Noninteracting, vicinal frustrated P/B-Lewis pair at the norbornane framework: Synthesis, characterization, and reactions

Article abstract of DOI:10.1021/ja400338e

Hydroboration of dimesitylnorbornenylphosphane with Piers' borane [HB(C₆F₅)₂] gave the frustrated Lewis pair (FLP) 4 in good yield. It has the -PMes₂ Lewis base attached at the 2-endo position and the -B(C₆F₅)₂ group 3-exo oriented at the norbornane framework. The vicinal FLP 4 was shown by X-ray diffraction and by spectroscopy to be a rare example of an intramolecular noninteracting pair of a Lewis acid and Lewis base functionality. The FLP 4 rapidly splits dihydrogen heterolytically at ambient temperature to yield the phosphonium/hydrido borate zwitterion 5. It adds to the carbonyl group of benzaldehyde and to carbon dioxide to yield the adducts 6 and 7, respectively. Compounds 5-7 were characterized by X-ray diffraction. Compound 4 adds to the S=O function of sulfur dioxide to give a pair of diastereomeric heterocyclic six-membered ring products due to the newly formed sulfur chirality center, annulated with the norbornane skeleton, which were investigated by ³¹P/¹¹B single and double resonance solid state NMR experiments. Compound 8 was also characterized by X-ray diffraction. The FLP 4 undergoes a clean N,N-addition to nitric oxide (NO) to give a norbornane annulated five-membered heterocyclic persistent FLP-NO aminoxyl radical 12 (characterized, e.g., by X-ray diffraction and EPR spectroscopy). Additionally, the FLP radical was characterized by ¹H solid state NMR spectroscopy. The radical 12 undergoes a H-atom abstraction reaction with 1,4-cyclohexadiene to yield the respective diamagnetic FLP-NOH product 13, which was also characterized by X-ray diffraction and solid state NMR spectroscopy.

Full text of DOI:10.1021/ja400338e

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Article
A Non-interacting Vicinal Frustrated P/B-Lewis Pair at the
Norbornane Framework: Synthesis, Characterization and Reactions.
Muhammad Sajid, Gerald Kehr, Thomas Wiegand, Hellmut Eckert, Christian Schwickert, Rainer Pöttgen,
Allan Jay P. Cardenas, Timothy H. Warren, Roland Fröhlich, Constantin Gabriel Daniliuc, and Gerhard Erker
J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/ja400338e • Publication Date (Web): 29 Apr 2013
Downloaded from http://pubs.acs.org on May 23, 2013
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Journal of the American Chemical Society
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A Non-interacting Vicinal Frustrated P/B-Lewis Pair at the
Norbornane Framework: Synthesis, Characterization and Re-
actions.
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a
a
b
b
c
Muhammad Sajid, Gerald Kehr, Thomas Wiegand, Hellmut Eckert, Christian Schwickert, Rainer
c
d
d
a
a
Pöttgen, Allan Jay P. Cardenas, Timothy H. Warren, Roland Fröhlich, Constantin G. Daniliuc,
a
Gerhard Erker *
a
OrganischꢀChemisches Institut, Westfälische WilhelmsꢀUniversität, Corrensstr. 40, 48149 Münster, Germany.
b
Institut für Physikalische Chemie and Graduate School of Chemistry Westfälische WilhelmsꢀUniversität, Corrensstr. 28/30,
4
8149 Münster, Germany.
c
Institut für Anorganische und Analytische Chemie, Westfälische WilhelmsꢀUniversität, Corrensstrasse 28/30, 48149 Münster, Germany
Georgetown University, Department of Chemistry, Box 571227, Washington, DC 20057ꢀ1227, USA
d
KEYWORDS frustrated Lewis pair, dihydrogen activation, carbon dioxide, sulfur dioxide, nitric oxide, Hꢀatom abstraction,
11
11 31
B quadrupolar coupling, B/ P solidꢀstate double resonance NMR
ABSTRACT: Hydroboration of dimesitylnorbornenylphosphane with Piers` borane [HB(C F ) ] gave the frustrated Lewis pair
6
5 2
(FLP) 4 in good yield. It has the –PMes Lewis base attached at the 2ꢀendo position and the –B(C F ) group 3ꢀexo oriented at the
2
6 5 2
norbornane framework. The vicinal FLP 4 was shown by Xꢀray diffraction and by spectroscopy to be a rare example of an intramoꢀ
lecular nonꢀinteracting pair of a Lewis acid and Lewis base functionality. The FLP 4 rapidly splits dihydrogen heterolytically at
ambient temperature to yield the phosphonium / hydrido borate zwitterion 5. It adds to the carbonyl group of benzaldehyde and to
carbon dioxide to yield the adducts 6 and 7, respectively. The compounds 5-7 were characterized by Xꢀray diffraction. Compound 4
adds to the S=O function of sulfur dioxide to give a pair of diastereomeric heterocyclic sixꢀmembered ring products due to the newꢀ
31
11
ly formed sulfur chirality center, annulated with the norbornane skeleton which were investigated by P/ B single and double resꢀ
onance solid state NMR experiments. One of the diastereoisomers of 8 was also characterized by Xꢀray diffraction. The FLP 4 unꢀ
dergoes a clean N,Nꢀaddition to nitric oxide (NO) to give a norbornane annulated fiveꢀmembered heterocyclic persistent FLPꢀNO
aminoxyl radical 12 (characterized e.g. by Xꢀray diffraction and esr spectroscopy). Additionally, the FLP radical was characterized
1
by H solid state NMR spectroscopy. The radical 12 undergoes a Hꢀatom abstraction reaction with 1,4ꢀcyclohexadiene to yield the
respective diamagnetic FLPꢀNOH product (13) which was also characterized by Xꢀray diffraction and solid state NMR spectroscoꢀ
py.
INTRODUCTION
Reactions of intermolecular FLPs with small molecules must
find a way to avoid the “termolecularity trap”. DFT calculaꢀ
tions indicated that combinations of such bulky Lewis bases
Frustrated Lewis Pairs (FLPs), i.e. pairs of reactive but suffiꢀ
ciently bulky Lewis acids and Lewis bases that avoid neutralꢀ
izing strong adduct formation, have been shown to react with
t
and acids as e.g. the often used Bu P/B(C F ) pair form “enꢀ
3
6 5 3
1
counter complexes” by van der Waals interaction that preꢀ
orient the FLP for the essential reaction with e.g. H or CO
a variety of small molecules. Activation of dihydrogen by
2
2
heterolytic splitting and utilization of the resulting FLP bound
10,11
+
ꢁ
etc.
Intramolecular FLPs avoid any termolecularity probꢀ
H /H pair in metal free catalytic hydrogenation is one promiꢀ
2,3
lem by having the active Lewis acid and Lewis base compoꢀ
nents tied together by a suitable linker. Many such systems
were described in the recent years and many of them were
shown to exhibit very high reactivity towards activation of
nent feature, but FLPs were also shown to bind to alkenes
4
5
and alkynes, to various carbonyl compounds, to nitrogen
6
7
8
9
oxides (N O , NO ), and even to CO or SO2.
2
2
12ꢀ14
small molecules.
Avoiding termolecularity by formation of
the intramolecular FLP is achieved at the expense of a potenꢀ
tially increased tendency of intramolecular Lewis acidꢀLewis
base adduct formation. Although it is seldom if at all observed
1
3,15
for geminal FLPs,
internal adduct formation is found for
12,16ꢀ18
19
many vicinal FLPs
and systems with longer bridges.
We could show by dynamic NMR spectroscopy that a variety
of vicinal P/B and N/B FLPs undergo rapid ring opening by
reversible P–B or N–B bond cleavage to equilibrate with their
Chart 1.
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not directly observed open isomers of higher energy content.
These then were thought to be the reactive forms of the intraꢀ
reaction has thus brought these two functional groups in a
1
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fixed vicinal orientation at the rigid norbornyl framework (diꢀ
hedral angle P1–C2–C3–B1: 110.7(2)°). The resulting PꢂꢂꢂB
separation is large at 3.878(1) Å, precluding any direct Lewis
acid / Lewis base interaction within this pair of heteroatoms.
Consequently, the coordination geometry at boron is trigonal
planar with a sum of C–B–C angles of 359.7° (individual valꢀ
ues: C3–B1–C31: 121.7(2)°, C3–B1–C41: 121.6(2)°, C31–
B1–C41: 116.4(2)°). The phosphorus atom attains the usual
distorted pseudoꢀtetrahedral coordination geometry, characterꢀ
ized by a sum of C–P1–C angles of 320.5°. We note that comꢀ
pound 4 features a conformational orientation of the bulky aryl
groups at phosphorus and at boron that brings a mesityl πꢀ
system and a C F πꢀsystem facing each other (shortest disꢀ
10,12
molecular FLPs to achieve small molecule activation.
1` equilibrium is a typical example (see Chart 1). The
P–B bond cleavage in this system has an activation barrier of
The
1
≠
ꢀ1
∆
G (298 K) ≈ 12.1±0.3 kcal.mol , i.e. it occurs very rapidly
even at low temperature. Consequently, compound 1 was
shown to rapidly cleave dihydrogen heterolytically even at ꢀ20
°
C to form the zwitterion 2 in high yield. This reaction is
thought to proceed through the open isomer 1` featuring the
C–P and C–B vectors in gauche orientation at the cyclohexane
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framework.
It is probably this kinetically facile generation of the nonꢀ
6
5
quenched reactive intermediates (e.g. 1`) that makes many
16,19
tance between the C21–C29 and the C41–C46 planes: 3.65
Å). This might indicate the presence of a weak πꢀstacking
interacting P/B (or N/B)
vicinal FLPs still good for small
molecule activation. It may, however, be a disadvantage that
the actual reactive open FLP forms (e.g. 1`) are only available
in minute quantities from the closed/open equilibrium (e.g. 1
23
interaction between the –PMes and –B(C F ) groups at the
2
6 5 2
norbornane framework in 4.
1
`). It might be better if it were possible to directly preꢀ
pare analogues of the open forms and prevent their internal
P/B adduct formation geometrically. That we have done by
using a rigid norbornane derived framework to which we have
attached a –PMes Lewis base and a –B(C F ) Lewis acid
2
6 5 2
component stereoselectively such that direct P–B formation
was inhibited. In this account we shall discuss the formation
of this vicinal nonꢀinteracting P/B FLP, present the results of
its structural and spectroscopic characterization and show a
selected series of FLP reactions this system undergoes.
RESULTS AND DISCUSSION
Synthesis of the Vicinal Frustrated Lewis Pair
Norbornene can rather selectively be deprotonated by using
2
1
Figure 1: View of the molecular structure of compound 4
thermal ellipsoids are shown with 30% probability).
“Schlosser´s base”. Consequently, we used a related proceꢀ
dure for the synthesis of 2ꢀdimesitylphosphinonorbornene (3).
Bicyclo[2.2.1]heptene was treated with a 1:1 mixture of potasꢀ
sium tertꢀbutoxide and nꢀbutyllithium in THF. The resulting
norbornenyl carbanion was then quenched with chlorodimesitꢀ
ylphosphane. Workup including sequential chromatographic
separation eventually gave the starting material 3 for our FLP
synthesis in 13% yield. This was acceptable since we needed
only one additional step to arrive at our target molecule 4 (see
(
11
31
Compound 4 was characterized by B and P solid state
11
NMR spectroscopy. The B Hahn echo MAS NMR spectrum
of 4 (see Figure 2) reveals a resonance at δCS = 75.2 ppm (in
1
1
good agreement with the broad B resonance at δCS = 75.0
ppm observed in solution typical for a planarꢀtricoordinate Rꢀ
22
B(C
F
5
)
2
boron Lewis acid ) which is strongly influenced by
6
second order quadrupolar effects. Line shape analysis reveals
a quadrupolar coupling constant C of 4.7 MHz and an asymꢀ
metry parameter η of 0.22. For obtaining the best agreement
31
Scheme 1). For this purpose the phosphane 3 ( P NMR: δ = ꢀ
Q
22
3
7.7) was treated with Piers´ borane [HB(C F ) ] in diꢀ
Q
6
5 2
chloromethane at room temperature. A clean hydroboration
reaction took place and we isolated the frustrated Lewis pair 4
as a yellow solid in 97 % yield.
between the experimental and the simulated spectrum, also
Chemical Shielding Anisotropy (CSA) parameters are includꢀ
ed within those simulations (see Table 1). The experimental
values are in excellent agreement with DFT calculations in the
gas phase for both, the electric field gradient (EFG) and the
magnetic shielding tensors, for the first using a GGA DFT
Scheme 1.
24
25,26
(
B97ꢀD ) and for the latter a hybrid DFT (B3ꢀLYP ) level
of theory (for details see Table 1 and the Supporting Inforꢀ
mation). The extraordinarily large CQ value and the ηQ paꢀ
rameter close to zero both point to a highly symmetric, nearly
perfectly planar threeꢀcoordinated boron species. Together
with the strongly positive isotropic chemical shift value, all the
1
1
Single crystals of compound 4 for the Xꢀray crystal structure
analysis (see Fig. 1, Table 2 and 3) were obtained by slow
evaporation of solvent from a pentane solution at ꢀ35 °C.
Compound 4 selectively features the –B(C F ) Lewis acid
B NMR parameters indicate that there is no electronic interꢀ
action between the two Lewis centers. This result contrasts
sharply with those obtained for most of the other vicinal P/B
1
7c,18
FLPs investigated so far,
actions result in much lower values for both B δCS and C
values, and where these NMR parameters could be correlated
where significant covalent interꢀ
6
5 2
11
substituent in the exoꢀorientation at carbon atom C3 and the ꢀ
Q
PMes Lewis base substituent in the endoꢀposition at C2. The
2
…
17c,18
defined cisꢀ1,2ꢀaddition stereochemistry of the hydroboration
with intramolecular B P distances and catalytic activities.
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Also the P chemical shifts (δ=ꢀ22.4 ppm in the solid state,
ꢀ21.8 ppm in solution) highlight the special character of 4 in
comparison to the other vicinal FLPs, for which chemical
shifts inꢀbetween 24.5 and 14.5 ppm are observed, which is
typical for the presence of Lewis acid/ꢀbase interactions. Theꢀ
se results are further supported by our DFT calculations of
In solution compound 5 features the typical H and C NMR
1
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5
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5
5
5
6
signals of the disubstituted norbornane framework. It shows
the H NMR resonance of the –PH function as a dd at δ = 7.22
with the typical large J = 476 Hz coupling constant ( J
9 Hz). The P NMR spectrum shows a respective dd at δ = ꢀ
7.4. The –BH unit exhibits a B NMR feature at δ = ꢀ19.6 (d,
JBH = 90 Hz). Compound 5 is chiral. Consequently it features
the NMR signals of a pair of diastereotopic mesityl substituꢀ
ents at phosphorus and of a pair of diastereotopic –C6F5
groups at boron (for details see the Supporting Information).
1
1
3
=
PH
PH
31
11
…
27
1
Wiberg bond order indices for the B P interaction of 0.014
in the CAO basis and 0.008 in the NAO basis (in contrast to
values near 0.8 in the NAO basis previously described for a
series of related vicinal P/B compounds that show a phosꢀ
phane/borane interaction
17c,18
).
0
1
2
3
4
5
6
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9
0
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2
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4
5
6
7
8
9
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0
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9
0
a
Table 2. Selected bond lengths of the FLP 4 and its reaction
products 5ꢀ8, 12 and 13.
1
1
Table 1: B solidꢀstate NMR parameters of 4 and 8.
δCS/ ppm ± C / MHz
ηQ
ꢃσ/ppm
ησ
C2ꢀC3
C2ꢀP1
C3ꢀB1
1.567(3)
1.636(3)
XꢀP1
ꢀ
ꢀ
YꢀB1
ꢀ
ꢀ
Q
0
.5 ppm
± 5 %
± 0.1a
± 20 ppm
± 0.1a
4
5
1.581(2)
1.577(3)
1.575(4)
1.571(4)
1.876(2)
1.810(2)
1.824(3)
1.813(3)
a
a
a
b
b
7
5.2
4.66
0.22
122.5
0.60
4
8
b
b
b
b
b
f
c
c
c
(
74.0 )
(4.77 )
(0.23 )
(130.3 )
(0.58 )
6
1.633(4) 1.976(3)c 1.499(4)
g
7
1.609(4) 1.907(3)
1.554(4)
2.4/ꢀ0.2
2.15/1.71
0.47/0.38
8b
d
d
b,c
b,c
b,c
h
1.589(5)
1.819(4)
1.621(6) 2.404(2)
1.573(5)
(ꢀ0.9 /
(2.04 /
(0.41 /
ꢀ
ꢀ
b,d
b,d
b,d
i
e
e
e
ꢀ4.1
)
1.89
)
0.44
)
12
1.570(4)
1.569(3)
1.790(3)
1.809(3)
b
1.620(4) 1.744(2)e 1.617(4)
j
a
1
3
1.631(4) 1.646(2)
1.587(4)
:
Extracted by line shape simulation of the MAS NMR specꢀ
trum shown in Figure 2. Euler angles of α=0°, β=15° and γ=45°
for relating the CSA with the EFG tensor were used within the
simulations. : DFTꢀcalculated values in the gasꢀphase (EFG valꢀ
ues were calculated on a B97ꢀD/def2ꢀTZVP (mod.) (for the full
AO basis set see the Supporting Information) and CSA values on
a B3ꢀLYP/def2ꢀTZVP level of theory). :Structure of 8ꢀeq., :
Structure of 8ꢀax.
a
c
d
bond length in Å : X=Y=H. C8(X), O1(Y). S1(X), O1(Y).
f g
e
X=Y=N1. C8ꢀO1 1.376(3) Å, C8ꢀC51 1.517(4) Å. C8ꢀO1
b
h
1.289(3) Å, C8ꢀO2 1.205(3) Å. S1ꢀO1 1.545(3) Å, S1ꢀO2
1.367(4) Å, S1ꢀO2A 1.310(8) Å. N1ꢀO1 1.291(3) Å. N1ꢀO1
1.430(3) Å.
28
i
j
c
d
Table 3. Selected structural parameters of the FLP 4 and its
reaction products 5ꢀ8, 12 and 13.
a
Σ C’ꢀP1ꢀ
Σ C’ꢀB1ꢀ
b
c
Σ ZꢀXꢀY
C
C
4
5
6
7
320.5
344.9
335.7
340.0
340.4
340.1
337.6
b
359.7
335.7
336.2
338.4
339.7
339.5
337.9
ꢀ
ꢀ
d
327.8e
360.0
b)
f
8
b
2
3
312.3
g
1
1
360.0g
360.1
a
c
bond angles in deg. C’/C: C2, C11, C21. C’/C: C3, C31,
+
d
e
f
*
+
+
C41.
C8(X), Z/Y: P1, O1, C51. C8(X), Z/Y: P1, O1, O2.
S1(X), Z/Y: P1, O1, O2 (O2A: 344.1°). N1(X), Z/Y: B1, P1,
O1.
*
+
g
a)
*
*
*
400
300
200
100
0
ꢀ100
ꢀ200
1
1
δ
( B)/ ppm
Scheme 2.
1
1
Figure 2: B Hahn echo MAS NMR spectrum of FLP 4 acquired
at 11.74 T with a spinning frequency of 15.0 kHz (a) and
corresponding line shape simulation (b) based on the NMR
parameters given in Table 1. + marks impurities and * spinning
sidebands.
FLP Reactions of 4 with Small Molecules
Compound 4 is a reactive frustrated Lewis pair. It splits dihyꢀ
drogen under mild conditions. In a typical experiment we exꢀ
posed the FLP 4 to a 2.5 bar H atmosphere in nꢀpentane at ꢀ
2
7
8 °C. Warming to r.t. resulted in the formation of a white
precipitate of the product of heterogeneous splitting of dihyꢀ
drogen, the phosphonium / hydridoborate zwitterion 5 that we
isolated in 67% yield (see Scheme 2).
The H ꢀsplitting product 5 was characterized by Xꢀray diffracꢀ
tion (see Fig. 2 and Table 2). The structure of 5 confirms the
2
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+
ꢁ
formation of a –PHMes2 phosphonium and a –BH(C F )
6
5 2
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
hydridoborate pair of substituents at the FLP´s norbornane
framework. The P–H and B–H vectors point to different direcꢀ
3b
tions. The sum of C–B–C angles confirms the formation of a
tetracoordinate borate center. The PꢂꢂꢂB separation is large, but
the system shows a conformation in the crystal that might inꢀ
2
3
dicate a mesityl / C F πꢀstacking interaction in the periphery
6
5
of the pair of the heteroatom bonded substituents (see Fig. 3,
Table 2 and 3).
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0
1
2
3
4
5
6
7
8
9
0
Figure 4. A view of the molecular structure of the benzaldehyde
addition product 6 (thermal ellipsoids are shown with 30%
probability).
In solution, rotation of the bulky mesityl substituents around
the P–C (aryl) vectors and the bulky –C F substituents around
6
5
the respective B–C (aryl) vectors is frozen at 299 K on the
NMR time scale. Consequently we have observed a total of six
1
separate mesityl CH3 H NMR resonances and four mesityl C–
H proton resonances of the pair of diastereotopic mesityl subꢀ
19
stituents at phosphorus and a total of eight F NMR signals of
the pair of diastereotopic C F groups at boron (the spectra are
Figure 3. A projection of the molecular structure of the
phosphonium hydridoborate zwitterion 5 (thermal ellipsoids are
shown with 30% probability).
6
5
11
depicted in the Supporting Information). The B NMR resoꢀ
nance of 6 occurs at ꢀ0.2 in a typical borate range and the
NMR signal of 6 was found at δ = +38.9.
31
P
Compound 4 undergoes typical FLP reactions with carbonyl
5
compounds under very mild conditions. This was shown by
The open FLP 4 reacts readily with carbon dioxide. We exꢀ
exposure of 4 to benzaldehyde. Mixing of a solution of
PhCHO with a solution of FLP 4 in nꢀpentane at ambient temꢀ
perature resulted in the instantaneous formation of a white
precipitate of the P/B 1,2ꢀaddition product 6 (see Scheme 2). It
was isolated in 85% yield.
posed the P/B pair to CO (3 bar) at ꢀ78 °C and warmed the
2
reaction mixture to r.t. Workup gave the CO addition product
2
7 in 78% yield. The compound was characterized by Xꢀray
diffraction. The structure features the newly formed sixꢀ
membered heterocycle in a distorted halfꢀchair conformation
annulated with the supporting rigid norbornane framework.
The phosphorus Lewis base of 4 was added to the carbonyl
The FLP 4 contains a total of four chirality centers within the
unsymmetrically substituted norbornane framework. These are
of course not independent of each other. The addition of 4 to
the prochiral benzaldehyde molecule generates a fifth carbon
chirality center. Therefore, one might expect the formation of
a mixture of two product diastereoisomers. However, we have
observed that this FLP reaction is highly diastereoselective and
we have only found a single diastereoisomer (6) within the
limits of detection. This could have the phenyl substituent at
the newly formed annulated heterocyclic sixꢀmembered ring
oriented toward the norbornane exoꢀ or endo side. The Xꢀray
crystal structure analysis of compound 6 has revealed that we
have here obtained the exoꢀoriented isomer (see Fig. 4). The
structure of 6 features the newly formed heterocyclic sixꢀ
membered ring system exo / endoꢀannulated with the norꢀ
bornane framework. It shows the newly formed P1–C8
carbon atom of the CO
molecule and the boron Lewis acid
2
8
was attached to a CO oxygen atom. The resulting exocyclic
2
C8–O2 linkage is in the C=O double bond range at 1.205(3) Å
whereas the endocyclic C8–O1 bond is longer (1.289(3) Å).
The coordination geometry at the bound CO carbon atom C8
2
in 7 is trigonal planar with a sum of bond angles of 360.0°
(P1–C8–O2: 116.3(2)°, P1–C8–O1: 119.6°, O1–C8–O2:
124.1(3)°) (see Fig. 4, Tables 2 and 3).
(1.976(3) Å) and B1–O1 (1.499(4) Å) single bonds (C8–O1:
1
.376(3) Å). The sixꢀmembered heterocycle in 6 is formed in a
distorted chair conformation. It has the phenyl substituent at
C8 oriented in an equatorial position in a cisꢀarrangement to
the C1–H vector at the norbornane junction i.e. pointing to the
exoꢀface of the norbornane framework.
Figure 5. Molecular structure of the FLP/CO addition product 7
2
(thermal ellipsoids are shown with 30% probability).
13
The CO addition product 7 features a C NMR carbonyl sigꢀ
2
1
nal at δ = 160.7 with a coupling constant of J = 88.0 Hz.
PC
The corresponding carbonyl stretching frequency observed in
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ꢀ
1
the IR spectrum was found at 1704 cm . Again we find hinꢀ
dered rotation of the pairs of bulky diastereotopic aryl groups
at boron and at phosphorus at the very rigid bicyclic skeleton
of 7. Consequently, we have observed four oꢀF, two pꢀF and
5). The structure shows the chairꢀshaped sixꢀmembered hetꢀ
erocycle annulated with the norbornane framework. The sixꢀ
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
membered ring FLP SO adduct 8 was formed by means of P–
2
S and B–O bond formation (see Fig. 5, Tables 2 and 3). The
coordination geometry at sulfur is pseudotetrahedral with the
sum of the three bond angles 312.2° (P1–S1–O2: 104.37(2)°,
P1–S1–O1: 95.10(1)°, O1–S1–O2: 112.8(2)°). In the FLP /
19
four mꢀF F NMR resonances of compound 7 in solution at
13 K and a total of six mesityl CH3 H NMR signals and four
CHꢀ mesityl resonances. The remaining NMR active heteroaꢀ
1
2
toms of the FLP / CO adduct 7 give rise to resonances at δ =
SO adduct 8b the exocyclic oxygen (S1–O2: 1.367(4) Å) is
occupying a pseudoꢀequatorial site at the newly formed sixꢀ
membered ring.
2
2
1
1
31
1
6.3 ( B) and δ = 13.7 ( P), respectively.
We had recently shown that FLPs can also react with sulfur
dioxide. We had isolated and described a small series of [P]–
The SO activation product 8 was additionally investigated by
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
2
9
S(O)–O–[B] type addition products. These compounds feaꢀ
solidꢀstate NMR spectroscopy for a more thorough characteriꢀ
zation of the two diastereomers formed in this reaction. The
tured a strongly nonꢀplanar coordination geometry at sulfur
3
1
1
which makes the sulfur atoms in these FLP / SO addition
P{ H} CPMAS NMR spectrum (see Figure 7, bottom) reꢀ
2
products chiral centers. The FLP 4 was treated with SO gas (2
veals two resonances at 57.8 and 56.6 ppm in an intensity ratio
of 3:2 (see the Supporting Information) most probably resultꢀ
ing from the two [B]ꢀOꢀS(O)ꢀ[P] epimers. In close agreement
2
bar) for five minutes at room temperature in nꢀpentane. During
this time a white precipitation of the SO adduct 8 was formed
2
11
and isolated as a colourless solid (see Scheme 3).
with these findings, also two B resonances are found in a
11 1
B{ H} MAS NMR spectrum (see Figure 7, top) with only
slightly differing quadrupolar coupling parameters (see Table
1). These parameters are in close agreement with the DFTꢀ
calculated ones for the [B]ꢀOꢀS(O)ꢀ[P] epimers.
Scheme 3.
We expected the formation of a pair of epimeric SO addition
2
products that were distinguished only by their relative configuꢀ
ration at the chiral sulfur atom. The two possible diastereoiꢀ
somers were then distinguished as having the relative configuꢀ
S
ration of racꢀ(1R,2S,3R,4S, R) (i.e. 8a) and racꢀ
S
(1R,2S,3R,4S, S) (i.e. 8b). Indeed we have found that the
obtained product contained a mixture of two diastereoisomers
31
in a 5:2 molar ratio. They are characterized in solution by
P
NMR resonances at δ = 59.6 (major) and δ = 53.7 (minor isoꢀ
mer), respectively. For the major isomer of 8 we have moniꢀ
1
9
tored a set of four oꢀC6F
5
F NMR signals, two pꢀC F and
6 5
some overlapping mꢀC F resonances. The minor isomer of 8
6
5
features a similar series of four oꢀC F and two pꢀC F signals.
6
5
6 5
11
1
Figure 7: Top: B{ H} MAS NMR spectrum of 8 acquired at
.05 T with a rotation frequency of 14.0 kHz (a) and
7
31
1
corresponding line shape simulation (b). Bottom: P{ H}
CPMAS NMR spectrum of 8 acquired at 7.05 T with a spinning
frequency of 10.0 kHz (a) and line shape simulation (b).
For further proving the hypothesis of the formation of epiꢀ
1
31
11
mers, we performed { H}→ P{ B} crossꢀpolarizationꢀ
rotational echo adiabatic passage double resonance (CPꢀ
REAPDOR) experiments (see Figure 8a) which allow a BꢂꢂꢂP
distance determination through recoupling of the heteronucleꢀ
Figure 6. Molecular structure of the FLP/SO addition product 8b
2
(thermal ellipsoids are shown with 30% probability).
2
9
We obtained single crystals of one of the epimers of 8. It was
ar BꢂꢂꢂP dipolar interaction under MAS conditions As illusꢀ
trated by Figure 8a the two phosphorus moieties show very
S
characterized as the racꢀ(1R,2S,3R,4S, S) isomer 8b (see Fig.
ACS Paragon Plus Environment

Journal of the American Chemical Society
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similar REAPDOR dephasing curves close to the numerical
compound 10 is chemically related to the large compound
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
simulation on the basis of the crystallographic BꢂꢂꢂP distance
of 3.54 Å and experimental quadrupolar coupling parameters.
These experiments suggest that both epimers have the same
BꢂꢂꢂP distance within experimental error, while the slight difꢀ
ferences observed between the two REAPDOR curves arise
class of the aminoxyl radicals. Compound 10 is a persistent
radical. It is the parent compound of the new class of FLPꢀNO
aminoxyl radicals (see Scheme 4). The FLP 1 also adds NO.
The resulting FLPꢀNO nitroxide product (11) shows a variety
7
of typical features of persistent aminoxyl radical species.
1
1
from the difference in the corresponding BꢀC values and/or
Q
experimental uncertainties. These results are confirmed by the
1
11
31
Scheme 4
{
(
H}→ B{ P} CPꢀrotational echo double resonance
17,30
REDOR)
curve shown in Figure 8b. The clear oscillatory
behaviour signifies the presence of isolated twoꢀspin systems
with nearly identical, extremely wellꢀdefined internuclear disꢀ
tances for both epimers present.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00
The open FLP 4 reacts rapidly with NO in nꢀpentane solution
in the temperature range between ꢀ78 °C to r.t. A solid formed
quickly upon exposure of the reactive FLP to a NO atmosꢀ
phere at low temperature and we isolated the FLP N,Nꢀ
addition product 12 as a pale turquoise solid in 87% yield.
Single crystals of 12 suitable for Xꢀray structure analysis (see
Fig. 6, Tables 2 and 3) were obtained from dichloromethane /
nꢀpentane at ꢀ35 °C by the diffusion method.
0
1
2
3
4
NT / ms
R
1
31
11
Figure 8a: { H}→ P{ B} CPꢀREAPDOR experiment of 8
performed at 7.05 T with a spinning frequency of 12.0 kHz. The
dephasing curves for the resonances at 57.8 ppm (filled squares)
and 56.6 ppm (filled circles) are shown. The SIMPSON
simulations are based on the crystallographic BꢂꢂꢂP distance and
quadrupolar coupling parameters of C = 1.71 MHz, η = 0.38
Scheme 5.
B(C F )
6
5 2
B(C F )
NO
r.t.
6
5
Q
Q
N
(
solid curve) and C = 2.15 MHz, η = 0.47 (dashed curve).
Mes2P
Q
Q
PMes2
O
4
12
1
0
0
.0
.8
.6
1/2
B(C F )
6
5
N
Mes P
2
O H
ꢀ1/2
13
0.4
0
0
.2
.0
The Xꢀray crystal structure analysis of compound 12 has conꢀ
firmed that the phosphorus Lewis base and the boron Lewis
acid have both added to the nitrogen atom of the nitric oxide
reagent (bond lengths; P1–N1: 1.744 Å, B1–N1: 1.617(4) Å).
The resulting fiveꢀmembered heterocycle is found annulated to
the norbornane framework in a 2ꢀendo (C2–P1: 1.790(3) Å),
3ꢀexo (C3–B1: 1.620(4) Å) fashion. The nitrogen atom in the
aminoxyl radical 12 features a trigonalꢀplanar coordination
geometry with a sum of its three bond angles being 360.0°
with individual angles of 126.1(2)° (O1–N1–B1), 118.9(2)°
(O1–N1–P1) and 115.0(2)° (B1–N1–P1). The B1–N1 bond
length (1.617(4) Å) is unexceptional. The P1–N1 bond is very
long at 1.744(2) Å), clearly being in a phosphorusꢀnitrogen
single bond range. The O1–N1 bond is rather short at 1.291(3)
Å which indicates a considerable delocalization of the unꢀ
paired electron between the aminoxyl oxygen and nitrogen
0
2
4
6
8
10
NT / ms
R
1
11
31
Figure 8b: { H}→ B{ P} CPꢀREDOR experiment of
8
performed at 7.05 T with a spinning frequency of 12.0 kHz and
1
H decoupling during the evolution and data acquisition time. The
SIMPSON simulation (straight curve) is based on the
crystallographic BꢂꢂꢂP distance of 3.54 Å.
Reaction with Nitric Oxide
We had recently shown that the ethylene bridged P/B FLP 9
7
reacted under mild conditions with nitric oxide (NO). The
reaction took place by N,Nꢀaddition of the P/B pair to yield
the five membered heterocyclic product 10. The paramagnetic
7
atoms.
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1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 11: UVꢀvis spectrum of 12 in fluorobenzene at room
temperature.
Figure 9. Molecular structure of the persistent FLPꢀNO aminoxyl
radical 12 (thermal ellipsoids are shown with 30% probability).
Additionally, the radical 12 represents the first example for
this class of compounds to be characterized by solidꢀstate
NMR spectroscopy. Since stateꢀofꢀtheꢀart liquidꢀstate NMR
experiments suffer from the presence of strongly pronounced
paramagnetic relaxation enhancement effects between the free
The EPR spectrum of 12 in fluorobenzene at room temperaꢀ
ture displays a multiꢀline pattern centered at g = 2.0078. As
previously seen in other P/B FLPꢀNO adducts, coupling to the
14
14
31
31
3
1
N [A( N) = 19.8 MHz], P [A( P) = 49.7 MHz], and
electron and the nuclei leading in a lot of cases to undetectaꢀ
ble, extremely broad resonances, this effect is often reduced in
the solidꢀstate, owing to the absence of molecular reorientaꢀ
1
1
10
11
B/ B [A( B) = 9.5 MHz] nuclei is observed. While the
magnitudes of these hyperfine coupling constants are almost
14
1
identical to those in the related P/B FLPꢀNO adduct 11 [A( N)
tion dynamics. Figure 12 shows the H MAS NMR spectra of
31
11
= 20.4 MHz, A( P) = 50.5 MHz, A( B) = 8.9 MHz], a sharper
EPR spectrum is seen for 12 that possesses more fine strucꢀ
ture, perhaps due to the extremely rigid nature of the tricyclic
1
2 and 13. The electronꢀspinꢀcarrying molecule 12 shows
strongly highꢀfrequency shifted resonances at chemical shift
values of about 20 and 10 ppm which have their origin most
probably in pseudoꢀscalar hyperfine interactions. Line shape
simulation and integration reveals that three resonances of the
norbornylꢀbackbone are shifted to higher frequencies. With
the help of DFT calculations of Mulliken spinꢀdensitiy populaꢀ
tions based on the TPSSꢀD3/def2ꢀTZVP KohnꢀSham determiꢀ
nants we assign the resonances at around 10 ppm to H2 and
H3 (attached to C2 and C3, respectively), while a resonance at
about 20 ppm most probably results from the hydrogen atom
attached to C5 (H5B). The crystal structure of 12 suggests that
this H atom has a rather close intermolecular contact with the
unpaired electron density situated at the terminal O atom of
the nitroxide moiety and DFT calculations of the Mulliken
spin density populations for a dimer of 12 (thereby taking into
account also intermolecular interactions) yield also significant
spin populations for this particular proton species (see the
Supporting Information).
1
2. Satisfactory simulation required consideration of the four
1
9
1
9
oꢀ F nuclei of the BꢀC F groups (A( F) = 4.0 MHz) as well
as the two H nuclei within the P/BꢀNO fiveꢀmembered ring
6
5
1
1
[
A( H) = 3.3 MHz].
Figure 10: Xꢀband EPR spectrum and simulation of 12 in fluoroꢀ
benzene at room temperature.
+
UVꢀvis spectroscopy of 12 in fluorobenzene at room temperaꢀ
b)
ture reveals an absorbance centered at λ = 682 nm (ε = 6.8
max
ꢀ
1
ꢀ1
M cm ). Vibrational fine structure is present with an average
spacing of 1093(36) cm that corresponds to the NꢀO stretch
ꢀ1
+
a2)
in the electronic excited state of 12 expected to possess a lowꢀ
7
er NꢀO bond order. This compares well to the value of
ꢀ1
1
097(24) cm for the vibronic fine structure seen in the UVꢀ
ꢀ1
ꢀ1
vis spectrum of 11 [λmax = 708 nm (ε = 5.0 M cm )].
+
a1)
3
5
30
25
20
15
10
5
0
ꢀ5
ꢀ10
ꢀ15
ꢀ20
δ/ ppm
1
Figure 12: H Hahn echo MAS NMR spectra of 12 (a1) and 13
b) acquired at 11.71 T with a rotation frequency of 28.0 kHz. The
line shape simulation for the spectrum of 12 is additionally shown
a2).
(
(
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1
1
31
It was also possible to record B and P MASꢀNMR spectra
of the solid material containing 12 (see the Supporting Inforꢀ
mation). The spectral parameters obtained from these spectra
closely resemble those of 13, however, and are also inconꢀ
Compound 13 was characterized by Xꢀray diffraction (see Fig.
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
14 and Tables 2 and 3). The structure is composed of the fiveꢀ
membered heterocyclic ring that is 2ꢀendo, 3ꢀexo annulated
with the supporting norbornane framework. The system now
contains an [N]O–H moiety. Its formation has resulted in a
marked elongation of the N1–O1 bond length from 1.15 Å in
1
1
31
sistent with the sizeable B and P magnetic hyperfine couꢀ
pling constants extracted from the liquid EPR spectra. Furꢀ
thermore, an absolute quantification experiment indicated that
the P nuclei detected correspond only to 2ꢀ3% of the total
number of spins present in these samples. Therefore, we conꢀ
clude that the spectra observed here do not belong to moleꢀ
cules of 12 but rather to molecules of 13 forming a solid soluꢀ
tion with the radical species.
34
NO itself, and 1.291(3) Å for the FLPꢀNO radical 12 to
1.430(3) Å in 13 which is a typical value of a FLPꢀNOH comꢀ
pound. The N1–B1 bond in 13 (1.587(4) Å) has become
slightly shorter than in the radical. The P1–N1 bond length in
13 is found at 1.646(2) Å. This is by ca. 0.1 Å shorter than the
corresponding P–N linkage in the FLPꢀNO radical 12. This
probably indicates some participation of a mesomeric phosꢀ
31
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
For additionally proving the radical character of 12 in the solid
state, the magnetic susceptibility was measured (for more deꢀ
tails see the Supporting Information). As typical for radicals
the compound exhibits CurieꢀWeiss behaviour and the effecꢀ
35
phinimine type structure (13B, see Scheme 6). In contrast
the FLPꢀNO radical seems to be best described by a σꢀ
structure (12A) featuring single bonds between the heteroaꢀ
toms inside the ring.
tive magnet moment was determined to 1.60(1) ꢄ (the slight
B
deviation from the theoretically expected spinꢀonly value of
1
.73 for one unpaired electron is attributed to a small amount
of diamagnetic impurities).
Many persistent aminoxyl radicals undergo hydrogen atom
3
2
abstraction (HAA) reactions, and so does our FLPꢀNO niꢀ
troxide radical 12. Exposure of a benzene solution of the paraꢀ
magnetic compound 12 to 1,4ꢀcyclohexadiene at r.t. resulted
in a rapid loss of the characteristic turquoise colour. The diaꢀ
magnetic compound 13 was obtained as a colourless crystalꢀ
3
1
line solid in 93% yield. Compound 13 shows a P NMR resoꢀ
1
1
nance at δ = 41.4 and a B NMR signal at δ = ꢀ6.4. The
1
[
N]OH H NMR resonance is found at δ = 4.66. The chiral
1
compound 13 shows the typical set of six separate CH3
H
NMR signals and the separate set of four separate mesityl CH
resonances of the pair of diastereotopic mesityl substituents at
1
phosphorus in addition to the typical H NMR signals of the
Figure 14. Molecular structure of the compound 13 (thermal
ellipsoids are shown with 30% probability).
19
norbornane derived residue. The F NMR spectrum of the
FLPꢀNOH compound 13 shows the signals of a pair of diaꢀ
stereotopic C F groups at boron. At 299 K the rotation around
Scheme 6.
6
5
the B–C vectors are “frozen” on the NMR time scale. This
19
leads to the observation of a total of four oꢀC6F5 F NMR
signals. Three of these are in the usual chemical shift range
(ca. δ = ꢀ130 to δ = ꢀ133) whereas one oꢀC F signal is shifted
6
5
markedly to a more negative δꢀvalue (δ = ꢀ144) (see Fig. 13).
We assume that this indicates the presence of a [N]O–HꢂꢂꢂF–
3
3
C(aryl) interaction. Consequently, we monitor JHF coupling
1
in the H NMR spectrum of 13.
Interestingly we find the [N]O–H group in the FLPꢀNOH
compound 13 oriented toward the C32–F32 vector of a C6F5
group at boron (O1–H01ꢂꢂꢂF32: 2.13 Å). This may serve as a
further indication for the occurrence of a weak O–HꢂꢂꢂF–C
contact in 13 (see above).
We also carried out two competition experiments. We treated
a mixture of the parent vicinal P/B FLP 9 and our new FLP 4
with NO (ca. 0.5 molar equiv.). Subsequent treatment with
1
9
1
,4ꢀhexadiene converted the resulting FLPꢀNO radicals to
Figure 13. F NMR (564 MHz, 253K, CD Cl ) spectrum of
2
2
1
compound 13 with H NMR (600 MHz, 253K, CD Cl ) and
H{ F} NMR (selectively decoupled F at δ = ꢀ144) spectra of
the [N]O H resonance featuring a [N]OHꢂꢂꢂF–C(aryl) interaction.
their diamagnetic products. In this experiment the FLP 4 reactꢀ
ed ca. 3.6 times faster than 9. However, the relative reactivity
seems to be strongly reagent dependent. In a similar competiꢀ
tion experiment of the 9/4 mixture with benzaldehyde it was
2
2
1
19
19
1
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Page 9 of 16
Journal of the American Chemical Society
the FLP 9 that reacted preferentially by a factor of 2.3 (for
details see the Supporting Information).
slow retroꢀhydroboration of 4 might generate a small quantity
of 3 and HB(C F ) in an endothermic equilibrium situation
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
6
5 2
from which the borane was then rapidly trapped by its hydroꢀ
boration of ethylene. The resulting ethylꢀB(C F ) product then
Reaction with Ethylene
6 5 2
can be considered forming a new intermolecular frustrated
The FLP 4 appears quite robust in all these reactions. Howevꢀ
er, we eventually found some evidence that its formation by
the hydroboration reaction might be reversible under some
suitable conditions. This was found when we treated 4 with
ethylene. For this purpose we prepared the FLP 4 in situ by
treatment of dimesitylꢀ2ꢀnorbornenylphosphane (3) with
HB(C F ) in nꢀpentane for 30 min. at room temperature. The
36
Lewis pair with 3, which then eventually traps a further
equivalent of ethylene in a typical FLP olefin addition reaction
to form 14. This hypothetical reaction pathway would explain
the formation of the observed product straightforwardly but it
needs further experimental evidence to be confirmed.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
6
5 2
Conclusions
resulting yellow solution of the FLP 4 was then without any
workup subjected to an ethylene atmosphere (3 bar) at r.t. The
It is likely that many intermolecular frustrated Lewis pairs
feature weak covalent bonding interactions between the Lewis
acid and Lewis base components that enable them to react
reaction between 4 and CH =CH was apparently slow, it reꢀ
2
2
quired ca. 2 d for the typical yellow colour to disappear. Durꢀ
ing this time colourless crystals of a product (14) had formed
that were isolated in 68% yield (see Scheme 7).
10,11,17,37
with added small molecules.
Those LA / LB interacꢀ
tions seem to effectively eliminate the “termolecularity trap”
of such threeꢀcomponentꢀreactions. A variety of intramolecuꢀ
lar FLPs were also shown to exhibit interactions between their
Lewis acid and Lewis base components. For several examples
these interactions were quantified either by experimental work
The Xꢀray crystal structure analysis (see Fig. 15) revealed that
two equivalents of ethylene had been taken up. The compound
shows a norbornene framework with a phosphorus substituent
at C2 (C2–C3: 1.340(4) Å, C2–P1: 1.782(3) Å). The boron
atom has become removed from C3. It now has an ethyl subꢀ
stituent attached to it (B1–C51: 1.637(5) Å) and it is connectꢀ
(
e.g. liquid and solidꢀstate NMR) or by quantum chemical
12,16,17,18,20
calculations.
There were only a few examples of
geminal or vicinal FLPs known where any direct LA / LB inꢀ
teraction was absent mainly in cases of very weak Lewis base
components, having e.g. strongly electron withdrawing C F
ed with the –PMes substituent at the norbornene framework
2
by an ethylene bridge.
6
5
13,14,15
substituents at phosphorus.
For vicinal FLPs having
Scheme 7.
“normal” substituents at the Lewis base component and using
the ubiquitous –B(C F ) Lewis acid site, to the best of our
6
5 2
knowledge, most published examples feature some degree of
LA / LB interaction. This posed the question of whether such
weak LA / LB interaction might actually be necessary in order
to observe typical FLP reactions and reaction modes toward
small molecule binding or activation.
The properties and the observed reactions of FLP 4 described
in this study indicate that such LA / LB interaction seems not
to be necessary. There is good indication from the spectroꢀ
scopic features, including the solid state NMR experiments
and structural properties that 4 is a rare example of a nonꢀ
interacting intramolecular frustrated Lewis pair. Nevertheless,
it effects rapid heterolytic cleavage of dihydrogen and it adds
rapidly to CO , to benzaldehyde, to SO and even to NO. This
2
2
encompasses almost the full range of known small molecule
reactions of FLPs. This behaviour indicates that intramolecular
frustrated Lewis pairs probably activate themselves (at least in
many cases) by cleaving their moderately strong or weak interꢀ
actions. The open forms, available from this preceding equiꢀ
librium must probably be considered the active species in
many of such FLP reactions. Future design efforts of new
FLPs may take this effect into account in order to generate
highly active new main group systems of this type for adꢀ
vanced small molecule activation.
Experimental Section
General Procedures. All syntheses involving airꢀ and moisꢀ
ture sensitive compounds were carried out using standard
Schlenkꢀtype glassware (or in a glove box) under an atmosꢀ
phere of argon. Solvents were dried with the procedure acꢀ
Figure 15. A projection of the molecular structure of compound
1
4 (thermal ellipsoids are shown with 30% probability).
38
Apparently, the P/B addition reaction of the FLP 4 to ethylene
is sufficiently slow to allow for the observation of an alternaꢀ
tive competing pathway. The formation of the product 14 may
be rationalized by the following hypothetical reaction course:
cording to Grubbs or were distilled from appropriate drying
agents and stored under an argon atmosphere. NMR spectra
1
13
were recorded on a Bruker AV 300 ( H: 300 MHz, C:
31
11
19
76 MHz, P: 122 MHz, B: 96 MHz, F: 282 MHz), a Variꢀ
an Inova 500 ( H: 500 MHz, C: 126 MHz, F: 470 MHz,
1
13
19
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Journal of the American Chemical Society
Page 10 of 16
1
1
1
31
B:160 MHz, P: 202 MHz) and on a Varian UnityPlus 600
Dimesitylnorbornenylphosphane (25 mg, 0.069 mmol) and
HB(C F ) (24 mg, 0.069 mmol) were weighed together and
13
19
11
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
( H: 600 MHz, C: 151 MHz, F: 564 MHz, B: 192 MHz,
6
5 2
3
1
1
13
P: 243 MHz). H NMR and C NMR: chemical shifts
given relative to TMS and referenced to the solvent signal.
NMR: chemical shifts are given relative to CFCl (external
δ
are
F
dissolved in CD Cl (0.7 mL) to get a yellow solution. NMR
2 2
1
9
data was collected after 30 minutes which showed the forꢀ
1
mation of compound 4, admixed with ca. 5% (detected in H
δ
3
1
1
NMR spectrum) of a compound not identified yet. The solvent
was removed under vacuum to get a yellow solid (47 mg, 96%
yield). Crystals of the compound 4 suitable for Xꢀray crystal
structure analysis were obtained by slow evaporation of its
reference), B NMR: chemical shifts
δ
are given relative to
BF ꢂEt O (external reference), P NMR: chemical shifts are
given relative to H PO (85% in D O) (external reference).
3
1
δ
3
2
3
4
2
NMR assignments were supported by additional 2D NMR
experiments. IR spectra were recorded on a Varian 3100 FTꢀ
IR (Excalibur Series). HRMS was recorded on GTC Waters
Micromass (Manchester, UK). XꢀRay crystal structure analꢀ
yses. Data sets were collected with a Nonius KappaCCD difꢀ
fractometer. Programs used: data collection, COLLECT; data
reduction DenzoꢀSMN; absorption correction, Denzo;
structure so43lution SHELXSꢀ97;
SHELXLꢀ97 and graphics, XP (BrukerAXS, 2000). Therꢀ
1
solution in nꢀpentane at ꢀ35 °C. H NMR (500 MHz, CD Cl ,
2
=
2
2
4
A
4
99 K): δ = 6.75 (d, J = 2.6 Hz, 2H, mꢀMes ), 6.52 (d, J
PH PH
B
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
2.3 Hz, 2H, mꢀMes ), 4.06 (br m, 1H, PCH), 2.76/1.50 (each
m, each 1H, Hꢀ6), 2.72 (br m, 1H, Hꢀ1), 2.37 (br m, 1H, Hꢀ4),
MesA,B
3
MesA
39
2.34 (br s, 12H, oꢀCH3
), 2.19 (s, 3H pꢀCH3
PH HH
), 2.03 (s,
MesB
3
40
41
3H, pꢀCH3 ), 2.01 (dd, J = 12.9 Hz, J = 7.9 Hz, 1H,
42
BCH), 1.69/1.52 (each m, each 1H, Hꢀ5), 1.42/1.26 (each m,
13 1
structure refinement
each 1H, Hꢀ7), C{ H} NMR (126 MHz, CD Cl , 299 K): δ =
2
2
3
B
A
144.9 (d, J = 15.6 Hz, oꢀMes ), n.o. (oꢀMes ), 139.4 (d,
JPC = 1.5 Hz, pꢀMes ), 137.2 (d, J = 1.0 Hz, pꢀMes ),
PC
mals ellipsoids are shown with 30% probability, Rꢀvalues are
given for observed reflections, and wR values are given for
all reflections.
4
B
4
A
2
PC
1
A
1
1
33.1 (d, J = 33.4 Hz, iꢀMes ), 131.9 (d, J = 20.9 Hz, iꢀ
PC PC
B A 3 B
Mes ), 130.6 (br, mꢀMes ), 129.4 (d, J = 4.5 Hz, mꢀMes ),
PC
Synthesis of the dimesitylnorbornenylphosphane (3)
2
2
4
9.3 (br d, J = 17.5 Hz, BCH), 42.1 (d, J = 21.6 Hz, Cꢀ
PC PC
3 3
t
BuOK (2.02 g, 18.00 mmol) was weighed in a well dried
1), 41.3 (d, J = 2.6 Hz, Cꢀ4), 40.7 (d, J = 5.0 Hz, Cꢀ7),
PC PC
1 3
Schlenk flask, dissolved in THF (20.0 mL) and cooled to ꢀ78
°
(
39.5 (d, J = 18.7 Hz, PCH), 32.9 (Cꢀ5), 24.4 (d, J = 31.8
PC PC
3 3
C. A precooled solution (ꢀ78 °C) of bicyclo[2.2.1]heptꢀ2ꢀene
5.15 g, 54.69 mmol) in THF (10.0 mL) was transferred to the
Hz, Cꢀ6), 23.06 (d, J = 15.9), 23.01 (d, J = 13.5) (oꢀ
PC PC
MesA MesB
MesA,B
11
CH3
), 20.7 (pꢀCH3
), 20.6 (pꢀCH3 ). [C6F5 not
t
1
precooled solution of BuOK via a syringe. nꢀBuLi (1.6 M,
1.2 mL, 17.92 mmol) was added slowly to the above reaction
listed]. B{ H} NMR (192 MHz, CD Cl , 99 K): δ = 75.0 (ν
2
2
1/2
31
1
1
≈ 1500 Hz). P{ H} NMR (202 MHz, CD Cl , 299 K): δ = ꢀ
2 2
19
mixture at ꢀ78°C. The reaction mixture was stirred for 30 min.
at ꢀ78 °C then warmed up to ꢀ60 °C and the temperature was
maintained between ꢀ60 °C and ꢀ50 °C for 90 min. The reacꢀ
tion mixture was cooled again to ꢀ78 °C and a precooled (ꢀ60
21.8 (ν1/2 ≈ 2 Hz). F NMR (564 MHz, CD Cl , 299 K): δ = ꢀ
2 2
3
130.3 (m, 2F, oꢀC F ), ꢀ151.2 (t, J = 20.1 Hz, 1F, pꢀC F ), ꢀ
6
5
FF
6 5
+
162.1 (m, 4F, mꢀC F ). HRMS: calc. for C H PBF [M+H] :
6
5
37 33
10
ꢀ
1
709.22478. Found: 709.22337. IR (KBr): ύ/cm = 2936 (s),
2863 (s), 2362 (w), 1647 (s), 1604 (w), 1521 (s), 1474 (vs). Xꢀ
ray crystal structure analysis of compound 4: formula
C H BF P, M = 708.41, colourless crystal, 0.40 x 0.25 x
°
C) solution of Mes PCl (6.53 g, 21.42 mmol) in THF (10 mL)
2
was added to it. The reaction mixture was allowed to warm to
r.t. and the solvent was evaporated under vacuum to get a
brown residue. The residue was dissolved in nꢀpentane (100
mL) and filtered over Celite®. The filtrate was concentrated
under vacuum to get a brown oily residue. The residue was
dissolved in a minimum amount of nꢀpentane, loaded onto an
alumina column (basic, activity III) and eluted with nꢀpentane
which gave the compound 3 as colourless oil in impure form.
Further chromatography on a silica gel column (CH Cl / nꢀ
pentane, 3:7) gave the compound 3 in pure form (R = 0.31,
1.011 g, 13 % yield). H NMR (500 MHz, CD Cl , 299 K): δ =
6.84 (s, 2H, mꢀMes ), 6.82 (s, 2H, mꢀMes ), 5.45 (m, 1H, Hꢀ
37
32
10
0.13 mm, a = 20.4305(4), b = 14.7348(5), c = 11.0389(3) Å, β
3
ꢀ3
= 90.088(2) °, V = 3323.14(16) Å , ρ = 1.416 gcm , ꢄ =
calc
ꢀ1
1.474 mm , empirical absorption correction (0.590 ≤ T ≤
0.831), Z = 4, monoclinic, space group P2 /c (No. 14), λ =
1
1.54178 Å, T = 223(2) K, ω and φ scans, 16319 reflections
ꢀ1
collected (±h, ±k, ±l), [(sinθ)/λ] = 0.60 Å , 5559 independent
2
2
(Rint = 0.032) and 5162 observed reflections [I>2σ(I)], 448
2
F
refined parameters, R = 0.045, wR = 0.119, max. (min.) reꢀ
1
ꢀ
3
2
2
sidual electron density 0.25 (ꢀ0.24) e.Å , hydrogen atoms
were calculated and refined as riding atoms.
A
B
3
CH3
), 3.13 (br s, 1H, Hꢀ1), 2.82 (br s, 1H, Hꢀ4), 2.35 (s, 6H, oꢀ
MesB
), 2.26 (s, 6H, pꢀCH3
MesA,B
), 2.22 (s, 6H, oꢀCH3
MesA
Synthesis of compound 5-H
),
HB(C F ) (80 mg, 0.231 mmol) and the norbornenylꢀ
1
1
(
.73/0.97 (each m, each 1H, Hꢀ5), 1.71/1.22 (each m, each
H, Hꢀ6), 1.57/1.31 (each br m, each 1H, Hꢀ7). C{ H} NMR
126 MHz, CD Cl , 299 K): δ = 144.0 (d, J = 12.6 Hz, Cꢀ2),
43.8 (d, J = 14.7 Hz, oꢀMes ), 141.8 (d, J = 15.2 Hz, oꢀ
PC PC
B 2
6 5 2
1
3
1
phosphane 3 (82 mg, 0.226 mmol) were weighed together,
dissolved in nꢀpentane (10 mL) and stirred for 30 min. at r.t. to
get yellow solution of compound 4. The solution was degassed
1
2
2
PC
2
A
2
1
by freezeꢀpumpꢀthaw cycles (×2) and cooled to ꢀ78 °C. H gas
Mes ), 139.5 (d,
CH3
J
= 3.1 Hz, Cꢀ3), 138.8, 137.4 (pꢀ
2
PC
MesA,B
1
B
1
was pressed (2.5 bar) over the solution and allowed the soluꢀ
tion to warm to r.t. The solution was stirred at r.t. for further
10 min. Formation of a colourless precipitate was observed.
The solvent was decanted off, the residue washed with nꢀ
pentane (3 mL) and dried in vacuum to get a slightly yellow
solid. The compound was crystallised from CH Cl to get
), 132.1 (d, J = 20.0 Hz, iꢀMes ), 130.5 (d, J
=
PC
PC
A
3
B
8
.2 Hz, iꢀMes ), 130.1 (d, J = 2.7 Hz, mꢀMes ), 129.8 (d,
JPC = 4.7 Hz, mꢀMes ), 48.4 (d, J = 30.8 Hz, Cꢀ1), 45.9 (d,
JPC = 2.0 Hz, Cꢀ7), 43.6 (d, J = 2.4 Hz, Cꢀ4), 27.8 (d, J
PC
3
A
2
PC
3
3
4
PC
PC
3
= 2.0 Hz, Cꢀ5), 25.6 (Cꢀ6), 22.8 (d, JPC = 13.5 Hz, oꢀ
CH3 ), 22.3 (d,
CH3
2
H] : 363.22361. Found: 363.22233. IR (KBr): ύ/cm = 3023
(
(
MesB
3
MesA
J
= 16.6 Hz, oꢀCH
), 21.1 (pꢀ
2
2
PC
MesB 31
3
MesA
1
compound 5-H as thin colourless needles (108 mg, 67 %
), 20.9 (pꢀCH3 ). P{ H} NMR (202 MHz, CD Cl ,
2 2
yield). The obtained crystals were suitable for Xꢀray crystal
99 K): δ = ꢀ37.7 (ν ≈ 2 Hz). HRMS: calc. for C H P [Mꢀ
1/2 25 32
+ ꢀ1
1
structure analysis. H NMR (600 MHz, CD Cl , 299 K): δ =
2
2
1
3
7
2
2
.22 (dd, J = 466.9 Hz, J = 9.2 Hz, 1H, HP), 7.04 (br,
w), 2961 (s), 2862 (s), 2360 (w), 1602 (w), 1549 (w), 1447
s).
PH PH
H), 6.96 (br, 1H), 6.81 (br, 1H) (mꢀMes), 3.20 (br, 1H, PCH),
.75, 2.26 (each br, each 1H, Hꢀ1,4), 2.10/1.28, 1.74/1.42,
Synthesis of compound 4
ACS Paragon Plus Environment

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Journal of the American Chemical Society
A
1
2
.42/1.23 (each m, each 1H, CH ), 2.58 (very br), 2.50 (br),
299 K): δ = 7.05 (br m, 1H, mꢀMes ), 7.04 (m, 1H, pꢀPh), 7.00
2
Mes
B
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
(m, 2H, oꢀPh), 6.99 (s, 1H, mꢀMes ), 6.92 (m, 2H, mꢀPh), 6.84
.41 (very br), 2.26 (br) (Σ18H, oꢀCH ), 2.32, 2.29 (each s,
3
Mes
3
A
2
each 3H, pꢀCH ), 1.86 (br d, J = 27.6 Hz, 1H, BCH).
(br s, 1H, m´ꢀMes ), 6.46 (d, JPH = 13.5 Hz, CHO), 6.20 (br s,
1H, m´ꢀMes ), 3.63 (m, 1H, PCH), 2.90 (s, 3H, oꢀCH
3
PH
1
3
1
B
MesB
C{ H} NMR (151 MHz, 299 K, CD Cl ): δ = 145.6, 145.4
3
),
2
2
MesA
(pꢀMes), n.o. (oꢀMes), 132.4, 132.0, 131.8, 131.4 (each br, mꢀ
Mes), 114.8 (d, J = 69.8 Hz), 113.7 (d, J = 79.2 Hz) (iꢀ
Mes), 43.6 (d, JPC = 5.9 Hz), 41.6 (d, J = 2.2 Hz) (Cꢀ1,4),
4
1
2.88 (s, 3H, oꢀCH
3
), 2.80 (br s, 1H, Hꢀ1), 2.43 (br s, 1H,
1
1
MesA MesB
Hꢀ4), 2.30 (s, 3H, pꢀCH
), 2.18 (s, 3H, pꢀCH
), 1.91 (s,
), 1.64 (dd, JPH = 23.9 Hz, JHH = 11.9 Hz,
BCH), 1.39/1.01 (each m, each 1H, Hꢀ5), 1.13/0.78 (each m,
PC
PC
3
3
2
MesA
3
3
3H, o´ꢀCH
PC
3
1
3.5 (br, BCH), 42.9 (d, J = 35.0 Hz, PCH), 38.9 (d, JPC =
PC
MesB
5.0 Hz), 32.7, 25.4 (d, J = 10.5 Hz) (CH ), 23.0, 22.5 (each
each 1H, Hꢀ7), 0.95 (s, 3H, o´ꢀCH
3
), 1.09/0.75 (each m,
each 1H, Hꢀ6). C{ H} NMR (126 MHz, CD Cl , 299 K): δ =
144.6 (d, JPC = 4.4 Hz, o´ꢀMes ), 143.8 (d, JPC = 3.0 Hz, pꢀ
PC
2
Mes
Mes
11
13
1
br, oꢀCH3 ), 21.3, 21.1 (pꢀCH3 ), [C F not listed].
B
2
2
6
5
1
2
A
4
NMR (192 MHz, CD Cl , 299 K): δ = ꢀ19.6 (d, J ~ 90 Hz).
2
2
BH
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
31
1
A
4
B
2
P NMR (243 MHz, CD Cl , 299 K): δ = ꢀ7.4 (br dd, J =
Mes ), 143.0 (d, JPC = 3.2 Hz, pꢀMes ), 142.5 (d, JPC = 7.5
2
2
PH
3
19
B 2 A 2
4
67.5 Hz, J = 28.8 Hz). F NMR (564 MHz, CD Cl , 299
Hz, oꢀMes ), 142.0 (d, JPC = 11.7 Hz, oꢀMes ), 141.9 (d, JPC
B 3
HH
2
2
A
B
K): δ = ꢀ131.8 (br m, 2F, oꢀC F ), ꢀ133.0 (br, 2F, oꢀC F ), ꢀ
1
1
= 8.6 Hz, o´ꢀMes ), 138.5 (d, JPC = 3.3 Hz, iꢀPh), 132.7 (d,
6
5
6 5
3
A
3
3
A 3 B
63.2 (t, J = 20.2 Hz, 1F, pꢀC F ), ꢀ164.6 (t, J = 20.2 Hz,
F, pꢀC F ), ꢀ165.4 (m, 2F, mꢀC F ), ꢀ167.2 (m, 2F, mꢀ
JPC = 11.8 Hz, mꢀMes ), 132.4 (d, JPC = 10.7 Hz, mꢀMes ),
3 A 3
FF
6
5
FF
B
A
132.0 (d, JPC = 8.4 Hz, m´ꢀMes ), 131.4 (d, JPC = 10.1 Hz,
6
5
6 5
B
+
B
3
5
C F ). HRMS: calc. for C H PBF [M+H] : 709.22478.
m´ꢀMes ), 128.4 (br d, JPC = 5.9 Hz, oꢀPh), 128.3 (d, JPC
=
=
6
5
37 33
10
ꢀ
1
4
1
Found: 709.22413. IR (KBr): ύ/cm = 2966 (s), 2929 (s),
2967 (m), 2370(s, PH/BH), 1636 (w), 1604 (m), 1509 (s),
1457 (vs). Xꢀray crystal structure analysis of compound 5:
formula C H BF P, M = 710.42, colourless crystal, 0.25 x
0
2
3.3 Hz, pꢀPh), 127.2 (d, JPC = 1.8 Hz, mꢀPh), 121.6 (d, JPC
A 1 B
45.1 Hz, iꢀMes ), 120.9 (d, JPC = 53.4 Hz, iꢀMes ), 87.6 (d,
1
3
2
J
J
PC = 22.6 Hz, CHO), 42.5 (d, JPC = 6.2 Hz, Cꢀ1), 41.6 (d,
PC = 16.8 Hz, Cꢀ7), 40.3 (d, JPC = 36.6 Hz, PCH), 38.8 (br
d, JPC = 7.4 Hz, Cꢀ4), 35.1 (br, BCH), 34.1 (Cꢀ5), 27.0 (oꢀ
1
37 34
10
3
.05 x 0.03 mm, a = 17.5236(5), b = 18.1897(6), c =
3
ꢀ3
MesA
3
MesB
3
0.2976(3) Å, V = 6469.8(3) Å , ρ = 1.459 gcm , ꢄ = 1.515
CH
3
), 25.1 (d, JPC = 5.6 Hz, o´ꢀCH
3
), 24.2 (d, JPC
=
calc
ꢀ
1
MesA
MesB
mm , empirical absorption correction (0.703 ≤ T ≤ 0.956), Z =
, orthorhombic, space group Pbca (No. 61), λ = 1.54178 Å, T
4.9 Hz, o´ꢀCH
PC = 1.4 Hz, pꢀCH
3
), 24.0 (br, oꢀCH
3
), 22.4 (Cꢀ6), 21.1 (d,
5
MesA
1
5
MesB
8
=
±
J
3
), 20.8 (d, JPC = 1.3 Hz, pꢀCH
3
).
11
223(2) K, ω and φ scans, 33268 reflections collected (±h,
[C
6
F
5
not listed]. B{ H} NMR (160 MHz, CD
2
Cl , 299 K): δ
2
31
1
ꢀ1
=
0.2 (ν1/2 ≈ 150 Hz). P{ H} NMR (202 MHz, CD Cl , 299
2 2
19
k, ±l), [(sinθ)/λ] = 0.60 Å , 5632 independent (Rint = 0.056)
K): δ = 38.9 (ν1/2 ≈ 5 Hz). F NMR (470 MHz, CD Cl , 213
and 5632 observed reflections [I>2σ(I)], 456 refined parameꢀ
ters, R = 0.045, wR = 0.114, max. (min.) residual electron
density 0.23 (ꢀ0.26) e.Å , hydrogen atoms at P1 and B1 were
refined freely, others hydrogen atoms calculated and refined as
riding atoms.
2
2
2
K): δ = ꢀ130.2, ꢀ133.5, ꢀ134.2, ꢀ134.8 (each m, 1F each, oꢀ
C F ), ꢀ160.5 (t, J = 20.7 Hz, 1F, pꢀC F ), ꢀ160.8 (t, J =
21.6 Hz, 1F, pꢀC F ), ꢀ164.3 (m, 1F, (m, 1F, mꢀC F ), ꢀ165.1 ,
3
3
ꢀ
3
6
5
FF
6
5
FF
6
5
6 5
ꢀ
1
(
2
1
m, 2F, mꢀC F ), ꢀ165.8 , (m, 1F, mꢀC F ). IR (KBr): ύ/cm =
6 5 6 5
953 (vs), 2875 (s), 2361 (w), 2339 (w), 1640 (m), 1606 (m),
512 (s), 1456 (vs). Xꢀray crystal structure analysis of comꢀ
pound 6: formula C H BF OP, M = 814.52, colourless crysꢀ
tal, 0.37 x 0.20 x 0.10 mm, a = 11.3261(2), b = 11.4019(2), c
18.0739(4) Å, α = 80.106(4), β = 86.398(7), γ = 67.178(8)°,
V = 2119.31(7) Å , ρ = 1.276 gcm , ꢄ = 0.141 mm , empirꢀ
Synthesis of compound 5-D
A solution of the compound 4 (243 mg, 0.343 mmol) in nꢀ
pentane was cooled (ꢀ60 °C) and degassed. D gas (1.2 bar)
44
38
10
2
was pressed over the solution for 3 minutes and the cooling
bath was removed. After stirring the reaction mixture for 30
minutes at r.t. the solvent was decanted off and the residual
yellowish precipitate was washed with nꢀpentane (1 x 4 mL).
Crystallisation from CH Cl gave the compound 5-D as a colꢀ
ourless crystalline solid (132 mg, 54% yield). H NMR (92
MHz, CD Cl , 299 K): δ = 7.24 (d, J = 71.7 Hz, 1D, DP),
2
1
=
3
ꢀ3
ꢀ1
calc
ical absorption correction (0.949 ≤ T ≤ 0.986), Z = 2, triclinic,
space group P
1
(No. 2), λ = 1.54178 Å, T = 223(2) K, ω and φ
2
2
scans, 16980 reflections collected (±h, ±k, ±l), [(sinθ)/λ] =
2
ꢀ1
0
.59 Å , 7239 independent (R = 0.037) and 6197 observed
int
2
1
2
2
PD
reflections [I>2σ(I)], 520 refined parameters, R = 0.067, wR
1
1
.55 (br, 1D, DB). B NMR (160 MHz, CD Cl , 299 K): δ = ꢀ
9.8 (ν1/2 ~ 80 Hz). P{ H} NMR (243 MHz, CD Cl , 299 K):
ꢀ
2
2
=
0.199, max. (min.) residual electron density 0.35 (ꢀ0.30) e.Å
, hydrogen atoms were calculated and refined as riding atoms.
3
1
1
3
2
2
1
δ = ꢀ8.0 (1:1:1 t, J = 71.7 Hz).
PD
Synthesis of compound 7
Synthesis of compound 6
HB(C F ) (97 mg, 0.280 mmol) and the dimesitylnorꢀ
6
5 2
HB(C F ) (96 mg, 0.277 mmol) and dimesitylnorꢀ
6
5 2
bornenylphosphane (100 mg, 0.276 mmol) were weighed toꢀ
gether, dissolved in nꢀpentane (70 mL) and stirred for 2 h. at
r.t. to get a yellow solution. The solution was cooled to ꢀ78 °C
bornenylphosphane (100 mg, 0.276 mmol) were weighed toꢀ
gether, dissolved in nꢀpentane (15 mL) and stirred for 30 min.
at r.t. to get a yellow solution. Then a solution of benzaldeꢀ
hyde (40.0 mg, 0.377 mmol) in nꢀpentane (2.0 mL) was added
to the solution of the FLP 4 and instantaneous formation of a
colourless precipitate was observed. The reaction mixture was
stirred at r.t. for 15 min. The volatiles were removed under
vacuum. The obtained residue was washed with nꢀpentane (3
mL) and dried under vacuum overnight to get compound 6 as
a colourless solid (166 mg, 85% yield). There is about 5% of
an unidentified compound present which could not be separatꢀ
and degassed by applying vacuum. CO gas was pressed (3.0
2
bar) onto the solution. The cooling bath was removed and the
solution was allowed to warm to r.t. Formation of a precipitate
was observed. The reaction mixture was cooled to ꢀ78 °C and
the solvent was removed via a filter canula. The residue was
washed with precooled nꢀpentane (1 x 3 mL) and dried under
vacuum to get the compound 7 as colourless solid (162 mg, 78
yield). Crystals of the compound 7 suitable for Xꢀray crystal
structure analysis were obtained by slow diffusion of nꢀ
pentane to a solution of compound 7 in CH Cl at ꢀ35 °C. H
NMR (500 MHz, CD Cl , 213 K): δ = 7.03 (d, J = 3.9 Hz,
%
31
1
ed even by crystallization ( P NMR: δ = 30.7). Crystals of
compound 6 suitable for Xꢀray crystal structure analysis were
obtained by slow diffusion of nꢀpentane to a solution of comꢀ
pound 6 in CH Cl at ꢀ35 °C. H NMR (500 MHz, CD Cl ,
2
2
4
2
2
PH
A,B
A
4
2
H, mꢀMes B ), 6.94 (br, 1H, m´ꢀMes ), 6.91 (d, J = 3.8 Hz,
1H, m´ꢀMes ), 3.08 (br d, J = 12.0 Hz, 1H, PCH), 2.83 (br
PH
1
3
2
2
2
2
PH
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 12 of 16
), 1.40/1.02
MesA
3
MesA
s, 1H, Hꢀ1), 2.63 (s, 3H, oꢀCH
), 2.50 (br, 1H, Hꢀ4), 2.38
Hz, J = 10.6 Hz, BCH), 1.69 (s, 3H, o´ꢀCH3
3
HH
MesB
MesB
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
(s, 3H, oꢀCH
), 2.30 (s, 3H, pꢀCH
), 2.28 (s, 3H, pꢀ
(each br m, each1H, Hꢀ5), 1.13/0.83 (each br m, each1H, Hꢀ
6), 1.13/0.69 (each br m, each1H, Hꢀ7). [ tentatively asꢀ
signed]. C{ H} NMR (126 MHz, CD Cl , 299 K)[selected
3
3
MesA
MesB
MesA
t
CH3
), 1.83 (s, 3H, o´ꢀCH
), 1.74 (s, 3H, o´ꢀCH3
),
3
3
3
13
1
1.61 (br dd, J = 21.6 Hz, J = 12.0 Hz, 1H, BCH),
PH
HH
2
2
1
B
1.31/0.92 (each br m, each 1H, Hꢀ5), 1.23/1.01 (each br m,
resonances]: δ = 121.4 (d, J = 35.4 Hz, iꢀMes ), 116.5 (d,
JPC = 44.5 Hz, iꢀMes ), 43.1 (d, J = 12.6 Hz, Cꢀ1), 41.3 (d,
JPC = 15.2 Hz, PCH), 40.6 (d, J = 15.6 Hz, Cꢀ7), 39.5 (br
m, Cꢀ4), 35.6 (br, BCH), 33.3 (Cꢀ5), 22.7 (br, Cꢀ6). P NM19R
(202 MHz, CD Cl , 299 K): δ = 59.5 (dm, J = 24.7 Hz. F
2 2 PH
PC
13
1
1
1
A
each 1H, Hꢀ6), 1.17/0.61 (each br m, each 1H, Hꢀ7). C{ H}
PC
1
3
NMR (126 MHz, CD Cl , 213 K): δ = 160.7 (d, J = 88.0
2
2
PC
PC
4
B
2
31
Hz, CO), 144.9 (d, J = 3.0 Hz, pꢀMes ), 144.13 (d, J
=
PC
PC
A
2
A
3
1
(
1
2.6 Hz, o´ꢀMes ), 144.10 (d, J = 2.2 Hz, pꢀMes ), 143.1
PC
2
B
2
B
d, J = 9.8 Hz, o´ꢀMes ), 142.9 (d, J = 8.5 Hz, oꢀMes ),
NMR (470 MHz, CD Cl , 213 K): δ = ꢀ130.4, ꢀ132.3, ꢀ134.9, ꢀ
PC
PC
2 2
2
A
3
40.9 (d, J = 12.4 Hz, oꢀMes ), 132.5 (d, J = 11.1 Hz,
m´ꢀMes ), 132.1 (d, J = 12.5 Hz, mꢀMes ), 131.9 (d, J
0.6 Hz, mꢀMes ), 131.0 (d, J = 10.5 Hz, m´ꢀMes ), 118.0
135.5 (each m, each 1F, oꢀC F ), ꢀ158.6, ꢀ158.9 (each t, each
6 5
3
PC
PC
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
A
3
A
3
=
JFF = 20.6 Hz, each 1F, pꢀC F ), ꢀ163.6, ꢀ164.06, 164.11, ꢀ
6 5
1
PC
PC
B
3
B
1
(
4
164.9 (each m, each 1F, mꢀC F ). Minor isomer (ca. 35%): H
6 5
PC
1
A
1
B
d, J = 68.3 Hz, iꢀMes ), 114.3 (d, J = 69.1 Hz, iꢀMes ),
NMR (500 MHz, CD Cl , 299 K): δ = 7.14 (br s, 1H, mꢀ
2 2
A 4 B
PC
PC
1
2
2.7 (d, J = 21.8 Hz, PCH), 42.6 (d, J = 7.3 Hz, Cꢀ1),
Mes ),7.11 (br d, J = 4.0 Hz, 1H, mꢀMes ), 6.96 (br s, 1H,
PH
A B 1
PC
PC
3
40.8 (d, J = 17.7 Hz, Cꢀ7), 38.2 (br, Cꢀ4), 33.7 (br, BCH),
m´ꢀMes ), 6.89 (br s, 1H, m´ꢀMes ), 3.11 (br d, J = 10.5
PH
MesA
PC
3
MesA
3
33.3 (br, Cꢀ5), 24.1 (d, J = 3.5 Hz, o´ꢀCH
), 23.9 (d, J
Hz, 1H, PCH), 2.79 (br, 1H, Hꢀ1), 2.70 (s, 3H, oꢀCH
),
2.67 (d, J = 1.9 Hz, 3H, oꢀCH3 ), 2.66 (br, 1H, Hꢀ4),
PC
3
PC
3
MesB
MesA
3
3
MesB
= 7.6 Hz, o´ꢀCH
), 23.3 (br, oꢀCH3
), 22.9 (d, J = 4.6
3
PC
PH
MesB
MesB
MesA t
MesB t
Hz, oꢀCH
CH3
), 21.2 (br, Cꢀ6), 21.0 (pꢀCH
), 20.7 (pꢀ
2.35 (s, 3H, pꢀCH3
) , 2.32 (s, 3H, pꢀCH3 ) , 2.06 (s, 3H,
3
3
MesA
31
1
MesB
), 1.97 (s, 3H, o´ꢀCH3
MesA 3
). [C F not listed] P{ H} NMR (202 MHz, CD Cl ,
o´ꢀCH3
), 1.90 (br ddm, J
=
PH
6
5
2
2
1
9
3
2
2
13 K): δ = 13.7 (ν1/2 ≈ 4 Hz). F NMR (470 MHz, CD Cl ,
22.4, J = 11.0, 1H, BCH), 1.47/1.19 (each br m, each1H, Hꢀ
2
2
PH
A
B
13 K): δ = ꢀ129.6 (m, 1F, oꢀC F ), ꢀ131.4 (m, 1F, oꢀC F ), ꢀ
5), 1.12/0.54 (each br m, each1H, Hꢀ7), 1.12/0.80 (each br m,
6
5
6 5
B
A
t
t
13
1
1
36.2 (m, 1F, o´ꢀC F ), ꢀ137.8 (m, 1F, o´ꢀC F ), ꢀ158.8 (t,
each1H, Hꢀ6) . [ tentatively assigned] C{ H} NMR (126
6
5
6 5
3
A
3
1
JFF = 21.0 Hz, 1F, pꢀC F ), ꢀ159.1 (t, J = 21.0 Hz, 1F, pꢀ
C F ), ꢀ163.1 (m, 1F, mꢀC F ), ꢀ163.4 (m, 1F, m´ꢀC F ), ꢀ
MHz, CD Cl , 299 K) [selected resonances]: δ = 124.5 (d, J
6
5
FF
2
2
PC
B
A
A
B
1
A
6
5
6
5
6
5
= 22.1 Hz, iꢀMes ), 121.7 (d, J = 50.2 Hz, iꢀMes ), 43.1 (d,
PC
1 3
B
B
1
64.1 (m, 1F, mꢀC F ), ꢀ164.8 (m, 1F, m´ꢀC F ). HRMS:
JPC = 12.6, Cꢀ1), 41.0 (d, J = 11.5 Hz, PCH), 40.1 (d, J
=
PC
6
5
6
5
PC
+
calc. for C H PBO F [M+HꢀCO ] : 709.22478. Found:
15.1, Cꢀ7), 38.5 (br, Cꢀ4), 33.4 (Cꢀ5), 29.9 (br, BCH), 22.7
38
33
2
10
2
t
t
3
1
7
09.22578. CO seems to be released under the applied condiꢀ
(Cꢀ6) . [ tentatively assigned]. P NMR (202 MHz, CD Cl ,
2 2
3 19
2
ꢀ
1
tions. IR (KBr): ύ/cm = 2957(s), 2878 (m), 2360 (w), 2338
(m), 1704 (s, CO), 1642 (m), 1605 (m), 1513 (m), 1458 (vs).
Xꢀray crystal structure analysis of 7: formula C H BF P *
299 K): δ = 53.6 (dm, J = 23.3 Hz). . F NMR (470 MHz,
PH
CD Cl , 213K): δ = ꢀ129.9, ꢀ134.0, ꢀ135.5, ꢀ136.6 (each m,
2
2
3
each 1F, oꢀC F ), ꢀ159.1, ꢀ160.0 (each t, each J = 20.6 Hz,
3
8
32
10
6
5
FF
CH Cl , M = 837.34, colourless crystal, 0.15 x 0.10 x 0.05
each 1F, pꢀC F ), ꢀ163.8, ꢀ164.0, ꢀ165.0, ꢀ165.1 (each m, each
2
2
6 5
mm, a = 10.4235(10), b = 17.0105(9), c = 21.3930(20) Å, V =
1F, mꢀC F ). Data from the mixture: HRMS: calc. for
6 5
+
3
ꢀ3
ꢀ1
3
793.2(5) Å , ρcalc = 1.466 gcm , ꢄ = 2.691 mm , empirical
C H PBSO F [M+HꢀSO ] : 709.22478. Found: 709.22578.
37 33 2 10 2
absorption correction (0.688 ≤ T ≤ 0.877), Z = 4, orthorhomꢀ
bic, space group P2 2 2 (No. 19), λ = 1.54178 Å, T = 223(2)
SO seems to be released under the applied conditions. IR
2
ꢀ1
1
1
1
(KBr): ύ/cm = 2957 (s), 2928 (s), 2880 (s), 2361 (m), 2341
(m), 1641 (m), 1606 (m), 1559 (w), 1515 (s), 1457 (vs). Xꢀray
crystal structure analysis of compound 8b: formula
K, ω and φ scans, 20986 reflections collected (±h, ±k, ±l),
ꢀ
1
[
5
=
0
(sinθ)/λ] = 0.60 Å , 6556 independent (R = 0.040) and
int
989 observed reflections [I>2σ(I)], 515 refined parameters, R
0.041, wR = 0.097, max. (min.) residual electron density
.16 (ꢀ0.22) e.Å , hydrogen atoms calculated and refined as
riding atoms. Flack parameter Flack parameter was refined to
.01(2).
C
37
H
32BF10
O
2
PS, M = 772.47, colourless crystal, 0.10 x 0.07 x
2
0.02 mm, a = 16.4556(7), b = 16.7148(6), c = 24.6103(8) Å,
ꢀ3
3
ꢀ3
ꢀ1
V = 6769.1(4) Å , ρcalc = 1.516 gcm , ꢄ = 2.107 mm , empiriꢀ
cal absorption correction (0.817 ≤ T ≤ 0.959), Z = 8, orthoꢀ
rhombic, space group Pbca (No. 61), λ = 1.54178 Å, T =
223(2) K, ω and φ scans, 36959 reflections collected (±h, ±k,
0
Synthesis of compound 8
ꢀ
1
±l), [(sinθ)/λ] = 0.60 Å , 5779 independent (R = 0.112) and
int
HB(C F ) (43 mg, 0.123 mmol) and the dimesitylnorꢀ
6
5 2
3593 observed reflections [I>2σ(I)], 456 refined parameters, R
= 0.057, wR = 0.144, max. (min.) residual electron density
.26 (ꢀ0.50) e.Å , hydrogen atoms calculated and refined as
bornenylphosphane (40.0 mg, 0.121 mmol) were weighed
together, dissolved in nꢀpentane (6.0 mL) and stirred for 30
min. at r.t. to get a yellow solution of the compound 4. The
2
ꢀ3
0
riding atoms.
solution was degassed by applying some vacuum and SO gas
2
Synthesis of compound 12
was pressed (2.0 bar) over the solution which resulted in the
formation of a colourless precipitate. The reaction mixture was
stirred at r.t. for 5 min., the reaction flask was flushed with
argon and the solvent was decanted off. The residue was
washed with nꢀpentane (1 × 3 mL) and dried under vacuum to
get 8a and 8b as a colourless solid (68 mg, 80% yield). The
two diastereoisomers were obtained in a ratio of ca.5:2 (deꢀ
HB(C F )
(345 mg, 1.00 mmol) and the norꢀ
6
5 2
bornenylphosphane 1 (360.0 mg, 1.00 mmol) were weighed
together, dissolved in nꢀpentane (70 mL) and stirred for 30
min. at r.t. to get a yellow solution. The solution was cooled to
ꢀ78 °C and degassed by applying vacuum. NO gas was pressed
(2.0 bar) onto the solution and quick formation of a precipitate
was observed. The cooling bath was removed and the reaction
mixture was stirred at r.t. for further 10 min. The reaction flask
was flushed with argon and the solvent was removed under
vacuum. The residue was washed with nꢀpentane (1 × 10 mL)
and dried under vacuum to get compound 12 as turquoise solꢀ
id (643 mg, 87% yield). Crystals of the compound 12 suitable
for Xꢀray crystal structure analysis were obtained by slow difꢀ
1
termined by NMR spectroscopy). Major isomer (ca 65%): H
NMR (500 MHz, CD Cl , 299 K): δ = 7.16 (br s, 1H, mꢀ
2
2
A
4
B
Mes ),7.09 (br d, J = 4.5 Hz, 1H, mꢀMes ), 6.94 (s, 2H, m´ꢀ
Mes ), 3.54 (br m, 1H, PCH), 2.88 (br, 1H, Hꢀ1), 2.74 (br d,
JPH = 1.7 Hz, 3H, oꢀCH3
br, 1H, Hꢀ4), 2.35 (s, 3H, pꢀCH
PH
A,B
3
MesA
MesB t
), 2.65 (s, 3H, oꢀCH
) , 2.42
3
MesA t
(
) , 2.34 (s, 3H, pꢀ
3
MesB t
MesB t
3
CH3 ) , 2.06 (s, 3H, o´ꢀCH3 ) , 1.82 (br dd, J = 24.4
PH
ACS Paragon Plus Environment

Page 13 of 16
Journal of the American Chemical Society
13.0849(2), c = 15.5601(3) Å, α = 113.879(2), β = 96.700(1),
fusion of nꢀpentane to a solution of compound 12 in CH Cl at
2
2
+
3
ꢀ3
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
ꢀ35 °C. HRMS: calc. for C H PBF NONa [M+Na] :
γ = 93.957(1)°, V = 1657.44(5) Å , ρcalc = 1.482 gcm , ꢄ =
0.173 mm , empirical absorption correction (0.971 ≤ T ≤
3
7
32
10
ꢀ
1
ꢀ1
761.20535. Found: 761.20330. IR (KBr): ύ/cm = 2951 (s),
2883 (m), 1641 (w), 1606 (m), 1513 (s), 1463 (vs). Xꢀray crysꢀ
tal structure analysis of compound 12: formula
C H BF NOP * CH Cl , M = 823.34, pale green crystal,
0.988), Z = 2, triclinic, space group P
1 (No. 2), λ = 0.71073
Å, T = 223(2) K, ω and φ scans, 17726 reflections collected
ꢀ
1
37 32
10
2
2
(±h, ±k, ±l), [(sinθ)/λ] = 0.60 Å , 5725 independent (R
=
int
0
1
1
.35 x 0.25 x 0.10 mm, a = 10.5699(3), b = 17.6128(6), c =
0.9505(5) Å, β = 113.061(2) °, V = 1875.70(12) Å , ρ
.458 gcm , ꢄ = 2.679 mm , empirical absorption correction
0.041) and 4939 observed reflections [I>2σ(I)], 470 refined
parameters, R = 0.053, wR = 0.126, max. (min.) residual elecꢀ
tron density 0.22 (ꢀ0.22) e.Å , hydrogen atom at O1 was reꢀ
fined freely, others hydrogen atoms were calculated and reꢀ
fined as riding atoms.
3
2
=
calc
ꢀ
3
ꢀ1
ꢀ
3
(0.452 ≤ T ≤ 0.774), Z = 2, monoclinic, space group P2 (No.
1
4
), λ = 1.54178 Å, T = 223(2) K, ω and φ scans, 10974 reflecꢀ
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
ꢀ1
tions collected (±h, ±k, ±l), [(sinθ)/λ] = 0.60 Å , 5757 indeꢀ
pendent (Rint = 0.039) and 5666 observed reflections [I>2σ(I)],
5
residual electron density 0.48 (ꢀ0.28) e.Å , hydrogen atoms
were calculated and refined as riding atoms. Flack parameter
Flack parameter was refined to 0.03(2).
Synthesis of compound 14
2
HB(C F ) (49 mg, 0.142 mmol) and the dimesitylnorbornꢀ
6
5 2
21 refined parameters, R = 0.039, wR = 0.105, max. (min.)
ꢀ3
enylphosphane 3 (50 mg, 0.138 mmol) were weighed together,
dissolved in nꢀpentane (5.0 mL) and stirred for 30 min. at r.t.
to get a yellow solution of compound 4. The solution was deꢀ
gassed by freezeꢀpumpꢀthaw cycles (×2), cooled to ꢀ78 °C.
Ethylene gas was pressed (3.0 bar) over the solution and the
reaction mixture allowed to warm to r.t. The reaction mixture
was kept at r.t. for 2 days without stirring. The colour of the
solution almost disappeared and colourless crystals were
formed. The solvent was decanted off and the residue was
washed with nꢀpentane (1 × 3 mL) to get 14 as a colourless
crystalline solid (71 mg, 68% yield). Crystals of compound 14
suitable for Xꢀray crystal structure analysis were obtained by
slow diffusion of nꢀpentane into a solution of compound 14 in
Synthesis of compound 13
The nitroxide adduct 12 (95 mg, 0.129 mmol) was dissolved
in benzene (7.0 mL) to get
a green solution. 1,4ꢀ
cyclohexadiene (0.1 mL, 1.057 mmol) was added to the soluꢀ
tion and stirred at r.t for 5 min. to get a colourless solution.
The volatiles were evaporated in vacuo, the obtained residue
was washed with nꢀpentane (2 x 5 mL) and dried under vacuꢀ
um to get compound 13 as colourless crystalline solid (91 mg,
96 % yield). Crystals of the compound 13 suitable for Xꢀray
crystal structure analysis were obtained by slow diffusion of nꢀ
1
CH Cl at ꢀ35 °C. H NMR (500 MHz, CD Cl , 299 K): δ =
2
2
2
2
1
4
A
4
pentane to a solution of compound 13 in CH Cl at ꢀ35 °C. H
NMR (600 MHz, CD Cl , 233 K): δ = 7.05 (d, J = 4.2 Hz,
6.95 (d, J = 4.5 Hz, 2H, mꢀMes ), 6.94 (d, J = 4.5 Hz,
PH PH
B 3
2
2
4
2
2
PH
2H, mꢀMes ), 6.72 (dm, J = 12.2 Hz, 1H, =CH), 3.62 (br s,
PH
A
B
A
1
6
1
1
2
H, mꢀMes ), 6.90 (br, 1H, mꢀMes ), 6.86 (br, 1H, m´ꢀMes ),
.74 (d, J = 4.8 Hz, 1H, m´ꢀMes ), 4.66 (d, J = 11.6 Hz,
H, OH), 2.71 (br m, 1H, Hꢀ1), 2.61 (br m, 1H, Hꢀ4), 2.60 (m,
H, PCH), 2.55 (s, 3H, oꢀCH
Hꢀ1), 3.11 (br s, Hꢀ4), 2.65, 2.42 (each m, each 1H, PCH ),
2
MesA,B MesB
4
B
PH
FH
2.31 (s, 6H, pꢀCH3
), 2.12 (br s, 6H, oꢀCH3 ), 2.04 (br
MesA
s, 6H, oꢀCH3
), 1.83/0.95 (each br m, each 1H, Hꢀ5),
MesA
MesB
), 2.41 (s, 3H, oꢀCH3 ),
1.81/1.50 (each br m, each 1H, Hꢀ7), 1.69/0.56 (each br m,
3
MesA
MesB
.28 (s, 3H, pꢀCH
), 2.24 (s, 3H, pꢀCH
), 1.93 (s, 3H,
each 1H, Hꢀ6), 1.13/0.95 (each br m, each 1H, BCH ), 0.82
3
3
2
MesA
MesB
3
o´ꢀCH3
1
1
), 1.92 (s, 3H, o´ꢀCH3 ), 1.54 (m, 1H, BCH),
(br m, 2H, BCH CH ), 0.45 (t, J = 7.5 Hz, 3H, BCH CH ).
2
3
HH
2
3
13
1
.31/1.04 (each m, each 1H, Hꢀ5), 1.24/0.81 (each m, each
H, Hꢀ7), 1.13/0.51 (each m, each 1H, Hꢀ6). C{ H} NMR
C{ H} NMR (126 MHz, CD Cl , 299 K): δ = 157.9 (=CH),
2 2
4 A,B
1
3
1
144.1, 144.0 (each d, each J = 2.9 Hz, pꢀMes ), 142.1 (d,
PC
2 A 2 B
2
(151 MHz, CD Cl , 233 K): δ = 144.5 (d, J = 8.3 Hz, o´ꢀ
JPC = 9.4 Hz, oꢀMes ), 141.9 (br d, J = 9.3 Hz, oꢀMes ),
PC
3 A,B 1
2
2
PC
A
2
B
4
Mes ), 144.2 (d, J = 5.9 Hz, oꢀMes ), 143.3 (d, J = 2.6
Hz, pꢀMes ), 142.7 (d, J = 2.9 Hz, pꢀMes ), 140.7 (d, J
12.1 Hz, oꢀMes ), 139.4 (d, J = 16.3 Hz, o´ꢀMes ), 131.5
132.4 (d, J = 11.1 Hz, mꢀMes ), 131.2 (d, J = 71.3 Hz,
PC PC
1 A 1
PC
PC
A
4
B
2
=
=CP), 120.3 (d, J = 80.2 Hz, iꢀMes ), 119.6 (d, J = 81.5
PC PC
B 3 2
PC
PC
A
2
B
PC
Hz, iꢀMes ), 49.0 (d, J = 4.5 Hz, Cꢀ7), 48.1 (d, J = 7.8
PC PC
3 1
3
A
3
(d, J = 11.2 Hz, m´ꢀMes ), 131.4 (d, J = 10.4 Hz, mꢀ
Hz, Cꢀ1), 44.7 (d, J = 12.8 Hz, Cꢀ4), 28.7 (d, J = 39.5
PC
PC
PC
PC
B
3
A
3
3
Mes ), 131.3 (d, J = 12.2 Hz, mꢀMes ), 130.0 (d, J
1
=
Hz, PCH ), 25.9 (Cꢀ6), 25.6 (d, J = 3.4 Hz, Cꢀ5), 23.8 (d,
PC
PC
2
PC
B
1
B
3
MesA
3
1.5 Hz, m´ꢀMes ), 123.1 (d, J = 80.3 Hz, iꢀMes ), 119.9
JPC = 4.5 Hz, 3H, oꢀCH3
), 23.6 (d, J = 4.2 Hz, 3H, oꢀ
PC
5
PC
1
A
1
MesB
(d, J = 88.7 Hz, iꢀMes ), 49.8 (d, J = 63.8 Hz, PCH),
CH3 ), 21.11, 21.09 (each d, each JPC = 1.4 Hz, pꢀ
PC
PC
3
2
MesA,B
4
2
2
2.3 (d, J = 18.7 Hz, Cꢀ7), 41.4 (br, BCH), 40.3 (d, J
.1 Hz, Cꢀ1), 37.7 (m, Cꢀ4), 35.4 (Cꢀ5), 24.3 (br, oꢀCH
=
PC
MesA
),
CH3
), 17.3 (br, BCH ), 14.3 (br, BCH CH ), 11.0
2 2 3
11 1
PC
3
(BCH CH ). [C F not listed]. B{ H} NMR (160 MHz,
2
3
6 5
3
MesA
3
31
1
3.2 (d, J = 3.8 Hz, o´ꢀCH
), 21.2 (d, J = 8.6 Hz, o´ꢀ
CD Cl , 299 K): δ = ꢀ10.4 (ν ≈ 80 Hz). P{ H} NMR (202
2 2 1/2
19
PC
3
PC
MesB
5
MesB
5
CH3 ), 20.9 (d, J = 1.2 Hz, pꢀCH3 ), 20.8 (d, J
1
CH3 ). [C F not listed. B{ H} NMR (192 MHz, CD Cl ,
233 K): δ = ꢀ6.7 (ν1/2 ≈ 400 Hz). P{ H} NMR (242 MHz,
CD Cl , 233 K): δ = 40.8 (ν ≈ 5 Hz). F NMR (564 MHz,
CD Cl , 233 K): δ = ꢀ130.2, (m, 1F, oꢀC F ), ꢀ133.2, (m, 1F,
oꢀC F ), ꢀ133.2 (m, 1F, o´ꢀC F ), ꢀ144.8 (m, 1F, o´ꢀC F ), ꢀ
1
1
=
MHz, CD Cl , 299 K): δ = 17.0 (ν ≈ 50 Hz). F NMR (470
2 2 1/2
PC
PC
MesA
3
.2 Hz, pꢀCH
), 20.5 (br, Cꢀ6), 20.2 (d, J = 4.1 Hz, oꢀ
MHz, CD Cl , 299 K): δ = ꢀ133.1 (m, 4F, oꢀC F ), ꢀ164.77, ꢀ
2 2 6 5
3
3
PC
MesB
11
1
6
5
2
2
164.81 (each t, each J = 20.8 Hz, pꢀC F ), ꢀ167.0 (m, 4F, mꢀ
FF 6 5
+
3
1
1
C F ). HRMS: calc. for C H PBF Na [M+NaꢀH] :
6 5 41 40 10
ꢀ1
1
9
2
2
1/2
787.27002. Found: 787.27022. IR (KBr): ύ/cm = 2941 (s),
2362 (w), 2343 (w), 1636 (w), 1606 (w), 1559 (w), 1507 (s),
1449 (vs). Xꢀray crystal structure analysis of compound 14:
formula C H BF P, M = 764.51, colourless crystal, 0.23 x
A
2
2
6 5
B
A
B
6
5
6
5
6 5
3
A
3
60.1 (t, J = 20.9 Hz, 1F, pꢀC F ), ꢀ160.5 (t, J = 20.7 Hz,
FF 6 5 FF
A B
41
40
10
F, pꢀC F ), ꢀ164.0 (m, 1F, mꢀC F ), ꢀ164.8 (m, 1F, m´ꢀ
6
5
6
5
0.13 x 0.05 mm, a = 17.5033(6), b = 11.6428(5), c =
B
A
3
C F ), ꢀ165.1 (m, 2F, mꢀ, m´ꢀC F ). HRMS: calc. for
C H PBF NONa [M+Na] : 762.21318. Found: 762.21269.
6
5
6
5
19.5772(13) Å, β = 111.969(3) °, V = 3699.9(3) Å , ρ
=
calc
+
ꢀ
3
ꢀ1
37
33
10
1.372 gcm , ꢄ = 1.364 mm , empirical absorption correction
ꢀ
1
IR (KBr): ύ/cm = 3532 (s, OH), 2954 (s), 2874 (s), 1640 (m),
606 (m), 1512 (s), 1458 (vs). Xꢀray crystal structure analysis
of compound 13: formula C H BF NOP, M = 739.42,
(
0.744 ≤ T ≤ 0.934), Z = 4, monoclinic, space group P2 /n
1
1
(
No. 14), λ = 1.54178 Å, T = 223(2) K, ω and φ scans, 31943
ꢀ
1
3
7
33
10
reflections collected (±h, ±k, ±l), [(sinθ)/λ] = 0.60 Å , 6398
independent (Rint = 0.069) and 4845 observed reflections
colourless crystal, 0.17 x 0.13 x 0.07 mm, a = 9.0382(2), b =
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 14 of 16
2
[
I>2σ(I)], 485 refined parameters, R = 0.058, wR = 0.150,
Chase, P.; Hastie, J. J.; Geier, S. J.; Farrell, J. M.; Brown, C. C.;
Heiden, Z. M.; Welch, G. C.; Ullrich, M. Inorg. Chem. 2011, 50,
ꢀ
3
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
max. (min.) residual electron density 0.30 (ꢀ0.30) e.Å , hydroꢀ
gen atoms were calculated and refined as riding atoms.
1
1
2338. f) Segawa, Y.; Stephan, D. W. Chem. Commun. 2012, 48,
1963. g) Stephan, D. W. Org. Biomol. Chem. 2012, 10, 5740. h)
Farrel, M. J.; Hatnean, A. J.; Stephan, D. W. J. Am. Chem. Soc. 2012,
134, 15728. i) Stephan, D. W.; Erker, G. Top. Curr. Chem. 2013,
332, 85.
(3) a) Spies, P.; Schwendemann, S.; Lange, S.; Kehr, G.; Fröhlich, R.;
Erker, G. Angew. Chem. 2008, 120, 7654; Angew. Chem. Int. Ed.
Solid State NMR Spectroscopy.
11
The B MAS NMR spectra were acquired at 11.74 T and 7.05
T with a rotorꢀsynchronized Hahn echo sequence (90°ꢀτꢀ180°ꢀ
τꢀacq.) in case of 4 and singleꢀpulse spectra (45 degree excitaꢀ
tion pulses) in case of 8 using spinning frequencies of 14.0ꢀ
2
008, 47, 7543. b) Wang, H.; Fröhlich, R.; Kehr, G.; Erker, G. Chem.
Commun. 2008, 5966. c) Chen, D.; Klankermayer, J. Chem.
Commun. 2008, 2130. d) Xu, B.ꢀH.; Kehr, G.; Fröhlich, R.;
Wibbeling, B.; Schirmer, B.; Grimme, S; Erker, G. Angew. Chem.
2011, 123, 7321 (2012, 124, 10359); Angew. Chem. Int. Ed. 2011,
50, 7183 (2012, 51, 10213). e) Lu, Z.; Cheng, Z.; Chen, Z.; Wenig,
L.; Li, Z. H., Wang, H. Angew. Chem. 2011, 123, 12435; Angew.
Chem. Int. Ed. 2011, 50, 12227. f) Sumerin, V.; Chernichenko, K.;
Nieger, M.; Leskelä, M.; Rieger, B.; Repo, T. Adv. Synth. Catal.
1
5.0 kHz. 90° excitation pulses of 1.6ꢀ3.0 ꢄs length and reꢀ
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
laxation delays of 5 s ꢀ 20 s were used. Proton decoupling was
4
4
achieved during data acquisition using the TPPMꢀ15 decouꢀ
1
pling scheme (a H pulse length of approx. 7.5 ꢄs length corꢀ
3
1
1
responding to a 10/12 π pulse was applied). P{ H} CPMAS
NMR experiments were conducted at 7.05 T with a rotation
frequency of 10.0 kHz using the following acquisition parameꢀ
2
011, 353, 2093. g) Reddy, J. S.; Xu, B.ꢀH.; Mahdi, T.; Fröhlich, R.;
1
ters: H 90° pulse length 7.5 ꢄs, contact time 5 ms, relaxation
Kehr, G.; Stephan, D. W.; Erker, G. Organometallics 2012, 31, 5638.
h) Ghattas, G.; Chen, D.; Pan, F.; Klankermayer, J. Dalton Trans.
2012, 41, 9026. i) Erıs, G.; Nagy, K.; Mehdi, H.; Pápai, I.; Nagy, P.;
Király, P.; Tárkányi, G.; Soós, T. Chem. Eur. J. 2012, 18, 574. j)
Greb, L.; OñaꢀBurgos, P.; Schirmer, B.; Grimme, S.; Stephan, D. W.;
Paradies, J. Angew. Chem. 2012, 124, 10311; Angew. Chem. Int. Ed.
2012, 51, 10164. k) Inés, B.; Palomas, D.; Holle, S.; Steinberg, S.;
Nicasio, J. A.; Alcarazo, M. Angew. Chem. 2012, 124, 12533;
Angew. Chem. Int. Ed. 2012, 51, 12367.
1
11
31
1
31
11
delay 5 s. { H}→ B{ P} CPꢀREDOR and { H}→ P{ B}
CPꢀREAPDOR experiments were conducted at 7.05 T using
radio frequency power levels corresponding to 180° pulses of
11
31
7
1
ꢄs length, for B and 9 ꢄs length for P. Spinning speeds of
2.0 kHz were used in both cases. For creating a reproducible
magnetization in each experiment, a preꢀsaturation comb
consisting of 60 90° pulses was applied. H decoupling was
1
achieved by using the TPPMꢀ15 decoupling scheme during the
evolution and data acquisition period with rf fields
(
2
4) a) McCahill, J. S. J.; Welch, G. C.; Stephan, D. W. Angew. Chem.
007, 119, 5056; Angew. Chem. Int. Ed. 2007, 46, 4968. b) Sortais,
J.ꢀB.; Voss, T.; Kehr, G.; Fröhlich, R.; Erker, G. Chem. Commun.
009, 7417. c) Mömming, C. M.; Frömel, S.; Kehr, G.; Fröhlich, R.;
1
corresponding to a H nutation frequency of 59 kHz. In case of
1
1
the REAPDOR experiments the B resonance was excited for
one third of the rotor period during the dipolar evolution time.
All line shape simulations were performed using the DMFIT
2
Grimme, S.; Erker, G. J. Am. Chem. Soc. 2009, 131, 12280. d)
Ullrich, M.; Seto, K. S.ꢀH.; Lough, A. J.; Stephan, D. W. Chem.
Commun. 2009, 2335. e) Chen, C.; Fröhlich, R.; Kehr, G.; Erker, G.
Chem. Commun. 2010, 46, 3580. f) Mömming, C. M; Kehr, G.;
Wibbeling, B.; Fröhlich, R.; Schirmer, B.; Grimme, S.; Erker, G.
Angew. Chem. 2010, 122, 2464; Angew. Chem. Int. Ed. 2010, 49,
2414. g) Voss, T.; Chen, C.; Kehr, G.; Nauha, E.; Erker, G.; Stephan,
D. W. Chem. Eur. J. 2010, 16, 3005. h) Chen, C.; Eweiner, F.;
Wibbeling, B.; Fröhlich, R.; Senda, S.; Ohki, Y.; Tatsumi, K.;
Grimme, S.; Kehr, G.; Erker, G. Chem. Asian J. 2010, 5, 2199. i)
Voss, T.; Sortais, J.ꢀB.; Fröhlich, R.; Kehr, G.; Erker, G.
Organometallics 2011, 30, 584. j) Mömming, C. M; Kehr, G.;
Fröhlich, R.; Erker, G. Chem. Commun. 2011, 47, 2006. k) Feldhaus,
P.; Schirmer, B.; Wibbeling, B.; Daniliuc, C. G.; Fröhlich, R.;
Grimme, S.; Kehr, G.; Erker, G. Dalton Trans. 2012, 41, 9135.
4
5
software (version 2011) . For details of the DFTꢀcalculated
NMR parameters see the Supporting Information.
ASSOCIATED CONTENT
Details of the syntheses and characterization of all new comꢀ
pounds, and crystal structure data (CIF). This material is available
free of charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
Prof. Dr. Gerhard Erker
erker@uniꢀmuenster.de
(
5) a) Mömming, C. M; Kehr, G.; Fröhlich, R.; Erker, G. Dalton
Trans. 2010, 39, 7556. b) Xu, B.ꢀH.; Adler Yanez, R. A.; Nakatsuka,
H.; Kitamura, M.; Fröhlich, R.; Kehr, G.; Erker, G. Chem. Asian J.
2012, 7, 1347.
ACKNOWLEDGEMENTS
(6) a) Otten, E.; Neu, R. C.; Stephan, D. W. J. Am. Chem. Soc. 2009,
1
31, 9918. b) Neu, R. C.; Otten, E.; Lough, A.; Stephan, D. W. Chem.
Sci. 2011, 2, 170.
7) a) Cardenas, A. J. P.; Culotta, B. J.; Warren, T. H.; Grimme, S.;
Stute, A.; Fröhlich, R.; Kehr, G.; Erker, G. Angew. Chem. 2011, 123,
709; Angew. Chem. Int. Ed. 2011, 50, 7567. b) Sajid, M.; Stute, A.;
Financial support from the European Research Council (grant to
G. E) is gratefully acknowledged. The solid state NMR studies
were supported by the Deutsche Forschungsgemeinschaft, SFB
(
8
58. T.W. thanks the Fonds der Chemischen Industrie and the
7
NRW Forschungsschule “Molecules and Materials” for doctoral
stipends. We thank Prof. Dr. Stefan Grimme for his support with
the DFT calculations.
Cardenas, A. J. P.; Culotta, B. J.; Hepperle, J. A. M.; Warren, T. H.;
Schirmer, B.; Grimme, S.; Studer, A.; Daniliuc, C. G.; Fröhlich, R.;
Petersen, J. L.; Kehr, G.; Erker, G. J. Am. Chem. Soc, 2012, 134,
1
0156.
REFERENCES
(
8) a) Mömming, C. M.; Otten, E.; Kehr, G.; Fröhlich, R.; Grimme,
(
1) Stephan, D. W.; Erker, G. Angew. Chem. 2010, 122, 50; Angew.
S.; Stephan, D. W.; Erker, G.; Angew. Chem. 2009, 121, 6770;
Angew. Chem. Int. Ed. 2009, 48, 6643. b) Dureen, M. A.; Stephan, D.
W. J. Am. Chem. Soc. 2010, 132, 13559. c) Peuser, I.; Neu, R. C.;
Zhao, X.; Ulrich, M.; Schirmer, B.; Tannert, J. A.; Kehr, G.; Fröhlich,
R.; Grimme, S.; Erker, G.; Stephan, D. W. Chem. Eur. J. 2011, 17,
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