Bis(tetrafluorophenyl)borane

Article abstract of DOI:10.1039/c2dt30924f

The reaction of the Grignard reagent (p-C₆F₄H)MgBr with Me₂SnCl₂ afforded the p-C₆F₄H transfer reagent Me₂Sn(p-C₆F₄H)₂ (1). Subsequent reaction o

Full text of DOI:10.1039/c2dt30924f

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PAPER
Bis(tetrafluorophenyl)borane†
Daniel Winkelhaus, Beate Neumann, Hans-Georg Stammler and Norbert W. Mitzel*
Received 27th April 2012, Accepted 10th May 2012
DOI: 10.1039/c2dt30924f
The reaction of the Grignard reagent (p-C6F4H)MgBr with Me2SnCl2 afforded the p-C6F4H transfer
reagent Me2Sn(p-C6F4H)2 (1). Subsequent reaction of 1 with BCl3 led to the chloroborane
(p-C6F4H)2BCl (2), which was converted to the borane [(p-C6F4H)2BH]2 (3) by treatment with the
hydride source Me2SiHCl. By reaction of tetrafluoropyridine with i-PrMgCl followed by the in situ
reaction with Me2SnCl2, the stannane Me2Sn(C5F4N)2 (4) could be obtained. However, this did not react
with BCl3. The resulting products were characterized by elemental analyses and NMR spectroscopy.
Single crystal X-ray diffraction experiments were performed for compounds 1, 2 and 4. The crystal
structure of the literature known compound Me2Sn(C6F5)2 (5) was determined and compared with
structures of 1 and 4.
Introduction
The strong Lewis acid tris(pentafluorophenyl)borane, B(C6F5)3,
was first synthesized in the early 1960s by Massey, Park and
Stone.1,2 Later on, B(C6F5)3 was used in a variety of different
applications. Starting as a catalyst in metallocene Ziegler–Natta
olefin polymerization,3–5 it was used for abstraction reactions or
Scheme 1 Reaction of B(C6F5)3 with phosphines.
as a stoichiometric reagent. In 2006 Stephan and co-workers dis-
covered the field of frustrated Lewis pairs (FLPs) on the basis of
the strong Lewis acid B(C6F5)3 and secondary phosphines.6 The
concept was based on steric demanding Lewis acids and bases
precluding the classical adduct formation which leads to an
unquenched reaction potential.7–9 The research area of FLPs has
grown tremendously over the last years, finding applications in
the metal-free activation of dihydrogen,10,11 carbon dioxide12–14
and other small molecules.15,16 Moreover, the heterolytic
activation of H2 by FLPs was shown to serve as a metal-free
pathway for hydrogenation catalysis of imines, nitriles and
enamines.17–20
To introduce (p-C6F4H)2B groups, we present in this contri-
bution the synthesis of the chloroborane (p-C6F4H)2BCl and the
hydroboration reagent [(p-C6F4H)2BH]2. Furthermore, the pre-
cursor tin compounds Me2Sn(C6F4H)2 and Me2Sn(C5F4N)2 will
be presented and their molecular structures will be compared
with the literature known compound Me2Sn(C6F5)2.26
Results and discussion
The Lewis acid B(C6F5)3 is the most used acid for FLP
chemistry. In this regard the introduction of the B(C6F5)2 group
via salt elimination with the chloroborane (C6F5)2BCl21 is
accomplished. Alternative hydroboration reactions with Piers’
Bis(tetrafluorophenyl)borane
The reaction of p-C6F4HBr with i-PrMgCl afforded the Grignard
reagent (p-C6F4H)MgBr which was reacted in situ with
Me2SnCl2 in Et2O to give the p-C6F4H disubstituted stannane
Me2Sn(p-C6F4H)2 (1) upon workup as a colourless crystalline
solid in 68% yield (Scheme 2).
22
borane [(C6F5)2BH]2 have been tested. However, nucleophilic
aromatic substitution at the para-position of the C6F5 group
by less sterically encumbered phosphines has been observed
(Scheme 1).23
To prevent this attack, Ullrich, Stephan et al. have introduced
the Lewis acid B(p-C6F4H)3 and have shown its wide appli-
cation in FLP chemistry.24,25
Compound 1 was characterized by elemental analysis and by
NMR spectroscopy of the nuclei H, 13C, 19F and 119Sn. The
1
1H NMR spectrum of Me2Sn(p-C6F4H)2 (1) shows a signal at
δ = 6.26 ppm attributable to the hydrogen atom in the para-
3
4
position. The JHF and JHF couplings explain the triplet of
triplets signal pattern. The signal for the methyl group is
observed at δ = 0.56 ppm featuring the typical 117/119Sn satel-
lites. The corresponding signal in the 13C NMR spectrum is
Universität Bielefeld, Fakultät für Chemie, Anorganische Chemie und
Strukturchemie, Universitätsstraße 25, 33615 Bielefeld, Germany.
E-mail: mitzel@uni-bielefeld.de; Fax: (+49) (0)521 106-6182
†CCDC 874087, 874088, 874089 and 874090. For crystallographic data
in CIF or other electronic format see DOI: 10.1039/c2dt30924f
4
detected as a quintet at δ = −6.1 ppm with a JCF of 2.5 Hz and
117/119Sn satellites with a 1J(117/119Sn/13C) coupling of 425.3 Hz.
Dalton Trans., 2012, 41, 8609–8614 | 8609
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Scheme 2 Synthesis of Me2Sn(p-C6F4H)2 (1) and (p-C6F4H)2BCl (2).
The 19F NMR signals of the meta and ortho fluorine atoms are
observed at δ = −137.7 and −123.2 ppm. The 119Sn{1H} NMR
spectrum shows a multiplet at δ = −66.5 ppm. The molecular
structure of 1 was determined by X-ray diffraction experiments;
it will be discussed later on. Subsequent reaction of the aryl
transfer reagent Me2Sn(p-C6F4H)2 (1) with BCl3 in hexane
at 120 °C afforded the monomeric electrophilic borane
(p-C6F4H)2BCl (2) (Scheme 2). The reaction was carried out
in analogy to the synthesis of (C6F5)2BCl,21 thus a detailed
description of the experiment is not given here. After fractional
sublimation the chloroborane 2 was obtained in 74% yield as a
colourless crystalline solid.
Compound 2 was characterized by elemental analysis and by
1H, 11B, 13C and 19F NMR spectroscopy. The 1H NMR spectrum
of 2 shows a triplet of triplets at δ = 6.13 ppm (2JHF = 9.20 Hz,
3JHF = 7.68 Hz). The product gives rise to a broad resonance in
the 11B NMR spectrum at δ = 59.7 ppm. The 19F NMR spectrum
shows two signals at δ = −137.7 (m-C6F4H) and −130.5 ppm
(o-C6F4H).
Fig. 1 Molecular structure of 2 in the crystal. Hydrogen atoms are
omitted for clarity. Bond lengths [Å] and angles [°]: Cl(1)–B(1)
1.755(1), B(1)–C(7) 1.568(2), B(1)–C(1) 1.568(2), C(7)–B(1)–C(1)
123.3(1), C(7)–B(1)–Cl(1) 118.3(1), C(1)–B(1)–Cl(1) 118.4(1), C(2)–
C(1)–C(6) 114.9(1), C(2)–C(1)–B(1) 121.0(1), C(6)–C(1)–B(1)
124.1(1), C(8)–C(7)–B(1) 123.4(1), C(12)–C(7)–B(1) 121.6(1).
Single crystals of the chloroborane 2 were obtained upon slow
sublimation at 60 °C/10−2 mbar. Compound 2 crystallizes in the
orthorhombic space group Pbca with eight molecules in the unit
cell (Fig. 1).
The boron atom has a trigonal planar geometry. The bond
angles around the boron atom adopt values of 123.3(1), 118.3(1)
and 118.4(1)° for C(7)–B(1)–C(1), C(7)–B(1)–Cl(1) and C(1)–
B(1)–Cl(1), respectively.
Scheme 3 Synthesis of [(p-C6F4H)2BH]2 (3).
indicative of dimeric boranes.29 A monomeric species as it is
22
present for [(C6F5)2BH]2 was not observed in the spectra of
compound 3.
The B–C bond lengths in 2 are both at 1.568(2) Å. This is
almost identical to the bond lengths in (C6F5)2BCl [1.566(6) and
1.551(7) Å]27 and (C6F2H3)2BCl [1.561(3) and 1.556(3) Å].28
The B(1)–Cl(1) bond at 1.755(1) Å is of similar length to the
corresponding bond in (C6F5)2BCl and (C6F2H3)2BCl. Most
likely, steric repulsion between the fluorine atoms F(1) and F(8)
[F(1)⋯F(8) distance 2.997 Å] leads to a twisting of the p-C6F4H
groups out of the C(1)–C(7)–B(1)–Cl(1) plane by 35.9 and
37.0°, respectively.
Attempt to synthesize bis(tetrafluoropyridyl)borane
The tetrafluoropyridyl (C5F4N) substituent is known to possess a
stronger electron withdrawing character than C6F4H or C6F5
groups.30 In order to obtain the tetrafluoropyridyl substituted
chloroborane (C5F4N)2BCl, we first synthesized the C5F4N
disubstituted stannane Me2Sn(C5F4N)2 (4). Analogous to 1,
tetrafluoropyridine was treated with i-PrMgCl, followed by the
in situ reaction with Me2SnCl2 in Et2O. Subsequent workup
afforded compound 4 in 60% yield as a colourless solid
(Scheme 4).
Analogous to the synthesis of [(C6F5)2BH]2 22 the chloroborane
2 was reacted with the hydride source Me2SiHCl to give the
electrophilic borane reagent [(p-C6F4H)2BH]2 (3) in 81% yield
as a colourless powder (Scheme 3).
The 1H NMR spectrum of compound 3 shows a broad peak at
δ = 4.54 ppm attributable to the B–H fragment. The signal for
the para hydrogen atom of the aryl ring is observed at δ =
3
6.02 ppm as a triplet of triplets (2JHF = 9.20 Hz, JHF = 7.35
Hz). In the 19F NMR spectrum the signals for the meta and
ortho fluorine atoms are detected at
δ = −136.9 and
−133.7 ppm, respectively. The 11B NMR spectrum shows a
broad resonance at δ = 20.3 ppm which is in the region
Scheme 4 Synthesis of Me2Sn(C5F4N)2 (4).
8610 | Dalton Trans., 2012, 41, 8609–8614
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1
In the H NMR spectrum of compound 4 the resonance for
C–Sn–C angles between the carbon atoms of the two aryl substi-
tuents feature the smallest values in compounds 1, 4 and 5 with
angles of 99.5(1) [C(7)–Sn(1)–C(1)], 100.5(1) [C(1)–Sn(1)–C(6)]
the methyl group is observed at δ = 0.44 ppm. The correspond-
ing signal in the 13C NMR spectrum is detected at δ = −6.1 ppm
as
a = 2.4 Hz) exhibiting tin satellites
quintet (4JCF
(1J(117/119Sn/13C) = 429 Hz). The 19F NMR spectrum shows two
signals at δ = −125.5 (m-C5F4N) and −91.3 ppm (o-C5F4N).
The 119Sn{1H} resonance at δ = −67.2 ppm is split into a quintet
of quintets due to the coupling with the fluorine atoms.
Single crystals suitable for X-ray diffraction of 4 were
obtained from a concentrated hexane solution; its molecular
structure will be discussed below.
The reaction for the synthesis of the tetrafluoropyridyl substi-
tuted chloroborane (C5F4N)2BCl was attempted analogously to
that of 2 with BCl3 in hexane at 120 °C (Scheme 4). However,
even after long reaction times (1 week) only the reagent Me2Sn-
(C5F4N)2 (4) could be isolated and no reaction could be
observed.
Crystal structures of tin compounds
As mentioned above, crystal structures of the stannanes 1 and 4
could be obtained. For comparison reasons we also determined
the crystal structure of the literature known compound Me2Sn-
(C6F5)2 (5).21,26 The structures of 1, 4 and 5 are displayed in
Fig. 2–4; selected structural parameters are listed in the captions.
The coordination around the tin atoms in compounds 1, 4 and
5 is markedly distorted tetrahedral. In all compounds the largest
C–Sn–C angle is observed between the two methyl groups with
values of 115.7(1) [C(13)–Sn(1)–C(14) in 1], 119.2(1) [C(11)–
Sn(1)–C(12) in 4] and 116.6° [C(13)–Sn(1)–C(14) in 5]. The
Fig. 3 Molecular structure of 4 in the crystal. Hydrogen atoms are
omitted for clarity. Selected bond lengths [Å] and angles [°]: Sn(1)–
C(11) 2.119(2), Sn(1)–C(12) 2.123(2), Sn(1)–C(1) 2.174(2), Sn(1)–C(6)
2.180(2), C(11)–Sn(1)–C(12) 119.2(1), C(11)–Sn(1)–C(1) 111.7(1),
C(12)–Sn(1)–C(1) 107.8(1), C(11)–Sn(1)–C(6) 108.4(1), C(12)–Sn(1)–
C(6) 107.5(1), C(1)–Sn(1)–C(6) 100.5(1).
Fig. 2 Molecular structure of 1 in the crystal. Hydrogen atoms are
omitted for clarity. Selected bond lengths [Å] and angles [°]: Sn(1)–
C(13) 2.123(2), Sn(1)–C(14) 2.125(2), Sn(1)–C(7) 2.162(2), Sn(1)–C(1)
2.163(2), C(13)–Sn(1)–C(14) 115.7(1), C(13)–Sn(1)–C(7) 111.0(1),
C(14)–Sn(1)–C(7) 108.2(1), C(13)–Sn(1)–C(1) 109.3(1), C(14)–Sn(1)–
C(1) 111.8(1), C(7)–Sn(1)–C(1) 99.5(1).
Fig. 4 Molecular structure of 5 in the crystal. Hydrogen atoms are
omitted for clarity. Selected bond lengths [Å] and angles [°]: Sn(1)–
C(13) 2.119(2), Sn(1)–C(14) 2.122(2), Sn(1)–C(1) 2.165(2), Sn(1)–C(7)
2.168(2), C(13)–Sn(1)–C(14) 116.6(1), C(13)–Sn(1)–C(1) 110.1(1),
C(14)–Sn(1)–C(1) 106.4(1), C(13)–Sn(1)–C(7) 107.6(1), C(14)–Sn(1)–
C(7) 110.6(1), C(1)–Sn(1)–C(7) 105.0(1).
This journal is © The Royal Society of Chemistry 2012
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and 105.0(1)° [C(1)–Sn(1)–C(7)], respectively. This observation
can be explained with the VSEPR model. The bonding electron
pairs of the more electron withdrawing aryl substituents require
less space and the electron releasing methyl substituents more
space, which leads to an increase and decrease of these bond
angles, respectively. Furthermore, the more electron withdrawing
character of the C5F4N substituent in 4 compared to the C6F5
group in 5 is verified by the smaller C–Sn–C bond angle at the
tin atom [100.5(1) in 4, 105.0(1)° in 5]. Interestingly, the
smallest C–Sn–C bond angle between the two aryl groups is
observed for the less electron withdrawing C6F4H substituent in
1 [99.5(1)°].
The Sn–C bonds to the methyl substituents in compounds 1, 4
and 5 are distinctly shorter than the Sn–C bonds to the aryl sub-
stituents. The Sn–C bond length to the methyl group in 1
(average 2.124 Å) is marginally longer than in 4 and 5 (average
2.121 Å for both compounds). By contrast, the Sn–C distance to
the aryl group exhibits the smallest value in 1 (average 2.163 Å)
of all three compounds. The average Sn–C bonds to the aryl
groups in 4 and 5 are 2.177 and 2.167 Å, respectively.
externally (11B, BF3·OEt2; 19F, CFCl3; 119Sn, SnMe4). Elemental
analyses were performed using a Leco CHNS 932 instrument.
Crystallographic structure determinations
Single crystals suitable for X-ray diffraction measurement were
picked inside a glove-box, suspended in a paratone-N–paraffin
oil mixture, mounted on a glass fibre and transferred onto the
goniometer of the diffractometer. The measurements were
carried out with Mo-Kα radiation (λ = 0.71073 Å). The struc-
tures were solved by direct methods and refined by full-matrix
least-squares cycles (program SHELX-97).32 Crystallographic
data (excluding structure factors) for the structures reported in
this paper have been deposited with The Cambridge Crystallo-
graphic Data Centre as supplementary publications. The
deposition numbers are provided in Table 1.
Me2Sn(C6F4H)2 (1). i-PrMgCl (4.4 mL, 8.7 mmol, 2.0 M in
Et2O, 2 equiv.) was added to a solution of p-C6F4HBr (2.0 g,
8.7 mmol, 2 equiv.) in 25 mL Et2O at ambient temperature and
the mixture was stirred for 1 h. To the turbid solution was added
solid Me2SnCl2 (0.96 g, 4.4 mmol). The suspension was stirred
for an additional 2 h and filtered. The residue was washed with
10 mL hexane and the solvent was removed from the collected
extracts under reduced pressure to give a colourless liquid,
Conclusion
Herein we described the synthesis of the p-C6F4H transfer
reagent Me2Sn(p-C6F4H)2 (1) which was used to obtain the
chloroborane (p-C6F4H)2BCl (2). Subsequent treatment of 2
with the hydride source Me2SiHCl afforded the electrophilic
borane [(p-C6F4H)2BH]2 (3). NMR spectroscopic data showed
that compound 3 is dimeric in solution. The synthesized stan-
nane Me2Sn(C5F4N)2 (4) was found to be unreactive towards
reaction with BCl3 and thus no C5F4N substituted chloroborane
could be obtained.
Crystal structures of the tin compounds Me2Sn(p-C6F4H)2 (1)
and Me2Sn(C5F4N)2 (4) were compared with the structure of the
literature known compound Me2Sn(C6F5)2 (5). The bond angles
reflect the electronegativity of the substituents.
1
which crystallized on standing. Yield: 1.33 g (68%). H NMR
3
(500.1 MHz, C6D6, 298 K): δ = 6.26 (tt, 2JHF = 9.30 Hz, JHF
=
7.34 Hz, 2H, CH), 0.56 ppm (s, J(117/119Sn/1H) = 32 Hz, 6H,
2
CH3); 13C{1H} NMR (125.7 MHz, C6D6, 298 K): δ = 148.9
1
1
(dm, JCF = 236.5 Hz, C6F4H), 145.8 (dm, JCF = 252.0 Hz,
2
2
C6F4H), 116.3 (t, JCF = 43.5 Hz, i-C6F4H), 108.3 (t, JCF
=
23 Hz, C6F4H), −6.1 ppm (quint, 4JCF = 2.5 Hz, 1J(117/119Sn/13C)
= 425 Hz); 19F NMR (470.5 MHz, C6D6, 298 K): δ = −137.7
(m, 4F, m-C6F4H), −123.2 ppm (m, 4F, o-C6F4H); 119Sn{1H}
NMR (186.4 MHz, C6D6, 298 K): δ = −66.5 ppm (m).
C14H8F8Sn (446.91): calcd C 37.62, H 1.80; found C 37.55,
H 1.97.
In contrast to the B(C6F5) moiety, the B(p-C6F4H) fragment is
not accessible for nucleophilic aromatic substitution. Therefore,
the chloroborane (p-C6F4H)2BCl (2) and the electrophilic borane
[(p-C6F4H)2BH]2 (3) could be interesting synthetic tools to
obtain a broader range of FLPs.
(C6F4H)2BCl (2). (C6F4H)2BCl (2) was prepared using a pro-
cedure exactly analogous to the synthesis of (C6F5)2BCl. Sub-
stances used for the synthesis: Me2Sn(C6F4H)2 (1) (0.96 g,
2.2 mmol); BCl3 (0.25 g, 2.2 mmol); 5 ml hexane. Yield: 0.55 g
(74%). 1H NMR (500.1 MHz, C6D6, 298 K): δ = 6.13 ppm
2
3
(tt, JHF = 9.20 Hz, JHF = 7.68 Hz, 2H, CH); 11B{1H} NMR
(160.4 MHz, C6D6, 298 K): δ = 59.7 ppm (ν1/2 = 300 Hz);
13C{1H} NMR (125.7 MHz, C6D6, 298 K): δ = 147.6 (dm,
Experimental part
1
1JCF = 251.7 Hz, C6F4H), 145.9 (dm, JCF = 252.5 Hz, C6F4H),
General methods
2
117.7 (br, i-C6F4H), 111.2 ppm (t, JCF = 22.6 Hz, p-C6F4H);
All manipulations were performed under a rigorously dry inert
atmosphere of argon using standard Schlenk and glove-box tech-
niques. Diethyl ether and hexane were dried with LiAlH4 before
being employed in reactions. C6D6 was dried with Na/K alloy
and degassed. Me2Sn(C6F5)2 (5)21 and 2,3,5,6-tetrafluoropyri-
dine31 (at 0 °C) were synthesized according to literature pro-
cedures. Me2SnCl2, p-C6F4HBr and Me2SiHCl were purchased
from ABCR. Boron trichloride and isopropylmagnesium chlo-
ride solution (2 M in Et2O) were purchased from Aldrich. NMR
measurements were undertaken with a Bruker DRX 500 and a
Bruker Avance 500. NMR chemical shifts were referenced to the
residual peaks of the protons of the used solvents (1H,13C) or
19F NMR (470.5 MHz, C6D6, 298 K): δ = −137.7 (m, 4F,
m-C6F4H), −130.5 ppm (m, 4F, o-C6F4H). C12H2BClF8 (344.4):
calcd C 41.85, H 0.59; found C 41.32, H 0.49.
[(C6F4H)2BH]2 (3). Me2SiHCl (148 mg, 1.56 mmol, 8.7
equiv.) was condensed at −78 °C to (C6F4H)2BCl (2) (63 mg,
0.18 mmol). The reaction mixture was warmed to ambient
temperature and stirred for 30 min. The volatiles were removed
in vacuum, the residue was washed with hexanes (2 mL) and the
solvent was removed in vacuum until dryness was achieved.
The product was obtained as a colourless powder. Yield:
1
47 mg (81%). H NMR (500.1 MHz, C6D6, 298 K): δ = 6.02
8612 | Dalton Trans., 2012, 41, 8609–8614
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Table 1 Crystallographic data for compounds 1, 2, 4 and 5
1
2
4
5
Formula
Mr
T [K]
C14H8F8Sn
446.89
100(2)
C12H2BClF8
344.40
100(2)
C12H6F8N2Sn
448.88
100(2)
C14H6F10Sn
482.88
100(2)
Crystal size [mm]
Cryst. system
Space group
a [Å]
b [Å]
c [Å]
0.30 × 0.16 × 0.16
Monoclinic
P21/c
15.4580(15)
10.2400(10)
9.3710(11)
90
0.30 × 0.16 × 0.08
Orthorhombic
Pbca
14.0378(3)
6.2568(1)
26.9402(6)
90
0.20 × 0.12 × 0.10
Monoclinic
P21/n
9.5845(2)
10.1094(2)
14.2700(4)
90
0.29 × 0.16 × 0.12
Monoclinic
P21/c
12.7879(1)
11.8729(2)
20.1503(3)
90
α [°]
β [°]
94.291(9)
90
1479.2(3)
4
2.007
1.809
90
90
89.9819(12)
90
1382.67(6)
4
2.156
1.939
91.2741(8)
90
3058.65(7)
8
2.097
1.776
γ [°]
V [Å3]
Z
2366.20(8)
8
1.934
0.418
1344
ρcalcd [g cm−3
]
μ [mm−1
F(000)
]
856
856
1840
Θ range [°]
Index ranges
2.4 to 30.0
−21 ≤ h ≤ 21
−14 ≤ k ≤ 14
−13 ≤ l ≤ 13
35 391
4315
3657
3.0 to 30.0
−19 ≤ h ≤ 19
−8 ≤ k ≤ 8
−37 ≤ l ≤ 37
40 848
3441
2787
2.9 to 30.0
−13 ≤ h ≤ 13
−14 ≤ k ≤ 14
−20 ≤ l ≤ 20
33 346
4026
3513
3.1 to 30.0
−17 ≤ h ≤ 17
−16 ≤ k ≤ 16
−28 ≤ l ≤ 28
85 715
8907
7622
Reflns collect.
Unique reflns
Obs. refl (2σ)
Rint
0.0291
0.053
0.068
0.050
Data/restr/param
4315/0/210
1.046
3441/0/199
1.036
4026/0/210
1.068
8907/0/455
1.023
GoF (F2)
R1, wR2 [I > 2σ(I)]
R1, wR2 (all data)
0.0199, 0.0457
0.0297, 0.0507
0.44/−0.60
874087
0.0301, 0.0792
0.0410, 0.0853
0.37/−0.27
874088
0.0242, 0.0630
0.0297, 0.0656
0.47/−0.83
874089
0.0249, 0.0590
0.0323, 0.0621
0.63/−0.96
874090
Δρmax/min [e Å−3
]
CCDC no.
2
3
(tt, JHF = 9.20 Hz, JHF = 7.35 Hz, 2H, CH), 4.54 ppm (br s,
2H, BH); 11B{1H} NMR (160.4 MHz, C6D6, 298 K):
δ = 20.3 ppm (ν1/2 = 400 Hz); 13C{1H} NMR (125.7 MHz,
C12H6F8N2Sn (448.89): calcd C 32.11, H 1.35, N 6.24; found C
32.43, H 1.05, N 6.04.
1
C6D6, 298 K): δ = 146.1 (dm, JCF = 246.0 Hz, C6F4H), 145.6
1
Acknowledgements
(dm, JCF = 253.6 Hz, C6F4H), 112.0 (br, i-C6F4H), 109.2 ppm
2
(t, JCF = 22.5 Hz, p-C6F4H); 19F NMR (470.5 MHz, C6D6,
We thank Klaus-Peter Mester and Gerd Lipinski for recording
the NMR spectra and Brigitte Michel for performing the elemen-
tal analyses. We gratefully acknowledge the financial support of
the Fonds der Chemischen Industrie (stipend for D. W.) and the
DFG within the priority program SPP1178.
298 K): δ = −136.9 (m, 4F, m-C6F4H), −133.7 ppm (m, 4F,
o-C6F4H). C12H2BClF8 (344.4): calcd C 41.85, H 0.59; found C
41.32, H 0.49.
Me2Sn(C5F4N)2 (4). i-PrMgCl (6.6 mL, 13 mmol, 2.0 M in
Et2O, 2 equiv.) was added to a solution of 2,3,5,6-tetrafluoro-
pyridine (2.0 g, 13 mmol, 2 equiv.) in 40 mL Et2O at ambient
temperature and stirred for 1 h. To the turbid solution was added
Me2SnCl2 (1.4 g, 6.6 mmol) as a solid. The suspension was
stirred overnight and filtered. The residue was washed with
10 mL hexane and the solvent was removed from the collected
extracts under reduced pressure to give a colourless solid. Crys-
tals suitable for X-ray diffraction were obtained from a con-
centrated hexane solution. Yield: 1.78 g (60%). 1H NMR
Notes and references
1 A. G. Massey, A. J. Park and F. G. A. Stone, Proc. Chem. Soc., 1963,
212.
2 A. G. Massey and A. J. Park, J. Organomet. Chem., 1964, 2, 245–250.
3 E. Y.-X. Chen and T. J. Marks, Chem. Rev., 2000, 100, 1391–1434.
4 X. Yang, C. L. Stern and T. J. Marks, J. Am. Chem. Soc., 1991, 113,
3623–3625.
5 X. Yang, C. L. Stern and T. J. Marks, J. Am. Chem. Soc., 1994, 116,
10015–10031.
6 G. C. Welch, R. R. S. Juan, J. D. Masuda and D. W. Stephan, Science,
2006, 314, 1124–1126.
7 D. W. Stephan, Chem. Commun., 2010, 46, 8526–8533.
8 D. W. Stephan and G. Erker, Angew. Chem., 2009, 122, 50–81, (Angew.
Chem., Int. Ed., 2010, 49, 46–76).
9 D. W. Stephan, Org. Biomol. Chem., 2008, 6, 1535.
10 G. C. Welch and D. W. Stephan, J. Am. Chem. Soc., 2007, 129, 1880–
1881.
11 P. Spies, G. Erker, G. Kehr, K. Bergander, R. Fröhlich, S. Grimme and
D. W. Stephan, Chem. Commun., 2007, 5072–5074.
12 A. Berkefeld, W. E. Piers and M. Parvez, J. Am. Chem. Soc., 2010, 132,
10660–10661.
(500.1 MHz, C6D6, 298 K): δ = 0.44 ppm (s, J(117/119Sn/1H) =
2
32.5 Hz, 6H, CH3); 13C{1H} NMR (125.7 MHz, C6D6, 298 K):
1
1
δ = 144.2 (dm, JCF = 252.0 Hz, C5F4N), 143.0 (dm, JCF
=
2
253.5 Hz, C5F4N), 130.2 (t, JCF = 40.1 Hz, i-C5F4N),
−6.1 ppm (quint, JCF = 2.4 Hz, J(117/119Sn/13C) = 429 Hz);
19F NMR (470.5 MHz, C6D6, 298 K): δ = −125.5 (m, 4F,
m-C5F4N), −91.3 ppm (m, 4F, o-C5F4N); 119Sn{19F} NMR
4
1
2
(186.4 MHz, C6D6, 298 K): δ = −67.2 ppm (sept, JSnH = 67
Hz); 119Sn{1H} NMR (186.4 MHz, C6D6, 298 K): δ =
3
4
−67.2 ppm (quintet of quintets, JSnF = 26 Hz, JSnF = 16 Hz).
This journal is © The Royal Society of Chemistry 2012
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13 C. M. Mömming, E. Otten, G. Kehr, R. Fröhlich, S. Grimme,
D. W. Stephan and G. Erker, Angew. Chem., 2009, 121, 6770–6773,
(Angew. Chem., Int. Ed., 2009, 48, 6643–6646).
22 D. J. Parks, R. E. v. H. Spence and W. E. Piers, Angew. Chem., 1995,
107, 895–897; D. J. Parks, R. E. v. H. Spence and W. E. Piers, Angew.
Chem., Int. Ed. Engl., 1995, 34, 809–811.
14 G. Ménard and D. W. Stephan, Angew. Chem., 2011, 123, 8546–8549,
(Angew. Chem., Int. Ed., 2011, 50, 8396–8399).
15 R. C. Neu, E. Otten, A. Lough and D. W. Stephan, Chem. Sci., 2011, 2,
170–176.
23 G. C. Welch, L. Cabrera, P. A. Chase, E. Hollink, J. D. Masuda, P. Wei
and D. W. Stephan, Dalton Trans., 2007, 3407–3414.
24 M. Ullrich, A. J. Lough and D. W. Stephan, J. Am. Chem. Soc., 2009,
131, 52–53.
16 R. C. Neu, E. Otten and D. W. Stephan, Angew. Chem., 2009, 121, 9889–
9892, (Angew. Chem., Int. Ed., 2009, 48, 9709–9712).
17 P. Spies, S. Schwendemann, S. Lange, G. Kehr, R. Fröhlich and G. Erker,
Angew. Chem., 2008, 120, 7654–7657, (Angew. Chem., Int. Ed., 2008,
47, 7543–7546).
18 V. Sumerin, F. Schulz, M. Nieger, M. Leskelä, T. Repo and B. Rieger,
Angew. Chem., 2008, 120, 6090–6092, (Angew. Chem., Int. Ed., 2008,
47, 6001–6003).
19 V. Sumerin, F. Schulz, M. Nieger, M. Atsumi, C. Wang, M. Leskelä,
P. Pyykkö, T. Repo and B. Rieger, J. Organomet. Chem., 2009, 694,
2654–2660.
20 P. A. Chase, T. Jurca and D. W. Stephan, Chem. Commun., 2008, 1701–
1703.
25 M. Ullrich, A. J. Lough and D. W. Stephan, Organometallics, 2010, 29,
3647–3654.
26 R. D. Chambers and T. Chivers, J. Chem. Soc., 1964, 4782–4790.
27 W. E. Piers, R. E. v. H. Spence, L. R. MacGillivray and M. J. Zaworotko,
Acta Crystallogr., Sect. C: Cryst. Struct. Commun., 1995, C51, 1688–
1689.
28 W. Fraenk, T. M. Klapötke, B. Krumm, P. Mayer, H. Nöth, H. Piotrowski
and M. Suter, J. Fluorine Chem., 2001, 112, 73–81.
29 J. A. Soderquist and H. C. Brown, J. Org. Chem., 1980, 45, 3571–
3578.
30 B. Hoge and J. Bader, J. Fluorine Chem., 2007, 128, 857–861.
31 S. S. Laev and V. D. Shteingarts, Tetrahedron Lett., 1997, 38, 3765–
3768.
21 D. J. Parks, W. E. Piers and G. P. A. Yap, Organometallics, 1998, 17,
5492–5503.
32 G. M. Sheldrick, Acta Crystallogr., Sect. A: Fundam. Crystallogr., 2008,
A64, 112–122.
8614 | Dalton Trans., 2012, 41, 8609–8614
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