Synthesis and reactivity of alkynyl-linked phosphonium borates

Article abstract of DOI:10.1002/chem.201100203

The phosphine tBu₂PC≡CH (1) was reacted with B(C ₆F₅) to give the zwitterionic species tBu ₂P(H)C≡CB(C₆F₅)₃ (2). The analogous species tBu₂P(Me)C≡CB(C₆F

Full text of DOI:10.1002/chem.201100203

FULL PAPER
DOI: 10.1002/chem.201100203
Synthesis and Reactivity of Alkynyl-Linked Phosphonium Borates
Xiaoxi Zhao, Alan J. Lough, and Douglas W. Stephan*[a]
ꢀ
ꢀ
Abstract: The phosphine tBu2PC CH
the
zwitterionic
product
N
ACHTNUGRTNE(NGNU C6F5)2][O-
(1) was reacted with B
A
(C6F5)2(H)BC(H)=C
A
ꢀ
ꢀ
ꢀ
the zwitterionic species tBu2P(H)C
G
tBu2PC CB
the formation of {[tBu2PC CB
[O(CH2)4]}2 (17). In a related example,
ACHTNUGTRNE(NNUG C6F5)2 with THF lead to
ꢀ
CB
(C6F5)3
(2).
The
analogous
ACHTUNGTRENNUNG(C6F5)2]
ꢀ
species tBu2P(Me)C CB
G
phine–borane generated in situ from 5,
with 1-hexene gave the species
[tBu2PC CB
[tBu2PC CB
quent reaction with methanol or
hexene resulted in the formation of
ACHTUNGTRENNUNG
ꢀ
ꢀ
tBu2P(H)C CB(Cl)
G
the reaction of Mes2PC CBACHTUNGTRENNUNG(C6F5)2
with PhC CH gave {[Mes2PC CB-
ꢀ
ꢀ
ꢀ
tBu2P(H)C CB(H)
G
ꢀ
tBu2P(Me)C CB(H)
U
(C6F5)2]
N
ꢀ
also prepared. The salt [tBu2P(H)C
reacted with AlX3 (X=Cl, Br) to give
addition to the alkynyl unit, affording
CB
prepared through abstraction of hy-
dride by [Ph3C][B(C6F5)4]. Species 5 re-
A
E
(C6F5)4] (7) was
ꢀ
[tBu2P(H)C CB
(C6F5)2BC(H)=C[P(H)tBu2]
(X=Cl 19, Br 20). In a similar fashion,
5 reacted with [Zn(C6F5)2]·C7H8, [Al-
(C6F5)3]·C7H8, or HB(C6F5)2 to give
(C6F5)3BC(H)=C[P(H)tBu2][Zn(C6F5)]
(21), (C6F5)3BC(H)=C[P(H)tBu2][Al-
(C6F5)2] (22), or [(C6F5)2B]2HC=
CH[P(H)tBu2] (23), respectively. The
implications of this reactivity are dis-
cussed.
ACHTUNGERTN(NUNG AlX3)
N
(CH2CHnBu)[tBu2PC CB
acted with the imine tBuN=CHPh to
(OMe) (14) or the macrocycle
{[tBu2PC CB
(15), respectively. In a related fashion,
the reaction of 13 with THF afforded
ACHTUNGTRENNUNG
ꢀ
give the borane–amine adduct tBu2PC
A
ACHTUNGTRENNUNG
CB
[tBuN(H)CH2Ph]
(C6F5)2 (8). The
ACHTUNGTRENNUNG
ꢀ
related phosphine Mes2PC CH (9;
Mes=C6H2Me3) was used to prepare
the macrocycle [tBu2PC CB
ACHTUNGTRENNUNG
ꢀ
[tBu3PH][Mes2PC CB
(C6F5)3] (10) and
ꢀ
generate
adduct
Mes2PC CB
G
The
ACHTNUGRTEN(NGNU C6F5)2
Keywords: boranes · borates · frus-
trated Lewis pairs · phosphanes ·
phosphonium borates · zwitterions
ꢀ
Mes2PC CB
U
(11) was isolated. Reaction of
ꢀ
Mes2PC CB
(C6F5)2 with H2 gave
Introduction
tives have been developed from the reactions of sterically
encumbered ꢀfrustrated Lewis pairsꢁ (FLPs) with a variety
of small molecules including olefins,[11–14] alkynes,[15–19]
CO2,[20–22] and N2O.[23,24] In the case of the reactions of FLPs
with alkynes, we have shown that a variety of Lewis bases,
including phosphines,[15,17] polyphosphines,[16] amines, thio-
ethers,[18] and pyrroles,[19] will effect addition reactions to
give alkenyl-linked zwitterionic products.
Interest in the chemistry of zwitterionic phosphonium bo-
rates garnered particular attention in 2006 with the finding
that the species Mes2P(H)C6F4B(H)ACHTUNGTRENUNG(C6F5)2 (Mes=
C6H2Me3) reversibly liberates and takes up H2.[1] This unpre-
cedented heterolytic cleavage of H2 by a metal-free main-
group system was attributed to the cooperative action of un-
quenched Lewis acidity and basicity on H2. The inability of
these systems to form conventional Lewis acid–base adducts
results from steric congestion. Based on this observation,
subsequent findings have led to the development of effective
metal-free catalysts for the hydrogenation of imines,[2–8] azir-
idines, and protected nitriles.[2,3] Related alkyl-linked zwit-
In general, alkynyl-linked zwitterions have drawn less at-
tention, although Uhl and co-workers have recently shown
that alkynylphosphines react with alanes to give unusual
cyclic phosphonium aluminates.[25] To explore the reactivity
of alkynyl-linked zwitterionic phosphonium borates, we
have recently begun an investigation of the chemistry of the
ꢀ
terions, such as Mes2P(H)C2H4B(H)
N
alkynyl zwitterion tBu2P(H)C CB(H)ACHTNGUTERNU(NG C6F5)2. Interestingly,
discovered and shown to catalyze the hydrogenation of en-
amines,[4,9] silylenol ethers,[6] and selected N heterocycles.[10]
In addition, new synthetic routes to such zwitterionic deriva-
this species reacts with a Ni0 source with loss of H2 to gener-
ate a Ni–alkyne complex in which B bends towards the Ni,
[26]
À
giving rise to an unusual Ni B interaction (Scheme 1).
We have also shown that a related zwitterion undergoes
thermal rearrangement to give a unique cumulene deriva-
[a] X. Zhao, Dr. A. J. Lough, Prof. Dr. D. W. Stephan
Department of Chemistry, University of Toronto
80 St. George St., Toronto, Ontario, M5S 3H6 (Canada)
Fax : (+1)416-978-7551
tive, (tBu2P)C6F4B(F)CATHNUGETNRGNNU(C6F5)C4ACHUTGNTRNENUG(C6F5)2BAHCTUNGERTNGN(NU CH2CHnBu)ACHTUNGTRENNUNG(PtBu2)
(Scheme 1).[27] Herein, we describe an exploration of the
ꢀ
generation and reactions of R2PC CB
These “push–pull” alkynyl-linked phosphine boranes are
G
E-mail: dstephan@chem.utoronto.ca
Chem. Eur. J. 2011, 17, 6731 – 6743
ꢂ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
6731

Scheme 1. Reactions of alkynylphosphonium borates. COD=1,5-cyclooc-
tadiene.
Scheme 2. Synthesis of 1–8.
shown to behave as FLPs, affording unique routes to macro-
ꢀ
cyclic dizwitterions. In addition, tBu2P(H)C CB(H)
gives interesting Lewis acid addition products. The nature of
the products is described and the implications are discussed.
G
Results and Discussion
Synthesis of alkynylphosphonium borates: The phosphine
ꢀ
tBu2PC CH (1) was prepared by using a modified literature
method[28] and was then reacted with B
(C6F5)3 in toluene.
The workup gave off-white product 2 in 88% yield. The H
and 31P{1H} NMR spectral data for 2 revealed a resonance
attributable to a PH fragment and the P chemical shift was
consistent with a phosphonium cation. The 11B{1H} NMR
chemical shift of 2 at À21.4 ppm was consistent with the
presence of a borate fragment. The 19F NMR spectrum of 2
showed resonances consistent with the C6F5 rings. These
data, together with mass spectrometry data and elemental
analyses, support the formula of 2 being the zwitterionic
ꢀ
species tBu2P(H)C CBACTHUNTRGNE(GNU C6F5)3 (Scheme 2). An X-ray crys-
tallographic study of 2 confirmed this formulation (Fig-
À
ꢀ
ure 1a) with a central C C bond of 1.217(4) ꢃ and PC C
Figure 1. POV-ray depictions of a) 2 and b) 3.
ꢀ
and C CB angles of 171.2(2) and 174.9(3)8, respectively.
Subsequent reaction of 2 with MeLi, followed by treatment
with MeI gave 3 in 58% yield. The 31P{1H} NMR chemical
shift at 32.8 ppm and the 1H NMR doublet for PCH3 at
1.71 ppm are consistent with the structure of 3 being
ꢀ
a
11B{1H} NMR signal at À12.8 ppm, consistent with the
presence of a borate unit. The 31P{1H} NMR spectrum also
gives a signal at 25.5 ppm, shifted downfield from the reso-
nance of the alkynylphosphine (Scheme 2). Collectively
tBu2P(Me)C CBACHTUNGTRENNUNG(C6F5)3. This was also confirmed crystallo-
graphically (Figure 1b).
ꢀ
In an analogous fashion, the reaction of 1 with ClB
(C6F5)2
these data infer that the formula of 4 is tBu2P(H)C CB(Cl)-
proceeds easily at À358C to give the new off-white product
A
4 in 72% isolated yield. Similar to 2, compound 4 exhibits a
crystallography, following isolation of suitable crystals from
CH2Cl2/pentane (Figure 2a). The metric parameters of 4
were similar to those in 2 and 3, with a B Cl bond length of
1
À
H NMR doublet resonance at 5.80 ppm, with a P H cou-
À
pling constant of 469 Hz, which is indicative of the presence
of a PH phosphonium fragment. Compound 4 also exhibits
1.911(4) ꢃ.
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Alkynyl-Linked Phosphonium Borates
FULL PAPER
two 11B{1H} NMR signals at À3.2 and À16.6 ppm correspond
to B bound to THF and the [BACHTUNRGTEN(UNG C6F5)4] anion, respectively,
inferring abstraction of hydride to form the alkynylphospho-
nium borate cation. These data, together with other NMR
ꢀ
spectra, are consistent with 7 being [tBu2P(H)C CB
ACHUTNGERNU(NG THF)][BACHTUNGTREN(NNGU C6F5)4] (Scheme 2).
G
Species 5 also reacts with the imine tBuN=CHPh in 2 h at
258C to give colorless crystals of 8 in 57% yield. The
1H NMR data infer the loss of the signals arising from both
the PH and BH groups and the generation of new resonan-
ces at 5.10 and 3.75 ppm, attributable to the NH and CH2
groups in the amine tBuN(H)CH2Ph. The 31P{1H} NMR res-
onance at 18.6 ppm suggests a phosphine fragment and the
11B{1H} NMR spectrum shows a broad signal at À9.6 ppm.
Together with the 19F NMR spectrum, these data infer the
ꢀ
formation of the borane–amine adduct tBu2PC CB-
[tBuN(H)CH2Ph]
R
quently confirmed by an X-ray crystal structure (Figure 3).
Figure 2. POV-ray depictions of a) 4 and b) 5.
Treatment of 4 with excess Me2SiHCl results in exchange
À
of the B-bound chloride for hydride, generating a B H unit
and Me2SiCl2. The resulting off-white product 5 was isolated
in 79% yield (Scheme 2). The NMR data confirm the re-
placement of chloride by hydride, as shown by the observa-
Figure 3. POV-ray depiction of 8.
À
tion of a 1:1:1:1 quartet at 3.25 ppm with a B H coupling
constant of 91 Hz, and the 11B{1H} NMR resonance shifts to
The formation of 8 results from proton and hydride transfer
to the imine. Although imine reductions have previously
been shown to be catalytic with aryl- and alkyl-linked phos-
phonium borates,[2,29] efforts to utilize 5 as a catalyst to
effect the hydrogenation of the imine tBuN=CHPh under an
H2 atmosphere at 808C were unsuccessful. This was attribut-
ed to the inherent reactivity of the polarized alkyne unit in
5, as these reactions afforded a complex mixture of unidenti-
fied degradation products. It is noteworthy that alkynylbor-
anes with strongly electron-withdrawing substituents on B
have been reported to be unstable at room temperature
and/or in the solid state.[30,31]
À29.2 ppm. One of the acetylenic carbon atoms is observed
in the 13C NMR spectrum at 64.4 ppm with a JCP of 158 Hz.
1
The resonance for the B-bound acetylenic carbon was not
observed, presumably due to quadrupolar broadening aris-
ing from the adjacent B center. Nonetheless, infrared data
revealed an absorption at 2125 cmÀ1, in accord with the
presence of the acetylenic unit. The proposed connectivity
ꢀ
for 5, tBu2P(H)C CB(H)ACHTNUGTRENUNG(C6F5)2, was confirmed through
X-ray crystallography (Figure 2b), which showed the metric
parameters and geometry to be unexceptional. Interestingly,
viewing the molecule along the PC CB vector in the solid
state, it is noted that the substituents on B and P are
eclipsed, with the BH and PH groups occupying the same
plane.
ꢀ
To probe the impact of substituent variation, the phos-
ꢀ
phine Mes2PC CH (9) was prepared by employing a proce-
dure analogous to that used to synthesize 1. Phosphine 9
In a procedure similar to that used to prepare 3, deproto-
nation of 5 with MeLi and subsequent treatment with MeI
was isolated as colorless crystals in 45% yield. The acetylen-
1
ic proton gave rise to a H NMR resonance at 2.65 ppm and
afforded tBu2P(Me)C CB(H)ACHTNUGRTNEUNG(C6F5)2 (6) in 84% yield. This
the 31P{1H} NMR resonance was observed at À54.5 ppm.
Compound 9 was also characterized crystallographically (see
the Supporting Information), confirming the incorporation
ꢀ
formulation is consistent with the 1H NMR resonances at
1.72 ppm and 3.20 ppm, arising from the P-bound methyl
À
group and the preserved B H fragment, respectively. In a
of the alkynyl fragment. The reaction of 9 with BACTHUNGTERNNU(G C6F5)3 and
related reaction of 5, treatment with [Ph3C][B
A
PtBu3 gave crystalline product 10 in 87% yield. This species
gave rise to 31P{1H} NMR resonances at 61.4 and À52.9 ppm,
with a 11B{1H} NMR signal at À20.9 ppm, consistent with
the presence of a borate unit and supporting the structure of
ꢀ
ed in the generation of [tBu2P(H)C CB
which was not stable enough to be isolated in pure form. In-
stead, it was isolated as THF adduct 7 in 77% yield. The
N
ACHTUNGTRENNUNG
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6733

D. W. Stephan et al.
ꢀ
10 being the salt [tBu3PH][Mes2PC CB
unambiguously confirmed crystallographically (Scheme 3,
Figure 4). It is noteworthy that the use of B(C6F5)3 and the
AHCTNUGTER(GNNUN C6F5)3]. This was
(Scheme 3). The 11B{1H} NMR signal observed at À12.6 ppm
and the 19F NMR signals at À133.9, À157.9, and À164.5 ppm
are consistent with the quaternized B center and the
31P{1H} NMR resonance at À53.0 ppm is consistent with a
phosphine fragment. Crystallographic data confirmed this
AHCTUNGTRENNUNG
sterically hindered, yet basic, phosphine PtBu3 to effect de-
protonation of the alkyne, affording alkynylborate salts, has
been previously shown to be one of the general reactions of
FLPs with terminal alkynes.[15]
À
structure (Figure 5) and revealed a B N bond length of
1.596(2) ꢃ.
Figure 5. POV-ray depiction of 11.
ꢀ
Exposure of a solution of the phosphine–borane Mes2PC
CB
A
isolation of 12 in 37% yield. The H and 19F NMR spectra
of 12, obtained at room temperature, contained substantially
broadened signals, presumably due to high degrees of rota-
tional inhibition of the bulky substituents. The 19F NMR
spectrum measured at 1008C revealed resonances indicative
1
Scheme 3. Synthesis of 10–12.
of two distinct BACTHNUTRGNEUNG
(C6F5)2 groups. Similarly, the 11B{1H} NMR
data showed signals at À16.9 (a doublet with coupling to P)
and À20.3 ppm (broad singlet). Meanwhile, the 1H NMR
spectrum obtained at 1008C showed the presence of an ole-
finic H coupled to P, two distinct Mes2PH groups, and a BH
signal. The 31P{1H} NMR resonances also indicated two envi-
ronments, with signals at À23.3 and À48.7 ppm. The precise
nature of 12 was unambiguously determined by crystallogra-
ꢀ
phy to be (C6F5)2(H)BC(H)=C[P(H)Mes2]ACHTUNGRTNEUNG[(C6F5)2BC
Figure 4. POV-ray depiction of the anion of 10.
CP(H)Mes2] (Scheme 3, Figure 6). These data reveal that
the phosphine–borane activates H2, although the mechanism
for the formation of 12 is unclear. Presumably, the transient-
ꢀ
ꢀ
Efforts to form the analogous salt [tBu3PH][Mes2PC
ly formed H2 activation species Mes2P(H)C CB(H)ACHTUNGTRENNUNG(C6F5)2
ꢀ
CBCl
G
N
(C6F5)3
reacts with the starting material Mes2PC CB
effect Lewis acid mediated hydride migration from B to the
adjacent acetylenic carbon (examples shown later), followed
G
resulted in loss of Cl. This is due to the greater Lewis acidity
ꢀ
of ClB
two equivalents of ClB
and PtBu3 to generate Mes2PC CB
[Cl2B(C6F5)2]. Subsequent precipitation of the salt byprod-
A
(C6F5)2. Thus,
A
ꢀ
AHCUTNERTGGN(UNN C6F5)2 and [tBu3PH]-
N
ACHTUNGTRENNUNG
uct left the alkynylphosphine borane as a red–orange solu-
tion. NMR spectra of the solution in [D8]toluene revealed
19F resonances at À128.9, À147.5, and À162.0 ppm, indicat-
ing the presence of a 3-coordinate B centre, as well as giving
a
31P{1H} signal at À53.4 ppm, attributable to the formation
ꢀ
of Mes2PC CB
Mes2PC CB
tivity of its polarized alkynyl fragment. Nonetheless, addi-
G
ꢀ
N
tion of acetonitrile allowed the isolation of the yellow
ꢀ
adduct Mes2PC CB
G
G
Figure 6. POV-ray depiction of 12.
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Alkynyl-Linked Phosphonium Borates
FULL PAPER
by addition of another H2 molecule to generate dissymmet-
ric dizwitterion 12. This reactivity stands in stark contrast to
the reversible H2 activation that allows the facile intercon-
version of Mes2PC6F4B
ACHTGNURTNE(NUGN C6F5)2 and Mes2P(H)C6F4B(H)-
ACHTUNGTRENNUNG
system demonstrates reactivity typical of an FLP, this reac-
tivity precludes its use as a hydrogenation catalyst.
ꢀ
The corresponding neutral phosphine–borane, tBu2PC
CB
tBu3P and B
[HB(C6F5)3] as a byproduct (Scheme 2). This reaction results
from the greater basicity and acidity of tBu3P and B(C6F5)3,
A
ACHTUNGTRENNUNG(C6F5)3, generating the known salt [tBu3PH]
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
respectively. Although attempts to isolate the neutral species
resulted in unidentified decomposition products, the forma-
tion of the phosphine–borane was confirmed by 11B, 19F, and
31P NMR analysis of the reaction mixture. This phosphine–
borane generated in situ has previously been found to react
ꢀ
with 1-hexene in a ratio of 1:1 to give the species [tBu2PC
ꢀ
CB
G
G
N
subsequently undergoes thermolysis to give the dissym-
metric
A
cumulene
(tBu2P)C6F4B(F)ACTHGNURTEN(UNG C6F5)C4ACHTNUGTREN(NUNG C6F5)2B-
(PtBu2).[27] Although 13 could not be structur-
ally characterized, simple treatment of 13 with methanol re-
sulted in the protonation of its free phosphine center with
ꢀ
methoxide binding to B, affording [tBu2P(H)C CB
(C6F5)2]-
ꢀ
A
N
T
(Scheme 4). This species was crystallized and the structural
data confirmed this formulation (Figure 7).
Macrocyclic zwitterionic alkynylphosphonium borates: In
probing the reactivity of the above species, we sought to ex-
ploit these compounds to form macrocyclic products
through FLP reactivity. To that end, an excess of 1-hexene
was combined with 13 and heated to 808C to form a new
species, 15. Although the formation of the previously report-
ed cumulene derivative was a competing reaction, com-
pound 15 was isolated in 28% yield due to its lower solubili-
ty. The 11B{1H} NMR spectrum of 15 shows a broad peak at
À18.1 ppm and the 31P{1H} NMR signals at 43.0 and
41.3 ppm are consistent with the formation of a mixture of
diastereomers arising from P/B addition to a second equiva-
Scheme 4. Synthesis of 14–18.
1
lent of olefin. H and 19F NMR data were also in agreement
with the generation of two diastereomers. It was speculated
that these data are consistent with the dimeric formula
Figure 7. POV-ray depiction of 14.
ꢀ
{[tBu2PC CB
N
tion that was confirmed crystallographically (Figure 8). In-
terestingly, the P/B alkynyl fragment adopts a quasi-parallel
geometry. The macrocyclic nature of 15 results in intramo-
oriented at an angle of 23.38 with respect to each other. An
À
À
lecular P P and B B distances of 5.82 and 5.40 ꢃ, respec-
tively.
expanded macrocycle is also accessible through treatment of
ꢀ
tBu2PC CB
G
In other work, we have demonstrated that FLPs are capa-
ble of effecting ring-opening reactions of THF,[32] as well as
dioxane and thioxane.[33] Herein, we exploit this reactivity to
prepare a dissymmetric macrocyclic species through reaction
of 13 with THF. This reaction affords the new macrocycle
alone. This leads to ring opening of THF and the formation
ꢀ
of {[tBu2PC CB
yield. Although the spectroscopic data are as expected, the
crystallography data (Figure 10) reveals that the symmetry
G
G
ꢀ
of macrocycle 17 again orients the PC CB fragments in an
ꢀ
ꢀ
[tBu2PC CB
(C6F5)2]
N
E
approximately parallel orientation with a dihedral angle of
À
À
U
40.38, although the intramolecular P P and B B distances
have lengthened to 6.67 and 7.96 ꢃ, respectively.
ꢀ
macrocycle 16 (Figure 9) results in PC CB vectors being
Chem. Eur. J. 2011, 17, 6731 – 6743
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6735

D. W. Stephan et al.
Figure 11. POV-ray depiction of 18.
Figure 8. POV-ray depiction of 15.
Figure 9. POV-ray depiction of 16.
Figure 10. POV-ray depiction of 17.
Reactions of alkynylphosphonium borates with Lewis
acids: In exploring a final aspect of the reactivity of alkynyl-
phosphonium borates, the reactivity with several Lewis acids
was probed. Phosphonium borate 5 was reacted with AlCl3
in toluene. After stirring overnight at 258C and subsequent
workup, a new white solid 19 was isolated in 74% yield. The
31P{1H} NMR spectrum of 19 showed a broad signal at
76.9 ppm and an 27Al resonance was seen at 103.8 ppm. The
11B{1H} NMR signal at 12.6 ppm and the 19F NMR resonan-
ces at À130.1, À155.3, and À163.9 ppm were all broad, sug-
1
gesting some fluxional behavior. H NMR data were consis-
tent with the retention of the P H fragment, as a doublet
was observed at 5.42 ppm with a JHP of 429 Hz. In addition,
À
1
À
a doublet at 8.23 with P H coupling of 45.9 Hz suggested
the reduction of the alkynyl fragment and formation of
a =CH fragment. This view was supported by the observa-
tion of a 13C{1H} NMR signal at 186.9 ppm. In a similar fash-
ion, the corresponding reaction with AlBr3 led to the forma-
tion and isolation of 20 in 48% yield. The NMR data for 20
were similar to those seen for 19. Both products were struc-
turally characterized by X-ray crystallography to be
(C6F5)2BC(H)=C[P(H)tBu2]ACTHNUGRTENUNG(AlX3) (X=Cl (19), Br (20);
Scheme 5, Figure 12). The two products are similar pseudo-
five-membered rings in which the alkynyl fragment is for-
mally reduced to an alkenyl group. Hydride has migrated
from boron to the adjacent carbon atom and AlX3 binds to
the carbon atom adjacent to the phosphonium fragment
with a halide atom bridge to boron. The Al C distances in
19 and 20 are 1.958(3) and 1.965(3) ꢃ, respectively, although
the resulting C=C bond lengths are identical (1.344(4) ꢃ).
À
À
In a final example of the use of FLP reactivity to generate
The corresponding B halide distances were found to be
ꢀ
macrocycles, the phosphine–borane Mes2PC CB
(C6F5)2 was
2.198(3) and 2.343(4) ꢃ, respectively. These comparatively
large separations are consistent with the fluxional behavior
of 19 and 20 in solution. Examination of the dynamic behav-
ior of 19 and 20 by low temperature NMR proved difficult
due to their low solubilities.
ꢀ
reacted with PhC CH. We have previously shown that FLPs
that include less basic donors will effect donor and acceptor
addition to the alkyne. In the present case, this results in the
ꢀ
formation of the macrocyclic product {[Mes2PC CBACHTNUTGRENUNG(C6F5)2]-
(CH=CPh)}2 (18; Scheme 4, Figure 11). This species is remi-
In a similar fashion, the reaction of 5 with the Lewis acid
niscent of the previously reported macrocyclic species
[ZnACHTGUNETRN(NUG C6F5)2]·C7H8 afforded a new white solid 21 in 70%
{[Mes2PC6F4B(C6F5)2]
G
R
yield. This new species exhibited a 31P NMR resonance at
ꢀ
À
the linkages enforces an approximately planar [PC CBC=
C]2 core, with a maximum deviation from the mean-square
plane of 0.181 ꢃ.
73.6 ppm with P H coupling of 425 Hz shown in the
1H NMR spectrum and 19F NMR signals at À130.4, À158.8,
and À163.6 ppm. These resonances, together with the
6736
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ꢂ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 6731 – 6743

Alkynyl-Linked Phosphonium Borates
FULL PAPER
Figure 13. POV-ray depiction of 21.
derivative. The metric parameters within the borate and
phosphonium fragments are as expected. Zn is bound to the
olefinic fragment, adopting a linear two-coordinate geome-
À
try with a C-Zn-C angle of 172.66(7)8 and Zn C distances
to the olefinic and fluoroaryl fragments of 1.928(2) and
1.935(2) ꢃ, respectively.
The analogous reaction of 5 with [AlACHTUNRTGNE(UNG C6F5)3]·C7H8 pro-
Scheme 5. Synthesis of 19–23.
ceeded in a similarly smooth fashion to give 22 in 61%
yield. The 19F NMR spectrum reveals broad signals that can
be attributed to two types of C6F5 group which integrate to
a 3:2 ratio whereas the sharp 11B resonance at À13.8 ppm is
consistent with a 4-coordinate B center. The solid-state
structure of 22 was unambiguously confirmed by X-ray crys-
tallography to be (C6F5)3BC(H)=C[P(H)tBu2][AlACHTUNGTRENNUNG(C6F5)2]
(22; Scheme 5, Figure 14). In this species the Al has added
Figure 12. POV-ray depiction of a) 19 and b) 20.
Figure 14. POV-ray depiction of 22.
11B signal at À12.9 ppm are consistent with the presence of
to the C attached to the phosphonium center and the hy-
dride from B has added to the adjacent C atom, resulting in
a central olefinic fragment. Interestingly, a C6F5 group has
migrated to B, affording an anionic BACHTNURGTNEUNG(C6F5)3 borate unit.
One of the ortho-fluorine atoms on the aryl rings on B coor-
a borate fragment derived from BACTHNUTRGNE(UNG C6F5)3. Additionally, inte-
gration of the 19F NMR signals at À117.5, À151.7, and
À160.5 ppm are consistent with the presence of an addition-
al C6F5 ring, presumably on Zn. Compound 21 also gives
1
rise to H signals at 8.92 and 5.28 ppm, attributable to ole-
dinates to the formally unsaturated Al center with an Al···F
À
finic CH and PH fragments, respectively. These data are
consistent with 21 being derived from the combination of
the reactants although determining the exact nature of 21
required a crystallographic study. These data unambiguously
confirmed the formula of 21 to be (C6F5)3BC(H)=
of 1.926 ꢃ. A number of reports have described such Al F
interactions.[35,36] It is interesting to note that transfer of a
C6F5 group normally proceeds from B to Al.[34] However, in
22, the presence of the phosphonium cation presumably ele-
vates the Lewis acidity of B, as well as the steric congestion
around Al.
C[P(H)tBu2][ZnACHTUNGTRENNUNG(C6F5)] (Scheme 5, Figure 13), a vinylborate
Chem. Eur. J. 2011, 17, 6731 – 6743
ꢂ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
6737

D. W. Stephan et al.
Compound 5 also reacts with the Lewis acid HB
(C6F5)2,
yl-linked phosphine-boranes react as FLPs in reactions such
as the stoichiometric reduction of imines, the addition to
olefins and alkynes, and the ring opening of THF. Exploiting
this reactivity, synthetic routes to novel macrocyclic products
have been developed. In addition alkynylphosphonium bo-
rates were shown to react with a variety of Lewis acids,
prompting hydride transfer from the borohydride fragment
to the alkyne unit, affording reduction to the corresponding
olefin. The unique reactivity of related zwitterionic species
and the application of FLP reactivity in the synthesis of new
materials is still an active area of research in our laborato-
ries.
yielding a new species 23 in 68% isolated yield. The
31P{1H} NMR spectrum of 23 shows a resonance at 55.6 ppm
1
and, along with the H NMR doublet resonance at 4.61 ppm
À
with P H coupling of 433 Hz, is consistent with retention of
the phosphonium fragment. The 11B{1H} NMR spectrum of
23 shows two signals, one broad peak at 60.5 ppm and a
sharp signal at À15.9 ppm. These peaks infer the presence
of three-coordinate borane and four-coordinate borate frag-
ments. The corresponding 19F NMR spectrum showed 18
resonances, suggesting that steric congestion in 23 restricts
1
À
rotation about the B C bonds. The H NMR signals at 3.39
and 2.44 ppm can be attributed to methine protons, suggest-
ing full reduction of the alkynyl fragment. The nature of 23
was unambiguously confirmed by X-ray crystallography to
be [(C6F5)2B]2HC=CH[P(H)tBu2] (Scheme 5, Figure 15).
Experimental Section
General remarks: All manipulations were carried out under an atmos-
phere of dry, O2-free N2 by employing an MBraun glove box and a
Schlenk vacuum line. Solvents were purified with a Grubbs-type column
system manufactured by Innovative Technology and dispensed into thick-
walled Schlenk glass bombs equipped with Young-type Teflon-valve stop-
cocks (hexanes, pentane, toluene, CH2Cl2, THF), or were dried over the
appropriate agents and distilled into the same kind of Young bomb
(C6H5Br, methanol). All solvents were thoroughly degassed after purifi-
cation (repeated freeze–pump–thaw cycles). Deuterated solvents were
dried over the appropriate agents, vacuum-transferred into Young bombs
and degassed accordingly (C6D5Br, CD2Cl2, C6D6, [D8]toluene). NMR
spectra were recorded at 258C on Varian 300 and 400 MHz and Bruker
400 MHz spectrometers unless otherwise stated. Chemical shifts are
given relative to SiMe4 and referenced to the residual solvent signal (1H,
13C) or relative to an external standard (11B: (Et2O)BF3; 19F: CFCl3; 31P:
85% H3PO4). In some instances, signal and/or coupling assignment was
derived from two-dimensional NMR experiments. Chemical shifts are re-
ported in ppm and coupling constants as scalar values in Hz. Combustion
analyses were performed in house by employing a Perkin–Elmer CHN
Figure 15. POV-ray depiction of 23.
Analyzer. Mes2PCl,[38] ClB(C6F5)2,[39] [Zn(C6F5)2]·C7H8,[40] and [Al-
ACTHNUTRGENNUG CAHTUNGTRENNUGN
This species contains a central boratirane ring, with phos-
phonium and borane substituents on the C atoms. Within
[34]
G
were synthesized according to literature preparations.
ꢀ
ꢀ
[tBu2PC CB
(C6F5)2]
E
(C6F5)2] (14) was prepared
as previously reported.[27]
À
À
the BC2 ring, the Bcyclic C(P) and Bcyclic C(B) bonds are
À
1.609(2) and 1.712(2) ꢃ, respectively, whereas the C C
ꢀ
Synthesis of tBu2PC CH (1): This compound was prepared by using a
bond is 1.525(2) ꢃ (average values of the two crystallo-
graphically independent molecules in each asymmetric unit).
The exocyclic phosphonium and planar borane substituents
modification of the literature method.
Method 1: A solution of nBuLi in hexane (1.6m, 10.0 mL, 16.0 mmol)
ꢀ
was added to a solution of HC CSiMe3 (1.567 g, 15.95 mmol) in THF
(20 mL) at 08C. After stirring at 08C for 30 min, ClPtBu2 (3.00 mL,
15.79 mmol) in THF (15 mL) was added to the reaction mixture at
À788C and stirred at that temperature for 30 min. The reaction was then
warmed to room temperature and stirred overnight. THF was evaporated
off completely while the flask was kept in an ice bath. The product mix-
ture was redissolved in pentane (15 mL) and filtered through Celite. The
solvent was evaporated under vacuum with the flask kept in an ice bath
À
À
give rise to P C and B C bond lengths to the boratirane
ring of 1.774(1) and 1.483(2) ꢃ, respectively. In addition, the
B
cyclic-C-P and Bcyclic-C-B angles are 123.25(11) and
112.18(12)8, respectively. These metric parameters, the large
Bcyclic C(B) separation, short exocyclic B C bond length,
and small Bcyclic-C-B angle suggest some degree of hypercon-
jugation in the Bcyclic-C-B moiety,[37] which stabilizes the
structure of 23. This reaction is believed to proceed through
À
À
ꢀ
to give tBu2PC CSiMe3. This product was stirred with potassium carbon-
ate (4.42 g. 32.0 mmol) in methanol (17 mL) overnight followed by filtra-
tion through Celite. Pentane (10 mL) was then added to the filtrate and
the mixture was separated by using a separation funnel under a N2 at-
mosphere. The methanol layer was washed twice with pentane (10 mL).
The combined pentane phase was passed through a plug of neutral alumi-
na to remove any dissolved methanol. Pentane was evaporated off while
the flask was kept in an ice bath. The lightly colored liquid product
(1.915 g, 71%) was used in subsequent reactions without further purifica-
tion. The compound was stored at À358C to avoid decomposition.
initial hydroboration of 5 with HBACHTNUTRGNE(UNG C6F5)2, followed by intra-
molecular hydride transfer from B to its adjacent C atom,
the net effect of which gives the complete reduction of the
alkynyl group in 5.
Method 2: The same procedure as above was used for the generation of
Conclusion
ꢀ
tBu2PC CSiMe3. This product was then stirred with potassium carbonate
in methanol (8 mL) overnight followed by filtration through Celite and
washing with pentane (20 mL). The filtrate was then passed through a
column of neutral alumina and washed with pentane. Pentane was
The results presented herein demonstrate synthetic routes to
a variety of alkynylphosphonium borate derivatives. Alkyn-
6738
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ꢂ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 6731 – 6743

Alkynyl-Linked Phosphonium Borates
FULL PAPER
ꢀ
pumped off while the flask was kept in an ice bath to give the product
Synthesis of tBu2P(H)C CB(H)AHCTUNGTER(GNNUN C6F5)2 (5): Compound 4 (368 mg,
1
ꢀ
(1.602 g, 56%). H NMR (C6D6): d=2.55 (s, 1H; C CH), 1.21 ppm (d,
0.668 mmol) was stirred with Me2SiHCl (1.0 g, 5.83 mmol) overnight in
CH2Cl2 (8 mL). After confirming full conversion to the product by NMR
spectroscopy of the reaction mixture, all volatiles were completely re-
moved. The residue was dissolved in toluene (10 mL) and passed through
neutral alumina to eliminate high molecular weight impurities. The fil-
trate was dried and the product was recrystallized by layering a solution
of the product in CH2Cl2 with pentane at 258C overnight. The colorless
crystals of product were separated from the supernatant, from which
more product was recrystallized by layering a CH2Cl2 solution of the
compound with pentane. The combined product was dried in vacuo
(273 mg, 79%). Single crystals suitable for X-ray diffraction were grown
by layering a solution of the product in CH2Cl2 with pentane at 258C.
1H NMR (CD2Cl2): d=5.70 (dd, 1H, 1JHP =464 Hz, 5JHH =2.0 Hz; PH),
3.25 (q, 1H, 1JHB =91 Hz; BH), 1.48 ppm (d, 18H, 3JHP =18.8 Hz; tBu);
11B{1H} NMR: d=À29.2 ppm (s); 13C{1H} NMR (CD2Cl2): d=148.0 (dm,
3
2
18H, JHP =12.3 Hz; tBu); 13C{1H} NMR (C6D6): d=95.5 (d, JCP =5.0 Hz;
1
1
ꢀ
ꢀ
PC C), 84.9 (d, JCP =27.9 Hz; PC C), 33.3 (d, JCP =17.4 Hz; quaternary
tBu), 30.6 ppm (d, 2JCP =14.7 Hz; tBu); 31P{1H} NMR (C6D6): d=
ꢀ
12.5 ppm (s); MS (EI): m/z calcd: 170.1224; found: 170.1222 [HC
CPtBu2]+.
ꢀ
Synthesis of tBu2P(H)C CB
0.29 mmol) in toluene (3 mL) was added to a solution of B
N
A
solution of
1
(50 mg,
(C6F5)3
U
(150 mg, 0.29 mmol) in toluene (2 mL) at À358C. The reaction was
stirred at room temperature for 1 h, and toluene was evaporated off. Pen-
tane (10 mL) was then added, and the mixture was filtered and washed
with pentane to isolate an off-white product. The product was further
dried in vacuo (175 mg, 88%). Single crystals suitable for X-ray diffrac-
tion were grown by slow diffusion of pentane into a solution of the prod-
1
1
uct in CH2Cl2 at 258C. H NMR (CD2Cl2): d=5.71 (d, 1H, JHP =466 Hz;
1JCF =235 Hz; o-C6F5), 138.8 (dm, 1JCF =245 Hz; p-C6F5), 136.9 (dm,
PH), 1.45 ppm (d, 18H, JHP =18.8 Hz; tBu); 11B{1H} NMR (CD2Cl2): d=
3
1JCF =261 Hz; m-C6F5), 120.9 (brs; quaternary C6F5), 64.4 (d, JCP
=
1
À21.4 ppm (s); 13C{1H} NMR (CD2Cl2): d=148.7 (dm, 1JCF =242 Hz; o-
158 Hz; C CP), 34.7 (d, 1JCP =44 Hz; quaternary tBu), 26.7 ppm (d,
C6F5), 139.7 (dm, 1JCF =234 Hz; p-C6F5), 137.3 (dm, 1JCF =240 Hz; m-
ꢀ
2JCP =2.6 Hz; tBu), the C CB carbon was not observed; 19F NMR
C6F5), 120.5 (brs; i-C6F5), 65.8 (d, 1JCP =173 Hz; C CP), 35.3 (d, JCP
=
1
ꢀ
ꢀ
(CD2Cl2): d=À133.2 (dm, 4F, 3JFF =21 Hz; o-C6F5), À162.8 (t, 2F, JFF
=
3
43 Hz; quaternary tBu), 27.0 ppm (d, 2JCP =2.6 Hz; tBu), the acetylenic
carbon bound to boron was not observed; 19F NMR (CD2Cl2): d=À133.1
(d, 6F, 3JFF =23 Hz; o-C6F5), À161.5 (t, 3F, 3JFF =20 Hz; p-C6F5),
À166.6 ppm (m, 6F; m-C6F5); 31P{1H} NMR (CD2Cl2): d=24.5 ppm (s);
20 Hz; p-C6F5), À166.7 ppm (m, 4F; m-C6F5); 31P{1H} NMR (CD2Cl2):
d=24.2 ppm (s); IR (CH2Cl2): n˜ =2125 cmÀ1 (C C); elemental analysis
ꢀ
calcd (%) for C22H20BF10P: C 51.19, H 3.91; found: C 51.35, H 4.02.
ꢀ
MS (EI, CH2Cl2): m/z: 682.1 [tBu2P(H)C CB
(C6F5)3]+; elemental analy-
ꢀ
Synthesis of tBu2P(Me)C CB(H)
(C6F5)2 (6): This compound (43 mg,
sis calcd (%) for C28H19BF15P: C 49.30, H 2.81; found: C 49.36, H 3.02.
84%) was prepared in a fashion analogous to 3. Single crystals suitable
for X-ray diffraction were grown by layering a solution of the product in
ꢀ
Synthesis of tBu2P(Me)C CB
G
1
CH2Cl2 with pentane at 258C. 1H NMR (CD2Cl2): d=3.20 (q, 1H, JHB
=
was added to 2 (163 mL) in toluene (7 mL). The reaction was stirred
overnight. The solvents were completely evaporated off and the white
solid was washed with pentane. The dry product was redissolved in
CH2Cl2 (3 mL) and CH3I (0.5 mL) was then added to the solution.The re-
action was stirred overnight and all volatiles were evaporated off. The
solid was washed with pentane and recrystallized by layering a CH2Cl2
solution of the compound with pentane to give the pure product (96 mg,
58%). Single crystals suitable for X-ray diffraction were grown by layer-
ing a solution of the product in CH2Cl2 with pentane at 258C. 1H NMR
(CD2Cl2): d=1.71 (d, 3H, 3JHP =12.1 Hz; PCH3), 1.39 ppm (d, 18H,
3JHP =16.9 Hz; tBu); 11B{1H} NMR (CD2Cl2): d=À21.5 ppm (s);
13C{1H} NMR (CD2Cl2): d=148.7 (dm, 1JCF =237 Hz; o-C6F5), 139.6 (dm,
2
3
91 Hz; BH), 1.72 (d, 3H, JHP =12.1 Hz; PCH3), 1.42 ppm (d, 18H, JHP
=
16.9 Hz; tBu); 11B{1H} NMR (CD2Cl2): d=À29.2 ppm (s); 13C{1H} NMR
(CD2Cl2): d=148.4 (dm, 1JCF =238 Hz; o-C6F5), 139.1 (dm, 1JCF =239 Hz;
p-C6F5), 137.3 (dm, 1JCF =246 Hz; m-C6F5), 121.7 (brs, quaternary C6F5),
1
1
ꢀ
69.4 (d, JCP =165 Hz; C CP), 35.3 (d, JCP =48 Hz; quaternary tBu), 26.8
(d, 2JCP =1.3 Hz; tBu), 4.7 ppm (d, 1JCP =57 Hz; CH3), the C CB carbon
was not observed; 19F NMR (CD2Cl2): d=À132.9 (d, 4F, 3JFF =20 Hz; o-
C6F5), À162.7 (t, 2F, 3JFF =20 Hz; p-C6F5), À166.4 ppm (m, 4F; m-C6F5);
31P{1H} NMR (CD2Cl2): 31.9 ppm (s); elemental analysis calcd (%) for
C23H22BF10P: C 52.10, H 4.18; found: C 51.74, H 3.97.
ꢀ
ꢀ
Synthesis of [tBu2P(H)C CB
5 (50 mg, 0.097 mmol) in CH2Cl2 (1 mL) was added dropwise to a stirring
(C6F5)
E
G
1JCF =247 Hz; p-C6F5), 137.3 (dm, JCF =228 Hz; m-C6F5), 121.1 (brs; qua-
1
ternary C6F5), 70.5 (d, JCP =145 Hz; C CP), 35.4 (d, JCP =47 Hz; quater-
nary tBu), 26.7 (d, 2JCP =1.5 Hz; tBu), 4.4 ppm (d, 1JCP =57 Hz; PCH3),
solution of [CPh3][B
ACHTUNGTRENNUNG
the intense yellow color of [CPh3][BAHCTNUGTRENNNUG
the C CB carbon was not observed; 19F NMR (CD2Cl2): d=À132.8 (m,
ꢀ
of 5 was used). The reaction mixture was stirred for a further 5 min, fol-
lowed by addition of THF (30 mL, 0.37 mmol) and stirring for another
5 min. The colorless solution was evaporated down to ꢁ0.5 mL. Addition
of pentane (5 mL) precipitated a sticky solid product, which was left to
stir for 3 h. The mother liquor was removed and the sticky solid dried in
vacuo. The product was further recrystallized by layering a CH2Cl2 solu-
tion of the compound with pentane at RT (70 mg, 77%). 1H NMR
4F; o-C6F5), À161.3 (t, 2F, 3JFF =21 Hz; p-C6F5), À166.3 ppm (m, 4F; m-
C6F5); 31P{1H} NMR (CD2Cl2): d=32.8 ppm (s); elemental analysis calcd
(%) for C29H21BF15P: C 50.03, H 3.04; found: C 49.49, H 3.08.
ꢀ
Synthesis of tBu2P(H)C CB(Cl)
1.93 mmol) in toluene (8 mL) was added to a solution of ClB
(733 mg, 1.93 mmol) in toluene (2 mL) at À358C. The reaction was
stirred for 1 h, during which time the solution became yellow. After the
solvent was completely evaporated off, pentane (12 mL) was added and
the mixture was stirred until an off-white solid formed. The supernatant
liquid was decanted and the solid product was washed with pentane.
Drying in vacuo afforded an off-white powder (761 mg, 72%). This prod-
uct was used in the subsequent reactions without further purification.
Single crystals suitable for X-ray diffraction were grown by layering a so-
(CD2Cl2): d=5.83 (d, 1H, 1JHP =475 Hz; PH), 4.37 (m, 4H; O-
3
(CH2CH2)2), 2.30 (m, 4H;
O
(CH2CH2)2), 1.51 ppm (d, 18H, JHP
=
BACHTUNGTRENNUNG(THF)),
À16.6 ppm (s; B
(C6F5)4); 13C{1H} NMR (CD2Cl2): d=150.3–135.5 (over-
ACHTUNGTRENNUNG
lapping broad signals for o-, p-, and m-C6F5), 124.6 (brs; i-C6F5, B-
ACHTNUGTREG(UNNN C6F5)4), 113.2 (brs, i-C6F5, BAHCUTNREGTN(GUNN C6F5)2), 78.1 (s; OCAHTNUGRTEN(NNGU CH2CH2)2), 73.7 (d,
1JCP =143 Hz; C CP), 35.7 (d, 1JCP =39 Hz; quaternary tBu), 27.0 (d,
ꢀ
2JCP =3.0 Hz; tBu), 25.7 ppm (s; O
A
lution of the product in CH2Cl2 with pentane at 258C. 1H NMR
ꢀ
served; 13C
o-C6F5, B(C6F5)2), 140.5 (s; p-C6F5, B
136.9 (s; m-C6F5, B
(C6F5)2), 135.5 (q, 3JCB =3.0 Hz; m-C6F5, B
123.4 ppm (q, 1JCB =51 Hz; i-C6F5, B(C6F5)4); 19F NMR (CD2Cl2): d=
(C6F5)2),
(C6F5)2), À162.4 (m, 4F; m-C6F5, B-
(C6F5)4), À168.0 ppm (m,
E
(CD2Cl2): d=5.80 (d, 1H, 1JHP =469 Hz; PH), 1.51 ppm (d, 18H, JHP
18.8 Hz; tBu); 11B{1H} NMR (CD2Cl2): d=À12.8 ppm (s); 13C{1H} NMR
(CD2Cl2): d=148.3 (dm, 1JCF =243 Hz; o-C6F5), 140.1 (dm, 1JCF =251 Hz;
p-C6F5), 137.6 (dm, 1JCF =248 Hz; m-C6F5), 119.8 (brs; quaternary C6F5),
A
ACHTUNGTREN(NGU C6F5)2), 137.4 (s; p-C6F5, BACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
67.4 (d, 1JCP =155 Hz; C CP), 35.4 (d, 1JCP =42 Hz; quaternary tBu),
ꢀ
À133.5 (m, 8F; o-C6F5, B
A
ACHTUNGTRENNUNG
27.0 ppm (d, 2JCP =2.5 Hz; tBu), the C CB carbon was not observed;
À153.9 (t, 2F, 3JFF =20 Hz; p-C6F5, B
ACHTUNGTRENNUNG
19F NMR (CD2Cl2): d=À133.1 (m, 4F; o-C6F5), À160.5 (t, 2F, JFF
A
ACHTUNGTRENNUNG
20 Hz; p-C6F5), À166.1 ppm (m, 4F; m-C6F5); 31P{1H} NMR (CD2Cl2):
d=25.5 ppm (s); elemental analysis calcd (%) for C22H19BClF10P: C
47.99, H 3.48; found: C 47.87, H 3.80.
8F; m-C6F5, BACTHNGUTERNNUG
(C6F5)4); 31P{1H} NMR (CD2Cl2): 26.8 ppm (s); elemental
analysis calcd (%) for C50H27B2F30OP: C 47.43, H 2.15; found: C 47.83, H
2.58.
Chem. Eur. J. 2011, 17, 6731 – 6743
ꢂ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
6739

D. W. Stephan et al.
ꢀ
ꢀ
Synthesis of tBu2PC CB
[tBuN(H)CH2Ph]
N
5
solution of Mes2PC CBACHTNGUTERNNU(G C6F5)2. After acetonitrile (20 mL) was added, the
(32 mg, 0.06 mmol) and tBuN=CHPh (10 mg, 0.06 mmol) were stirred in
CH2Cl2 (1–2 mL) for 2 h at RT. Colorless crystals formed from the con-
centrate at À358C over 2 d. The supernatant liquid was quickly decanted
and the crystals were washed with cold pentane and dried. More crystal-
line product was obtained from the combined and concentrated washings
at À358C (24 mg, 57%). The crystalline product was suitable for X-ray
diffraction. 1H NMR (C6D6): d=6.82 (m, 3H; Ph), 6.52 (brs, 2H; Ph),
5.10 (brs, 1H; NH), 3.75 (brs, 2H; CH2), 1.41 (brs, 18H; PtBu2),
1.26 ppm (s, 9H; NtBu); 11B{1H} NMR (C6D6): d=À9.6 ppm (brs);
13C{1H} NMR (C6D6): d=148.6 (dm, 1JCF =243 Hz; o-C6F5), 140.8 (dm,
1JCF =243 Hz; p-C6F5), 138.0 (dm, 1JCF =249 Hz; m-C6F5), 135.9 (s; quater-
nary Ph), 129.2 (s; Ph), 126.1 (s; Ph), 119.7 (brs; quaternary C6F5), 65.3
solution was kept at À358C to afford yellowish crystals of the product
(43 mg, 53%). The product crystals were suitable for X-ray diffraction.
1H NMR (CD2Cl2): d=6.77 (d, 4H, 4JHP =3.0 Hz; Ar-H), 2.45 (s, 3H;
CH3, NCMe), 2.29 (s, 12H; o-CH3), 2.22 ppm (s, 6H; p-CH3);
11B{1H} NMR (CD2Cl2): d=À12.6 ppm (brs); 13C{1H} NMR (CD2Cl2):
d=148.2 (dm, 1JCF =243 Hz; o-C6F5), 142.5 (d, 2JCP =15 Hz; o-C6H2),
140.7 (dm, 1JCF =255 Hz; p-C6F5), 138.8 (s; p-C6H2), 137.1 (dm, JCF
=
1
248 Hz; m-C6F5), 130.4 (d, 1JCP =10 Hz; i-C6H2), 130.2 (d, 3JCP =4 Hz; m-
3
ꢀ
C6H2), 115.0 (s, C N), 22.9 (d, JCP =14 Hz; o-CH3, Mes), 21.1 (s; p-CH3,
Mes), 3.5 ppm (s; CH3, NCMe), the quaternary B
A
carbon atoms were not observed. 19F NMR (CD2Cl2): d=À133.9 (m, 4F;
o-C6F5), À157.9 (t, 2F, 3JFF =20 Hz; p-C6F5), À164.5 ppm (m, 4F; m-
C6F5); 31P{1H} NMR (CD2Cl2): d=À53.0 pm (s); elemental analysis calcd
(%) for C34H25BF10NP: C 60.11, H 3.71, N 2.06; found: C 59.43, H 3.74,
N 2.11.
ꢀ
(brs; C CP), 53.7 (s; quaternary NtBu), 53.3 (s; CH2), 33.5 (d, JCP
=
17 Hz; quaternary PtBu2), 30.5 (d, 2JCP =14 Hz; PtBu2), 28.4 ppm (s;
NtBu), the C CB carbon was not observed; 19F NMR (C6D6): d=À128.5
ꢀ
ꢀ
(brs, 2F; o-C6F5), À128.9 (brs, 2F; o-C6F5), À156.9 (brs, 2F; p-C6F5),
À163.9 (brs, 2F; m-C6F5), À164.2 ppm (brs, 2F; m-C6F5); 31P{1H} NMR
(C6D6): d=18.6 ppm (s); elemental analysis calcd (%) for C33H35BF10NP:
C 58.43, H 5.20, N 2.21; found: C 58.05, H 5.60, N 2.30.
Synthesis of (C6F5)2B(H)HC=C[P(H)Mes2]
(12): The procedure described in the synthesis of 11 was followed to gen-
N
ꢀ
erate Mes2PC CB
(C6F5)2 in situ from compound 9 (75 mg, 0.25 mmol),
(C6F5)2 (190 mg, 0.50 mmol), and PtBu3 (50 mg, 0.25 mmol) in a tolu-
ClB
A
ene/hexanes (1:12, 6.5 mL) mixture. The red-orange solution was trans-
ferred to a Schlenk bomb (50 mL) that was subsequently charged with
H2 (ca. 4 atm) through three freeze–pump–thaw cycles. The reaction was
kept under H2 pressure for 2 d, during which time a light yellow precipi-
tate formed. The contents of the bomb was transferred to a vial and the
yellow solid was isolated and washed with hexanes. The product was fur-
ther recrystallized by layering a CH2Cl2 solution of the compound with
pentane at À358C and extensively washed with pentane to yield a white
powder (59 mg, 37%). 1H NMR (C6D5Br, 373 K): d=8.90 (brd, 1H,
ꢀ
Synthesis of Mes2PC CH (9): The procedure for the synthesis of 1 was
ꢀ
followed in general except for the work up. Me3SiC CPMes2 was synthe-
ꢀ
sized by using Me3SiC CH (1.2 g, 12.2 mmol), nBuLi (1.6m hexane solu-
tion, 6.7 mL, 10.7 mmol), and Mes2PCl (3.00 g, 9.84 mmol). After
ꢀ
Mes2PC CH was formed in methanol with potassium carbonate (3.0 g,
22 mmol), the methanol was completely evaporated from the reaction
mixture. The product was extracted with pentane, filtered through Celite,
passed through a plug of neutral alumina, and recrystallized from pen-
tane to yield colorless crystals that were further dried in vacuo (1.293 g,
45%). This crystalline product was suitable for X-ray diffraction.
3JHP =78.1 Hz; =CH), 8.14 (d, 1H, 1JHP =511 Hz; PH, CPH), 7.72 (brd,
ꢀ
1H, 1JHP =457 Hz; PH, =CPH), 6.73 (d, 4H, 4JHP =5.2 Hz; Ar-H,
ꢀ
1H NMR (C6D6): d=6.66 (d, 4H, 4JHP =2.8 Hz; Ar-H), 2.65 (s, 1H; C
ꢀ
CPHMes2), 6.54 (brs, 4H; Ar-H, =CPHMes2), 3.45 (brs, 1H; BH), 2.27
CH), 2.48 (s, 12H; o-CH3), 2.04 ppm (s, 6H; p-CH3); 13C{1H} NMR
ꢀ
(s, 12H; o-CH3, CPHMes2), 2.25 (brs, 12H; o-CH3,=CPHMes2), 2.09
2
(C6D6): d=142.0 (d, JCP =16.1 Hz; 2,6-C6H2), 138.3 (s; 4-C6H2), 130.2 (d,
(s, 6H; p-CH3), 2.05 ppm (s, 6H; p-CH3); 11B{1H} NMR (C6D5Br, 373 K):
3JCP =3.9 Hz; 3,5-C6H2), 129.7 (d, 1JCP =11.6 Hz; PCmes), 96.2 (d, JCP
=
2
d=À16.9 (d, 2JBP =17 Hz;
B
(C6F5)2), À20.3 ppm (brs; BH
ACHTUNGTRENNUNG(C6F5)2);
6.3 Hz; PC C), 83.3 (d, 1JCP =13.1 Hz; PC C), 23.1 (d, 2JCP =14.1 Hz; o-
CH3), 20.7 ppm (s; p-CH3); 31P{1H} (C6D6): d=À54.5 ppm (s); elemental
analysis calcd (%) for C20H23P: C 81.60, H 7.87; found: C 81.57, H 7.82.
ꢀ
ꢀ
13C{1H} NMR (C6D5Br, 273 K): d=147.7 (dm, 1JCF =240 Hz; overlapping
signals of o-C6F5), 145.2, 142.8, 142.3, 142.2, 142.1, 141.9, 140.8, 136.3
(dm, 1JCF =248 Hz; overlapping signals of m-C6F5), 111.8 (brs; ArMes),
21.5 (brs; CH3), 20.7, 20.6, 20.5, 20.4, 20.1, a number of carbon signals
were hidden underneath the solvent peaks or could not be unambiguous-
ly assigned for a spectrum taken at 258C; 19F NMR (C6D5Br, 373 K): d=
ꢀ
Synthesis of [HPtBu3][Mes2PC CB
1.6 mmol) in toluene (3 mL) was added to a solution of B
N
U
1.6 mmol) and PtBu3 (33 mg, 1.6 mmol) in toluene (3 mL) at À358C.
After 3 h of stirring, the solvent was completely evaporated off. Pentane
(6 mL) was then added and the mixture was stirred overnight. A white
solid precipitated. The supernatant liquid was removed, and the product
was further washed with pentane and dried. The product was recrystal-
lized by layering a benzene solution of the compound with heptane at
À127.0 (brs, 4F; o-C6F5, B
N
ACHTUNGTRENNUNG
À159.4 (brs, 2F; p-C6F5, B
ACHTUNGTRENNUNG
À164.2 (brs, 4F; m-C6F5, B (C6F5)2), À166.3 ppm (brs, 4F; m-C6F5, BH-
A
ꢀ
À48.7 ppm (s; CP); elemental analysis calcd (%) for C64H48B2F20P2: C
RT (142 mg, 87%). The crystalline product was suitable for X-ray diffrac-
60.03, H 3.78; found: C 59.99, H 3.66.
tion. 1H NMR (CD2Cl2): d=6.70 (s, 4H; Ar-H), 5.04 (d, 1H, JHP
=
1
ꢀ
ꢀ
Synthesis of [tBu2P(H)C CB
AHCTUNGTREG(NNNU OMe) (14): Predried CH3OH (250 mL) was added to a solution of com-
ACTHGNUTERN(UNGN C6F5)2]AHCNUTRGTE(GNNUN nBuCH2CH)[tBu2PC CBACHTUNGTRENNUNG(C6F5)2]-
428 Hz; HP), 2.26 (s, 12H; o-CH3), 2.19 (s, 6H; p-CH3), 1.61 ppm (d,
27H, 3JHP =15.6 Hz; tBu); 11B{1H} NMR (CD2Cl2): d=À20.9 ppm (s);
pound 13 (55 mg, 0.049 mmol) in CH2Cl2 (8 mL) in a well-dried Schlenk
flask. After stirring at RT for 2d, all volatiles were removed in vacuo.
The remaining mixture was redissolved in CH2Cl2 (5 mL), the solvent
evaporated, and the crude product precipitated by addition of pentane
(12 mL). Recrystallization by layering a toluene solution of the com-
pound with pentane gave a colorless crystalline product (42 mg, 74%).
The product crystals were suitable for X-ray diffraction. 1H NMR
(CD2Cl2): d=5.71 (d, 1H, 1JHP =465 Hz; PH), 3.26 (s, 3H; OCH3), 2.42
(m, 1H; PCH), 1.95 (m, 1H; PCHCH2), 1.82 (m, 2H; BCH2), 1.59 (d,
9H, 3JHP =15.6 Hz; tBu), 1.50 (d, 9H, 3JHP =18.8 Hz; tBu), 1.46 (d, 9H,
3JHP =18.7 Hz; tBu), 1.45 (d, 9H, 3JHP =15.1 Hz; tBu), 1.43 (m, 1H;
PCHCH2), 1.41 (m, 1H; PCHCH2CH2), 1.04 (m, 1H; PCHCH2CH2), 0.82
(m, 1H; PCHCH2CH2CH2), 0.65 (m, 1H; PCHCH2CH2CH2), 0.63 ppm
(m, 3H; PCHCH2CH2CH2CH3); 11B NMR (CD2Cl2): d=À6.9 (s;
13C{1H} NMR (CD2Cl2): 148.6 (dm, JCF =240 Hz; o-C6F5), 142.3 (d, JCP
=
1
2
15 Hz; o-C6H2), 138.8 (dm, 1JCF =246 Hz; p-C6F5), 137.9 (s; p-C6H2),
137.1 (dm, 1JCF =245 Hz; m-C6F5), 132.4 (d, 1JCP =12 Hz; i-C6H2), 129.9
(d, 3JCP =4 Hz; m-C6H2), 38.2 (d, 1JCP =26 Hz; quaternary tBu), 30.5 (s;
tBu), 22.7 (d, 3JCP =14 Hz; o-CH3, Mes), 21.1 ppm (s; p-CH3, Mes), C
ꢀ
ꢀ
CP, C CB and quaternary C6F5 carbon atoms were not observed;
19F NMR (CD2Cl2): d=À132.3 (dm, 6F, 3JFF =23 Hz; o-C6F5), À164.0 (t,
3F, 3JFF =20 Hz; p-C6F5), À167.5 ppm (tm, 6F, 3JFF =20 Hz; o-C6F5);
31P{1H} NMR (CD2Cl2): d=61.4 (s; HPtBu3), À52.9 ppm (s; PMes2); ele-
mental analysis calcd (%) for C50H50BF15P2: C 59.54, H 5.00; found: C
59.27, H 5.02.
ꢀ
Synthesis of Mes2PC CB
A
E
9
(37 mg,
0.13 mmol) and PtBu3 (25 mg, 0.12 mmol) were dissolved in toluene
(1 mL) and precooled to À358C. The phosphine mixture was then added
BOCH3), À18.6 ppm (brs; BCH2CHP); 13C{1H} NMR (CD2Cl2): d=148.4
1
(dm, 1JCF =245 Hz; overlapping signals of o-C6F5), 139.3 (dm, JCF
=
to a precooled solution of ClBACHTUNRGTEN(UNG C6F5)2 (95 mg, 0.25 mmol) in toluene
1
(1 mL) at À358C to give a red solution. After the reaction was stirred for
253 Hz; overlapping signals of p-C6F5), 137.5 (dm, JCF =248 Hz; overlap-
ping signals of m-C6F5), 123.3 (brs; overlapping signals of i-C6F5), 53.0 (s;
OCH3), 39.1 (d, 1JCP =38.3 Hz; quaternary tBu), 37.6 (d, 1JCP =40.1 Hz;
quaternary tBu), 37.3 (d, 1JCP =34.7 Hz; PCH), 35.6 (d, 1JCP =42.5 Hz;
1 h, it was evaporated to ꢁ0.5 mL. Hexanes (6 mL) were added to pre-
cipitate a yellow solid ([HPtBu3]ACTHUNTRGENN[UG Cl2BACHTUTGNRENN(UGN C6F5)2]), and the mixture was kept
at À358C for 2 h. This was filtered through Celite to give a red-orange
6740
www.chemeurj.org
ꢂ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 6731 – 6743

Alkynyl-Linked Phosphonium Borates
FULL PAPER
3
quaternary tBu), 35.5 (d, 1JCP =42.5 Hz; quaternary tBu), 34.7 (d, JCP
=
À165.8 (m, 2F; m-C6F5), À166.5 (m, 2F; m-C6F5), À166.7 ppm (m, 2F;
3.8 Hz; PCHCH2CH2), 33.3 (d, 2JCP =1.9 Hz; PCHCH2), 29.0 (s; tBu),
m-C6F5); 31P{1H} NMR (CD2Cl2): 40.6 (brs), 38.2 ppm (s); IR (thin film
28.4 (s; tBu), 27.1 (d, JCP =1.4 Hz; tBu), 27.1 (d, 2JCP =1.7 Hz; tBu), 23.9
2
ꢀ
from CH2Cl2): n˜ =2126 (C C); elemental analysis calcd (%) for
(brs;
BCH2),
23.2
(s;
PCHCH2CH2CH2),
13.9 ppm
(s;
C54H56B2F20OP2: C 54.75, H 4.76; found: C 54.69, H 4.92.
PCHCH2CH2CH2CH3), the acetylenic carbon atoms were not observed;
19F NMR (CD2Cl2): d=À131.9 (m, 2F; o-C6F5), À132.2 (m, 2F; o-C6F5),
À134.2 (m, 4F; o-C6F5), À160.4 (t, 1F, 3JFF =20 Hz; p-C6F5), À160.9 (t,
1F, 3JFF =20 Hz; p-C6F5), À162.1 (t, 1F, 3JFF =20 Hz; p-C6F5), À162.1 (t,
1F, 3JFF =20 Hz; p-C6F5), À165.1 (m, 4F; m-C6F5), À166.4 ppm (m, 4F;
m-C6F5); 31P{1H} NMR (CD2Cl2): d=39.3 (brs; PCHCH2B), 24.4 ppm (s;
PH); elemental analysis calcd (%) for C51H51B2F20OP2: C 53.57, H 4.50;
found: C 53.83, H 5.00.
ꢀ
Synthesis of {[tBu2PC CB
G
E
(C6F5)3 (18 mg, 0.035 mmol) and PtBu3 (7 mg, 0.035 mmol) dissolved in
toluene (1.0 mL) was added to a solution of 5 (18 mg, 0.035 mmol) in tol-
uene (1.0 mL). The reaction mixture immediately turned orange-yellow
and became cloudy after stirring for 10 min. Hexanes were added and
the reaction was left to stand at À358C for 30 min. The mixture was then
filtered through Celite and washed with cold hexanes. More hexanes
were added to the combined filtrate to a total amount of 18 mL (approxi-
ꢀ
Synthesis of {[tBu2PC CB
(C6F5)2](nBuCH2CH2)}2 (15): A Schlenk bomb
mately 2 mm of the (C6F5)2BC CPtBu2 species). Upon addition of THF
(50 mL) was charged with compound 13 (23 mg, 0.021 mmol) in toluene
(1.5 mL). 1-Hexene (1.5 mL, 12.0 mmol) was added by syringe to the
bomb, which was then tightly closed and heated at 808C for 24 h. The
light yellow solution was poured into a vial and hexanes (8 mL) was
added to the solution. After standing in a freezer at À358C for 3 d, color-
less crystals had precipitated. These were isolated, washed with hexanes
and dried in vacuo to give the white product as a mixture of two diaste-
reomers (7 mg, 28%). The crystalline product was suitable for X-ray dif-
fraction studies. Mixture of two diastereomers: 1H NMR (CD2Cl2): d=
2.59 (m), 2.42 (m), 2.09 (m), 1.81 (m), 1.57 (d, 18H, 3JHP =14.9 Hz; tBu),
(40 mL), the solution immediately turned colorless. The reaction was kept
at 258C without stirring until a colorless crystalline material precipitated
out (typically 2 d). The product was washed with pentane and dried in va-
cuo (8 mg, 39%). Single crystals suitable for X-ray diffraction were ob-
tained from the reaction mixture. 1H NMR (CD2Cl2): d=3.55 (t, 4H,
3JHH =5.93 Hz; CH2OB), 2.22 (m, 4H; PCH2), 1.96 (m, 4H;
3
PCH2CH2CH2), 1.75 (m, 4H; PCH2CH2), 1.38 ppm (d, 36H, JHP
=
16.4 Hz; tBu); 11B{1H} NMR (CD2Cl2): d=À7.3 ppm (s); 13C{1H} NMR
(CD2Cl2): 148.4 (dm, 1JCF =240 Hz; o-C6F5), 139.4 (dm, 1JCF =246 Hz; p-
C6F5), 137.3 (dm, 1JCF =245 Hz; m-C6F5), 69.9 (d, 1JCP =149 Hz; C CP),
ꢀ
3
3
3
65.5 (s; BOCH2), 36.4 (d, 1JCP =44.7 Hz; quaternary tBu), 33.6 (d, JCP
=
1.51 (d, 18H, JHP =15.3 Hz; tBu), 1.46 (d, 18H, JHP =15.4 Hz; tBu), 1.41
3
(m), 1.24 (m), 1.21 (d, 18H, 3JHP =15.0 Hz; tBu), 0.99 (m), 0.88 (t, JHH
=
13.7 Hz; PCH2CH2CH2), 27.0 (s; tBu), 25.1 (d, 2JCP =6.4 Hz; PCH2CH2),
7.2 Hz), 0.73 (t, JHH =7.2 Hz), 0.67 ppm (m); 11B{1H} NMR (CD2Cl2): d=
3
18.2 ppm (d, 1JCP =48.7 Hz; PCH2), the i-C6F5 and C CB carbon atoms
ꢀ
1
À18.1 ppm (br); 13C{1H} NMR (CD2Cl2; partial): d=40.3 (d, JCP
=
3
were not observed; 19F NMR (CD2Cl2): d=À134.0 (dm, 16F, JFF
=
37.6 Hz; quaternary tBu), 39.2 (d, 1JCP =38.2 Hz; quaternary tBu), 38.5
(d, 1JCP =40.0 Hz; quaternary tBu), 37.4 (d, 1JCP =39.1 Hz; quaternary
tBu), 34.7, 34.4, 33.1 (s), 32.8 (d, JCP =9.9 Hz), 31.6 (d, JCP =13.2 Hz), 29.7
(s; tBu), 29.6 (s; tBu), 29.4 (s; tBu), 28.2 (s; tBu), 23.7, 23.5 (s), 22.9 (s),
3
24 Hz; o-C6F5), À161.6 (t, 8F, JFF =20 Hz; p-C6F5), À166.2 ppm (m, 16F;
m-C6F5); 31P{1H} NMR (CD2Cl2): 38.1 ppm (s); elemental analysis calcd
(%) for C52H52B2F20O2P2: C 53.27, H 4.47; found: C 53.36, H 3.95.
ꢀ
Synthesis of {[Mes2PC CB
scribed in the synthesis of 11 was followed to generate Mes2PC CB-
(C6F5)2]
E
ACTHNUTRGNEUNG
14.4 (s; CH3), 14.0 (s; CH3), 13.9 ppm (s; CH3); 13C{19F} NMR (CD2Cl2):
d=148.5 (s; o-C6F5), 148.4 (s; o-C6F5), 148.1 (s; o-C6F5), 139.1 (s; p-C6F5),
137.5 (s; m-C6F5), 137.4 ppm (s; m-C6F5); 19F NMR (CD2Cl2): d=À129.3
(dm, 4F, 3JFF =20 Hz; o-C6F5), À131.2 (dm, 4F, 3JFF =20 Hz; o-C6F5),
À132.3 (m, 4F; o-C6F5), À132.7 (dm, 4F, 3JFF =20 Hz; o-C6F5), À161.7 (t,
2F, 3JFF =20 Hz; p-C6F5), À162.0 (t, 2F, 3JFF =20 Hz; p-C6F5), À162.2 (t,
2F, 3JFF =20 Hz; p-C6F5), À162.5 (t, 2F, 3JFF =20 Hz; p-C6F5), À165.8 (m,
8F; m-C6F5), À166.2 ppm (m, 8F; m-C6F5); 31P{1H} NMR (CD2Cl2): d=
43.0 (m), 41.3 ppm (s); elemental analysis calcd (%) for C56H60B2F20P2: C
56.21, H 5.05; found: C 55.68, H 5.25.
ACHUTNGRENUN(G C6F5)2 in situ from compound 9 (26 mg, 0.088 mmol), ClBAHCTUNGTREN(NUGN C6F5)2 (68 mg,
0.18 mmol), and PtBu3 (18 mg, 0.089 mmol) in a toluene/hexanes (1:12,
6.5 mL) mixture. Phenylacetylene (100 mL, 0.91 mmol) was syringed into
the reaction in one portion. After stirring at RT for 30 min, the solvent
was evaporated off, and pentane was added to precipitate the product.
The yellow product was further recrystallized by layering a CH2Cl2 solu-
tion of the compound with pentane at RT (18 mg, 28%). Single crystals
suitable for X-ray diffraction were grown by layering a solution of the
product in CH2Cl2 with pentane at 258C. 1H NMR (CD2Cl2): d=9.07 (d,
2H, 3JHP =40.3 Hz; CH), 6.83 (m, 18H; Ph, Mes), 2.35 (s, 24H; o-CH3),
2.27 ppm (s, 12H; p-CH3); 11B{1H} NMR (CD2Cl2): d=À19.4 ppm (s);
ꢀ
ꢀ
Synthesis of [tBu2PC CB
ACHTUNGTRENNUNG(CH2)4] (16): Compound 14 (30 mg) was dissolved in CH2Cl2 (10 mL)
ACTHGNUTREN(UNGN C6F5)2]AHCNUTRTEGN(GUNN nBuCH2CH)[tBu2PC CBCAHTNUGTRENUN(NG C6F5)2][O-
and THF (0.5 mL). The resulting mixture was left to stand at 258C with-
out stirring for 1 d. The solvent was completely evaporated off. Following
the addition of a small amount of pentane, the solid product was further
dried in vacuo. Recrystallization by layering a CH2Cl2 solution of the
compound with pentane was performed when further purification was
necessary (26 mg, 81%). Single crystals suitable for X-ray diffraction
were grown by layering a solution of the product in CH2Cl2 with pentane
at 258C. 1H NMR (CD2Cl2): d=3.48 (m, 2H; OCH2), 2.83 (m, 1H;
PCH), 2.20 (m; BCH2), 1.97 (m, 4H; PCHCH2CH2, PCH2), 1.66 (m, 2H;
4
13C{1H} NMR (CD2Cl2; partial): d=144.0 (d, JCP =2.8 Hz; p-C6H2), 143.1
(d, 2JCP =10.3 Hz; o-C6H2), 132.0 (d, 3JCP =11.5 Hz; m-C6H2), 130.3 (d,
J
CP =5.3 Hz; Ph), 128.0 (d, JCP =2.9 Hz; Ph), 127.2 (d, JCP =1.5 Hz; Ph),
120.5 (d, 1JCP =91 Hz; i-C6H2), 23.8 (d, 3JCP =6.2 Hz; o-CH3, Mes),
21.3 ppm (s; p-CH3, Mes); 13C{19F} NMR (CD2Cl2): d=147.7 (s; o-C6F5),
AHCTUNGTRENNUNG
139.0 (s; p-C6F5), 136.9 ppm (s; m-C6F5), a cross-peak for =CHB carbon
was observed in an HSQC experiment at 177.5 ppm; 19F NMR (CD2Cl2):
d=À132.5 (dm, 8F, 3JFF =20 Hz; o-C6F5), À162.3 (t, 4F, 3JFF =20 Hz; p-
C6F5), À166.5 ppm (m, 8F; m-C6F5); 31P{1H} NMR (CD2Cl2): d=
À4.7 ppm (s); elemental analysis calcd (%) for C80H56B2F20P2: C 64.89, H
3.81; found: C 62.85, H 4.08.
3
3
OCH2CH2), 1.58 (d, 9H, JHP =15.5 Hz; tBu), 1.52 (d, 9H, JHP =15.3 Hz;
tBu), 1.48 (d, 9H, 3JHP =16.5 Hz; tBu), 1.41 (d, 9H, 3JHP =16.5 Hz; tBu),
3
1.14 (m, 2H; PCH2CH2), 0.82 (m, 2H; PCHCH2CH2), 0.71 (t, 3H, JHH
=
7.0 Hz; CH3), 0.50 ppm (m; CH2CH3); 11B{1H} NMR (CD2Cl2): d=À7.1
Synthesis of (C6F5)2BC(H)=C[P(H)tBu2]ACTHNUTRGNEUNG(AlCl3) (19): A solution of 5
(s), À18.3 ppm (brs); 13C{1H} NMR (CD2Cl2): d=148.4 (dm, JCF
=
=
1
(75 mg, 0.15 mmol) in toluene (4 mL) was added to a stirring suspension
of AlCl3 (19 mg, 0.14 mmol) in toluene (4 mL). The reaction was stirred
overnight at RT. After passing the reaction mixture through a plug of
Celite, the solvent was evaporated from the filtrate. Recrystallization by
layering a toluene solution of the compound with hexanes gave a white
solid that was further washed with hexanes and dried in vacuo (67 mg,
74%). Single crystals suitable for X-ray diffraction were grown by layer-
ing a solution of the product in CH2Cl2 with hexanes at 258C. 1H NMR
(CD2Cl2, 298 K): d=8.23 (d, 1H, 3JHP =45.9 Hz; =CH), 5.42 (d, 1H,
1JHP =429 Hz; PH), 1.51 ppm (d, 18H, 3JHP =16.5 Hz; tBu2);
11B{1H} NMR (CD2Cl2, 298 K): d=12.6 ppm (brs); 13C{1H} NMR
(CD2Cl2, 298 K; partial): d=186.9 (brs; =CH), 148.4 (dm, 1JCF =245 Hz;
o-C6F5), 141.7 (dm, 1JCF =253 Hz; p-C6F5), 137.8 (dm, 1JCF =250 Hz; m-
236 Hz; o-C6F5), 139.3 (dm, 1JCF =249 Hz; p-C6F5), 137.4 (dm, JCF
1
254 Hz; m-C6F5), 123.5 (brs; quaternary C6F5), 73.3 (dm, 1JCP =144 Hz;
C CP), 71.4 (dm, 1JCP =146 Hz; C CP), 64.2 (s; OCH2), 41.2 (m; PCH),
39.1 (d, 1JCP =38 Hz; quaternary tBu), 38.4 (d, 1JCP =38 Hz; quaternary
tBu), 37.1 (d, 1JCP =44 Hz; quaternary tBu), 36.4 (d, 1JCP =45 Hz; quater-
nary tBu), 34.3 (s; OCH2CH2), 34.2 (d, 2JCP =10 Hz; PCH2CH2), 31.7 (s;
PCHCH2CH2), 29.7 (s; tBu), 29.3 (s; tBu), 27.2 (s; tBu), 26.9 (s; tBu),
24.7 (d, 2JCP =6 Hz; BCH2), 23.6 (s; CH2CH2CH3), 18.5 (d, 1JCP =49 Hz;
PCH2), 13.8 ppm (s; CH3); 19F NMR (CD2Cl2): d=À131.6 (m, 2F; o-
ꢀ
ꢀ
3
3
C6F5), À132.1 (d, 2F, JFF =21 Hz; o-C6F5), À134.2 (d, 4F, JFF =22 Hz; o-
C6F5), À161.6 (t, 2F, 3JFF =21 Hz; p-C6F5), À161.9 (t, 1F, 3JFF =20 Hz; p-
C6F5), À162.1 (t, 1F, 3JFF =21 Hz; p-C6F5), À165.5 (m, 2F; m-C6F5),
Chem. Eur. J. 2011, 17, 6731 – 6743
ꢂ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
6741

D. W. Stephan et al.
1
C6F5), 34.7 (d, JCP =35 Hz; quaternary tBu), 28.5 (s; tBu), the i-C6F5 and
ꢀ
off, and the residue was stirred in hexanes (6 mL) overnight. The white
solid product was isolated, washed with haxanes, and dried in vacuo
(113 mg, 68%). Single crystals suitable for X-ray diffraction were grown
by layering a solution of the product in CH2Cl2 with hexanes at 258C.
C CAl carbon resonances were not observed; 19F NMR (CD2Cl2, 193 K):
d=À130.1 (dm, 4F, 3JFF =20 Hz; o-C6F5), À155.3 (t, 2F, 3JFF =20 Hz; p-
C6F5), À163.9 ppm (m, 4F; m-C6F5); 27Al NMR (CD2Cl2, 298 K): d=
103.8 ppm (s); 31P{1H} NMR (CD2Cl2, 298 K): d=76.9 ppm (brs); ele-
mental analysis calcd (%) for C22H20AlBCl3F10P: C 41.37, H 3.16; found:
C 41.05, H 3.74.
1
3
1H NMR (CD2Cl2, 298 K): d=4.61 (dd, 1H, JHP =433 Hz, JHH =12.7 Hz;
3
3
PH), 3.39 (dd, 1H, JHP =16.5 Hz, JHH =11.7 Hz; CH[BACHTUNGTRNEUNG(C6F5)2]2), 2.44 (t,
1H, 3JHH =12.0 Hz; CHPHtBu2), 1.52 (d, 9H, 3JHP =15.9 Hz; tBu),
1.43 ppm (d, 9H, JHP =15.6 Hz; tBu); 11B{1H} NMR (CD2Cl2, 298 K): d=
3
Synthesis of (C6F5)2BC(H)=C[P(H)tBu2]
0.11 mmol) in toluene (1.0 mL) was added to compound
ACHTUNGTRENNUNG
60.5 (brs), À15.9 ppm (s); 13C{1H} NMR (CD2Cl2, 298 K, partial): d=
5
143.1 (m; o-, p-, m-C6F5), 41.6 (s; CHPHtBu2), 36.2 (d, 1JCP =35 Hz; qua-
0.11 mmol) dissolved in toluene (2.0 mL) at À358C, and the mixture was
stirred at that temperature for 5 min. The reaction was warmed up to RT
and stirred for a further 30 min. The precipitated product was separated
on a filter frit and washed with toluene followed by pentane. The product
was then dried in vacuo (42 mg, 48%). Single crystals suitable for X-ray
diffraction were grown from a solution of the compound in bromoben-
zene at 258C. 1H NMR (C6D5Br): d=7.87 (d, 1H, 3JHP =45.0 Hz; =CH),
4.94 (d, 1H, 1JHP =432 Hz; PH), 1.12 ppm (d, 18H, 3JHP =16.2 Hz; tBu2);
11B NMR (C6D5Br): no signal observed; 13C{1H} NMR (C6D5Br): d=
147.4 (dm, JCF =248 Hz; o-C6F5), 140.8 (dm, JCF =260 Hz; p-C6F5), 136.7
(dm, 1JCF =247 Hz; m-C6F5), 114.2 (brs; i-C6F5), 33.6 (d, 1JCP =33 Hz;
quaternary tBu), 27.3 (s; tBu), the olefinic carbon resonances were not
observed; 19F NMR (C6D5Br): d=À127.7 (dm, 4F, 3JFF =23 Hz; o-C6F5),
À152.5 (brs, 2F; p-C6F5), À162.1 ppm (m, 4F; m-C6F5); 27Al NMR
(C6D5Br): d=81.0 ppm (s); 31P{1H} NMR (C6D5Br): d=84.5 (brs); ele-
mental analysis calcd (%) for C22H20AlBBr3F10P: C 33.75, H 2.57; found:
C 34.10, H 2.68.
1
ternary tBu), 33.9 (d, JCP =35 Hz; quaternary tBu), 28.7 (s; tBu), 27.8 (s;
tBu), 13.3 ppm (brs; CH[BACHTNUGRTENN(UG C6F5)2]2) (the i-C6F5 carbon atoms were not
observed; 19F NMR (CD2Cl2, 193 K): d=À126.9 (dm, 1F, 3JFF =23 Hz; o-
C6F5), À128.9 (m, 1F; o-C6F5), À129.8 (m, 2F; o-C6F5), À130.2 (brs, 1F;
o-C6F5), À132.3 (brs, 1F; o-C6F5), À132.9 (m, 1F; o-C6F5), À133.6 (dm,
1F, 3JFF =23 Hz; o-C6F5), À152.5 (t, 1F, 3JFF =20 Hz; p-C6F5), À152.8 (t,
1F, 3JFF =20 Hz; p-C6F5), À156.9 (t, 1F, 3JFF =20 Hz; p-C6F5), À159.3 (t,
1F, 3JFF =20 Hz; p-C6F5), À161.1 (brs, 1F; m-C6F5), À162.3 (brs, 1F; m-
C6F5), À162.6 (m, 1F; m-C6F5), À163.0 (m, 2F; m-C6F5), À163.2 (m, 1F;
m-C6F5), À164.1 (m, 1F; m-C6F5), À166.4 ppm (m, 1F; m-C6F5);
31P{1H} NMR (CD2Cl2, 298 K): d=55.6 ppm (s); elemental analysis calcd
(%) for C34H21B2F20P: C 47.37, H 2.46; found: C 46.77, H 2.36.
1
1
X-ray crystallography: Crystals were coated in paratone-N oil in the glo-
vebox, 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 employing MoKa
radiation (l=0.71073 ꢃ). Data collection strategies were determined by
using Bruker Apex software and optimized to provide >99.5% complete
data to a 2q value of at least 558. The data were collected at 150(Æ2) K
for all crystals. The frames were integrated with the Bruker SAINT soft-
ware package by using a narrow-frame algorithm. Data were corrected
for absorption effects by using the empirical multiscan method
(SADABS). Nonhydrogen atomic scattering factors were taken from the
literature tabulations. The heavy-atom positions were determined by
using direct methods employing the SHELXTL direct-methods routine.
The remaining nonhydrogen atoms were located from successive differ-
ence Fourier map calculations. The refinements were carried out by using
full-matrix least-squares techniques on F, minimizing the function w-
Synthesis of (C6F5)3BC(H)=C[P(H)tBu2][Zn
(29 mg, 0.056 mmol) and [Zn(C6F5)2]·C7H8 (28 mg, 0.056 mmol) were
ACHTUGNTRENN(UGN C6F5)] (21): Compound 5
AHCTUNGTRENNUNG
stirred together in CH2Cl2 (2 mL) overnight at RT. Evaporation of the
solvent afforded a white solid product (36 mg, 70%). Single crystals suit-
able for X-ray diffraction were grown by layering a solution of the prod-
uct in CH2Cl2 with pentane at 258C. 1H NMR (CD2Cl2): d=8.92 (d, 1H,
3JHP =46 Hz; C=CH), 5.28 (d, 1H, 1JHP =425 Hz; PH), 1.36 ppm (d, 18H,
3JHP =15.7 Hz; tBu); 11B{1H} NMR (CD2Cl2): d=À12.9 ppm (d, JBP
=
3
20 Hz); 13C{1H} NMR (CD2Cl2; partial): d=149.2 (dm, 1JCF =234 Hz; o-
C6F5, [Zn
1JCF =260 Hz; p-C6F5, [Zn
(C6F5)3), 138.1 (dm, 1JCF =246 Hz; m-C6F5, B
254 Hz; m-C6F5, [Zn
(C6F5)]), 33.7 (d, 1JCP =38 Hz, quaternary tBu),
28.0 ppm (s; tBu), the i-C6F5 and olefinic carbon atoms were not ob-
served; 19F NMR (CD2Cl2): d=À117.5 (d, 2F, 3JFF =21 Hz; o-C6F5, [Zn-
A
ACHTNUGTNER(UNGN C6F5)3), 142.2 (dm,
AHCTUNGTRENNUNG
1
E
ACTHUGNRETN(NNUG C6F5)3), 137.5 (dm, JCF =
2
2
N
ACHTNUGNERT(NGNU Fo ) and Fo and Fc
ACHTUNGTRENNUNG
are the observed and calculated structure factor amplitudes, respectively.
In the final cycles of each refinement, all nonhydrogen atoms were as-
signed anisotropic temperature factors in the absence of disorder or in-
A
U
À
sufficient data. In the latter case atoms were treated isotropically. C H
3JFF =20 Hz; p-C6F5, [Zn
(C6F5)3), À160.5 (m, 2F; m-C6F5, [Zn
C6F5, B
(C6F5)3); 31P{1H} (CD2Cl2): d=73.6 ppm (brs); elemental analysis
calcd (%) for C34H20BF20PZn: C 44.60, H 2.20; found: C 44.90, H 2.42.
Synthesis of (C6F5)3BC(H)=C[P(H)tBu2][Al(C6F5)2] (22): In a small vial,
compound (30 mg, 0.058 mmol) was dissolved in bromobenzne
(1.0 mL) and the solution was layered with solution of [Al-
(C6F5)3]·toluene (36 mg, 0.068 mmol) in benzene (2.0 mL). After 4 d
ACHTUNGTRENNUNG
atom positions were calculated and allowed to ride on the carbon to
A
E
À
which they are bound assuming a C H bond length of 0.95 ꢃ. H-atom
ACHTUNGTRENNUNG
temperature factors were fixed at 1.20 times the isotropic temperature
factor of the C atom to which they are bound. 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.
CCDC-768761 (10), 808763 (12), 808764 (11), 808765 (14), 808766 (15),
808767 (16), 808768 (17), 808769 (18), 808770 (2), 808771 (19), 808772
(21), 808773 (20), 808774 (23), 808775 (22), 808776 (3), 808777 (4),
808778 (8), and 808779 (9) contain the supplementary crystallographic
data for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_
request/cif..
AHCTUNGTRENNUNG
5
a
ACHTUNGTRENNUNG
standing at RT without stirring, a microcrystalline solid product had pre-
cipitated. The mother liquor was pipetted off, and the product was
washed with benzene and pentane, followed by drying in vacuo (37 mg,
61%). Single crystals suitable for X-ray diffraction were obtained from
the reaction mixture. 1H NMR (C6D5Br): d=9.43 (brd, 1H, JHP
=
3
1
3
51.2 Hz; =CH), 4.75 (d, 1H, JHP =423 Hz; PH), 0.94 ppm (d, 18H, JHP
=
16.1 Hz; tBu2); 11B NMR (C6D5Br): d=À13.8 ppm (s); 13C{1H} NMR
(C6D5Br): d=27.1 (brs; tBu), all other carbon resonances were not ob-
served due to low solubility of the compound in C6D5Br; more polar sol-
vents were not suitable as they reacted with the compound; 19F NMR
(C6D5Br): d=À121.3 (brs, 4F; o-C6F5), À131.0 (brs, 6F; o-C6F5), À147.8
(brs, 2F; p-C6F5), À156.9 (brs, 3F; p-C6F5), À158.3 (brs, 4F; m-C6F5),
À161.8 ppm (brs, 6F; m-C6F5); 27Al NMR (C6D5Br): no signal observed;
31P{1H} NMR (C6D5Br): no signal observed; elemental analysis calcd (%)
for C44H29AlBF25P: C 47.98, H 2.65; found: C 46.28, H 3.01.
Acknowledgements
Professor Stephan is grateful for the financial support of NSERC of
Canada and the award of a Canada Research Chair and a Killam Re-
search Fellowship. XZ is grateful for the award of an NSERC-CGS schol-
arship.
ꢀ
Synthesis of [(C6F5)2B]2HC CH[P(H)tBu2] (23): Compound 5 (100 mg,
0.19 mmol) and HB
N
(5 mL) at 258C overnight. The solvent was then completely evaporated
6742
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ꢂ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 6731 – 6743

Alkynyl-Linked Phosphonium Borates
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Received: January 19, 2011
Published online: May 5, 2011
Chem. Eur. J. 2011, 17, 6731 – 6743
ꢂ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
6743