2).
X-Ray Crystallography
X-ray diffraction data were collected at 90 K on a Nonius kappa
CCD diffractometer from a crystal flash-cooled directly into
Table 2. Crystal data and structure refinement for the perchlorate salt
of [Co-4a]21 (endo isomer)
Parameter
[Co-4a]21
Complex Co-4a Band 1: dH (300 MHz, d6-DMSO) 1.60
(s, 1H), 2.50 (br, 7H), 2.71 (d, 3H), 3.4 (s, 1H), 3.88 (s, 1H),
4.51 (s, 1H), 4.8 (br, 3H), 5.12 (s, 1H), 5.35 (s, 1H), 7.35 (m, 5H),
7.55 (q, J 4.5, 1H). dC (300 MHz, d6-DMSO) 27.8, 126.6, 126.9,
130.6 (CH, CH3); 44.0, 45.3, 45.5, 141.5 (C, CH2); C¼S not
observed. m/z (z ¼ þ1) 443, 383; (z ¼ þ2) 172. Calc. MW 543.3.
Complex Co-4a Band 2: dH (300 MHz, d6-DMSO) 2.50 (br,
8H), 2.71 (s, 3H), 4.01 (s, 1H), 4.30 (s, 2H), 4.45 (s, 1H), 4.69 (s,
2H), 4.82 (s, 1H), 4.97 (s, 1H), 7.21 (br, 1H), 7.38 (br, 4H), 9.54
(s, 1H). dC (300 MHz, d6-DMSO) 33.2, 123.3, 125.3, 129.2 (CH,
CH3); 44.9, 45.2, 45.3, 46.0, 137.7, 171.2 (C, CH2). m/z (z ¼ þ1)
443, 383; (z ¼ þ2) 172. Anal. Calc. for CoSC12H25N6Cl2O8ꢁ
2H2O (543.3): Co 10.17, Cl 12.24. Found: Co 10.13,
Cl 12.20 %.
Empirical formula
Formula weight
[C12H25N6S](ClO4)2ꢁ1.32H2O
567.05
Crystal size [mm3]
0.25 ꢀ 0.20 ꢀ 0.10
90.0(2)
Temperature [K]
˚
Wavelength [A]
0.71073
Crystal system, space group
Unit cell dimensions
Triclinic, P ꢂ1
˚
a [A]
9.7586(3)
˚
b [A]
9.8451(3)
˚
c [A]
12.9448(5)
a [deg.]
b [deg.]
g [deg.]
75.0898(14)
89.7522(14)
68.5636(16)
3
˚
Volume [A ]
1113.08(6)
Z
2
Calculated density [g cmꢂ3
]
1.692
Complex Co-4b Band 1: dH (300 MHz, d6-DMSO) 1.62
(s, 1H), 2.28 (s, 3H), 2.5 (br, 8H), 2.68 (d, J 7.8, 3H), 3.88
(s, 1H), 4.50 (s, 1H), 4.75 (br, 3H), 5.11 (s, 1H), 5.32 (s, 1H),
7.12 (d, J 7.8, 2H), 7.21 (d, J 7.8, 2H), 7.49 (q, J 4.5, 1H). dC
(300 MHz, d6-DMSO) 21.3, 27.8, 126.8, 131.1 (CH, CH3); 44.0,
45.3, 45.5, 135.9, 138.9 (C, CH2); C¼S not observed.
Complex Co-4b Band 2: dH (300 MHz, d6-DMSO)2.30
(s, 3H), 2.5 (br, 8H), 2.70 (s, 3H), 4.00 (s, 1H), 4.35 (br, 3H),
4.61 (s, 1H), 4.70 (s, 1H), 4.80 (s, 1H) 4.95 (s, 1H), 7.19 (d, J 7.8,
2H), 7.28 (d, J 7.8, 2H), 9.48 (s, 1H). dC (300 MHz, d6-DMSO)
21.1, 33.1, 123.6, 129.7 (CH, CH3); 44.8, 45.2, 45.3, 45.9, 134.5,
135.0 (C, CH2); C¼S not observed. m/z (z ¼ þ1) 457, 397;
(z ¼ þ2) 179. Calc. MW 557.3.
Absorption coefficient [mmꢂ1
]
1.163
F(000)
586.4
y range for data collection
Limiting indices
1.648 to 27.448
–12 # h # 12, ꢂ12 # k # 12,
ꢂ16 # l # 13
13 240/5078 (Rint ¼ 0.0570)
99.7
Reflections collected/unique
Completeness to y ¼ 27.44 [%]
Absorption correction
Semi-empirical from equivalents
0.893 and 0.760
Full-matrix least-squares on F2
5078/16/313
Max. and min. transmission
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
1.008
Final R indices [I . 2s(I)]
R indices (all data)
˚
Largest diff. peak and hole [e A
R1 0.0484, wR2 0.0885
R1 0.1003, wR2 0.1031
0.724 and ꢂ0.522
Complex Co-4c Band 1: dH (300 MHz, d6-DMSO) 1.69 (s,
1H), 2.45 (s, 3H), 2.5 (br, 8H), 2.66 (d, J 4.8, 3H), 3.20 (s, 1H),
ꢂ3
]

[(en)2Co]3þ Complexes Coordinated by Thiourea Ligands
951
liquid nitrogen.[37] Unit cell parameters were obtained from
10 ꢀ 1 degree frames and were refined using a least-squares
scheme based on all data frames (SCALEPACK, Denzo-
SMN[38]). Lorentz and polarisation corrections were applied
during data reduction. The structure was solved by direct
methods (SHELXS97[39]) and refined against F2 by weighted
full-matrix least-squares (SHELXL97[39]). Absorption correc-
tions (SCALEPACK[38] and XABS2[40]) were applied. Hydrogen
atoms were found in difference maps and refined using a com-
bination of riding models and free refinement with isotropic
displacement parameters derived from their carrier atoms. Non-
hydrogen atoms were refined with anisotropic displacement
parameters. Atomic scattering factors were taken from the
International Tables for Crystallography.[41] Final models were
checked using Platon[42] and by an R-tensor.[43] Crystal data and
relevant details of the structure determination are summarised in
Table 2 and selected geometrical parameters are given in
Table 1. All bond lengths (Table S1) and angles (Table S2) are
provided as Supplementary Material.
[12] D. P. Fairlie, W. G. Jackson, Inorg. Chim. Acta 1988, 150, 81.
doi:10.1016/S0020-1693(00)87628-8
[13] D. P. Fairlie, W. A. Wickramasinghe, K. A. Byriel, H. Taube, Inorg.
Chem. 1997, 36, 2242. doi:10.1021/IC9611397
[14] P. Maslak, J. J. Sczepanski, M. Parvez, J. Am. Chem. Soc. 1991, 113,
1062. doi:10.1021/JA00003A061
[15] R. L. Blakeley, A. Treston, R. K. Andrews, B. J. Zerner, J. Am. Chem.
Soc. 1982, 104, 612. doi:10.1021/JA00366A040
[16] L. Roecker, J. Akande, L. N. Elam, I. Gagua, B. W. Helton, M. C.
Prewitt, A. M. Sargeson, J. H. Swango, A. C. Willis, T. Xin, J. Xu,
Inorg. Chem. 1999, 38, 1269. doi:10.1021/IC980287P
[17] L. Roecker, M. H. Dickman, D. L. Nosco, R. J. Doedens, E. Deutsch,
Inorg. Chem. 1983, 22, 2022. doi:10.1021/IC00156A018
[18] L. Roecker, E. Deutsch, Inorg. Chem. 1985, 24, 16. doi:10.1021/
IC00195A006
[19] A. Ellis, A. Fultz, R. Hicks, T. Morgan, L. Parsons, Jr, M. J. Saderholm,
L. A. Smith, M. Staub, J. K. Starnes, L. J. Sun, L. Roecker, Aust.
J. Chem. 1992, 45, 2049. doi:10.1071/CH9922049
[20] N. E. Dixon, W. G. Jackson, M. J. Lancaster, G. A. Lawrence,
A. M. Sargeson, Inorg. Chem. 1981, 20, 470. doi:10.1021/
IC50216A031
Crystallographic information files have been deposited with
the Cambridge Crystallographic Data Centre and assigned the
deposit codes 931427. These can be obtained free of charge via
http://www.ccdc.cam.ac.uk/data_request/cif.
[21] N. E. Dixon, G. A. Lawrance, A. M. Sargeson, Inorg. Chem. 1984, 23,
2940. doi:10.1021/IC00187A009
[22] G. A. Lawrance, Chem. Rev. 1986, 86, 17. doi:10.1021/CR00071A002
[23] P. H. Lay, R. H. Magnuson, H. Taube, Inorg. Chem. 1989, 28, 3001.
doi:10.1021/IC00314A026
[24] Z. Cao, W. P. Forest, Y. Gao, P. E. Fanwick, Y. Zhang, T. Ren, Inorg.
Chem. 2011, 50, 7364. doi:10.1021/IC200836V
Supplementary Material
[25] D. X. West, J. K. Swearingen, A. K. Hermetet, L. J. Ackerman,
C. Presto, J. Mol. Struct. 2000, 522, 27 and references therein.
doi:10.1016/S0022-2860(99)00314-2
Selected bond lengths and bond angles for the cation [Co-4a]2þ
(endo isomer) are available on the Journal’s website.
[26] W. Zhou, B. Li, L. Zhu, J. Ding, Y. Zhang, L. Lu, X. Yang, J. Mol.
Struct. 2004, 690, 145. doi:10.1016/J.MOLSTRUC.2003.11.029
[27] W. Zhou, K. Leng, Y. Zhang, L. Lu, J. Mol. Struct. 2003, 657, 215.
doi:10.1016/S0022-2860(03)00371-5
[28] H. Arslan, U. Flo¨rke, N. Ku¨lcu¨, Turk. J. Chem. 2004, 28, 673.
[29] L. R. Gahan, T. M. Donlevey, T. W. Hambley, Inorg. Chem. 1990, 29,
1451 and references therein. doi:10.1021/IC00332A038
[30] G. Kemp, A. Roodt, W. Purcell, K. R. Koch, J. Chem. Soc., Dalton
Trans. 1997, 4481. doi:10.1039/A705887J
Acknowledgements
Funding for the Thermo Finnigan LCQ Deca Max was through NSF Grant
0421581 to Matthew Saderholm at Berea College. The authors thank
Dr Saderholm for his assistance obtaining the mass spectrometry data. Initial
funding for this work was provided by the Appalachian College Association,
Berea, KY.
[31] M. Bonamico, G. Dessy, V. Fares, L. Scaramuzza, J. Chem. Soc. A
References
1971, 3195. doi:10.1039/J19710003195
[1] K. R. Koch, Coord. Chem. Rev. 2001, 216–217, 473.
[2] L. C. Eiter, N. W. Hall, C. S. Day, G. Saluta, G. L. Kucera, U. Bierbach,
J. Med. Chem. 2009, 52, 6519. doi:10.1021/JM9012856
[3] U. Bierbach, T. W. Hambley, N. Farrell, Inorg. Chem. 1998, 37, 708.
doi:10.1021/IC970420Y
[32] W. Zhou, W. Yang, L. Qiu, Y. Zhang, Z. Yu, J. Mol. Struct. 2005, 749,
89. doi:10.1016/J.MOLSTRUC.2005.03.046
[33] I. F. Taylor, Jr, M. S. Weininger, E. L. Amma, Inorg. Chem. 1974, 13,
2835. doi:10.1021/IC50142A014
[34] R. C. Elder, L. R. Florian, R. E. Lake, A. M. Yacynych, Inorg. Chem.
1973, 12, 2690. doi:10.1021/IC50129A038
[35] M. H. Dickman, R. J. Doedens, E. Deutsch, Inorg. Chem. 1980, 19,
[4] R. Guddneppanavar, G. Saluta, G. L. Kucera, U. Bierbach, J. Med.
Chem. 2006, 49, 3204. doi:10.1021/JM060035V
[5] E. T. Martins, H. Baruah, J. Kramarcyk, G. Saluta, C. S. Day,
G. L. Kucera, U. Bierbach, J. Med. Chem. 2001, 44, 4492.
doi:10.1021/JM010293M
945. doi:10.1021/IC50206A030
[36] D. P. Fairlie, W. G. Jackson, G. M. McLaughlin, Inorg. Chem. 1989,
28, 1983. doi:10.1021/IC00309A043
[6] C. G. Barry, E. C. Turney, C. S. Day, G. Saluta, G. L. Kucera,
U. Bierbach, Inorg. Chem. 2002, 41, 7159. doi:10.1021/IC025744N
[7] R. del Campo, J. J. Criado, R. Gheorghe, F. J. Gonza´lez, M. R.
Hremosa, F. Sanz, J. L. Manzano, E. Monte, E. Rodr´ıguez-Ferna´ndez,
J. Inorg. Biochem. 2004, 98, 1307. doi:10.1016/J.JINORGBIO.2004.
03.019
[37] S. Parkin, H. Hope, J. Appl. Cryst. 1998, 31, 945. doi:10.1107/
S0021889898005305
[38] Z. Otwinowski, W. Minor, in Methods in Enzymology (Eds C. W.
Carter, Jr, R. M. Sweet) 1997 Vol 276 (Macromolecular Crystallogra-
phy Part A), pp. 307–326 (Academic Press: New York, NY).
[39] G. M. Sheldrick, Acta Crystallogr. 1997, A64, 112.
[40] S. Parkin, B. Moezzi, H. Hope, J. Appl. Cryst. 1995, 28, 53.
doi:10.1107/S0021889894009428
[8] W. Zhou, W. Yang, L. Xie, X. Cheng, J. Inorg. Biochem. 2005, 99,
1314. doi:10.1016/J.JINORGBIO.2005.03.004
[9] H. Alizaman, M. R. Ganjali, P. Norouzi, A. Tajorodi, Y. Hanifehpour,
J. Chilean Chem. Soc. 2007, 52, 1332.
[10] N. E. Dixon, D. P. Fairlie, W. G. Jackson, A. M. Sargeson, Inorg.
[41] International Tables for Crystallography, Vol. C: Mathematical,
Physical and Chemical Tables (Ed. A. J. C. Wilson) 1992
(Kluwer Academic: London).
Chem. 1982, 21, 688. doi:10.1021/IC00132A044
[11] N. J. Curtis, N. E. Dixon, A. M. Sargeson, J. Am. Chem. Soc. 1983, 105,
5347. doi:10.1021/JA00354A027
[42] A. L. Spek, J. Appl. Cryst. 2003, 36, 7. doi:10.1107/
S0021889802022112
[43] S. Parkin, Acta Crystallogr. 2000, A56, 157.