Cu(II) and Cu(I) complexes with 2-(3,5-diphenyl-1H-pyrazole-1-yl)-4,6-diphenylpyrimidine: Synthesis and structure. Catalytic activity of Cu(II) compounds in reaction of ethylene polymerization

Article abstract of DOI:10.1134/S1070328406030067

The Cu(II) and Cu(I) complexes with 2-(3,5-diphenyl-1H-pyrazole-1-yl)-4,6-diphenylpyrimidine (L) of the composition CuLX₂ (X = Cl, Br) and CuL(MeCN)Br are synthesized. According to X-ray diffraction data, the complexes have molecular structures. The molecules L are coordinated to the copper atom in bidentate-cyclic mode, i.e., through the N² atom of pyrazole and N¹ atom of pyrimidine rings. The coordination polyhedron of the Cu²⁺ ion in CuLX₂ compounds is completed to a distorted tetrahedron with halide ions, that of the Cu⁺ ion in CuL(MeCN)Br compounds, with the bromide ion and the nitrogen atom of acetonitrile molecule. The CuLX₂ complexes (X = Cl, Br) in combination with cocatalysts (methylaluminoxane and triisobutylaluminium) exhibit catalytic activity in ethylene polymerization. Pleiades Publishing, Inc. 2006.

Full text of DOI:10.1134/S1070328406030067

ISSN 1070-3284, Russian Journal of Coordination Chemistry, 2006, Vol. 32, No. 3, pp. 199–207. © Pleiades Publishing, Inc., 2006.
Original Russian Text © M.B. Bushuev, V.P. Krivopalov, N.V. Semikolenova, E.V. Peresypkina, A.V. Virovets, L.A. Sheludyakova, L.G. Lavrenova, V.A. Zakharov, S.V. Larionov,
2006, published in Koordinatsionnaya Khimiya, 2006, Vol. 32, No. 3, pp. 208–216.
Cu(II) and Cu(I) Complexes with
2-(3,5-Diphenyl-1H–pyrazole-1-yl)-4,6-diphenylpyrimidine:
Synthesis and Structure. Catalytic Activity of Cu(II) Compounds
in Reaction of Ethylene Polymerization
M. B. Bushuev*, V. P. Krivopalov**, N. V. Semikolenova***, E. V. Peresypkina*,
A. V. Virovets*, L. A. Sheludyakova*, L. G. Lavrenova*, V. A. Zakharov***, and S. V. Larionov*
*Nikolaev Institute of Inorganic Chemistry, Siberian Division, Russian Academy of Sciences, pr. Akademika Lavrent’eva 3,
Novosibirsk, 630090 Russia
**Novosibirsk Institute of Organic Chemistry, Siberian Division, Russian Academy of Sciences, Novosibirsk, Russia
***Boreskov Institute of Catalysis, Siberian Division, Russian Academy of Sciences, pr. Akademika Lavrent’eva 3,
Novosibirsk, 630090 Russia
Received June 21, 2005
Abstract—The Cu(II) and Cu(I) complexes with 2-(3,5-diphenyl-1H-pyrazole-1-yl)-4,6-diphenylpyrimidine
(L) of the composition CuLX2 (X = Cl, Br) and CuL(MeCN)Br are synthesized. According to X-ray diffraction
data, the complexes have molecular structures. The molecules L are coordinated to the copper atom in biden-
tate-cyclic mode, i.e., through the N2 atom of pyrazole and N1 atom of pyrimidine rings. The coordination poly-
hedron of the Cu2+ ion in CuLX2 compounds is completed to a distorted tetrahedron with halide ions, that of
the Cu+ ion in CuL(MeCN)Br compounds, with the bromide ion and the nitrogen atom of acetonitrile molecule.
The CuLX2 complexes (X = Cl, Br) in combination with cocatalysts (methylaluminoxane and triisobutylalu-
minium) exhibit catalytic activity in ethylene polymerization.
DOI: 10.1134/S1070328406030067
A search for and study of new catalytic systems that the transition 3d metals that can be used as catalysts in
can be used in the target synthesis of polymers with the olefin polymerization reactions is still of interest today.
required properties make an urgent task for researchers The authors of [11] reported lately the catalytic activity
[1–4]. Recently, a series of new Fe, Co, Ni, and V com- of the Fe(II) and Co(II) complexes with 2,6-di(pyr-
plexes with the nitrogen-containing organic ligands azole-1-yl)- and 2,6-di(pyrazole-1-ylmethyl)pyridines
were used in combination with cocatalysts (methylalu- in ethylene polymerization in the presence of MAO.
minoxane (MAO) or trialkylaluminium compounds) as Also, the first Cu catalysts of ethylene polymerization
efficient catalysts in ethylene polymerization [5–10]. were reported (the CuCl2 complexes with bidentate
Nevertheless, the development of novel complexes of α-diamine [12] and bis(benzimidazole) [13] ligands).
R
R
R
R
N
N
X
N
N
[ ]
N
N
[ ]
N
N
n
n
n
n
Cu
N
N
Cl
Cl
Cu
M
R
R
Cl
Cl
R
R
Cl Cl
R = H, Me; M = Co, Fe;
n = 0, 1 [11]
R = Ph, iso-Pr [12]
R = alkyl; X = C(OMe)Me,
CEt2, 2,2'-C6H4–C6H4 [13]
The structural aspects of the Cu(I) and Cu(II) com- ing heterocycles with several N atoms and the study of
plexes with the nitrogen-containing ligands, which are their structures and catalytic activity in reactions of ole-
usually used in the radical atom-transfer polymeriza- fin polymerization are of unquestionable interest.
tion are discussed in [14].
The aim of this work was to synthesize the Cu(II)
In this connection, the synthesis of new Cu com- and Cu(I) complexes with a new nitrogen-containing
plexes with the nitrogen-containing ligands incorporat- heterocyclic ligand, namely, 2-(3,5-diphenyl-1H-pyr-
199

200
BUSHUEV et al.
azole-1-yl)-4,6-diiphenylpyrimidine (L) and to study from their solutions in a mixture of CHCl3–MeCN (2 : 1).
their structures and catalytic activity of the Cu(II) com-
pounds in the ethylene polymerization reaction.
Single crystals of I (colored red-orange) and of II (col-
ored dark brown) were formed over a day.
Synthesis of CuL(MeCN)Br (III). Complex II was
dissolved in a mixture of CHCl3–MeCN (2 : 1) on heat-
ing. The solution was cooled, poured in a weighing bot-
tle, and closed. In several hours, dark brown crystals
precipitated from the solution, which were similar in
color to crystals II. In 2–3 days, the dark brown color
of the crystals in the solution changed to red-orange
color and the crystals consolidated. They were used in
X-ray diffraction analysis and their composition was
identified as CuL(MeCN)Br.
The content of Cu in complexes I and II was deter-
mined by complexometric titration after the samples
were decomposed in a mixture of concentrate H2SO4
and HNO3; the analysis for C, H, and N was performed
on a Carlo Erba analyzer using a standard procedure.
The electronic reflection spectra were recorded on a
Unicam 700A spectrophotometer at 340–2300 nm. IR
absorption spectra were recorded on a Scimitar FTS
2000 spectophotometer at 375–4000 cm–1 and on a
BOMEM MB-102 spectrophotometer at 200–400 cm–1;
a high-resolution mass spectrum was taken on a Finni-
gan MAT-8200 spectrometer, electron impact, 70 eV.
X-ray diffraction analysis of I–III was performed
following a standard procedure on automated four-cir-
cle Bruker-Nonius X8Apex diffractometer equipped
with two-coordinate CCD detector at room temperature
(åÓKα radiation, λ = 0.71073 Å, graphite monochro-
mator). The intensities of reflections were measured by
the method of ϕ-scanning of narrow (0.5°) frames to
2θ = 55°. The absorption was corrected empirically
with SADABS program [15]. The structures of I and
III were solved by the direct method and refined by a
full-matrix least-squares method in anisotropic approx-
imation for non-hydrogen atoms with SHELX97 pro-
gram package [16]. Compounds I and II are isostruc-
tural and therefore, a model of I was used in refinement
of structure II. The hydrogen atoms were refined in a
heavy body approximation.
EXPERIMENTAL
The reagents used in the synthesis were high-purity
CuCl2 · 2H2O and CuBr2; MAO Witco Gm1H (Bergha-
men) (a solution in toluene with a total content of Al
1.8 mol/l); triisobutylaluminium (TIBA) (a solution in
heptane, commercial grade).
Synthesis of L. A mixture of 2-hydrazino-4,6-
diphenylpyrimidine (2.6 g, 10 mmol), dibenzoyl-
methane (2.5 g, 11 mmol), 1 ml of acetic acid, and 30 ml
of ethanol was refluxed for 40 h. After cooling to room
temperature, the solvent was decanted, and the precipi-
tate formed was washed two times with ethanol. Then,
a 50% aqueous solution of ethanol was added to the
precipitate and Na2CO3 solution for neutralization. The
precipitate was filtered off, washed with water to a neu-
tral reaction, and then with a cold ethanol. The yield
was 4.2 g (93%); mp = 172–173.5°C. A high-resolution
mass spectrum (direct introduction of a sample to the
ionic source): found m/z 450.1855 [M]+. For C31H22N4
1
anal. calcd.: M = 450.1844. The HNMR spectrum
(200.13 MHz, CDCl3), δ, ppm: 8.20–8.00, 7.91–7.78,
7.60–7.26 (20 H, 4 × Ph), 7.97 (s, 1 H, 5-H
),
pyrimidine
6.89 (s, 1 H, 4-H
).
pyrazole
Synthesis of CuLCl2 (I) and CuLBr2 (II). A hot
solution of L (0.23 g, 0.5 mmol) in 25 ml of ethanol was
added dropwise with stirring to a hot solution of
0.5 mmol of the corresponding Cu(II) salt (0.09 g of
CuCl2 · 2H2O or 0.11 g of CuBr2) in 5–8 ml of ethanol.
A red-orange precipitate of complex I was formed in
2−3 min after mixing of the solutions, whereas a brown
precipitate of complex II was formed in the course of
addition of the L solution to a solution of CuBr2. The
mixtures were stirred for 1.5 h on heating (the final vol-
ume of a solution was 5–7 ml). The precipitates were
filtered off. Then, 2–3 ml of ethanol was added to a
freshly prepared precipitate, and the mixture was
stirred for 0.5 h with slight heating. The precipitate was
filtered off, washed with a small amount of ethanol, and
dried in air. The yield of complex I was 0.27 g (92%);
the yield of complex II was 0.28 g (83%).
The crystallographic parameters and details of data
collection are given in Table 1; the main bond lengths
and selected bond angles for compounds I–III are
listed in Table 2. The molecular packing of complexes
I–III was analyzed with the TOPOS program package
[17, 18] using the Voronoi–Dirichlet approach.
For C31H22N4Cl2Cu (I)
The coordinates of atoms and their thermal parame-
ters are deposited with the Cambridge Structural Data-
base (CSD) and are available from the authors.
Verification of catalytic activity of the Cu(II) com-
plexes in ethylene polymerization reaction was per-
formed in a temperature-controlled vessel (0.2 l in vol-
ume) equipped with a stirrer. MAO and TIBA were
anal. calcd. (%):
Found (%):
C, 63.6; H, 3.8; N, 9.6; Cu, 10.9.
C, 63.2; H, 3.8; N, 9.6; Cu, 10.9.
For C31H22N4Br2Cu (II)
anal. calcd. (%):
Found (%):
C, 55.3; H, 3.3; N, 8.3; Cu, 9.4.
C, 54.9; H, 3.3; N, 8.3; Cu, 9.4.
Single crystals of complexes I and II for X-ray dif- used as cocatalysts. The polymerization conditions are
fraction analysis were obtained by slow crystallization given in Table 3. In the course of the reaction (1 h), the
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 32 No. 3 2006

Cu(II) AND Cu(I) COMPLEXES
201
Table 1. Crystallographic parameters and details of data collection for complexes I–III
Value
Parameter
compound
I
II
III
Formula
M
C31H22Cl2CuN4
584.97
C31H22Br2CuN4
673.89
C33H25BrCuN5
635.03
Crystal system
Space group, Z
a, Å
Monoclinic
P21/n; 4
Monoclinic
P21/n; 4
Monoclinic
P21/n; 4
12.0295(5)
18.8084(7)
12.4585(5)
106.653(2)
2700.58(19)
1.439
12.0869(5)
19.1147(8)
12.5963(5)
106.555(2)
2789.6(2)
1.605
13.6091(6)
13.0721(6)
16.7956(7)
112.3930(10)
2762.6(2)
1.527
b, Å
c, Å
β, deg
V, Å3
ρ(calcd.), g/cm3
µ, mm–1
Crystal size, mm
1.035
3.675
2.269
0.18 × 0.10 × 0.09
23558/6193
0.0537
0.10 × 0.04 × 0.03
24206/6355
0.1080
0.60 × 0.25 × 0.10
28342/6248
0.0304
Number of measured/independent reflections
Rint
Number of observed reflections
R1 for observed reflections
wR2 for all reflections
3709
2559
4634
0.0423
0.0479
0.0355
0.1103
0.1029
0.0944
GOOF for all reflections
0.989
0.889
1.012
constant temperature and pressure were maintained. bromide ion is supposed to be a reductant. Therefore,
the following transformations are carried out:
The obtained polyethylene (PE) powder was dried in
air and weighed.
Ph
Ph
Ph
N
N
N
N
(PhCO)2CH2
NHNH2
N
RESULTS AND DISCUSSION
N
Ph
Pyrazolylpyrimidine L was obtained by cyclic con-
densation of 2-hydrazino-4,6-diphenylpyramidine with
dibenzoylmethane. Complexes I and II were synthe-
sized by reacting Cu(II) salts with L in ethanol solu-
tions on heating. The compounds were taken at a molar
ratio Cu : L = 1 : 1. A slight excess of the Cu(II) salt
with respect to a stoichiometric ratio of 1 : 1 can be
used in the synthesis of the complexes. In order to
obtain a pure phase, the precipitate formed should be
thoroughly washed as recommended above. Com-
plexes I–III are stable in air. Compounds I and II are
soluble in organic solvents (ethanol, MeCN, isopropyl
alcohol, CHCl3, and their mixtures), but are poorly sol-
uble in water. Crystals III precipitated from a solution
Ph
Ph
L
CuX2
Ph
Ph
Ph
Ph
Ph
Ph
N
N
N
N
X = Br
N
N
Cu
N
N
Cu
Ph
Ph
Br
NCMe
X
X
(III)
(I and II, X = Cl, Br)
Mononuclear complexes I–III have molecular
obtained after dissolution of complex II in a mixture of structures. The structures of complexes I and III are
CHCl3–MeëN (2 : 1), after it was allowed to stay for shown in Fig. 1a, 1b, respectively. The coordination
several days. Complex III is a product of reduction of polyhedron of the Cu atoms in I and II is a distorted tet-
compound II and addition of acetonitrile molecule. The rahedron with two coordination sites occupied by the
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 32 No. 3 2006

202
BUSHUEV et al.
Table 2. The main bond lengths (d) in structures I–IV and bond (ω) and torsion (τ) angles in I–III
d, Å
ω, τ, deg
Bond
Angle
III
IV
III
I
II
X = Br
I
II
X = Br
X(1) = Br, [19]
X(1) = Br,
X(2) = N(1L)
X = Cl
X = Cl
X(2) = N(1L) X = Cl
Cu(1)–X(1) 2.2065(8) 2.3165(8) 2.3874(4)
Cu(1)–X(2) 2.1848(8) 2.3399(9) 1.984(2)
2.235 X(1)Cu(1)X(2)
108.40(3) 107.69(3)
123.64(6)
2.188 N(2)Cu(1)X(1)
N(2)Cu(1)N(10)
126.66(7) 103.88(12) 108.59(5)
79.85(8) 80.00(16) 77.24(7)
N(1L)–C(2L)
C(1L)–C(2L)
1.120(3)
1.463(4)
N(10)Cu(1)X(1)
101.51(6) 139.18(12) 116.26(5)
103.36(7) 125.89(12) 114.50(9)
138.42(6) 101.62(12) 107.43(8)
Cu(1)–N(2) 1.986(2) 1.984(4) 2.1106(19) 2.009 X(2)Cu(1)N(2)
Cu(1)–N(10) 2.027(2) 2.015(4) 2.1157(19) 2.000 X(2)Cu(1)N(10)
C(3)–C(4)
N(1)–N(2)
C(3)–N(2)
C(4)–C(5)
1.402(4) 1.389(6) 1.406(3)
1.369(3) 1.367(5) 1.376(3)
1.332(3) 1.338(6) 1.334(3)
1.358(4) 1.368(6) 1.371(3)
1.388
1.384 N(1)C(5)C(51)C(56)
1.379 N(2)C(3)C(31)C(32)
1.382 N(30)C(40)C(41)C(46)
N(10)C(60)C(61)C(66)
1.376 N(30)C(20)N(1)C(5)
1.401
121.9(3) 122.4(6)
133.6(3) 134.5(6)
12.1(4) 10.7(7)
146.1(4) 140.5(5)
–3.96(4) –4.8(8)
131.3(3)
161.3(2)
0.1(3)
C(5)–C(51) 1.478(4) 1.467(6) 1.478(3)
C(5)–N(1) 1.377(3) 1.385(6) 1.381(3)
133.4(3)
–3.5(3)
C(20)–N(1) 1.407(3) 1.406(6) 1.420(3)
C(3)–C(31) 1.467(4) 1.475(7) 1.473(3)
Deviation from the plane
N(10)C(20)N(1)N(2), Å
I
II
III
X = Cl
X = Br
X(1) = Br,
X(2) = N(1L)
C(20)–N(10) 1.345(3) 1.344(6) 1.340(3)
C(20)–N(30) 1.304(3) 1.307(6) 1.320(3)
C(40)–C(50) 1.387(4) 1.398(6) 1.383(3)
C(40)–N(30) 1.352(3) 1.339(6) 1.352(3)
C(50)–C(60) 1.374(4) 1.387(6) 1.381(3)
C(60)–N(10) 1.358(3) 1.356(6) 1.352(3)
1.334 Cu(1)
1.309 X(1)
1.387 X(2)
1.318
0.0856
1.8917
1.2526
0.0501
1.3756
1.9559
0.2639
1.3187
2.4879
1.368
1.356
Table 3. The results of estimation of the catalytic activity of complexes I and II in ethylene polymerization reaction
Experimental conditions
Activity,
Complex
PE yield, g
kg PE/mol Cu h atm
PC H , atm
cocatalyst
T, °C
2
4
CuLCl2 (I)
MAO
TIBA
MAO
TIBA
MAO
10
35
0.70
1.12
0.90
1.15
0.4
35
56
45
58
4.5
CuLBr2 (II)
10
35
Cu(α-diimine)Cl2
4.5
25
–4
*The data of [12] are given for comparison ([Cu] = 2.0 × 10 mol/l).
**The polymerization conditions are: 70 ml of toluene (heptane), [Cu] = 3 × 10 mol/l, the molar ratio Al
–5
: Cu = 500.
cocat
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 32 No. 3 2006

Cu(II) AND Cu(I) COMPLEXES
203
(a)
C(44)
C(54)
C(45)
C(43)
C(55)
C(56)
C(53)
C(52)
C(46)
C(42)
C(41)
C(40)
N(30)
C(20)
C(51)
C(5)
C(4)
N(1)
C(50)
N(10)
C(60)
C(3)
C(61)
N(2)
C(66)
C(65)
C(32)
C(33)
C(31)
Cu(1)
C(62)
C(63)
C(36)
Cl(1)
C(64)
C(34)
C(35)
Cl(2)
(b)
C(45)
C(44)
C(43)
C(54)
C(55)
C(56)
C(46)
C(53)
C(52)
C(42)
C(41)
C(40)
C(51)
N(30)
N(1)
C(5)
C(50)
C(4)
C(20)
N(2)
C(60)
N(10)
C(3)
C(31)
C(32)
C(61)
C(66)
C(65)
Cu(1)
Br(1)
C(36)
N(1L)
C(2L)
C(33)
C(34)
C(62)
C(63)
C(35)
C(64)
C(1L)
Fig. 1. The structure of (a) complex I and (b) complex III (ellipsoids of a 50% probability). The numbering schemes in I and II coincide.
N2 atom of pyrazole and N1 atom of pyrimidine rings of 0.264 Å) from the N2C2 plane (Table 2). The nitrogen-
containing heterocycles are also almost planar with the
maximum deviation of the atoms from their plane in I,
II, and III being 0.031, 0.026, and 0.011 Å, respec-
tively.
a bidentate-cyclic ligand L. The remaining two vertices
of a tetrahedron in molecules I and II are occupied by
the halogen atoms; in III, by the Br atom and the N
atom of the coordinated MeCN molecule. As a result of
the ligand coordination, the CuN2C2 chelate cycle is
closed. In compounds I and II, this cycle is almost pla-
The molecular structure of complexes I and II is
similar to that of compound CuCl2 with symmetric
nar, while in III, the Cu atom noticeably deviates (by α-diimine, which is catalytically active [11]. Note that
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 32 No. 3 2006

204
BUSHUEV et al.
(‡)
(b)
y
x
Fig. 2. (a) Molecular pair and (b) molecular packing along the z axis in structures I and II.
compounds I and II have substantially different lengths with methyl and methoxy groups instead of phenyl sub-
of the Cu–Hal bond for two halogen atoms and of the
Cu–N bond for the donor N atoms of different hetero-
cycles (Table 2). At the same time, the CuCl2 complex
with α-diimine, where both N atoms belong to identical
fragments, does not show this difference.
stituents in pyrazole and pyrimidine rings. The bond
lengths in pyrazole rings of compounds I and II are
almost identical. The analysis of the C–C and C–N dis-
tances in complexes I–III shows that the change in the
oxidation state of copper from +2 to +1 results in a
higher delocalization of bonds in pyrimidine ring. It is
worthwhile noting that elongation of the C3–N2 and
C4−C5 bonds in complex IV as compared to complexes
I and II is caused by a stronger positive mesomeric
electronic effect of the 5-MeO group as compared to
that of 5-Ph group on the electron density redistribution
The lengths of the Cu–N and Cu–Hal bonds gradu-
ally decrease on going from two Cu(II) complexes
(I and II) to the Cu(I) complex (III). The analysis of
data from CSD showed that compound III is the first
Cu complex with oxidation state +1 and pyrazolylpyri-
midine ligand. The nearest analog of complexes I and
II is dichloro(4-methoxy-2-(5-methoxy-3-methylpyra-
zole-1-yl)-6-methylpyrimidine)copper (II) (IV) [19] in a pyrazole ring.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 32 No. 3 2006

Cu(II) AND Cu(I) COMPLEXES
205
(‡)
(b)
y
z
Fig. 3. (a) The dimeric molecular pair formed by stacking interaction and (b) packing along the x axis in structure III.
Crystals I and II have similar molecular packing pyrimidine ring of another molecule, which prevents
(Fig. 2a). Each CuLX2 molecule (X = Cl, Br) is sur- stacking interactions. The remaining molecules in sur-
rounded by 14 neighbors (molecular C.N. 14). It was rounding have lower contact area. Therefore, one can
previously shown [20, 21] that the nearest surrounding formally consider the molecular packing as a packing
of a molecule in crystal can be efficiently analyzed of molecular pairs, which, despite nonuniform sur-
using the frontier surfaces, whose area and solid angle rounding of every separate molecule, realize almost
determine the surface area of a contact between the perfectly uniform packing of a body-centered cubic lat-
tice. In general, the molecular packing in crystals I and
II can be considered to be mainly due to van der Waals
interactions between molecules.
neighboring molecules and hence, the relative energy
of their interaction.
The molecules of structures I and II form cen-
trosymmetric pairs (Fig. 2a), for which the frontier sur-
face area is maximum and is equal to about 17% and
14%, respectively, of the total surface of a central mol-
Crystal III has different molecular packing. Every
molecule in this crystal is surrounded by 13 close and 2
remote neighbors. In this case, one of the surrounding
ecule. The molecules are arranged in such a way that molecules forms with a central molecule a frontier sur-
the halogen atom of one molecule is directed toward face equal to ~22% of the total surface of the molecule
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206
BUSHUEV et al.
Table 4. The main frequencies in IR spectra (cm–1) of the L ligand and complexes I–III
Compound
ν(Ph)
(ν + δ)ring
ν(CH)
ν(Cu–N)
ν(Cu–X)
L
1602
1607
1607
1607
1587, 1574, 1560, 1522
1594, 1577, 1557, 1527
1593, 1577, 1557, 1526
1592, 1577, 1554, 1526
3062
3059
3059
CuLCl2 (I)
280 sh
304, 329
230, 246
CuLBr2 (II)
255, 264
CuL(MeCN)Br(III)
(Fig. 3a), whereas the contribution of any other sur- proved to be efficient cocatalyst for complexes I and II
rounding molecule is less than 13%. As in the case of (Table 3, experiments 2 and 4).
crystals I and II, in crystal III, a pair of nearest mole-
Thus, it was shown that the Cu(II) halide complexes
cules is bonded through the symmetry center. However,
with a ligand containing pyrazole and pyrimidine rings
the molecules of a dimer ensemble are noticeably
are potential catalysts that can be used in the ethylene
drawn together, and the π-systems of a pyrimidine ring
and of one of the phenyl rings participate in the stack-
ing interactions (the distance between the planes of
these rings is ~3.4 Å). As a whole, the molecular pack-
ing (Fig. 3b), which can be treated as a packing of
dimers (where the molecules are bonded to one another
stronger than to the neighboring molecules), is in fact a
significantly distorted face-centered cubic lattice.
Table 4 contains IR spectroscopic data for ligand L
and complexes I–III. The positions of the stretching-
deformation vibrations of heterocyclic rings in IR spec-
tra of complexes I–III are changed as compared to the
spectrum of L, which, in accordance with X-ray dif-
fraction data, suggest coordination of the L molecule.
The band due to vibrations of the phenyl group in the
spectra of the complexes shifts toward the high-fre-
quency region. The low-frequency regions of the spec-
tra of complexes I and II each contain two bands due to
the stretching vibrations of the bonds Cu–Cl in I and
Cu–Br in II, for which ν(Cu–Br)/ν(Cu–Cl) = 0.74–
0.77. The IR spectra of complexes I and II exhibit the
bands due to the stretching vibrations of the Cu–N
bonds. In the spectrum of compound I, the bands due to
vibrations ν(Cu–N) are overlapped by the intense
absorption ν(Cu–Cl).
polymerization process. Therefore, further search for
new catalysts, i.e., the transition 3d-metal complexes
with the nitrogen-containing heterocyclic ligands and
several N atoms in the cycles, is promising.
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