Changes in the conformational parameters of 1-allylbenzotriazole in a mixed halide π-complex [CuCl0.85Br0.15(C6H 4N3CH2CH=CH2)] under the action of bromine atoms

Article abstract of DOI:10.1007/s10947-006-0026-0

Single crystals of [CuCl_0.85Br_0.15(C ₆H₄N₃CH₂=CH₂)] (I) were obtained by alternating current electrochemical synthesis; their X-ray structural investigation has been carried out (DARCh automatic diffractometer, MoK _α radiation, θ/2θ scanning; 1460 reflections with F ≥ 4σ(F), R = 0.0517). The crystals are monoclinic, their space group is P2₁/c, a = 7.292(3) A, b = 17.947(8) A, c = 7.398(4) A, β = 93.56(4)°, V = 966(1) A³, Z = 4). Complex I is close in structure to the previously investigated compound [CuCl(C₆H₄N₃CH₂=CH₂)] (II). In both structures, the trigonal-pyramidal surroundings of the copper atom include two halide atoms (one is apical), a nitrogen atom, and a C=C group. The Cu₂X₂ dimers are associated into {[Cu₂X ₂(C₆H₅N₃CH₂=CH ₂)]}_n layers due to the bridging function of the 1-allylbenzotriazole molecule. In spite of the similar coordination polyhedra of the metal atoms and identical bridging function of the ligand molecule in I and II, the differences in the conformation parameters of the allyl group π-coordinated by the copper(I) atom (trans-like in I and cis-like in II) caused by the presence of bromine atoms in the coordination sphere predetermine different structures of the organometallic [Cu₂X₂(C ₆H₅N₃CH₂=CH₂)] ₄ tetramer subunits in the layers and, as a consequence, formation of different crystal structures.

Full text of DOI:10.1007/s10947-006-0026-0

Journal of Structural Chemistry, Vol. 46, No. 1, pp. 172-176, 2005
Original Russian Text Copyright © 2005 by E. A. Goreshnik, B. M. Mykhalichko, and V. N. Davydov
CHANGES IN THE CONFORMATIONAL PARAMETERS
OF 1-ALLYLBENZOTRIAZOLE IN A MIXED HALIDE
S-COMPLEX [CuCl0.85Br0.15(C
6
H
4
N
3
ɋɇ
2
2
ɋɇ=ɋɇ )] UNDER
THE ACTION OF BROMINE ATOMS
2
E. A. Goreshnik, B. M. Mykhalichko,
1
UDC 548.736:546.561
1
and V. N. Davydov
Single crystals of [CuCl0.85Br0.15(C H N ɋɇ ɋɇ=ɋɇ )] (I) were obtained by alternating current
6
4
3
2
2
electrochemical synthesis; their X-ray structural investigation has been carried out (DARCh automatic
diffractometer, ɆɨK radiation, T/2T scanning; 1460 reflections with F t 4V(F ), R = 0.0517). The crystals
D
are monoclinic, their space group is Ɋ2 /ɫ, ɚ = 7.292(3) Å, b = 17.947(8) Å, c = 7.398(4) Å, E = 93.56(4)q,
1
3
V = 966(1) Å , Z = 4). Complex I is close in structure to the previously investigated compound
[
CuCl(C H N ɋɇ ɋɇ=ɋɇ )] (II). In both structures, the trigonal-pyramidal surroundings of the copper
6
4
3
2
2
atom include two halide atoms (one is apical), a nitrogen atom, and a C=C group. The Cu X dimers are
2
2
associated into {[Cu ɏ (C H N CH ɋɇ=ɋɇ )]} layers due to the bridging function of the 1-allylben-
2
2
6
5
3
2
2
n
zotriazole molecule. In spite of the similar coordination polyhedra of the metal atoms and identical bridging
function of the ligand molecule in I and II, the differences in the conformation parameters of the allyl group
S-coordinated by the copper(I) atom (trans-like in I and cis-like in II) caused by the presence of bromine
atoms in the coordination sphere predetermine different structures of the organometallic
[
Cu
2
ɏ
2
(C
6
H
5
N
3
CH
2 2 4
ɋɇ=ɋɇ )] tetramer subunits in the layers and, as a consequence, formation of different
crystal structures.
Keywords: S-complex, copper(I) halide, 1-allylbenzotriazole, synthesis, structure, geometry of the
coordination center.
Copper(I) chloride and bromide frequently form nonisostructural S-complexes [1-3]. The difference between the
atomic radii of chlorine and bromine generally leads to the formation of different surroundings of the metal atoms and to the
formation of nonisostructural compounds. As a rule, mixed chloride-bromide compounds are isostructural with the bromide
analogs, although in some cases isomorphic chloride and chloride-bromide complexes are formed [4].
This paper reports on the results of an X-ray structural investigation of a new mixed halide S-complex of copper(I)
having the composition [CuCl0.85Br0.15(C
6
H
4
N
3
ɋɇ
2 2
ɋɇ=ɋɇ )] (I) and compares the structure with that of the previously
investigated compound [CuCl(C H N ɋɇ ɋɇ=ɋɇ )] (II) [5].
6
4
3
2
2
Experimental. Synthesis of 1-allylbenzotriazole. The ligand was synthesized (according to a procedure similar to
that described in [6]) from the equimolar amounts of benzotriazole (Reachim), freshly distilled allyl bromide, and NaHCO in
3
1
2
I. Franko Lvov National University, Ukraine; mykhalitchko@franko.lviv.ua. George-August University,
Göttingen, Germany. Translated from Zhurnal Strukturnoi Khimii, Vol. 46, No. 1, pp. 174-178, January-February, 2005.
Original article submitted February 10, 2004.
1
72
0022-4766/05/4601-0172 © 2005 Springer Science+Business Media, Inc.

TABLE 1. Crystal Data and Parameters for I
Characteristics
I
Empirical formula
Color, habit
Space group
a, b, c, Å
9 9 3
CuCl0.85Br0.15C H N
Colorless monoclinic prisms
P2 /ɫ
1
7.292(3), 17.947(8), 7.398(4)
E, deg
V, Å
93.56(4)
3
966(1)
Z
4
1.822(3)/1.85(3)
32.1
3
U
calc /Umsd, g/cm
P(MoK ), cm
D
–
1
Crystal dimensions, mm
0.3u0.3u0.1
1460
Number of reflections with |F t 4V(F )|*
2
-
max, deg
55
2
2 –1
Weight scheme (w)
R, R
[V(F) + 0.003F ]
0.0517, 0.0581
w
*A correction for Lorentz and polarization factors is applied.
ethanol. The mixture was boiled for 22 h with a reflux condenser and then filtered. A concentrated solution of 1-
allylbenzotriazole containing a small amount of NaBr as an admixture (the solubility of NaBr in ethanol is 2.27%) was used
to synthesize compound I.
Synthesis of [CuCl0.85Br0.15(C H N ɋɇ ɋɇ=ɋɇ )] crystals (I). High-quality single crystals of compound I were
6
4
3
2
2
obtained by alternating current electrochemical synthesis [7] in ethanol; the solution contained CuCl
-allylbenzotriazole (2.0 mmol) with a small admixture of NaBr; copper electrodes were used (alternating current 50 Hz,
voltage 0.4 V); synthesis was performed according to the scheme
2 2
˜2H O (1.0 mmol) and
1
II
0
1
0Cu Cl
2
˜2H
2
O + 10Cu + 20C
6
H
4
N
3
ɋɇ
2
ɋɇ=ɋɇ
2
+ 3NaBr = 20[CuCl0.85Br0.15(C
6
H
4
N
3
ɋɇ
2
2
ɋɇ=ɋɇ )] + 3NaCl.
After 27 days, colorless lamellar crystals of compound I formed on the electrodes. The density of the crystals
3
measured by the flotation method in a mixture of chloroform with bromoform was 1.85 g/cm .
X-ray structural analysis of crystals I. The crystals were preliminarily investigated by the photo method. To solve
the structure, the integrated intensities of reflections with I t 2V(I ) obtained with a DARCh single crystal diffractometer
(
MoK radiation, T/2T scan mode) were used. The unit cell parameters were refined by the least squares method with respect
D
to setup angles of 24 reflections in the range 25q d 2T d 30q. Crystal data and parameters for single crystal I are listed in Table 1.
The structure of compound I was solved by direct methods using the CSD program package [8]. After localization of
all non-hydrogen atoms and structure refinement in the isotropic approximation, a correction for absorption was applied using
the DIFABS program. The positions of hydrogen atoms were determined with difference Fourier syntheses. The final
refinement of the structure was carried out in the anisotropic version (H atoms in the isotropic one). The atomic coordinates
and thermal parameters are listed in Table 2; the interatomic distances and bond angles are shown in Table 3. The figures
were prepared using the DIAMOND program [9].
Results and discussion. In both structures, the copper and halogen atoms form Cu X centrosymmetrical dimers
2
2
(
Fig. 1). The Cu–X distances in I are somewhat increased and equal 2.312(2) Å and 2.831(2) Å versus 2.283(2) Å and
.673(2) Å in II; these distances are in good agreement with partial bromide-chloride substitution in I. The nitrogen atom of
2
N
one 1-allylbenzotriazole molecule and the C=C group of the other complete the S,V surroundings of copper(I) to a trigonal
pyramid.
1
73

TABLE 2. Atomic Coordinates and Thermal Parameters* for I
Atom
x
y
z
B
iso
Atom
x
y
z
B
iso
Cu
0.3759(1) 0.08060(5) 0.9136(1)
0.3109(2) 0.00560(8) 0.1556(2)
0.5119(7) 0.2935(3) 0.0559(7)
0.4062(7) 0.2388(3) 0.9823(7)
0.4878(7) 0.1749(3) 0.0145(7)
0.2258(9) 0.0441(4) 0.6817(9)
0.2900(8) 0.1132(4) 0.6512(8)
0.4489(9) 0.3706(4) 0.0384(9)
0.7927(9) 0.1394(4) 0.1699(8)
0.9416(9) 0.1716(4) 0.2595(9)
0.9561(9) 0.2478(4) 0.2929(9)
0.8196(9) 0.2976(4) 0.2310(9)
2.86(2)
3.39(4)
2.1(1)
2.4(1)
2.4(1)
2.9(2)
2.4(2)
2.7(2)
2.8(2)
3.6(2)
3.2(2)
2.7(2)
C(8)
C(9)
H(1)
H(2)
H(3)
H(4)
H(5)
H(6)
H(7)
H(8)
H(9)
0.6683(8) 0.2641(3) 0.1384(7)
0.6527(8) 0.1885(3) 0.1119(8)
1.9(1)
2.1(1)
3(1)
3(1)
2(1)
1(1)
1(1)
3(1)
5(2)
4(2)
3(1)
X**
N(1)
N(2)
N(3)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
0.297(8)
0.134(9)
0.239(9)
0.564(7)
0.410(7)
0.792(9)
0.032(9)
0.042(9)
0.840(9)
0.005(3)
0.035(4)
0.150(3)
0.401(3)
0.382(3)
0.089(4)
0.139(5)
0.275(4)
0.355(4)
0.624(7)
0.728(9)
0.689(8)
0.076(6)
0.923(7)
0.142(8)
0.271(9)
0.347(9)
0.255(9)
1
*
B
eq
=
B a a (a a ), for ɇ — ȼiso.
¦
ij
i
j
i
j
3
ij
*
*G = 0.846(6)Cl + 0.154(6)Br.
TABLE 3. Bond Lengths d (Å) and Angles Z (deg) for I and II
d
d
d
Bond
Cu–X
Bond
Bond
I
II
I
II
I
II
2.312(2)
2.831(2)
2.003(6)
2.082(8)
2.086(7)
1.972(7)
2.283(2)
2.673(2)
2.010(5)
2.067(8)
2.092(7)
1.965(7)
C(1)=C(2)
C(2)–C(3)
N(1)–C(3)
N(1)–C(8)
N(1)–N(2)
N(2)–N(3)
1.348(9)
1.497(9)
1.462(9)
1.366(8)
1.343(8)
1.306(8)
1.363(9) N(3)–C(9)
1.385(8)
1.366(9)
1.39(1)
1.367(8)
1.367(9)
1.400(9)
1.357(9)
1.419(9)
1.388(9)
…
Cu Xc
1.473(9)
1.477(9)
1.341(8)
1.335(8)
1.315(8)
C(4)–C(5)
C(5)–C(6)
C(6)–C(7)
C(7)–C(8)
C(8)–C(9)
Cu–N(3)
Cu–C(1)
Cu–C(2)
Cu–m*
1.39(1)
1.398(9)
1.375(9)
Z
Z
Angle
Angle
I
II
I
II
XCuXc
XCum
91.6(2)
95.7(1)
N(1)N(2)N(3)
N(2)N(3)ɋ(9)
N(2)N(1)C(8)
N(1)C(8)C(9)
N(3)C(9)C(8)
N(3)C(9)C(4)
C(9)C(4)C(5)
C(4)C(5)C(6)
ɋ(5)C(6)C(7)
ɋ(6)C(7)C(8)
C(7)C(8)N(1)
108.9(6)
107.8(6)
127.5(3)
97.6(3)
120.8(1)
103.3(1)
111.7(2)
94.6(2)
108.2(6)
109.9(6)
104.9(6)
108.0(6)
130.1(7)
115.2(7)
123.5(7)
121.8(7)
114.2(7)
131.6(7)
108.7(6)
111.1(6)
104.8(6)
107.4(6)
132.8(7)
118.5(7)
119.9(7)
124.7(7)
114.0(7)
132.0(7)
XcCum
XCuN(3)
XcCuN(3)
mCuN(3)
C(1)CuC(2)
107.6(3)
102.4(3)
120.3(4)
37.7(3)
121.7(2)
38.2(3)
ɋ(1)ɋ(2)ɋ(3)
ɋ(2)ɋ(3)N(1)
ɋ(3)N(1)ɋ(8)
ɋ(3)N(1)N(2)
124.1(7)
112.6(6)
130.9(7)
119.2(6)
124.4(7)
112.0(6)
128.5(6)
120.3(6)
m is the middle of the C=C bond.
1
74

Fig. 1. Fragment of the crystal structure of [CuCl0.85Br0.15(C
6
H
4
N
3
ɋɇ
2 2
ɋɇ=ɋɇ )].
Fig. 2. Structure of the {[Cu
2
ɏ
2
(C
6
H
5
N
3
CH
2
ɋɇ=ɋɇ
2
)]} layer in I (a) and II (b).
n
1
75

In structure I, the Cu–m distance is 1.972(7) Å, the coordinated C=C bond length is increased to 1.348(9) Å, and the
C–Cu–C angle is 37.7(3)q. These values point to a rather efficient Cu(I)–(C=C) interaction. The C–Cu–C angle in ȱ is
somewhat smaller than that in II (38.2(3)q), which is the result of the presence of bromine in the coordination sphere of
copper and, as a consequence, of partially decreased efficiency of Cu(I)–(C=C) interaction.
The bridging function of the 1-allylbenzotriazole molecule results in the formation of organometallic layers in both
compounds (Fig. 2). However, partial substitution of chlorine atoms (in ȱȱ) by bromine atoms (in ȱ) in the coordination
surroundings of the central atom changes the conformation parameters of the allyl group of the 1-allylbenzotriazole molecule,
which has a trans-type conformation in ȱ but almost cis-type conformation in ȱȱ. This is also depicted in the shape of layers
formed in the structures of the complexes under consideration. For example, in both structures, an elementary subunit
[
Cu X (C H N Cɇ ɋɇ=ɋH )] can be distinguished within the sublayer; it differs in shape between I and II. In the
2
2
6
4
3
2
2
4
elementary subunits, four ligand molecules are linked by four Cu ɏ dimer bridges into a closed cycle. Within one cycle, the
2
2
Cu ɏ dimer bridges lie in pairs facing one another; the distances between the dimer bridges in one pair are much shorter than
2
2
those in another (the corresponding “dimer–dimer” distances are 7.4 Å and 15.2 Å for I and 4.4 Å and 16.3 Å for II).
These differences in the structure of the sub-units including ligand molecules have a strong effect on the
conformation of 1-allylbenzotriazole. The torsion angles in I (Cu–C(2)–C(3)–N(1) 87.4q, C(1)–C(2)–C(3)–N(1) 168.2q and
N(2)–N(1)–C(3)–C(2) 70.9q) are notably different from the corresponding values (166.7q, 87.8q, and 103.1q) in II. Thus the
ligand in I acquires a more stretched conformation in comparison with the folded conformation in II. In structure I, the
alternate Cu
with one copper atom are parallel at a distance of a3.7 Å. At the same time, all inorganic dimers in II are almost parallel to
each other; the nearest two ligand molecules are bound with one Cu Cl fragment and have a “head-to-head” arrangement, the
2
ɏ
2
fragments are tilted to each other at an angle of 70q, two nearest 1-allylbenzotriazole molecules connected
2
2
distance between the planes of the benzotriazole rings (~5 Å) depending on the size of the inorganic fragment.
Thus in spite of the same type of coordination polyhedron for the metal atoms and the identical bridging function of
the ligand molecule in both compounds, compounds I and II are nonisostructural. In our opinion, the presence of a small
amount of bromine atoms in structure ȱ decreases the packing density, which makes the stacking of aromatic rings
predominant in the formation of the structure; in particular, this results in changes in the ligand conformation, forming a
structure generally different from that of II.
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1
2
3
4
5
6
7
8
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1
76