Highly fluorinated aryl-substituted tris(indazolyl)borate thallium complexes: Diverse regiochemistry at the B-N bond

Article abstract of DOI:10.1021/ic202125c

The synthesis and characterization (mainly by ¹⁹F NMR and X-ray diffraction) of highly fluorinated aryl-4,5,6,7-tetrafluoroindazoles and their corresponding thallium hydrotris(indazolyl)borate complexes are reported [aryl = phenyl, pentafluorophenyl, 3,5-dimethylphenyl, 3,5-bis(trifluoromethyl)phenyl]. Thanks to N-H???N hydrogen bonds, the indazoles crystallize as dimers that pack differently depending on the nature of the aryl group. The thallium hydrotris(indazolyl)borate complexes Tl[Fn-Tp^4Bo,3aryl] resulting from the reaction of aryl-4,5,6,7-tetrafluoroindazoles [aryl = phenyl, 3,5-dimethylphenyl, 3,5-bis(trifluoromethyl)phenyl] with thallium borohydride adopt overall C_3v symmetry with the indazolyl groups bound to boron via their N-1 nitrogen in a conventional manner. When the perfluorinated pentaphenyl-4,5,6,7-tetrafluoroindazole is reacted with thallium borohydride, a single regioisomer of C_s symmetry having one indazolyl ring bound to boron via its N-2 nitrogen, TlHB(3-pentafluorophenyl-4,5,6,7-tetrafluoroindazol- 1-yl)₂(3-pentafluorophenyl-4,5,6,7-tetrafluoroindazol-2-yl) Tl[F27-Tp^(4Bo,3C6F5)*], is obtained for the first time. Surprisingly, the perfluorinated dihydrobis(indazolyl)borate complex Tl[F ₁₈-Bp^3Bo,3C6F5], an intermediate on the way to the hydrotris(indazolyl)borate complex, has C_s symmetry with two indazolyl rings bound to boron via N-2. The distortion of the coordination sphere around Tl and the arrangement of the complexes in the crystal are discussed.

Full text of DOI:10.1021/ic202125c

Article
pubs.acs.org/IC
Highly Fluorinated Aryl-Substituted Tris(indazolyl)borate Thallium
Complexes: Diverse Regiochemistry at the B−N Bond
Wilfried-Solo Ojo,†,‡ Kane Jacob,†,‡ Emmanuelle Despagnet-Ayoub,†,‡ Bianca K. Munoz,†,‡
̃
Sergio Gonell,†,‡ Laure Vendier,†,‡ Viet-Hoang Nguyen,†,‡ and Michel Etienne*,†,‡
†CNRS, LCC (Laboratoire de Chimie de Coordination), 205 route de Narbonne, F-31077 Toulouse, France
‡Universite
́
de Toulouse, UPS, INPT, LCC, F-31077 Toulouse, France
S
* Supporting Information
ABSTRACT: The synthesis and characterization (mainly by 19F NMR and X-ray
diffraction) of highly fluorinated aryl-4,5,6,7-tetrafluoroindazoles and their correspond-
ing thallium hydrotris(indazolyl)borate complexes are reported [aryl = phenyl,
pentafluorophenyl, 3,5-dimethylphenyl, 3,5-bis(trifluoromethyl)phenyl]. Thanks to
N−H···N hydrogen bonds, the indazoles crystallize as dimers that pack differently
depending on the nature of the aryl group. The thallium hydrotris(indazolyl)borate
complexes Tl[Fn-Tp4Bo,3aryl] resulting from the reaction of aryl-4,5,6,7-tetrafluoroinda-
zoles [aryl = phenyl, 3,5-dimethylphenyl, 3,5-bis(trifluoromethyl)phenyl] with thallium
borohydride adopt overall C3v symmetry with the indazolyl groups bound to boron via
their N-1 nitrogen in a conventional manner. When the perfluorinated pentaphenyl-
4,5,6,7-tetrafluoroindazole is reacted with thallium borohydride, a single regioisomer of
Cs symmetry having one indazolyl ring bound to boron via its N-2 nitrogen, TlHB(3-
pentafluorophenyl-4,5,6,7-tetrafluoroindazol-1-yl)2(3-pentafluorophenyl-4,5,6,7-tetra-
fluoroindazol-2-yl) Tl[F27-Tp(4Bo,3C6F5)*], is obtained for the first time. Surprisingly, the
perfluorinated dihydrobis(indazolyl)borate complex Tl[F18-Bp3Bo,3C6F5], an intermediate on the way to the hydrotris(indazolyl)-
borate complex, has Cs symmetry with two indazolyl rings bound to boron via N-2. The distortion of the coordination sphere
around Tl and the arrangement of the complexes in the crystal are discussed.
instead of b (Tp3Bo) (Chart 1).5 When substitution occurs at
INTRODUCTION
■
position 3 (e.g., R = Me, as in Tp4Bo,3Me), the same pattern a is
then referred to as “normal” since the largest substituent is
placed away from boron,6 in contrast to hydrotris(pyrazolyl)-
borates where the bulky substituent virtually always ends up at
position 3.2,7
As a consequence of its strong electronegativity and hardness,
fluorine imparts unique properties to organic or inorganic
compounds that extend to intermolecular interactions and
supramolecular chemistry.1 Fluorinated ligands exhibit high
electron-withdrawing properties and good oxidative stability
which yields stable yet strongly electrophilic metal centers.
Tris(pyrazolyl)borates have been extensively used as ligands in
inorganic and organometallic chemistry because of their pocket-
type configuration affording a good protection around the
metal center and an easy tuning of their electronic and steric
properties.2 Up to now, only few examples of fluorinated
scorpionate ligands were synthesized because of limitation of
the synthetic methologies.3 On the basis of indazolyl units, we
recently reported a perfluorinated hydrotris(3-trifluoromethy-
lindazol-1-yl)borate and its use in alkane activation.4 Interested
in fine-tuning the electronic and steric properties of the
fluorinated tris(indazolyl)borate ligands, we investigated the
synthesis and structures of aryl-substituted hydrotris-
(indazolyl)borates [aryl = phenyl, pentafluorophenyl, 3,5-
dimethylphenyl and 3,5-bis(trifluoromethyl)phenyl] and their
thallium complexes.
For homoscorpionates based on indazoles, all thallium
compounds are of C3v, type a, symmetry except for those
containing a 7-alkyl substituent and those obtained from 3-
methylnaphtopyrazole for which a 2:3 mixture of hydrotris(3-
methyl-2H-benz[g]indazol-2-yl) (type b) and hydrobis(3-
methyl-2H-benz[g]indazol-2-yl)(3-methyl-2H-benz[g]indazol-
1-yl)borate (Cs, type c, Scheme 1) was observed.6 To the best
of our knowledge, no Cs symmetric complex of type d has ever
been described. Herein we report the synthesis and the
structural characterization of a family of aryl-4,5,6,7-tetrafluor-
oindazoles and their related fluorinated hydrotris-
(arylindazolyl)borates. The expected C3v structure Tl[F12-
Tp4Bo,3Ph] (Tl-1),8 Tl[F12-Tp4Bo,3(3,5‑Me2C6H3)] (Tl-3), and
Tl[F30-Tp4Bo,3(3,5‑(CF3)2C6H3)] (Tl-4) is obtained from 3-
phenyl-4,5,6,7-tetrafluoro-1H-indazole, 3-(3,5-dimethylphen-
yl)- and 3-(3,5-bis(trifluoromethyl)phenyl)-indazoles, respec-
tively. In complete contrast, when the highly electron poor 3-
Unsubstituted hydrotris(indazolyl)borates adopt a so-called
“abnormal” regiochemistry where boron is apparently bound to
the more sterically hindered, yet electronically richer, nitrogen
as in a (R = H, a Tp4Bo following Trofimenko’s nomenclature)
Received: September 30, 2011
Published: February 16, 2012
© 2012 American Chemical Society
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Chart 1. Regiochemistry of Thallium Hydrotris(indazolyl)borates
Scheme 1. Synthesis of Aryl-4,5,6,7-tetrafluoroindazoles 1, 2, 3, and 4
Figure 1. (a) Molecular view of 1; (b) Packing diagram of 1 along the a axis; for clarity the molecules from the same layer are drawn with the same
color; intermolecular interactions are marked as dotted lines (red: NH···N hydrogen bonds, black: F···F, pale blue: NH···F).
pentafluorophenyl-4,5,6,7-tetrafluoro-1H-indazole is reacted
with TlBH4, a Cs structure is exclusively formed in TlHB(3-
pentafluorophenyl-4,5,6,7-tetrafluoroindazol-1-yl)2(3-penta-
fluorophenyl-4,5,6,7-tetrafluoroindazol-2-yl), Tl[F27-
Tp(4Bo,3C6F5)*] (Tl-2), the first d-type complex ever reported
(Chart 1). We have also discovered that the bis(indazolyl)-
borate synthesized from 3-phenyl-4,5,6,7-tetrafluoro-1H-inda-
zole, an intermediate in the synthesis of Tl-2, is indeed of Cs
symmetry but exhibits an “abnormal” regiochemistry with
TlH2B(3-pentafluorophenyl-4,5,6,7-tetrafluoroindazol-2-yl)2
Tl[F18-Bp3Bo,5C6F5] (Tl-5) being formed, indicating that
complex rearrangements do take place in poly(indazolyl)borate
thallium chemistry.
available 2,3,4,5,6-pentafluorobenzophenone and decafluoro-
benzophenone, respectively. Overall yields range from 83 to
95% except for the 3-(3,5-bismethylphenyl)-4,5,6,7-tetrafluoro-
1H-indazole (3) (37%) because of a poor cyclization yield. The
new indazoles were spectroscopically and crystallographically
characterized. The spectroscopic data for 1 and 2 matched
those previously reported.10 In all compounds, the benzo ring is
characterized by four 19F NMR signals more shielded in the
sequence F-5 < F-7 < F-6 < F-4 with a unique fine structure.
The chemical shift of F-4 (as a pseudo triplet) appears more
sensitive to substitution at position 3 (C6H5, δ −140.0; C6F5, δ
−154.6; 3,5-Me2C6H3, δ −142.7; 3,5-(CF3)2C6H3, δ −140.0).
In the crystal, indazoles 1, 2, and 4 show different packings
depending on the aryl substituent. Indeed, 1 crystallizes in the
space group Pbc21 (Figure 1). In the asymmetric unit, two
similar but not identical molecules of 1 are connected by two
NH···N hydrogen bonds (red lines (Figure 1b): N1−N2 =
1.356(7), N3−N4 = 1.345(6), N1···N4 = 2.86, N2···N3 = 2.87
Å). The dimers are packed as stacked arrays of antiparallel pairs
along the a axis (Figure 1b). This arrangement is likely the
consequence of attractive π−π interactions between electro-
deficient fluorinated benzo rings (C6F4) and phenyl (C6H5)
substituents.1b,11 The molecules are not planar, the phenyl
group being twisted with respect to the fluorinated indazole
unit (N2−C7−C8−C13 = −24°; N4−C20−C21−C26 = 25°).
RESULT AND DISCUSSION
■
Synthesis and Characterization of Aryl-4,5,6,7-tetra-
fluoroindazoles. Indazoles were synthesized following the
reported procedure for 3-trifluoromethyl-4,5,6,7-tetrafluoro-
1H-indazole.9 Pentafluorobromobenzene was treated by n-
butyllithium at low temperature followed by addition of the
corresponding methyl benzoate to generate the pentafluor-
obenzophenone. Then the cyclization was realized by adding
hydrazine hydrate and heating the reaction mixture in toluene
(Scheme 1). Compounds 1 and 2, previously synthesized via a
slightly different route,10 were obtained from the commercially
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Figure 2. (a) Molecular view of 2. (b) Dimer formed via N−H···N hydrogen bonds. (c) Packing diagram of 2; for clarity the chains having the same
c coordinate are drawn with the same color; intermolecular interactions are marked as dotted lines (red: N−H···H, black: F···F, blue: NH···F).
Figure 3. (a) Molecular view of 4. (b) Dimer formed via N−H···N hydrogen bonds. (c) Packing diagram of 4 along the b axis; for clarity the
molecules from the same layer are drawn with the same color; intermolecular interactions are marked as dotted lines (red: N−H···H hydrogen
bonds, black: F···F, blue: H···F).
Scheme 2. Synthesis of Fluorinated Hydrotris(indazolyl) borates Tl-1, Tl-3, Tl-4
Short contacts, smaller than the van der Waals radii are also
apparent (Figure 1b) such as C−F···F−C [black lines: 2.84 Å
(126.7, 145.6°) and 2.81 Å (99.6, 139.7°)], N−H···F−C (pale
blue lines: N···F 3.10, H···F 2.45 Å; N−H···F 131°, N···F−C
165°) and C−H···F−C (C···F 3.21, H···F 2.45 Å; C−H···F 136,
C···F−C 132°). All these interactions participate in the dimers’
arrangement in the crystal lattice.1b,11−13
subsequent benzo and C6F5 rings (black lines; F13···F2 2.75
Å, C13−F13···F2 135°).13
The packing of 4 is similar to that observed for the phenyl
tetrafluoroindazole 1 (Figure 3) with an antiparallel motif
translated along the b axis. This allows a more attractive π-
stacking between the electron-deficient tetrafluorobenzo ring
and the partially fluorinated xylyl moiety. The stacking is overall
simpler since the space group is P21/c and, as a consequence,
the dimers resulting from N−H···N hydrogen bonds are
symmetrical. Indazole 4 exhibits a dihedral angle N1−C1−C8−
C9 of −22.8° between the 3,5-bis(trifluoromethyl)phenyl and
the tetrafluoroindazolyl groups. Short contacts can be high-
lighted: CF3···F (black lines (Figure 3b): 2.77−2.93 Å) and H−
N···H hydrogen bonds (N1−N2 = 1.340(5) Å, N2···N1′ = 2.90
Å; N2−H2···N1′ = 135°). Moreover the distortion of the xylyl
group allows C−H···F interchain interactions [blue lines
(Figure 3b): (i) C−H···F3C: 2.53 Å (121.2, 152.7°); (ii) C−
H···F−Cbenzo: 2.66 Å (145.5, 147.7°)].13
Introducing electron-withdrawing fluorines on the phenyl
group modifies the crystal packing (Figure 2). Indazole 2
crystallizes in the space group P1. Two molecules of 2, related
̅
by an inversion center, are connected by N−H···N hydrogen
bonds (red lines, Figure 2b; N1−N2 = 1.3542(16) Å, N2···N1′
= 2.85 Å, N2−H2 = 0.851(9) Å; N2−H2···N1′ = 140°). The
dimers stack parallel along the a axis. The C6F5 and the
indazolyl moiety are not coplanar with a dihedral angle N2−
C7−C1−C6 of −41.5°. Close contacts are noticed as N−
H···F−C between a fluorine from a C6F5 ring and H2−N2 of a
neighboring dimer (pale blue lines; F6···N2 2.98 Å, C6−
F6···N2 153°), and C−F···F−C between fluorines of
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Figure 4. (a), (b), (c) Molecular views of Tl-1, Tl-3, and Tl-4, respectively (For relevant bond length and angles, see Table 1).
Table 1. Selected Intra- and Intermolecular Metrical Parameters for Tl-1, Tl-3, and Tl-4
compounds
Tl-1
Tl-3
Tl-4
Tl−N (Å)
B−N (Å)
N−Tl−N (deg)
B1−N2−N1−Tl1 (deg)
B1−N4−N3−Tl1 (deg)
B1−N6−N5−Tl1 (deg)
B−N−N−C (deg)
π−π: d(plane/plane) (offset) (Å)
2.660(4), 2.659(4), 2.615(4)
1.554(6), 1.548(6), 1.545(6)
2.5925(16), 2.6178(16), 2.6450(17)
1.555(3), 1.547(3), 1.560(3)
69.44(5), 72.64(5), 69.46(5)
−6.5
2.653(3), 2.648(3), 2.645(3)
1.542(5), 1.534(5), 1.550(5)
69.98(9), 69.84(9), 75.05(9)
22.0
69.57(12)
−24.3
−28.2
12.4
̧ 64.82(12), 75.96(12)
7.9
24.1
10.2
38.2
174.1, −165.6, 176.2
N(1)N(2): 3.56 (2.11)
N(3)N(4): 3.37 (1.71)
2.80 (128.0, 90.8)
161.8, 166.4, 172.9
N(1)N(2): 3.46 (2.52)
N(3)N(4): 3.73 (2.20)
2.87
166.9, 175.9,172.4
N(5)N(6): 3.40 (2.31)
Cbenzo−F···F−Cbenzo d (Å) (angles (deg))
H···F (Å) (angles (deg))
2.78 (171.5, 85.2),
2.63 (131.1, 80.6)
2.59 (165.5, 118.5)
2.66 (133.4, 123.6)
2.65 (165.0, 109.1)
Scheme 3. Synthesis of Tl[F27-Tp(4Bo,3C6F5)*] (Tl-2)
Interestingly, none of the aryl-substituted fluorinated
indazoles 1, 2, and 4 pack in a helix fashion like the 3-
trifluoromethyl-4,5,6,7-tetrafluoro-1H-indazole.9,14 It is likely
that in addition to different steric demands aromatic π−π
interactions, whether between fluorinated rings or between
fluorinated and hydrogenated rings, overcome those between
saturated CH or CF and tetrafluorinated indazolyl rings that
lead to crystallizations as catemers.15
compounds show a single set of signals pointing to an overall
C3v symmetry in solution.
The X-ray structures of Tl-1, Tl-3, and Tl-4 confirm that an
a-type structure is adopted as expected (Figure 4). Tl−N, B−N
bonds and N−Tl−N angles are virtually equal, except for Tl-1
where N−Tl−N angles vary more than 10° (Table 1). All of
them are unexceptional.17 The structures are distorted from
idealized C3v, Cs, or C3 symmetries. Apart from dihedral angles
about the connection at C-3, the distortion mainly concerns the
coordination to thallium (Table 1: torsion angles: B−N−N−
Tl). Complex Tl-3 appears to be the least distorted. For all
complexes, each indazolyl ring is not coplanar with the
corresponding mean B−N−N−Tl plane, a situation particularly
noteworthy for one of the ring (Figure 4; Table 1: torsion angle
B−N−N−C following the order: B1−N2−N1−C3, B1−N4−
N3−C16, B1−N6−N5−C29). Complex Tl-1 exhibits a close
intramolecular F···F contact of 2.81 Å between F6 and F32,
both 7-F of N1N2 and N5N6 based indazolyl groups. These
distorted structures are probably due to an interplay between
steric and packing effects.
Synthesis and Characterization of Complexes Tl-1, Tl-
3, and Tl-4. Upon reaction with KBH4, 3-methyl-1H-
indazole6a or its perfluorinated 3-trifluoromethyl-1H-tetrafluor-
oindazole4a yield hydrotris(indazolyl)borates with a-type
structures regardless of the counterion. The new thallium
complexes Tl[F12-Tp4 B o , 3 P h
] (Tl-1), Tl[F12-
Tp4Bo,3(3,5‑Me2C6H3)] (Tl-3), Tl[F30-Tp4Bo,3(3,5‑(CF3)2C6H3)] (Tl-
4) were obtained from an excess of the appropriate aryl-1H-
tetrafluoroindazole and most conveniently TlBH4 instead of the
more conventional KBH4 in 72, 77, and 62% yield, respectively
(Scheme 2).16 The synthesis of Tl[F27-Tp4Bo,3C6F5] (Tl-2) is
discussed in the next section. 11B NMR yielded a single broad
signal around δ −3. 1H and 19F NMR solution spectra for these
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The packing of these thallium complexes is mainly dictated
by aromatic type interactions whether they concern fluorinated
rings, hydrogenated rings, or rings containing nitrogens and
fluorines as analyzed in the literature.1,11,13,17c
Synthesis and Characterization of Complex Tl-2.
When an excess of 3-pentafluorophenyl-4,5,6,7-tetrafluoro-
1H-indazole (2) is reacted with TlBH4 in the melt at about
200 °C, TlHB(3-pentafluorophenyl-4,5,6,7-tetrafluoroindazol-
1-yl)2(3-pentafluorophenyl-4,5,6,7-tetrafluoroindazol-2-yl) Tl-
[F27-Tp(4Bo,3C6F5)*] (Tl-2) is formed and is isolated in 65%
yield (Scheme 3).
F26 (2.78 Å), that is, F-7 on one indazolyl ring and an ortho
fluorine of this inverted C6F5 ring, respectively.
To get a better insight into this regiochemistry issue, the
relative stability of different isomers, most prominently those of
a- and d-type, has been probed by a density functional theory
(DFT) analysis. At the PBE1PBE/SDD/6-31G(d) level, the
optimized d-type structure Tl-2-d (Figure 6) does not show the
long Tl1−N5 bond as in the solid state where a cocrystallized
methanol molecule interacts with the thallium. Apart from this
particular Tl−N bond, calculated bond lengths and angles
including those to Tl matched the experimental ones. The
relative orientation of the “inverted” C6F5 ring with respect to
the benzo rings is very similar to that observed in the solid state
with the “inverted” C6F5 ring being almost parallel to one
indazolyl group. The optimized structure of hypothetical Tl-2-a
(Figure 6b) is very close in energy (+1.5 kJ.mol−1) to that of
Tl-2-d (Figure 6a) suggesting that there is little, if any,
thermodynamic preference for the one or the other. This
suggests that the exclusive formation of Tl-2 with a d-type
structure is most probably kinetically driven, and that the
barrier linking a- and d-type isomers is very high since Tl-2
does not rearrange upon heating (see above). Hypothetical b-
and c-type isomers were also optimized (see Supporting
Information) and their computed energies (relative to Tl-2-d),
Tl-2-b (+0.8 kJ.mol−1) and Tl-2-c (+2.5 kJ.mol−1), are again
very close, reinforcing the idea that kinetics, not thermody-
namics, play a key role in the selective synthesis of Tl-2. It is
noteworthy that Tl-2-b, despite having three bulky penta-
fluorophenyl groups syn to the boron, is the second most stable
isomer after Tl-2-d. Similarly, none of these structures appear
notably distorted. A larger energy difference (9 kJ.mol−1)
favoring Tl-1 (i.e., Tl-1-a) over hypothetical Tl-1-d was
computed.
Careful examination of crude reaction mixtures by 19F NMR
showed no other regioisomer was present at all stages of the
reaction. The 19F NMR data clearly point to an overall Cs
structure in solution with two sets of resonances in a 2:1 ratio
for each type of fluorine, including those from the C6F5 rings
(viz. for F-5 fluorines with respect to boron: δ −167.18 (pt, 2F,
J 19.2 Hz, F-5 syn), −152.32 (pt, 1F, J 16.9 Hz, F-5 anti). Also,
no isomerization was observed upon heating pure Tl-2 in
anisole at 453 K for 8 h as ascertained by 19F NMR. X-ray
diffraction reveals that Tl-2 (as its MeOH solvate Tl-2.MeOH
in the crystal) indeed has the first d-type structure ever
reported (Figure 5). It has been verified that redissolving the
Synthesis and Characterization of a Bis(indazolyl)-
borate Thallium Complex. In an effort to probe the origin of
the regiochemistry of Tl-2 we decided to look at its stepwise
synthesis by first preparing the bis(indazolyl)borate thallium
compound. Surprisingly the perfluorinated bis(indazolyl)borate
complex isolated in 74% yield (Scheme 4), is TlH2B(3-
pentafluorophenyl-4,5,6,7-tetrafluoroindazol-2-yl)2 Tl[F18-
Bp3Bo,5C6F5] (Tl-5) which indeed has the two indazolyl
substituents syn to the boron (Figure 7). 11B NMR shows a
single signal at δ −8.8, shielded as compared to those for
Tl[Fn-Tp4Bo,R] (see above).
The two indazolyl rings are symmetrically bound to the
thallium. There is a weak B1−H1b···Tl1 agostic interaction
(Tl···H 3.11, Tl···B 3.53 Å)18 with a longer Tl···H distance than
for the intermolecular interaction B1′-H1b′···Tl1 (Tl···H = 2.68,
Tl···B = 3.55 Å) between two repeating units. The coordination
at the thallium is supplemented by π-type interactions with a
neighboring molecule (Tl···centroid N1.N2, 3.37; Tl···N1,
3.28; Tl···N2, 3.49; Tl···C1, 3.28 Å), and numerous F···F and
CF···aromatic short contacts.
Figure 5. ORTEP drawing of Tl-F27-Tp(4Bo,3C6F5)*·MeOH Tl-
2·MeOH. Relevant bond lengths (Å) and angles (deg): N1−Tl1
2.659(4), N3−Tl1 2.623(4), N5−Tl1 2.837(4), N2−B1 1.535(6),
N4−B1 1.555(6), N6−B1 1.531(7); N5−Tl1−N3 69.58(11), N5−
Tl1−N1 67.47(12), N3−Tl1−N1 70.44(12), N6−B1−N4 108.8(4),
N6−B1−N2 112.1(4), N4−B1−N2 110.3(4).
crystals gave the same 19F NMR spectrum confirming that
neither the crystallization process nor the presence of MeOH in
the crystals induced any rearrangement or isomerization.
As can be seen from Figure 5, two indazolyl groups (N1N2
and N5N6) are bound to boron via their N1-nitrogen (N2 and
N6) with C6F5 rings syn to the thallium. The third indazolyl
group which contains N3 is “inverted”, that is, bound to boron
via its N2-nitrogen, N4 thereby directing the C6F5 ring syn to
the boron. The B−N bond with this “inverted” indazole is
barely longer than the other two (1.56 vs 1.53 Å). The C6F5
group of the “inverted” indazolyl group (torsional angle of 67°)
is almost parallel to one of the indazolyl groups, that containing
N1 and N2 (angle between planes 8°). The closest intra-
molecular contact between fluorines is that between F10 and
Monitoring the synthesis of Tl-2 by 19F NMR only showed
excess 3-pentafluorophenyl-4,5,6,7-tetrafluoro-1H-indazole 2
and Tl-5 before the third equivalent of indazole reacts. This
confirms that complex rearrangements in the form of multiple
B−N bond cleavage/formation events take place in this
chemistry. Also, it is remarkable that a given connection
between an indazolyl ring and boron might well show different
preferences in bis or tris(indazolyl)borates. Even though we
have no mechanistic information, it is gratifying that single
isomers are obtained in all cases.
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Figure 6. DFT optimized structures of Tl-2-d (a) and Tl-2-a (b). Color code: dark gray, C; blue, N; green, F; pink, B; purple, Tl; H omitted for
clarity.
Scheme 4. Synthesis of Tl[F18-Bp3Bo,5C6F5] (Tl-5)
fluorinated poly(indazolyl)borates for which we can tune the
steric and electronic properties. We have already started to
explore their utilization as ligands, particularly in the field of
alkane functionalization,4 and there is no doubt they will
complement the growing family of highly fluorinated poly-
(azolyl)borates.3
EXPERIMENTAL SECTION
■
All experiments were performed using conventional vacuum line and
Schlenk tube techniques or in a drybox under argon. Pentafluor-
obenzophenone, perfluorobenzophenone, methyl 3,5-dimethylben-
zoate were purchased from Aldrich and methyl 3,5-bistrifluorome-
thylbenzoate from Fluorochem. The fluorinated indazoles were
prepared according to a procedure used for the synthesis of 3-
trifluoromethyl-4,5,6,7-tetrafluoroindazole9 and following slight mod-
ifications to recently published procedures for 1 and 2.10 Thallium
borohydride (TlBH4) was prepared according to a published
procedure.16 NMR experiments were run on a Bruker DPX-300
MHz spectrometer (1H, 300.13; 19F, 282.40; 11B, 96.25 MHz).
Elemental analyses were performed in the Analytical Service of our
Laboratory. Mass spectroscopic data were recorded on a QTRAP
Applied Biosystems mass spectrometer.
3-Phenyl-4,5,6,7-tetrafluoro-1H-indazole (1). Pentafluoroben-
zophenone (4.00 g, 14.7 mmol) was dissolved in toluene (20 mL) and
cooled down to 0 °C. Hydrazine monohydrate (715 μL, 14.7 mmol)
was then added dropwise, and the mixture was stirred for 1 h at low
temperature. The reaction mixture was then heated to reflux for 24 h,
yielding a white mixture with a yellow aqueous phase. The phases were
separated, and the aqueous phase was extracted with toluene (3 × 10
mL). The combined organic phases were dried over MgSO4, and all
volatiles were removed under vacuum, yielding a white solid that was
purified by sublimation under vacuum (ca 140 °C). The white crystals
were identified as 3-phenyl-4,5,6,7-tetrafluoro-1H-indazole (1) (3.72 g,
Figure 7. Molecular view Tl-5. Relevant bond lengths (Å) and angles
(deg): N1−Tl1 2.706(3), N3−Tl1 2.688(3), N2−B1 1.548(6), N4−
B1 1.555(5); N3−Tl1−N1 73.30(9), N4−B1−N2 109.5(3).
CONCLUSION
■
We have described the syntheses and characterization in
solution and in the solid state of several highly fluorinated
indazoles and indazolylborates. While phenyl, dimethylphenyl,
and bis(trifluoromethyl)phenyl substituents yield hydrotris-
(indazolyl)borates of the type Tl[Fn-Tp4Bo,R] with overall C3v
symmetry as expected, the use of the pentafluorophenyl
substituent yields Tl[F27-Tp(4Bo,3C6F5)*], a complex with
overall Cs symmetry that has one indazolyl group bound to B
via its N-2 nitrogen for the first time. While the cause of this
particular behavior remains unclear, it is noted that the
corresponding bis(indazolyl)borate, on the way to
Tp(4Bo,3C6F5)*, has both rings bound via N-2 demonstrating
that reversible B−N bond cleavage is facile in certain
circumstances. We now have in hands a range of highly
1
14.0 mmol, 95%). H NMR (CDCl3): δ 11.5 (vbr, 1H, NH), 7.85−
7.47 (m, 5H, C6H5). 19F NMR (CDCl3): δ −164.62 (ptd, 1F, J = 19.5,
2.8 Hz, F-5), −158.90 (pt, 1F, J = 18.6 Hz, F-7), −156.18 (pt, 1F, J =
19.2 Hz, F-6), −140.38 (pt, 1F, J = 18.6 Hz, F-4). Anal. Calcd for
C13H6F4N2: C, 58.66; H, 2.27; N, 10.52. Found: C, 58.58; H, 1.75; N,
10.63.
3-Pentafluorophenyl-4,5,6,7-tetrafluoro-1H-indazole (2).
Following the same procedure, perfluorobenzophenone (2.50 g, 6.90
mmol) and hydrazine monohydrate (335 μL, 6.90 mmol) yielded a
white solid identified as 3-pentafluorophenyl-4,5,6,7-tetrafluoro-1H-
1
indazole (2) (2.22 g, 90%). H NMR (acetone-d6): δ 10.72 (vbr, 1H,
NH). 19F NMR (acetone-d6): δ −166.92 (ptd, J = 18.6, 2.2 Hz, 1F, F-
5), −164.02 (m, 2F, meta-C6F5), −159.29 (pt, J = 18.4 Hz, 1F, F-7),
−159.04 (ptd, J = 18.1, 2.3 Hz, 1F, F-6), −154.57 (pt, J = 20.6 Hz, 1F,
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F4), −150.84 (m, 1F, para-C6F5), −142.42 (m, 2F, ortho-C6F5). Anal.
Calcd for C13HF9N2: C, 43.84; H, 0.28; N, 7.87. Found: C, 43.48; H,
0.00; N, 8.62.
solution of K[F12-Tp4Bo,3Ph] (0.50 g, 0.59 mmol) in chloroform
(50 mL). The mixture was stirred vigorously for 24 h. By that
time solid Tl2SO4 had disappeared. The organic layer was then
decanted, and the water extracted with chloroform (2 × 10
mL). After the evaporation of the combined organic phases, a
white powder of Tl[F12-Tp4Bo,3Ph] (Tl-1) (0.42 g, 0.41 mmol)
was obtained in 68% yield. Anal. Calcd for C39H16BF12N6Tl: C,
46.30; H, 1.59; N, 8.31. Found: C, 45.74; H, 1.02; N, 8.29.
3-(3,5-Dimethylphenyl)-4,5,6,7-tetrafluoro-1H-indazole (3).
3,5-Dimethylpentafluorobenzophenone was first synthesized following
the reported procedure from commercially available methyl-3,5-
dimethylbenzoate. Pentafluorobromobenzene (3.80 mL, 30.49
mmol) was dissolved in diethyl ether (10 mL) and cooled at −80
°C. n-Butyllithium (12.19 mL, 30.50 mmol), precooled to −80 °C, was
added dropwise over a period of 20 min. The mixture was stirred for
another 10 min at low temperature. After that time, a solution of
methyl-3,5-dimethylbenzoate (5.01 g, 30.50 mmol) in diethyl ether
(20 mL) was quickly added, and the reaction was stirred for 15 min,
before being quenched with cold HCl (2N, 70 mL, 0 °C). The mixture
was stirred overnight at room temperature. The two phases were
separated, and the aqueous phase was extracted with diethyl ether (2 ×
20 mL). The combined organic phases were dried over MgSO4 and all
volatiles were removed under reduced pressure to yield a viscous
colorless liquid, which was purified by column chromatography
(CH2Cl2-hexane 1:5). The resulting white solid 3,5-dimethylpenta-
fluorobenzophenone (4.84 g, 16.1 mmol) was used without further
purification for the subsequent cyclization step in the usual manner.
3,5-Dimethylpentafluorobenzophenone (4.84 g, 16.1 mmol) and
hydrazine monohydrate (0.79 mL, 16.3 mmol) yielded white crystals
identified as 3-(3,5-dimethylphenyl)-4,5,6,7-tetrafluoro-1H-indazole
Tl[F27-Tp(4Bo,3C6F5)*] (Tl-2). A mixture of 3-pentafluorophenyl-
4,5,6,7-tetrafluoroindazole (2) (1.00 g, 2.81 mmol) and TlBH4 (0.17 g,
0.78 mmol) was heated up to 200 °C for 4 h. The reaction mixture was
allowed to cool to room temperature. Excess 2 was removed by
vacuum sublimation at 140 °C. Tl[F27-Tp4Bo,3C6F5] (Tl-2) was
obtained as a white powder (0.65 g, 0.51 mmol, 65%). 19F NMR
(acetone-d6): δ −167.18 (pt, 2F, J = 19.2 Hz, F5 syn), −166.17 (pt, 1F,
J = 16.9 Hz, F6 anti), −164.08 (m, 2F, meta-C6F5 anti), −163.58 (m,
4F, meta-C6F5 syn), −161.08 (pt, 1F, J = 16.9 Hz, F7 anti), −159.57
(pt, 2F, J = 18.6 Hz, F6 syn), −155.70 (m, 1F, F4 anti), 155.42 (m, 2F,
F7 syn), −154.51 (pt, 2F, J = 20.6 Hz, para-C6F5 syn), −152.89 (m, 1F,
para-C6F5 anti), −152.32 (pt, 1F, J = 16.9 Hz, F5 anti), −151.94 (pdt,
2F, J = 22.0, 9.3 Hz, F4 syn), −141.24 (m, 4F, ortho-C6F5 syn),
−139.29 (pd, 2F, J = 21.2 Hz, ortho-C6F5 anti). 11B NMR (acetone-
d6): δ −3.15. Anal. Calcd for C39HBF27N6Tl: C, 36.55; H, 0.08; N,
6.56. Found: C, 36.14; H, 0.00; N, 7.65. ESI-MS: m/z (relative
intensity) 1077.6 (100, M−), 205 (100, M+).
1
Tl[F12-Tp4Bo,3(3,5‑Me2C6H3)] (Tl-3). A mixture of 3-(3,5-dimethyl-
phenyl)-4,5,6,7-tetrafluoro-1H-indazole (3) (0.50 g, 1.70 mmol) and
TlBH4 (0.11 g, 0.50 mmol) was heated up to 210 °C for 4 h. The
reaction mixture was allowed to cool to room temperature. The
residue was washed with pentane. Tl-3 was obtained as a white powder
(0.42 g, 0.38 mmol, 77%). 1H NMR (acetone-d6): δ 7.31 (s, 6H, ortho-
C6H3Me2), 7.13 (s, 3H, para-C6H3Me2), 2.34 (s, 18H, C6H3Me2). 19F
NMR (acetone-d6): δ −168.81 (pt, J = 19.8 Hz, 1F, F-5), −160.16 (pt,
J = 18.6 Hz, 1F, F-7), −154.56 (m, 1F, F-6), −145.52 (pt, J = 19.2 Hz,
1F, F-4). 11B NMR (acetone-d6): δ −2.67. Anal. Calcd for
C45H28BF12N6Tl: C, 49.32; H, 2.58; N, 7.67. Found: C, 51.21; H,
1.89; N, 8.33. DCI-MS: m/z 1097.2 [M + H]+. High resolution LSI
calculated [M + H]+: 1096.2 (C45H28BF12N6Tl). Found 1096.2 (100%
[M + H]+).
(3) (3.31 g, 37%). H NMR (acetone-d6): δ 13.61 (vbr, 1H, NH),
7.50 (s, 2H, ortho-C6H3Me2), 7.13 (s, 1H, para-C6H3Me2), 2.40 (s,
6H, C6H3Me2). 19F NMR (acetone-d6): δ −168.76 (pt, J = 19.2 Hz,
1F, F-5), −160.94 (pt, J = 19.2 Hz, 1F, F-7), −160.56 (pt, J = 19.2 Hz,
1F, F-6), −142.65 (pt, J = 19.2 Hz, 1F, F-4). Anal. Calcd for
C15H10F4N2: C, 61.23; H, 3.43; N, 9.52. Found: C, 58. 91; H, 2.92; N,
9.54.
3-(3,5-Bis(trifluoromethyl)phenyl)-4,5,6,7-tetrafluoro-1H-in-
dazole (4). Following the same procedure detailed for 3, 3-(3,5-
bis(trifluoromethyl)phenyl)-4,5,6,7-tetrafluoro-1H-indazole (4) was
obtained from the commercially available methyl-3,5-bis-
1
(trifluoromethyl)benzoate (yield: 83%). H NMR (CDCl3): δ 10.78
(vbr, 1H, NH), 8.41 (s, 2H, o-C6H3(CF3)2), 7.98 (s, 1H, p-
C6H3(CF3)2). 19F NMR (CDCl3): δ −162.60 (pt, J = 19.5 Hz, 1F,
F-5), −158.00 (pt, J = 18.6 Hz, 1F, F-7), −154.60 (pt, J = 19.2 Hz, 1F,
F-6), −139.95 (pt, J = 18.9 Hz, 1F, F-4), −63.03 (s, 6F, CF3). Anal.
Calcd for C15H4F10N2: C, 44.79; H, 1.00; N, 6.97. Found: C, 43.21; H,
0.96; N, 6.12.
Tl[F12-Tp4Bo,3(3,5‑(CF3)2C6H3)] (Tl-4). A mixture of 3-(3,5-bis-
(trifluoromethyl)phenyl)-4,5,6,7-tetrafluoroindazole (4) (1.10 g, 2.73
mmol) and TlBH4 (0.19 g, 0.85 mmol) was heated up to 180 °C for 5
h. The reaction mixture was allowed to cool to room temperature. The
residue was sublimated at 140 °C to remove unreacted 4. Tl[F30-
Tp4Bo,3(3,5(CF3)2C6H3)] (Tl-4) was obtained as a white powder (0.75 g,
Tl[F12-Tp4Bo,3Ph] (Tl-1). Two procedures were used to synthesize
Tl-1.
1
0.53 mmol, 62%). H NMR (CDCl3): 8.01 (s, 9H, C6H3(CF3)2). 19F
(1) A mixture of 3-phenyl-4,5,6,7-tetrafluoroindazole (1) (2.0 g,
7.50 mmol) and TlBH4 (0.484 g, 2.21 mmol) was heated up to
180 °C for 2 h. The reaction mixture was allowed to cool to
room temperature. The residue was washed with a methanol/
pentane (1/5) mixture. Tl[F12-Tp4Bo,3Ph] (Tl-1) was obtained
as a white powder after drying under vacuum (1.84 g, 1.82
mmol, 82%). Anal. Calcd for C39H16BF12N6Tl: C, 46.30; H,
1.59; N, 8.31. Found: C, 46.45; H, 1.53; N, 8.71. ESI-MS: m/z
(relative intensity) 807.5 (100, M−), 205 (100, M+).
(2) KBH4 was first dried at 140 °C under vacuum for 1 h. KBH4
(0.12 g, 2.2 mmol) and 3-phenyl-4,5,6,7-tetrafluoroindazole (1)
(2.0 g, 7.5 mmol) were introduced in a Schlenk tube. The
mixture was heated up to 190 °C for 4 h. The reaction mixture
was allowed to cool to room temperature and excess 1 was
removed by vacuum sublimation at 170 °C. The grayish residue
was washed with methanol and dried under vacuum. K[F12-
Tp4Bo,3Ph] was obtained as a white powder (1.40 g, 1.65 mmol,
75%). [1H NMR (acetone-d6): δ 7.72−7.25 (m, 15H, 3×C6H5).
19F NMR (acetone-d6):δ −171.55 (pt, 1F, J = 19.8 Hz, F-5),
−165.34 (pt, 1F, J = 19.5 Hz, F-7), −155.91 (m, 1F, F-6),
−145,02 (pt, 1F, J = 18.6 Hz, F-4). IR: ν(B−H)= 2554 cm−1.
11B NMR (acetone-d6): δ −2.26. ESI-MS: m/z (relative
intensity) 807.5 (100, M−)]. A solution of thallium(I) sulfate
(0.223 g, 0.44 mmol) in water (50 mL) was then added to a
NMR (CDCl3): δ −162.45 (pt, J = 19.6 Hz, 1F, F-5), −153.34 (pt, J =
18.10 Hz, 1F, F-7), −151.20 (m, 1F, F-6), −144.33 (pt, J = 18.8 Hz,
1F, F-4), −63.26 (s, 6F, C6H3(CF3)2). 11B NMR (CDCl3): δ −2.98.
Anal. Calcd for C45H10BF30N6Tl: C, 38.07; H, 0.71; N, 5.92. Found: C,
38.78; H, 0.00; N, 6.34. ESI-MS: m/z (relative intensity) 1215.4 (100,
M−), 205 (100, M+).
Tl[F18-Bp3Bo,3C6F5] (Tl-5). A mixture of 3-pentafluorophenyl-4,5,6,7-
tetrafluoroindazole (2) (0.50 g, 1.40 mmol) and TlBH4 (0.15 g, 0.70
mmol) was heated up to 150 °C for 1 h. The reaction mixture was
allowed to cool to room temperature. The residue was washed with a
pentane/toluene (3/1) mixture. Tl[F18-Bp4Bo,3C6F5] (Tl-5) was
obtained as a white powder (0.48 g, 0.52 mmol, 74%). 19F NMR
(acetone-d6): δ −167.96 (pt, J = 17.4 Hz, 2F, F-5), −164.61 (m, 4F,
meta-C6F5), −163.32 (pt, 2F, J = 16.9 Hz, F-7), −156.61 (pt, 2F, J =
18.2 Hz, F-6), −154.48 (pt, 2F, J = 20.2 Hz, F-4), −153.32 (pt, 2F, J =
18.8 Hz, para- C6F5), −138.87 (pd, 4F, J = 19.8 Hz, ortho-C6F5). 11B
NMR (acetone-d6): δ −8.8. Anal. Calcd for C26H2BF18N4Tl: C, 33.63;
H, 0.22; N, 6.04. Found: C, 34.54; H, 0.00; N, 6.91. ESI-MS: m/z
(relative intensity) 723.5 (100, M−), 205 (100, M+).
X-ray Crystallography. Data for 1, 2, 4, Tl-1, Tl-2·MeOH, Tl-4,
Tl-5 were collected at 180 K on an Xcalibur Oxford Diffraction
diffractometer equipped with an Oxford Instrument Cooler Device.
Data for Tl-3 were collected at 180 K on a Bruker Kappa Apex II
diffractometer equipped with an Oxford Cryosystems Cryostream
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Table 2. Crystal Data, Data Collection, and Refinement for Compounds 1, 2, 4, Tl-1, Tl-2·MeOH, Tl-3, Tl-4
1
2
4
Tl-1
Tl-2·MeOH
Tl-3
Tl-4
formula
formula weight
temperature/K
λ (MoKα)/Å
crystal system
space group
a/Å
C13H6F4N2
266.20
180
C13HF9N2
356.16
180
C15H4F10N2
402.20
C39H16BF12N6Tl
1011.76
C40H5BF27N6OTl·CH4O
1345.72
180
C45H28BF12N6Tl
1095.91
C45H10BF30N6Tl
1419.77
180
180
180
180
0.71073
orthorhombic
Pbc21
0.71073
triclinic
0.71073
monoclinic
P21/c
0.71073
0.71073
triclinic
0.71073
0.71073
monoclinic
P21/c
triclinic
triclinic
P1
P1
P1
P1
̅
̅
̅
̅
7.0480(5)
14.0810(8)
21.7250(14)
90
3.81860(10)
12.3676(3)
13.7752(4)
67.237(3)
82.115(2)
89.001(2)
593.77(3)
2
12.6031(10)
7.5208(6)
15.6167(15)
90
11.9370(6)
11.9610(6)
14.4060(7)
104.020(4)
110.394(4)
103.113(4)
1757.50(15)
2
11.8175(3)
13.9013(3)
14.9703(4)
110.435(2)
99.598(2)
104.244(2)
2145.53(11)
2
11.2334(8)
13.2250(11)
15.366(2)
104.709(3)
96.815(6)
100.048(5)
2142.0(4)
2
20.5920(4)
21.8080(5
11.1760(2)
90
b/Å
c/Å
α/deg
β/deg
90
109.848(10)
90
94.027(2)
90
γ/deg
V/Å3
90
2156.1(2)
8
1392.3(2)
4
5006.42(18)
4
Z
ρcalcd/Mg m−3
μ/mm−1
F(000)
1.640
1.992
1.919
1.912
2.083
1.699
1.884
0.148
0.22
0.209
4.700
3.93
3.863
3.379
1072
348
792
972
1284
1068
2712
crystal size/mm 0.2 × 0.15 × 0.05 0.25 × 0.15 × 0.03 0.2 × 0.15 × 0.05 0.19 × 0.12 × 0.07 0.3 × 0.2 × 0.08
0.2 × 0.12 × 0.03 0.25 × 0.15 × 0.08
θ range/deg
2.89−26.36
3.58−25.68
2.72−24.71
2.61−26.37
2.66−25.35
2.13−32.1
2.72−26.37
index range
−8 ≤ h ≤ 8
−13 ≤ k ≤ 17
−27 ≤ l ≤ 27
−4 ≤ h ≤ 4
−15 ≤ k ≤ 15
−16 ≤ l ≤ 16
−14 ≤ h ≤ 14
−8 ≤ k ≤ 8
−14 ≤ l ≤ 18
−14 ≤ h ≤ 14
−14 ≤ k ≤ 14
−15 ≤ l ≤ 18
−14 ≤ h ≤ 14
−16 ≤ k ≤ 16
−18 ≤ l ≤ 17
−16 ≤ h ≤ 16
−19 ≤ k ≤ 19
−22 ≤ l ≤ 21
−25 ≤ h ≤ 17
−27 ≤ k ≤ 27
−13 ≤ l ≤ 13
reflections
collected/
unique
15734/2262,
R(int) = 0.0692
11765/2253,
R(int) = 0.0184
9132/2373,
R(int) = 0.0323
12062/6924,
R(int) = 0.1092
15000/7809,
R(int) = 0.0254
64621/14857,
R(int) = 0.0367
38754/10217,
R(int) = 0.0317
completeness to 26.36 (100%)
25.68 (99.7%)
24.71 (100.0%)
26.37 (96.5%)
25.35 (99.5%)
32.1 (99.1%)
26.37 (99.9%)
θ/derg
absorption
corrections
semiempirical
from equivalents
semiempirical
from equivalents
semiempirical
from equivalents
semiempirical
from equivalents
semiempirical from
equivalents
semiempirical
from equivalents
semiempirical
from equivalents
max/min
0.989/0.975
0.997/0.906
0.987/0.96
0.715/0.41
0.725/0.408
0.888/0.592
0.748/0.561
transmission
refinement
method
full-matrix least-
full-matrix least-
full-matrix least-
full-matrix least-
full-matrix least-squares on full-matrix least-
full-matrix least-
squares on F2
squares on F2
squares on F2
squares on F2
F2
squares on F2
squares on F2
data/restraints/
parameters
2262/1/343
2253/1/220
1.141
2373/0/241
1.128
6924/0/532
1.135
7809/0/707
14857/0/592
10217/0/748
1.064
goodness-of-fit
0.983
1.034
1.006
on F2
final R indices I R1 = 0.0620
> 2σ(I)
R1 = 0.027
R1 = 0.0694
R1 = 0.0311
R1 = 0.035
R1 = 0.0283
R1 = 0.0299,
wR2 = 0.1506
wR2 = 0.081
R1 = 0.0323
wR2 = 0.1742
R1 = 0.0964
wR2 = 0.0680
R1 = 0.0568
wR2 = 0.0873
R1 = 0.0421
wR2 = 0.058
R1 = 0.0383
wR2 = 0.0780
R1 = 0.0425
R indices (all
data)
R1 = 0.0766
wR2 = 0.1606
wR2 = 0.083
wR2 = 0.1881
wR2 = 0.0884
wR2 = 0.0908
wR2 = 0.0602
wR2 = 0.0812
largest diff.
0.751/−0.318
0.241/−0.168
1.128/−0.867
1.847/−1.857
1.539/−0.842
0.817/−0.837
1.210/−0.739
peak/hole/Å3
Cooler Device. Details of crystal data, data collection, and refinement
can be found in Table 2. The structures have been solved by direct
methods using SHELXS-8619 for Tl-1, SHELXS-9719 for 4, and
SIR9220 for all other compounds. The structures were refined by
means of least-squares procedures on F2 with the aid of the program
SHELXL9718 included in the software package WinGX version 1.63.21
The Atomic Scattering Factors were taken from the International
Tables for X-ray Crystallography.22 All hydrogen atoms were
geometrically placed and refined by using a riding model. All non-
hydrogen atoms were anisotropically refined, and in the last cycles of
D(calc), F(000), and the molecular weight are only valid for the
ordered part of the structure. Even if the best possible crystal has been
sought and utilized for the data collection and even if the data were
collected at low temperature, compound 4 was weakly diffracting. As a
result, there is a low sine(θ_max)/wavelength (0.59), and a poor data/
parameter ratio. Moreover, the overall quality of the data being poor,
this leads to spurious peaks and holes of residual electron density.
Compound Tl-4 presents highly disordered fluorines.
refinement a weighting scheme was used, where weights were
Computational Details. All DFT calculations were performed
with Gaussian03.26 Structures were optimized at the PBE1PBE level.27
The thallium was described with the Stuttgart/Dresden ECP valence
basis set and the quasi-relativistic effective core potential of Kuchle et
al.28 The 6-31G(d) basis was used for F, N, C, B, and H.29 Geometry
optimizations were carried out without any symmetry restrictions, and
the nature of the extrema (minima) was verified with analytical
frequency calculations (no imaginary frequency).
2
calculated from the following formula: w = 1/[σ2(Fo ) + (aP)2
+
2
bP] where P = (Fo + 2Fc2)/3. Plots of the molecular structures were
performed with the programs ORTEP3223 or CAMERON24 with 30%
probability displacement ellipsoids for non-hydrogen atoms.
For compounds Tl-3, it was not possible to resolve diffuse electron-
density residuals (enclosed solvent molecule). Treatment with the
SQUEEZE facility from PLATON25 resulted in a smooth refinement.
Since a few low order reflections are missing from the data set, the
electron count will be underestimated. Thus, the values given for
2900
dx.doi.org/10.1021/ic202125c | Inorg. Chem. 2012, 51, 2893−2901

Inorganic Chemistry
Article
(b) Choudhury, A. R.; Guru Row, T. N. CrystEngComm 2006, 8, 265−
274. (c) Mariaca, R.; Behrnd, N.-R.; Eggli, P.; Stoeckli-Evans, H.;
Hulliger, J. CrystEngComm. 2006, 8, 222−232.
(13) Packing details for indazoles 1, 2, 4 and thallium complexes Tl-
1, Tl-2, Tl-3, and Tl-4 are reported in the Supporting Information.
(14) Perfluoalkyl substituted indazoles Rf-4,5,6,7-tetrafluoro-1H-
indazoles crystallize as 3-fold helices (Rf = CF3, CF2CF3), 1-D chains
(Rf = CF2CF2CF3, CF2CF2CF2CF3) and stacks of dimers (Rf =
CF2CF2CF2CF2CF2CF3). See ref 9 and unpublished results from this
Laboratory.
ASSOCIATED CONTENT
* Supporting Information
Crystallographic data (CIF files), detailed packing analyses, full
ref 26, and computational details (Cartesian coordinates and
absolute energies of optimized structures). This material is
available free of charge via the Internet at http://pubs.acs.org.
■
S
AUTHOR INFORMATION
Corresponding Author
*E-mail: michel.etienne@lcc-toulouse.fr.
Notes
■
(15) For a theoretical and computational analysis of crystal packing
in 1H-pyrazoles, see: Foces-Foces, C.; Alkorta, I.; Elguero, J. A. Acta
Crystallogr., Sect. B 2000, B56, 1018−1026.
(16) Kitamura, M.; Takenaka, Y.; Okuno, T.; Hall, R.; Wunsch, B.
̈
The authors declare no competing financial interest.
Eur. J. Inorg. Chem. 2008, 1188−1192.
(17) (a) Janiak, C. Coord. Chem. Rev. 1997, 163, 107−216.
(b) Craven, E.; Mutlu, E.; Lundberg, D.; Temizdemir, S.; Dechert,
S.; Brombacher, H.; Janiak, C. Polyhedron 2002, 21, 553−562.
(c) Janiak, C. J. Chem. Soc., Dalton Trans. 2000, 3885−3896.
(18) Fillebeen, T.; Hascall, T.; Parkin, G. Inorg. Chem. 1997, 36,
3787−3790.
(19) Sheldrick, G. M. Acta Crystallogr., Sect. A 2008, A64, 112.
(20) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A. J.
Appl. Crystallogr. 1993, 26, 343−350.
(21) Farrugia, L. J. Appl. Crystallogr. 1999, 32, 837.
(22) International tables for X-Ray crystallography; Kynoch Press:
Birmingham, England, 1974; Vol IV.
ACKNOWLEDGMENTS
■
The CNRS and the ERA Chemistry programme of FP6 (2nd
call, contract number 1736154) are acknowledged for support.
S.G. thanks Universitat Jaume I, Castellon (Spain) for a
traveling grant.
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