Frustrated Lewis pair behavior of intermolecular amine/B(C 6F5)3 pairs

Article abstract of DOI:10.1021/om300017u

Reactions of N,N-dimethylaniline, N-isopropylaniline, 1,4-C ₆H₄(CH₂NHtBu)₂, and benzyldimethylamine with the Lewis acid B(C₆F₅) ₃ have been studied. In the case of N,N-dimethylaniline the combination of the Lewis acid and base forms an almost completely noninteracting frustrated Lewis pair, while the corresponding reactions of N-isopropylaniline and benzyldimethylamine with B(C₆F₅)₃ afford the adducts (PhNHiPr)B(C₆F₅)₃ (1) and PhCH ₂NMe₂B(C₆F₅)₃ (2), respectively. 1,4-C₆H₄(CH₂NHtBu)₂ reacts with 2 equiv of B(C₆F₅)₃ to give rise to an inseparable mixture of the mono- and bis-amine-borane adducts as well as an iminium salt derived from hydride abstraction from a benzylic carbon of the diamine. Subsequent selected reactions of the Lewis acid/base combinations with H₂ afforded [PhNMe₂H][HB(C₆F₅) ₃] (3), [PhCH₂NMe₂H][HB(C₆F ₅)₃] (4), and [1,4-C₆H₄(CH ₂NH₂tBu)₂][HB(C₆F₅) ₃]₂ (5). Reactions with CO₂ gave PhCH ₂NMe₂CO₂B(C₆F₅) ₃ (6), [PhNiPrH₂][PhNiPrCO₂B(C ₆F₅)₃] (8), [1,4-C₆H ₄(CH₂NH₂tBu)(CH₂NtBuCO ₂B(C₆F₅)₃] (9), and [C ₅H₆Me₄NMeH]₂[1,4-C₆H ₄(CH₂NtBuCO₂B(C₆F₅) ₃)₂] (10). Interestingly, the species 4 also reacts with CO₂ to give [PhCH₂NMe₂H][HCO ₂B(C₆F₅)₃] (7). Species 8 reacts with HSiEt₃ to yield [PhNiPrC(OSiEt₃)OB(C ₆F₅)₃] (11). The adduct 2 also reacts with ethene, 2,4-hexadiyne, and the alkynes HC≡CR (R = n-Bu, Ph, tBu, SiMe ₃) to give the 1,2- addition products PhCH₂NMe ₂CH₂CH₂B(C₆F₅) ₃ (12), PhCH₂NMe₂C(CCMe)=CMeB(C ₆F₅)₃ (13), and the ammonium alkynylborate salts [PhCH₂NMe₂H][RCCB(C₆F₅) ₃] (R = n-Bu (14a), Ph (14b), tBu (14c), SiMe₃ (14d)). In contrast, the reaction of 1-hexyne with the Lewis pair PhNMe₂ and B(C₆F₅)₃ affords the trans-1,2-addition product PhNMe₂C(C₄H₉)=CH(B(C₆F ₅)₃) (15). This chemistry demonstrates the generality of such FLP chemistry, extending it to N-based Lewis bases and thereby expanding the scope for applications of FLP chemistry.

Full text of DOI:10.1021/om300017u

Article
pubs.acs.org/Organometallics
Frustrated Lewis Pair Behavior of Intermolecular Amine/B(C6F5)3
Pairs
Tanja Voss,†,‡ Tayseer Mahdi,‡ Edwin Otten,‡ Roland Frohlich,† Gerald Kehr,† Douglas W. Stephan,*,‡
̈
and Gerhard Erker*,†
†Organisch-Chemisches Institut der Universitat Munster, Corrensstrasse 40, 48149 Munster, Germany
̈
̈
̈
‡Department of Chemistry, University of Toronto, 80 St. George St. Toronto, Ontario M5S 3H6, Canada
S
* Supporting Information
ABSTRACT: Reactions of N,N-dimethylaniline, N-isopropyl-
aniline, 1,4-C6H4(CH2NHtBu)2, and benzyldimethylamine
with the Lewis acid B(C6F5)3 have been studied. In the case
of N,N-dimethylaniline the combination of the Lewis acid and
base forms an almost completely noninteracting frustrated
Lewis pair, while the corresponding reactions of N-
isopropylaniline and benzyldimethylamine with B(C6F5)3
afford the adducts (PhNHiPr)B(C6F5)3 (1) and
PhCH2NMe2B(C6F5)3 (2), respectively. 1,4-C6H4-
(CH2NHtBu)2 reacts with 2 equiv of B(C6F5)3 to give rise to an inseparable mixture of the mono- and bis-amine−borane
adducts as well as an iminium salt derived from hydride abstraction from a benzylic carbon of the diamine. Subsequent selected
reactions of the Lewis acid/base combinations with H2 afforded [PhNMe2H][HB(C6F5)3] (3), [PhCH2NMe2H][HB(C6F5)3]
(4), and [1,4-C6H4(CH2NH2tBu)2][HB(C6F5)3]2 (5). Reactions with CO2 gave PhCH2NMe2CO2B(C6F5)3 (6), [PhNiPrH2]-
[PhNiPrCO2B(C6F5)3] (8), [1,4-C6H4(CH2NH2tBu)(CH2NtBuCO2B(C6F5)3] (9), and [C5H6Me4NMeH]2[1,4-
C6H4(CH2NtBuCO2B(C6F5)3)2] (10). Interestingly, the species 4 also reacts with CO2 to give [PhCH2NMe2H][HCO2B-
(C6F5)3] (7). Species 8 reacts with HSiEt3 to yield [PhNiPrC(OSiEt3)OB(C6F5)3] (11). The adduct 2 also reacts with ethene,
2,4-hexadiyne, and the alkynes HCCR (R = n-Bu, Ph, tBu, SiMe3) to give the 1,2- addition products PhCH2NMe2CH2CH2B-
(C6F5)3 (12), PhCH2NMe2C(CCMe)=CMeB(C6F5)3 (13), and the ammonium alkynylborate salts [PhCH2NMe2H][RCCB-
(C6F5)3] (R = n-Bu (14a), Ph (14b), tBu (14c), SiMe3 (14d)). In contrast, the reaction of 1-hexyne with the Lewis pair PhNMe2
and B(C6F5)3 affords the trans-1,2-addition product PhNMe2C(C4H9)=CH(B(C6F5)3) (15). This chemistry demonstrates the
generality of such FLP chemistry, extending it to N-based Lewis bases and thereby expanding the scope for applications of FLP
chemistry.
those with α-C−H bonds, in FLP type reactivity appears to be
more complicated than the more common P/B cases.
Complications arise from competing reaction pathways that
are specifically open to amines, such as α-C−H abstraction by
the Lewis acid.21 Indeed, this reaction has been shown to
interfere with typical FLP chemistry in ferrocenophane-derived
systems. While the small NMe2 group of the ferrocenophanes
and B(C6F5)3 undergo cooperative FLP addition to the
adjacent pendant alkenyl group at low temperatures, this
reaction is reversed at higher temperatures, prompting
formation of the corresponding iminium species.22 In this
paper, we describe studies of FLP chemistry employing several
N/B pairs. These simple systems are shown to exhibit typical
FLP chemistry, reacting with H2, CO2, olefins, alkynes, and
diynes. This chemistry demonstrates the extension of FLP
chemistry to N-based Lewis bases and thereby expanding the
scope for applications.
INTRODUCTION
■
The chemistry of frustrated Lewis pairs (FLPs) has seen
significant development in recent years.1 This has mostly been
based on bulky phosphine−borane pairs, the later being
predominantly derived from C6F5-substituted systems.2 This
has resulted in well-established pathways of metal-free
heterolytic H2 activation2,3 and the catalytic hydrogenation of
various polar substrates.4 Phosphine-based FLPs have also been
shown to heterolytically cleave B−H bonds5 and disulfides,6
ring open THF, cyclic ethers, and lactones,7 and add to CO2,8
alkenes,9 dienes,10 alkynes,11 conjugated enynes, diynes,12
organic carbonyl compounds,13 and azides14 as well as CO,15
N2O,16 and NO.17 In contrast, the corresponding chemistry
utilizing amine−borane FLP systems is less explored. The
activation of H2 by the combination of tetramethylpiperidine,18
1,4-diazabicyclo(2,2,2)octane,19 or pyridines20 with boranes has
been demonstrated and employed in FLP-catalyzed hydro-
genations of imines, enamines, and silyl enol ethers. In addition,
these N/B FLPs have been employed to activate H2 or silane
and effect the reduction of CO2 to methanol or methane,
respectively.8e The utilization of smaller amines, especially
Received: January 9, 2012
Published: March 7, 2012
© 2012 American Chemical Society
2367
dx.doi.org/10.1021/om300017u | Organometallics 2012, 31, 2367−2378

Organometallics
Article
is thought to arise from hydride abstraction from the amine,
generating the salt [PhNHCMe2][HB(C6F5)3] by analogy to
known systems (Scheme 1b).
RESULTS AND DISCUSSION
■
Amine−Borane Adduct Formation. The reaction of N,N-
dimethylaniline with B(C6F5)3 has been previously studied. We
found the same results as described in the literature;21b namely,
formation of a product mixture characterized by 11B NMR
signals at ca. 63, −2, and −24 ppm, when B(C6F5)3 was treated
with the aniline derivative employed as purchased. In contrast,
mixing of carefully purified N,N-dimethylaniline with B(C6F5)3
under rigorous dry conditions did not lead to any appropriate
reaction being observed. Monitoring the NMR features of the
mixture of components in C7D8 revealed a broad 11B NMR
signal at ca. 60 ppm and 19F NMR resonances at −128.8,
−142.0, and −160.2 ppm (see the Supporting Information). It
seems that PhNMe2 and B(C6F5)3 form an almost non-
interacting FLP under these conditions (Scheme 1a).23
In a similar sense, the corresponding reaction of 1,4-
C6H4(CH2NHtBu)2 with 2 equiv of B(C6F5)3 gave rise to an
inseparable mixture of two species, as evidenced by two 11B
NMR signals. A broad signal at −3 ppm and a sharp doublet at
−24 ppm appear in a 2:1 ratio. The chemical shift of the former
signal is consistent with a mixture of mono- and bis-amine−
borane adducts. The high-field signal is attributable to the anion
[HB(C6F5)3]− arising from the generation of [1,4-
C6H4(CH2NHtBu)(CHNHtBu)][HB(C6F5)3] (Scheme 1c).
The reaction of the nucleophilic benzyldimethylamine with
the Lewis acid B(C6F5)3 results in the formation of the weak
adduct 2 (Scheme 1d). This was evident from an upfield shift
of the 11B NMR signal to about 46 ppm (C7D8) as well as the
19F NMR signals to −128.0, −145.7, and −161.0 ppm. Single
crystals of adducts 1 and 2 were characterized by X-ray
diffraction (Figure 1). The X-ray crystal structure analyses
Scheme 1. Reactions of Amines with B(C6F5)3
Figure 1. POV-ray depictions of (a) 1 and (b) 2. Color codes: C,
black; N, blue-green; B, yellow-green; F, pink; H, gray. Only the NH
hydrogen atom is shown.
confirmed the formulations of these adducts. In the case of 1
the B−N bond distance was found to be 1.686(3) Å, whereas
the B−N linkage in 2 is rather long at 1.807(3) Å,20a,24
although the boron and the nitrogen atoms of both structures
adopt pseudotetrahedral coordination geometries. The signifi-
cant difference in the B−N distances is interesting, given that
one might expect benzyldimethylamine to be more basic than
N-isopropylaniline. Nonetheless, it is clear that the steric
congestion about the tertiary amine center precludes a closer
approach of N to B.
The above examples demonstrate the influence of both steric
and electronic factors on the formation of classical Lewis
adducts by amines and B(C6F5)3. While such factors may
“frustrate” the adduct formation, they provide equilibrium
access to the free FLPs for subsequent reactivity. Moreover, the
hydridophilic nature of the borane also generates the possibility
of minor side products derived from hydride abstraction from
the α-C to generate iminium salts.
The corresponding reaction of N-isopropylaniline and
1
B(C6F5)3 in C6D5Br resulted in broad H, 11B, and 19F NMR
signals at 25 °C. On cooling to −80 °C, the mixture exhibited a
11B NMR signal at ca. −3 ppm and the 19F NMR spectrum
exhibited 14 resonances consistent with inequivalent fluoroaryl
groups (two o-F overlapping). The corresponding low-
1
temperature H NMR spectrum revealed inequivalent methyl
resonances at 1.23 and 0.72 ppm. These data were consistent
with the formation of the adduct (PhNHiPr)B(C6F5)3 (1).
Repetition of this reaction in pentane instantly yielded 1,
permitting its isolation. In the 11B NMR spectrum, about 10%
of the material gives rise to a signal at −23.6 ppm, consistent
with the formation of the anion [HB(C6F5)3]−.2b This species
2368
dx.doi.org/10.1021/om300017u | Organometallics 2012, 31, 2367−2378

Organometallics
Article
Reactions with Dihydrogen. The N,N-dimethylaniline−
B(C6F5)3 Lewis pair reacted rapidly with H2 (4 atm) at 25 °C,
despite the low basicity of the Lewis base component, to effect
the heterolytic cleavage of H2 and yield the ammonium−
hydridoborate salt [PhNMe2H][HB(C6F5)3] (3) (Scheme 2).
ppm attributable to the NH proton as well as a singlet at 2.72
ppm attributable to two N-bound methyl groups. The
corresponding IR bands for 3 are observed at νNH 3060 cm−1
and νBH 2311 cm−1. The same reaction with D2 afforded 3-d2,
as evidenced by the observation of 2H NMR resonances
attributable to the ND and BD moieties. In addition, some
deuteration of the aromatic ring of the [PhNMe2D]+ cation was
also observed (see the Supporting Information).
Scheme 2. Reactions of Amine−B(C6F5)3 with H2
In C6D5Br, adduct 2 reacts slowly at 25 °C with H2 (4 atm)
to give the salt [PhCH2NMe2H][HB(C6F5)3] (4) (Scheme 2
and Figure 2). The reaction was complete on standing for 3
days to afford 4 in 88% isolated yield. This species gives rise to
typical NMR features of the anion, while the cation shows a
1
methylene H NMR resonance at 3.52 ppm and a methyl
singlet at 2.25 ppm. The corresponding experiment with D2
2
gave the analogous salt 4-d2, which exhibited H NMR signals
at 7.35 ppm (ND) and 3.23 ppm (BD). The formulation of 4
was also confirmed by X-ray diffraction (Figure 2b).
In the case of the diamine 1,4-C6H4(CH2NHtBu)2, treatment
with 2 equiv of B(C6F5)3 in toluene and exposure to H2 (4
atm) resulted in the formation of a precipitate at 25 °C.
Subsequent isolation of the residue afforded a quantitative yield
of the salt [1,4-C6H4(CH2NH2tBu)2][HB(C6F5)3]2 (5). The
1H NMR spectrum of 5 showed a broad signal at 5.95 ppm
1
attributable to the NH2 fragment, while the H, 19F, and 11B
NMR spectra confirmed the presence of the borate anion. The
formulation of 5 was confirmed unambiguously by X-ray
diffraction (Figure 3). The metric parameters are unexcep-
tional.
Product 3 was subsequently isolated in near-quantitative yield,
and crystals were obtained from pentane−dichloromethane at
−32 °C. The metric parameters were unexceptional, and typical
pseudotetrahedral geometries about N and B were observed
1
(Figure 2a). The 11B, H, and 19F NMR spectra confirm the
formation of the hydridoborate anion.2b The corresponding
[PhNMe2H]+ cation shows a sharp 1H NMR resonance at 8.60
Figure 3. POV-ray depiction of 5. Color code: C, black; N, blue-green;
B, yellow-green; F, pink; H, gray. Only one of borate anions and only
the BH and NH hydrogen atoms are shown.
Reactions with Carbon Dioxide. We have previously
shown that P-based FLPs react with carbon dioxide to yield the
respective addition products in which P and B add to a C−O
bond in CO2. In this fashion, tBu3PCO2B(C6F5)3 and
Mes2P(CO2)CH2CH2B(C6F5)2 were characterized.8a Subse-
quently, we also described a series of related P/B-FLP-CO2
species.8e In all cases, these species were shown to be thermally
labile, liberating CO2 rapidly at temperatures between −20 and
Figure 2. POV-ray depictions of (a) 3 and (b) 4. Color code: C, black;
N, blue-green; B, yellow-green; F, pink; H, gray. Only the BH and NH
hydrogen atoms are shown.
2369
dx.doi.org/10.1021/om300017u | Organometallics 2012, 31, 2367−2378

Organometallics
Article
+80 °C in solution. In a similar fashion, the reactions of
amine−borane species were probed. While primary and
secondary amines are known to react with CO2 to generate
carbamates,25 PhCH2NMe2 appears to be unreactive with
CO2.26 However, the mixture of PhCH2NMe2 with B(C6F5)3
(i.e., 2) reacted slowly with CO2 in C6H5Br or toluene solution
at low temperature (−32 °C) over a period of 12 h to yield the
thermolabile addition product 6 (Scheme 3). While this system
with the observed 13C NMR carbonyl resonance of 6 (150.1
ppm), which has shifted upfield by about 10 ppm toward the
value for free CO2 (125 ppm), suggesting a stronger CO
bond in 6. This is also consistent with the observed increase of
the IR ν(CO) stretching band in 6 (1822 cm−1), which is
markedly closer to the asymmetric stretching band of CO2
(2345 cm−1) than the CO groups in related P/B CO2
derivatives.8a
The species 4 also reacts with CO2 at 80 °C to give the
ammonium borylformate salt 7, which was isolated as a white
solid from the reaction mixture in 90% yield (Scheme 3). The
presence of the formate moiety is evidenced by the signal at
Scheme 3. Reactions with CO2
1
8.29 ppm in the H NMR spectrum and at 170.2 ppm in the
13C NMR spectrum. This anion gives rise to a 11B NMR signal
at −2.2 ppm and 19F NMR resonances at −134.2, −157.9, and
−164.3 ppm as well as an IR ν(CO) stretching band at 1621
cm−1. Compound 7 was independently synthesized by
treatment of the FLP adduct 2 with formic acid and
characterized by X-ray diffraction (Figure 5). Compound 7
Figure 5. POV-ray depiction of 7. Color code: C, black; N, blue-green;
B, yellow-green; O, red; F, pink; H, gray. Only COH and NH
hydrogen atoms are shown.
releases CO2 rapidly in solution (CH2Cl2) above ca. −20 °C,
the product 6 was isolable in 54% yield at low temperature.
Single-crystal X-ray diffraction of compound 6 revealed amine
N binding to the C of CO2 with O binding to B(C6F5)3 (Figure
4). The N−C and B−O bond lengths were found to be
features a B−O bond length of 1.535(3) Å and a CO double
bond of 1.213(5) Å, which are both slightly shorter than the
respective bonds in the related system [C5H6Me4NH2]-
[HCO2B(C6F5)3] (B−O = 1.546(3) Å, CO = 1.236(3)
Å).27−29
Following a similar reaction strategy, a mixture of N-
isopropylaniline and B(C6F5)3 was exposed to 13CO2 (1 atm).
After the mixture was stirred at 25 °C for 2 days, workup led to
the isolation of the product 8 as a white powder in 95% yield.
1
The H NMR spectrum of 8 shows a resonance at 7.55 ppm
attributable to an NH2 fragment as well as two sets of
resonances for isopropyl groups. These data, in addition to the
19F and 11B NMR spectra, were consistent with the formation
of a borate, while the 13C NMR signal at 159.4 ppm was
attributed to the N-bound CO2 moiety. In addition to these
NMR features, the IR absorption at 1646 cm−1 (using 13CO2)
was consistent with the formulation of 8 as [PhNiPrH2]-
[PhNiPrCO2B(C6F5)3]. This was confirmed crystallographi-
cally (Figure 6). The N−C and B−O bond distances associated
with the NCO2B fragment 8 were found to be 1.355(3) and
1.508(3) Å, respectively.
The closely related product [1,4-C6H4(CH2NH2tBu)-
(CH2NtBuCO2B(C6F5)3)] (9) was derived from the corre-
sponding reaction of the diamine 1,4-C6H4(CH2NHtBu)2 with
B(C6F5)3 and CO2 (Scheme 4). This zwitterionic salt was
isolated in 88% yield and exhibited spectral parameters
Figure 4. POV-ray depiction of 6. Color code: C, black; N, blue-green;
B, yellow-green; O, red; F, pink. Hydrogen atoms are not shown.
1.545(2) and 1.550(2) Å, respectively. The carbamate-like core
of the molecule features a trigonal-planar carbon atom with
pertinent bond angles of 133.06(18)° (O−C−O) and
118.04(17) and 108.85(16)° (N−C−O). The C−O−B angle
is 121.54(15)°, while the angles about N are typical of a
pseudotetrahedral coordination geometry.
The CO bond in the adduct 6 is short (C−O = 1.193(3)
Å); indeed markedly shorter than those observed in the related
and previously reported P/B-FLP adducts.8a This corresponds
2370
dx.doi.org/10.1021/om300017u | Organometallics 2012, 31, 2367−2378

Organometallics
Article
Figure 6. POV-ray depiction of 8. Color code: C, black; N, blue-green;
B, yellow-green; F, pink; O, red. Hydrogen atoms are not shown.
Figure 8. POV-ray depiction of the dianion of 10. Color code: C,
black; N, blue-green; B, yellow-green; F, pink; O, red. Hydrogen atoms
are not shown.
Scheme 4. Reactions of Diamine with CO2 and B(C6F5)3
NCO2B fragment are in the range of those for 8 and 10 (N−C
= 1.380(5) Å, B−O = 1.508(5) Å).
Piers and co-workers have previously shown that the
formatoborate salt [TMPH][HC(O)OB(C6F5)3] reacts with
silane, ultimately giving CH4, with (Et3Si)2O.27b For compar-
ison, species 8 was reacted with HSiEt3, giving rise to the new
species 11, which was isolated in 64% yield (Scheme 3). The
1H NMR spectrum of 11 was consistent with the loss of the
NH2 protons of the cation of 8 and showed the presence of the
SiEt3 fragment. The 19F and 11B NMR spectra revealed signals
at −135.0, −160.0, −165.3, and −3.98 ppm, respectively. The
13C NMR resonance at 156.4 ppm was consistent with the
incorporation of 13CO2. Collectively, these data were consistent
with the formulation of 11 as [PhNiPrC(OSiEt3)OB(C6F5)3]
and the concurrent evolution of H2. Compound 11 was
subsequently confirmed crystallographically (Figure 9). The
Figure 9. POV-ray depiction of 11. Color code: C, black; N, blue-
green; B, yellow-green; F, pink; O, red; Si, orange. Hydrogen atoms
are not shown.
N−C distance in 11 was found to be 1.327(3) Å, similar to that
in 8−10, while the B−O distance is elongated slightly to
1.557(3) Å and the Si−O distance to 1.706(2) Å. Interestingly,
efforts to effect similar reactions of 9 with HSiEt3 were
unsuccessful. At 25 °C, multinuclear NMR data revealed no
reaction between HSiEt3 and 9, whereas heating to 80 °C
resulted only in the liberation of CO2. The differing reactivities
of 8 and 9 are attributed to increased steric congestion adjacent
to the CO2 fragment and the decreased acidity of the
ammonium fragment in 9, which combine to preclude silylation
and evolution of H2.
Reactions with Alkenes and Alkynes. We have
previously demonstrated that P/B FLPs add to alkenyl or
alkynyl fragments. Amine-based FLPs have been shown to
exhibit intramolecular additions of amines to alkenyl or alkynyl
substituents in the presence of B(C6F5)3.30 The adduct 2 reacts
slowly with ethene (2 atm) in pentane at 25 °C to yield the 1,2-
Figure 7. POV-ray depiction of 9. Color code: C, black; N, blue-green;
B, yellow-green; F, pink; O, red; H, gray. Only the NH hydrogen atom
is shown.
analogous to those of 8. The nature of this species was also
confirmed crystallographically (Figure 7). The N−C and B−O
distances associated with the NCO2B fragment were found to
average 1.364(6) and 1.496(6) Å, respectively. Repetition of
this reaction in the presence of 2 equiv of 1,2,2,6,6-
pentamethylpiperidine resulted in isolation of the salt
[C5H6Me4NMeH]2[1,4-C6H4(CH2NtBuCO2B(C6F5)3)2]
(10). Both amine fragments of the precursor diamine have
reacted with CO2 and the borane forms the dianion, while the
more basic pentamethylpiperidine forms the corresponding
cations. The structure of 10 was determined crystallographically
(Scheme 4 and Figure 8). The N−C and B−O distances of the
2371
dx.doi.org/10.1021/om300017u | Organometallics 2012, 31, 2367−2378

Organometallics
Article
FLP addition product PhCH2NMe2CH2CH2B(C6F5)3 (12).
This product was isolated in 57% yield (Scheme 5). The X-ray
corresponding reaction of the intramolecular P/B-FLP
Mes2PCH2CH2B(C6F5)2, which results in 1,4-addition, yielding
a heterocyclic eight-membered 1,2,3-butatriene derivative.12
The X-ray crystal structure analysis of 13 (Figure 11)
Scheme 5. Reactions of 2 with Ethene and Diyne
Figure 11. POV-ray depiction of 13. Color code: C, black; N, blue-
green; B, yellow-green; F, pink. Hydrogen atoms are not shown.
confirmed the regioselective trans-1,2-addition of the N/B-
FLP 2 to one of the carbon−carbon triple bonds, giving rise to
the tetrasubstituted Z-configured olefinic subunit with a C−C
bond length of 1.345(3) Å.
The analogous reaction of 2 with the terminal alkynes HC
CR (R = n-Bu, Ph, tBu, SiMe3) resulted in deprotonation of the
alkynes, affording the corresponding ammonium alkynylborate
salts [PhCH2NMe2H][RCCB(C6F5)3] (R = n-Bu (14a), Ph
(14b), tBu (14c), SiMe3 (14d)) (Scheme 6). Spectroscopically,
Figure 10. POV-ray depiction of 12. Color code: C, black; N, blue-
green; B, yellow-green; F, pink. Hydrogen atoms are not shown.
Scheme 6. Reactions with Terminal Alkynes
crystal structure analysis of 12 (Figure 10) confirmed the
addition reaction and revealed the new N−C and B−C bond
lengths of 1.518(3) and 1.666(4) Å, respectively. This
zwitterionic product adopts an antiperiplanar conformation of
the core atoms with a B1−C1−C2−N3 dihedral angle of
172.92(5)° and a C1−C2 bond length of 1.514(3) Å. In C6D6,
1
compound 12 exhibits H NMR signals for the methylene
groups at 2.31 (NCH2) and 1.55 (CH2B) ppm, while the
corresponding 13C NMR resonances were seen at 68.9 (NCH2)
and 15.6 (CH2B) ppm. The 11B NMR signal at −14.4 ppm is
typical of a borate, as is the Δδ(19Fp,m) of 4.2 ppm for the 19F
NMR resonances.
The N/B-FLP 2 reacts with the reagent 2,4-hexadiyne to
undergo regioselective addition, affording the trans-1,2-addition
product PhCH2NMe2C(CCMe)CMeB(C6F5)3 (13), which
was isolated in 52% yield as a white solid (Scheme 5). The 13
C
NMR spectrum of 13 shows a 1:1:1:1 quartet resonance at
156.6 ppm with a C−B coupling of about 52 Hz. This signal is
indicative of boron substitution at C2. The adjacent olefinic
carbon atom C3 gives rise to a 13C NMR resonance at 126.7
ppm, while the acetylenic carbons give rise to signals at 74.4
and 97.2 ppm. The corresponding 11B NMR resonance is seen
at −12.1 ppm. The observation of a total of 15 inequivalent 19F
NMR resonances at ambient temperature is consistent with the
hindered rotation around the B−C σ bonds. This conforma-
tional chirality results in diastereomeric environments for the
methyl groups and methylene hydrogens adjacent to nitrogen.
these species are similar. For example, 14a exhibits character-
istic 13C NMR resonances for the acetylenic carbon atoms at
101.3 and 96.1 ppm, with the former exhibiting typical coupling
of ca. 70 Hz to the adjacent boron atom, while the latter
exhibits a much smaller coupling value. The product 14a was
characterized by X-ray diffraction (Figure 12). This species
showed a new B−C bond length of 1.605(3) Å and alkynyl C−
C bond length of 1.199(4) Å (for 14a); otherwise, the metric
parameters are unexceptional. Such deprotonation of terminal
alkynes has been previously reported for basic phosphine-
s.11a−d,31
The analogous reaction of 1-hexyne with the PhNMe2/
B(C6F5)3 mixture in pentane at 25 °C overnight gave the
regioselective trans-1,2-addition product [PhNMe2C(C4H9)
CH(B(C6F5)3] (15), which was isolated in 50% yield after
recrystallization from dichloromethane/pentane at −32 °C. It
1
As a consequence, the methylene group gives rise to two H
NMR resonances at 4.59 and 4.46 ppm with a two-bond H, H
coupling constant of 13.1 Hz. The methyl groups on nitrogen
are inequivalent and show two signals at 3.36 and 3.27 ppm.
This reactivity with diyne stands in contrast to the
2372
dx.doi.org/10.1021/om300017u | Organometallics 2012, 31, 2367−2378

Organometallics
Article
are continuing to develop and apply the unique reactivity of
FLPs in synthetic chemistry and catalysis.
EXPERIMENTAL SECTION
■
General Considerations. All reactions involving air- and/or
moisture-sensitive compounds were carried out under an inert gas
atmosphere (Munster, argon purchased from Westfalen AG; Toronto,
̈
nitrogen) using Schlenk-type glassware and a glovebox (Munster,
̈
Glovebox 150 B-G II from MBraun; Toronto, glovebox from
Innovative Technology). All other manipulations were performed on
a double-manifold N2 (H2)/vacuum line with Schlenk-type glassware
or in an N2-filled inert-atmosphere glovebox. The N2 and H2 gases
were dried by passage through a Dririte column. Solvents (Aldrich)
were dried using an Innovative Technologies solvent system (toluene,
hexanes, pentane, CH2Cl2). NMR spectra were obtained on a Bruker
ARX 300 spectrometer (1H, 300 MHz; 13C, 75 MHz), a Bruker
Avance 400 MHz spectrometer, or a Varian Inova 500 spectrometer
(1H, 500 MHz; 13C, 126 MHz; 19F, 470 MHz; 11B, 160 MHz). For 1H
NMR and 13C NMR, chemical shifts (δ) are given relative to TMS and
referenced to the solvent signal (19F relative to external CFCl3; 11B
relative to external BF3·Et2O). NMR assignments were supported by
additional 1D and 2D NMR experiments. NMR spectra were recorded
at 25 °C unless otherwise stated, and chemical shifts are reported in
ppm. NMR solvents were purchased from Cambridge Isotopes, dried
over CaH2 (CD2Cl2, C6D5Br, and CDCl3), vacuum-distilled prior to
use, and stored over 4 Å molecular sieves in the glovebox. Elemental
analyses were performed on a Elementar Vario El III instrument. IR
spectra were recorded on a Varian 3100 FT-IR spectrometer
(Excalibur Series). Melting points were obtained with a DSC Q20
(TA Instruments). The synthesis of N,N′-(1,4-phenylenebis-
(methylene))bis(tert-butylamine) was achieved by the literature
method of Tilley and Sayigh.33 B(C6F5)3 was purified by two
successive sublimations (Toronto) or freshly prepared and precipi-
Figure 12. POV-ray depiction of 14a. Color code: C, black; N, blue-
green; B, yellow-green; F, pink; H, gray. Only NH hydrogen atoms are
shown.
features 13C NMR signals of the trisubstituted alkenyl moiety at
141.1 and 146.4 ppm, respectively, and a 11B NMR signal at ca.
−16 ppm. The X-ray crystal structure analysis of compound 15
(Figure 13) shows the transoid disposition of the B(C6F5)3 and
Figure 13. POV-ray depiction of 15. Color code: C, black; N, blue-
green; B, yellow-green; F, pink; H, gray. Only alkene CH hydrogen
atoms are shown.
tated from pentane (Munster).
̈
Reaction of PhNMe2 and B(C6F5)3. N,N-Dimethylaniline (10.0
mg, 0.083 mmol) and B(C6F5)3 (42.2 mg, 0.083 mmol) were dissolved
in C7D8 (0.5 mL) to yield a reaction solution which was characterized
by NMR spectroscopy. 1H NMR (600 MHz, C7D8, 298 K): δ 7.11 (m,
2H, m-C6H5); 6.67 (m, 1H, p-C6H5); 6.51 (m, 2H, o-C6H4); 2.47 (s,
6H, NMe2). 19F NMR (564 MHz, C7D8, 298 K): δ −128.8 (m, 2F, o-
PhNMe2 substituents about the terminal olefinic bond. The
corresponding B−C distance is 1.647(5) Å, while the olefinic
C−C bond length is 1.320(5) Å.
The contrasting behavior of the aniline derivative based FLP
is attributed to the reduced basicity of PhNMe2 in comparison
to PhCH2NMe2. The impact of this reduced basicity was
further illustrated in efforts to react PhNMe2/B(C6F5)3 with
either tBuCCH or Me3SiCCH. Apparently, the aniline
derivative is not sufficiently basic to abstract a proton from
these acetylenes, nor does 1,2-N/B-FLP addition occur;
presumably this is a result of increased steric hindrance.
Rather, the reaction between B(C6F5)3 and the 1-alkyne
derivatives occurs to give the products of 1,1-carboboration of
the alkyne.32 These products have been previously detailed, and
the nature of the products was confirmed by independent
synthesis in the absence of the amine.
C6F5); −142.0 (m, 1F, p-C6F5); −160.2 (m, 2F, m-C6F5) (Δδ(19Fp,m
)
≈
= 18.2). 11B{1H} NMR (192 MHz, C7D8, 298 K): δ 59.9 (br, ν1/2
950 Hz).
Synthesis of PhNH(iPr)(B(C6F5)3) (1). In a glovebox, a 20 mL vial
equipped with a magnetic stir bar was charged with B(C6F5)3 (176 mg,
0.344 mmol) and N-isopropylaniline (46.5 mg, 0.344 mmol) in
toluene (4 mL). All volatiles were removed, and the crude oil was
washed with hexanes (2 mL). The hexanes portion was reduced in
volume and placed in a −40 °C freezer. Colorless crystals of 1 were
1
obtained (122 mg, 0.192 mmol, 55%). H NMR (400 MHz, CD2Cl2,
298 K): δ 8.84 (br s, 1H, NH), 7.37 (m, 3H, o,p-Ar), 7.05 (m, 2H, m-
3
Ar), 3.68 (m, 1 H, JH−H = 6.1 Hz, CH(CH3)2), 1.23 ppm (d, 6H,
3JH−H = 6.5 Hz, CH(CH3)2). 13C NMR (101 MHz, CD2Cl2, 298 K): δ
147.8 (dm, 1JC−F ≈ 246 Hz, C6F5), 139.0 (dm, 1JC−F ≈ 242 Hz, C6F5),
1
136.5 (dm, JC−F ≈ 236 Hz, C6F5), 132.8 (i-Ar), 130.1 (o-Ar), 129.5
(p-Ar), 122.7 (m-Ar), 55.6 (CH), 19.5 ppm (CH3). 19F NMR (377
CONCLUSION
■
3
MHz, CD2Cl2, 298 K): δ −134.6 (d, 2F, JF−F = 25 Hz, o-C6F5),
3
−160.9 (t, 1F, JF−F = 42 Hz, p-C6F5), −165.6 (m, 2F, m-C6F5). 11B
The above chemistry demonstrates the ability of amines to
partake in FLP chemistry. While in some cases formation of
classical Lewis adducts are seen, it is still possible for such
systems to engage in subsequent reactivity with other
substrates. Herein, reactions with H2, CO2, olefins, alkynes,
and diynes have been demonstrated for amine−borane
combinations. This work serves to demonstrate that the notion
of FLP chemistry extends broadly beyond sterically demanding
phosphine−borane combinations, thus establishing some
generality of such reactivity. Moreover, this chemistry offers
new synthetic strategies based on amines in FLP chemistry. We
NMR (128 MHz, CD2Cl2, 298 K): δ −2.19 (s). Anal. Calcd for
C27H13BF15N: C, 50.11; H, 2.02; N, 2.16. Found: C 49.61; H, 2.46; N,
2.09. X-ray: C27H13BF15N, M = 647.19, a = 11.6228(4) Å, b =
18.1284(7) Å, c = 23.6578(9) Å, V = 4984.8(3) Å3, Z = 8,
orthorhombic, P212121, data (λ = 0.710 69 Å, T = 150 K), 8773 (Rint
=
0.030) and 7798 reflections (I ≥ 2σ(I)), 798 parameters, R1 = 0.032,
wR2 = 0.076, GOF = 1.021.
Synthesis of PhCH2NMe2(B(C6F5)3) (2). N,N-Dimethylbenzyl-
amine (10.0 mg, 0.074 mmol) and B(C6F5)3 (38.2 mg, 0.074 mmol)
were dissolved in C6D5Br (0.5 mL) and C7D8 (0.5 mL), respectively,
and mixed to yield a solution which was characterized by NMR
2373
dx.doi.org/10.1021/om300017u | Organometallics 2012, 31, 2367−2378

Organometallics
Article
1
11B{1H} NMR (160 MHz, CD2Cl2, 298 K): −24.6 (BH); −24.8 (br,
BD). X-ray: C27H15BF15N, M = 649.21, a = 10.1853(3) Å, b =
13.3147(8) Å, c = 21.7805(7) Å, α = 86.615(4)°, β = 73.671(3)°, γ =
spectroscopy. H NMR (400 MHz, C6D5Br, 298 K): δ 7.19 (m, 5H,
1
C6H5); 3.63 (br s, 2H, CH2N); 2.21 (s, 6H, NCH3). H NMR (600
MHz, C7D8, 298 K): δ 7.08, 7.04, 7.02 (m, ∑5H, C6H5); 3.36 (br s,
2H, CH2N); 2.00 (s, 6H, NCH3). 19F NMR (377 MHz, C6D5Br, 298
K): δ −126.3 (br, 2F, o-C6F5); −147.9 (br, 1F, p-C6F5); −160.6 (br,
2F, m-C6F5), (Δδ(19Fp,m) = 12.7). 19F NMR (564 MHz, C7D8, 298 K):
δ −128.0 (br, 2F, o-C6F5); −145.7 (br, 1F, p-C6F5); −161.0 (br, 2F,
m-C6F5), (Δδ(19Fp,m) = 15.3). 11B{1H} NMR (128 MHz, C6D5Br, 298
K): δ 30.3 (ν1/2 ≈ 1200 Hz). 11B{1H} NMR (192 MHz, C7D8, 298 K):
δ 46.3 (ν1/2 ≈ 800 Hz). X-ray: C27H13BF15N·CH2Cl2, M = 732.12, a =
9.9870(5) Å, b = 10.6730(5) Å, c = 14.3150(7) Å, α = 71.935(2)°, β =
68.525(3)°, V = 2634.6(2) Å3, Z = 4, triclinic, P1, data (λ = 1.541 78
̅
Å, T = 223 K), 9134 (Rint = 0.042) and 7448 reflections (I ≥ 2σ(I)),
810 parameters, R1 = 0.056, wR2 = 0.150, GOF = 1061.
Synthesis of [1,4-C6H4(CH2NH2tBu)2][HB(C6F5)3]2 (5). In a
glovebox, a 100 mL glass bomb equipped with a magnetic stir bar
and Teflon screw cap was charged with a solution of B(C6F5)3 (304
mg, 0.594 mmol) and 1,4-C6H4(CH2NHtBu)2 (72.5 mg, 0.297 mmol)
in toluene (4 mL). The reaction was degassed three times with a
freeze−pump−thaw cycle on the vacuum/H2 line. The reaction flask
was cooled to −196 °C and filled with H2 (4 atm). At 25 °C,
immediate precipitation of a white solid was observed. The reaction
mixture was stirred overnight at 70 °C. Pentane (10 mL) was added,
after which the supernatant was decanted. The residue was washed
with pentane (2 × 2 mL) and dried in vacuo to afford 5 as a white
powder (374 mg, 0.297 mmol, 100%). Crystals suitable for X-ray
crystal structure analyses were obtained from a concentrated solution
in C6D5Br at 25 °C. 1H NMR (400 MHz, CD2Cl2, 298 K): δ 7.27 (s,
4H, Ar); 5.95 (br s, 4H, NH2); 4.38 (s, 4H, CH2); 3.39 (q, 1JH−B = 83
Hz, BH); 1.62 ppm (s, 18H, C(CH3)3). 13C{1H} NMR (101 MHz, d8-
THF, 298 K): δ 149.3 (dm, 1JC−F ≈ 236 Hz, C6F5); 146.1 (i-Ar); 138.5
(dm, 1JC−F ≈ 243 Hz, C6F5); 137.4 (dm, 1JC−F ≈ 246 Hz, C6F5); 134.5
(br, i-C6F5); 131.4 (Ar); 59.5 (C(CH3)3); 46.1 (CH2); 25.9 ppm
(C(CH3)3). 19F NMR (377 MHz, CD2Cl2, 298 K): δ −134.9 (d, 2F,
3JF−F = 23 Hz, o-C6F5); −163.5 (t, 1F, 3JF−F = 20 Hz, p-C6F5); −167.0
ppm (m, 2F, m-C6F5). 11B NMR (128 MHz, CD2Cl2, 298 K): δ −24.3
80.851(2)°, γ = 81.259(2)°, V = 1423.59(12) Å3, Z = 2, triclinic, P1,
data (λ = 1.541 78 Å, T = 223 K) 4868 (Rint = 0.040) and 4417
reflections (I ≥ 2σ(I)), 426 parameters, R1 = 0.047, wR2 = 0.126,
GOF = 1.035.
̅
Synthesis of [PhNMe2H][HB(C6F5)3] (3) and [PhNMe2D][DB-
(C6F5)3] (3-d2). These compounds were prepared in a similar fashion.
A solution of B(C6F5)3 (42.2 mg, 0.083 mmol) and N,N-dimethylani-
line (10.0 mg, 0.083 mmol) in C6D5Br (2 mL) was subjected to three
freeze−pump−thaw cycles and back-filled with H2 (∼4 atm) at −196
°C. The solution was stored overnight at 25 °C, and all volatiles were
removed in vacuo. Upon addition of dichloromethane (0.5 mL) and
pentane (5 mL), a white precipitate was formed, which was collected
and dried to finally give the ammonium salt 3 (48.0 mg, 0.076 mmol,
92%). Data for 3 are as follows. 1H NMR (400 MHz, C6D5Br, 298 K):
δ 8.60 (s, 1H, NH); 7.07 (m, 3H, C6H5); 6.89 (m, 2H, C6H5); 3.50
(br, 1:1:1:1 q, 1JBH ≈ 80 Hz, 1H, BH); 2.72 (s, 6H, NCH3). 1H NMR
(500 MHz, CD2Cl2, 298 K): δ 8.88 (s, 1H, NH); 7.56 (m, 3H, C6H5);
7.37 (m, 2H, C6H5); 3.46 (br, 1:1:1:1 q, 1JBH ≈ 78 Hz, 1H, BH); 3.39
(s, 6H, NCH3). 13C{1H} NMR (101 MHz, C6D5Br, 298 K): δ 148.3
(dm, 1JC−F ≈ 230 Hz, C6F5); 140.7 (i-C6H5); 138.7 (dm, 1JC−F ≈ 251
1
ppm (d, JB−H = 94 Hz, BH). Anal. Calcd for C52H32B2F30N2: C,
48.93; H, 2.53; N, 2.19. Found: C, 48.82; H, 2.69; N, 2.52. X-ray:
C52H32B2F30N2·C6H5Br, M = 1432.42, a = 9.3616(18) Å, b =
11.479(2) Å, c = 15.046(3) Å, α = 73.474(9)°, β = 85.102(9)°, γ =
1
Hz, C6F5); 136.8 (dm, JC−F ≈ 247 Hz, C6F5); 131.0, 130.8, 118.9
(C6H5); 47.2 (NCH3); n.o. (i-C6F5). 19F NMR (377 MHz, C6D5Br,
298 K): δ −133.9 (m, 2F, o-C6F5); −160.4 (m, 1F, p-C6F5); −164.3
(m, 2F, m-C6F5), (Δδ(19Fp,m) = 4.1). 11B NMR (128 MHz, C6D5Br,
67.335(6)°, V = 1429.9(5) Å3, Z = 1, triclinic, P1, data (λ = 0.710 69 Å,
̅
T = 150 K), 4780 (Rint = 0.059) and 2984 reflections (I ≥ 2σ(I)), 424
parameters, R1 = 0.060, wR2 = 0.163, GOF = 1.081.
298 K): δ −24.0 (d, JBH ≈ 80 Hz). 11B{1H} NMR (128 MHz,
1
Synthesis of [PhCH2NMe2CO2B(C6F5)3] (6). N,N-Dimethylben-
zylamine (150 mg, 1.11 mmol) and B(C6F5)3 (570 mg, 1.11 mmol)
were dissolved in C6H5Br (10 mL), and the solution was subjected to
two freeze−pump−thaw cycles. At 25 °C the reaction flask was filled
with an atmosphere of CO2 and left at −32 °C for 12 h. Then pentane
(10 mL) was added, and the resulting white precipitate was filtered off
and dried in vacuo at −10 °C to yield 390 mg (54%, 0.600 mmol) of
the carbon dioxide containing compound. Crystals suitable for
diffraction were grown from a C6H5Br solution that was stored
C6D5Br, 298 K): −24.0 (s, ν1/2 ≈ 50 Hz). IR: νNH 3060 cm−1 and νBH
2311 cm−1. Anal. Calcd for C26H13BF15N: C, 49.16; H, 2.06; N, 2.21.
2
Found: C, 49.24; H, 2.25; N, 2.11. Data for 3-d2 are as follows. H
NMR (77 MHz, CD2Cl2, 298 K): δ 8.81 (br s, ND); 7.63, 7.41 (each
br, C6H4D); 3.45 (br m, BD). 11B{1H} NMR (160 MHz, CD2Cl2, 298
K): δ −24.3 (s, ν1/2 ≈ 60 Hz). 11B NMR (160 MHz, CD2Cl2, 298 K):
−24.3 (s, ν1/2 ≈ 50 Hz). X-ray: C27H15BF15N, M = 635.18, a =
9.9101(4) Å, b = 16.3709(14) Å, c = 15.6368(10) Å, β = 94.644(4)°, V
= 2528.5(3) Å3, Z = 4, monoclinic, P21/n, data (λ = 1.541 78 Å, T =
223 K) 4294 (Rint = 0.058) and 3080 reflections (I ≥ 2σ(I)), 396
parameters, R1 = 0.049, wR2 = 0.128, GOF = 1.015.
Synthesis of [PhCH2 NMe2 H][HB(C6 F5)3 ] (4) and
[PhCH2NMe2D][DB(C6F5)3] (4-d2). These compounds were prepared
in a similar fashion: a solution of B(C6F5)3 (37.9 mg, 0.074 mmol) and
N,N-dimethylbenzylamine (10.0 mg, 0.074 mmol) in C6D5Br (1 mL)
was subjected to three freeze−pump−thaw cycles and back-filled with
H2 at −196 °C (∼4 atm). After the mixture was stirred at 25 °C for 30
min, dichloromethane (0.1 mL) was added and the resulting solution
was layered with hexane (5 mL). Storing at 25 °C for 3 days yielded
white crystals (42.4 mg, 0.065 mmol, 88%). Data for 4 are as follows.
1H NMR (400 MHz, C6D5Br, 295 K): δ 7.36 (NH), 7.19 (m, 1H, p-
1
under an atmosphere of CO2 at −32 °C for several days. H NMR
(500 MHz, CD2Cl2, 218 K): δ 7.54 (m, 1H, p-C6H5); 7.42 (m, 2H, m-
C6H5); 7.25 (m, 2H, o-C6H5); 4.46 (s, 2H, CH2N); 3.08 (s, 6H,
NCH3). 13C{1H} NMR (126 MHz, CD2Cl2, 218 K): δ 150.1 (CO);
147.4 (dm, 1JC−F ≈ 238 Hz, C6F5); 139.1 (dm, 1JC−F ≈ 246 Hz, C6F5);
1
136.2 (dm, JC−F ≈ 246 Hz, C6F5); 132.4 (o-C6H5); 131.1 (p-C6H5);
129.3 (m-C6H5); 125.5 (i-C6H5); 117.5 (br, i-C6F5); 66.8 (CH2N);
48.0 (NCH3). 19F NMR (470 MHz, CD2Cl2, 218 K): δ −135.6 (m,
3
2F, o-C6F5); −158.9 (br t, JFF ≈ 20 Hz, 1F, p-C6F5); −164.7 (m, 2F,
m-C6F5) (Δδ(19Fp,m) = 5.8). IR (KBr/cm−1): ν 1822 (m). Anal. Calcd
for C28H13BF15NO2: C, 48.65; H, 1.90; N, 2.03. Found: C, 48.52; H,
1.99; N, 1.97. X-ray: C28H13BF15NO2, M = 691.20, a = 14.309(3) Å, b
= 12.160(2) Å, c = 15.471(3) Å, β = 92.833(7)°, V = 2688.6(9) Å3, Z
= 4, monoclinic, P21/n, data (λ = 0.710 69 Å, T = 150 K), 6176 (Rint
=
C6H5); 7.09 (m, 2H, m-C6H5); 6.86 (m, 2H, o-C6H5); 3.52 (s, 2H,
CH2N); 3.31 (br q, JHB ≈ 83 Hz, BH); 2.25 (s, 6H, CH3). 13C{1H}
1
0.036) and 4293 reflections (I ≥ 2σ(I)), 424 parameters, R1 = 0.045,
wR2 = 0.115, GOF = 1016.
NMR (101 MHz, C6D5Br, 297 K): δ 130.6 (p-C6H5); 130.1 (o-C6H5);
129.4 (m-C6H5); 127.5 (i-C6H5); 62.7 (CH2N); 42.8 (NCH3) [C6F5
not listed]. 19F NMR (377 MHz, C6D5Br, 295 K): δ −133.9 (m, 2F, o-
Synthesis of [PhCH2NHMe2][HCO2B(C6F5)3] (7). Compound 4
(100 mg, 0.154 mmol) was dissolved in toluene (4 mL). After two
freeze−pump−thaw cycles, the solution was pressurized with CO2 (1.5
atm) and then heated to 80 °C overnight. The solvent was removed
under reduced pressure, and pentane (10 mL) was added. Drying in
vacuo yielded 96.0 mg (0.139 mmol, 90%) of the formic acid adduct 7.
1H NMR (500 MHz, C6D6, 298 K): δ 8.29 (s, 1H, CHO); 6.98 (m,
3H, m,p-C6H5); 6.75 (m, 2H, o-C6H5); 2.84 (s, 2H, CH2N); 1.46 (s,
6H, NCH3), n.o. (NH). 13C{1H} NMR (126 MHz, C6D6, 298 K): δ
3
C6F5); −160.7 (t, JFF = 20.1 Hz, 1F, p-C6F5); −164.5 (m, 2F, m-
C6F5), (Δδ(19Fp,m) = 3.8). 11B NMR (128 MHz, C6D5Br, 295 K): δ
−24.3 (d, 1JBH ∼ 84 Hz). 11B{1H} NMR (128 MHz, C6D5Br, 295 K):
−24.3 (s, ν1/2 ≈ 60 Hz). Anal. Calcd for C27H15BF15N: C, 49.95; H,
2.33; N, 2.16. Found: C, 49.79; H, 2.39; N, 2.20. Data for 4-d2 are as
2
follows. H NMR (77 MHz, CD2Cl2, 298 K): δ 7.35 (br, ND); 4.27
(br, CHDN); 3.23 (br, BD). 11B NMR (160 MHz, CD2Cl2, 298 K): δ
1
−24.6 (ca. 50%, br d, JBH ≈ 88 Hz, BH); −24.8 (ca. 50%, br, BD).
170.2 (CHO); 148.6 (dm, 1JC−F ≈ 243 Hz, C6F5); 140.2 (dm, 1JC−F
≈
2374
dx.doi.org/10.1021/om300017u | Organometallics 2012, 31, 2367−2378

Organometallics
Article
1
247 Hz, C6F5); 137.6 (dm, JC−F ≈ 251 Hz, C6F5); 130.5 (p-C6H5),
130.4 (o-C6H5); 129.4 (m-C6H5); 128.0 (i-C6H5); 120.6 (br, i-C6F5);
60.8 (CH2N); 40.9 (NCH3). 19F NMR (470 MHz, C6D6, 298 K): δ
−134.2 (m, 2F, o-C6F5); −157.9 (t, 1F, 3JFF ≈ 21 Hz, p-C6F5); −164.3
(m, 2F, m-C6F5) (Δδ(19Fp,m) = 6.4). 11B{1H} NMR (160 MHz, C6D6,
298 K): δ −2.2 (ν1/2 ≈ 200 Hz). IR (KBr/cm−1): ν 1621 (m). Anal.
Calcd for C28H15BF15NO2: C, 48.51; H, 2.18; N, 2.02. Found: C,
48.33; H, 2.49; N, 2.36. X-ray: C28H15BF15NO2, M = 693.22, a =
7.5203(3) Å, b = 18.6531(8) Å, c = 19.9816(10) Å, V = 2803.0(2) Å3,
Z = 4, orthorhombic, P212121, data (λ = 1.541 78 Å, T = 223 K) 4454
(Rint = 0.064) and 3270 reflections (I ≥ 2σ(I)), 432 parameters, R1 =
0.043, wR2 = 0.102, Flack parameter −0.09(17), GOF = 1.035.
Synthesis of [PhNiPrH2][PhNiPrCO2B(C6F5)3] (8). In a glovebox,
a 50 mL glass bomb equipped with a magnetic stir bar and Teflon
screw tap was charged with a solution of B(C6F5)3 (500 mg, 0.978
mmol) and N-isopropylaniline (264 mg, 1.95 mmol) in toluene (7
mL). The reaction was degassed three times with a freeze−pump−
thaw cycle on the vacuum/CO2 line. The reaction flask was cooled to
−196 °C and filled with 13CO2 (1 atm). The reaction mixture was
stirred at 25 °C for 2 days. All volatiles were then removed in vacuo;
the residue was dissolved in a minimum amount of dichloromethane,
and the product was precipitated as a white powder using hexanes.
The product was washed with hexanes (2 × 2 mL) and dried in vacuo
to yield 8 (769 mg, 0.930 mmol, 95%). 1H NMR (400 MHz, CD2Cl2,
298 K): δ 7.55 (br s, NH2); 7.48−7.33 (m, 6H, m,p-Ar); 7.10 (d, 2H,
o-Ar); 6.68 (br d, 2H, o-Ar); 4.78 (m, 1H, CH); 3.09 (br s, 1H, CH);
1.12 (d, 6H, CH(CH3)2); 0.91 ppm (br s, 6H, CH(CH3)2). 13C{1H}
NMR (101 MHz, CD2Cl2, 298 K): δ 159.4 (s, NCO2); 147.9 (dm,
P1, data (λ = 0.710 69 Å, T = 150 K), 14 788 (Rint = 0.043) and 8568
reflections (I ≥ 2σ(I)), 1135 parameters, R1 = 0.085, wR2 = 0.271,
GOF = 1.031.
̅
Synthesis of [C5H6Me4NMeH]2[1,4-C6H4(CH2NtBuCO2B-
(C6F5)3)2] (10). In a glovebox, a 50 mL glass bomb equipped with a
magnetic stir bar was charged with B(C6F5)3 (206 mg, 0.402 mmol),
N,N′-(1,4-phenylenebis(methylene))bis(tert-butylamine) (50.0 mg,
0.201 mmol), and 1,2,2,6,6-pentamethylpiperidine (62.4 mg, 0.402
mmol) in toluene (5 mL). The reaction was degassed three times with
a freeze−pump−thaw cycle on the vacuum/CO2 line. The reaction
flask was cooled to −196 °C and filled with CO2 (1 atm). The reaction
mixture was stirred at 25 °C overnight. Over this reaction time
precipitate was observed in the reaction vessel. Pentane (3 mL) was
added, after which the supernatant was decanted. The product was
washed with pentane (3 × 2 mL) and dried in vacuo to afford the
product as a white crystalline material (153 mg, 46%). Colorless
crystals suitable for X-ray crystal structure analyses were obtained by
recrystallization from a THF solution layered with hexanes in a −40
1
°C freezer. H NMR (400 MHz, CD2Cl2, 298 K): δ 7.07 (s, 4H,
C6H4); 7.04 (br, 2H, NH); 4.61 (br, 4H, CH2); 2.63 (s, 6H, NCH3);
t
1.72−1.58 (br m, 12H, m,p-CH2); 1.37 (br, 18H, Bu); 1.28 ppm (s,
24H, CH3). 13C{1H} NMR (101 MHz, CD2Cl2, 298 K): δ 158.7
1
1
(NCO2); 148.0 (dm, JC1−F ≈ 240 Hz, C6F5); 138.2 (dm, JC−F ≈ 246
Hz, C6F5); 136.2 (dm, JC−F ≈ 246 Hz, C6F5); 128.8 (i-Ar); 125.9
(Ar); 124.2 (i-C6F5); 64.8 (C(CH3)2); 54.9 (C(CH3)3); 48.3 (amine-
CH2); 38.1 (PMP m-CH2); 29.5 (tBu); 29.0 (NCH3); 28.5 (PMP-
CH3); 18.8 (PMP-CH3); 15.4 ppm (PMP-p-CH2). 19F NMR (377
MHz, CD2Cl2, 298 K): δ −133.6 (br, 2F, o-C6F5); −164.8 (br, 1F, p-
C6F5); −168.6 ppm (br, 2F, m-C6F5). 11B NMR (128 MHz, CD2Cl2,
298 K): δ −4.70 ppm (s). IR (KBr): ν 1693 cm−1 (vs, CO). Anal.
Calcd for C74H70B2F30N4O4: C, 53.19; H, 4.22; N, 3.35. Found: C,
53.03; H, 4.38; N, 3.39. X-ray: C37H35BF15N2O2, M = 835.48, a =
15.0642(17) Å, b = 12.3370(14) Å, c = 21.279(2) Å, β = 109.498(7)°,
V = 3727.8(7) Å3, Z = 4, monoclinic, P21/c, data (λ = 0.710 69 Å, T =
150 K), 8566 (Rint = 0.129) and 3321 reflections (I ≥ 2σ(I)), 526
parameters, R1 = 0.068, wR2 = 0.221, GOF = 0.965.
1JC−F ≈ 240 Hz, C6F5); 140.3 (s, i-Ar); 138.7 (dm, JC−F ≈ 243 Hz,
1
C6F5); 136.5 (dm, 1JC−F ≈ 239 Hz, C6F5); 132.1 (s, o-Ar); 129.8 (br, i-
C6F5); 129.6 (s, m-Ar); 127.5 (s, p-Ar); 122.2 (br, o-Ar); 49.0 (s, CH);
21.2 (s, CH(CH3)2); 19.2 ppm (br, CH(CH3)2).19F NMR (377 MHz,
3
CD2Cl2, 298 K): δ −134.7 (d, 2F, JF−F = 22 Hz, o-C6F5); −162.3 (t,
1F, JF−F = 20 Hz, p-C6F5); −166.8 ppm (m, 2F, m-C6F5). 11B NMR
3
(128 MHz, CD2Cl2, 298 K): δ −3.95 ppm (s). IR: ν(CO) 1646
cm−1. Anal. Calcd for C75H50B2Cl2F30N4O4: C, 51.96; H, 2.91; N, 3.23.
Found: C, 51.63; H, 3.28; N, 3.29. X-ray: C37H24BF15N2O2·1/2CH2Cl2,
M = 866.86, a = 11.2336(4) Å, b = 14.9889(6) Å, c = 44.3937(16) Å, β
= 90.618(2)°, V = 7474.5(5) Å3, Z = 8, monoclinic, P21/c, data (λ =
0.710 69 Å, T = 150 K), 13 157 (Rint = 0.048) and 10 517 reflections (I
≥ 2σ(I)), 1072 parameters, R1 = 0.053, wR2 = 0.127, GOF = 1.051.
Synthesis of [1,4-C6H4(CH2NH2tBu)(CH2NtBuCO2B(C6F5)3)]
(9). In a glovebox, a 50 mL glass bomb equipped with a magnetic
stir bar and Teflon screw tap was charged with a solution of B(C6F5)3
(154 mg, 0.300 mmol) and N,N′-(1,4-phenylenebis(methylene))bis-
(tert-butylamine) (73.3 mg, 0.300 mmol) in toluene (5 mL). The
reaction was degassed three times with a freeze−pump−thaw cycle on
the vacuum/CO2 line. The reaction flask was cooled to −196 °C and
filled with 13CO2 (1 atm). Upon warming to 25 °C, precipitate was
observed in the reaction flask. The mixture was stirred overnight at 50
°C. Pentane (3 mL) was added, after which the supernatant was
decanted. The product was washed with pentane (3 × 2 mL) and
dried in vacuo to afford 9 as a white powder (212 mg, 0.263 mmol,
88%). Crystals suitable for X-ray crystal structure analyses were
obtained by recrystallization from a standing solution in C6H5Br at 25
°C. 1H NMR (400 MHz, d8-THF, 298 K): δ 7.88 (br, 2H, NH2); 7.34
(br, 2H, Ar); 7.21 (br d, 2H, Ar); 4.67 (br, 2H, CH2); 4.20 (br m, 2H,
NH2CH2); 1.48 (s, 9H, CH3); 1.30 ppm (br, 9H, CH3). 13C{1H}
NMR (101 MHz, d8-THF, 298 K): δ 157.6 (NCO2); 148.1 (dm, 1JC−F
Synthesis of [PhNiPrC(OSiEt3)OB(C6F5)3] (11). In a glovebox,
compound 8 (68.4 mg, 0.0827 mmol) was weighed into a 20 mL vial
and dissolved in toluene (3 mL). To this solution, HSiEt3 (13.3 μL,
0.0835 mmol) was added via syringe. The reaction mixture was mixed
overnight at 25 °C. All volatiles were removed, and the crude oil was
dissolved in a minimum amount of pentane and placed in a −40 °C
freezer overnight. Colorless crystals of 11 were obtained (42.6 mg,
0.0529 mmol, 64%). 1H NMR (400 MHz, CD2Cl2, 298 K): δ 7.56 (m,
3
3H, m,p-Ar); 7.15 (m, 2H, o-Ar); 4.77 (m, 1H, JH−H = 6.6 Hz, CH);
3
3
1.15 (d, 6H, JH−H = 6.6 Hz, CH(CH3)2); 0.64 (t, 9H, JH−H = 8 Hz,
Si(CH2CH3)3, 0.10 (q, 6H, JH−H = 8 Hz, Si(CH2CH3)3 . 13C{1H}
3
NMR (101 MHz, CD2Cl2, 298 K): δ 156.4 (NCO2); 148.3 (dm, 1JC−F
≈ 249 Hz, C6F5); 137.5 (dm, 1JC−F ≈ 250 Hz, C6F5); 136.5 (dm, 1JC−F
≈ 242 Hz, m-C6F5); 134.8 (i-Ar); 130.7 (p-Ar); 130.2 (m-Ar); 130.1
(o-Ar); 129.4 (br, i-C6F5); 53.7 (NCH); 20.7 (CH(CH3)2); 6.07
(Si(CH2CH3)3); 4.31 ppm (Si(CH2CH3)3). 19F NMR (377 MHz,
CD2Cl2, 298 K): δ −135.0 (br, 2F, o-C6F5); −160.0 (br, 1F, p-C6F5);
−165.3 (br, 2F, p-C6F5) ppm. 11B NMR (128 MHz, CD2Cl2, 298 K): δ
−3.98 ppm (s). Anal. Calcd for C34H27BF15NO2Si: C, 50.70; H, 3.38;
N, 1.74. Found: C, 50.85; H, 3.54; N, 1.84. X-ray: C34H27BF15NO2Si,
M = 805.47, a = 10.0980(8) Å, b = 11.9201(9) Å, c = 15.5418(13) Å,
α = 88.808(4)°, β = 80.396(5)°, γ = 69.131(4)°, V = 1722.0(2) Å3, Z
= 2, triclinic, P1, data (λ = 0.710 69 Å, T = 150 K), 6044 (Rint = 0.053)
̅
1
≈ 246 Hz, C6F5); 145.7 (i-Ar); 138.1 (dm, JC−F ≈ 246 Hz, C6F5);
136.0 (dm, JC−F ≈ 242 Hz, C6F5); 128.7 (o-Ar); 128.6 (i-Ar); 127.6
and 4109 reflections (I ≥ 2σ(I)), 487 parameters, R1 = 0.042, wR2 =
1
0.108, GOF = 1.012.
(o-Ar); 124.3 (br, i-C6F5); 57.9 (C(CH3)3); 54.9 (C(CH3)3); 47.9
(CH2); 45.7 (CH2); 29.0 (br, CH3); 25.4 ppm (CH3) 19F NMR (377
MHz, d8-THF, 298 K): δ −134.9 (br, 2F, o-F); −162.7 (br, 1F, p-F);
−167.8 ppm (br, 2F, m-F). 11B NMR (128 MHz, d8-THF, 298 K): δ
−4.24 (s) ppm. IR: ν(CO) 1645 cm−1. Anal. Calcd for
C35H28BF15N2O2·THF: C, 53.44; H, 4.14; N, 3.20. Found: C, 53.89;
H, 4.63; N, 3.16. X-ray: C35H28BF15N2O2·CH2Cl2·THF, M = 961.43, a
= 11.8169(9) Å, b = 14.2528(10) Å, c = 25.8313(18) Å, α = 92.291(4)
°, β = 101.983(4)°, γ = 94.629(4)°, V = 4234.7(5) Å3, Z = 4, triclinic,
Synthesis of PhCH2NMe2CH2CH2B(C6F5)3 (12). A solution of
N,N-dimethylbenzylamine (30.0 mg, 0.222 mmol) and B(C6F5)3 (114
mg, 0.222 mmol) in pentane (5 mL) was degassed carefully and
pressurized with ethylene (2 atm), upon which a white solid started to
precipitate. Stirring was continued for 2 days, and then the precipitate
was filtered off. After crystallization of the solid from dichloro-
methane/pentane at −32 °C, the product was obtained (57%, 85.6 mg,
1
0.126 mmol). H NMR (600 MHz, C6D6, 298 K): δ 6.96 (m, 1H, p-
C6H5); 6.91 (m, 2H, m-C6H5); 6.21 (m, 2H, o-C6H5); 2.48 (s, 2H,
2375
dx.doi.org/10.1021/om300017u | Organometallics 2012, 31, 2367−2378

Organometallics
Article
= 73.953(2)°, γ = 72.449(6)°, V = 1577.24(12) Å3, Z = 2, triclinic, P1,
PhCH2N); 2.31 (m, 2H, NCH2); 1.55 (br, 2H, CH2B); 1.20 (s, 6H,
NCH3). 13C{1H} NMR (126 MHz, C6D6, 298 K): δ 148.9 (dm, 1JC−F
≈ 241 Hz, C6F5); 139.0 (dm, 1JC−F ≈ 253 Hz, C6F5); 137.4 (dm, 1JC−F
≈ 239 Hz, C6F5); 132.0 (o-C6H5); 131.0 (p-C6H5); 129.0 (m-C6H5);
125.9 (i-C6H5); n.o. (i-C6F5); 68.9 (NCH2); 67.2 (PhCH2N); 47.8
(NCH3); 15.6 (br, CH2B). 19F NMR (564 MHz, C6D6, 298 K): δ
−132.7 (m, 2F, o-C6F5); −160.8 (t, 3J = 20.2 Hz, 1F, p-C6F5); −165.0
(m, 2F, m-C6F5) (Δδ(19Fp,m) = 4.2). 11B{1H} NMR (160 MHz, C6D6,
̅
data (λ = 1.541 78 Å, T = 223 K) 5412 (Rint = 0.040) and 4657
reflections (I ≥ 2σ(I)), 471 parameters, R1 = 0.053, wR2 = 0.151,
GOF = 1.024.
1
Data for 14b are as follows. H NMR (500 MHz, C6D6, 298 K): δ
7.22 (m, 2H, 4-H); 7.01 (m, 1H, p-C6H5); 6.94 (m, 2H, m-C6H5);
6.83 (m, 3H, 5,6-H); 6.49 (m, 2H, o-C6H5); 2.75 (s, 2H, CH2N); 1.34
(s, 2H, NCH3). 13C{1H} NMR (126 MHz, C6D6, 298 K): δ 149.0
(dm, 1JC−F ≈ 239 Hz, C6F5); 139.2 (dm, 1JC−F ≈ 221 Hz, C6F5); 137.3
298 K):
δ −14.4 (ν1/2 ≈ 30 Hz). Anal. Calcd for
1
C29H17BF15N·0.3CH2Cl2: C, 50.20; H, 2.51; N, 2.00. Found: C,
50.06; H, 2.17; N, 1.90. X-ray: C29H17BF15N·1/2CH2Cl2, M = 717.71, a
= 13.2426(3) Å, b = 13.7868(3) Å, c = 18.2798(5) Å, α = 111.590(2)°,
β = 99.707(2)°, γ = 101.426(1)°, V = 2933.02(12) Å3, Z = 4, triclinic,
(dm, JC−F ≈ 226 Hz, C6F5); 131.7 (C-4); 131.1 (p-C6H5); 130.5 (o-
C6H5); 129.6 (m-C6H5); 128.8 (C-5); 127.3 (C-6); 126.3 (C-3); 126.2
1
(i-C6H5); 124.1 (br m, i-C6F5); 111.9 (1:1:1:1 q, JCB ≈ 70 Hz, C-1);
94.9 (1:1:1:1 q, 2JCB ≈ 15 Hz,, C-2); 61.9 (CH2N); 42.0 (NCH3). 19
F
P1, data (λ = 1.541 78 Å, T = 223 K), 10 000 (Rint = 0.052) and 7942
̅
NMR (470 MHz, C6D6, 298 K): δ −132.3 (m, 2F, o-C6F5); −161.2 (t,
3JFF = 21.1 Hz, 1F, p-C6F5); −165.5 (m, 2F, m-C6F5), (Δδ(19Fp,m) =
4.3). 11B{1H} NMR (160 MHz, C6D6, 298 K): δ −20.3 (ν1/2 ≈ 20
Hz). Anal. Calcd for C35H19BF15N: C, 56.10; H, 2.56; N, 1.87. Found:
C, 55.24; H, 2.56; N, 2.17.
parameters (I ≥ 2σ(I)), 872 parameters, R1 = 0.048, wR2 = 0.124,
GOF = 1.051.
Synthesis of PhCH2NMe2C(CCMe)CMeB(C6F5)3 (13). 2,4-
Hexadiyne (11.5 mg, 0.148 mmol) was added to a solution of N,N-
dimethylbenzylamine (20.0 mg, 0.148 mmol) and B(C6F5)3 (75.8 mg,
0.148 mmol) in pentane (5 mL). After the mixture was stirred
overnight at 25 °C, the obtained precipitate was filtered off and dried
under reduced pressure to yield the product 13 (52%, 55.8 mg, 0.077
1
Data for 14c are as follows. H NMR (500 MHz, C6D6, 298 K): δ
7.05 (m, 1H, p-C6H5); 7.00 (m, 2H, m-C6H5); 6.56 (m, 2H, o-C6H5);
2.81 (s, 2H, CH2N); 1.42 (s, 6H, NCH3); 1.27 (s, 9H, tBu). 13C{1H}
NMR (126 MHz, C6D6, 298 K): δ 149.0 (dm, 1JC−F ≈ 240 Hz, C6F5);
138.8 (dm, 1JC−F ≈ 243 Hz, C6F5); 137.3 (dm, 1JC−F ≈ 247 Hz, C6F5);
131.2 (p-C6H5); 130.5 (o-C6H5); 129.7 (m-C6H5); 126.4 (i-C6H5);
104.4 (br, C-2); 61.8 (CH2N); 42.0 (NCH3); 31.9 (tBu); 28.7 (tBu),
n.o. (i-C6F5); n.o. (C-1). 19F NMR (470 MHz, C6D6, 298 K): δ
1
mmol). H NMR (500 MHz, CD2Cl2, 298 K): δ 7.50 (m, 1H, p-
C6H5); 7.38 (m, 2H, m-C6H5); 7.22 (m, 2H, o-C6H5); 4.59 (d, 2JHH
=
2
13.1 Hz, 1H, CH2N); 4.46 (d, JHH = 13.1 Hz, 1H, CH2N); 3.36 (s,
3H, NCH3); 3.27 (s, 3H, NCH3); 2.00 (br s, 3H, 1-H); 1.63 (s, 3H, 6-
H). 13C{1H} NMR (126 MHz, CD2Cl2, 298 K): δ 156.6 (1:1:1:1 q,
1JCB ≈ 52 Hz, C-2); 132.4 (o-C6H5); 131.4 (p-C6H5); 129.5 (m-
C6H5); 127.7 (i-C6H5); 126.7 (br, C-3); 97.2 (C-5); 74.7 (br, C-4);
69.2 (CH2N); 56.0, 53.3 (NCH3); 22.2 (br, C-1); 4.1 (C-6) [C6F5 not
listed]. 19F NMR (470 MHz, CD2Cl2, 298 K): δ −129.5 (m, 1F, o-
3
−131.7 (m, 2F, o-C6F5); −162.4 (t, JFF = 20.4 Hz, 1F, p-C6F5);
−166.3 (m, 2F, m-C6F5), (Δδ(19Fp,m) = 3.9). 11B{1H} NMR (160
MHz, C6D6, 298 K): δ −20.3 (ν1/2 ≈ 25 Hz). Anal. Calcd for
C33H23BF15N: C, 54.34; H, 3.18; N, 1.92. Found: C, 54.62; H, 3.21; N,
1.89.
A
C
C
1
C6F5 ); −129.6 (m, 1F, o-C6F5 ); −129.9 (m, 1F, o-C6F5 ); −130.5
Data for 14d are as follows. H NMR (500 MHz, C6D6, 298 K): δ
B
B
A
(m, 1F, o-C6F5 ); −131.9 (m, 1F, o-C6F5 ); −133.1 (m, 1F, o-C6F5 );
7.01 (m, 1H, p-C6H5); 6.95 (m, 2H, m-C6H5); 6.60 (m, 2H, o-C6H5);
2.87 (br s, 2H, CH2N); 1.45 (br s, 6H, NCH3); 0.04 (s, 2JSiH = 6.9 Hz,
9H, SiCH3). 13C{1H} NMR (126 MHz, C6D6, 298 K): δ 148.9 (dm,
1JC−F ≈ 244 Hz, C6F5); 139.4 (dm, 1JC−F ≈ 235 Hz, C6F5); 137.4 (dm,
1JC−F ≈ 245 Hz, C6F5); 131.1 (p-C6H5); 130.7 (o-C6H5); 129.6 (m-
C6H5); 126.3 (i-C6H5); 101.2 (m, C-2); 61.4 (CH2N); 41.6 (NCH3);
0.78 (SiCH3), n.o. (i-C6F5); n.o. (C-1). 19F NMR (470 MHz, C6D6,
3
A
3
−162.2 (t, J = 20.5 Hz, 1F, p-C6F5 ); −163.1 (t, J = 21.6 Hz, 1F, p-
C
3
B
C6F5A); −163.5 (t, J = 20.6 Hz, 1F, p-C6F5 ); −165.9 (m, 1F, m-
A
C
C6F5 ); −166.5 (m, 1F, m-C6F5 ); −167.3 (m, 2F, m-C6F5 ); −167.4
B
C
(m, 2F, m-C6F5 ); −168.0 (m, 1F, m-C6F5 ); −168.2 (m, 1F, m-
B
C6F5 ). 11B{1H} NMR (160 MHz, CD2Cl2, 298 K): δ −12.1 (ν1/2
≈
20 Hz). Anal. Calcd for C33H19BF15N: C, 54.65; H, 2.64; N, 1.93.
Found: C, 54.69; H, 3.00; N, 1.93. X-ray: C33H19BF15N·1/2C5H12, M =
761.38, a = 10.3487(3) Å, b = 13.2156(8) Å, c = 13.9427(10) Å, α =
97.316(3)°, β = 107.850(5)°, γ = 109.846(3)°, V = 1649.26(14) Å3, Z
3
298 K): δ −131.8 (m, 2F, o-C6F5); −160.6 (t, J = 21.1 Hz, 1F, p-
C6F5); −165.3 (m, 2F, m-C6F5), (Δδ(19Fp,m) = 4.7). 11B{1H} NMR
(160 MHz, C6D6, 298 K): δ −20.9 (ν1/2 ≈ 20 Hz). 29Si DEPT NMR
(99 MHz, C6D6, 298 K): δ −19.3 (ν1/2 ≈ 5 Hz). Anal. Calcd for
C32H23BF15NSi: C, 51.56; H, 3.11; N, 1.88. Found: C, 51.27; H, 3.29;
N, 1.91.
= 2, triclinic, P1, data (λ = 1.541 78 Å, T = 223 K), 5717 (Rint = 0.042)
̅
and 4943 reflections (I ≥ 2σ(I)), 471 parameters, R1 = 0.058, wR2 =
0.175, maximum GOF = 1.064.
Synthesis of [PhCH2NMe2H][RCCB(C6F5)3] (R = n-Bu (14a),
Ph (14b), tBu (14c), SiMe3 (14d)). These compounds were prepared
in a general way. A representative example: a solution of N,N-
dimethylbenzylamine (50.0 mg, 0.370 mmol) and B(C6F5)3 (190 mg,
0.370 mmol) in pentane (10 mL) was treated with 1-hexyne (30.5 mg,
0.370 mmol) and the reaction mixture was stirred vigorously
overnight. The resulting white solid was filtered off, washed with
pentane, and dried in vacuo to yield the zwitterionic compound 14a
(190 mg, 0.26 mmol, 70%).
Synthesis of [PhNMe2C(C4H9)CH(B(C6F5)3)] (15). N,N-
Dimethylaniline (40.0 mg, 0.330 mmol), B(C6F5)3 (170 mg, 0.332
mmol), and 1-hexyne (27.1 mg, 0.330 mmol) were dissolved in
pentane (5 mL), and the mixture was stirred at 25 °C overnight. The
solvent was removed under reduced pressure to yield a yellow oil,
which was purified by fractional crystallization from dichloromethane/
pentane at −32 °C. Compound 15 was isolated in 50% yield (118 mg,
1
0.165 mmol). H NMR (600 MHz, C6D6, 298 K): δ 6.71 (m, 3H,
1
m-,p-Ph); 6.70 (m, 1H, 1-H); 6.48 (m, 2H, o-Ph); 1.98 (s, 6H,
NCH3); 1.53 (m, 2H, 3-H); 0.70 (m, 2H, 5-H); 0.49 (t, 3JHH = 7.1 Hz,
3H, 6-H); 0.30 (m, 2H, 4-H). 13C{1H} NMR (151 MHz, C6D6, 298
K): δ 146.4 (C-2); 141.1 (br, C-1); 130.1 (p-Ph); 129.9 (m-Ph), 120.1
(o-Ph); n.o. (i-Ph); 53.7 (NCH3); 30.6 (C-4); 30.0 (C-3); 23.1 (C-5);
13.4 (C-6) [C6F5 not listed]. 19F NMR (564 MHz, C6D6, 298 K): δ
−132.2 (m, 2F, o-C6F5); −160.6 (t, 3J = 20.4 Hz, 1F, p-C6F5); −165.2
(m, 2F, m-C6F5), (Δδ(19Fp,m) = 4.6). 11B{1H} NMR (192 MHz, C6D6,
Data for 14a are as follows. H NMR (500 MHz, C6D6, 298 K): δ
7.00 (m, 1H, p-C6H5); 6.95 (m, 2H, m-C6H5); 6.62 (m, 2H, o-C6H5);
2.83 (s, 2H, CH2N); 1.59 (m, 2H, 3-H); 1.46 (s, 6H, NCH3); 1.43 (m,
3
2H, 4-H); 1.31 (m, 2H, 5-H); 0.84 (t, JHH = 7.3 Hz, 3H, 6-H); n.o.
(NH). 13C{1H} NMR (126 MHz, C6D6, 298 K): δ 148.9 (dm, 1JC−F
238 Hz, C6F5); 139.3 (dm, 1JC−F ≈ 245 Hz, C6F5); 137.3 (dm, 1JC−F
≈
≈
249 Hz, C6F5); 131.1 (p-C6H5); 130.7 (o-C6H5); 129.6 (m-C6H5);
126.5 (i-C6H5); 124.6 (br m, i-C6F5); 101.3 (1:1:1:1 q, 1JCB = 71.1 Hz,
2
C-1); 96.1 (1:1:1:1 q, JCB = 14.4 Hz, C-2); 61.9 (CH2N); 41.8
298 K): δ −16.3 (ν1/2 ≈ 20 Hz). Anal. Calcd for
(NCH3); 31.9 (C-4); 22.0 (C-5); 20.7 (C-3); 13.6 (C-6). 19F NMR
C33H19BF15N·0.25CH2Cl2: C, 53.50; H, 2.61; N, 1.87. Found: C,
53.22; H, 2.97; N, 2.28. X-ray: C32H21BF15N·CH2Cl2, M = 800.23, a =
9.5086(6) Å, b = 11.9158(7) Å, c = 15.6879(10) Å, α = 94.247(5)°, β
= 97.456(4)°, γ = 106.783(3)°, V = 1675.69(18) Å3, Z = 2, triclinic,
3
(470 MHz, C6D6, 298 K): δ −132.1 (m, 2F, o-C6F5); −161.3 (t, J =
22.2 Hz, 1F, p-C6F5); −165.6 (m, 2F, m-C6F5), (Δδ(19Fp,m) = 4.3).
11B{1H} NMR (160 MHz, C6D6, 298 K): δ −20.6 (s, ν1/2 ≈ 20 Hz).
Anal. Calcd for: C33H23BF15N: C, 54.34; H, 3.18; N, 1.92. Found: C,
53.84; H, 3.13; N, 2.07. X-ray: C33H23BF15N, M = 729.33, a =
10.0966(4) Å, b = 10.4671(6) Å, c = 16.6994(5) Å, α = 73.407(4)°, β
P1, data (λ = 1.54178 Å, T = 223 K) 5741 (R = 0.058) and 4440
̅
int
reflections (I ≥ 2σ(I)), 472 parameters, R1 = 0.068, wR2 = 0.192,
GOF = 1.030.
2376
dx.doi.org/10.1021/om300017u | Organometallics 2012, 31, 2367−2378

Organometallics
Article
X-ray Data Collection and Reduction (Toronto). Crystals were
coated in Paratone-N oil in the glovebox, mounted on a MiTegen
Micromount, and placed under an N2 stream, thus maintaining a dry,
O2-free environment for each crystal. The data were collected on a
Bruker Apex II diffractometer with Mo Kα radiation (λ = 0.710 69 Å).
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).
ACKNOWLEDGMENTS
■
Financial support from the Fonds der Chemischen Industrie
and a gift of solvents from BASF is gratefully acknowledged by
G.E. D.W.S. is grateful for the financial support of the NSERC
of Canada and the award of a Canada Research Chair and a
Killam Research Fellowship. E.O. is grateful for the award of an
NWO postdoctoral fellowship.
̈
X-ray Data Collection and Reduction (Munster). Crystals were
coated in FOMBLIN Y oil, mounted on a glass fiber, and placed under
an N2 stream, thus maintaining a dry, O2-free environment for each
crystal. The data were collected on Nonius KappaCCD diffractom-
eters, both with APEXII detectors; in the case of Mo radiation a
rotating anode generator equipped with Montel mirrors was used. The
frames were integrated with the DENZO-SMN software package34
including absorption corrections35 using the empirical multiscan
method.
REFERENCES
■
(1) Stephan, D. W.; Erker, G. Angew. Chem., Int. Ed. 2010, 49, 46.
(2) (a) Welch, G. C.; Juan, R. R. S.; Masuda, J. D.; Stephan, D. W.
Science 2006, 314, 1124. (b) Welch, G. C.; Stephan, D. W. J. Am.
Chem. Soc. 2007, 129, 1880. (c) Spies, P.; Erker, G.; Kehr, G.;
Bergander, K.; Frohlich, R.; Grimme, S.; Stephan, D. W. Chem.
̈
Commun. 2007, 5072.
Structure Solution and Refinement (Toronto). Non-hydrogen
atomic scattering factors were taken from the literature tabulations.36
The heavy-atom positions were determined using direct methods
employing the SHELXTL direct methods routine.37 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 F2, minimizing the function w(Fo −
(3) (a) Huber, D. P.; Kehr, G.; Bergander, K.; Frohlich, R.; Erker, G.;
̈
Tanino, S.; Ohki, Y.; Tatsumi, K. Organometallics 2008, 27, 5279.
(b) Piers, W. E.; Marwitz, A. J. V.; Mercier, L. G. Inorg. Chem. 2011,
50, 12252.
(4) (a) Chase, P. A.; Jurca, T.; Stephan, D. W. Chem. Commun. 2008,
1701. (b) Chase, P. A.; Welch, G. C.; Jurca, T.; Stephan, D. W. Angew.
Chem., Int. Ed. 2007, 46, 9136. (c) Stephan, D. W.; Greenberg, S.;
Graham, T. W.; Chase, P.; Hastie, J. J.; Geier, S. J.; Farrell, J. M.;
Brown, C. C.; Heiden, Z. M.; Welch, G. C.; Ullrich, M. Inorg. Chem.
2011, 50, 12338. (d) Axenov, K. V.; Kehr, G.; Frohlich, R.; Erker, G. J.
Am. Chem. Soc. 2009, 131, 3454. (e) Spies, P.; Schwendemann, S.;
Lange, S.; Kehr, G.; Frohlich, R.; Erker, G. Angew. Chem., Int. Ed. 2008,
47, 7543. (f) Wang, H. D.; Frohlich, R.; Kehr, G.; Erker, G. Chem.
2
2
Fc)2, where the weight w is defined as 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.
C−H atom positions were calculated and allowed to ride on the
carbon to which they are bonded, assuming a C−H bond length of
0.95 Å. H atom temperature factors were fixed at 1.10 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. Additional details are
provided in the Supporting Information.
̈
̈
̈
Commun. 2008, 5966. (g) Tumay, T. A.; Axenov, K. V.; Peuser, I.;
Kehr, G.; Frohlich, R.; Erker, G. Organometallics 2010, 29, 1067.
̈
(h) Grimme, S.; Kruse, H.; Goerigk, L.; Erker, G. Angew. Chem., Int.
Ed. 2010, 49, 1402.
(5) Dureen, M. A.; Lough, A.; Gilbert, T. M.; Stephan, D. W. Chem.
Commun. 2008, 4303.
(6) Dureen, M. A.; Welch, G. C.; Gilbert, T. M.; Stephan, D. W.
Inorg. Chem. 2009, 48, 9910.
(7) (a) Birkmann, B.; Voss, T.; Geier, S. J.; Ullrich, M.; Kehr, G.;
Erker, G.; Stephan, D. W. Organometallics 2010, 29, 5310. (b) Kreitner,
C.; Geier, S. J.; Stanlake, L. J. E.; Caputo, C.; Stephan, D. W. Dalton
Trans. 2011, 6771.
̈
Structure Solution and Refinement (Munster). Non-hydrogen
atomic scattering factors were taken from the literature tabulations.36
The heavy-atom positions were determined using direct or Patterson
methods employing the SHELXS routine.37 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 F2 employing the SHELXL routine. 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.
C−H atom positions were calculated and allowed to ride on the
carbon to which they are bonded, assuming C−H bond lengths
between 0.94 and 0.99 Å, depending on the type of carbon atom. H
atom temperature factors were fixed at 1.20 or 1.50 times the isotropic
temperature factor of the C atom to which they are bonded. 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. Additional data for the
structural studies have been deposited with the Cambridge Crystallo-
graphic Database.
(8) (a) Momming, C. M.; Otten, E.; Kehr, G.; Frohlich, R.; Grimme,
̈
̈
S.; Stephan, D. W.; Erker, G. Angew. Chem., Int. Ed. 2009, 48, 6643.
(b) Menard, G.; Stephan, D. W. J. Am. Chem. Soc. 2010, 132, 1796.
(c) Menard, G.; Stephan, D. W. Angew. Chem., Int. Ed. 2011, 50, 8396.
́
́
(d) Zhao, X. X.; Stephan, D. W. Chem. Commun. 2011, 47, 1833.
(e) Peuser, I.; Neu, R. C.; Zhao, X.; Ulrich, M.; Schirmer, B.; Kehr, G.;
Frohlich, R.; Grimme, S.; Erker, G.; Stephan, D. W. Chem. Eur. J. 2011,
17, 9640.
(9) (a) McCahill, J. S. J.; Welch, G. C.; Stephan, D. W. Angew. Chem.,
Int. Ed. 2007, 46, 4968. (b) Sortais, J. B.; Voss, T.; Kehr, G.; Frohlich,
R.; Erker, G. Chem. Commun. 2009, 7417. (c) Momming, C. M.; Kehr,
̈
̈
̈
G.; Frohlich, R.; Erker, G. Chem. Commun. 2011, 47, 2006.
̈
(10) Ullrich, M.; Seto, K. S. H.; Lough, A. J.; Stephan, D. W. Chem.
Commun. 2009, 2335.
(11) (a) Dureen, M. A.; Stephan, D. W. Organometallics 2010, 29,
6594. (b) Dureen, M. A.; Brown, C. C.; Stephan, D. W.
Organometallics 2010, 29, 6422. (c) Dureen, M. A.; Stephan, D. W.
ASSOCIATED CONTENT
■
J. Am. Chem. Soc. 2009, 131, 8396. (d) Momming, C. M.; Fromel, S.;
̈
S
* Supporting Information
Kehr, G.; Frohlich, R.; Grimme, S.; Erker, G. J. Am. Chem. Soc. 2009,
̈
Text, figures, and CIF files giving synthetic, experimental, and
crystallographic details. This material is available free of charge
via the Internet at http://pubs.acs.org.
131, 12280. (e) Stirling, A.; Hamza, A.; Rokob, T. A.; Papai, I. Chem.
Commun. 2008, 3148. (f) Guo, Y.; Li, S. H. Eur. J. Inorg. Chem. 2008,
2501.
(12) Momming, C. M.; Kehr, G.; Wibbeling, B.; Frohlich, R.;
̈
̈
Schirmer, B.; Grimme, S.; Erker, G. Angew. Chem., Int. Ed. 2010, 49,
AUTHOR INFORMATION
■
2414.
Notes
(13) Spies, P.; Kehr, G.; Bergander, K.; Wibbeling, B.; Frohlich, R.;
Erker, G. Dalton Trans. 2009, 1534.
̈
The authors declare no competing financial interest.
2377
dx.doi.org/10.1021/om300017u | Organometallics 2012, 31, 2367−2378

Organometallics
Article
(14) (a) Bebbington, M. W. P.; Bontemps, S.; Bouhadir, G.;
Bourissou, D. Angew. Chem., Int. Ed. 2007, 46, 3333. (b) Moebs-
Sanchez, X.; Bouhadir, G.; Saffon, N.; Maron, L.; Bourissou, D. Chem.
(c) Leitner, W. Coord. Chem. Rev. 1996, 153, 257. (d) Sakakura, T.;
Choi, J.-C.; Yasuda, H. Chem. Rev. 2007, 107, 2365.
(30) Voss, T.; Chen, C.; Kehr, G.; Nauha, E.; Erker, G.; Stephan, D.
W. Chem. Eur. J. 2010, 16, 3005.
(31) (a) Binnewitz, R.-J.; Klingenberger, H.; Paetzhold, P. Chem. Ber.
1983, 116, 1271. (b) Jiang, C. F.; Blacque, O.; Berke, H.
Organometallics 2010, 29, 125.
Commun. 2008, 3435. (c) Momming, C. M.; Kehr, G.; Wibbeling, B.;
̈
Frohlich, R.; Erker, G. Dalton Trans. 2010, 39, 7556. (d) Stute, A.;
̈
Kehr, G.; Frohlich, R.; Erker, G. Chem. Commun. 2011, 47, 4288.
(15) Dureen, M. A.; Brown, C. C.; Stephan, D. W. Organometallics
̈
(32) (a) Chen, C.; Eweiner, F.; Wibbeling, B.; Frohlich, R.; Senda, S.;
̈
2010, 29, 6594.
Ohki, Y.; Tatsumi, K.; Grimme, S.; Kehr, G.; Erker, G. Chem. Asian J.
(16) (a) Otten, E.; Neu, R. C.; Stephan, D. W. J. Am. Chem. Soc.
2009, 131, 9918. (b) Neu, R. C.; Otten, E.; Stephan, D. W. Angew.
Chem., Int. Ed. 2009, 48, 9709. (c) Neu, R. C.; Otten, E.; Lough, A.;
Stephan, D. W. Chem. Sci. 2011, 2, 170.
2010, 5, 2199. (b) Chen, C.; Kehr, G.; Frohlich, R.; Erker, G. J. Am.
̈
Chem. Soc. 2010, 132, 13594. (c) Dierker, G.; Ugolotti, J.; Kehr, G.;
Frohlich, R.; Erker, G. Adv. Synth. Catal. 2009, 351, 1080. (d) Chen,
̈
C.; Frohlich, R.; Kehr, G.; Erker, G. Chem. Commun. 2010, 46, 3580.
̈
(17) Cardenas, A. J. P.; Culotta, B. J.; Warren, T. H.; Grimme, S.;
(e) Ekkert, O.; Frohlich, R.; Kehr, G.; Erker, G. J. Am. Chem. Soc.
2011, 133, 4610. (f) Chen, C.; Frohlich, R.; Kehr, G.; Erker, G. Org.
Lett. 2011, 13, 62.
̈
Stute, A.; Frohlich, R.; Kehr, G.; Erker, G. Angew. Chem., Int. Ed. 2011,
̈
̈
50, 7567.
(18) Jiang, C. F.; Blacque, O.; Berke, H. Organometallics 2009, 28,
5233.
(33) Tilley, J. N.; Sayigh, A. A. R. J. Org. Chem. 1963, 28, 2076.
(34) Otwinowski, Z.; Minor, W. Methods Enzymol. 1997, 276, 307.
(35) Otwinowski, Z; Borek, D.; Majewski, W.; Minor, W. Acta
Crystallogr. 2003, A59, 228.
(36) Cromer, D. T.; Waber, J. T. International Tables for X-Ray
Crystallography; Kynoch Press: Birmingham, U.K., 1974; Vol. 4, p 71.
(37) (a) Sheldrick, G. M. SHELXTL; Bruker AXS, Madison, WI,
2000. (b) Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467.
(c) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112.
(19) (a) Sumerin, V.; Schulz, F.; Nieger, M.; Atsumi, M.; Wang, C.;
Leskela, M.; Pyykko, P.; Repo, T.; Rieger, B. J. Organomet. Chem.
2009, 694, 2654. (b) Sumerin, V.; Schulz, F.; Atsumi, M.; Wang, C.;
Nieger, M.; Leskela, M.; Repo, T.; Pyykko, P.; Rieger, B. J. Am. Chem.
Soc. 2008, 130, 14117. (c) Schulz, F.; Sumerin, V.; Leskela, M.; Repo,
T.; Rieger, B. Dalton Trans. 2010, 39, 1920.
(20) (a) Geier, S. J.; Stephan, D. W. J. Am. Chem. Soc. 2009, 131,
3476. (b) Geier, S. J.; Gille, A. L.; Gilbert, T. M.; Stephan, D. W. Inorg.
Chem. 2009, 48, 10466.
(21) (a) Hughes, R. P.; Kovacik, I.; Lindner, D.; Smith, J. M.;
Willemsen, S.; Zhang, D.; Guzei, I. A.; Rheingold, A. L. Organometallics
2001, 20, 3190. (b) Millot, N.; Santini, C. C.; Fenet, B.; Basset, J. M.
Eur. J. Inorg. Chem. 2002, 3328. (c) Di Saverio, A.; Focante, F.;
Camurati, I.; Resconi, L.; Beringhelli, T.; D’Alfonso, G.; Donghi, D.;
Maggioni, D.; Mercandelli, P.; Sironi, A. Inorg. Chem. 2005, 44, 5030.
(d) Focante, F.; Mercandelli, P.; Sironi, A.; Resconi, L. Coord. Chem.
Rev. 2006, 250, 170. (e) Sumerin, V.; Schulz, F.; Nieger, M.; Leskela,
M.; Repo, T.; Rieger, B. Angew. Chem., Int. Ed. 2008, 47, 6001.
(f) Unverhau, K.; Lubbe, G.; Wibbeling, B.; Frohlich, R.; Kehr, G.;
Erker, G. Organometallics 2010, 29, 5320. (g) Venne-Dunker, S.; Kehr,
G.; Frohlich, R.; Erker, G. Organometallics 2003, 22, 948. (h) Liptau,
̈
P.; Neumann, M.; Erker, G.; Kehr, G.; Frohlich, R.; Grimme, S.
̈
Organometallics 2004, 23, 21.
(22) Voss, T.; Sortais, J.-B.; Frohlich, R.; Kehr, G.; Erker, G.
̈
Organometallics 2011, 30, 584.
(23) (a) Brown, H. C.; Schlesinger, H. I.; Cardon, S. Z. J. Am. Chem.
Soc. 1942, 64, 325. (b) Wittig, G.; Benz, E. Chem. Ber. 1959, 92, 1999.
(c) Brown, H. C.; Kanner, B. J. Am. Chem. Soc. 1966, 88, 986.
(d) Tochtermann, W. Angew. Chem., Int. Ed. 1966, 5, 351.
(24) (a) Jacobsen, H.; Berke, H.; Doring, S.; Kehr, G.; Erker, G.;
̈
Frohlich, R.; Meyer, O. Organometallics 1999, 18, 1724. (b) Kehr, G.;
̈
Frohlich, R.; Wibbeling, B.; Erker, G. Chem. Eur. J. 2000, 6, 258.
(c) Vagedes, D.; Erker, G.; Kehr, G.; Bergander, K.; Kataeva, O.;
̈
Frohlich, R.; Grimme, S.; Muck-Lichtenfeld, C. Dalton Trans. 2003,
̈
̈
1337. (d) Flierler, U.; Leusser, D.; Ott, H.; Kehr, G.; Erker, G.;
Grimme, S.; Stalke, D. Chem. Eur. J. 2009, 15, 4595. (e) Geier, S. J.;
Chase, P. A.; Stephan, D. W. Chem. Commun. 2010, 46, 4884.
(25) (a) Jessop, P. G.; Heldebrant, D. H.; Li, X.; Eckert, C. A.; Liotta,
C. L. Nature 2005, 436, 1102. (b) Liu, Y.; Jessop, G. P.; Cunningham,
M.; Eckert, C. A.; Liotta, C. L. Science 2006, 313, 958. (c) Dickie, D.
A.; Parkes, M. V.; Kemp, R. A. Angew. Chem., Int. Ed. 2008, 47, 9955.
(26) (a) Fichter, F.; Becker, B. Chem. Ber. 1911, 3481. (b) Werner, E.
A. J. Chem. Soc. 1920, 117, 1046. (c) Belli Dell’Amico, D.; Calderazzo,
F.; Labella, L.; Marchetti, F.; Pampaloni, G. Chem. Rev. 2003, 103,
3857.
(27) (a) Ashley, A. E.; Thompson, A. L.; O’Hare, D. Angew. Chem.,
Int. Ed. 2009, 48, 9839. (b) Berkefeld, A.; Piers, W. E.; Parvez, M. J.
Am. Chem. Soc. 2010, 132, 10660.
(28) Mitu, S.; Baird, M. C. Can. J. Chem. 2006, 84, 225.
(29) (a) Braunstein, P.; Matt, D.; Nobel, D. Chem. Rev. 1988, 88,
747. (b) Jessop, P. G.; Ikariya, T.; Noyori, R. Chem. Rev. 1995, 95, 259.
2378
dx.doi.org/10.1021/om300017u | Organometallics 2012, 31, 2367−2378