Cis-trans isomerism in Copper(II) complexes with N-acyl thiourea ligands

Article abstract of DOI:10.1002/zaac.200400030

The N-acyl thiourea complexes bis[N,N-diethyl-N′-(p-nitrobenzoyl)- thioureato]copper(II) (1a,1b) and bis(N,N-diphenyl-N′-benzoylthioureato) copper(II) (2a,2b) crystallize in each case in two modifications. X-ray structural analysis shows that 1a and 1b ar

Full text of DOI:10.1002/zaac.200400030

Artikel
Cis-trans Isomerism in Copper(II) Complexes with N-acyl Thiourea Ligands
a
a
b
c
c
c
´
Wilfredo Hernandez , Evgenia Spodine , Andres Vega , Rainer Richter , Jan Griebel , Reinhard Kirmse , Uwe
Schröderc, and Lothar Beyerc *
a
´
Santiago de Chile, Universidad de Chile, Facultad de Ciencias Quımicas y Farmaceuticas, CIMAT
b
´
´
Santiago de Chile, Universidad de Chile, Facultad de Ciencias Fısicas y Matematicas, CIMAT
c Leipzig, Universität, Fakultät für Chemie und Mineralogie
Received February 6th, 2004.
Dedicated to Professor Joachim Sieler on the Occasion of his 65th Birthday
Abstract. The N-acyl thiourea complexes bis[N,N-diethyl-NЈ-(p-
nitrobenzoyl)-thioureato]copper(II) (1a,1b) and bis(N,N-diphenyl-
NЈ-benzoylthioureato)copper(II) (2a,2b) crystallize in each case in
two modifications. X-ray structural analysis shows that 1a and 1b
are cis-trans isomers. This is very unusual for N-acyl thioureato
complexes because with exception of one platinum(II) complex up
to now only cis complexes have been found. In contrast X-ray
structural analysis of both forms 2a and 2b of the other complex
shows no cis-trans pair. Both modifications are cis complexes. In
solution both isomers of the copper(II) complexes are observable
by EPR spectroscopy.
Keywords: Acylthioureato complexes; Copper; Cis-trans isomers;
Crystal structures; EPR spectroscopy
Cis-trans-Isomerie in Kupfer(II)-Komplexen mit N-Acylthioharnstoff-Liganden
Inhaltsübersicht. Die N-Acylthioharnstoff-Komplexe Bis[N,N-di-
ethyl-NЈ-(p-nitrobenzoyl)thioureato]kupfer(II) (1a,1b) und Bis-
(N,N-diphenyl-NЈ-benzoylthioureato)kupfer(II) (2a,2b) kristallisie-
ren in jeweils zwei Modifikationen. Die Röntgenkristallstruktur-
analyse zeigt, daß 1a und 1b cis-trans-Isomere sind. Das ist sehr
ungewöhnlich für N-Acylthioharnstoff-Komplexe, weil mit Aus-
nahme eines Platin(II)-Komplexes bisher nur cis-Komplexe gefun-
den wurden. Im Gegensatz dazu zeigt die Röntgenkristallstruktur-
analyse der beiden Formen 2a und 2b des anderen Komplexes kein
cis-trans-Paar. Beide Modifikationen sind cis-Komplexe. In Lösun-
gen der Kupfer(II)-Komplexe werden beide Isomere EPR-spektros-
kopisch beobachtet.
Introduction
thoyl thiourea ligand for which a trans arrangement could
be confirmed by X-ray structure analysis [18].
Copper(II) complexes with N-acyl thiourea ligands have al-
ready been described repeatedly in the literature with regard
to their synthesis and general characterization [1Ϫ3], mo-
lecular structures [4Ϫ7], EPR parameters and magnetic
data [8, 9], mass spectra [10], XPS spectra [11], thermo-
dynamic stability, extraction behaviour and chromatogra-
phy [12Ϫ14], electrochemical [15, 16] and biological ac-
tivity [17].
Therefore the finding of a pair of cis-trans isomers in the
case of the copper(II) complex with the ligand N,N-diethyl-
NЈ-(p-nitrobenzoyl) thiourea is at least unusual and should
be reported. Both isomers have been found in the same
sample and characterized by X-ray structure analysis. The
complex
bis[N,N-diethyl-NЈ-(p-nitrobenzoyl)thioureato]-
copper(II) has been synthesized because of its expected can-
cerostatic activity [17].
These copper(II) complexes are in every case nearly
square-planar neutral bis chelates with a cis arrangement of
the ligands at the copper atom. This cis configuration of
the square-planar copper(II) bis chelates is also preferred
by other central atoms such as nickel(II), palladium(II) and
platinum(II). There is only one known exception: a bis
platinum(II) complex with a sterically demanding N-naph-
In continuation of these investigations we found a further
copper(II) complex with the ligand N,N-diphenyl-NЈ-ben-
zoyl thiourea which also crystallizes in two modifications.
The X-ray structure analysis of both forms showed no cis-
trans pair. Both modifications are cis complexes.
Results and Discussion
* Prof. Dr. Dr. h.c. Lothar Beyer
Universität Leipzig
Synthesis
Fakultät für Chemie und Mineralogie
Institut für Anorganische Chemie
Johannisallee 29
D-04103 Leipzig
Fax: ϩ49-341-9736199
Scheme 1 shows the pathway for the syntheses of the cop-
per(II) complexes 1a/1b and 2a/2b.
The copper(II) complexes 1a/1b were obtained by reac-
tion of N,N-diethyl-NЈ-(p-nitrobenzoyl) thiourea 1 with
copper(II) acetate monohydrate. The analogous reaction of
e-mail: beyinorg@chemie.uni-leipzig.de
Z. Anorg. Allg. Chem. 2004, 630, 1381Ϫ1386
DOI: 10.1002/zaac.200400030
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W. Hernandez, E. Spodine, A. Vega, R. Richter, J. Griebel, R. Kirmse, U. Schröder, L. Beyer
Schema 1
N,N-diphenyl-NЈ-benzoyl thiourea 2 with copper(II) acet-
ate monohydrate yielded the complexes 2a/2b.
Unexpectedly, in both samples always two crystalline
modifications have been found the crystals of which were
all suitable for X-ray structure analysis.
Molecular structures
In the case of the ligand N,N-diethyl-NЈ-(p-nitrobenzoyl)
thiourea 1 the two different modifications of the copper(II)
complex are a cis isomer 1a and a trans isomer 1b the crys-
tals of which showed no visible differences in habit and col-
our. The molecular structure of 1a is shown in Figure 1.
In the copper(II) complex 1a the ligand forms by coordi-
nation a bis chelate with cis arrangement of the ligator
atoms S and O. The coordination is square-planar with an
angle Cu1S1O1/Cu1S2O2 of 2.5(1)°.
All bond lengths are in the expected ranges. In the chelate
rings the distances N1ϪC1 and N4ϪC13 in the thiourea
fragment (1.353; 1.354 A) are significantly longer than the
˚
Fig. 1 Molecular structure of cis-Bis[N,N-diethyl-NЈ-(p-nitroben-
zoyl)thioureato]-copper(II) 1a. Selected bond lengths/A and
angles/°:
Cu1ϪS1 2.244(1), Cu1ϪS2 2.246(1), Cu1ϪO1 1.942(2), Cu1ϪO2 1.925(2),
S1ϪC1 1.722(2), S2ϪC13 1.728(2), O1ϪC2 1.272(3), O2ϪC14 1.265(3),
N1ϪC1 1.353(3), N1ϪC2 1.315(3), N4ϪC13 1.354(3), N4ϪC14 1.318(3),
S1ϪCu1ϪO1 93.83(5), S2ϪCu1-O2 93.67(5)
˚
distances N1ϪC2 and N4ϪC14 at the benzoyl group
˚
(1.315; 1.318 A).
Both phenyl rings are only slightly twisted with regard to
the planes of the chelate rings (C3-C8/O1N1C2 13.6(3)°
and C15-C20/O2N4C14 4.7(5)°). The p-nitro groups are
nearly coplanar with the phenyl rings.
In the crystal structure the complex molecules are ar-
ranged in such a way that O atoms of the p-nitro groups of
two neighbouring molecules extend the square-planar coor-
dination to a strongly tetragonally distorted octahedral co-
(1Ϫx,Ϫy,Ϫz)]. The molecular structure of 1b is shown in
Figure 2.
As in the structure of 1a the ligand coordinates by S and
O and forms a bis chelate. However, the molecular sym-
metry is Ci which gives a trans arrangement of the ligator
atoms with a strictly square-planar coordination.
˚
ordination with additional Cu-O distances of 2.982 A
˚
[Cu1ϪO4 (1Ϫx,Ϫ1Ϫy,Ϫz)] and 2.955 A [Cu1ϪO5
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Cis-trans Isomerism in Copper(II) Complexes
Fig. 2 Molecular structure of trans-Bis[N,N-diethyl-NЈ-(p-nitroben-
˚
zoyl)thioureato]-copper(II) 1b. Selected bond lengths/A and
angles/°:
Cu1ϪS1 2.253(1), Cu1ϪO1 1.901(2), S1ϪC1 1.714(2), O1ϪC2 1.261(3),
N1ϪC1 1.356(3), N1ϪC2 1.310(3), S1ϪCu1ϪO1 93.39(5)
Fig. 3 Molecular structure of cis-Bis(N,N-diphenyl-NЈ-benzoylthio-
˚
ureato)copper(II) 2a (Mod. 1). Selected bond lengths/A and
angles/°:
All bond lengths are in the expected ranges and show no
differences to 1a. The length of the bond N1ϪC1 (1.356 A)
˚
Cu1ϪS1 2.233(1), Cu1ϪS2 2.237(1), Cu1ϪO1 1.937(2), Cu1ϪO2 1.928(2),
S1ϪC1 1.722(3), S2ϪC21 1.725(3), O1ϪC2 1.258(4), O2ϪC22 1.268(4),
N1ϪC1 1.330(4), N1ϪC2 1.330(4), N3ϪC21 1.335(4), N3ϪC22 1.322(4),
S1ϪCu1ϪO1 94.26(7), S2ϪCu1ϪO2 94.91(7)
is again significantly longer than the length of the bond
˚
N1ϪC2 (1.310 A).
The angle between the phenyl ring and the chelate ring is
of the same order as in 1a (C3-C8/O1N1C2 4.4(3)°).
By packing effects in the crystal structure the square-
planar coordination is again extended to a tetragonally dis-
torted octahedral coordination with two centrosymmetr-
Figure 4 shows the molecular structure of 2b.
The molecular structure of 2b is nearly identical with the
molecular structure of 2a. The arrangement of the ligands
at the central atom is cis with coordination by the S and O
ligator atoms. The coordination angle Cu1S1O1/Cu1S2O2
is 12.4(1)°.
As in 2a the distances N1ϪC1 (1.329 A) and N3ϪC21
(1.315 A) in the thiourea fragment and the distances
N1ϪC2 (1.323 A) and N3ϪC22 (1.327 A) at the benzoyl
group have the same length.
The angles between the phenyl rings C3-C8 and C23-C28
and the chelate rings are significantly different [C3-C8/
O1N1C2 26.9(3)° and C23-C28/O2N3C22 1.7(4)°]. As in
2a the phenyl rings of the diethylamino groups are nearly
perpendicularly arranged [C9-C14/C15-C20 77.9(1)° and
C29-C34/C35-C40 64.6(1)°].
˚
ically arranged O atoms with a CuϪO distance of 2.947 A
[Cu1ϪO3 (0.5-x, Ϫ0.5ϩy, 0.5ϩz) and Cu1ϪO3Ј
(Ϫ0.5ϩx, 0.5Ϫy, Ϫ0.5ϩz)].
In contrast to ligand 1 the two found modifications of
the copper(II) complex with N,N-diphenyl-NЈ-benzoyl thio-
urea 2 are no cis-trans isomers. Both modifications are cis
configurated in the usual manner. Both substances form
brown crystals. The molecular structure of 2a is shown in
Figure 3.
˚
˚
˚
˚
The bis complex 2a shows a coordination by S and O
with a slightly distorted square-planar cis arrangement (co-
ordination angle Cu1S1O1/Cu1S2O2 11.5(1)°).
The bond lengths have the expected values, but the dis-
˚
˚
tances N1ϪC1 (1.330 A) and N3ϪC21 (1.335 A) in the
thiourea fragment are in this complex equal to the distances
˚
˚
N1ϪC2 (1.330 A) and N3ϪC22 (1.322 A) at the benzoyl
group.
EPR measurements
The phenyl rings C3-C8 and C23-C28 are slightly twisted
with regard to the planes of the chelate rings [C3-C8/
O1N1C1 18.9(3)° and C23-C28/O2N3C22 14.3(6)°]. The
phenyl rings of the diphenylamino groups are arranged by
sterical reasons nearly perpendicular [C9-C14/C15-C20
82.7(1)° and C29-C34/C35-C40 64.5(1)°].
The appearance of two isomers for the copper complex 1a/
1b leads us to record the EPR spectrum of 1a/1b in liquid
solutions. The room-temperature EPR spectrum is shown
in Figure 5. For one copper(II) species the typical 63,65Cu
hyperfine structure quartet is expected due to the interac-
tion of the unpaired electron with the Cu nuclei
Z. Anorg. Allg. Chem. 2004, 630, 1381Ϫ1386
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W. Hernandez, E. Spodine, A. Vega, R. Richter, J. Griebel, R. Kirmse, U. Schröder, L. Beyer
Fig. 5 X-band EPR spectrum of 1a/1b in CH2Cl2 at T ϭ 295 K.
The stick spectra denote the individual Cu hyperfine lines of both
isomers.
Line-broadenings at lower and especially at higher tempera-
tures prevent informations about the equilibrium of the cis
and trans forms of the complexes under study. Nevertheless,
the EPR spectra show the presence of both isomers of the
copper(II) complexes in liquid solution in a certain ratio.
The isolation of crystals of the cis or the trans isomer used
for the X-ray analysis has, therefore, some accidential
character. According to the concentration ratio cis/trans de-
tected by EPR the chance to isolate the cis complex is
much larger.
Fig. 4 Molecular structure of cis-Bis(N,N-diphenyl-NЈ-benzoylthio-
ureato)copper(II) 2b (Mod. 2). Selected bond lengths/A and
angles/°:
Cu1ϪS1 2.226(1), Cu1ϪS2 2.239(1), Cu1ϪO1 1.924(2), Cu1ϪO2 1.922(2),
S1ϪC1 1.727(2), S2ϪC21 1.737(2), O1ϪC2 1.248(3), O2ϪC22 1.250(3),
N1ϪC1 1.329(3), N1ϪC2 1.323(3), N3ϪC21 1.315(3), N3ϪC22 1.327(3),
S1ϪCu1ϪO1 94.24(6), S2ϪCu1ϪO2 94.41(6)
˚
Experimental
(I(63,65Cu)ϭ3/2). However, in the spectrum represented in
Figure 5 in addition to an intense Cu hyperfine structure
quartet in the high-field part there are further lines which
indicate the presence of a second copper(II) species with a
lower concentration (about 10 % of that of the main com-
ponent). Stick spectra of the two copper(II) complexes are
included in Figure 5.
Synthesis of the ligands
N,N-Diethyl-NЈ-(p-nitrobenzoyl) thiourea (1)
A solution of p-nitrobenzoyl chloride (50 mmol, 9,3 g) in acetone
(30 mL) was added dropwise to a solution of KSCN (50 mmol,
4.9 g) in acetone (30 mL) and stirred for 1 h at 5 °C. The reaction
mixture was then filtered. A solution of diethylamine (50 mmol,
5,2 mL) in acetone (20 mL) was added dropwise to the yellow fil-
trate and stirred at room temperature for 2 h.The solution was con-
centrated to half the volume under reduced pressure and then
placed in a refrigerator for one week. Yellow crystals were collected
by filtration, washed with ethanol and dried in vacuo.
From the spectrum the following isotropic g0 and hyper-
Cu
fine splitting constants a0 have been derived:
Cu
(a)
(b)
g0 ϭ 2.084 0.002
g0 ϭ 2.096 0.002
a0 ϭ (78.5 1.0) · 10Ϫ4cmϪ1
a0 ϭ (75.1 1.0) · 10Ϫ4cmϪ1
Cu
C12H15O3N3S (Mϭ281.33); square yellow crystals, m.p. 163-
165 °C; yield: 83 %. Anal. Calc.: C 51.25; H 5.34; N 14.95; S
11.39 %. Found: C 50.91; H 5.38; N 14.88; S 10.96 %.
IR (KBr, cmϪ1): ν(N-H) 3284 cmϪ1 (br, m), ν(CϭO) 1648 cmϪ1 (vs), ν(Cϭ
S) 1230 (s). 1H-NMR (300 MHz, CDCl3): δ 1.31 (t, 3H, CH3), 1.36 (t, 3H,
CH3), 3.61 (q, 2H, CH2), 4.03 (q, 2H, CH2), 8.01 (d, 2Hortho, p-NO2Ph), 8.34
(d, 2Hmeta, p-NO2-Ph), 8.41 (s, 1H, NH). 13C-NMR (75.5 MHz, CDCl3): δ
11.79, 13.65 (CH3); 48.23 (CH2); 124.43, 129.42, 138.46, 140.9 (ortho, meta,
para, i-Ph); 162.35 (CϭO), 178.82 (CϭS).
The parameter set (a) will be attributed to the cis isomer 1a
according to what has been found earlier from single-crystal
EPR measurements on bis(N,N-diethyl-NЈ-benzoylthio-
ureato)copper(II) [8]. Thus, parameter set (b) is ascribed to
the trans isomer 1b. The difference between the parameter
sets for both isomers is not too large to questionate a
CuS2O2 coordination. Interestingly, the EPR spectrum of
2a/2b in liquid solutions is similar to that of 1a/1b also
showing the presence of both isomers with the trans com-
plex in a low amount.
N,N-Diphenyl-NЈ-benzoyl thiourea (2)
Temperature-dependent EPR studies in the temperature
range 240-360 K (solvent: toluene) were not successful.
A solution of benzoyl chloride (50 mmol, 5,8 mL) in acetone
(30 mL) was added dropwise to a solution of KSCN (50 mmol,
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Cis-trans Isomerism in Copper(II) Complexes
Table 1 Crystal data and details of structure determinations
1a
1b
2a
2b
Empirical formula
Mr /g·molϪ1
C24H28CuN6O6S2
624.18
C24H28CuN6O6S2
624.18
green prisms
monoclinic
P21/n
10.359(1)
10.804(1)
11.959(1)
C40H30CuN4O2S2
726.34
C40H30CuN4O2S2
726.34
Colour, habit
Crystal system
Space group
green prisms
triclinic
brown prisms
triclinic
dark brown plates
triclinic
¯
¯
¯
P1
P1
P1
˚
a /A
9.685(2)
10.546(2)
13.569(3)
87.474(3)
81.734(4)
86.313(3)
1367.8(4)
2; 646
10.009(2)
11.161(2)
16.551(3)
105.176(4)
91.397(4)
104.072(4)
1723.3(6)
2; 750
10.771(1)
13.131(1)
14.052(1)
75.591(1)
79.744(1)
66.636(1)
1760.1(2)
2; 750
˚
b /A
˚
c /A
α /°
β /°
γ /°
93.947(2)
3
˚
V /A
1335.3(2)
2; 646
1.552
Z; F(000)
ρcalc /g·cmϪ3
1.515
1.400
1.371
Crystal size /mm
2θ range /°
0.3x0.2x0.2
3.8Ϫ58.5
213(2)
1.002
9033
6401
5629
0.8x0.3x0.1
5.0Ϫ55.1
293(2)
1.026
10769
2911
0.4x0.1x0.05
4.0Ϫ56.0
213(2)
0.797
11475
7889
5689
0.8x0.6x0.4
3.4Ϫ55.1
293(2)
0.780
12912
7509
5579
Temperature /K
Absorption coeffizient µ /mmϪ1
Measured reflections
Unique reflections
Observed reflections
(I > 2σ(I))
2257
Refined parameters
wR2 (unique reflections)
R1 (observed reflections)
Largest difference peak
464
180
562
442
0.0959
0.0441
0.35/Ϫ0.43
0.1028
0.0404
0.43/Ϫ0.27
0.1187
0.0625
0.46/Ϫ0.44
0.1227
0.0469
0.43/Ϫ0.21
Ϫ3
˚
and hole /e·A
4,9 g) in acetone (30 mL).The reaction mixture was refluxed for 1 h
and then cooled to room temperature. A solution of diphenylamine
(50 mmol, 8,46 g) in acetone (20 mL) was added dropwise to the
mixture during 20 minutes and then stirring was continued for 2 h.
KCl was removed by filtration and the yellow filtrate was placed
into water (250 mL) under constant agitation.The yellow precipi-
tate was separated by filtration, washed several times with cold
water, ethanol and dried in vacuo.The crude product was purified
from CH2Cl2-CH3OH (2:1, v/v).
C20H16ON2S (Mϭ332.42); pale yellow solid, m.p. 122-124 °C;
yield: 90 %. Anal. Calc.: C 72.26; H 4.82; N 8.43; S 9.65 %. Found:
C 71.89; H 4.97; N 8.51; S 9.58 %.
IR (KBr, cmϪ1): ν(N-H) 3223 cmϪ1 (m,br), ν(CϭO) 1692 cmϪ1 (vs), ν(Cϭ
S) 1221 (vs). 1H-NMR (300 MHz, CDCl3): δ 7.36 (m, 5H, NPh2), 7.41 (m,
5H, NPh2), 7.39 (t, 2Hmeta, Ph), 7.52 (t, 1Hpara, Ph), 7.59 (d, 2Hortho, Ph),
8.69 (s, 1H, NH). 13C-NMR (75.5 MHz, CDCl3): δ 127.2, 128.2, 129.69
(NPh2), 127.9, 129.2, 133.0, 133.3 (meta, ortho, para, i-Ph), 162.63 (CϭO),
182.76 (CϭS).
C24H28O6N6S2Cu (Mϭ624.18); green crystals, m.p. 204-206 °C;
yield: 90 %. Anal. Calc.: C 46.14; H 4.49; N 13.46; S 10.25, Cu
10.17 %. Found: C 45.61; H 4.63; N 13.39; S 10.27, Cu 10.26 %.
IR (KBr, cmϪ1): ν(CϭO) 1625 cmϪ1 (w), ν(CϭS) 1205 (m). FAB(؉)-MS
(matrix: 3-NBA): m/z 624 (Mϩ, 86.14 %); 613.1 (3-NBA, 100 %), 342.5 ([M-
L]ϩ, 25.6 %). µeff (Tϭ296 K) 1.82 B.M.
Bis(N,N-diphenyl-NЈ-benzoylthioureato)copper(II)
(2a/2b)
To a stirred solution of the ligand 2 (1 mmol) in ethanol (30 mL)
was added dropwise a solution of Cu(CH3COO)2 · H2O (0.5 mmol)
in ethanol (30 mL). The reaction mixture was stirred at 50 °C for
1 h followed by further stirring at room temperature for 24 h. The
solid complexes were filtrated, washed with ethanol and dried un-
der vacuum. The brown precipitate was dissolved in hot methanol
and left to evaporate slowly at room temperature. After few days,
single crystals suitable for X-ray diffraction studies were obtained.
C40H30O2N4S2Cu (Mϭ726.34); brown needles, m.p. 218-220 °C;
yield: 61 %. Anal. Calc.: C 66.08; H 4.13; N 7.71; S 8.81; Cu
8.74 %. Found: C 65.91; H 4.20; N 7.87; S 8.57, Cu 8.69 %.
Synthesis of the copper(II) complexes
Bis[N,N-diethyl-NЈ-(p-nitrobenzoyl)thioureato]-
copper(II) (1a/1b)
IR (KBr, cmϪ1): ν(CϭO) 1586 cmϪ1 (m), ν(CϭS) 1262 (m). µeff (T ϭ 296 K)
1.92 B.M.
Solutions of ligand 1 (1 mmol) in methanol (30 mL) and Cu-
(CH3COO)2 · H2O (0.5 mmol) in methanol (30 mL) were mixed
together and stirred for 1 h under reflux. Then the reaction mixture
was stirred at room temperature for 24 h. The green solution was
filtrated and the filtrate was evaporated to dryness under reduced
pressure to yield a dark green solid. The solid was washed several
times with small portions of cold ethanol and dried in vacuo. The
precipitate was dissolved in acetone and then the green solution
was stored in a refrigerator. After two weeks, the solution was left
to evaporate slowly at room temperature. Suitable X-ray quality
crystals were obtained within a few days.
Crystal structure determinations
The data for the crystal structure determinations were collected
on a Siemens-CCD-Smart Diffractometer (MoKα radiation, λ ϭ
0.71073 A, graphite monochromator) at a measuring temperature
of 213(2) K for 1a and 2a and 293(2) K for 1b and 2b. The intensit-
ies were corrected for Lorentz and polarization effects and for ab-
sorption using SADABS.
˚
Z. Anorg. Allg. Chem. 2004, 630, 1381Ϫ1386
zaac.wiley-vch.de
 2004 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim
1385

´
W. Hernandez, E. Spodine, A. Vega, R. Richter, J. Griebel, R. Kirmse, U. Schröder, L. Beyer
The structures were solved by direct methods and refined aniso-
[4] R. Richter, L. Beyer, J. Kaiser, Z. Anorg. Allg. Chem. 1980,
461, 67.
[5] R. Flores-Centurion, R. Richter, J. Angulo-Cornejo, L. Beyer,
Bol. Soc. Quim. Peru 1999, 65, 211.
[6] J. R. B. Gomes, M. A. V. Ribeiro da Silva, Inorg. Chem. Com-
mun. 2003, 6, 149.
[7] U. Schröder, R. Richter, L. Beyer, J. Angulo-Cornejo, M.
Lino-Pacheco, A. Guillen, Z. Anorg. Allg. Chem. 2003, 629,
1051.
[8] R. Kirmse, L. Beyer, E. Hoyer, Chem. Phys. Lett. 1976, 44,
173.
tropically [19]. The positions of the hydrogen atoms for 1a and 2a
were found by difference syntheses and refined isotropically. For 1b
and 2b the positions of the hydrogen atoms were calculated geo-
metrically and taken into account with isotropic temperature fac-
tors 1.2 times higher than Ueq of the parent C atom. Details of
crystal data and structure determinations are given in Table 1.
Further details of the crystal structure determinations are available
on request from the Cambridge Crystallographic Data Center, 12
Union Road, Cambridge CB2 1 EZ, UK, on quoting the depositing
numbers CCDC-236863 (1a), CCDC-236864 (1b), CCDC-236865
(2a) and CCDC-236866 (2b), the name of the authors, and the
journal citation.
´
[9] E. Guillon, I. Dechamps-Olivier, A. Mohamadou, J.-P. Bar-
bier, Inorg. Chim. Acta 1998, 268, 13.
[10] R. Herzschuh, B. Birner, L. Beyer, F. Dietze, E. Hoyer, Z.
Anorg. Allg. Chem. 1980, 464, 159.
[11] J. V. Salyn, N. K. Zumadilov, V. I. Nefedov, R. Scheibe, G.
Leonhardt, L. Beyer, E. Hoyer, Z. Anorg. Allg. Chem. 1977,
432, 275.
EPR measurements
The EPR spectra were recorded with a BRUKER ESP 300 E spec-
trometer at X-band frequency (f ϭ 9.4382 GHz) in liquid CH2Cl2
solutions at T ϭ 295 K. For the T-dependent studies in the tem-
perature range 240 Յ T Յ 360 K toluene was used as solvent.
[12] K.-H. König, M. Schuster, G. Schneeweis, B. Steinbrech, Fre-
senius Z. Anal. Chem. 1984, 319, 66.
[13] K.-H. König, M. Schuster, B. Steinbrech, G. Schneeweis, R.
Schlodder, Fresenius Z. Anal. Chem. 1985, 321, 457.
[14] P. Mühl, K. Gloe, F. Dietze, E. Hoyer, L. Beyer, Z. Chem.
1986, 26, 81.
Acknowledgement. W. H. thanks the DAAD for the A/01/176226
doctoral scholarship granted in Chile. Financial support from grant
FONDAP 11980002 is gratefully acknowledged.
´
[15] E. Guillon, A. Mohamadou, I. Dechamps-Olivier, J.-P. Bar-
bier, Polyhedron 1996, 15, 947.
[16] J. Losada, I. del Peso, L. Beyer, Transition Met. Chem. 2000,
25, 112.
´
[17] W. Hernandez, E. Spodine, L. Beyer, U. Schröder, R. Richter,
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