Bis[bis(3-phenylpyrazol-1-yl)(pyrazol-1-yl)methane]copper(II) bis(perchlorate) acetonitrile disolvate

Article abstract of DOI:10.1107/S0108270105041661

The title copper(II) complex, [Cu(C₂₂H₁₈N ₆)₂](ClO₄)₂·2C ₂H₃N, comprises two neutral substituted tris(pyrazol-1-yl)methane ligands bonded to a central Cu^II ion, which is positioned on a crystallographic inversion center. Six Cu - N bonds are arranged in a distorted octahedral fashion. The unsubstituted pyrazole rings on each ligand are oriented trans with respect to each other, interdigitated with the two 3-phenylpyrazole rings of the other ligand.

Full text of DOI:10.1107/S0108270105041661

metal-organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
of copper(II) perchlorate in acetonitrile/acetone, the green
complex [CuL2](ClO4)2Á2C2H3N, (I) (Fig. 1), crystallizes.
There are two possible isomers of the complex, which differ
in the position of the unsubstituted pyrazole moieties relative
to each other in the complex. A centrosymmetric complex
with two unsubstituted pyrazole moieties opposite each other
clearly has less steric hindrance than an asymmetric isomer
with juxtaposed unsubstituted groups.
ISSN 0108-2701
Bis[bis(3-phenylpyrazol-1-yl)(pyrazol-
1-yl)methane]copper(II) bis(perchlor-
ate) acetonitrile disolvate
M. Scott Goodman,a Margaret A. Goodman,a Andrey Y.
Kovalevsky,b Alexander Y. Nazarenkoa* and Donald
Popea
aChemistry Department, State University of New York, College at Buffalo, 1300
Elmwood Ave, Buffalo, NY 14222-1095, USA, and bDepartment of Chemistry,
State University of New York, University at Buffalo, Buffalo, NY 14260, USA
Correspondence e-mail: nazareay@buffalostate.edu
Received 16 November 2005
Accepted 13 December 2005
Online 14 January 2006
The title copper(II) complex, [Cu(C22H18N6)2](ClO4)2Á-
2C2H3N, comprises two neutral substituted tris(pyrazol-1-
yl)methane ligands bonded to a central CuII ion, which is
positioned on a crystallographic inversion center. Six CuÐN
bonds are arranged in a distorted octahedral fashion. The
unsubstituted pyrazole rings on each ligand are oriented
trans with respect to each other, interdigitated with the two
3-phenylpyrazole rings of the other ligand.
Previously reported structures of symmetric tris(pyrazol-
yl)methane±copper(II) complexes demonstrate a typically
Jahn±Teller-distorted geometry, with two short CÐN distances
Ê
Ê
of approximately 2.0 A and one long distance of 2.35 A. In the
title compound, the additional effect of the unsubstituted
pyrazole group results in further variety of the bond distances
Ê
(Table 1), one becoming signi®cantly shorter [1.9433 (13) A]
Comment
The transition metal complexes of tris(pyrazolyl)methanes
(Tpms) have been known for over 30 years (Tro®menko, 1970;
Reger, 1999). Several structural studies on 2:1 Tpm±
copper(II) complexes have been undertaken. These include
the CuII complexes with tris(3,5-dimethylpyrazolyl)methane
(Reger et al., 2002; Martini et al., 2002), tris(3,4,5-trimethyl-
pyrazolyl)methane (Martini et al., 2002), tris(4-bromo-3,5-
dimethylpyrazolyl)methane (Cvetkovic et al., 2001) and tris-
(pyrazolyl)methane (Astley et al., 1993). With CuII, these
tripodal N-donor ligands typically form 2:1 octahedral
complexes, showing Jahn±Teller distortion typical of d9 metal
complexes. Other stoichiometries are also possible (Cvetkovic
et al., 2001; Moubaraki et al., 2002; Van Langenberg et al.,
2002).
A common feature of all the tris(pyrazolyl)methane ligands
studied thus far is that they each have C3v symmetry, viz. they
are all constructed using three identical pyrazole moieties. In
this report, for the ®rst time, we present the structure of a
metal complex that incorporates a tris(pyrazolyl)methane
ligand constructed from two different pyrazoles (see scheme).
Ligand L, namely bis(3-phenylpyrazolyl)(pyrazolyl)methane,
incorporates two 3-phenylpyrazole moieties and a single
unsubstituted pyrazole ring. Upon mixing with 0.5 equivalents
Figure 1
A view of the molecule of [CuL2](ClO4)2Á2C2H3N, showing the atom-
labeling scheme. Displacement ellipsoids are drawn at the 50%
probability level. H atoms have been omitted.
m30 # 2006 International Union of Crystallography
DOI: 10.1107/S0108270105041661
Acta Cryst. (2006). C62, m30±m32

metal-organic compounds
dichloromethane/ethyl acetate mixture. The polarity was slowly
increased to 3:1 dichloromethane/ethyl acetate. The order of elution
is based on the number of 3-phenylpyrazoles incorporated into the
Tpm. Trisubstituted tris(3-phenylpyrazolyl)methane elutes ®rst,
followed by disubstituted L and, ®nally, monosubstituted (3-phenyl-
1
pyrazolyl)bis(pyrazolyl)methane. Ligand L: H NMR: ꢀ 6.37 (t, J =
4.3 Hz, 1H), 6.67 (d, J = 2.6 Hz, 2H), 7.32 (t, J = 7.1 Hz, 2H), 7.39 (t, J =
6.6 Hz, 4H), 7.66 (d, J = 2.6 Hz, 3H), 7.68 (d, J = 1.3 Hz, 1H), 7.81 (d,
J = 6.9 Hz, 4H), 8.48 (s, 1H); 13C NMR: ꢀ 83.7, 104.6, 107.2, 126.0,
128.4, 128.6, 129.6, 130.8, 132.5, 141.8, 153.6; EIMS m/z: 366 (M+), 223.
EI±HRMS: calculated for C22H18N6: 366.1593; found: 366.1590. For
the preparation of the CuII complex, a solution of Cu(ClO4)2Á6H2O
(37 mg, 0.10 mmol) in acetonitrile (10 ml) was mixed with L (73 mg,
0.20 mmol) dissolved in acetone (10 ml). Upon standing, dark-green
crystals suitable for X-ray diffraction were deposited on the sides of
the tube.
Figure 2
The packing of [CuL2](ClO4)2Á2C2H3N, viewed along the c axis.
Ê
and another much longer [2.1878 (14) A]. The bite angles
Crystal data
between unsubstituted pyrazole atom N32 and phenylpyrazole
atoms N12 and N22 are only slightly smaller than 90ꢀ (Table 1),
while the angle between the two phenylpyrazole N atoms is
visibly less [79.19 (5)ꢀ]. Once again, it appears that steric
hindrance is playing a dominant role.
The central CuII atom along with axial atom C1 and each
corresponding pair of pyrazole groups form three planes. In
agreement with planarity of the copper±pyrazole complex, the
torsion angles around the NÐN bond are small, being almost
zero for the unsubstituted pyrazole moiety (Table 1). The
mean deviation of atoms from the plane containing the
3
[Cu(C22H18N6)2](ClO4)2Á2C2H3N
Dx = 1.464 Mg m
Mo Kꢂ radiation
Cell parameters from 20256
re¯ections
Mr = 1077.40
Monoclinic, P21=c
Ê
Ê
a = 11.3652 (2) A
b = 16.3372 (3) A
ꢃ = 3±29ꢀ
ꢄ = 0.63 mm
T = 90 (2) K
1
Ê
c = 14.0065 (3) A
ꢁ = 109.949 (1)ꢀ
V = 2444.62 (8) A
Z = 2
3
Ê
Prism, green
0.40 Â 0.25 Â 0.19 mm
Data collection
Bruker SMART CCD area-detector
diffractometer
' and ! scans
5606 independent re¯ections
4998 re¯ections with I > 2ꢅ(I)
Rint = 0.030
Ê
unsubstituted pyrazole ring is less than 0.01 A, while for the
Absorption correction: empirical
(using intensity measurements)
(SADABS; Sheldrick, 1996)
Tmin = 0.79, Tmax = 0.88
34957 measured re¯ections
ꢃmax = 27.5ꢀ
Ê
other two planes these deviations are visibly larger (0.04 A).
h = 14 ! 14
These three planes intercept each other very close to the C1Ð
Cu axis, thus forming the main motif of a complex cation. The
same shape of the complex can be achieved via molecular
simulations using semi-empirical calculations in the PM3
approximation. The angles between the planes are 73.5, 53.0
and 53.5ꢀ, with the largest corresponding to that between the
two substituted pyrazole groups.
The cationic complexes are positioned with the copper ion
on a crystallographic inversion center. The metal ion is
surrounded by a hydrophobic `coat', thus leaving no possibi-
lity for any additional interactions. The perchlorate ions and
solvent molecules ®ll voids in the crystal structure, which
shows no hydrogen bonds or short contacts (Fig. 2).
k = 21 ! 21
l = 18 ! 18
Re®nement
Re®nement on F2
R[F2 > 2ꢅ(F2)] = 0.032
wR(F2) = 0.088
S = 1.05
5606 re¯ections
w = 1/[ꢅ2(F2o) + (0.0395P)2
+ 2.3608P]
where P = (F2o + 2Fc2)/3
(Á/ꢅ)max < 0.001
3
Ê
Áꢆmax = 0.92 e A
3
Ê
0.37 e A
352 parameters
H-atom parameters constrained
Áꢆmin
=
Extinction correction: SHELXL97
Extinction coef®cient: 0.0099 (5)
Table 1
Selected geometric parameters (A, ).
ꢀ
Ê
CuÐN32
CuÐN12
CuÐN22
C1ÐN21
C1ÐN31
C1ÐN11
N11ÐC15
N11ÐN12
N12ÐC13
C13ÐC14
C14ÐC15
1.9433 (13)
2.1878 (14)
2.3500 (14)
1.441 (2)
1.4432 (19)
1.445 (2)
1.347 (2)
1.3689 (18)
1.340 (2)
1.403 (3)
N21ÐC25
N21ÐN22
N22ÐC23
C23ÐC24
C24ÐC25
N31ÐC35
N31ÐN32
N32ÐC33
C33ÐC34
C34ÐC35
1.356 (2)
1.3635 (18)
1.339 (2)
1.408 (2)
1.365 (2)
1.351 (2)
1.3543 (18)
1.330 (2)
1.394 (2)
1.369 (2)
Experimental
Ligand L was prepared using a method similar to that previously
described by Goodman & Bateman (2001). Tris(pyrazolyl)methane
(2.00 g, 9.3 mmol) and 3-phenylpyrazole (4.00 g, 27.7 mmol) were
dissolved in dry toluene (250 ml) in a 500 ml round-bottomed ¯ask.
p-Toluenesulfonic acid (1.60 g, 9.3 mmol) was added and the reaction
mixture re¯uxed for 24 h under argon. The cooled reaction mixture
was poured into saturated aqueous NaHCO3 (150 ml), and the
organic layer was separated. The aqueous layer was extracted with
CH2Cl2 (2 Â 100 ml) and the combined organic layers were washed
with water (100 ml). The organic extracts were dried with Na2SO4
and evaporated, affording a mixture consisting of all possible
substitution products, 3-phenylpyrazole and pyrazole. The crude
product was dissolved in a small amount of dichloromethane and
applied to a silica column. The column was ®rst eluted with a 4:1
1.367 (3)
N32ÐCuÐN12
N32iÐCuÐN12
N32ÐCuÐN22
88.60 (5)
91.40 (5)
87.61 (5)
N32iÐCuÐN22
N12ÐCuÐN22
N12iÐCuÐN22
92.39 (5)
79.19 (5)
100.81 (5)
C1ÐN11ÐN12ÐCu
C1ÐN21ÐN22ÐCu
10.75 (17)
6.78 (16)
C1ÐN31ÐN32ÐCu
2.43 (19)
Symmetry code: (i) x ‡ 1; y; z ‡ 1.
ꢁ
Acta Cryst. (2006). C62, m30±m32
Goodman et al.
[Cu(C22H18N6)2](ClO4)2Á2C2H3N m31

metal-organic compounds
All H atoms were located in a difference map and then allowed to
ride on their parent C atoms, with Uiso(H) values of 1.2Ueq(C) for
aromatic and 1.5Ueq(C) for methyl H atoms.
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m32 Goodman et al.
[Cu(C22H18N6)2](ClO4)2Á2C2H3N
Acta Cryst. (2006). C62, m30±m32