Synthesis and properties of ferrocenylalkyl derivatives of indazole

Article abstract of DOI:10.1023/A:1021360704054

Ferrocenylmethylation and α-ferrocenylethylation of indazole were carried out for the first time. Both reactions afforded two isomers, which were characterized by physical and physicochemical methods, among them by X-ray diffraction analysis. 1-(α-Ferroce

Full text of DOI:10.1023/A:1021360704054

1894
Russian Chemical Bulletin, International Edition, Vol. 51, No. 10, pp. 1894—1899, October, 2002
Synthesis and properties of ferrocenylalkyl derivatives of indazole
V. V. Gumenyuk,ꢀ Z. A. Starikova, Yu. S. Nekrasov, and V. N. Babin
A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
28 ul. Vavilova, 119991 Moscow, Russian Federation.
Fax: +7 (095) 135 5085. Eꢀmail: gumen@ineos.ac.ru
Ferrocenylmethylation and αꢀferrocenylethylation of indazole were carried out for the first
time. Both reactions afforded two isomers, which were characterized by physical and physicoꢀ
chemical methods, among them by Xꢀray diffraction analysis. 1ꢀ(αꢀFerrocenylethyl)indazole
is thermally more stable than the 2ꢀsubstituted isomer. Both isomers serve as ferrocenylalkylating
agents with respect to sꢀtriazole.
Key words: ferrocenylalkylation, indazole, isomers, Xꢀray diffraction analysis.
Acidꢀcatalyzed ferrocenylalkylation performed in twoꢀ
Results and Discussion
phase media with the use of (αꢀhydroxyalkyl)ferrocenes 1
is one of the most convenient procedures for the synthesis
of αꢀferrocenylalkylazoles,1—4 including those possessing
antitumor activity and low toxicity.5—7 In the present
study, with the aim of preparing new compounds of this
series and as part of continuing studies of the properties of
polydentate ligands in ferrocenylalkylation reactions, we
synthesized 1ꢀ and 2ꢀferrocenylalkylindazoles 2a,b and
3a,b (Scheme 1) and examined some of their properties.
Under analogous conditions, the reactions involving the
sodium salt of indazole instead of indazole by itself afꢀ
forded the same reaction products.
Compounds 2a and 3a were generated in a ratio of
2 : 1, whereas compounds 2b and 3b were obtained in
virtually equal amounts. All reaction products are yellow
or orange crystalline compounds, which are soluble in
many organic solvents and insoluble in water. The meltꢀ
ing points of the 1ꢀisomers are lower than those of the
2ꢀisomers, and the melting points of ferrocenylethylꢀ
indazoles are lower than those of the correspondꢀ
ing ferrocenylmethyl derivatives (m.p. 93—95 °C and
141—143 °C for 2a and 2b, respectively; 119—120 °C and
162—163 °C for 3a and 3b, respectively). The mass specꢀ
tra of these compounds have rather intense molecular ion
peaks [M]+ at m/z = 330 (for 2a and 3a) and m/z = 316
(for 2b and 3b). The main directions of [M]+ fragmentaꢀ
tion (I = 100%) of the ferrocenylmethyl derivatives of
indazoles involve the following processes. First, this is the
simple cleavage of the metal—ligand bonds to form the
[CpFe]+ ions with m/z = 121 and the [M – Cp]+ ions
with m/z = 265 or the cleavage of the heterocycle—alkyl
bonds to form the [FcCH2]+ ions with m/z = 199 and the
[Ind]+ ions with m/z = 117. Second, this is the rearꢀ
rangement accompanied by migration of the hydrogen
atom from the heterocycle to the ferrocenyl fragment
([FcCH3]+ ion with m/z = 200) and migration of the
heterocycle to the iron atom ([CpFeInd]+ and [FeInd]+
ions with m/z = 238 and 173, respectively). For the
ferrocenylethylꢀcontaining compounds, the predominant
direction of [M]+ fragmentation involves elimination of
indazole to give vinylferrocene with m/z = 212 (I = 100%),
which is characteristic of ferrocenylethylazoles.8
Scheme 1
A comparison of the 1H NMR spectra of the resulting
compounds with each other and with the spectra of the
R = Me (a); H (b)
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1744—1748, October, 2002.
1066ꢀ5285/02/5110ꢀ1894 $27.00 © 2002 Plenum Publishing Corporation

Ferrocenylalkylꢀsubstituted indazoles
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 10, October, 2002
1895
1
Table 1. H NMR spectra of substituted indazoles (CDCl3, δ, J/Hz)
Comꢀ
pound
Н(3)
Н(4)
Н(5)
Н(6)
Н(7)
Other signals
2a
7.95 s
7.66 (d, J = 8.85) 7.03 m
7.22—7.45
5.68 (q, 1 H, CH); 4.28 s;
4.15—4.03 (m, 4 H, substituted Сp);
4.08 (s, 5 H, unsubstituted Cp);
1.91 (d, 3 H, CH3, J = 7.9)
3a
7.66 s
7.97 s
7.51 (d, J = 7.7)
7.71 (d, J = 8.0)
6.97 m
7.11 m
7.19 m
7.65 (d, J = 8.4)
5.65 (q, 1 H, CH); 4.36 m;
4.20—4.11 (m, 4 H, substitutedСp);
4.14 (s, 5 H, unsubstituted Cp);
1.95 (d, 3 H, CH3, J = 7.0)
2b
3b
7.25—7.50
5.31 (s, 2 H, CH2); 4.27, 4.10
(both s, 2 H each, substituted Сp);
4.15 (s, 5 H, unsubstituted Cp)
7.69 s
7.94
7.48 (d, J = 8.4)
6.94 m
7.10
7.15 m
7.34
7.62 (d, J = 8.7)
5.22 (s, 2 H, CH2); 4.28—4.03
(group of signals, 9 H, Cp)
1ꢀMethylꢀ
indazole9
7.71
7.56
7.59
7.68
3.95 NꢀMe
2ꢀMethylꢀ
indazole9
7.67
7.02
7.26
3.80 NꢀMe
corresponding methylindazoles provided evidence for their
close similarity (Table 1). There are no substantial differꢀ
ences in the IR spectra of these isomers as well (see the
Experimental section).
Because of this, the structures of compounds 3a and
3b were established by Xꢀray diffraction study. The crysꢀ
tals of compounds 3a and 3b were grown from a solution
in hexane at ca. –8 °C and from a solution in CDCl3 at
room temperature, respectively.
The molecular structures of compounds 3a and 3b are
shown in Figs. 1 and 2, respectively. In both compounds,
the ferrocenylalkyl group is bound to the N(2) atom.
Therefore, these compounds are 2Hꢀindazole derivatives
and would be expected to have orthoꢀquinoid structures,
which are also typical of the corresponding alkyl derivaꢀ
tives of indazole.9—11
The indazole systems in molecules 3a and 3b are subꢀ
stantially distorted. The ideal orthoꢀquinoid structures do
not occur because the bonds in the fiveꢀmembered ring
are essentially delocalized although the quinoid form in
the benzene ring is more pronounced. The C(5)—C(6)
and C(7)—C(8) bonds in 3a and the C(10)—C(11) bond
in 3b are substantially shorter than the remaining bonds
(Table 2). Hence, the superposition of the quinoid and
1Hꢀindazole forms should be ignored and only the orthoꢀ
quinoid structure with the bond delocalization in the fiveꢀ
membered heterocycle should be considered.
The crystal structure of compound 3b contains two
independent molecules located on the crystallographic
plane m resulting in disordering of the heterocycle, the
N(1) and C(8) atoms occupying close positions. One of
the independent molecules is shown in Fig. 2. Selected
bond lengths (Å) in two independent molecules are as
follows: N(1)—N(2), 1.404(14) and 1.405(9); N(2)—C(8),
1.234(17) and 1.260(14); N(1)—C(9), 1.404(14) and
1.434(10); C(8)—C(9), 1.35(2) and 1.29(2) (average valꢀ
ues are 1.40(1), 1.26(2), 1.42(1), and 1.32(2), respecꢀ
tively); C(6)—C(7), 1.499(3) and 1.498(3); C(7)—N(2),
1.474(3) and 1.474(2); C(9)—C(9A), 1.416(4) and
1.412(4); Fe—C(Cp), 2.036—2.054(2).
C(2)
C(3)
C(5)
C(1) N(2)
C(4)
C(16)
C(15)
Fe(1)
C(6)
C(7)
C(11)
C(10)
C(14)
C(17)
C(18)
C(9)
N(1)
C(8)
C(19)
C(12)
C(13)
Fig. 1. Molecular structure of compound 3a.

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Gumenyuk et al.
C(8A)
N(1A)
C(2A)
C(4A)
C(4A)
C(10A)
C(9A)
C(1A)
C(1)
C(11A)
C(7)
C(3)
C(6)
N(2)
C(11)
Fe(1)
C(4)
C(8)
N(1)
C(9)
C(5)
C(2)
C(10)
Fig. 2. Molecular structure of compound 3b.
In the orthoꢀquinoid structures containing the methyl
substituent at the N(2) atom of indazole,10,11 the
C(CH3)—N(2) and N(1)—N(2) bonds are equalized
(1.344—1.355 Å), whereas the N(1)—C(9) bonds (see
Fig. 1) are shorter than the C(3)—C(4) bonds (1.355,
1.360 and 1.389, 1.392 Å, respectively) and are identical
with those observed in 3a. It is difficult to adequately
analyze the geometric parameters of compound 3b beꢀ
cause its diazacycle in the crystal structure is disordered.
However, the N(2)—C(8) bond in compound 3b is also
shorter than the C(8)—C(9) bond. It should be noted that
the bond delocalization in the fiveꢀmembered diazacycle
is observed in all molecules with the orthoꢀquinoid form
of 2ꢀsubstituted indazoles, which are available in the Camꢀ
bridge Structural Database (CSD).12
angles between the planes of the indazole and Cp fragꢀ
ments are 109.2 in 3a and 112.7 and 109.4° in 3b. The
geometry of the Cp ring in compound 3a is characterized
by an elongation of the C(11)—C(10) and C(10)—C(14)
bonds (average, 1.423 Å) compared to the remaining
bonds in the ring (1.399—1.414 Å) and also by a decrease
in the C(11)—C(10)—C(14) bond angle to 107.1(2)° (the
remaining angles are 108.3°). In molecule 3b, an analoꢀ
gous elongation of the bonds is much less pronounced.
The exocyclic C(Cp)—C(1 or 7) bond length (1.505(3) Å
in 3a and 1.498(3) Å in 3b) is close to the standard
C(Cp)—Csp3 bond length.
The N(2)—C(1) bond in compound 3a (1.483(3) Å) is
somewhat longer than the average value (1.469 Å)13 typiꢀ
cal of the Csp3—N bonds with the participation of the
threeꢀcoordinate nitrogen atom. In compound 3b, this
bond length is close to the standard value (1.474 Å).
Analysis of the C—C and C—N bond lengths in the
Fc—C(R1,R2)—N(R3R4) fragments of compounds availꢀ
able in the CSD demonstrated that the C—N bond length
depends primarily on the nature of the R3R4 substituents,
whereas the R1,R2 substituents have virtually no effect on
this bond. Thus, the bond lengths between the C atom
and the NHPh, NMe2 (or N(Alk)2), and N=CHPh groups
are 1.451—1.454 Å, 1.459—1.472 Å, and 1.472 Å, reꢀ
spectively. In the ferrocenylalkyl derivatives of nucleic
bases, the C—N bond lengths are in the range of
1.470—1.485 Å 14—16 and are larger than the value averꢀ
aged over 52 different N(9)ꢀsubstituted adenines devoid
of the Fc substituent (1.459 Å).
In both molecules, the indazole fragment is planar
and the exocyclic carbon atom (C(1) in 3a and C(7)
in 3b) lies in the plane of the fragment. The dihedral
Table 2. Selected bond lengths (d) and bond angles (ω) in comꢀ
pound 3a
Bond
d/Å
Angle
ω/deg
Fe(1)—C(Cp) 2.025—
2.050(3)
C(3)—N(2)—N(1)
C(3)—N(2)—C(1)
N(1)—N(2)—C(1)
N(2)—N(1)—C(9)
N(2)—C(3)—C(4)
C(3)—C(4)—C(9)
C(3)—C(4)—C(5)
C(9)—C(4)—C(5)
C(6)—C(5)—C(4)
C(5)—C(6)—C(7)
C(8)—C(7)—C(6)
C(7)—C(8)—C(9)
N(1)—C(9)—C(4)
N(1)—C(9)—C(8)
C(4)—C(9)—C(8)
113.7(2)
128.4(2)
117.9(2)
103.5(2)
107.0(2)
104.2(2)
135.9(3)
119.9(2)
117.7(3)
122.0(3)
122.3(3)
117.4(3)
111.6(2)
127.7(3)
120.7(2)
N(2)—C(3)
C(3)—C(4)
C(4)—C(9)
C(4)—C(5)
C(5)—C(6)
C(6)—C(7)
C(7)—C(8)
C(8)—C(9)
C(9)—N(1)
N(1)—N(2)
N(2)—C(1)
C(1)—C(10)
1.337(3)
1.383(3)
1.412(4)
1.427(4)
1.362(5)
1.396(5)
1.363(5)
1.417(4)
1.352(3)
1.351(2)
1.483(3)
1.505(3)
An elongation of the C—N bond in ferrocenylalkyl
derivatives of nucleic bases is indicative of its lability,
which made it possible to use these compounds as
ferrocenylalkylating agents.3,14,16 It is also known that
2ꢀacylindazoles are good acylating agents9 and can unꢀ
dergo isomerization to give 1ꢀacylindazoles. In this conꢀ
nection, we studied thermal stability of compounds 2a,b
and 3a,b and examined the possibility of the transfer of
the ferrocenylalkyl group from these compounds to anꢀ
other substrate. It was found that refluxing of 2ꢀisomers
3a,b in a tetrahydrofuran solution in air for 15 h (interꢀ
C(10)—C(14) 1.420(3)
C(10)—C(11) 1.426(3)
C(14)—C(10)—C(11) 107.1(2)

Ferrocenylalkylꢀsubstituted indazoles
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 10, October, 2002
1897
Scheme 3
ruption for 12 h) led to the partial transformation of these
isomers into the 1ꢀisomers. 2ꢀFerrocenylmethylindazole
appeared to be more stable than its αꢀethyl analog and its
conversion was only 5—10%, whereas 2ꢀ(αꢀferrocenylꢀ
ethyl)indazole was converted by almost 50%. In addition,
the latter reaction afforded a small amount of vinylꢀ
ferrocene and its dimer (Scheme 2). It should be noted
that under the same conditions, solutions of 1ꢀisomers
2a,b did not undergo noticeable changes during the same
period of time.
Scheme 2
R = Me (a); H (b)
Refluxing of methanolic solutions of each of the four
compounds, which were acidified with concentrated HCl,
in the presence of 1,2,4ꢀtriazole for 2.5 h gave rise to the
corresponding Nꢀferrocenylalkylꢀ1,2,4ꢀtriazoles 4a,b with
the molecular masses [M]+ with m/z = 281 and 267, reꢀ
spectively (Scheme 3). In these four reactions, the yields
of compounds 4a,b differed only slightly (25—35% for 2a
and 3a; 20—25% for 2b and 3b). Ferrocenylalkylation of
triazole was accompanied by the transformation of 2ꢀsubꢀ
stutited indazole derivatives 3a,b into 1ꢀferrocenylalkylꢀ
indazoles 2a,b.
αꢀFerrocenylethylation of sꢀtriazole also gave rise to
vinylferrocene, its dimer, and trimer, whereas ferrocenylꢀ
methylation afforded a small amount of unidentified deꢀ
composition products. It can be suggested that αꢀferroꢀ
cenylalkylation of sꢀtriazole is the reversible reaction. This
conclusion is evidenced by the fact that 1ꢀNꢀ(αꢀferroꢀ
cenylethyl)ꢀ1,2,4ꢀtriazole (4a) prepared independently
(according to the reaction analogous to that presented in
Scheme 1) readily performed ferrocenylethylation of
indazole under the aboveꢀmentioned conditions. In this
reaction, 1ꢀ(αꢀferrocenylethyl)indazole (2a) was selecꢀ
tively generated.
3a compared to that in 3b correlates with a decrease in its
thermal stability, but has a lesser effect on the ferroꢀ
cenylalkylating ability.
Experimental
The IR spectra were recorded on a URꢀ20 spectrometer
(Carl Zeiss) in KBr pellets. The mass spectra (EI) were meaꢀ
sured on an MSꢀ890 instrument (Kratos) with direct inlet of
the sample; the temperature of the ionization chamber was
200—220 °C; the energy of ionizing electrons was 70 eV.
The 1H NMR spectra were measured at ∼20 °C on a Bruker
WPꢀ200ꢀSY instrument operating at 200.13 MHz. Chromatoꢀ
graphy was carried out with the use of aluminum oxide
(Brockmann activity II); pH of a 10% aqueous solution was
9—10. Indazole was prepared according to a known procedure.17
1ꢀ and 2ꢀ(αꢀFerrocenylethyl)indazoles (2a and 3a). A 38%
aqueous solution of fluoroboric acid (2.13 mL) was added with
vigorous stirring to a mixture of indazole (1.18 g, 10 mmol) and
αꢀhydroxyethylferrocene (2.30 g, 10 mmol) in chloroform
(10 mL). The reaction mixture was stirred for 5 min. Then
distilled water (100 mL) was added and the acid was neutralized
with aqueous ammonia. The reaction mixture was treated with
ether (100 mL), the organic layer was separated, and the solvent
was evaporated in air. The solid residue was dissolved in chloroꢀ
form and chromatographed on Al2O3. The darkꢀyellow band
Therefore, an elongation of the C—N bond between
the indazole fragment and the alkyl group in compound

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Gumenyuk et al.
was eluted with benzene. After removal of the solvent, 1ꢀ(αꢀferroꢀ
cenylethyl)indazole (2a) was obtained in a yield of 2.05 g (62%),
m.p. 93—95 °C. IR, ν/cm–1: ferrocene: 492, 518, 820, 842, 1005
(shoulder), 1024, 1110, 1420, 3070, and 3110; heterocycle: 912,
1185, 1478, 1508, 1627. Found (%): C, 68.96; H, 5.40; N, 8.19.
C19H18N2Fe. Calculated (%): C, 69.09; H, 5.45; N, 8.49. The
paleꢀyellow band was eluted with chloroform. After removal of
the solvent, 2ꢀ(αꢀferrocenylethyl)indazole (3a) was obtained in
a yield of 0.96 g (29%), m.p. 119—120 °C. Compound 3a was
recrystallized from hexane. IR, ν/cm–1: ferrocene: 480, 508,
826, 1005, 1110, 1391, 3110, and 3135 (br); heterocycle: 911,
1141, 1152, 1458, 1478, and 1638.
1ꢀ and 2ꢀFerrocenylmethylindazoles (2b and 3b) were preꢀ
pared from indazole (3 mmol) and ferrocenylmethanol (3 mmol)
according to the aboveꢀdescribed procedure. The yield of 1ꢀferroꢀ
cenylmethylindazole (2b) was 0.44 g (46%), m.p. 141—143 °C.
The yield of 2ꢀferrocenylmethylindazole (3b) was 0.39 g (41%),
m.p. 162—163 °C. IR of 2b, ν/cm–1: ferrocene: 488, 507, 830,
843, 1012, 1110, 1425, 2937, and 2957; heterocycle: 915, 1172,
1476, 1510, and 1627. IR of 3b, ν/cm–1: ferrocene: 480—505 (br),
830, 1010, 1114, 1393, 3070, and 3085; heterocycle: 915, 1180,
1476, 1525, and 1638. Found (%): C, 68.27; H, 5.30; N, 8.86.
C18H16N2Fe. Calculated: C, 68.35; H, 5.06; N, 8.86.
compounds). After cooling, thinꢀlayer chromatography of the
reactions mixiture on Al2O3 was carried out to isolate vinylꢀ
ferrocene18 ([M]+ m/z = 212, m.p. 49—51 °C) along with its
dimer ([M]+ m/z = 424) for compound 3a using hexane as the
eluent, compound 2a (40—45%) using dimethyl ether as the
eluent, and compound 3a (50%) using chloroform as the eluent.
In the case of indazole 2a, no changes were observed.
Xꢀray diffraction study of compound 3a was performed on an
automated EnrafꢀNonius CAD4 diffractometer (MoꢀKα radiaꢀ
tion, graphite monochromator, θ
= 25°) at ∼20 °C. Paleꢀ
max
yellow transparent crystals of C19H18FeN2 (M = 330.20) are
monoclinic, a = 12.742(3) Å, b = 9.895(2) Å, c = 12.764(3) Å,
β = 106.78(3)°, V = 1540.8(5) Å3, space group P21/n, Z = 4,
dcalc = 1.423 g cm–3. A total of 2704 independent reflections
were measured (Rint = 0.0440). The structure was solved by
direct methods and refined by the leastꢀsquares method based
on F2 with anisotropic thermal parameters for nonhydrogen
hkl
atoms and isotropic thermal parameters for hydrogen atoms,
whose positions were revealed from difference electron density
syntheses. The final reliability factors were as follows: R1 = 0.0461
(calculated based on Fhkl for 2202 reflections with I > 2σ(I )),
wR2 = 0.0990 (calculated based on F 2 for all independent
hkl
reflections), 271 refinable parameters.
Reactions of ferrocenylethylindazoles 2a and 3a with 1,2,4ꢀtriꢀ
azole. Indazole 2a or 3a (0.07 g, 0.2 mmol) was dissolved in
ethanol on heating. Then a solution of 1,2,4ꢀtriazole (0.01 g,
0.2 mmol) in H2O (1.5 mL) and concentrated HCl (0.09 mL)
was added. The reaction mixture was refluxed for 2.5 h, cooled,
neutralized with aqueous ammonia, and extracted with dimethyl
ether. The organic layer was separated. Thinꢀlayer chromatogꢀ
raphy on silica gel afforded vinylferrocene along with its dimer
and trimer ([M+] m/z = 212, 424, and 636) using hexane as the
eluent; compound 2a or the mixture 2a+3a ([M+] m/z = 330)
using benzene as the eluent; and 1ꢀ(αꢀferrocenylethyl)ꢀ1,2,4ꢀ
triazole14 (4a) ([M+] m/z = 281) using methanol as the eluent.
1H NMR of 4a (d6ꢀacetone), δ: 8.28 and 7.75 (both s, 1 H each,
C(3)H and C(5)H); 5.45 (m, 1 H, CH); 4.18 (s, 5 H, unꢀ
substituted Cp ring); 3.80—4.40 (group of signals, 4 H, substiꢀ
tuted Cp ring); 1.70 (d, 3 H, CH3, J = 5.8 Hz).
Reaction of ferrocenylethyltriazole 4a with indazole.
1ꢀ(αꢀFerrocenylethyl)ꢀ1,2,4ꢀtriazole (4a) (0.06 g, 0.2 mmol),
which was prepared from sꢀtriazole and αꢀhydroxyethylferrocene
analogously to ferrocenylethylindazoles, was dissolved in methaꢀ
nol on heating. Then a solution of indazole (0.02 g, 0.2 mmol) in
H2O (1.5 mL) and concentrated HCl (0.09 mL) was added. The
reaction mixture was refluxed for 2.5 h, cooled, neutralized with
aqueous ammonia, and extracted with dimethyl ether. The orꢀ
ganic layer was separated. According to the massꢀspectrometric
data, the mixture contained vinylferrocene along with its dimer
([M+] m/z = 212 and 424), ferrocenylethylindazole ([M+]
m/z = 330) as the major compound, and a small amount of
1ꢀNꢀ(αꢀferrocenylethyl)ꢀ1,2,4ꢀtriazole14 4a ([M+] m/z = 281).
A comparative chromatogram on a Silufol plate showed the
presence of only 1ꢀ(αꢀferrocenylethylindazole) (2a). Isomer 3a
was absent.
Xꢀray diffraction study of compound 3b. Paleꢀyellow needleꢀ
like crystals of 3b (C18H16FeN2 M = 316.18) are monoclinic, at
110 K a = 23.260(5) Å, b = 10.313(2) Å, c = 13.023(3) Å, β =
117.302(4)°, V = 2776(1) Å3, space group C2/m, Z = 8, dcalc
=
1.513 g cm–3. A total of 11705 reflections were collected on
a Bruker SMART 1000 CCD area detector diffractometer
(λMoꢀKα radiation, 2θ
= 60.08°) at 110 K from a single
max
crystal of dimensions 0.1×0.2×0.5 mm. The data were proꢀ
cessed with the use of the SAINT19 and SADABS20 programs
(Tmax = 0.928, Tmin = 0.164) to obtain 4199 independent reflecꢀ
tions (Rint = 0.0454), which were used for the solution and
refinement of the structure. The structure was solved by direct
methods. The nonhydrogen atoms were located from difference
electron density syntheses and refined anisotropically based
on F 2hkl. The positions of all hydrogen atoms were revealed and
refined isotropically, except for the H atoms at the disordered
nitrogen atoms in the indazole rings, which were refined with
fixed Biso = 0.5. The final reliability factors were as follows:
R1 = 0.0429 (calculated based on Fhkl for 3556 reflections with
I > 2σ(I )), wR2 = 0.1213 (calculated based on F 2 for all
hkl
4199 reflections), GOOF = 1.032; 291 refinable parameters.
All calculations were carried out with the use of the
SHELXTL PLUS 5 program package.21 The complete Xꢀray
diffraction data were deposited with the Cambridge Structural
Database.
This study was financially supported by the Russian
Foundation for Basic Research (Project Nos. 00ꢀ03ꢀ32807
and 99ꢀ07ꢀ90133).
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Received May 5, 2002;
in revised form July 9, 2002