Cobalt(II) scorpionate-like complexes obtained from in situ synthesized ligand created in [Co(0)-1-hydroxymethyl-3,5-dimethylpyrazole-VOSO 4-NH4SCN] system

Article abstract of DOI:10.1016/j.poly.2012.08.021

Novel cationic-anionic {[Co^II(NCS)L^S] ⁿ⁺[X]^n-} X = [V₆O ₁₁(CH₃O)₈]^2-, [Co ^II(NCS)₄]^2- (1 and 2) and neutral [Co ^II(NCS)₂L^S] (3) complexes have been isolated in one pot synthesis from [Co⁰-L-VOSO₄-NH₄SCN] (L = 1-hydroxymethyl-3,5-dimethylpyrazole) system. The anion [V^IV ₂V^V₄O₁₁(CH₃O) ₈]^2- was found to be a new mixed valence Lindqvist type cluster. The redox reactions resulted in atypical compositions and structures of the products as well as in an in situ formation of tris(3,5- dimethylpyrazolylmethyl)amine (L^S), which is a scorpionate-type ligand. The coordination numbers of cobalt(II) in the species were found to be five (1), five and four (2) and six (3). The compounds were characterized by analytical, spectroscopic (FT-IR and UV-Vis) and X-ray methods. For the complex containing two different transition metals (1) and that with one transition metal but in two different geometrical environments (2), the digital filtration method applied made it possible to elucidate two independent crystal fields.

Full text of DOI:10.1016/j.poly.2012.08.021

Polyhedron 47 (2012) 104–111
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Polyhedron
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Cobalt(II) scorpionate-like complexes obtained from in situ synthesized ligand
created in [Co(0)–1-hydroxymethyl-3,5-dimethylpyrazole–VOSO4–NH4SCN] system
b
c
Anna Adach a, , Marek Daszkiewicz , Maria Cieslak-Golonka
⇑
´
a
´
Institute of Chemistry, Jan Kochanowski University, 15G Swie˛tokrzyska Str., 25-406 Kielce, Poland
b Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Okólna 2, 50-950 Wrocław, Poland
c
_
´
Faculty of Chemistry, Wrocław University of Technology, Wybrzeze Wyspianskiego 27, 50-370 Wrocław, Poland
a r t i c l e i n f o
a b s t r a c t
Novel cationic–anionic {[CoII(NCS)LS]n+[X]nꢀ} X = [V6O11(CH3O)8]2ꢀ, [CoII(NCS)4]2ꢀ (1 and 2) and neutral
[CoII(NCS)2LS] (3) complexes have been isolated in one pot synthesis from [Co0–L–VOSO4–NH4SCN]
(L = 1-hydroxymethyl-3,5-dimethylpyrazole) system. The anion [VIV2VV4O11(CH3O)8]2ꢀ was found to be
a new mixed valence Lindqvist type cluster. The redox reactions resulted in atypical compositions and
structures of the products as well as in an in situ formation of tris(3,5-dimethylpyrazolylmethyl)amine
(LS), which is a scorpionate-type ligand. The coordination numbers of cobalt(II) in the species were found
to be five (1), five and four (2) and six (3). The compounds were characterized by analytical, spectroscopic
(FT-IR and UV–Vis) and X-ray methods. For the complex containing two different transition metals (1)
and that with one transition metal but in two different geometrical environments (2), the digital filtration
method applied made it possible to elucidate two independent crystal fields.
Article history:
Received 28 May 2012
Accepted 8 August 2012
Available online 17 August 2012
Keywords:
Crystal structure
Cobalt(II) complexes
Electronic spectra
Tris(1-(3,5-dimethylpyrazolylmethyl)amine)
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
in the process of zerovalent metal oxidation, in this work we have
changed Zn(II) into the VO2+ group. Vanadium, apart from having
Pyrazole-based ligands play an important role in biology and
chemistry [1,2]. For example, a pyrazole entity was found to be a
component of various biological molecules taking part in, e.g. ge-
netic processes [1–3]. Besides, pyrazole rings can be considered
models for histidine residues of proteins [3]. Metal complexes con-
taining pyrazole ligands have been well established in literature
[4–8] and have various application areas [1–3]. For example, they
can mimic an active site of metalloenzymes [1,3].
a biological significance of its compounds [13], is used as a compo-
nent in implant alloys (in contrast to zinc) [14].
In this work, we have applied and modified a general procedure
for the isolation of complexes starting from zerovalent metals [15].
+
In this method, the presence of NH4 ion as one of the reagents
plays the role of a proton reservoir for the reduced atmospheric
oxygen, which finally leads to water formation and M0 ? Mn+ me-
tal oxidation [15].
As pyrazole derivatives have found various successful applica-
tions in bioinorganic chemistry, in this work our interest has been
focused on using them in models for metal implant corrosion
[9,10]. Toxic effects of metals released from orthopedic implants
upon dissolution are very well documented [9,10].
Recently, in an attempt to understand the process of cobalt oxi-
dation in the presence of biological ligands, we investigated solid
state products isolated from a [Co–1-hydroxymethyl-3,5-dimethyl-
pyrazole–Mn+] system [11,12]. We have found that a combination
of both redox and condensation processes in the [Co0–1-hydroxy-
methyl-3,5-dimethylpyrazole–Zn2+] system resulted in the forma-
tion of a cationic–anionic complex of Co(II) pyrazolylamine and
Zn(II) urotropine, respectively. Both organic ligands were formed
in situ [11]. Since in the [cobalt(0)–organic ligand–Mn+] system
the metallic ion seems to be one of the crucial factors taking part
Here, we have reported physicochemical characteristics of three
subsequently isolated complexes with various coordination num-
bers of the cobalt(II) ion. Each of these complexes contains an
in situ formed scorpionate ligand (LS) while only one of them has
an earlier unknown vanadate cluster. Moreover, unlike our earlier
studies reporting exclusively a cationic–anionic species formation
[11,12], one complex was found to be in a neutral form.
The results of this work can be further evidence that the reac-
tions of metallic cobalt as a substrate can result in isolating prod-
ucts of unique compositions and structures.
2. Experimental
2.1. Materials and measurements
All reagents were purchased from commercial sources and used
without further purification. The experiments were carried out in
air atmosphere. Cobalt powder, VOSO4 and 1-hydroxymethy-3,
⇑
Corresponding author.
E-mail address: adach@ujk.kielce.pl (A. Adach).
0277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.08.021

A. Adach et al. / Polyhedron 47 (2012) 104–111
105
Table 1
Crystal data and structure refinement for the studied compounds 1–3.
1
2
3
Chemical formula
Formula weight
T (K)
C8H24O19V6ꢁ2(C19H27CoN8S)ꢁ4(C7H8)
2(C19H27CoN8S)ꢁC4CoN4S4ꢁCH4O
C20H27CoN9S2
516.56
295(2)
1007.70
295(2)
1240.24
295(2)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
triclinic
P1
triclinic
P1
monoclinic
P21/n
12.7916(9)
12.6345(9)
16.3674(12)
90
104.593(6)
90
2559.9(3)
4
ꢀ
ꢀ
10.7321(9)
12.5025(9)
18.6712(11)
83.034(5)
78.492(6)
69.014(7)
2288.7(3)
2
10.5710(7)
15.4554(11)
18.8732(13)
86.767(6)
85.263(6)
74.293(6)
2956.3(4)
2
a
(°)
b (°)
c
(°)
V (Å3)
Z
Dcalc
l
1.462
1.06
1.393
1.09
1.340
0.86
(mmꢀ1
)
Crystal size (mm)
hmax (°)
0.41 ꢂ 0.18 ꢂ 0.03
0.32 ꢂ 0.28 ꢂ 0.26
0.33 ꢂ 0.24 ꢂ 0.16
24.7
24.1
24.1
No. of measured, independent and observed [I > 2
Tmin, Tmax
r
(I)] reflections
21816, 7771, 2834
0.827, 0.973
0.113
0.064, 0.147, 0.91
7771/0/550
0.908
32235, 9284, 5701
0.666, 0.761
0.092
0.061, 0.178, 1.01
9284/2/668
1.008
17 565, 4043, 2867
0.719, 0.823
0.042
0.046, 0.115, 1.08
4043/0/295
1.076
Rint
R[F2 > 2
r
(F2)], wR(F2), S
Data/restraints/parameters
Goodness of fit on F2
D
qmax
,
D
qmin (e Åꢀ3
)
0.35, ꢀ0.33
0.63, ꢀ0.43
0.39, ꢀ0.30
5-dimethylpyrazole were purchased from Aldrich Chemical
Company. Elemental analyses were performed with a Perkin Elmer
Elemental Analyzer 2400 CHN and an AES-ICP 3410 emission
spectrometer (Co) using appropriate Aldrich standards. IR spectra
were recorded on Perkin-Elmer FTIR 1600 (4000–400 cmꢀ1) and
Perkin-Elmer FTIR 2000 (600–100 cmꢀ1) spectrophotometers in
KBr pellets and Nujol mull, respectively.
methanolic solution of VOSO4 (0.0815 g, 0.5 mmol) and NH4SCN
(0.0769 g, 1 mmol). Finally, a metanolic solution (5 cm3) of 1-
hydroxymethyl-3,5-dimethylpyrazole (0.2525 g, 2.0 mmol) was
added. The mixture was heated to 50–60 °C and stirred magneti-
cally until a dissolution of the cobalt powder (ca. 5 h). The resulting
solution was of a dark violet color. After 3 days, deep green crystals
1 appeared, which were filtered off and recrystallized from the
mixture of toluene and CH2Cl2 (4:1). Subsequently, under a slow
evaporation of filtrate 1 at room temperature, blue crystals 2
precipitated after 4 days and were filtered off and recrystallized
from methanol. Finally, a pink crystalline compound 3 precipitated
from the resulting filtrate 2 (Scheme 1) after 1 week. It was filtered
off and recrystallized from warm methanol.
Electronic reflectance spectra (range 50000–5000 cmꢀ1) were
measured on a Cary 500 Scan (Varian) UV–VIS–NIR Spectropho-
tometer. In order to obtain accurate values of the band positions,
the spectra were analyzed using a variable digital filter method
[16,17] with the following filter parameters: the number determin-
ing a degree of resolution enhancement:
number determining the filter width: N = 10; the increment
between points (step): K = 100 cmꢀ1
a = 200.0; the integer
All the isolated compounds (1–3) were repeatedly recrystallized
to obtain products suitable for X-ray crystallographic
measurements.
.
Magnetic moments were measured using an MSB-MKI instru-
ment (Sherwood Scientific Ltd.) at ambient temperature with
Co[Hg(SCN)4] as standard.
Compound (1) yield: 18.9%. Elemental analyses for C74H110N16-
S2O19Co2V6: Anal. Calc.: C, 44.60; H, 5.60; N, 11.12; Co, 5.75; V,
15.16. Found: C, 44.36; H, 5.38; N, 11.47; Co, 5.53; V, 14.95%; IR
spectrum: 2972(vw), 2059(s), 1550(m), 1467(m), 1425(w),
1390(m) 1302(w),1276(w), 1247(m), 1180(w), 1130(w), 1037(m),
949(vs), 764(m), 774(m), 689(w), 669(m), 647(vw), 628(m)
595(m,br), 548(sh), 482(m,br), 441s,sh), 417(s,sh), 366(w,sh),
354(w), 327(m), 291(m), 238(m), 206(w), 191(m, sh), 157(m),
145(w), 133(w), 121(m).
Compound (2) yield: 38%. Elemental analyses for C43H58N20S6-
OCo3: Anal. Calc.: C, 41.64; H, 4.71; N, 22.59; Co, 14.30. Found: C,
41.53; H, 4.37; N, 23.03; Co, 14.83%; IR spectrum: 3132(vw),
2914(vw), 2054(vs), 1628(vw), 1553(s), 1466(s), 1419(m),
1387(m,sh), 1375(m,sh), 1302(m), 1246(m), 1180(w), 1128(m),
1065(m,sh), 1044(m, sh), 985(w), 945(m), 891(m), 837(w),
808(m,sh), 796(m,sh), 690(m), 670(m), 659(m), 625(m), 594(m),
548(m), 498(m), 481(m), 440(s), 408(m,br), 353(m,sh), 318(s,sh),
305(s,sh), 288(s,sh), 239(m), 223(w), 189(s,sh) 182(s,sh), 149(m),
140(m), 133(w), 112(w).
2.2. Single crystal X-ray diffraction studies
X-ray diffraction data were collected on a KUMA Diffraction
KM-4 four-circle single crystal diffractometer equipped with a
CCD detector using graphite-monochromatized Mo K
a radiation
(k = 0.71073 Å). The raw data were treated with the CRYSALIS Data
Reduction Program (version 1.172.32.6), taking into account an
absorption correction. The intensities of the reflection were cor-
rected for Lorentz and polarization effects. The crystal structures
were solved by direct methods [18] and refined by a full-matrix
least-squares method using SHELXL-97 program [18] (Table 1). All
non-hydrogen atoms were refined using anisotropic displacement
parameters. The H-atoms were visible on Fourier difference maps,
but placed by geometry and allowed to ride on the parent atom.
2.3. Preparation of complexes
Compound (3) yield: 21%. Elemental analyses for C20H27N9S2Co:
Anal. Calc.: C, 46.50; H, 5.27; N, 24.41; Co, 11.41. C, 46.93; H, 5.37;
N, 24.03; Co, 11.80%; IR spectrum: 2920(vw), 2073(vs), 1554(s),
1463(s)(, 1435(m,sh), 1419(m), 1396(m), 1246(w), 1174(m),
118(m), 1045(s), 1016(m), 974(m), 890(m), 796(s), 689(m),
All the compounds (1–3) were synthesized according to the
general procedure [15]. The reagents: metallic Co, VOSO4, NH4SCN
and organic ligand L were used in 1:1:2:4 M ratio, respectively.
Cobalt powder (0.0296 g, 0.5 mmol) was added to 30 cm3 of a

106
A. Adach et al. / Polyhedron 47 (2012) 104–111
[11,12] (Scheme 1). The resulting product (LS–tris(1-(3,5-dim-
ethylpyrazolylmethyl)amine)) was found to be a tetradentate scor-
pionate-like ligand [3] – analog of poly(pyrazol-1-yl)borates [2].
3.1. Crystal structure of cobaltoscorpionates
3.1.1. Crystal structure of [Co(NCS)LS]2[V6O11(CH3O)8]ꢁ4C7H8 (1)
ꢀ
Complex 1 crystallizes in P1 triclinic space group (Table 1) with
one [Co(NCS)LS]+ ion, half of the [V6O11(CH3O)8]2ꢀ anion and two
toluene molecules in the asymmetric unit of the unit cell. The [V6-
O11(CH3O)8]2ꢀ anion lies in inversion centers, whereas the other
species are located in general positions.
A molecular structure of the [Co(NCS)LS]+ ion is very similar to
that published earlier, containing chloride ligand [11,12]. One
tris(1-(3,5-dimethylpyrazolylmethyl)amine (LS) and one (SCN)ꢀ an-
ion create a five-coordination sphere around the Co2+ ion. The cen-
tral ion is significantly displaced from the basal plane of the trigonal
bipyramid (Fig. 1a). The shortest and the longest Co–N distances are
observed in vertical positions of the trigonal bipyramid (Table 2).
Examples of organic vanadium (IV/V) oxo- and methoxobridged
complexes with nuclearity higher than two are rare in literature
Scheme 1. Isolation procedure for (1–3).
669(s), 630(s), 599(s), 570(m), 513(w), 488(m), 478(m), 456(m),
422(m), 405(m), 365(w), 325(m), 268(s), 246(s), 224(s,sh),
205(s,sh), 196(s), 152(m,sh), 142(w), 132(w), 121(m), 110(w).
3. Results and discussion
Two cationic–anionic (1–2) and one neutral (3) complexes were
obtained in one pot synthesis from the system: [Co0–1-hydroxy-
methyl-3,5-dimethylpyrazole (L)–VOSO4–NH4(SCN)] (Scheme 1).
All the isolated compounds (1–3) contained cobalt exclusively
on +2 oxidation state and with its various coordination numbers
(CN): 5 for compound 1, 5 and 4 for compound 2, and 6 for com-
pound 3.
The oxidation of Co0 with atmospheric oxygen in the presence
+
of NH4 cations leads to cobalt(II) formation and releasing water
and ammonia (Scheme 1) [11,12,15]:
The ammonia molecules were further used for the synthesis of
scorpionate ligands (LS), which are products of an in situ condensa-
tion of NH3 with 1-hydroxymethyl-3,5-dimethylpyrazole (L)
Fig. 1. (a) The structure of the hexavanadate [V6O11(CH3O)8]2ꢀ anion in 1 and (b) in
referenced compound [17]. (c) Coordination sphere of the Co2+ ion in compound 1.
(d) Normalized Hirshfeld surface of the [Co(NCS)LS]+ ion and interacting species.

A. Adach et al. / Polyhedron 47 (2012) 104–111
107
nꢀ [26]
Table 2
belongs to a highly symmetrical Lindqvist structure [M6O19
]
Selected geometric parameters (Å, °).
with eight oxygen atoms substituted with methoxo groups [26].
The mixed valence [VIV2VV4O11(OR)8]2ꢀ cluster exhibits two
1
coordination numbers:
5 and 6 for V(IV) and V(V) ions,
Co1–N1
Co1–N32
Co1–N22
Co1–N12
Co1–N2
V1–O7
1.977(6)
2.031(5)
2.037(6)
2.052(5)
2.290(4)
1.588(5)
1.849(4)
1.864(4)
1.963(5)
2.003(5)
2.2053(13)
3.014(2)
3.0164(19)
1.593(5)
1.769(5)
1.923(5)
1.928(5)
V2–O1
V2–O10
V2–V1i
V2–V3
2.000(5)
2.2431(12)
3.014(2)
3.1134(19)
1.600(5)
1.787(4)
1.827(5)
1.985(5)
1.987(5)
2.2504(12)
3.0164(19)
1.928(5)
1.864(4)
1.849(4)
2.2053(13)
2.2431(12)
2.2504(13)
respectively. The arrangement of the methoxo and oxo ligands
are similar to that found in [27] (Fig. 1a and b). Eight positions
(6 ordered + 2 disordered) of the CH3O– group have been deter-
mined (Fig. 1b) [27]. Considering only a mutual position of the
methoxo groups, it was found that [V6O11(CH3O)8]2ꢀ anion forms
a different isomer, i.e. of Ci point group symmetry when compared
with the recently reported hexavanadate of approximately Cs point
group symmetry [27].
Oxygen atoms of a hexavanadate anion are attractive sites for
the formation of an intermolecular hydrogen bonding. Many weak
hydrogen bonds are found between [Co(LS)(NCS)]+ and [V6O11(CH3-
O)8]2ꢀ anions (Table S1 and Fig. 1d). Two toluene molecules are
V3–O9
V3–O6
V3–O3
V3–O2
V3–O4
V3–O10
V3–V1i
O4–V2i
O5–V1i
O6–V1i
O10–V1i
O10–V2i
O10–V3i
V1–O6i
V1–O5i
V1–O1
V1–O2
V1–O10
V1–V2i
V1–V3i
V2–O8
V2–O5
V2–O3
also involved in weak intermolecular interactions of C–Hꢁ ꢁ ꢁ
p type.
V2–O4i
In turn, the first two C–Hꢁ ꢁ ꢁ
p
interactions listed in Table S1 can be
2
classified to group II of Malone’s classification [28], whereas the
Co1–N1A
Co1–N21
Co1–N11
Co1–N31
Co1–N1
Co2–N1B
Co2–N41
1.958(5)
2.033(4)
2.043(4)
2.050(4)
2.287(3)
1.974(5)
2.027(4)
Co2–N51
Co2–N61
Co2–N2
Co3–N4D
Co3–N6F
Co3–N5E
Co3–N1C
2.028(4)
2.034(5)
2.292(4)
1.931(5)
1.952(6)
1.955(6)
1.961(5)
other two belong to group V.
3.1.2. Crystal structure of [Co(NCS)LS)]2[Co(NCS)4]ꢁCH3OH (2)
ꢀ
Complex 2 crystallizes in P1 triclinic space group (Table 1). Two
[Co(NCS)LS]+ cations, one [Co(NCS)4]2ꢀ anion and one methanol
molecule exist in the asymmetric unit of the unit cell (Fig. 2). The
methanol molecule is disordered over two symmetry independent
positions, i.e. C1M–O1M and C2M–O2M. The distance between
C1M and O2M is unusually short and equals to 2.637 Å. However,
no effects associated with such a hydrogen bonding interaction
were observed in the infrared spectrum. Therefore, in the model
of the crystal structure of 2, the methanol molecule is disordered
over two positions with a site occupancy factor 0.5 each, rather than
two molecules occupying symmetry independent positions.
3
Co1–N2
Co1–N1
Co1–N31
2.007(3)
2.075(3)
2.119(3)
Co1–N21
Co1–N11
Co1–N3
2.152(3)
2.174(3)
2.261(2)
Symmetry code: (i) ꢀx, ꢀy + 1, ꢀz + 1.
[19–22]. Generally, they are formed during oxidation of VO2+ cat-
ion or reduction of vanadium(V) [19,21,22]. Here, a polyoxovana-
date cluster decorated with six bridging and two terminal
methoxo groups has been formed. Such hexavanadate cluster, have
been recently studied due to their peculiar coordination features
[23], the spin frustrated structure [24], and fluorescence of surfac-
tants [25]. In the structure of 1, the polyoxymethoxo vanadate an-
Two symmetry independent Co2+ ions have five coordinate
spheres, each with one tris(1-(3,5-dimethylpyrazolylmeth-
yl)amine) (LS) and one (NCS)– anion creating a trigonal bipyramid
around the central ion. However, the Co2+ ion is displaced from
the basal plane of the bipyramid. Therefore, axial Co–N distances
significantly differ from each other in both symmetry independent
[Co(NCS)(LS)]+ ions (Table 2). The structure of complex 2, apart
from two [Co(NCS)(LS)]+ cations, contains one [Co(NCS)4]2ꢀ anion
ion contains eight l2-methoxo and four l2-oxo bridges (Fig. 1a and
b). Such a geometry requires a mixed-valence state of vanadium
ions, i.e. four VV and two VIV. The [V6O11(CH3O)8]2ꢀ anion formally
Fig. 2. Asymmetric unit of the unit cell of [Co(LS)(NCS)]2[Co(NCS)4]ꢁCH3OH (2).

108
A. Adach et al. / Polyhedron 47 (2012) 104–111
Fig. 3. (a) Coordination sphere of the Co2+ ion in compound 3. (b) Normalized Hirshfeld surface of the [Co(NCS)2LS] molecule.
of an approximately tetrahedral configuration. The tetrahedrally
coordinated Co(II) ion with N-bonded (NCS)ꢀ ions is responsible
for the deep blue color (‘‘cobalt blue’’) [29] of the crystals of 2.
Additionally, in the crystal structure of 2, several hydrogen bon-
dings are found (Table S2). Similarly to 3 (vide infra), both the lone
pair at the sulfur atom and electron cloud between carbon and
In the crystal structure of 3, the C24–H24ꢁ ꢁ ꢁC35iv and
C17–H17Bꢁ ꢁ ꢁC34v interactions are of the C–Hꢁ ꢁ ꢁ
p type (Table S3).
They both can be classified to group III of Malone’s classification
of X–Hꢁ ꢁ ꢁ
p interactions [28,34].
3.2. Infrared spectra
nitrogen atoms are the acceptors. Also, one C–Hꢁ ꢁ ꢁ
found (Table S2). It belongs to group III of Malone’s classification
of the X–Hꢁ ꢁ ꢁ interactions [28].
p interaction is
The comparison of selected vibrational bands of free 1-hydroxy-
methyl-3,5-dimethylpyrazole (L) and 1–3 are important for the
confirmation of the in situ formation of a new ligand, i.e. tris(1-
(3,5-dimethylpyrazoylmethyl)amine) (LS). The spectrum of the free
ligand L is completely different from that of the coordinated one. In
the starting (L) the OH stretching band lies at 3152 cmꢀ1 and is
very broad due to the inter- and intramolecular hydrogen bonding
(O. . .H. . .N). The O–H band disappears in the spectra of 1–3. Addi-
p
3.1.3. Crystal structure of [Co(NCS)2(LS)] (3)
Complex crystallizes in P21/n monoclinic space group
3
(Table 1). The Co2+ ion coordinates the tetradentate tris(1-(3,5-
dimethylpyrazolylmethyl)amine) [30], and two NCSꢀ anions
(Fig. 3). Compound 3 exists as a molecular crystal, because the
inorganic anions fully compensate the positive charge of the cobalt
ion in [Co(NCS)2(LS)]. The ligands are bound to Co2+ by the nitrogen
atoms, forming chromophore of tetragonal geometry (CoN2N4). It
tionally, the appearance of new, medium stretching m(C–N) vibra-
tion typical of tertiary amine at 1273 cmꢀ1 (1), 1265 cmꢀ1 (2)
1267 cmꢀ1 (3) can be related to the presence of LS [39,40]. The IR
spectra of (1–3) exhibited also a new, very strong band at
2051 cmꢀ1 (1), 2054 cmꢀ1 (2) 2073 cmꢀ1 (3), confirming the pres-
ence of the (NCS)ꢀ entity in the complexes [39,41]. The (NCS)ꢀ
group may coordinate to metal through nitrogen or sulfur atoms
[39,41–43]. The absorption bands which occur in the range of
2143–2039 cmꢀ1 (CN stretching), 827–806 cmꢀ1 (CS stretching
for N-bonded) and d(NCS) near at 480 cmꢀ1 (for N-bonded) corrob-
orate the X-ray data on the monodentate coordination of N-bonded
isothiocyanate ligand to Co(II) in 1–3 [39,41–43].
appears to be the first time that the product isolated from the sys-
+
tem [Co(0)–L–M0–NH4
] L = 1-hydroxymethyl-3,5-dimethylpyra-
zole (L) is a neutral cobalt(II) complex. Moreover, it appears that
here, for the first time, hexacoordinate cobalt(II) with ligand LS cre-
ated in situ was found. In the Cambridge Structural Database nine
mono- and dinuclear complexes with LS (N,N,N-substituted 3,5-
dimethylpyrazole amine) ligand have been deposited but only
two of them form hexacoordinate cobalt(II) complexes, however,
they are not both neutral and monomeric [31–34].
The deformation towards tetragonality of the octahedral geom-
etry around the central metal ion in 3 (Table 2) can be related to
the polidentate coordination mode of the organic ligand and mixed
ligand complex formation. Indeed, the Co–(NCS) distances are sig-
nificantly shorter than the other Co–N(organic ligand) distances.
In the crystal structure of 3, there are no conventional hydrogen
bonds. The shortest contacts are listed in Table S3. All these inter-
actions of C–Hꢁ ꢁ ꢁ(NCS) type are weak and they can be seen on the
normalized Hirshfeld surface (Fig. 3b) [35,36]. It is worth noting
that both the lone pair at the sulfur atom and the electron cloud
between carbon and nitrogen atoms are acceptors in the intermo-
lecular interactions. These interactions are arranged in the chain
patterns described by the unitary graph-sets (Table S3) [37,38].
All the chains are formed along three different directions towards
the 21 screw axis or n glide plane.
In addition, the IR spectrum of 1 reveals bands corresponding to
the presence of polyoxoalkoxo vanadates. The strongest bands are
located in the 950–1100 cmꢀ1 region: the O–CH3 (1000–
1100 cmꢀ1) and the V@O (950–1000 cmꢀ1) stretching modes
[24]. A further absorption band located in the 550–650 cmꢀ1 re-
gion is attributed to V–O–V bending [24]. Finally, two bands in
the 400–450 cmꢀ1 region are tentatively assigned to V–O stretch-
ing [24]. The IR spectrum of
1 shows vibration of V@O
(949 cmꢀ1) [44], V–O–V bridging fragments (743, 548 cmꢀ1) [44]
and also V–OCH3 from fragments (594 and 417 cmꢀ1) [39,44].
Coordination of (LS) to Co(II) is also demonstrated in the far-IR re-
gion (400–100 cmꢀ1). In this region, new bands arising from the
stretching vibrations
[39,41,45] and
(Co–NCS) at 270 cmꢀ1 (1), 288 cmꢀ1 (2) and
268 cmꢀ1 (3) [39,41,42,46,47] were observed.
m ) (1–2)
of (Co–N) at (441, 238 cmꢀ1
m

A. Adach et al. / Polyhedron 47 (2012) 104–111
109
3.3. Electronic spectra
The electronic spectra are collected in Table 3 and Figs. 4–6.
The spectra of 1–3 are complicated mainly due to the presence
of more than one crystal field both in 1 (Co(II)-d7 and V(IV)-d1) and
2 (Co(II) ions in the environment of different symmetries. Gener-
ally, for heterometallic transition metal complexes and homome-
tallic of different symmetries more than one crystal field can be
expected. Their detection is not a simple task due to overlapping
bands of low intensity. The complication also arises from some dis-
tortions of the metal environment from the ideal polyhedron (Ta-
bles 1 and 2). However, using a digital filter method, they can be
identified with an assumption of the independent absorption of
the metallic centers [48,49]. Indeed, the crystallographic data con-
firmed that the distances are large enough for such an assumption.
Thus, the electronic spectra of (1–3) enhanced with the digital
filtration have been successfully analyzed adopting the respective
energy diagrams for [CoN4SN]+ (D3h), [CoN4SN2] (D4h
[VO(O)4] (C4v) and [Co(NCS)4] (Td) chromophores.
) and
Fig. 4. Reflectance spectra (a) of [Co(NCS)LS]2[V6O11(CH3O)8]ꢁ(CH3C6H5)4 (1) and
the effect of the digital filtration (b).
In the cationic–anionic complex 1, two central metal atoms, i.e.
Co(II) (d7) and V(IV) (d1) are present. The digitally resolved spectra
allowed detecting an individual absorption in the trigonal bipyra-
midal (D3h) Co(II)(d7) (vide supra) and square pyramidal (C4v
)
V(IV) (d1) crystal fields (Fig. 4).
In general, for a high spin regular trigonal bipyramidal (D3h
)
4
4
[CoL5(NCS)]+ species 4F term (Co(II) d7 conf.) splits into A100, A020,
4
4
4
4E00, E0 and 4P – into A20 (P) and E00(P) [48,52,53]. The reflectance
spectrum of 1 (Fig. 4) exhibits well-resolved bands in the spectral
range 6700–24000 cmꢀ1 attributed to the characteristic transi-
tions of the high-spin five coordinate cobalt(II) complex of the tri-
gonal bipiramidal geometry (Table 3). The data are in line with the
spectra obtained by others: {N2O3} [50], {N4Br} [51], {CoN4Cl}
[29,52,53], and by us [11,12] (3).
4T1g(F)
4E''
CN=4
CN=5
4T2g(F)
4E'
4 T1g(P)
CN=4
4A'(P)
CN=5
CN=4
CN=5
In the 10000–30000 cmꢀ1 absorption region, the oxovana-
dium(IV) species of C4v symmetry are characterized by three low
intensity bands assigned to the following electronic transitions:
4E'(P)
CN=5
C-T
2B2 ? 2E (dxy ? dxy,dyz) and (2B2
!
2B1 ðdxy ! dx
Þ
and
2ꢀy2
2B2
!
2A1ðdxy ! dz Þ [44,48,55]. The spectrum of 1 shows the
2
10000
15000
20000
25000
bands at 13700, 22300 and 25600 cmꢀ1 (Fig. 4). Vanadium com-
plexes containing V@O moiety exhibit electronic spectra which
are distinct from other vanadium(IV) compounds [48,54,55]. In
some cases, the symmetry of the [(V@O)O4] (C4v) is decreasing
~
ν [cm-1]
Fig. 5. Reflectance spectra (a) of [Co(NCS)LS]2[Co(NCS)4]ꢁCH3OH (2) and the effect of
the digital filtration (b).
and, consequently, the degeneracy of eg (dx
moved [24,54,55].
; dz ) orbitals is re-
2ꢀy2
2
The spectrum of complex 3 with broad, weakly structured bands
reveals splitting upon filtration. The mode of the splitting points to a
lowered Oh symmetry towards tetragonality of the [CoN6]
chromophore. Six coordinate cobalt(II) complexes in Oh symmetry
In the spectrum of 2 (Fig. 5), two crystal fields, i.e. the described
above trigonal pyramidal [Co(NCS)(LS)]+ and an anionic tetrahedral
[Co(NCS)4]2ꢀ can be also expected. The bands in the spectrum of 2
(Fig. 5) are asymmetrical. However, the filtration process allowed
us to obtain their positions (Table 3). The transitions at 11700,
17500, 24300 and 24300 cmꢀ1 belong to five coordinate Co(II)
[11,12,40,48,52,53]. The bands at 15400 cmꢀ1 and two shoulders
at 19800 and 22500 cmꢀ1 can be assigned to the tetrahedral
[Co(NCS)4]2 ion [42,43,48] (Fig. 5).
exhibit three spin typical transitions: 4T1g(4F) ? 4T2g
(
m
1),
4
4T1g(4F) ? 4A2g(4F)(
m
2), T1g(4F) ? 4T1g(4P)(
m
3) [48,49,53] (Fig. 6
and Table 3). However, the analysis of the bands revealed their split-
ting, showing a significant lowering symmetry supported by a struc-
tural analysis. The spectrum of [CoLS(NCS)2] 3 is similar to those of
other Co(II) complexes with a tetragonal [CoA2B4] chromophore [49].
Table 3
Electronic spectra of the 1–3 and the literature data for cobalt(II) complexes with LS ligands.
Compound
Band position (
m
max, cmꢀ1
)
[Co(NCS)LS]2[V6O11(CH3O)8] ꢃ 4Toluene (1)
Filtration effect
6700
6820
6820
6770
10500
10450
13100
13110
13000
11660
17100
20070
16700
15430
24100sh
23750
23000br
24190
24200br
24170
24080
16900
12840
13040
22300
22800
[Co(NCS)LS]2[Co(NCS)4] ꢃ CH3OH (2)
Filtration effect
19700
19830
20000
20740
8740
9500br
9660
10630
11550
17520
[Co(NCS)2LS] (3)
Filtration effect
11620
15690
16664
16870br
17160
18725
[CoClLS][ZnLCl2] [19]
[CoClLS][CdBr4] [20]
6790
6820
23720

110
A. Adach et al. / Polyhedron 47 (2012) 104–111
Co(II) ion coordinating both LS and the inorganic anions (I-, Cl-
NCS-). Moreover, the ‘‘anionic metal’’ in cation–anion complexes
always adopts its favorite geometry, i.e. tetrahedral for Zn(II)
[11], Cd(II) [12], and a polyoxometallate form for vanadium (this
work). However, unlike in other studied systems, the process takes
place through a subsequent precipitation of the species. Further-
more, in contrast to previous studies where only cationic–anionic
products were isolated, here, one pot synthesis resulted in the for-
mation of a neutral complex as a final product.
In summary, the isolation of the complexes with such unusual
compositions and architecture can be ascribed to the redox
(Co0 ? CoII) processes and the accompanying in situ formation of
the pyrazole derivative ligand.
Evidently, the direct synthesis as a model of implant corrosions
results in the formation of interesting although still weakly pre-
dictable species and is worthy of further investigation.
Acknowledgments
Fig. 6. Reflectance spectra (a) of complex [Co(NCS)2LS] (3) and the effect of the
digital filtration (b).
The authors are thankful to Ł. Kwas and K. Pietura for their help
in the synthesis of the complexes. Special thanks to Prof. B. Barszcz
for fruitful discussions.
This work was partly supported by the Chemistry Department,
Wrocław University of Technology (Grant No. S10064/ZO304).
The magnetic moment of complex 3 (leff = 4.37 lB) was found
in the range supporting a hexacoordinate symmetry of the Co(II)
ion [46]. The electronic spectra of the range above 30000 cmꢀ1
have been assigned both to intraligand (pyrazole
p ?
p⁄) and
Appendix A. Supplementary data
L ? M CT transitions [30,42,43,56].
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.poly.2012.08.021.
4. Summary and conclusions
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