Synthesis, crystal structure, and spectroscopic and magnetic properties of a dinuclear iron(III) complex asymmetrically bridged by a phenoxo and a methoxo group

Article abstract of DOI:10.1515/znb-2005-0905

A new dinuclear iron(III) derivative Fe₂L(OCH ₃)Cl₂ (L = 1,3-bis[N-(5-chloro-2-hydroxybenzylidene)-2- aminoethyl]-2-(5-chloro-2-hydroxyphenyl)imidazolidine) has been synthesized, it crystal structure determined and magneti

Full text of DOI:10.1515/znb-2005-0905

Synthesis, Crystal Structure, and Spectroscopic and Magnetic Properties
of a Dinuclear Iron(III) Complex Asymmetrically Bridged by a Phenoxo
and a Methoxo Group
a
b
b
C. T. Zeyrek , A. Elmali , and Y. Elerman
a
Turkish Atomic Energy Authority, 06690 Lodumlu-Ankara, Turkey
Department of Engineering Physics, Faculty of Engineering, Ankara University,
b
0
6100 Besevler-Ankara, Turkey
Reprint requests to Prof. Dr. A. Elmali. E-mail: elmali@eng.ankara.edu.tr
Z. Naturforsch. 60b, 940 – 944 (2005); received May 17, 2005
A new dinuclear iron(III) derivative Fe L(OCH )Cl (L = 1,3-bis[N-(5-chloro-2-hydroxybenzyl-
2
3
2
idene)-2-aminoethyl]-2-(5-chloro-2-hydroxyphenyl)imidazolidine) has been synthesized, it crystal
structure determined and magnetically characterized. The two iron(III) ions are asymmetrically
˚
bridged by a phenoxo and a methoxo group and separated by 3.150(2)A. The magnetic susceptibility
of the complex was measured over the range 5 – 349.3 K and the observed data were successfully
−
−→
simulated by the equation based on the spin-Hamiltonian operator H = −J S · S , indicating very
1
−
2
1
weak antiferromagnetic coupling between the iron ions with J = −11.3 cm . The magnetic and
structural parameters of the compound and the nature of the magnetic super-exchange interaction are
discussed and compared with data of similar dinuclear iron(III) complexes.
Key words: Dinuclear Iron(III) Complex, Super-Exchange Interactions, Antiferromagnetic
Coupling, Schiff Base, Imidazolidine
Introduction
We reported previously the structures and mag-
netic properties of several dinuclear iron(III) com-
plexes [16, 20 – 24]. In an attempt to accumulate more
data for further discussion of magneto-structural cor-
relations for this type of complexes, we present here
the synthesis, X-ray structural and magnetic character-
ization of a derivative of the closely related ligand L,
Fe L(OCH )Cl containing a cyclic Fe-OMe-Fe-OPh
The electronic and magnetic properties of dinuclear
iron(III) complexes have been extensively studied in
recent years [1 – 3]. They provide structural models
for dinuclear sites in several proteins involved in oxy-
gen storage by hemerytherin and oxygen activation by
methanemonooxygenase [4 – 7]. In addition, these sys-
tems were treated as model systems for the understand-
ing of the size and magnitude of exchange coupling in-
teractions by theoretical considerations.
2
3
2
unit (Fig. 1).
Experimental Section
Preparation of Fe L(OCH )Cl
2
Gorun and Lippard suggested a quantitative magne-
tostructural relationship for dinuclear iron(III) centers,
doubly bridged by oxygen atoms [8]. The influence of
the geometrical parameters in Fe O bridging systems,
2
3
The dinuclear Fe(III) complex was prepared in two steps
Fig. 1). A solution of triethylenetetramine (2.2 g, 15 mmol)
(
2
2
in methanol (20 ml) was added dropwise to a methanolic so-
lution (40 ml) of 5-chlorosalicylaldehyde (6.32 g, 45 mmol)
with stirring at room temperature. The Schiff base ligand
was obtained in the form of yellow crystals. For the prepa-
ration of the Fe(III) complex, a 15 ml quantity of a 0.1 M
the Fe–O bond distances and the Fe–O–Fe bond an-
gles, on the super-exchange integral, however, is not
yet understood in detail due to lack of structural data
[9 – 11]. Studies of some iron complexes have shown
that the oxo-bridge is responsible for the strong antifer-
solution of CH ONa in methanol was added to a solution of
3
−
1
romagnetic coupling (usually −50 > J > −200 cm
)
FeCl ·6H O in the same solvent (0.54 g, 2 mmol, in 20 ml).
3
2
[
12– 15] and that complexes with alkoxo, phenoxo, or
To the resulting solution was added with stirring a solution
hydroxo bridges are weakly coupled (usually 0 > J > of L in methanol (0.58 g, 1 mmol). The dark blue solu-
−
1
−
30 cm ) [15, 16 – 19].
tion was allowed to evaporate at room temperature for one
0
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C. T. Zeyrek et al. · Dinuclear Iron(III) Complex
941
Table 1. Crystallographic data for the investigated complex.
Table 2. Selected bond lenghts ( A˚ ) and bond angles ( ) char-
◦
acterizing the inner coordination sphere of the iron(III) cen-
ters (see Fig. 2 for labeling scheme adopted).
Formula
C28H27Cl5Fe2N4O4
772.49
Formula weight (g.mol 1)
−
Crystal system
orthorhombic
Pbcn
Fe1···Fe2
Fe1–N1
Fe1–N2
Fe1–O1
Fe1–O2
Fe1–O3
Fe1–Cl1
3.150(2)
2.108(1)
2.315(1)
1.893(1)
2.073(1)
1.967(1)
2.310(1)
Space group
Fe2–N3
Fe2–N4
Fe2–O2
Fe2–O3
Fe2–O4
Fe2–Cl2
2.280(1)
2.088(1)
2.096(1)
1.956(1)
1.897(1)
2.316(1)
˚
a [A]
12.790(1)
18.779(1)
24.950(2)
5992.6(7)
8
˚
b [A]
˚
c [A]
˚
3
Vol [A ]
Z
Dcalc [g·cm 3]
−
1.712
1.457
O1–Fe1–O2
O1–Fe1–O3
O2–Fe1–O3
O1–Fe1–N1
O2–Fe1–N1
O3–Fe1–N1
O1–Fe1–N2
O2–Fe1–N2
O3–Fe1–N2
N1–Fe1–N2
N2–Fe1–Cl1
O1–Fe1–Cl1
O2–Fe1–Cl1
O3–Fe1–Cl1
N1–Fe1–Cl1
Fe1–O2–Fe2
92.1(1)
103.4(1)
76.0(1)
88.3(1)
89.8(1)
162.3(1)
164.4(1)
82.6(1)
89.7(1)
77.0(1)
90.6(1)
96.3(1)
170.3(1)
96.3(1)
95.5(1)
98.2(1)
O2–Fe2–O3
O2–Fe2–O4
O3–Fe2–O4
O2–Fe2–N3
O2–Fe2–N4
O3–Fe2–N4
O3–Fe2–N3
O4–Fe2–N3
O4–Fe2–N4
N3–Fe2–N4
O2–Fe2–Cl2
O3–Fe2–Cl2
O4–Fe2–Cl2
N3–Fe2–Cl2
N4–Fe2–Cl2
Fe1–O3–Fe2
76.6(1)
90.6(1)
102.5(1)
82.9(1)
87.9(1)
160.5(1)
89.7(1)
164.5(1)
89.2(1)
76.6(1)
171.4(1)
97.5(1)
96.8(1)
90.9(1)
96.5(1)
106.8(1)
−
1
µ [cm
F(000)
]
3136
◦
◦
θ Range for data collection
Index ranges
2.53 < θ < 30.17
0 ≤ h ≤ 18, 0 ≤ k ≤ 26
0
≤ l ≤ 34
Reflections collected
Independent reflections
Data / parameters
Goodness-of-fit on F
Final R indices [I > 2σ(I)]
Final R indices (all data)
8398
8390
8390 / 383
1.192
R = 0.0306, wR = 0.0828
R = 0.0396, wR = 0.0974
0.310 and −0.904
2
˚
−3
]
Largest diff. peak and hole [eA
Fig. 2. View of the molecule. Displacement ellipsoids are
plotted at the 50% probability level. The hydrogen atoms are
omitted for clarity.
day to give prismatic dark blue crystals, which were col-
lected, washed with cold absolute ethanol and finally dried
in air. Yield 0.76 g (67.9%), C H Cl Fe N O (772.49):
2
8
27
5
2 4 4
calcd. C 43.61, H 3.45, N 7.34, Fe 14.50; found C 43.54,
−
1
H 3.52, N 7.25, Fe 14.46. Infrared spectrum (cm , KBr
−1
disk): ν˜ (phenolic C–O) 1539 cm ; ν˜ (azomethinic C–N)
Fig. 1. Preparation of the dinuclear iron(III) complex.
−1
1
622 cm
.
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9
42
C. T. Zeyrek et al. · Dinuclear Iron(III) Complex
X-ray structure determination
Table 3. Least-squares pseudomirror plane within the
Fe L(OCH )Cl
molecule, 0.362(2)x + 18.745(2)y +
2
3
2
Crystals of Fe L(OCH )Cl were mounted on an Enraf- 1.332(2)z = 2.845(3).
2
3
2
Nonius CAD-4 diffractometer (graphite monochromatized
Mo-Kα radiation, λ = 0.71073 A) [25]. Experimental con-
ditions are summarized in Table 1. The structure was solved
by SHELXS-97 and refined with SHELXL-97 [26, 27]. The
˚
˚
˚
Atom
O2
Dev (A)
Atom
O3
C22
C24
C26
C28
Dev (A)
0.050 (1)
−0.016 (1)
0.026 (1)
−0.024 (1)
C21
C23
C25
C27
Cl4
0.030 (1)
−0.021 (1)
−0.009 (1)
−0.024 (1)
positions of the H atoms bonded to C atoms were calculated
˚
−0.029 (1)
(C-H distance 0.96 A) and refined using a riding model. H
0.036 (1)
atom displacement parameters were restricted to be 1.2Ueq
of the parent atom. Selected bond distances and bond angles
−0.020 (1)
are listed in Table 2. An ORTEP view of the molecular struc- spectively. The bridging angle at the phenoxy oxygen
◦
ture is given in Fig. 2 [28]. Crystallographic data (excluding
structure factors) have been deposited with the Cambridge
Crystallographic Data Center as supplementary publication
no. CCDC-271906 [29].
atom, 98.2(3) , is smaller than that at the methoxy oxy-
◦
gen atom, 106.8(4) . The average bridging phenolic
oxygen-iron bond length is 2.085(1) A, the average
Fe–OCH distance is 1.962(2) A. The Fe–N(imine)
bond lengths of 2.108(1) and 2.088(1) A are signifi-
˚
˚
3
˚
Susceptibility measurements
cantly shorter than the Fe–N(amine) bond lengths of
˚
Variable-temperature magnetic susceptibility measure- 2.315(1) and 2.280(1) A. The overall geometrical dis-
ments of a powdered sample were performed with a QUAN- tortion is as expected for an octahedral low-spin d
5
TUM Design SQUID magnetometer in the temperature range
iron(III) ion with hexadentate chelation. The geometry
5
– 349.3 K. The applied field was 2 T. Diamagnetic correc-
is similar to that of related binuclear iron complexes
15, 16 – 19]. The ipso-phenoxy and methoxy carbon
atoms are displaced on opposite sides of the bridging
plane by 0.216(1) A for C27 and 0.148(1) A for C28,
respectively.
tions of the molar magnetic susceptibility were applied using
Pascal’s constant [30]. The effective magnetic moments were
calculated by the equation µeff = 2.828(χT)1 , where χ is
the magnetic susceptibility per Fe(III) ion.
[
/2
˚
˚
The complexation reaction is different from the se-
lective imidazolidine ring opening reaction observed
earlier in a different ligand system [31]. Imidazolidine
ring-cleavage with removal of one aldehyde molecule
was observed for reactions of the L ligand with ferrous
perchlorate hexahydrate in 1:2 mole ratio in aqueous
methanol in air [32]. However, the title complex was
prepared by reacting the ligand with FeCl ·6H O in
Results and Discussion
X-ray crystal structures
The crystal structure of Fe L(OCH )Cl is built of
2
3
2
discrete dinuclear molecules. In the dinuclear unit, the
Fe(III) ions are asymmetrically bridged by phenoxy
and methoxy oxygen atoms. The geometry around
the iron(III) ions is distorted octahedral, as shown
in Fig. 2. One oxygen and two nitrogen atoms (cis)
of the Schiff base ligand (L) occupy three coordi-
nation sites; the remaining three sites are occupied
by the two bridging oxygen atoms of the phenoxy
and methoxy groups and a terminal chlorine atom.
The whole molecule has a nearly perfect Cs symme-
3
2
1
:2 mole ratio in in air, and the imidazolidine ring is
not cleaved regenerating the diamine.
Spectroscopic properties
The most significant effects of coordination on the
try with the mirror plane perpendicular to the iron- vibrational spectrum of free salicylaldimine Schiff lig-
oxygen ring. In the compound, the bridging oxygen ands have previously been observed between ∼ 1500
−
1
atoms O2 and O3, and the carbon atoms of C21-C27, and ∼ 1650 cm [33– 35], attributed to the azome-
and C28 lie approximately on this mirror plane. Devia- thinic ν(C–N) and phenolic ν(C–O) stretching modes,
tions of these atoms from the least-squares pseudomir- respectively. In this spectral region the free Schiff
ror plane are given in Table 3. The dihedral angle be- base ligand L exhibits two strong bands, azome-
◦
−1
tween the Fe1O2O3 and Fe2O2O3 planes is 11.9(1) . thinic ν(C–N) at 1640 cm
and phenolic ν(C–O)
[32]. On complex formation, the
plane by 0.082(1) A for Fe1 and Fe2. The Fe Fe and ν(C–N) decreases, and ν(C–O) increases: to 1621 and
−
1
The iron(III) ions are displaced from the coordination at 1503 cm
˚
···
···
˚
−1
O2 O3 separations are 3.150(2) and 2.514(2) A, re- 1539 cm for Fe L(OCH )Cl , respectively.
2
3
2
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C. T. Zeyrek et al. · Dinuclear Iron(III) Complex
943
Table 4. Structural and magnetic data for a series of asym-
metrically bridged Fe(III)–Fe(III) complexes.
Compound
Fe···Fe ꢁFe–Oꢂ
P
(A)
α
J
(cm
Jcalc
(cm )
˚
˚
e
˚
f
◦ g
−1
−1 i
(
A)
(A)
( )
)
Present work 3.150
2.024
2.024
2.013
2.018
2.023
1.956 102.5 −11.3 −15.3
a
b
c
d
a
3.133
3.139
3.162
3.662
1.965 101.7 −10.8 −13.7
1.975 102.5 −8.0
1.965 103.5 −7.4
1.986 125.4 −7.7
−12.1
−13.7
−10.5
[Fe2(L)(OCH3)Cl]2 (L = 1,3-bis[N-(3,5-dichloro-2-hydroxybenz-
ylidene)-2-aminoethyl]-2-(3,5-dichloro-2-hydroxyphenyl)imidazol-
b
idine) [24]; [Fe2(sal3trien)(OMe)] (sal3trien = trisalicylidene-tri-
c
d
ethylene-tetraamine) [10]; [Fe2(sal3trien)(OH)] [37]; [Fe2(bbap)-
OEt)(O2PPh2)(H2O)] (bbap = 2,6-bis[bis(2-benzimidazolylmeth-
(
e
yl)aminomethyl]-4-methylphenol) [38]; ꢁFe–Oꢂ is the average dis-
tance between the iron and the bridging oxygen atoms of hydr-
Fig. 3. The molar magnetic susceptibilities (•) and magnetic
moment (o) χ per iron(III) vs. temperature T curves.
f
oxo-, alkoxo- or phenoxo- groups; describing the shortest super-
exchange pathway between the two metal centers; g α (◦) average
bridging angle, which includes the hydroxo-, alkoxo- or phenoxo-
oxygen atom; i the calculated spin exchange coupling constant ac-
cording to Gorun et al. [8];
Magnetic properties
The magnetic susceptibility and the magnetic mo-
ment of the complex are shown as a function of tem-
The selected structural and magnetic data of the ti-
perature in Fig. 3. The magnetic data was fitted using tle compound and similar complexes are listed in Ta-
the expression for molar susceptibility vs. T derived ble 4. The increase in the average Fe–O–Fe bridging
−
from the spin exchange Hamiltonian, H = −J S · S , angles (α) from 101.7 in a to 125.4 in d is connected
1
2
where J is the interaction parameter between two spin with a decrease in the antiferromagnetic exchange cou-
−
1
carriers with S = S = 5/2 as given in eq. (1).
pling constant (J) from −10.8 to −7.7 cm . d has the
largest average Fe–O–Fe bridging angle and the small-
est J constant (see Table 4). The average Fe–O bond
lengths of a, b, c, d and of the investigated compound
are almost identical, the difference of the Fe–O bond
1
2
ꢀ
ꢀ
ꢀ
χ = (1−xp)χ +2xpχ +TIP
(1)
ꢀ
C
ꢀ
ꢀ
χ =
2exp(2x)+10exp(6x)+28exp(12x)
T
˚
+
60exp(20x)+110exp(30x)ꢁ
the difference of the J constant 3.3 cm . The data
strongly indicate that variations in the Fe–O–Fe bridg-
ing angles and Fe–O bond lengths do not play a dom-
inant role in determining the degree of antiferromag-
netic exchange in these compounds.
−
1
·
ꢀ1+3exp(2x)+5exp(6x)+7exp(12x)
9exp(20x)+11exp(30x)ꢁ−1
+
In recent years several attempts were made to com-
bine the structural and magnetic properties of a large
number of Fe(III)–O(R)–Fe(III)-systems using simple
2
2
B
C
J
NLg µ
ꢀ
χ =
,
x =
,
C =
3
T
kT
k
For a satisfactory fit it was necessary to include a empirical correlations. In 1991 Gorun and Lippard
Curie-Weiss term in order to correct for a paramag- [8] established a semi-empirical correlation of mag-
netic impurity; xp is the molar amount of this mononu- netic and structural data for dinuclear oxygen-bridged
clear impurity. The temperature-independentparamag- iron(III) complexes which are double or triply bridged
−
6
3
2−
−
−
−
−
netism (TIP = 400·10 cm /mol for each iron atom) by O , OR , OPh , OH or O X (i.e. acetate, sul-
2
was also taken into account. The best-fit parameters fate, phosphate, arsenate etc.), relating the magnitude
obtained with eq. (1) by using a standard least-squares of the exchange coupling constant J with a single struc-
program were J = −11.3 cm and xp = 0.04%. An tural parameter P:
isotropic g value of 2.0 was assumed. The effective
−
1
−
J = A·exp(B·P)
(2)
magnetic moment per iron(III) at 349.3 K is 7.12 µB,
1
1
but 0.57 µB at 5 K, and decreases rapidly as the tem- Using the reported values for A (8.763 × 10 ) and
˚
perature is lowered to liquid helium temperature.
B(−12.663) and the value P = 1.956 A as found in
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9
44
C. T. Zeyrek et al. · Dinuclear Iron(III) Complex
−
1
−1
the present study, a value of Jcalc = −15.3 cm is ob- served (7 ≤ |J| ≤ 17 cm ) for other iron(III) com-
tained in fair agreement with Jobs = −11.3 cm 1.
−
plexes involving Fe O bridging units [10, 35– 38].
2 2
The magnitude of the Fe–O–Fe bridging angles and
of the Fe–O bond lengths has no noticeable influence
Conclusion
We have investigated the structural and magnetic on the exchange coupling in the Fe2L(OCH3)Cl2 com-
properties of a dinuclear Fe(III) Schiff base complex pounds. The variation of the strength of the super-
asymmetrically bridged by a phenoxo and a methoxo exchange interaction cannot be explained completely
group. The iron(III) centers are weakly antiferromag- by the structural features of dinuclear iron(III) com-
netically coupled with a J value in the range so far ob- plexes.
[
[
[
1] S. J. Lippard, Angew. Chem. 100, 353 (1988).
2] D. M. Kurtz, Chem. Rew. 90, 585 (1990).
[21] A. Elmali, Y. Elerman, I. Svoboda, H. Fuess, J. Mol.
Struct. 516, 43 (2000).
3] L. Que (Jr.), A. E. True, Progr. Inorg. Chem. 38, 97 [22] A. Elmali, Y. Elerman, I. Svoboda, Z. Naturforsch.
1990).
56b, 897 (2001).
4] S. Sheriff, W. A. Hendrickson, J. L. Smith, J. Mol. Biol. [23] A. Elmali, Y. Elerman, I. Svoboda, H. Fuess,
73 (1987) .
K. Griesar, W. Haase, Z. Naturforsch. 48b, 313 (1993).
5] R. E. Stenkamp, L. C. Sieker, L. H. Jesen, J. Am. Chem. [24] C. T. Zeyrek, A. Elmali, Y. Elerman, Z. Naturforsch. in
Soc. 106, 618 (1994).
press (2005).
6] A. C. Rosenzweig, C. A. Frederick, S. J. Lippard, [25] Enraf-Nonius diffractometer control software, Release
P. Nordlund, Nature 336, 537 (1993).
5.1, Enraf-Nonius, Delft, Netherlands (1993).
7] A. C. Rosenzweig, P. Nordlund, P. M. Takahara, C. A. [26] G. M. Sheldrick, SHELXS-97, Program for the solu-
(
[
[
[
[
[
[
2
Frederick, S. J. Lippard, J. Chem. Biol. 2, 409 (1995).
8] S. M. Gorun, S. J. Lippard, Inorg. Chem. 30, 1625
tion of crystal structures, Univ. of G o¨ ttingen, Germany
(1997).
[27] G. M. Sheldrick, SHELXL-97, Program for the refine-
ment crystal structures, Univ. of G o¨ ttingen, Germany
(1997).
(1991).
9] B. Chiari, O. Piovesena, T. Tarantelli, P. E. Zanazzi, In-
org. Chem. 21, 1396 (1982).
[
[
[
10] B. Chiari, O. Piovesena, T. Tarantelli, P. E. Zanazzi, In- [28] L. J. Farrugia, ORTEPIII. J. Appl. Crystallogr. 30, 565
org. Chem. 21, 2444 (1982).
(1997).
11] P. J. Hay, J. C. Thibealut, R. J. Hoffmann, J. Am. Chem. [29] Further information may be obtained from: Cam-
Soc. 97, 4884 (1975).
bridge Crystallographic Data Center (CCDC), 12
Union Road, Cambridge CB21EZ, UK, by quot-
ing the depository number CCDC-271906. E-mail:
deposit@ccdc.cam.
12] R. E. Norman, S. Yan, L. Que (Jr.), G. Backes, J. Ling,
J. Sanders-Loehr, J. H. Zhang, C. J. O’Connor, J. Am.
Chem. Soc. 112, 1554 (1990).
[
13] R. E. Norman, R. C. Holz, S. M e´ nage, C. J. O’Connor, [30] A. Weiss, H. Witte, Magnetochemie, Verlag Chemie,
J. H. Zhang, L. Que (Jr.), Inorg. Chem. 29, 4629
1990).
14] S. M. Gorun, S. Lippard, Inorg. Chem. 30, 1625 (1991).
Weinheim (1973).
[31] W. R. Scheidt, D. K. Geiger, R. K. Hayes, G. Lang,
J. Am. Chem. Soc. 105, 2625 (1983).
(
[
[
15] H. Weihe, H. U. G u¨ del, J. Am. Chem. Soc. 119, 6539 [32] C. T. Zeyrek, A. Elmali, Y. Elerman, Z. Naturforsch.
1997).
60b, 520 (2005).
16] A. Elmali, Y. Elerman, C. T. Zeyrek, I. Svoboda, Z. Na- [33] G. C. Percy, D. A. Thornton, J. Inorg. Nucl. Chem. 34,
turforsch. 58b, 433 (2003).
3369 (1972).
17] A. Elmali, Y. Elerman, I. Svoboda, H. Fuess, J. Mol. [34] A. Syamal, K. S. Kale, Inorg. Chem. 18, 992 (1979).
(
[
[
[
[
[
Struct. 516, 43 (2000).
18] A. Elmali, Y. Elerman, I. Svoboda, Z. Naturforsch. 56b,
[35] J. T. Wrobleski, G. J. Long. Inorg. Chem. 16, 2752
(1977).
8
97 (2001).
[36] J. A. Bertrand, P. G. Eller, Inorg. Chem. 13, 125 (1974).
19] A. Elmali, Y. Elerman, I. Svoboda, H. Fuess, K. Griesar, [37] B. Chiari, O. Piovesena, T. Tarantelli, P. E. Zanazzi, In-
W. Haase, Z. Naturforsch. 48b, 313 (1993).
org. Chem. 21, 2781 (1983).
20] A. Elmali, Y. Elerman, I. Svoboda, H. Fuess, K. Griesar, [38] R. Werner, S. Ostrovsky, K. Griesar, W. Haase, Inorg.
W. Haase, Z. Naturforsch. 49b, 365 (1994).
Chim. Acta, 326, 78 (2001).
Unauthenticated
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