Synthesis and structures of iron(III) complexes based on azo derivatives of 5-oxo- and 5-thioxopyrazole

Article abstract of DOI:10.1023/B:RUCB.0000012379.96546.bb

New potentially tridentate ligands, viz., 3-methyl-1-phenyl-4-(quinolin-8- ylhydrazono)pyrazol-5(1H)-one and 3-methyl-1-phenyl-4-(quinolin-8-ylhydrazono) pyrazole-5(1H)-thione (LH), and their complexes with Fe^III were synthesized. The structure

Full text of DOI:10.1023/B:RUCB.0000012379.96546.bb

Russian Chemical Bulletin, International Edition, Vol. 52, No. 11, pp. 2523—2526, November, 2003
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Brief Communications
Synthesis and structures of iron(III) complexes
based on azo derivatives of 5ꢀoxoꢀ and 5ꢀthioxopyrazole
a
†
a
a
b
A. I. Uraev,a A. L. Nivorozhkin, V. P. Kurbatov, L. N. Divaeva, M. S. Korobov, K. A. Lyssenko,
ꢀ
M. Yu. Antipin,b D. A. Pavlenko,a and A. D. Garnovskiia
aRostov State University,
194/2 prosp. Stachki, 344090 RostovꢀonꢀDon, Russian Federation.
Fax: +7 (863 2) 43 4667. Eꢀmail: garn@ipoc.rsu.ru
bA. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
28 ul. Vavilova, 119991 Moscow, Russian Federation.
Fax: +7 (095) 135 5085
New potentially tridentate ligands, viz., 3ꢀmethylꢀ1ꢀphenylꢀ4ꢀ(quinolinꢀ8ꢀylhydrꢀ
azono)pyrazolꢀ5(1H )ꢀone and 3ꢀmethylꢀ1ꢀphenylꢀ4ꢀ(quinolinꢀ8ꢀylhydrazono)pyrazoleꢀ
5(1H )ꢀthione (LH), and their complexes with FeIII were synthesized. The structures of the
ligands and metal chelates (FeL2A; A = ClO4 or FeCl4) were studied by 1H NMR spectroscopy
and magnetochemistry. The FeL2A complex (A = FeCl4) was investigated by Xꢀray diffraction.
These lowꢀspin complexes have pseudooctahedral structures with the N4X2 ligand environment
(X = O or S).
Key words: nitrile hydratase, azo compounds, iron(III) chelates, Xꢀray diffraction analysis,
NMR spectroscopy, magnetochemistry.
Iron(III) chelates in a nitrogen chalcogen ligand enviꢀ
ronment can serve as models of the active center of nitrile
hydratase.1—3
Earlier,4—6 we have synthesized and studied enamines
of type 1 and iron(III) chelates of type 2, which reproduce
certain spectroscopic and structural parameters of nitrile
hydratase. As part of our continuing studies, we syntheꢀ
sized new tridentate ligands of type 3 and iron chelates 4
based on these ligands.
Ligand 3a was synthesized by the reaction of 3ꢀmeꢀ
thylꢀ1ꢀphenylpyrazolꢀ5ꢀone with a quinolinꢀ8ꢀdiazonium
salt using a modified procedure described earlier7—9
(Scheme 1). Like 4ꢀarylazo derivatives of pyrazolone,9
compound 3a reacts with POCl3 to give a 5ꢀchloroꢀsubꢀ
stituted product 5. The reaction of the latter with Na2S
affords 3ꢀmethylꢀ1ꢀphenylꢀ4ꢀ(quinolinꢀ8ꢀylhydrazoꢀ
no)pyrazoleꢀ5(1H )ꢀthione (3b) (see Scheme 1). Taking
into account the results of studies of enamines 1 by Xꢀray
1
diffraction analysis and H NMR spectroscopy10 and by
† Deceased.
analogy with the data published in the literature,11—13 we
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2386—2389, November, 2003.
1066ꢀ5285/03/5211ꢀ2523 $25.00 © 2003 Plenum Publishing Corporation

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Uraev et al.
1a, 3a
1b, 3b
1c
2a, 4a
2b, 4b
2c, 4c
2d, 4d
2e
2f
X
A
O
—
S
—
Se
—
O
FeCl4
O
ClO4
S
FeCl4
S
ClO4
Se
FeCl4
Se
ClO4
assigned the oxoꢀ and thioxohydrazone structures to
ligands 3.
respectively. The folding angles of the fiveꢀ and sixꢀmemꢀ
bered rings are 13° and 24°, respectively. The presence of
two fiveꢀmembered metallocycles, which are sterically
more hindered than sixꢀmembered rings, leads to only
slight distortions of the octahedral symmetry of the coorꢀ
dination polyhedron (the corresponding bond angles deꢀ
viate from 90° within 7.5°). The structure of metal chelate
4c is similar to that of complex 2c studied by us earlier.4,5
For example, the Fe—S distances in 4c (2.207(1) and
2.209(1) Å) are only slightly shortened compared to those
in 2c (2.227(2) and 2.230(2) Å).4,5 The Fe—Nazo bond
length in 4c (1.939(3) Å (1.946(3) Å)) is smaller, on the
average, by 0.03 Å than that in metal chelate 2c (Y = CH),
whereas the Fe—Nqin distance (2.012(3) Å (2.021(3) Å))
is, on the contrary, larger, on the average, by 0.015 Å.
Taking into account that iron(III) chelates with the
NOꢀligand environment are generally highꢀspin or beꢀ
long to compounds exhibiting the spinꢀequilibrium beꢀ
havior,3,14,15 the magnetic moment of complex 4b in the
solid state (µeff = 1.98 µB) is unexpectedly low. The state
with S = 1/2 of the iron(III) ion in the cation is typical of
sulfurꢀcontaining derivatives of 4d (µeff = 2.17 µB). The
unusually high effective magnetic moments of compounds
4a and 4c (µeff = 6.17 and 6.20 µB, respectively) are attribꢀ
uted to the combined contribution of the lowꢀspin FeIII
cation (S = 1/2) and the highꢀspin FeIII anion FeCl4
(S = 5/2). The effective magnetic moments of complexes
4b,d measured in CDCl3 and DMSO solutions by the
Evans method16 are 2.16 µB (CDCl3) and 2.36 µB (DMSO)
for 4b and 2.16 µB (CDCl3) and 2.17 µB (DMSO) for 4d.
The fact that the magnetic moments of metal chelates
Scheme 1
Iron(III) complexes 4a—d were synthesized by the
direct reaction of compound 3a,b (1 equiv.) with
Fe(ClO4)3•nH2O or FeCl3•6H2O (1 equiv.) in EtOH.
Complexes 4a,c were satisfactorily characterized by elꢀ
emental analysis data.
According to the results of Xꢀray diffraction analysis,
the iron atom in the cation of complex 4c (Fig. 1) is in an
N4S2ꢀtype pseudooctahedral environment with the cis
arrangement of the sulfur atoms (S(1)—Fe—S(1´),
–
94.36(4)°). Complex 4c contains FeCl4 as the anion.
The ligands coordinated to the iron ion are in the orꢀ
thogonal orientation with respect to each other (the diꢀ
hedral angle is 90.1°). The principal geometric paramꢀ
eters of the ligands are virtually identical. The sixꢀmemꢀ
bered and fiveꢀmembered metallocycles adopt the chair
and envelope conformations with the metal atoms deviatꢀ
ing from the planes of the rings by 0.49 and 0.34 Å,

Synthesis and sructures of iron(III) complexes
Russ.Chem.Bull., Int.Ed., Vol. 52, No. 11, November, 2003 2525
C(10´)
C(3´)
N(4´)
C(17´)
C(2´)
C(16´)
C(15´)
N(1´)
C(18´)
N(5´)
C(4´)
C(1´)
C(5´)
C(6´)
N(2´)
C(11)
C(14´)
C(19´)
C(12)
C(7´)
C(9´)
S(1´)
N(3)
Fe(1)
C(8´)
S(1)
C(8)
C(9)
C(13)
C(7)
N(3´)
C(13´)
C(12´)
C(1)
C(4)
C(14)
C(19)
N(5)
C(11´)
N(2)
C(6)
C(18)
C(15)
C(2)
C(3)
C(5)
N(1)
N(4)
C(16)
C(17)
C(10)
Fig. 1. Overall view of cation 4c.
Smart 1000 CCD diffractometer at 110 K (MoꢀKα radiation,
graphite monochromator, ω scanning technique, 2θ = 56°),
4b,d determined in the crystalline state are similar to those
measured in solutions indicates that these complexes reꢀ
tain the magnetic properties and, apparently, their strucꢀ
tures in solutions.
max
and 10176 observed reflections (Rint = 0.0421) were used in
calculations. The structure was solved by direct methods and
refined by the fullꢀmatrix leastꢀsquares method based on F 2
with anisotropic and isotropic thermal parameters. The hydroꢀ
gen atoms were revealed from difference electron density synꢀ
theses and refined using the riding model. The final reliabilꢀ
ity factors were as follows: wR2 = 0.1243, GOOF = 0.971
(R1 = 0.0564 for 5101 reflections with I > 2σ(I )). All calculaꢀ
tions were carried out using the SHELXTL PLUS program
package.
3ꢀMethylꢀ1ꢀphenylꢀ4ꢀ(quinolinꢀ8ꢀylhydrazono)pyrazolꢀ
5(1H )ꢀone (3a) was synthesized according to a procedure analoꢀ
gous to that described earlier.7—9 8ꢀAminoquinoline (0.72 g,
5 mmol) was dissolved in concentrated HCl (6 mL) and water
(10 mL). The reaction solution was cooled to 0—5 °C and then a
solution of NaNO2 (0.42 g, 6 mmol) in water (2 mL) was added
dropwise. The reaction mixture was kept at this temperature for
20 min. The resulting solution of the diazonium salt was added
with thorough stirring to a solution of 3ꢀmethylꢀ1ꢀphenylpyrazolꢀ
5ꢀone (0.87 g, 5 mmol) in EtOH cooled with ice. After 30 min,
the reaction mixture was neutralized with NaHCO3 to pH 7—8.
The precipitate that formed was filtered off and washed with
water. The reaction product was recrystallized from toluene.
The yield was 1 g (60%). Found (%): C, 69.35; H, 5.01; N, 21.21.
Experimental
The 1H NMR spectra were recorded on a Varian UNITYꢀ300
spectrometer (300 MHz) in CDCl3. The magnetic moments of
the complexes in the crystalline state at 299 K were measured on
an instrument designed at the Rostov State University17 using
the Faraday method. The effective magnetic moments were calꢀ
culated by the formula µ = (8λ Т)1/2, where λ is the molar
eff
m
m
magnetic susceptibility taking into account the Pascal magnetic
corrections. The magnetic moments in CDCl3 and DMSO soluꢀ
tions were determined using the Evans method16 on a Varian
UNITYꢀ300 spectrometer. 8ꢀAminoquinoline (Aldrich) and
3ꢀmethylꢀ1ꢀphenylpyrazolꢀ5ꢀone (Lankaster) were used. Since
compounds 4b,d contain the perchlorate anion and are potenꢀ
tially explosive, they were not analyzed.
Xꢀray diffraction study of complex 4c. Crystals are triclinic,
at 110 K: a = 12.200(1), b = 12.253(1), c = 16.613(2) Å,
α = 75.510(2)°, β = 70.576(2)°, γ = 65.461(2)°, V = 2112.2(4) Å3,
–
dcalc = 1.615 g cm–1, space group P1, Z = 2. The intensiꢀ
ties of 19968 reflections were measured on an automated

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Uraev et al.
C19H15N5O. Calculated (%): C, 69.29; H, 4.59; N, 21.26.
1H NMR (DMSOꢀd6), δ: 2.30 (s, 3 H, Me); 7.20—9.00 (m,
11 H, C6H5, C9H6N); 14.50 (s, 1 H, OH or NH).
32538), the Federal Program for the Support of Leading
Scientific Schools of the Russian Foundation (Project
NShꢀ945.2003.3), and the Program "Russian Universiꢀ
ties" (Grant UR.05.01.006).
(5ꢀChloroꢀ3ꢀmethylꢀ1ꢀphenylꢀ1Hꢀpyrazolꢀ4ꢀyl)(quinolinꢀ8ꢀ
yl)diazene (5) was prepared according to a procedure analogous
to that describe earlier.9 Compound 3a (3.29 g, 0.01 mol) was
added to POCl3 (25 mL, 0.27 mmol) and the resulting mixture
was refluxed for 12 h. Then the major portion of POCl3 was
distilled off in vacuo. The remaining portion was poured onto ice
and kept for 12 h. The precipitate that formed was filtered off,
washed with water, and recrystallized from a toluene—AcOH
mixture. The yield was 2.61 g (75%). Found (%): C, 65.57;
H, 4.19; N, 20.10. C19H14ClN5. Calculated (%): C, 65.61; H,
References
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1
4.06; N, 20.14. H NMR (DMSOꢀd6), δ: 2.70 (s, 3 H, Me);
7.40—9.20 (m, 11 H, C6H5, C9H6N).
3ꢀMethylꢀ1ꢀphenylꢀ4ꢀ(quinolinꢀ8ꢀylhydrazono)pyrazoleꢀ
5(1H )ꢀthione (3b). Derivative 5 (3.48 g, 0.01 mol) was added to
a suspension of Na2S•9H2O (3.6 g, 0.015 mol) in DMSO
(20 mL). The reaction mixture was stirred at 60 °C for 4 h,
cooled to 20 °C, diluted with water (200 mL), and extracted
with Et2O. The aqueous layer was acidified with 10% HCl
to pH 7. The precipitate that formed was filtered off and recrysꢀ
tallized from toluene. The yield was 1 g (29%). Found (%):
C, 65.97; H, 4.30; N, 20.25. C19H15N5S. Calculated (%):
C, 66.07; H, 4.38; N, 20.27. 1H NMR (CDCl3), δ: 2.45 (s, 3 H,
Me); 7.20—9.00 (m, 11 H, C6H5, C9H6N); 17.50 (s, 1 H,
SH or NH).
Iron complexes 4 were prepared by heating an ethanolic
solution of the corresponding azo derivative 3 (1 mmol) and
Fe(ClO4)3•nH2O or FeCl3•6H2O (1 mmol) for 30—40 min.
The precipitates that formed were filtered off, washed with EtOH,
and recrystallized from toluene or a CH2Cl2—Et2O mixture.
The yields were 50—65%.
{Bis[3ꢀmethylꢀ1ꢀphenylꢀ4ꢀ(quinolinꢀ8ꢀyldiazenyl)ꢀ5ꢀpyrꢀ
azolato]iron(III)} tetrachloroferrate (4a). The yield was 0.591 g
(65%). Found (%): C, 49.97; H, 3.30; N, 15.20.
C38H28Cl4N10O2Fe2. Calculated (%): C, 50.14; H, 3.10;
11. J. A. Connor, R. J. Kennedy, H. M. Daves, M. B.
Hursthouse, and N. P. Walker, J. Chem. Soc., Perkin Trans. 2,
1990, 203.
N, 15.39. µeff = 6.17 µ .
B
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16. D. V. Evans, J. Chem. Soc., 1959, 2003.
{Bis[3ꢀmethylꢀ1ꢀphenylꢀ4ꢀ(quinolinꢀ8ꢀyldiazenyl)ꢀ5ꢀ
pyrazolato]iron(III)} perchlorate (4b). The yield was 0.44 g (55%),
µ
= 1.98 µB (solid), 2.36 µ (DMSOꢀd6), 2.16 µB (CDCl3).
eff
B
{Bis[3ꢀmethylꢀ1ꢀphenylꢀ4ꢀ(quinolinꢀ8ꢀyldiazenyl)ꢀ5ꢀ
pyrazolethiolato]iron(III)} tetrachloroferrate (4c). The yield was
0.57 g (60%). Found (%): C, 48.27; H, 2.70; N, 15.25.
C38H28Cl4N10S2Fe2. Calculated (%): C, 48.43; H, 2.99;
N, 14.86. µeff = 6.20 µ .
B
{Bis[3ꢀmethylꢀ1ꢀphenylꢀ4ꢀ(quinolinꢀ8ꢀyldiazenyl)ꢀ5ꢀ
pyrazolethiolato]iron(III)} perchlorate (4d). The yield was
0.406 g (50%). µ = 2.17 µ (solid), 2.16 µ (CDCl3), 2.17 µ
17. V. P. Kurbatov, A. V. Khokhlov, A. D. Garnovskii, O. A.
Osipov, and L. A. Khukhlachieva, Koord. Khim., 1979, 5,
351 [Sov. J. Coord. Chem., 1979, 5 (Engl. Transl.)].
eff
B
B
B
(DMSOꢀd6).
This study was financially supported by the Russian
Foundation for Basic Research (Project No. 01ꢀ03ꢀ
Received February 14, 2003;
in revised form September 29, 2003