Reactions of modified intermolecular frustrated P/B lewis pairs with dihydrogen, ethene, and carbon dioxide

Article abstract of DOI:10.1021/om201076f

In this contribution, we discuss the reactivity of different phosphanes (XPhos (1a), ^tBuXPhos (1b), and Mes₂PEt (1c)) and tris(pentafluorophenyl)borane (and in one case, EtB(C₆F ₅)₂) against small mol

Full text of DOI:10.1021/om201076f

Article
pubs.acs.org/Organometallics
Reactions of Modified Intermolecular Frustrated P/B Lewis Pairs with
Dihydrogen, Ethene, and Carbon Dioxide‡
Marcel Harhausen, Roland Frohlich,† Gerald Kehr, and Gerhard Erker*
̈
Organisch-Chemisches Institut, Universitat Munster, Corrensstrasse 40, 48149 Munster, Germany
̈
̈
̈
S
* Supporting Information
ABSTRACT: In this contribution, we discuss the reactivity of different phosphanes (XPhos (1a), tBuXPhos (1b), and Mes2PEt
(1c)) and tris(pentafluorophenyl)borane (and in one case, EtB(C6F5)2) against small molecules. 1a/B(C6F5)3, 1b/B(C6F5)3, and
1c/B(C6F5)3 split dihydrogen heterolytically to yield the phosphonium borate salts 2a, 2b, and 2c, respectively. Control
experiments with D2 gave the respective deuterated phosphonium borates 2a-D2, 2b-D2, and 2c-D2. The FLP systems 1b/
B(C6F5)3 and 1c/B(C6F5)3 underwent 1,2-addition reactions with ethene, resulting in the generation of the ethylene-bridged
phosphonium borates 3b and 3c. As well, the Lewis pair EtB(C6F5)2 and Mes2PEt reacted with ethene to yield the corresponding
1,2-addition product 3d. At low temperature, the FLP systems 1a/B(C6F5)3 and 1c/B(C6F5)3 coordinated carbon dioxide (4a,
4c). The new compounds 2a, 2b, 3b, 3c, 3d, 4a, and 4c were characterized by X-ray crystal structure analyses.
radicals. Inter- as well as intramolecular FLPs were shown to
take up carbon dioxide reversibly.14
INTRODUCTION
■
The synthesis of tris(pentafluorophenyl)borane was described
by Professor F. G. A. Stone and his co-workers in 1963.1 This
unique boron Lewis acid was used extensively as an activator
component in homogeneous Ziegler−Natta olefin polymer-
ization catalysis.2 It was also employed as a very potent Lewis
acid catalyst in organic synthesis3 and it recently opened useful
new variants of the 1,1-carboboration reaction.4 In recent years,
B(C6F5)3 and some of its derivatives have seen extensive use as
a Lewis acid component in frustrated Lewis pair chemistry.5
The strongly Lewis acidic −C6F5 substituted boranes are very
well suited to generate pairs of Lewis acids and bases in
solution that, due to their steric bulk, do not annihilate each
other by the otherwise usually observed strong adduct
formation. The coexistence of active Lewis acid and base
components in solution allows for a unique array of cooperative
reactions with a variety of added substrates to take place.6
Frustrated Lewis pairs (FLPs) thus undergo remarkable
reactions with a variety of small molecules. Many FLP systems
can cleave dihydrogen heterolytically;7 some examples have
served as potent nonmetallic catalysts for the hydrogenation of
a variety of olefinic or acetylenic substrates under rather mild
reaction conditions.8 Many FLP examples were shown to react
with unsaturated organic substrates, including various carbonyl
compounds;9 they react with alkenes10 and alkynes4,11
(including conjugated variants). FLP addition reactions to
N2O12 and even to NO13 have been reported, the latter leading
to the new class of the persistent P/B FLP-NO nitroxide
Most of these remarkable reactions were carried out by
phosphane/borane FLPs,6 although an increasing number of
FLPs has become known that utilize amine Lewis bases15 and
even carbon-based Lewis base components.16 The vast majority
of the presently known FLPs uses boron Lewis acid
components that bear strongly electron-withdrawing −C6F5
substituents. Probably the largest amount of reports on FLP
reactions is on the P/B systems. Among them, variants of the
system I are the most utilized intramolecular systems.7 The
phosphane/borane combination II and some of its variants are
probably the most frequently employed reactive intermolecular
FLPs to date (see Chart 1).7 In this account, we will report on a
Chart 1
trio of typical FLP reactions of a series of new P/B FLPs,
namely, the heterolytic cleavage of dihydrogen and the addition
reactions to ethene and to carbon dioxide. These make use of
simple commercially available or easily synthesized phosphanes.
Special Issue: F. Gordon A. Stone Commemorative Issue
Received: November 3, 2011
Published: January 4, 2012
© 2012 American Chemical Society
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They were combined with the B(C6F5)3 Lewis acid or readily
available derivatives thereof. Our study shows that the scope of
the structural features and the chemical composition of
frustrated Lewis pairs can easily be substantially expanded
and utilized for carrying out a variety of typical frustrated Lewis
pair reactions that readily take place under mild reaction
conditions.
isotopomer 2a-D2 was isolated in 68% yield. It features a PD
doublet in the 2H NMR spectrum at δ 5.48 (1JPD ∼ 71 Hz) and
a broad BD resonance at δ 3.63. The 31P NMR spectrum
showed the phosphonium PD signal as a 1:1:1 triplet at δ 14.1
with a ca. 14% residual PH resonance at δ 15.1 (for further
details see the Supporting Information).
Single crystals of the phosphonium/hydridoborate salt 2a
that were suited for the X-ray crystal structure analysis were
obtained from a solution of 2a in dichloromethane covered
with heptane at −30 °C. In the crystal, the product 2a features
independent phosphonium cations and hydroborate anions.
The boron atom is tetracoordinated (sum of the C−B−C
angles at boron: 338.0°) and shows a hydride attached to it.
The phosphorus atom is also tetracoordinated (sum of the C−
P−C bond angles at phosphorus: 335.6°) and it has the proton
attached to it. The bulky triisopropylphenyl substituent at the
o-position of the P-bonded phenyl group is rotated normal to
the phenyl plane and shields the P−H vector in this orientation
(see Figure 1).
RESULTS AND DISCUSSION
■
For this study, we used three phosphanes, namely, the
commercially available specifically substituted systems XPhos
17
(1a)17 and BuXPhos (1b) and ethyldimesitylphosphane
t
(Mes2PEt) (1c) (see Chart 2). The former pair of
Chart 2
aryldialkylphosphanes bear very bulky o-substituted aryl groups.
They have previously found extensive use in Pd-catalyzed
organic transformations where they had been introduced as
especially useful ligand systems to control C−N bond-forming
reactions.17
We prepared compound 1c from ethyldichlorophosphane by
reaction with 2 mol equiv of mesityllithium. Phosphane 1c was
obtained in 78% yield. It shows a 31P NMR resonance at δ
−18.1 in (CD2Cl2) (for details, see the Supporting
Information).
FLP Activation of Dihydrogen. The three phosphanes
1a−1c were each combined with B(C6F5)3 in an equimolar
ratio to give the respective frustrated Lewis pairs. These were
then subsequently reacted with dihydrogen. As a typical
example, we dissolved the 1a/B(C6F5)3 Lewis pair in pentane
and exposed the solution to a 2 bar hydrogen atmosphere at
room temperature. After ca. 1 h, an oily precipitate began to
appear. After 12 h stirring of the reaction mixture in pentane
under hydrogen atmosphere, we collected the product 2a as a
white precipitate in 77% yield (see Scheme 1).
Figure 1. Molecular structure of the [XPhosH+][HB(C6F5)3−] salt 2a.
t
The reaction of the BuXPhos (1b)/B(C6F5)3 FLP with
hydrogen was carried out analogously. It gave the [tBuXPhos-
H+][HB(C6F5)3−] salt in 65% yield. It was characterized by
spectroscopy [NMR: δ31P 31.9 (1JPH ∼ 455 Hz); δ1H 5.58
(PH); δ11B −25.5 (d, 1JBH ∼ 93 Hz)]. The heterolytic splitting
of dihydrogen was confirmed by carrying out the reaction of the
1b/B(C6F5)3 FLP with D2, which gave the isotopomer
[tBuXPhosD+][DB(C6F5)3−] (2b-D2) (for its characterization,
see the Supporting Information). Compound 2b was also
characterized by an X-ray crystal structure analysis. It exhibits
very similar structural features as the related [XPhosH+][HB-
(C6F5)3−] salt (2a). A view of the molecular structure of the salt
[tBuXPhosH+][HB(C6F5)3−] (2b) is depicted in the Support-
ing Information, where also detailed structural parameters are
listed.
Scheme 1
Ethyldimesitylphosphane (1c) gives a yellow solution when
dissolved together with B(C6F5)3 in pentane. This solution
reacts cleanly with H2 (2 bar) at room temperature. After 12 h
of reaction time, a colorless oil of the salt [Mes2EtPH+][HB-
(C6F5)3−] (2c) was isolated in 80% yield (see Scheme 2). It
shows the typical NMR features of the tris(pentafluorophenyl)-
hydridoborate anion (see above). The cation of 2c is
The salt 2a shows the typical spectroscopic features of the
hydroborate anion [NMR: δ 11B −25.4 (1JBH ∼ 93 Hz); δ1H
1
3.61 (broad 1:1:1:1 q, JBH ∼ 93 Hz, BH); δ19F −133.9 (o),
−164.8 (p), −167.7 (m) (C6F5)] and of a phosphonium cation
[NMR: δ31P 15.1 (1JPH ∼ 466 Hz); δ1H 5.52 (PH)]. The
reaction was also carried out with D2. The corresponding
1
characterized by typical H/31P NMR resonances at δ 7.53
1
(1H) and δ −7.5 (1JPH ∼ 473 Hz) (31P). It shows the H/13C
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Scheme 2
NMR data of the P-bonded ethyl group [δ 2.87 (2H), 1.36
(3H)/δ 18.5 (1JPC = 45.6 Hz), 9.1 (2JPC = 4.1 Hz)] and the
signals of the pair of mesityl substituents.
FLP Addition Reaction to Ethene. The ethyldimesityl-
phosphane/tris(pentafluorophenyl)borane frustrated Lewis pair
reacts readily with ethene. Stirring of a pentane solution of the
FLP in an ethene atmosphere (2 bar) for a prolonged period of
time (48 h) gave the 1,2-P/B-addition product 3c that was
isolated in >50% yield after crystallization (see Scheme 3).
Figure 2. View of the molecular structure of the zwitterionic ethene P/
B addition product 3c.
Scheme 3
The zwitterion 3c was characterized by X-ray diffraction. The
crystal structure analysis confirmed that 1,2-addition of the
Mes2PEt and B(C6F5)3 components to ethene had occurred.
The central B1−C4−C3−P1 unit (dihedral angle: −162.0(2)°)
adopts a slightly distorted antiperiplanar alkane-like confirma-
tion. On the boron side, the C41−C46 C6F5 ring stands in
continuation of this “zig-zag”-shaped chain (C4−B1 1.662(4)
Å, B1−C41 1.659(4) Å; angle C4−B1−C41 110.4(2)°;
dihedral angle C41−B1−C4−C3 178.0(2)°) and so does the
C21−C29 mesityl substituent at the distal phosphorus side
(C3−C4 1.549(4) Å, C3−P1 1.822(3) Å, P1−C21 1.820(3) Å;
angle C3−P1−C21 117.1(1)°; dihedral angle C4−C3−P1−
C21 175.9(2)°). The ethyl substituent at phosphorus is
oriented in a gauche arrangement relative to the central
antiperiplanar chain (P1−C2 1.822(3) Å; dihedral angles C4−
C3−P1−C2 −67.1(2)°, C3−P1−C2−C1 −68.9(2)°) (see
Figure 2).
Figure 3. Molecular structure of compound 3d.
arrangement of the bulky heteroatom-based substituents along
the core −CH2−CH2− moiety (dihedral angle P1−C1−C2−
B1 −155.8(2)°; bond lengths P1−C1 1.818(3) Å, C1−C2
1.533(4) Å, C2−B1 1.649(4) Å; bond angles P−C1−C2
110.8(2)°, C1−C2−B1 110.6(2)°), to which a boron-bonded
C6F5 group and a phosphorus-bonded mesityl group are also
antiperiplanarly connected (dihedral angles C41−B1−C2−C1
−176.6(2)°, C11−P1−C1−C2 −179.2(2)°). Both the ethyl
groups at boron and phosphorus are arranged in gauche
positions relative to the central unit (dihedral angles C1−C2−
B1−C5 −58.1(3)°, C2−C1−P1−C3 −66.1(2)°), and they are
oriented syn to each other at the framework.
The zwitterionic compound 3c shows typical borate type 11
B
(δ −13.1) and 19F [δ −133.1 (o), −162.8 (p), −166.3 (m-
C6F5); Δδ19Fp,m = 3.5] NMR signals and a phosphonium type
31P NMR signal at δ 36.1. The newly introduced bridging
ethylene unit shows NMR resonances at δ 2.51 (CH2P), 1.30
(CH2B) (1H), and δ 25.9 (1JPH = 38.0 Hz) and δ 15.5 (broad)
(13C), respectively.
Compound 3d shows similar NMR features as 3c (see
above) [δ −10.4 (11B), δ 35.5 (31P)] only that it exhibits the
additional signals of the ethyl substituent at boron [1H NMR: δ
0.80 (CH2), 0.44 (CH3)].
We eventually also reacted the tBuXPhos/B(C6F5)3
frustrated Lewis pair with ethene. Under the usual reaction
conditions (r.t., pentane), we obtained the 1,2-addition product
3b, which we isolated in 80% yield as a white solid (see Scheme
4). The X-ray crystal structure analysis showed an antiperi-
planar orientation of the bulky phosphonium and borate groups
at the central bridging ethylene unit (dihedral angle P1−C1−
C2−B1 −168.6(2)°; P1−C1 1.841(3) Å, C2−B1 1.669(4) Å)
(see Figure 4). The bulky o-triisopropylphenyl substituent at
the phosphorus-bonded aryl substituent is found in a
conformational orientation where it is π-facing the bridging
ethylene unit.
The analogous reaction was also carried out with the
frustrated Lewis pair derived from ethyldimesitylphosphane
(1c) and the slightly modified EtB(C6F5)2 Lewis acid. The
latter is readily available by ethene hydroboration with the
HB(C6F5)2 reagent.18 The reaction of this modified FLP (in
situ generation) with ethene was carried out under our typical
reaction conditions (r.t., pentane) and gave the zwitterion 3d,
isolated in ca. 40% yield (see Scheme 3).
The X-ray crystal structure analysis of compound 3d shows
an ethylene-bridged phosphonium/borate zwitterion (see
Figure 3). The central unit shows a distorted antiperiplanar
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Scheme 4
Scheme 5
NMR spectra were measured at 263 K to avoid decomposition.
Compound 4a shows an IR carbonyl stretching band at ν
(C
O) = 1698 cm−1.
The corresponding IR feature of the CO2 addition product
̃
4c derived from the 1c/B(C6F5)3 FLP occurs at ν
̃
(CO) =
1644 cm−1. Compound 4c shows a characteristic 13C NMR
carbonyl carbon signal at δ 162.5 (1JPC = 118.8 Hz) and
heteroatom resonances at δ31P 16.3, δ11B −2.4, and δ19F
−134.6 (o), −160.2 (p), and −165.7 (m), respectively. The 13
C
NMR signals of the single ethyl substituent at phosphorus
occur at δ 22.6 (1JPC = 42.1 Hz) and δ 8.2 (2JPC = 5.1 Hz),
respectively (all NMR spectra of compound 4c were measured
at 253 K).
Compound 4c was also characterized by an X-ray crystal
structure analysis (single crystals were obtained from a solution
of 4c in dichloromethane covered with heptane at −30 °C).
The structure (see Figure 6) features the newly formed bond of
phosphorus to the CO2 carbonyl carbon atom (P1−C1
1.894(3) Å, C1−O1 1.200(3) Å, C1−O2 1.304(3) Å; angle
P1−C1−O1 121.5(2)°) and the newly formed boron−oxygen
bond (B1−O2 1.554(3) Å; angle C1−O2−B1 120.5(2)°). The
ethyl substituent at phosphorus is antioriented to the carbonyl
oxygen in 4c (dihedral angle C2−P1−C1−O1 164.7(2)°).
Figure 4. View of the zwitterionic FLP addition product 3b.
In compound 3b, the [P]−CH2−CH2−[B] signals occur at δ
49.8 (31P), δ 21.0 (1JPC = 27.9 Hz), 18.4 (broad) (13C), and δ
−14.1 (11B), respectively.
FLP Reactions with Carbon Dioxide. We eventually
reacted the FLPs XPhos(1a)/B(C6F5)3 and Mes2EtP(1c)/
B(C6F5)3, respectively, with carbon dioxide. The reaction of the
1a/B(C6F5)3 pair with CO2 was carried out in pentane solution
that was covered with an atmosphere of carbon dioxide (2 bar,
r.t.). The reaction was quick at room temperature, where a
white precipitate started to appear after 20 min reaction time.
The mixture was then cooled to −20 °C and stirred for another
two hours. The solid CO2 addition product 4a was isolated in
80% yield (see Scheme 5).
CONCLUSIONS
■
Our study indicates that the scope of the phosphorus Lewis
base component of frustrated Lewis pairs can substantially be
varied without losing the typical character of FLP chemistry
with small molecules. The phosphanes employed here that are
bearing combinations of bulky aryl and alkyl substituents all
behaved as suitable Lewis base components in the combination
with the Lewis acid B(C6F5)3 (and in one case, with
EtB(C6F5)2). All the FLPs thus formed were able to activate
dihydrogen by heterolytic cleavage of the strong H−H bond at
ambient conditions. They reacted readily with ethene and also
with carbon dioxide to give the corresponding zwitterionic 1,2-
addition products in high yield. This shows us that the scope of
FLP components can probably be varied to quite some extent,
including many commercially available bulky phosphanes, such
Single crystals of the CO2 adduct 4a suited for the X-ray
crystal structure analysis were obtained from a solution of 4a in
dichloromethane covered with heptane at −30 °C. The solid-
state structure shows that the phosphorus atom of the FLP
component 1a has added to the carbonyl carbon atom (P1−C1
1.866(3) Å; angles P1−C1−O1 116.3(2)°, P1−C1−O2
115.0(2)°, O1−C1−O2 128.6(3)°). The O1−C1 bond of the
carbonyl groups is still short at 1.212(3) Å, whereas the
adjacent C1−O2 linkage has become quite elongated by the
addition reaction (C1−O2 1.296(3) Å). The oxygen atom O2
is found bonded to boron (O2−B1 1.554(4) Å; angle C1−
O2−B1 118.5(2)°). The bulky o-triisopropylphenyl substituent
in 4a is oriented facing a P-cyclohexyl group (see Figure 5).
t
as XPhos or BuXPhos, that were actually developed for other
The 13C NMR spectrum of 4a shows the carbonyl resonance
(catalytic) purposes than their utilization in FLP chemistry.
This indicates that FLP chemistry can probably be substantially
expanded with regard to utilization of readily available
components, especially Lewis base components.
1
at δ 162.5 with a coupling constant to phosphorus of JPC
=
116.0 Hz. The corresponding 31P NMR signal occurs at δ 26.8.
Compound 4a shows a 11B NMR resonance at δ −2.7. The
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Figure 5. Projection of the molecular structure of the FLP-CO2 adduct 4a.
(BrukerAXS, 2000). Graphics show the thermal ellipsoids with 50%
probability; R values are given for the observed reflections, wR2 values
for all reflections.
17
Materials. XPhos17 and BuXPhos were ordered from Sigma-
Aldrich and used without further purification. Ethyldichlorophosphane
was ordered from Acros Organics and used without any purification.
Bis(pentafluorophenyl)borane18 and tris(pentafluorophenyl)borane1
were prepared according to modified literature procedures.
t
Preparation of Compound 1c. In a 250 mL Schlenk flask,
bromomesitylene (11.94 g, 60 mmol, 9.2 mL, 2 equiv) was dissolved in
tetrahydrofuran (100 mL). The solution was cooled to −78 °C, and
within 30 min, n-butyl lithium (1.6 M, 41 mL, 65.0 mmol, 2.1 equiv)
was added with a syringe. The solution was stirred for 1 h at −78 °C.
Afterward, ethyldichlorophosphane (3.93 g, 30 mmol, 3.11 mL, 1
equiv) dissolved in tetrahydrofuran (20 mL) was added. The reaction
mixture was allowed to warm to room temperature and was then
stirred for 4 h. The solvent was removed in vacuo, and the residue was
dissolved in dichloromethane (100 mL). After filtration, the solvent
was removed in vacuo. The residue was washed with pentane. After
filtration and evaporation of the solvent, the product was obtained in
78% (6.98 g, 23.4 mmol) yield. Anal. Calcd for C20H27P (298.40 g/
1
mol): C, 80.50; H, 9.12. Found: C, 80.38; H, 9.02. mp: 119.1 °C. H
4
NMR (500 MHz, CD2Cl2, 298 K): δ = 6.78 (dm, JPHP = 2.6 Hz, 4H,
Figure 6. Molecular structure of 4c.
3
2
m-Mes), 2.48 (qd, JHH = 7.5 Hz, JPH = 2.4 Hz, 2H, EtCH ), 2.27 (s,
2
3
3
12H, o-Me), 2.22 (s, 6H, p-Me), 0.95 (dt, JPH = 18.6 Hz, JHH = 7.5
Hz, 3H, PEtCH ). 13C{1H} NMR (126 MHz, CD2Cl2, 298 K): δ =
EXPERIMENTAL SECTION
3
■
142.3 (d, 2JPC= 13.3 Hz, o-Mes), 137.7 (p-Mes), 133.7 (d, JPC = 22.8
1
General Information. All reactions were carried out under an
argon atmosphere with Schlenk-type glassware or in a glovebox.
Solvents (including deuterated solvents used for NMR spectroscopy)
were dried and distilled under argon prior to use. The following
instruments were used for physical characterization of the compounds.
Elemental analyses: Foss-Heraeus CHNO-Rapid. NMR: Bruker AC
200 P (1H, 200 MHz), Varian 500 MHz INOVA (1H, 500 MHz; 13C,
126 MHz), Varian UNITY plus NMR spectrometer (1H, 600 MHz;
13C, 151 MHz). Assignments of the resonances are supported by 2D
experiments. Melting points/decomposition temperature: DSC 2010
(TA-Instruments) apparatus, determined by the baseline method. IR:
Varian 3100 FT-IR (ExcaliburSeries) spectrometer. X-ray diffraction:
data sets were collected with a Nonius KappaCCD diffractometer.
Programs used: data collection, COLLECT (Nonius B.V., 1998); data
reduction, Denzo-SMN (Otwinowski, Z.; Minor,W. Methods Enzymol.
1997, 276, 307−326); absorption correction, Denzo (Otwinowski, Z.;
Borek, D.; Majewski, W.; Minor, W. Acta Crystallogr. 2003, A59, 228−
234); structure solution, SHELXS-97 (Sheldrick, G. M. Acta
Crystallogr. 1990, A46, 467−473); structure refinement, SHELXL-97
(Sheldrick, G. M. Universitat Gottingen, 1997); graphics, XP
Hz, i-Mes), 130.1 (d, 3JPC = 2.8 Hz, m-Mes), 23.2 (d, 3JPC = 13.5 Hz, o-
Me), 21.0 (d, 1JPC = 14.3 Hz, PEtCH ), 20.9 (p-Me), 11.5 (d, JPC = 21.0
2
2
Hz, EtCH ). 31P{1H} NMR (202 MHz, CD2Cl2, 298 K): δ = −18.1
P
3
(ν1/2 ≈ 2 Hz).
Preparation of Compound 2a. In a 10 mL Schlenk flask, XPhos
(50.0 mg, 105 μmol, 1 equiv) and tris(pentafluorophenyl)borane (53.7
mg, 105 μmol, 1 equiv) were dissolved in pentane (3 mL). The
solution was stirred for 10 min. The Schlenk flask was then evacuated,
and dihydrogen gas (2 bar) was added. After 1 h, an oily residue was
obtained. The solution was stirred for 12 h at room temperature, and a
white solid precipitated. The solution was removed and the residue
dried in vacuo. The product was obtained as a white solid in 77% (80.0
mg, 81.1 μmol) yield. Crystals suitable for X-ray crystal structure
analysis were obtained from a solution of 2a in dichloromethane
covered with heptane at −30 °C. Anal. Calcd for C51H51BF15P (M =
990.71 g/mol): C, 61.83; H, 5.19. Found: C, 61.22; H, 5.01. mp: 136.4
°C. 1H NMR (500 MHz, CD2Cl2, 298 K): δ = 7.87 (m, 1H, 4-H), 7.69
(m, 1H, 3-H), 7.68 (m, 1H, 2-H), 7.59 (m, 1H, 5-H), 7.18 (s, 2H, m-
tipp), 5.52 (dt, 1JPH = 465.1 Hz, 3JHH = 5.6 Hz, 1H, PH), 3.61 (1:1:1:1
q {partial relaxed}, 1JBH ∼ 93 Hz, 1H, BH), 2.98 (sept, 3JHH = 6.8 Hz,
̈
̈
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1H, p-iPrCH), 2.44, 1.98/1.40, 1.90/1.35, 1.86/1.28, 1.77/1.21, 1.75/
3
3JHH = 6.9 Hz, 1H, p-iPrCH), 2.26 (sept, JHH = 6.8 Hz, 2H, o-iPrCH),
3
1.32 (each br, each 2H, Cy), 2.19 (sept, JHH = 6.8 Hz, 2H, o-iPrCH),
3
3
1.44 (d, JPH = 17.4 Hz, 18H, tBu), 1.30 (d, JHH = 6.9 Hz, 6H,
3
1.30 (d, 3JHH = 6.8 Hz, 6H, p-iPrCH ), 1.26 ( JHH = 6.8 Hz), 1.01 (3JHH
p-iPrCH ), 1.23, 1.00 (each d, each JHH = 6.8 Hz, each 6H, o-iPrCH ).
13C{1H} NMR (126 MHz, CD2Cl2, 298 K): δ = 152.0 (p-tipp), 148.6
(dm, 1JFC ∼ 235 Hz, o-C6F5), 147.5 (d, 2JPC = 5.1 Hz, C-6), 147.0 (o-
3
3
3
3
= 6.8 Hz) (each d, each 6H, o-iPrCH ). 13C{1H} NMR (126 MHz,
3
1
CD2Cl2, 298 K): δ = 152.2 (p-tipp), 148.8 (dm, JFC ∼ 238 Hz, o-
C6F5), 146.9 (d, 2JPC = 7.0 Hz, C-6), 146.7 (o-tipp), 139.1 (dm, 1JFC
238 Hz, p-C6F5), 136.4 (dm, 1JFC ∼ 245 Hz, m-C6F5), 135.3 (d, 4JPC
∼
1
1
tipp), 138.0 (dm, JFC ∼ 242 Hz, p-C6F5), 136.9 (dm, JFC ∼ 245 Hz,
m-C6F5), 135.3 (d, 3JPC = 9.1 Hz, C-5), 135.1 (d, JPC = 3.0 Hz, C-4),
4
=
3
2
133.4 (d, 2JPC = 9.9 Hz, C-2), 131.1 (d, 3JPC = 4.2 Hz, i-tipp), 129.0 (d,
2.7 Hz, C-4), 134.2 (d, JPC = 9.0 Hz, C-5), 132.9 (d, JPC = 10.5 Hz,
3
3
3JPC = 11.8 Hz, C-3), 125.7 (i-C6F5), 122.3 (m-tipp), 114.8 (d, JPC
=
1
C-2), 131.1 (d, JPC = 5.4 Hz, i-tipp), 129.4 (d, JPC = 11.9 Hz, C-3),
122.3 (m-tipp), 113.5 (d, JPC = 80.5 Hz, C-1), 34.8 (p-iPrCH), 31.29
1
71.2 Hz, C-1), 35.8 (d, JPC = 33.1 Hz, tBu), 34.7 (p-iPrCH), 31.5
1
(o-iPrCH), 31.25 (d, JPC = 40.6 Hz), 28.6 (d, JPC = 3.8 Hz), 27.5 (d,
1
2
(o-iPrCH), 28.6 (d, JPC = 1.2 Hz, tBu), 26.8, 22.3 (o-iPrCH ), 24.0
2
3
2JPC = 3.1 Hz), 26.4 (d, 3JPC = 13.7 Hz), 26.2 (d, 3JPC = 13.8 Hz), 25.1
(p-iPrCH ). 31P{1H} NMR (202 MHz, CD2Cl2, 298 K): δ = 31.9 (ν1/2
3
(d, 4JPC = 1.6 Hz) (Cy), 26.3, 22.5 (o-iPrCH ), 24.0 (p- Pr ). 31P{1H}
NMR (202 MHz, CD2Cl2, 298 K): δ = 15.1 (ν1/2 ≈ 2 Hz). 31P NMR
(202 MHz, CD2Cl2, 298 K): δ = 15.1 (br d, 1JPH ∼ 466 Hz). 19F NMR
(470 MHz, CD2Cl2, 298 K): δ = −133.9 (m, 2F, o-C6F5), −164.8 (t,
3JFF = 20.4 Hz, 1F, p-C6F5), −167.7 (m, 2F, m-C6F5), [Δδ19Fp,m = 2.9].
11B{1H} NMR (160 MHz, CD2Cl2, 298 K): δ = −25.4 (ν1/2 ∼ 40 Hz).
i
CH3
3
≈ 2 Hz). 31P NMR (202 MHz, CD2Cl2, 298 K): δ = 31.9 (dm, 1JPH
∼
455 Hz). 19F NMR (470 MHz, CD2Cl2, 298 K): δ = −133.9 (m, 2F, o-
3
C6F5), −164.8 (t, JFF = 20.1 Hz, 1F, p-C6F5), −167.7 (m, 2F, m-
C6F5), [Δδ19Fp,m = 2.9]. 11B{1H} NMR (160 MHz, CD2Cl2, 298 K): δ
= −25.5 (ν1/2 ∼ 40 Hz). 11B NMR (160 MHz, CD2Cl2, 298 K): δ =
1
−25.5 (d, JBH ∼ 93 Hz).
11B NMR (160 MHz, CD2Cl2, 298 K): δ = −25.4 (d, JBH ∼ 93 Hz).
X-ray Crystal Structure Analysis of 2b. Formula, C47H47BF15P *
C4H8O, M = 1010.73; colorless crystal, 0.30 × 0.23 × 0.17 mm; a =
11.2833(3) Å, b = 12.7521(4) Å, c = 18.8957(14) Å, α = 97.043(2)°, β
= 101.311(4)°, γ = 111.568(2)°; V = 2422.2(2) Å3; ρcalc = 1.386 g
cm−3; μ = 1.347 mm−1; empirical absorption correction (0.688 ≤ T ≤
0.803); Z = 2; triclinic, space group P1 bar (No. 2); λ = 1.54178 Å; T
= 223 K; ω and φ scans, 35 859 reflections collected ( h, k, l),
[(sinθ)/λ] = 0.60 Å−1, 8362 independent (Rint = 0.049) and 6877
observed reflections [I ≥ 2σ(I)]; 640 refined parameters, R = 0.059,
wR2 = 0.168; max. residual electron density 0.48 (−0.51) e Å−3;
hydrogen atoms at P and B from difference Fourier map, the others
calculated and refined as riding atoms.
Preparation of Compound 2b-D2. In a 10 mL Schlenk flask,
tBuXPhos (50.0 mg, 118 μmol, 1 equiv) and tris(pentafluorophenyl)-
borane (60.3 mg, 118 μmol, 1 equiv) were dissolved in pentane (3
mL). The solution was stirred for 10 min. Then Schlenk flask was then
evacuated, and deuterium gas (2 bar) was added. After 1 h, an oily
residue was obtained. The solution was stirred for 12 h at room
temperature, and a white solid precipitated. The solution was removed,
and the residue was dried in vacuo. The product was obtained as a
1
X-ray Crystal Structure Analysis of 2a. Formula C51H51BF15P,
M = 990.70; colorless crystal, 0.20 × 0.12 × 0.12 mm; a = 12.6283(5)
Å, b = 13.1720(5) Å, c = 16.6906(8) Å, α = 71.304(2)°, β = 70.488(2)
°, γ = 70.734(2)°; V = 2400.31(17) Å3; ρcalc = 1.371 g cm−3; μ = 1.334
mm−1; empirical absorption correction (0.776 ≤ T ≤ 0.856); Z = 2;
triclinic, space group P1 bar (No. 2); λ = 1.54178 Å; T = 223 K; ω and
φ scans, 30 346 reflections collected ( h, k, l), [(sinθ)/λ] = 0.60
Å−1, 8313 independent (Rint = 0.065) and 6216 observed reflections [I
≥ 2σ(I)]; 625 refined parameters, R = 0.054, wR2 = 0.137; max.
residual electron density 0.20 (−0.27) e Å−3; hydrogen atoms at P and
B from difference Fourier map, the others calculated and refined as
riding atoms.
Preparation of Compound 2a-D2. In a 10 mL Schlenk flask,
XPhos (50.0 mg, 105 μmol, 1 equiv) and tris(pentafluorophenyl)-
borane (53.7 mg, 105 μmol, 1 equiv) were dissolved in pentane (3
mL). The solution was stirred for 10 min. The Schlenk flask was then
evacuated, and deuterium gas (2 bar) was added. After 1 h, an oily
residue was obtained. The solution was stirred for 12 h at room
temperature, and a white solid precipitated. The solution was removed
and the residue dried in vacuo. The product was obtained as a white
solid in 68% (70.8 mg, 71.4 μmol) yield. 1H NMR (500 MHz, CD2Cl2,
298 K): δ = 7.87 (m, 1H, 4-H), 7.69 (m, 1H, 3-H), 7.68 (m, 1H, 2-H),
7.59 (m, 1H, 5-H), 7.18 (s, 2H, m-tipp), 2.97 (sept, 3JHH = 7.1 Hz, 1H,
p-iPrCH), 2.43, 1.98/1.40, 1.90/1.35, 1.86/1.28, 1.77/1.21, 1.75/1.32
1
white solid in 45% (49.9 mg, 53.1 μmol) yield. H NMR (500 MHz,
CD2Cl2, 298 K): δ = 7.88 (m, 1H, 4-H), 7.78 (m, 1H, 2-H), 7.72 (m,
1
1H, 3-H), 7.64 (m, 1H, 5-H), 7.17 (s, 2H, m-tipp), 5.58 (d, JPH
=
453.4 Hz, 1H, PH), 2.96 (sept, 3JHH = 6.8 Hz, 1H, p-iPrCH), 2.26 (sept,
3JHH = 6.7 Hz, 2H, o-iPrCH), 1.44 (d, JPH = 17.4 Hz, 18H, tBu), 1.30
3
3
(each m, each 2H, Cy), 2.19 (sept, JHH = 6.8 Hz, 2H, o-iPrCH), 1.30
(d, 3JHH = 6.8 Hz, 6H, p-iPrCH ), 1.24, 1.00 (each d, each JHH = 6.7 Hz,
3
3
3
(d, 3JHH = 6.8 Hz, 6H, p-iPrCH ), 1.26 ( JHH = 6.8 Hz), 1.01 (3JHH = 6.8
3
each 6H, o-iPrCH ), [ca. 45% PH: δ = 5.58 (d, JPH = 453.4 Hz, PH)].
1
3
Hz) (each d, each 6H, o-iPrCH ), [ca. 17% PH: δ = 5.52 (dt, JPH
=
1
3
2H NMR (77 MHz, CH2Cl2, 298 K): δ = 5.58 (d, 1JPD = 69.7 Hz, 1D,
465.1 Hz, 3JHH = 5.6 Hz, PH)]. 2H NMR (77 MHz, CH2Cl2, 298 K): δ
PD), 3.56 (br, 1.5D, BD). 31P{1H} NMR (202 MHz, CD2Cl2, 298 K):
= 5.48 (d, 1JPD = 71.3 Hz, 1D, PD), 3.63 (br, 1D, BD). 31P{1H} NMR
δ = 31.9 (ca. 50%, PH), 31.1 (ca. 50%, 1:1:1 t, 1JPD ∼ 69 Hz, PD). 31
P
1
1
(202 MHz, CD2Cl2, 298 K): δ = 15.1 (PH), 14.4 (1:1:1 t, JPD ∼ 71
NMR (202 MHz, CD2Cl2, 298 K): δ = 31.9 (br d, JPH ∼ 450 Hz,
PH), 31.1 (br, PD). 11B{1H} NMR (160 MHz, CD2Cl2, 298 K): δ =
−25.6 (ν1/2 ∼ 60 Hz). 11B NMR (160 MHz, CD2Cl2, 298 K): δ =
−25.6 (ν1/2 ∼ 60 Hz).
Hz, PD). 31P NMR (202 MHz, CD2Cl2, 298 K): δ = 15.1 (ca. 14%, br
1
1
d, JPH ∼ 470 Hz, PH), 14.4 (ca. 86%, 1:1:1 t, JPD ∼ 71 Hz, PD).
11B{1H} NMR (160 MHz, CD2Cl2, 298 K): δ = −25.6 (ν1/2 ∼ 70 Hz).
11B NMR (160 MHz, CD2Cl2, 298 K): δ = −25.6 (ν1/2 ∼ 70 Hz).
Preparation of Compound 2b. In a 10 mL Schlenk flask,
tBuXPhos (50.0 mg, 118 μmol, 1 equiv) and tris(pentafluorophenyl)-
borane (60.3 mg, 118 μmol, 1 equiv) were dissolved in pentane (3
mL). The solution was stirred for 10 min. The Schlenk flask was then
evacuated, and dihydrogen gas (2 bar) was added. After 1 h, an oily
residue was obtained. The solution was stirred for 12 h at room
temperature, and a white solid precipitated. The solution was removed,
and the residue was dried in vacuo. The product was obtained as a
white solid in 65% (72.0 mg, 76.7 μmol) yield. Crystals suitable for X-
ray crystal structure analysis were obtained from a solution of 2b in
dichloromethane covered with heptane at −30 °C. Anal. Calcd for
C47H47BF15P (M = 938.64 g/mol): C, 60.14; H, 5.05. Found: C,
59.81; H, 4.77. mp: 127.1 °C. 1H NMR (500 MHz, CD2Cl2, 298 K): δ
= 7.88 (m, 1H, 4-H), 7.78 (m, 1H, 2-H), 7.72 (m, 1H, 3-H), 7.64 (m,
Preparation of Compound 2c. In a 10 mL Schlenk flask,
ethyldimesitylphosphane (48.1 mg, 162 μmol, 1 equiv) and tris-
(pentafluorophenyl)borane (83.0 mg, 162 μmol, 1 equiv) were
dissolved in pentane (3 mL). The yellow solution was stirred for 10
min. The Schlenk flask was then evacuated, and dihydrogen gas (2
bar) was added. After 1 h, an oily residue was obtained. The solution
was stirred for 12 h at room temperature. After evaporation of the
solvent in vacuo, the product was obtained as a colorless oil in 80%
(105.3 mg, 129.6 μmol) yield. Anal. Calcd for C38H29BF15P (M =
812.40 g/mol): C, 56.18; H, 3.60. Found: C, 56.00; H, 3.78. 1H NMR
(500 MHz, CD2Cl2, 233 K): δ = 7.53 (dt, 1JPH = 473.1 Hz, 3JHH = 7.1
Hz, 1H, PH), 7.05 (m, 4H, m-Mes), 3.54 (br q {partial relaxed}, 1H,
BH), 2.87 (m, 2H, EtCH ), 2.38 (s, 12H, o-Me), 2.31 (s, 6H, p-Me),
P
2
1.36 (dt, JPH = 23.6 Hz, JHH = 7.2 Hz, 3H, EtCH ). 13C{1H} NMR
3
3
P
3
1
(126 MHz, CD2Cl2, 233 K): δ = 147.9 (dm, JFC = 236 Hz, o-C6F5),
1
4
1
1H, 5-H), 7.17 (s, 2H, m-tipp), 5.58 (d, JPH = 453.4 Hz, 1H, PH),
146.6 (p-Mes), 143.1 (d, JPC = 10.4 Hz, o-Mes), 137.5 (dm, JFC
∼
=
1
3.59 (1:1:1:1 q {partial relaxed}, JBH ∼ 90 Hz, 1H, BH), 2.96 (sept,
245 Hz, p-C6F5), 136.3 (dm, 1JFC ∼ 247 Hz, m-C6F5), 132.0 (d, 3JPC
2806
dx.doi.org/10.1021/om201076f | Organometallics 2012, 31, 2801−2809

Organometallics
Article
1
11.1 Hz, m-Mes), 124.5 (i-C6F5), 109.9 (d, JPC = 81.4 Hz, i-Mes),
= 0.049, wR2 = 0.141, Flack parameter 0.06(3); max. residual electron
density 0.28 (−0.16) e Å−3; hydrogen atoms calculated and refined as
riding atoms.
3
1
22.0 (d, JPC = 7.8 Hz, o-Me), 21.1 (p-Me), 18.5 (d, JPC = 45.6 Hz,
PEtCH ), 9.1 (d, JPC = 4.1 Hz, PEtCH ). 31P{1H} NMR (202 MHz,
CD2Cl2, 233 K): δ = −7.5 (ν1/2 ≈ 5 Hz), [−19.3, tentatively assigned
as 1c]. 31P NMR (202 MHz, CD2Cl2, 233 K): δ = −7.5 (ca. 83%, dm,
1JPH ∼ 473 Hz), [−19.3 (ca. 17%, tentatively assigned as 1c]. 19F NMR
(470 MHz, CD2Cl2, 233 K): δ = −134.0 (m, 2F, o-C6F5), −163.7 (m,
1F, p-C6F5), −166.8 (m, 2F, m-C6F5), [Δδ19Fp,m = 3.1]. 11B{1H} NMR
(160 MHz, CD2Cl2, 233 K): δ = −25.5 (ν1/2 ∼ 95 Hz). 11B NMR (160
2
2
3
Preparation of Compound 3c. In a 10 mL Schlenk flask,
ethyldimesitylphosphane (50.0 mg, 168 μmol, 1 equiv) and tris-
(pentafluorophenyl)borane (85.6 mg, 168 μmol, 1 equiv) were
dissolved in pentane (3 mL). The solution was stirred for 10 min.
The Schlenk flask was then evacuated, and ethene gas (2 bar) was
added. A white solid precipitated during the reaction time of 48 h at
room temperature. The solution was removed, and the residue was
dried in vacuo. After fractional crystallization with dichloromethane
and pentane, the product was obtained as a white solid in 52% (73.2
mg, 87.4 μmol) yield. Crystals suitable for X-ray crystal structure
analysis were obtained from a solution of 3c in dichloromethane
covered with heptane at −30°. Anal. Calcd for C40H31BF15P (M =
838.43 g/mol): C, 57.30; H, 3.73. Found: C, 56.72; H, 3.75. mp: 257.6
1
MHz, CD2Cl2, 233 K): δ = −25.5 (d, JBH ∼ 82 Hz).
Preparation of Compound 2c-D2. In a 10 mL Schlenk flask,
ethyldimesitylphosphane (48.1 mg, 162 μmol, 1 equiv) and tris-
(pentafluorophenyl)borane (83.0 mg, 162 μmol, 1 equiv) were
dissolved in pentane (3 mL). The yellow solution was stirred for 10
min. The Schlenk flask was then evacuated, and deuterium gas (2 bar)
was added. After 1 h, an oily residue was obtained. The solution was
stirred for 12 h at room temperature. After evaporation of the solution
in vacuo, the product was obtained as a colorless oil in 90% (118.7 mg,
145.8 μmol) yield. 1H NMR (500 MHz, CD2Cl2, 298 K): δ = 7.10 (m,
1
°C. H NMR (500 MHz, CD2Cl2, 288 K): δ = 6.94 (m, 4H, m-Mes),
P
2.88 (m, 2H, EtCH ), 2.51 (m, 2H, PCH2), 2.30 (s, 6H, p-Me), 2.12
2
3
(br s, 12H, o-Me), 1.30 (br m, 2H, BCH2), 1.10 (dt, JPH = 20.7 Hz,
3
P
JHH = 7.5 Hz, 3H, EtCH ). 13C{1H} NMR (126 MHz, CD2Cl2, 288
3
4H, m-Mes), 2.89 (m, 2H, PEtCH ), 2.41 (s, 12H, o-Me), 2.35 (s, 6H, p-
2
K): δ = 148.4 (dm, 1JFC ∼ 240 Hz, o-C6F5), 144.6 (d, 4JPC = 2.9 Hz, p-
Me), 1.41 (dt, JP1H = 23.6 Hz, JHH = 7.3 Hz, 3H, EtCH ), [ca. 10%
3
3
P
3
2
1
2
Mes), 142.1 (d, JP1C = 9.1 Hz, o-Mes), 138.2 (dm, JFC3 ∼ 245 Hz, p-
C6F5), 136.9 (dm, JFC ∼ 243 Hz, m-C6F5), 132.8 (d, JPC = 11.2 Hz,
m-Mes), 125.3 (i-C6F5), 117.9 (d, 1JPC = 75.4 Hz, i-Mes), 25.9 (d, 1JPH
= 38.0 Hz, PCH2), 23.5 (br, o-Me), 21.0 (d, 5JPC = 1.5 Hz, p-Me), 20.5
PH: δ = 5.57 (d, JPH ∼ 472 Hz, PH)]. H NMR (77 MHz, CH2Cl2,
1
298 K): δ = 7.60 (d, JPD = 72.2 Hz, 1D, PD), 3.61 (br, 1D, BD).
31P{1H} NMR (202 MHz, CD2Cl2, 298 K): δ = −7.3 (11%, PH), −7.8
(89%, 1:1:1 t, 1JPD = 72.3 Hz, PD). 31P NMR (202 MHz, CD2Cl2, 298
K): δ = −7.3 (br d, PH), −7.8 (br 1:1:1 t, PD). 11B{1H} NMR (160
MHz, CD2Cl2, 298 K): δ = −25.6 (ν1/2 ∼ 60 Hz). 11B NMR (160
MHz, CD2Cl2, 298 K): δ = −25.6 (ν1/2 ∼ 60 Hz).
(d, JPC = 48.7 Hz, EtCH ), 15.5 (br, BCH2), 7.2 (d, JPC = 3.6 Hz,
1
P
2
2
PEtCH ). 31P{1H} NMR (202 MHz, CD2Cl2, 288 K): δ = 36.1 (ν1/2
∼
3
80 Hz). 19F NMR (470 MHz, CD2Cl2, 288 K): δ = −133.1 (m, 2F, o-
3
C6F5), −162.8 (t, JFF = 20.5 Hz, 1F, p-C6F5), −166.3 (m, 2F, m-
Preparation of Compound 3b. In a 10 mL Schlenk flask,
tBuXPhos (50.0 mg, 118 μmol, 1 equiv) and tris(pentafluorophenyl)-
borane (60.3 mg, 118 μmol, 1 equiv) were dissolved in pentane (3
mL). The solution was stirred for 10 min. The Schlenk flask was then
evacuated, and ethene gas (2 bar) was added to the solution. The
solution was stirred for 48 h at room temperature. The obtained white
precipitated was collected and dried in vacuo. After fractional
crystallization with dichloromethane and pentane, the product was
obtained as a white solid in 80% (91.1 mg, 94.4 μmol) yield. Crystals
suitable for X-ray crystal structure analysis were obtained from a
solution of 3b in dichloromethane covered with heptane at −30 °C.
Anal. Calcd for C49H49BF15P (M = 964.67 g/mol): C, 61.01; H, 5.12.
Found: C, 60.07; H, 5.43. mp: 253.8 °C. 1H NMR (600 MHz, CD2Cl2,
298 K): δ = 7.93 (m, 1H, 2-H), 7.63 (m, 1H, 4-H), 7.54 (m, 1H, 3-H),
7.25 (m, 1H, 5-H), 7.00 (s, 2H, m-tipp), 2.58 (sept, 3JHH = 7.0 Hz, 1H,
C6F5), [Δδ19Fp,m = 3.5]. 11B{1H} NMR (160 MHz, CD2Cl2, 288 K): δ
= −13.1 (ν1/2 ∼ 50 Hz).
X-ray Crystal Structure Analysis of 3c. Formula C40H31BF15P,
M = 838.43; colorless crystal, 0.12 × 0.07 × 0.05 mm; a = 11.1241(6)
Å, b = 12.3049(7) Å, c = 15.8458(9) Å, α = 104.190(5)°, β =
100.058(4)°, γ = 113.002(6)°; V = 1844.6(2) Å3; ρcalc = 1.510 g cm−3;
μ = 1.627 mm−1; empirical absorption correction (0.829 ≤ T ≤ 0.923);
Z = 2; triclinic, space group P1 bar (No. 2); λ = 1.54178 Å; T = 223 K;
ω and φ scans, 21 460 reflections collected ( h, k, l), [(sinθ)/λ]
= 0.60 Å−1, 6362 independent (Rint = 0.050) and 4973 observed
reflections [I ≥ 2σ(I)]; 521 refined parameters, R = 0.049, wR2 =
0.128; max. residual electron density 0.28 (−0.32) e Å−3; hydrogen
atoms calculated and refined as riding atoms.
Preparation of Compound 3d. In a 10 mL Schlenk flask,
ethyldimesitylphosphane (74.0 mg, 290 μmol, 1 equiv) and bis-
(pentafluorophenyl)borane (100.0 mg, 290 μmol, 1 equiv) were
combined in pentane (3 mL). The suspension was stirred for 10 min.
The Schlenk flask was then evacuated, and ethene gas (2 bar) was
added. Within 3 min, the suspension turned into a clear solution; after
an additional 35 min, a white solid precipitated. The reaction mixture
was stirred for 48 h at room temperature. The solution was then
removed and the residue dried in vacuo. After fractional crystallization
with dichloromethane and pentane, the product was obtained as a
white solid in 42% (89.4 mg, 127.6 μmol) yield. Crystals suitable for
X-ray crystal structure analysis were obtained from a solution of 3d in
dichloromethane covered with heptane at −30 °C. Anal. Calcd for
C36H36BF10P (M = 700.43 g/mol): C, 61.73; H, 5.18. Found: C,
61.42; H, 5.37. mp: 193.9 °C. 1H NMR (600 MHz, CD2Cl2, 298 K): δ
p-iPrCH), 2.25 (sept, JHH = 6.9 Hz, 2H, o-iPrCH), 1.81 (m, 4H, PCH2,
3
3
BCH2), 1.51 (d, JPH = 14.8 Hz, 18H, tBu), 1.10, 0.87 (each d, each
JHH = 6.7 Hz, each 6H, o-iPrCH ), 1.03 (d, JHH = 6.9 Hz, 6H,
3
3
3
p-iPrCH ), [ca. 15% BuXPhosH: δ = 5.59 (d, JPH = 454.2 Hz, PH),
t
1
3
2.97 (sept, JHH = 7.0 Hz, 1H, p-iPrCH)]. 13C{1H} NMR (151 MHz,
3
1
CD2Cl2, 298 K): δ = 150.4 (p-tipp), 148.5 (dm, JFC ∼ 239 Hz, o-
C6F5), 147.8 (d, 2JPC = 4.8 Hz, C-6), 145.6 (o-tipp), 138.5 (dm, 1JFC
245 Hz, p-C6F5), 136.8 (dm, 1JFC ∼ 238 Hz, m-C6F5), 136.7 (d, 3JPC
∼
=
10.6 Hz, C-5), 135.9 (d, 2JPC = 7.8 Hz, C-2), 134.1 (i-tipp), 132.5 (C-
3
4), 126.4 (d, JPC = 10.3 Hz, C-3), 125.0 (i-C6F5), 122.0 (m-tipp),
1
1
120.4 (d, JPC = 58.3 Hz, C-1), 39.4 (d, JPC = 32.8 Hz, tBu), 33.8
(p-iPrCH), 31.3 (o-iPrCH), 29.5 (tBu), 26.6, 21.4 (o-iPrCH ), 23.2
3
(p-iPrCH ), 21.0 (d, JPC = 27.9 Hz, PCH2), 18.4 (br, BCH2). 31P{1H}
1
3
= 6.94 (d, 4JHH = 4.0 Hz, 4H, m-Mes), 2.86 (dq, 3JPH = 11.8 Hz, 3JHH
=
NMR (243 MHz, CD2Cl2, 298 K): δ = 49.8 (ca. 82%, ν1/2 ∼ 60 Hz),
[31.8 (ca. 18%, tentatively assigned as BuXPhosH+]. 19F NMR (564
t
7.4 Hz, 2H, PEtCH ), 2.49 (m, 2H, PCH2), 2.30 (s, 6H, p-Me), 2.20 (br
2
MHz, CD2Cl2, 298 K): δ = −131.2 (m, 2F, o-C6F5), −163.5 (t, 3JFF
=
3
3
P
s, 12H, o-Me), 1.03 (dt, JPH = 20.4 Hz, JHH = 7.4 Hz, 3H, EtCH ),
3
20.0 Hz, 1F, p-C6F5), −166.3 (m, 2F, m-C6F5), [Δδ19Fp,m = 2.8].
11B{1H} NMR (192 MHz, CD2Cl2, 298 K): δ = −14.1 (ν1/2 ∼ 70 Hz).
X-ray Crystal Structure Analysis of 3b. Formula C49H49BF15P,
M = 964.66; colorless crystal, 0.35 × 0.25 × 0.20 mm; a = 12.0517(3)
Å, b = 16.2929(5) Å, c = 23.8126(7) Å; V = 4675.8(2) Å3; ρcalc = 1.370
g cm−3; μ = 1.354 mm−1; empirical absorption correction (0.649 ≤ T ≤
0.773); Z = 4; orthorhombic, space group P212121 (No. 19); λ =
1.54178 Å; T = 223 K; ω and φ scans, 44 201 reflections collected
( h, k, l), [(sinθ)/λ] = 0.60 Å−1, 8188 independent (Rint = 0.057)
and 7981 observed reflections [I ≥ 2σ(I)]; 607 refined parameters, R
1.01 (br, 2H, BCH2), 0.80 (q, 3JHH = 7.3 Hz, 2H, BEtCH ), 0.44 (t, JHH
3
2
= 7.8 Hz, 3H, BEtCH ). 13C{1H} NMR (151 MHz, CD2Cl2, 298 K): δ =
3
1
4
148.3 (dm, JFC ∼ 234 Hz, o-C6F5), 144.4 (d, JPC = 2.9 Hz, p-Mes),
2
1
142.2 (d, JPC = 9.2 Hz, o-Mes), 137.5 (dm, JFC ∼ 245 Hz, p-C6F5),
136.7 (dm, 1JFC ∼ 245 Hz, m-C6F5), 132.7 (d, 3JPC = 11.2 Hz, m-Mes),
1
1
129.5 (i-C6F5), 118.6 (d, JPC = 74.6 Hz, i-Mes), 26.1 (d, JPH = 36.1
1
Hz, PCH2), 23.6 (br, o-Me), 21.1 (p-Me), 20.5 (d, JPC = 49.8 Hz,
PEtCH ), 15.4 (br, BCH2) , 14.3 (br, Et ) , 10.9 ( Et ), 7.3 (d, JPC
t
B
CH2
t
B
CH3
2
2
= 3.2 Hz, EtCH ), [ tentative assignment]. 31P{1H} NMR (243 MHz,
P
t
3
CD2Cl2, 298 K): δ = 35.5 (ν1/2 ∼ 40 Hz). 19F NMR (564 MHz,
2807
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Article
3
1
CD2Cl2, 298 K): δ = −133.4 (m, 2F, o-C6F5), −164.7 (t, JFF = 20.5
Hz, 1F, p-C6F5), −166.9 (m, 2F, m-C6F5), [Δδ19Fp,m = 2.2]. 11B{1H}
NMR (192 MHz, CD2Cl2, 298 K): δ = −10.4 (ν1/2 ∼ 70 Hz).
X-ray Crystal Structure Analysis of 3d. Formula C36H36BF10P,
M = 700.43; colorless crystal, 0.20 × 0.10 × 0.05 mm; a = 10.2366(2)
Å, b = 23.1031(5) Å, c = 14.2896(3) Å, β = 90.937(1)°; V =
3379.00(12) Å3; ρcalc = 1.377 g cm−3; μ = 1.440 mm−1; empirical
absorption correction (0.762 ≤ T ≤ 0.932); Z = 4; monoclinic, space
group P21/c (No. 14); λ = 1.54178 Å; T = 223 K; ω and φ scans, 27
971 reflections collected ( h, k, l), [(sinθ)/λ] = 0.60 Å−1, 5915
independent (Rint = 0.082) and 4344 observed reflections [I ≥ 2σ(I)];
441 refined parameters, R = 0.054, wR2 = 0.143; max. residual electron
density 0.27 (−0.27) e Å−3; hydrogen atoms calculated and refined as
riding atoms.
Found: C, 55.51; H, 3.88. Decomp.: 175.8 °C. H NMR (500 MHz,
CD2Cl2, 253 K): δ = 6.98 (d, 4JHH = 4.5 Hz, 4H, m-Mes), 3.12 (m, 2H,
PEtCH ), 2.31 (s, 6H, p-Me), 2.14 (s, 12H, o-Me), 1.17 (dt, JPH = 21.5
2
2
Hz, JHH = 7.4 Hz, 3H, EtCH ). 13C{1H} NMR (126 MHz, CD2Cl2,
253 K): δ = 162.5 (d, 1JPC = 118.8 Hz, PCO2), 147.2 (dm, 1JFC ∼ 240
Hz, o-C6F5), 145.1 (d, 4JPC = 3.0 Hz, p-Mes), 142.7 (d, 2JPC = 9.5 Hz,
o-Mes), 139.1 (dm, 1JFC ∼ 246 Hz, p-C6F5), 136.7 (dm, 1JFC ∼ 245 Hz,
3
P
3
3
m-C6F5), 132.2 (d, JPC = 11.5 Hz, m-Mes), 118.7 (i-C6F5), 114.9 (d,
1JPC = 71.1 Hz, i-Mes), 23.3 (d, JPC = 4.6 Hz, o-Me), 22.6 (d, JPC
=
3
1
42.1 Hz, PEtCH ), 21.0 (d, JPC = 1.4 Hz, p-Me), 8.2 (d, 2JPC = 5.1 Hz,
5
2
PEtCH ). 31P{1H} NMR (202 MHz, CD2Cl2, 253 K): δ = 16.3 (br m).
3
19F NMR (470 MHz, CD2Cl2, 253 K): δ = −134.6 (m, 2F, o-C6F5),
3
−160.2 (t, JFF = 20.7 Hz, 1F, p-C6F5), −165.7 (m, 2F, m-C6F5),
[Δδ19Fp,m = 5.5]. 11B{1H} NMR (160 MHz, CD2Cl2, 253 K): δ = −2.4
(ν1/2 ∼ 600 Hz).
Preparation of Compound 4a. In a 10 mL Schlenk flask, XPhos
(50.0 mg, 105 μmol, 1 equiv) and tris(pentafluorophenyl)borane (53.7
mg, 105 μmol, 1 equiv) were dissolved in pentane (3 mL). The
solution was stirred for 10 min. The Schlenk flask was then evacuated,
and carbon dioxide gas (2 bar) was added. After 20 min, a white solid
started to precipitate. The suspension was cooled to −20 °C and
stirred for 2 h. The solution was then removed and the residue dried in
vacuo. The product was obtained as a white solid in 80% (86.7 mg,
84.0 μmol) yield. Crystals suitable for X-ray crystal structure analysis
could be obtained from a solution of 4a in dichloromethane covered
with heptane at −30 °C. Anal. Calcd for C52H49BF15O2P (M =
1032.71 g/mol): C, 60.48; H, 4.78. Found: C, 60.36; H, 4.73. mp:
X-ray Crystal Structure Analysis of 4c. Formula C39H27BF10O2P
* CH2Cl2, M = 939.31; colorless crystal, 0.40 × 0.10 × 0.07 mm; a =
11.8807(4) Å, b = 13.8628(3) Å, c = 24.3570(7) Å, β = 98.872(2)°; V
= 3963.6(2) Å3; ρcalc = 1.574 cm−3; μ = 2.835 mm−1; empirical
absorption correction (0.397 ≤ T ≤ 0.826); Z = 4; monoclinic, space
group P21/c (No. 14); λ = 1.54178 Å; T = 223 K; ω and φ scans, 31
946 reflections collected ( h, k, l), [(sinθ)/λ] = 0.60 Å−1, 6963
independent (Rint = 0.054) and 6009 observed reflections [I ≥ 2σ(I)];
557 refined parameters, R = 0.053, wR2 = 0.145; max. residual electron
density 0.59 (−0.80) e Å−3; hydrogen atoms calculated and refined as
riding atoms.
1
121.7 °C. H NMR (500 MHz, CD2Cl2, 263 K): δ = 7.70 (m, 1H, 4-
H), 7.65 (m, 1H, 2-H), 7.51 (m, 1H, 3-H), 7.26 (m, 1H, 5-H), 7.09 (s,
2H, m-tipp), 2.92 (sept, 3JHH = 6.8 Hz, 1H, p-iPrCH), 2.67 (CH), 2.14/
1.48, 1.81/1.12, 1.63/1.14, 1.62/0.73, 1.53/1.43 (each br, each 2H,
ASSOCIATED CONTENT
* Supporting Information
Text and figures giving further experimental, spectroscopic
details and crystallographic data. This material is available free
of charge via the Internet at http://pubs.acs.org.
■
S
3
3
Cy), 2.24 (sept, JHH = 6.8 Hz, 2H, o-iPrCH), 1.25 (d, JHH = 6.8 Hz,
3
6H, p-iPrCH ), 1.07, 0.86 (each d, each JHH = 6.8 Hz, each 6H,
3
o-iPrCH ). 13C{1H} NMR (126 MHz, CD2Cl2, 263 K): δ = 162.5 (d,
3
1JPC = 116.0 Hz, PCO2), 150.9 (p-tipp), 147.9 (dm, 1JFC ∼ 238 Hz, o-
C6F5), 146.7 (o-tipp), 145.4 (d, 2JPC = 6.4 Hz, C-6), 139.4 (dm, 1JFC
251 Hz, p-C6F5), 136.8 (dm, 1JFC ∼ 245 Hz, m-C6F5), 135.7 (d, 3JPC
∼
=
AUTHOR INFORMATION
Corresponding Author
*E-mail: erker@uni-muenster.de.
■
11.3 Hz, C-5), 134.0 (d, 2JPC = 10.4 Hz, C-2), 133.8 (d, 3JPC = 1.9 Hz,
4
3
i-tipp), 133.3 (d, JPC = 3.2 Hz, C-4), 128.4 (d, JPC = 11.7 Hz, C-3),
121.9 (m-tipp), 119.3 (i-C6F5), 115.5 (d, JPC = 64.5 Hz, C-1), 34.58
1
Author Contributions
3
†X-ray crystal structure analyses.
(CH), 27.6, 27.0, 26.9, 26.8 (d, JHH = 2.9 Hz), 25.3 (each br, Cy),
34.7 (p-iPrCH), 31.0 (o-iPrCH), 25.7, 21.8 (o-iPrCH ), 24.0 (p- Pr ).
i
CH3
3
31P{1H} NMR (202 MHz, CD2Cl2, 263 K): δ = 26.8 (ν1/2 ∼ 4 Hz),
ACKNOWLEDGMENTS
Financial support from the Deutsche Forschungsgemeinschaft
is gratefully acknowledged.
1
■
[14.7 (ca. 8%, br d, JPH ∼ 468 Hz, PH: tentatively assigned as
XPhosH+)]. 19F NMR (470 MHz, CD2Cl2, 263 K): δ = −133.9 (m,
2F, o-C6F5), −160.5 (t, 3JFF = 20.6 Hz, 1F, p-C6F5), −165.7 (m, 2F, m-
C6F5), [Δδ19Fp,m = 5.2]. 11B{1H} NMR (160 MHz, CD2Cl2, 263 K): δ
= −2.7.
DEDICATION
■
‡Dedicated to the memory of Professor F. Gordon A. Stone.
X-ray Crystal Structure Analysis of 4a. Formula
C52H49BF15O2P, M = 1032.69; colorless crystal, 0.15 × 0.10 × 0.03
mm; a = 9.2878(4) Å, b = 12.0852(5) Å, c = 22.1319(11) Å, α =
85.623(2)°, β = 82.110(2)°, γ = 81.036(2)°; V = 2426.79(19) Å3; ρcalc
= 1.413 g cm−3; μ = 1.377 mm−1; empirical absorption correction
(0.820 ≤ T ≤ 0.960); Z = 2; triclinic, space group P1 bar (No. 2); λ =
1.54178 Å; T = 223 K; ω and φ scans, 30 139 reflections collected
( h, k, l), [(sinθ)/λ] = 0.60 Å−1, 8393 independent (Rint = 0.081)
and 5990 observed reflections [I ≥ 2σ(I)]; 646 refined parameters, R
= 0.057, wR2 = 0.141; max. residual electron density 0.60 (−0.28) e
Å−3; hydrogen atoms calculated and refined as riding atoms.
Preparation of Compound 4c. In a 10 mL Schlenk flask,
ethyldimesitylphosphane (43.0 mg, 145 μmol, 1 equiv) and tris-
(pentafluorophenyl)borane (74.2 mg, 145 μmol, 1 equiv) were
dissolved in pentane (3 mL). The solution was stirred for 10 min.
The Schlenk flask was then evacuated, and carbon dioxide gas (2 bar)
was added. After 20 min, a white solid started to precipitate. The
solution was cooled to −20 °C and stirred for 2 h. The solution was
then removed and the residue dried in vacuo. The product was
obtained as a white solid in 75% (92.9 mg, 108.8 μmol) yield. Crystals
suitable for X-ray crystal structure analysis could be obtained from a
solution of 4c in dichloromethane covered with heptane −30 °C. Anal.
Calcd for C51H51BF15P (M = 854.39 g/mol): C, 54.82; H, 3.19.
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