Complexes of copper(II) and cobalt(II) halides with 4-(3,5-dimethyl-1H- pyrazol-1-yl)-6-methyl-2-phenylpyrimidine: Synthesis, structures, and properties

Article abstract of DOI:10.1134/S1070328409080077

Copper(II) and cobalt(II) complexes with 4-(3,5-dimethyl-1H-pyrazol-1-yl)- 6-methyl-2-phenylpyrimidine (L) of the general formula MLX₂ (M = Cu(II), X = Cl and Br; M = Co(II), X = Cl, Br, and I) were obtained. According to X-ray diffraction data

Full text of DOI:10.1134/S1070328409080077

ISSN 1070-3284, Russian Journal of Coordination Chemistry, 2009, Vol. 35, No. 8, pp. 597–608. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © M.B. Bushuev, V.P. Krivopalov, E.V. Peresypkina, A.V. Virovets, Yu.G. Shvedenkov, L.A. Sheludyakova, N.V. Semikolenova, V.A. Zakharov, S.V. Larionov,
2009, published in Koordinatsionnaya Khimiya, 2009, Vol. 35, No. 8, pp. 606–617.
Complexes of Copper(II) and Cobalt(II) Halides
with 4-(3,5-Dimethyl-1H-Pyrazol-1-yl)-6-Methyl-2-
Phenylpyrimidine: Synthesis, Structures, and Properties
M. B. Bushueva,b*, V. P. Krivopalovc, E. V. Peresypkinaa, A. V. Virovetsa, Yu. G. Shvedenkova,
L. A. Sheludyakovaa, N. V. Semikolenovad, V. A. Zakharovd, and S. V. Larionova
a Nikolaev Institute of Inorganic Chemistry, Siberian Division, Russian Academy of Sciences,
pr. akademika Lavrent’eva 3, Novosibirsk, 630090 Russia
b Novosibirsk State University, Novosibirsk, Russia
c Vorozhtsov Institute of Organic Chemistry, Siberian Division, Russian Academy of Sciences, Novosibirsk, Russia
d Boreskov Institute of Catalysis, Siberian Division, Russian Academy of Sciences,
pr. akademika Lavrent’eva 5, Novosibirsk, 630090 Russia
E-mail: bushuev@che.nsk.su
Received December 16, 2008
Abstract—Copper(II) and cobalt(II) complexes with 4-(3,5-dimethyl-1H-pyrazol-1-yl)-6-methyl-2-phenylpyri-
midine (L) of the general formula MLX2 (M = Cu(II), X = Cl and Br; M = Co(II), X = Cl, Br, and I) were obtained.
According to X-ray diffraction data, CuLBr2 and CoLX2 (X = Cl, Br, and I) are mononuclear molecular com-
plexes. The ligand L is coordinated to the metal atom in a chelating bidentate fashion through the N atoms of the
pyrimidine and pyrazole rings. The coordination polyhedron of the metal atom is extended to a distorted tetrahe-
dron by two halide ions. In solution, CuLBr2 undergoes slow transformation into CuL(1–x)L'xBr2 and the binuclear
(X-ray diffraction data) Cu(I) complex [CuL(1–x)L'xBr]2 (L' is 4-(4-bromo-3,5-dimethyl-1H-pyrazol-1-yl)-6-
methyl-2-phenylpyrimidine). The complexes MLX2 show weak antiferromagnetic interactions between the
M2+ ions.
DOI: 10.1134/S1070328409080077
A search for 3d-metal complexes, which are active for ethene polymerization than a complex of CuCl2 with
components of catalytic systems, is a promising avenue
in coordination chemistry and catalysis. Vanadium,
iron, cobalt, and nickel complexes with nitrogen-con-
taining organic ligands in the presence of organoalumi-
num compounds as cocatalysts catalyze olefin poly-
merization [1–6]. Complexes of CuCl2 with bidentate
α-diimino [7] and bis(benzoimidazole) ligands [8] are
also active in this reaction. Most of the complexes stud-
ied contain identical coordination fragments. At the
same time, attention is given to the synthesis and inves-
an α-diimino ligand [13]. At present, the development
of methods for targeted synthesis of complexes capable
of catalyzing olefin polymerization necessitates a
search for “composition–structure–property” correla-
tions. In this step of our investigations, we should
reveal correlations between the ligand structure, the
nature of the central atom, and the properties of the
complexes.
Additional interest in the synthesis of transition
tigation of complexes consisting of various coordina- metal complexes with pyrazolylpyrimidines is due to a
tion fragments [9]. We began to synthesize 3d-metal
complexes with polyheteroatomic ligands containing
five- and six-membered azaheterocycles (pyrazolylpy-
rimidines). Because heterocyclic fragments have sev-
eral N atoms and the pyrazole ring can be attached to
the pyrimidine one in different positions, pyrazolylpy-
rimidines can be coordinated by metal atoms to form
complexes with various compositions and structures
[10–12]. We found that mononuclear complexes of
CuCl2 and CuBr2 with 2-(3,5-diphenyl-1ç-pyrazol-1-
broad spectrum of biological activity of these nitroge-
neous heterocycles [14–22]. Since complexes with sim-
ilar hybrid ligands (pyrazolylpyrazines and pyra-
zolylpyridines) are magnetically active [23–25], pyra-
zolylpyrimidines can serve as potential ligands for the
preparation of complexes with attractive magnetic
properties (including those with spin transitions).
Earlier, we obtained a new ligand of this class,
namely, 4-(3,5-dimethyl-1ç-pyrazol-1-yl)-6-methyl-
yl)-4,6-diphenylpyrimidine are more active catalysts 2-phenylpyrimidine (L), and its complex CuLCl2 (I)
597

598
BUSHUEV et al.
Table 1. Elemental analysis data for complexes I, II, and
IV–VI
grade) at 160°ë. Fractionated EtOH, iso-PrOH, CHCl3
(reagent grade), and MeCN (analytical grade) were
employed as solvents. Reagent L and complex I were
obtained as described in [26].
Synthesis of CuLBr2 (II). A suspension of L
(0.12 g, 0.5 mmol) in ethanol (7 ml) was added drop-
wise to a stirred solution of CuBr2 (0.11 g, 0.5 mmol) in
ethanol (3 ml). The mixing resulted, within a few sec-
onds, in the formation of a reddish brown precipitate.
The suspension was stirred for an hour. The precipitate
was filtered off, washed with ethanol, and dried in air.
The yield was 0.16 g (66%).
Content (found/calculated), %
Complex
M
C
H
N
C16H16N4Cl2Cu (I) 15.6/15.9 48.4/48.2 4.1/4.0 14.1/14.0
CuLCl2
C16H16N4Br2Cu (II) 12.6/13.0 38.6/39.4 3.3/3.3 11.2/11.5
CuLBr2
Reddish brown single crystals of two phases crystal-
lized from a solution of complex II in iso-PrOH–MeCN
'
(2 : 1). The crystals are solid solutions CuL(1 – x)Lx Br2,
C16H16N4Cl2Co(IV) 14.8/15.0 48.8/48.8 4.2/4.1 14.3/14.2
where L' is 4-(4-bromo-3,5-dimethyl-1ç-pyrazol-1-yl)-6-
methyl-2-phenylpyrimidine. X-ray diffraction analysis
was carried out for crystals selected a day (IIa) and several
days (IIb) after the start of the crystallization. Further
crystallization gave orange single crystals of a copper(I)
CoLCl2
C16H16N4Br2Co (V) 11.9/12.2 38.9/39.8 3.4/3.3 10.8/11.6
CoLBr2
'
complex, namely, the solid solution [CuL(1 – x)Lx Br]2
(III).
C16H16N4I2Co (VI) 10.1/10.2 30.4/33.3 3.1/2.8 9.3/9.7
CoLI2
Synthesis of CoLCl2 (IV), CoLBr2 (V), and CoLI2
(VI). A hot solution of ligand L (0.26 g, 1 mmol) in iso-
propyl alcohol (10–15 ml) was added dropwise to a
stirred hot solution of an appropriate Co(II) salt
(1 mmol; 0.13 g for CoCl2, 0.22 g for CoBr2, and 0.35 g
for CoI2 · 2H2O) in isopropyl alcohol (5 ml). The mixing
resulted, in two to three minutes, in the formation of
blue (complexes IV, V) and green precipitates (VI). The
reaction mixture was heated while stirring it for 1–2 h.
The precipitates were filtered off and washed in a bea-
ker with isopropyl alcohol (3–4 ml) under heating
while stirring the mixture for 1 h. The precipitates were
filtered off, washed with a small amount of isopropyl
alcohol, and dried in air. The yields of complexes IV, V,
and VI were 0.31 g (79%), 0.31 g (64%), and 0.35 g
(61%), respectively.
and characterized them by X-ray diffraction analysis
[26].
N
3
N
N
N
2
(L)
Single crystals of complexes IV–VI were grown by
slow crystallization from their solutions in CH2Cl2–
MeCN (1 : 1).
The metal content of complexes I, II, and IV–VI
was determined by complexometric titration following
the decomposition of their samples in a mixture of con-
centrated H2SO4 and HNO3. An analysis for C, H, and
N was performed on a Carlo Erba analyzer according to
a standard procedure. The elemental analysis data are
given in Table 1.
Associated polymorphism was revealed for I: the
complex crystallizes into three polymorphous modifi-
cations with different colors: light green (2G), emerald
green (2EG), and orange (2O) [26]. The structures of
the polymorphs mainly differs in the packing of I mol-
ecules in the solid state by means of various intermolec-
ular π−π interactions. Thus, because of stacking, com-
plexes of this class are of interest for the creation of
molecular ensembles.
The goal of this study was to obtain complexes of
Cu(II) and Co(II) halides with ligand L and examine
their structures and magnetic and catalytic properties.
Electronic reflection spectra were recorded on a
Unicam 700A spectrophotometer in the 340–2500 nm
range. Electronic absorption spectra of solutions of the
complexes in CHCl3 (II, V, and VI) and CHCl3–MeCN
(I and IV) were recorded on a UV-3101 PC spectropho-
tometer (Shimadzu) in the 200–2500 nm range. IR
EXPERIMENTAL
The salts CuCl2 · 2H2O, CuBr2, CoI2 · 2H2O (high- absorption spectra were measured on Scimitar FTS
purity grade), and CoCl2 (analytical grade) were used; 2000 (375–4000 cm–1) and BOMEM MB-102 spectro-
CoBr2 was prepared by keeping CoBr2 ·6H2O (analytical photometers (200–400 cm–1).
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 35 No. 8 2009

COMPLEXES OF COPPER(II) AND COBALT(II) HALIDES
599
Magnetic properties were studied on an MPMS-5s L was 1 : 1 (ÒM ≈ 0.05–0.07 mol/l). To avoid precipita-
SQUID-magnetometer (Quantum Design) in the
2−300 K range with an applied magnetic field strength
of 5 kOe. In calculation of molar magnetic susceptibil-
ity c, the diamagnetism of the atoms was included via
the Pascal additive scheme. The effective magnetic
moment was calculated as µeff ≈ (8χT)1/2.
tion of some amount of the nonconsumed ligand L, the
metal salt should be used in a small excess with respect
to the reaction stoichiometry and the resulting precipi-
tate should be thoroughly washed as described in the
Experimental section. The complexes obtained are
moderately soluble in ethanol, acetonitrile, isopropyl
alcohol, dichloromethane, and chloroform and are neg-
ligible soluble in toluene. They decompose in water.
Complexes I, II, V, andVI are stable in air. When stored
in air, complex IV gradually decomposes for several
weeks into cobalt(II) chloride hydrates and free ligand
L, the IR spectrum of a stored sample no longer con-
tains the ν(OH) and ν(Co–O) bands but it shows the
ν(Co–N) and ν(Co–Cl) bands. Single crystals of com-
plex II were not obtained because of partial bromina-
tion of ligand L in position 4 of the pyrazole ring when
keeping its solution for a while. Single crystals of struc-
X-ray diffraction analysis of phases IIa, IIb, and
III–VI was carried out on a Bruker-Nonius X8Apex
CCD automated four-circle diffractometer (åÓäα radi-
ation, λ = 0.71073 Å, graphite monochromator) accord-
ing to a standard procedure. Crystallographic parame-
ters and a summary of data collection are given in
Table 2. The reflection intensities were measured in the
ϕ- and ω scan modes for narrow frames (0.5°) up to
2θ = 55°. Absorption correction was applied empiri-
cally with the SADABS program [27]. All six struc-
tures were solved by the direct method and refined by
the full-matrix least-squares method on F2 in the aniso-
tropic approximation for non-hydrogen atoms
(SHELX-97) [28]. Since the crystals of phases IIa and
IIb are isostructural with those of complex I (poly-
morph 2G) studied in [26], we performed structure
refinement according to a known model. The H atoms
were refined in the rigid-body approximation. In struc-
tures IIa, IIb, and III, the position at the C(4) atom of
the pyrazole fragment of ligand L is statistically occu-
pied by the H and Br atoms. The relative weight of the
Br atom refined at fixed thermal parameters is
0.0015(2), 0.076(1), and 0.900(4) in structures IIa, IIb,
and III, respectively. The crystals of complex IV are
isostructural with those of complex I (2O) [26]. The
crystals of complexes V and VI are isostructural with
each other. Atomic coordinates and thermal parameters
have been deposited with the Cambridge Crystallo-
graphic Data Collection (nos. 711439–711444).
Selected bond lengths and angles in six complexes are
given in Table 3. The environment and molecular pack-
ing in the crystal structures were analyzed with the
TOPOS 4.0 Professional program package [29].
'
tures IIa and IIb are solid solutions CuL(1 – x)Lx Br2 (X-
ray diffraction data). The fraction of the Br atoms in
position 4 of the pyrazole ring is ~1.5 and 7.6% in IIa
and IIb, respectively. Thus, phase IIa corresponds to
high-purity complex II. Apparently, the formation of
such solid phases is due to the reduction of Cu(II) in
complex II with Br– ions in solution. This results in
evolution of Br2 and partial bromination of the pyrazole
ring of ligand L. When kept for several days, the crys-
tallization solution produces copper(I) complex III as
'
orange crystals of the solid solution [CuL(1 – x)Lx Br]2
(x = 0.90). The observed reduction of Cu(II) to Cu(I)
with Br– ions agrees with data in [30, 31]. In contrast to
data in [13], according to which copper(II) is also
reduced to copper(I) in a complex of CuBr2 with 2-(3,5-
diphenyl-1ç-pyrazol-1-yl)-4,6-diphenylpyrimidine,
this reduction is accompanied by bromination of the
pyrazole ring of ligand L in our case. This is favored by
the presence of less bulky and more electron-donating
methyl groups compared to the phenyl substituents in
2-(3,5-diphenyl-1ç-pyrazol-1-yl)-4,6-diphenylpyrimi-
dine [13]. Similar examples of halogenation have been
cited in [32–34]. The bromination at position 4 of the
pyrazole ring, which is a π-abundant heterocyclic frag-
ment in ligand L, suggests its electrophilic mechanism.
Thus, the reduction of copper(II) to copper(I) occurs
very slowly and is accompanied by bromination of
ligand L. To elucidate the details of these transforma-
tions, further investigations are required. The overall
Complexes I, II, and V were tested in ethene poly-
merization with methylaluminoxane as a cocatalyst
(Pethene = 10 atm, T = 35°C, 70 ml of toluene, [M] = 3 ×
10–5 mol/l, molar ratio Alcocat : M = 500 (M = Cu and
Co)).
RESULTS AND DISCUSSION
Complexes I and IV–VI were obtained by heating
alcoholic solutions of appropriate metal salts and
ligand L. In the synthesis of complex II, heating is
unwanted because of partial reduction of complex II
(the dark precipitate of the complex contains light
inclusions). The precipitates of the complexes form
shortly after the mixing of the solutions. The ratio M : scheme of transformations is as follows:
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 35 No. 8 2009

600
BUSHUEV et al.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 35 No. 8 2009

COMPLEXES OF COPPER(II) AND COBALT(II) HALIDES
601
Table 3. Selected bond lengths d and bond (ω) and torsion angles (ϕ) in structures II–VI
IIa
IIb
III
IV
V
VI
Complex
(M = Cu, X = Br) (M = Cu, X = Br) (M = Cu, X = Br) (M = Co, X = Cl) (M = Co, X = Br) (M = Co, X = I)
d, Å
M(1)–X(1)
2.3536(5)
2.3314(5)
2.3503(8)
2.3264(8)
2.3632(6)
2.3632(6)
3.0203(9)
1.987(3)
2.455(3)
1.412(5)
1.470(5)
1.329(5)
1.353(5)
1.489(5)
1.370(4)
1.388(5)
1.416(4)
1.327(4)
1.381(5)
1.508(5)
1.336(5)
1.482(5)
1.335(4)
1.343(4)
1.377(6)
1.391(5)
1.375(6)
1.360(6)
1.376(6)
1.380(5)
1.386(4)
1.868(4)
2.2389(3)
2.2286(4)
2.3604(3)
2.3595(3)
2.5519(3)
2.5510(3)
M(1)–X(2)
M(1)–M(1')*
M(1)–N(1)
M(1)–N(4)
C(3)–C(4)
C(3)–C(31)
C(3)–N(1)
C(4)–C(5)
C(5)–C(51)
C(5)–N(2)
C(6)–C(7)
C(6)–N(2)
C(6)–N(4)
C(7)–C(8)
C(8)–C(81)
C(8)–N(3)
C(9)–C(10)
C(9)–N(3)
C(9)–N(4)
C(10)–C(11)
C(10)–C(15)
C(11)–C(12)
C(12)–C(13)
C(13)–C(14)
C(14)–C(15)
N(1)–N(2)
C(4)–Br(3)
Br(3)···Br(3')*
1.998(3)
2.014(3)
1.400(5)
1.486(5)
1.347(4)
1.369(5)
1.496(5)
1.374(4)
1.382(4)
1.406(4)
1.350(4)
1.386(5)
1.493(5)
1.349(4)
1.476(4)
1.329(4)
1.358(4)
1.394(5)
1.383(5)
1.389(5)
1.377(5)
1.379(5)
1.389(5)
1.389(4)
1.74(3)
2.005(4)
2.024(3)
1.406(7)
1.475(6)
1.340(5)
1.360(6)
1.493(7)
1.380(5)
1.374(5)
1.401(5)
1.344(5)
1.382(6)
1.502(6)
1.337(5)
1.483(5)
1.326(5)
1.350(5)
1.392(6)
1.375(6)
1.378(7)
1.388(7)
1.356(7)
1.394(7)
1.378(5)
1.784(7)
2.766(13)
2.0193(10)
2.0634(10)
1.4091(17)
1.4870(17)
1.3296(15)
1.3712(16)
1.4893(16)
1.3809(15)
1.3809(15)
1.4055(14)
1.3492(15)
1.3951(17)
1.4983(16)
1.3448(17)
1.4771(17)
1.3373(15)
1.3515(14)
1.3965(17)
1.3980(19)
1.390(2)
2.0052(14)
2.0929(15)
1.408(2)
1.484(3)
1.330(2)
1.364(3)
1.491(2)
1.386(2)
1.380(3)
1.393(2)
1.353(2)
1.389(2)
1.500(3)
1.330(2)
1.483(2)
1.350(2)
1.357(2)
1.397(2)
1.394(3)
1.388(3)
1.390(3)
1.385(3)
1.389(3)
1.382(2)
2.0037(15)
2.0875(16)
1.414(3)
1.483(3)
1.331(2)
1.364(3)
1.490(3)
1.386(2)
1.385(3)
1.395(2)
1.352(2)
1.392(2)
1.493(3)
1.354(2)
1.481(2)
1.330(2)
1.359(2)
1.403(2)
1.388(3)
1.394(3)
1.381(3)
1.391(3)
1.391(3)
1.380(2)
1.391(2)
1.387(2)
1.3910(18)
1.3812(13)
2.83(6)
Angle
ω, deg
X(1)–M(1)–X(2)
N(1)–M(1)–X(1)
N(1)–M(1)–X(2)
N(4)–M(1)–X(1)
N(4)–M(1)–X(2)
N(1)–M(1)–N(4)
101.62(2)
136.60(8)
102.95(8)
96.14(8)
149.03(8)
80.12(11)
101.77(3)
136.51(10)
102.94(10)
96.70(9)
148.64(9)
79.62(13)
103.87(2)**
111.64(9)
133.75(10)** 103.95(3)
124.12(8)
109.72(7)**
73.50(11)
111.053(12)
120.78(3)
113.130(12)
118.73(5)
110.64(4)
104.02(4)
127.72(4)
79.38(6)
112.598(10)
118.67(5)
110.97(5)
103.13(4)
129.17(4)
79.35(6)
109.43(3)
129.81(3)
78.81(4)
Angle
ϕ, deg
N(3)–C(9)–C(10)–C(11)
C(5)–N(2)–C(6)–C(7)
32.2(5)
15.2(6)
31.3(5)
14.8(6)
17.7(6)
34.0(6)
42.35(17)
12.5(2)
37.89(18)
18.9(3)
37.5(2)
17.9(3)
Deviation from the plane N(1)–N(2)–C(6)–N(4), Å
M(1)
X(1)
X(2)
0.426(5)
2.316(7)
–0.24(1)
0.437(6)
2.335(8)
–0.24(1)
0.445(7)
–1.14(1)
–1.29(1)
–0.050(2)
1.756(3)
–1.772 (3)
0.277(3)
2.465(4)
–1.201(5)
0.275(3)
2.642(4)
–1.273(5)
Notes: * The symmetry operation code is –x + 1, –y, –z + 1.
** The angles are given for X(2) = Br(1').
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 35 No. 8 2009

602
BUSHUEV et al.
N
N
N
N
MX2
N
N
N
N
M
X
X
(L)
M = Cu, X = Cl (I);
M = Co, X = Cl (IV), Br (V), I (VI)
CuBr2
N
N
N
N
Cu
Br
Br
BrxH(1 – x)
(II)
N
N
N
N
Cu
Br
Br
BrxH(1 – x)
Cu
N
N
+
+
N
N
N
N
N
N
Cu
Br
Br
BrxH(1 – x)
LxBr]2 (III: x = 0.90)
'
LxBr2
CuL
'
[CuL
(1 – x)
(1 – x)
(IIa: x = 0.015; IIb: x = 0.076)
Solid phases IIa and IIb are built from the mole- for the space group C2/c showed that these crystals are
cules of mononuclear copper(II) complexes containing
ligands L and L' and Br– ions (Fig. 1). The coordination
polyhedron of the Cu atom is a distorted tetrahedron
made up of the N(1) and N(4) atoms and the bromide
ions. The coordination of ligands L and L' results in clo-
sure of the five-membered chelate ring CuN3C. In struc-
tures IIa and IIb, the degree of replacement of the H
atoms by Br atoms virtually does not affect the bond
lengths in the pyrazole ring: the differences do not
exceed the standard deviation (Table 3). Solid phase III
is built from the molecules of a binuclear copper(I)
complex with two bridging Br atoms between the Cu
atoms (Fig. 2). The coordination of ligands L and L'
results in closure of the five-membered chelate ring
CuN3C. The degree of replacement of the H atoms by
the Br atoms in position 4 of the pyrazole ring is 90%.
'
the solid solution L(1 – x)Lx (x ≈ 0.6). Unfortunately, the
quality of the crystal precluded us from obtaining the R
factor below 10% in a model allowing for pseudomero-
hedral twinning. The Br content is ~60% (after the
refinement of position multiplicity). The atomic coordi-
nates in compound VII are omitted because of the low
accuracy of structure determination. The solid solution
obtained is not isostructural with the starting ligand L
[26]. In both structures, the conformation of pyra-
zolylpyrimidine is identical; the orientation of the pyra-
zole fragment relative to the pyrimidine one is opposite
to the conformation of ligands L coordinated by the
metal atom. In structure L [26], molecules are stacked
by π–π–interactions, lying exactly above each other
'
(motif AAA…). Structure L0.4L0.6 also shows molecu-
lar π-stacking (Fig. 3). However, its molecules are alter-
nately rotated with respect to each other, thus making
the sequence ABAB… Apparently, the presence of the
Br atoms makes the stacking motif AAA… unfeasible
Removal of the solvent from the crystallization mix-
ture gave a small amount of yellowish needlelike crys-
tals (compound VII); the parameters of its face-cen-
tered monoclinic unit cell are a = 7.224(3), b =
22.689(10), c = 19.151(9) Å, β = 100.304(12)°, V =
…
because a very short intermolecular contact Br Br
3088(2) Å3. The X-ray diffraction analysis performed (~3.5 A) dictated by π-stacking interactions between
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COMPLEXES OF COPPER(II) AND COBALT(II) HALIDES
603
the metal atom in a chelating bidentate fashion through
the N(1) and N(4) atoms to form five-membered chelate
rings CoN3C.
C(81)
C(7)
C(6)
C(8)
C(51)
Unlike the complex CuLCl2 [26], the complexes
CoLHal2 show no polymorphism. The crystals of com-
plex IV are isostructural with those of complex I (poly-
morph 2O) [26]. In the crystal of complex IV, the
planes of the π-systems in uneven molecular stacks are
spaced at 3.55 and 4.81 Å. In polymorph 2O, the corre-
sponding values are 3.63 and 4.67 Å, which suggests an
increased fraction of pair interactions in stacks for com-
plex IV. This can be due to a conformational difference
between structures 2O and IV: in complex IV, the rela-
tive angle between the pyrimidine and pyrazole rings is
greater almost by 10° than that in polymorph 2O and
the angle between the planes of the phenyl substituent
and the pyrimidine ring is also greater (Table 3).
N(3)
C(5)
C(4)
N(2)
C(9)
C(10)
N(4)
C(11)
C(3)
N(1)
Cu(1)
C(15)
C(14)
C(12)
C(13)
Br(1)
C(31)
Br(2)
Fig. 1. Molecular structure IIa with atomic thermal dis-
placement ellipsoids (50% probability).
Packing of isostructural crystals V and VI has no
analogs among the polymorphs of CuLCl2. In the crys-
tal, stacked pyrimidine rings are spaced at 3.65 and
3.56 Å for V and VI, respectively, to form π-stacking
dimeric ensembles. Similar dimeric ensembles have
been found in complex I (polymorph 2EG) [26]. How-
ever, in complexes V and VI, the π-stacking interaction
involves only the pyrimidine fragment of the ligand
(Table 3), while in polymorph 2EG, both the pyrimi-
dine and pyrazole rings participate in π–π interactions
[26]. Apparently, this structural feature accounts for the
existence of a new structural type for the complexes
CoLX2 (X = Br and I). In both structures, packed dimers
the molecules becomes inevitable. To prevent this
unwanted contact, the stacked molecules are rotated
with partial retention of the π-stacking contacts. This is
indirectly confirmed by the absence of noticeable inter-
molecular contacts Br···Br (< 3.95 Å characteristic of
normal van der Waals contacts [35]), except for ran-
domly occurring shortened contacts (3.75 Å) between
adjacent molecules in a stack.
Complexes IV–VI are structurally similar (Fig. 4).
The coordination polyhedra in the complexes are dis-
torted tetrahedra CoLHal2. Ligands L are coordinated to are sloping toward each other to make a peculiar “par-
Br(3)
C(31)
C(4)
C(5)
C(3)
C(51)
Br(1)
N(1)
Cu(1)
N(2)
C(6)
C(7)
C(8)
N(4)
C(9)
C(15)
C(81)
C(14)
N(3)
C(10)
C(11)
C(12)
C(13)
Fig. 2. Molecular structure III with atomic thermal displacement ellipsoids (50% probability).
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 35 No. 8 2009

604
BUSHUEV et al.
z
0
y
Fig. 3. Molecular packing in the crystal structure L L'
.
0.4
0.6
quet” stacking and their centers form a distorted body- ligand L, the band due to the phenyl ring is difficult to
identify because of conjugation of the double bonds. In
contrast, the spectra of the complexes show a band of
the phenyl substituent at 1604–1599 cm–1. This sug-
gests a changed geometry of the coordinated ligand L,
viz., the diminished conjugation between the phenyl
and pyrimidine rings, which agrees with X-ray diffrac-
tion data for ligand L and its complexes. In the low-fre-
quency range, the spectra of the complexes exhibit
bands due to ν(M–N) and ν(M–Hal) stretches (Table 4).
The ν(M−N) bands appear at 407–504 cm–1 for all com-
plexes. For the ν(M–Hal) bands, the frequency ratios
ν(M–Br)/ν(M–Cl) are close to the literature data (0.77–
0.74) [36]; the frequency ratio ν(Co–I)/ν(Co–Cl) also
correlates with the literature data (~ 0.65) [36].
centered cubic packing (Fig. 5).
In ligand L, the pyrazole and pyrimidine rings
absorb at 1589–1535 cm–1 (stretching bends; Table 4).
In the IR spectra of metal complexes with ligand L, the
system of these bands changes substantially because of
its coordination by metal atoms. In the spectrum of free
C(81)
C(51)
C(7)
C(6)
C(8)
N(3)
The electronic absorption and reflection spectra of
complexes I, II, and IV–VI are given in Table 5. The
number and positions of the bands in the spectra of
complexes IV–VI is consistent with the distorted tetra-
hedral structure of the coordination polyhedron of the
Co atom. The spectra contain three structured bands.
The close positions of analogous peaks in the electronic
absorption and reflection spectra suggest the retention
of the compositions and structures of the complexes
upon their dissolution. The near-IR range shows a wide
asymmetric band due to the transitions to the compo-
nents of the term 4í1(F) [37]. A wide band of the term
4í1(P) is split into two (complexes V and VI) or three
C(5)
N(2)
N(1)
C(9)
N(4)
Co(1)
C(4)
C(3)
C(11)
C(10)
C(12)
C(13)
C(15) C(14)
C(31)
X(1)
X(2)
Fig. 4. Molecular structure of complexes IV–VI with
atomic thermal displacement ellipsoids (50% probability).
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COMPLEXES OF COPPER(II) AND COBALT(II) HALIDES
605
(‡)
y
0
x
(b)
Fig. 5. (a) Centrosymmetric π–π-stacking dimer in structure VI and (b) packing of the dimers in the crystal.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 35 No. 8 2009

606
BUSHUEV et al.
Table 4. Selected frequencies in the IR spectra (cm–1) of free ligand L and its complexes
Compound
(ν + δ) (of the ring)
ν(Ph)
ν(M–N)
ν(M–Hal)
331, 311
L
1589, 1582, 1567, 1535 sh
1582, 1570, 1560 sh, 1535
1581, 1570, 1560, 1534
CuLCl2 (I)
CuLBr2 (II)
CoLCl2 (IV) 1592 sh, 1578, 1570,
1599
1599
1604
499, 446, 407
499, 444, 407
504, 439, 407
271, 255, 243
342, 330, 321
1560 sh, 1540 sh, 1530
CoLBr2 (V)
CoLI2 (VI)
1579, 1571, 1560, 1541, 1527
1579, 1570, 1560, 1540, 1527
1600
1599
503, 440, 407
504, 442, 407
274, 251, 242
230
Table 5. Electronic absorption and reflection spectra of complexes I, II, and IV–VI
Electronic reflection
Electronic absorption spectrum
spectrum
Complex
Transition
ν, cm–1
ε, l mol–1 cm–1
ν, cm–1
CuLCl2 (I)
25700
21900
12750
9490
22800
12500
748
190
CuLBr2 (II)
CoLCl2 (IV)
22700
17400
11900
1075
499
21400
17400
12 260 sh
8900
274
27800
18100
17600
16300
14800
9090
278
318
398
4A2
4T1(P)
15200
9490 sh
7400
25.2
37.2
4A2
4T1(F)
7210
CoLBr2 (V)
CoLI2 (VI)
27800
17320
14900
9120 sh
7370
17240
14900
160
328
4A2
4A2
4T1(P)
4T1(F)
7246
24400
16100
14700
37.0
2218
300
23600
16200
15000
4A2
4T1(P)
4T1(F)
657
8770 sh
7370
4A2
7100
81
components (IV); i.e., the symmetry of the coordina-
For complexes I and II, the µeff values are virtually
tion polyhedron is lower than Td. The intensities of the temperature-independent down to 20 K (Fig. 6); µeff =
components of both bands correlate with the literature 1.78 and 1.77 µB for complexes I and II, respectively,
data [37]. The high-frequency bands (at ~25000– approximate to the purely spin magnetic moment
28000 cm–1) are more intense and seem to be charge- (1.73 µB) for non-interacting Cu2+ ions with the spin S =
transfer bands.
1/2 and g = 2. Below the liquefaction temperature of
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 35 No. 8 2009

COMPLEXES OF COPPER(II) AND COBALT(II) HALIDES
µeff, µB
607
(‡)
5.0
4.5
4.0
3.5
µeff, µB
(b)
1.78
1.77
1.76
1.75
0
50 100 150 200 250 T, K
150 200 250 T, K
0
50
100
Fig. 6. Plots of µ vs. T for complexes (a) VI and (b) I.
eff
helium, µeff(T) for complexes I and II decreases to positions of the pyrazole and pyrimidine rings and the
1.76–1.75 µB, which suggests weak antiferromagnetic presence of dissimilar substituents in positions 3 and 5
interactions between Cu2+ ions. Since the magnetic of the pyrazole ring).
behavior of Cu(II) complexes (I and II), as well as that
of Co(II) complexes (IV–VI), is virtually identical,
here we present experimental curves µeff(T) only for
ACKNOWLEDGMENTS
complexes I and VI. At room temperature, µeff is 4.55,
4.58, and 4.87 µB for IV, V, and VI, respectively. With a
decrease in the temperature to 160 K, the above µeff val-
ues show a gradual decline to 4.40, 4.39, and 4.74 µB.
Such a run of the curve µeff(T) is mainly due to the spin-
orbital couplings of the Co2+ ions. In the temperature
range from 50 to 150 K, the µeff values remain nearly
constant (4.40, 4.39, and 4.74 µB). This is above a the-
oretical limit (3.87 µB) for non-interacting Co2+ ions
with the spin S = 3/2 and g = 2. In this case, the orbital
contribution to the magnetic moment of Co2+ ions also
plays a part. Below 50 K, µeff decreases to 3.39, 3.43,
and 3.77 µB (2 K) for complexes IV, V, and VI, respec-
tively. This suggests dominant antiferromagnetic inter-
actions between Co2+ ions. According to the curves
µeff(T) obtained for complexes IV–VI, the efficiency of
these interactions is low (≤1 cm–1).
We are grateful to I.V. Yushina for recording the
electronic absorption spectra of the complexes and to
V.A. Blatov (Samara State University) for providing the
TOPOS 4.0 Professional program package.
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