The thioether-methyleneborane (PhSCH2B(C6F 5)2)2: Synthesis and reactivity with donors and alkynes

Article abstract of DOI:10.1021/om200336t

2-Bromothioanisole, or thioanisole, was lithiated and subsequently reacted with ClB(C₆F₅)₂ to yield a new compound with the empirical formulation PhSCH₂B(C₆F₅) ₂, 1. NMR data at

Full text of DOI:10.1021/om200336t

ARTICLE
pubs.acs.org/Organometallics
The ThioetherꢀMethyleneborane (PhSCH2B(C6F5)2)2: Synthesis
and Reactivity with Donors and Alkynes
Cheryl A. Tanur and Douglas W. Stephan*
Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario, Canada, M5S 3H6
S Supporting Information
b
ABSTRACT: 2-Bromothioanisole, or thioanisole, was lithiated and subsequently
reacted with ClB(C6F5)2 to yield a new compound with the empirical formulation
PhSCH2B(C6F5)2, 1. NMR data at low temperature as well as X-ray crystallographic
data confirmed this species to be the dimer (PhSCH2B(C6F5)2)2, although an
equilibrium governs the interconversion of monomer to dimer at room temperature.
Compound 1 reacts with PtBu3 or OPEt3 to form adducts PhSCH2B(C6F5)2(L) (L =
PtBu3 2, OPEt3 3) in 85% and 87% yield, respectively. Compound 1 also reacts with
alkynes, namely, PhCCH, C4H9CCH, PhCCC4H9, C2H5CCC2H5, and PhCCPh, to
give the species (PhSCH2B(C6F5)2)(R0CdCR) (R = H, R0 = Ph 4, C4H9 5, R = Ph,
R0 = C4H9 6, R = R0 = C2H5 7, Ph 8) in yields in the range 70ꢀ92%. X-ray crystallographic analysis of 8 confirmed the five-
membered zwitterionic heterocyclic formulation.
’ INTRODUCTION
borane that incorporates a highly electrophilic B center. The
subsequent reactivity with a number of small molecules of this
species is probed. Although this species also forms a six-mem-
bered ring, the BꢀS bonds are labile, allowing capture of the
monomeric species by stronger donors. In addition, this species
is shown to react with alkynes to give the previously inaccessible
sulfonium-borate cyclopentene derivatives.
The reactivity of combinations of Lewis acids and bases in
which steric demands preclude or destabilize dative bond for-
mation has been the subject of intense development in recent
years.1ꢀ4 While these systems, known as frustrated Lewis pairs
(FLPs), react most notably with H2, such systems also demon-
strate broad reactivity with a variety of other small molecules
including disulfides,5 olefins,6 dienes,7 acetylenes,8ꢀ12 diynes,13,14
CO2,15,16 azides,17 and N2O.18 In the majority of instances, this
chemistry has been explored employing the combination of a
borane and a sterically encumbered phosphine. That being said,
other systems have been reported that incorporate Al-11,16
or C-based Lewis acids19 or amines,8,20ꢀ25 N-heterocycles,26ꢀ28
and carbenes29ꢀ32 as bases. In FLP chemistry, sulfur-based donors
’ RESULTS AND DISCUSSION
2-Bromothioanisole was lithiated initially at ꢀ78 °C, allowed
to warm to 25 °C for isolation, and subsequently reacted with
ClB(C6F5)2 at ꢀ38 °C to generate compound 1. A crude off-
white precipitate was isolated in near quantitative yield, purified
by extraction into toluene, and isolated, affording the pure
product in 32% yield. Alternatively, 1 was also derived from
the lithiation of thioanisole followed by subsequent reaction with
ClB(C6F5)2. This species gives rise to a broad signal at 5.1 ppm in
the 11B{1H} NMR spectrum, while the 19F{1H} NMR spectrum
displayed signals at ꢀ130.7, ꢀ153.6, and ꢀ163.0 ppm. The
have drawn less attention, although the adduct B(C6F5)3 SMe2
3
in combination with a bulky phosphine has been shown to effect
the heterolytic cleavage of H2. Similarly, thioethers such as Me2S
and (PhCH2)2S have been shown to add to terminal alkynes in
the presence of B(C6F5)3 to yield trans-zwitterions of the form
R2SC(R0)dCH(B(C6F5)3) (Scheme 1).9,11 It is also noteworthy
that the lability of thioether donors has been exploited by Hoshi
1
corresponding H NMR spectrum for 1 showed the expected
resonances for the phenyl protons and a singlet at 2.82 ppm.
These data were consistent with the empirical formulation of 1 as
PhSCH2B(C6F5)2. X-ray quality crystals of 1 were obtained from
a concentrated solution in toluene and bromobenzene at
ꢀ38 °C. The results showed that 1 is a dimer, in the solid state
of the formulation (PhSCH2B(C6F5)2)2 (Figure 1). In this form,
the two boron centers are each four coordinate, resulting from
coordination to sulfur. The BꢀS bond distances were found to be
2.054(4) and 2.071(5) Å. These bond lengths are comparable to
et al. in the reaction of B(C6F5)3 with BH3 SMe2 to generate the
3
adduct of Piers’ borane (C6F5)2BH SMe2,33,34 which was sub-
3
sequently used in a catalytic fashion for the hydroboration of a
terminal alkyne with HB(pin). The weak interaction between B
and S has also been employed by Gabbai and co-workers in
the development of aryl-linked boronꢀsulfur sensors for cyanide
and fluoride ions in water.35,36 Methylene-linked thioether boranes
are rare. Some years ago N€oth and co-workers37 described the
dimeric species (BH2CH2SMe)2 derived from the thermolysis of
the precursor amine adduct Me3NBH2CH2SMe. More recently
Wagner et al.38 described the related dimer (PhBrBCH2SMe)2.
Herein, we describe the synthesis of a methylene-linked thioether
€
those in the adduct B(C6F5)3 SMe2 (2.091(5) Å) reported by
3
Received: April 20, 2011
Published: June 07, 2011
r
2011 American Chemical Society
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dx.doi.org/10.1021/om200336t Organometallics 2011, 30, 3652–3657
|

Organometallics
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Scheme 1
Figure 2. Variable-temperature (a) 1H and (b) 19F NMR spectra of 1.
Chemical shifts are given in ppm.
Figure 1. POV-Ray depictions of 1. C: black, F: pink, B: yellow-green,
S: yellow.
Scheme 2
Denis et al.39 and similar to that in the dimer (PhBrBCH2SMe)2
(2.000(5) Å) described by Wagner and co-workers.38 The dimer
1 adopts a boat conformation in contrast to the geometry of
(PhBrBCH2SMe)2, which is a chair conformation with the Br
atoms occupying axial positions.38 The geometry of 1 is attrib-
uted to π-stacking between the electron-rich SꢀPh and the
electron-deficient BꢀC6F5 groups. This boat conformation is
reminiscent of the bent head-to-tail eight-membered ring re-
ported for the species (2-PyCH2BCy2)2.40
Variable-temperature NMR studies of 1 were undertaken.
Upon cooling to ꢀ60 °C, the 19F{1H} NMR spectrum reveals
two inequivalent environments for the C6F5 rings consistent with
a dimeric structure. Upon warming to 55 °C, these resonances
are replaced with those corresponding to a single C6F5 environ-
ment. In an analogous fashion, the 1H NMR data were tempera-
ture dependent. The resonance attributable to the methylene
protons observed as a singlet at 2.82 ppm broadens on cooling to
about ꢀ5 °C with the corresponding growth of a doublet of
doublets at 3.51 ppm. Upon further cooling to ꢀ60 °C, this
quartet coalesces to a single broad peak at 3.47 ppm. (Figure 2).
The corresponding information from the 11B spectra was less
informative, as a single broad resonance was observed at 0.92 ppm
at 55 °C and was not observable at ꢀ60 °C. These data suggest
complex equilibria, involving monomerꢀdimer interconversion.
Using an external standard as a reference, integration of the 1H
NMR signals attributable to the monomeric and dimeric forms
of 1 allowed an evaluation of the enthalpy and entropy asso-
ciated with the monomerꢀdimer equilibrium. These values were
determined to be 34.9 kJ/mol and 122.6 J/(mol K), res-
3
pectively. These energies correspond to a Gibbs free energy of
ꢀ1.63 kJ/mol and thus a Keq (25 °C) of 1.9. For comparative
purposes the corresponding thermodynamic parameters were
determined for B(C6F5)3 SMe2. These were found to be an
3
enthalpy of 76.1 kJ/mol and an entropy of 168.1 J/(mol K). For
3
an additional comparison it is noted that the ΔH and ΔS for the
monomerꢀdimer equilibrium for the species (2-PyCH2BCy2)2
and 2-PyCH2BCy2 were determined to be 79.2 kJ/mol and
218 J/(mol K).40 The lower values in the present system were
3
1
The H resonance at 2.82 ppm is attributed to the methylene
attributed to lower Lewis acidity of the boron center in 1 in
comparison to B(C6F5)3 and the poorer basicity of S in com-
parison to the PyꢀN.
group of a monomeric form in which rapid inversion at S occurs
via dissociation and BꢀS bond re-formation. On the other
hand, the quartet for this methylene group that grows in on
cooling is attributable to a dimeric form of 1. Further cooling
slows the exchange between chair and boat forms (Scheme 2).
This interpretation is also consistent with the 19F and 11B data.
Compound 1 reacts with PtBu3 or OPEt3 to form adducts
PhSCH2B(C6F5)2(L) (L = PtBu3 2, OPEt3 3), which can be
isolated in 85% and 87% yield, respectively. The 11B NMR
resonances are observed as sharp signals at δ ꢀ7.2 and 0.61 ppm,
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Organometallics
ARTICLE
respectively, and the gaps between the para- and meta-fluorines
in the 19F{1H} NMR spectra are 4.3 and 5.1 ppm for 2 and 3,
respectively, which is consistent with a four-coordinate B center.
The 31P signals for 2 and 3 were observed at 68.4 and 76.9 ppm,
respectively. The formations of 2 and 3 demonstrate the stronger
donor ability of phosphine and phosphine-oxide in comparison
to thioether and are consistent with the accessibility of the
monomeric fragment of 1 in solution, despite the electrophilic
nature of the B center. These reactions, in which the dimer is
cleaved, are reminiscent of the reaction of (PhBrBCH2SMe)2
with Me2NSiMe3 to give the amido-borane PhB(CH2SMe)-
(NMe2) reported by Wagner and co-workers.38
Scheme 3
As 1 contains donor and acceptor sites in dynamic equilibri-
um, it is conceivable that this species could react as an FLP. A
number of reactions observed with previous FLPs were at-
tempted with 1. Compound 1 did not form a stoichiometric
adduct with PhCHdNtBu, suggesting the steric congestion
about the N-donor precluded adduct formation. However,
treatment of this possible FLP with H2 at 60 °C for 12 h led to
no reaction, in contrast to the reaction of B(C6F5)3 and imine
with H2, where hydrogenation of the imine has been reported.20
This observation is consistent with the reduced Lewis acidity of
the B center in 1 resulting from both the presence of the alkyl
substituent and the equilibrium between the monomeric and
dimeric form.
As FLPs have been shown to react with olefins6 and
alkynes,9,11 compound 1 was also tested for possible reactivity
with these substrates. 1 was found to be unreactive with 1ꢀhexene.
Interestingly, 1 does react with both terminal and internal
alkynes. The addition of the alkynes PhCCH, C4H9CCH,
PhCCC4H9, C2H5CCC2H5, and PhCCPh led to the formation
of the new species (PhSCH2B(C6F5)2)(R0CdCR) (R = H, R0 =
Ph 4, C4H9 5, R = Ph, R0 = C4H9 6, R = R0 = C2H5 7, Ph 8) in
1
yields in the range 70ꢀ92%. The H NMR spectra of these
products gave rise to two distinct doublets ranging from 2.39 to
3.73 ppm, corresponding to the inequivalent protons in the CH2
moiety. In the case of 4 and 5, proton resonances at 8.33 and
7.61 ppm, respectively, were attributable to the presence of an
alkenyl proton. 19F{1H} NMR data for 4ꢀ8 show two sets of
resonances derived from the ortho-, meta-, and para-fluorine
atoms, consistent with two inequivalent C6F5 rings. Sharp 11B
NMR resonances were observed in the range ꢀ8.3 to ꢀ6.1 ppm,
inferring the presence of anionic four-coordinate boron centers.
Collectively these data suggest cycloadditions of the thioether-
borane species 1 with the respective alkynes (Scheme 3). This
formulation was confirmed unambiguously by an X-ray crystal-
lographic study of 8 (Figure 3). The five-membered ring is a
zwitterion with a formal positive charge on S and an anionic
charge on B. Within the SꢀB cyclopentene ring the SꢀC bond
lengths in 8 are found to be 1.7887(14) and 1.8059(14) Å, while
the BꢀC bonds are 1.634(2) and 1.666(2) Å and the CdC bond
is 1.3462(19) Å, consistent with the presence of a double bond.
The angles at S and B within the ring are found to be 96.11(7)o
and 103.38(11)o. The remaining angles within the ring at C(1),
C(2), and (C3) are found to be 107.44(9)o, 116.53(12)o, and
113.62(10)o, respectively.
Figure 3. POV-ray depictions of 8. C: black, F: pink, B: yellow-green, S:
yellow.
is thought to proceed via initial interaction of the alkyne with the
boron center. Presumably the proximity of the nucleophilic sulfur
center to the Lewis acid-activated alkyne prompts the cyclization.
It is noteworthy that we have previously demonstrated that
thioethers and B(C6F5)3 act as FLPs to effect addition to
terminal alkynes, affording a trans-zwitterionic addition product
of the form R2SCPhdCH(B(C6F5)3.9,11 The present systems,
however, are shown to give rise to cis-addition products 4ꢀ8.
These systems are reminiscent of the products derived from the
thermally induced rearrangement reactions of the zwitterionic
species R2PHC(dCHR)AlR2(CCR) to give cyclopentene phos-
phonium aluminates very recently described by Uhl and co-
workers.41 In addition, it is noteworthy that five-membered rings
containing B and S have received only very limited attention.42
In conclusion, a new linked boronꢀsulfur species, PhSCH2B-
(C6F5)2, was shown to be a dimer in the solid state, although it
exists in equilibrium with the monomeric species in solution. As a
result, it reacts with donors to form classical Lewis acidꢀbase
adducts. It has also been demonstrated to react as an FLP with
alkynes to effect the formation of novel boronꢀsulfur hetero-
cyclopentenes. Current efforts are focused on developing new
reactivity of FLP systems.
Interestingly, these heterocycles proved to be thermally stable
even upon heating to 120 °C overnight. Moreover, in contrast to
previously observed addition reactions, in which phosphine and
borane add to alkynes, addition of phosphine to a mixture of 1 and
phenylacetylene resulted only in the isolation of heterocyclc sulfo-
nium-borate 4. The formation of these thioether-borane heterocycles
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’ EXPERIMENTAL SECTION
129.8 (s, m-C), 33.3 (s, CH2). Anal. Calcd for C19H7BF10S: C 48.75, H
1.51. Found: C 49.22, H 1.65. X-ray quality crystals of the dimer were
obtained from a concentrated solution of product in toluene and
bromobenzene at ꢀ38 °C. X-ray data: monoclinic P21/n, a =
8.1411(7) Å, b = 18.587(2) Å, c = 23.881(3) Å, β = 96.257(4)o, V =
3594.0(6) Å3, Z = 4, data (>2σ) = 4011, variables = 559, R1 = 0.0546,
wR2 = 0.1373, GOF = 1.015.
Synthesis of (PhSCH2B(C6F5)2(L) (L = PtBu3 2, OPEt3 3).
These compounds were prepared in an analogous manner, and thus only
one preparation is detailed. In a 20 mL scintillation vial with a stirbar in a
cold brass ring (ꢀ38 °C) 74.8 μmol of compound 1 and 74.8 μmol of
PtBu3 were weighed out. These compounds were dissolved in ca. 4 mL
of cold toluene (ꢀ38 °C) and stirred overnight. Subsequent evacuation
of solvent resulted in clear, colorless oils. Addition of cold pentane and
placement of the vial in the glovebox freezer overnight resulted in a white
precipitate.
General Considerations. All reactions were performed under dry,
oxygen-free atmospheres either in a nitrogen-filled Innovative Technol-
ogies glovebox or on a Schlenk line under nitrogen. All solvents used
were purchased from Caledon Laboratories and dried through a Pure-
Solve solvent system. All deuterated solvents were purchased from Acros
or Cambridge Isotope Laboratories. Deuterated solvents were dried
overnight with the corresponding drying agent (CaH2 for CD2Cl2,
CaH2 for C6D5Br, Na/Ph2CO for d8-toluene), then sonicated for half an
hour, and vacuum transferred into a dry 100 mL bomb charged with
activated 4 Å molecular sieves. Molecular sieves were activated by
storage overnight in an oven at 120 °C. Reagents were purchased from
Sigma Aldrich or Strem Chemicals and were stored in the glovebox
except for sulfur precursors (thioanisole, 2-bromothioanisole), which
were stored over 4 Å molecular sieves and kept inside the fumehood. A
400 MHz Bruker UltraShield spectrometer, a 400 MHz Bruker Avance
III automatic sample changer, or a 400 MHz Varian Mercury spectro-
2: 1H NMR (d8-toluene, 400 MHz): δ 7.37 (d, 2H, 3JHꢀH = 7.4 Hz, o-
H), 6.89ꢀ6.85 (m, 2H, m-H), 6.83ꢀ6.81 (m, 1H, p-H), 2.38 (d, 2H,
3JPꢀH = 16.4 Hz, CH2), 0.93 (d, 3JHꢀH = 13.3 Hz, 27 Hz, tBu). 19F{1H}
NMR (d8-toluene, 377 MHz): δ ꢀ129.6 (br m, 4F, o-F), ꢀ160.6 (t, 2F,
3JFꢀF = 20.6 Hz, p-F), ꢀ164.9 (m, 4F, m-F). 11B{1H} NMR (d8-toluene,
128 MHz): δ ꢀ7.2 (s). 31P{1H} NMR (d8-toluene, 162 MHz): δ 68.4
(s). 13C{1H} NMR partial (CD2Cl2, 100 MHz): δ 134.2 (s, m-C), 128.2
(s, o-C), 125.4 (s, p-C), 40.0 (d, 2JPꢀC = 31.2 Hz, C(CH3)3), 30.9 (br s,
CH2, C(CH3)3). Yield: 85%. Anal. Calcd for C31H34BF10PS: C 55.54, H
5.11. Found: C 54.92, H 5.70.
1
meter was used to perform H, 13C, 11B, 19F, and 31P NMR spectros-
copy. 1H, 13C, 11B{1H}, 19F{1H}, and 31P{1H} NMR resonances were
referenced internally to residual protonated solvent, deuterated solvent,
BF3 Et2O, 80% CFCl3, and 85% H3PO4, respectively. To aid in the
3
assignment of carbon atoms in the 13C{1H} NMR, Hꢀ C HSQC
experiments were carried out using conventional pulse sequences.
Chemical shifts (δ) are expressed in ppm and coupling constants (J)
in Hz. Elemental analyses were performed by the in-house service in the
Department of Chemistry at the University of Toronto.43
1
13
3: 1H NMR (CD2Cl2, 400 MHz): δ 7.28ꢀ7.25 (m, 2H, o-H),
7.25ꢀ7.21 (m, 2H, m-H), 7.07ꢀ7.03 (m, 1H, p-H), 2.74 (s, 2H,
CH2), 2.07ꢀ1.98 (m, 6H, CH2), 1.21ꢀ1.08 (m, 9H, CH3). 19F{1H}
NMR (CD2Cl2, 377 MHz): δ ꢀ134.7 (m, 4F, m-F), ꢀ160.1 (t, 2F,
3JFꢀF = 20.1 Hz, p-F), ꢀ165.2 (m, 4F, m-F). 11B{1H} NMR (CD2Cl2,
128 MHz): δ 0.61 (s). 31P{1H} NMR (CD2Cl2, 162 MHz): δ 76.9 (s).
13C{1H} NMR partial (CD2Cl2, 100 MHz): δ 141.9 (s, ipso C), 129.1 (s,
m-C), 126.4 (s, o-C), 124.5 (s, p-C), 28.2 (s, CH2), 18.3 (d, 1JPꢀC = 65.7 Hz,
Synthesis of (PhSCH2B(C6F5)2)2, 1. In a preweighed 50 mL
Schlenk flask with a stir bar, ca. 25 mL of Et2O was added via cannula. To
the reaction vessel was added via a needle 0.30 mL of 2-bromothioani-
sole (2.25 mmol) (alternatively thioanisole can be used) under a
constant flow of N2 gas. The flask was then submerged in an acetone/
dry ice bath, and the contents were stirred for a few minutes to allow for
the temperature to equilibrate to ꢀ78 °C. nBuLi (1.55 mL of 1.6 M in
hexanes, 2.47 mmol) was added dropwise to the cold solution using a
needle and syringe. The reaction was allowed to stir for 2 h, during which
the clear, colorless solution turned milky. The volatiles were evacuated,
and the contents were dried under vacuum. To this lithiated species
(0.241 g, 1.85 mmol) was added cold pentane (ca. 2 mL), and the
mixture was stirred. In a separate scintillation vial, ClB(C6F5)233 (0.704 g,
1.85 mmol) was weighed out and dissolved in cold pentane (ca. 10 mL).
The chloroborane solution was transferred to the vial with the lithiated
compound and stirred overnight while warming gradually to room
temperature. The reaction mixture was filtered and the precipitate
extracted into toluene. Removal of the solvent afforded a fine white
2
CH2), 5.8 (d, JPꢀC = 4.7 Hz, CH3). Yield: 87%. Anal. Calcd for
C25H22BF10OPS: C 49.86, H 3.68. Found: C 51.01, H 4.14.
Synthesis of (PhSCH2B(C6F5)2(R0CdCR) (R = H, R0 = Ph 4,
C4H9 5, R = Ph, R0 = C4H9 6, R = R0 = C2H5 7, Ph 8). These
compounds were prepared in a similar fashion, and thus only one
preparation is detailed. In a 20 mL scintillation vial with a stir bar in a
cold brass ring (ꢀ38 °C) compound 1 (64.1 μmol) was weighed out and
dissolved in cold toluene (ca. 4 mL, ꢀ38 °C). Alkyne (64.1 μmol)
was added to the vial via a 0.50 cm3 syringe. The solution was stirred
overnight, and subsequent evacuation of solvent resulted in clear, color-
less oils. Addition of cold pentane and placement of the vial in the
glovebox freezer overnight resulted in a white to off-white precipitate.
4: 1H NMR (d8-toluene, 400 MHz): δ 8.33 (s, 1H, CH), 7.08ꢀ7.06
(m, 2H, o-H), 6.88 (d, 2H, 3JHꢀH = 7.5 Hz, o-H), 6.84ꢀ6.79 (m, 3H, m-
H, p-H), 6.64ꢀ6.60 (m, 1H, p-H), 6.56ꢀ6.52 (m, 2H, m-H), 3.46 (d,
1
powder (1) in 32% yield. H NMR (d8-toluene, 400 MHz, 25 °C): δ
6.72 (d, 2H, 3JHꢀH = 7.8 Hz, o-H), 6.59ꢀ6.55 (m, 3H, m-H, p-H), 2.82
(s, 2H, CH2). 1H NMR (d8-toluene, 400 MHz, ꢀ60 °C): δ 6.80 (d, 2H,
3JHꢀH = 7.2 Hz, o-H), 6.52 (t, 1H, 3JHꢀH = 7.2 Hz, p-H), 6.36 (t, 2H,
3JHꢀH = 7.2 Hz, m-H), 3.47 (s, 2H, CH2). 1H NMR (d8-toluene,
400 MHz, 55 °C): δ 6.78ꢀ6.77 (d, 2H, 3JHꢀH = 8.0 Hz, o-H), 6.64ꢀ6.59
(m, 3H, m-H, p-H), 2.87 (s, 2H, CH2). 19F{1H} NMR (d8-toluene,
377 MHz, 25 °C): δ ꢀ130.7 (m, 4F, o-F), ꢀ153.6 (t, 2H, 3JFꢀF = 20.4
Hz, p-F), ꢀ163.0 (m, 4F, m-F). 19F{1H} NMR (d8-toluene, 377 MHz,
ꢀ60 °C): δ ꢀ126.3 (m, 1F, o-F), ꢀ128.7 (m, 1F, o-F), ꢀ132.1 (d, 1F,
2
2
1H, JHꢀH = 13.6 Hz, CH2), 2.60 (d, 1H, JHꢀH = 13.6 Hz, CH2).
19F{1H} NMR (d8-toluene, 377 MHz): δ ꢀ132.6(d, 2F, 3JFꢀF = 24.2 Hz,
o-F), ꢀ133.5 (d, 2F, 3JFꢀF = 24.2 Hz, o-F), ꢀ159.3 (t, 1F, 3JFꢀF = 20.2
Hz, p-F), ꢀ159.5 (t, 1F, 3JFꢀF = 20.2 Hz, p-F), ꢀ163.7 (m, 2F, m-F),
ꢀ164.0 (m, 2F, m-F). 11B{1H} NMR (d8-toluene, 128 MHz): δ ꢀ7.8
(s). 13C{1H} NMR partial (CD2Cl2, 100 MHz): δ 133.7 (s, p-C), 131.5
(s, ipso C), 131.2 (s, m-C), 129.9 (s, o-C), 129.5 (s, m-C, p-C), 129.3 (s,
ipso C), 127.2 (s, o-C), 39.4 (s, CH2). Yield: 88%. Anal. Calcd for
C27H13BF10S: C 56.87, H 2.30. Found: C 56.03, H 2.71.
3JFꢀF = 24.3 Hz, o-F), ꢀ132.4 (d, 1F, JFꢀF = 24.3 Hz, o-F), ꢀ153.7
3
3
3
(t, 1F, JFꢀF = 21.7 Hz, p-F), ꢀ153.8 (t, 1F, JFꢀF = 21.7 Hz, p-F),
ꢀ161.8 (m, 1F, m-F), ꢀ162.2 (m, 1F, m-F), ꢀ162.5 (m, 1F, m-F),
ꢀ162.6 (m, 1F, m-F). 19F{1H} NMR (d8-toluene, 377 MHz, 55 °C):
δ ꢀ130.5 (m, 4F, o-F), ꢀ153.7 (t, 2H, 3JFꢀF = 20.4 Hz, p-F), ꢀ163.1
(m, 4F, m-F). 11B{1H} NMR (d8-toluene, 128 MHz, 25 °C): δ 5.1 (s).
11B{1H} NMR (d8-toluene, 128 MHz, 55 °C): δ 0.92 (br s). 11B{1H}
NMR (d8-toluene, 128 MHz, ꢀ60 °C): not observed. 13C{1H} NMR
partial (CD2Cl2, 100 MHz, 25 °C): δ 130.7 (s, p-C), 129.9 (s, o-C),
5: 1H NMR (d8-toluene, 400 MHz): δ 7.61 (s, 1H, CH), 6.96 (d, 2H,
3JHꢀH = 7.6 Hz, o-H), 6.85 (t, 1H, 3JHꢀH = 7.6 Hz, p-H), 6.76 (t, 2H,
3JHꢀH = 7.6 Hz, m-H), 3.57 (d, 1H, 2JHꢀH = 11.8 Hz, CH2), 2.49 (d, 1H,
2JHꢀH = 11.8 Hz, CH2), 1.87ꢀ1.79 (m, 1H, CCH2CH2), 1.63ꢀ1.55
(m, 1H,, CCH2CH2), 1.24ꢀ1.16 (m, 2H,, CCH2CH2), 1.06ꢀ0.89
3
(m, 2H, CH2CH3), 0.65 (t, 3H, JHꢀH = 7.2 Hz, CH3). 19F{1H}
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ARTICLE
3
NMR (d8-toluene, 377 MHz): δ ꢀ132.9 (d, 2F, JFꢀF = 19.3 Hz,
o-F), ꢀ133.6 (d, 2F, 3JFꢀF = 19.3 Hz, o-F), ꢀ159.6 (t, 1F, 3JFꢀF = 20.4
Hz, p-F), ꢀ159.7 (t, 1F, 3JFꢀF = 20.4 Hz, p-F), ꢀ163.9 (m, 2F, m-F),
ꢀ164.0 (m, 2F, m-F). 11B{1H} NMR (d8-toluene, 128 MHz): δ ꢀ8.3
(s). 13C{1H} NMR partial (CD2Cl2, 100 MHz): δ 135.6 (s, ipso C),
134.0 (s, p-C), 131.3 (s, m-C), 130.4 (s, o-C), 129.9 (s, ipso C), 42.9
(s, CH2), 30.8 (s, CCH2CH2), 30.7 (s, CCH2CH2), 22.4 (s, CH2CH3),
14.0 (s, CH3). Yield: 91%. Anal. Calcd for C25H17BF10S: C 54.57, H
3.11. Found: C 52.79, H 3.37.
collected at 150((2) K for all crystals. The frames were integrated with
the Bruker SAINT software package using a narrow-frame algorithm.
Data were corrected for absorption effects using the empirical multiscan
method (SADABS). Non-hydrogen atomic scattering factors were
taken from the literature tabulations.44 The heavy atom positions were
determined using direct methods employing the SHELXTL direct
methods routine. The remaining non-hydrogen atoms were located
from successive difference Fourier map calculations. The refinements
were carried out by using full-matrix least-squares techniques on F,
minimizing the function w(Fo ꢀ Fc)2, where the weight w is defined as
6: 1H NMR (CD2Cl2, 400 MHz): δ 7.63ꢀ7.61 (m, 2H, o-H),
7.53ꢀ7.49 (m, 1H, p-H), 7.48ꢀ7.44 (m, 2H, m-H), 7.31ꢀ7.28 (m,
2H, o-H), 7.28ꢀ7.26 (m, 2H, m-H), 7.24ꢀ7.20 (m, 1H, p-H), 3.73 (d,
1H, 2JHꢀH = 13.2 Hz, CH2), 2.68ꢀ2.62 (m, 1H, CCH2CH2), 2.45 (d,
1H, 2JHꢀH = 13.2 Hz, CH2), 2.41ꢀ2.34 (m, 1H, CCH2CH2), 0.92ꢀ0.86
(m, 2H, CCH2CH2), 0.84ꢀ0.74 (m, 1H, CH2CH3), 0.51 (t, 3H, CH3),
0.41ꢀ0.40 (m, 1H, CH2CH3). 19F{1H} NMR (d8-toluene, 377 MHz):
δ ꢀ132.6 (m, 2F, o-F), ꢀ133.0 (m, 2F, o-F), ꢀ159.5 (t, 1F, 3JFꢀF = 20.3 Hz,
p-F), ꢀ159.6 (t, 1F, 3JFꢀF = 20.3 Hz, p-F), ꢀ163.8 (m, 2F, m-F), ꢀ163.9
(m, 2F, m-F). 11B{1H} NMR (d8-toluene, 128 MHz): δ ꢀ6.1 (s).
13C{1H} NMR partial (CD2Cl2, 100 MHz): δ 133.6 (s, p-C), 133.5 (s,
ipso C), 132.0 (s, ipso C), 131.6 (s, ipso C), 131.1 (s, m-C), 130.3 (s, o-C),
129.7 (s, o-C), 129.4 (s, p-C), 129.0 (s, m-C), 128.8 (s, ipso C), 127.1
(s, ipso C), 43.6 (s, CH2), 32.3 (s, CCH2), 31.3 (s, CH2CH3), 23.5
(s, CH2CH2CH2), 13.6 (s, CH3). Yield: 92%. Anal. Calcd for
C31H21BF10S: C 59.44, H 3.38. Found: C 57.72, H 3.65.
2
2
4Fo /2σ(Fo ) and Fo and Fc are the observed and calculated structure
factor amplitudes, respectively. In the final cycles of each refinement, all
non-hydrogen atoms were assigned anisotropic temperature factors in
the absence of disorder or insufficient data. In the latter cases atoms were
treated isotropically. CꢀH atom positions were calculated and allowed
to ride on the carbon to which they are bonded assuming a CꢀH bond
length of 0.95 Å. H atom temperature factors were fixed at 1.20 times the
isotropic temperature factor of the C atom to which they are bonded.
The H atom contributions were calculated, but not refined. The
locations of the largest peaks in the final difference Fourier map
calculation as well as the magnitude of the residual electron densities
in each case were of no chemical significance.
’ ASSOCIATED CONTENT
7: 1H NMR (CD2Cl2, 400 MHz): δ 7.67ꢀ7.64 (m, 2H, o-H),
S
Supporting Information. This material is available free of
b
7.64ꢀ7.62 (m, 1H, p-H), 7.60ꢀ7.55 (m, 2H, m-H), 3.55 (d, 1H, 2JHꢀH
=
charge via the Internet at http://pubs.acs.org.
12.9 Hz, CH2), 2.62 (sextet, 1H, 3JHꢀH = 7.7 Hz, CCH2), 2.52ꢀ2.47 (m,
2
’ AUTHOR INFORMATION
2H, CCH2), 2.39 (d, 1H, JHꢀH = 12.9 Hz, CH2), 1.83 (sextet, 1H,
3JHꢀH = 7.7 Hz, CCH2), 1.03 (t, 3H, 3JHꢀH = 7.7 Hz, CH2CH3), 0.64
(t, 3H, 3JHꢀH = 7.7 Hz, CH2CH3). 19F{1H} NMR (CD2Cl2, 377 MHz):
δ ꢀ132.6 (m, 2F, o-F), ꢀ133.2 (m, 2F, o-F), ꢀ159.7 (t, 1F, 3JFꢀF = 20.2 Hz,
p-F), ꢀ159.8 (t, 1F, 3JFꢀF = 20.2 Hz, p-F), ꢀ164.0 (m, 2F, m-F), ꢀ164.1
(m, 2F, m-F). 11B{1H} NMR (CD2Cl2, 128 MHz): δ ꢀ7.0 (s). 13C{1H}
NMR partial (CD2Cl2, 100 MHz): δ 133.8 (s, p-C), 131.3 (s, m-C),
130.4 (s, o-C), 43.3 (s, CH2), 25.5 (s, CH2CH3), 21.3 (s, CH2CH3),
14.5 (s, CH2CH3), 13.1 (s, CH2CH3). Yield: 80%. Anal. Calcd for
C25H17BF10S: C 54.57, H 3.11. Found: C 53.28, H 3.28.
Corresponding Author
*E-mail: dstephan@chem.utoronto.ca.
’ ACKNOWLEDGMENT
Financial support of NSERC of Canada is gratefully acknowl-
edged. D.W.S. is grateful for the award of a Canada Research
Chair and a Killiam Research Fellowship for 2009ꢀ2011.
1
8: H NMR (CD2Cl2, 400 MHz): δ 7.75ꢀ7.73 (m, 2H, ArꢀH),
7.57ꢀ7.52 (m, 1H, ArꢀH), 7.52ꢀ7.48 (m, 2H, ArꢀH), 7.39ꢀ7.36 (m,
1H, ArꢀH), 7.15ꢀ7.12 (m, 2H, ArꢀH), 7.12ꢀ7.09 (m, 3H, ArꢀH),
7.06ꢀ7.00 (m, 2H, ArꢀH), 6.89ꢀ6.87 (m, 2H, ArꢀH), 3.81 (d, 1H,
2JHꢀH = 12.2 Hz, CH2), 2.76 (d, 1H, 2JHꢀH = 12.2 Hz, CH2). 19F{1H}
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