Reactivity of a Sterically Unencumbered α-Borylated Phosphorus Ylide towards Small Molecules

Article abstract of DOI:10.1002/chem.201902681

The influence of substituents on α-borylated phosphorus ylides (α-BCPs) has been investigated in a combined experimental and quantum chemical approach. The synthesis and characterization of Me₃PC(H)B(iBu)₂ (1), consisting of small Me substituents on phosphorous and iBu residues on boron, is reported. Compound 1 is accessible through a novel synthetic approach, which has been further elucidated through DFT studies. The reactivity of 1 towards various small molecules was probed and compared with that of a previously published derivative, Ph₃PC(Me)BEt₂ (2). Both α-BCPs react with NH₃ to undergo heterolytic N?H bond cleavage. Different di- and trimeric ring structures were observed in the reaction products of 1 with CO and CO₂. With PhNCO and PHNCS, the expected insertion products [Me₃PC(H)(PhNCO)B(iBu)₂] and [Me₃PC(H)(PhNCS)B(iBu)₂], respectively, were isolated.

Full text of DOI:10.1002/chem.201902681

A Journal of
Accepted Article
Title: Reactivity of a Sterically Unencumbered α-Borylated Phosphorus
Ylide Towards Small Molecules
Authors: Michael Radius, Ewald Sattler, Helga Berberich, and Frank
Breher
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Reactivity of a Sterically Unencumbered α-Borylated Phosphorus
Ylide Towards Small Molecules
Michael Radius,[a] Ewald Sattler,[a] Helga Berberich,[a] and Frank Breher*[a]
Abstract: The influence of the substituents on α-borylated
phosphorus ylides (α-BCPs) has been investigated in a combined
experimental and quantum chemical approach. The synthesis and
characterization of Me3PC(H)B(iBu)2 (1) consisting of small Me
substituents on phosphorous and iBu residues on boron is reported.
1 is accessible in a novel synthetic approach, which was further
elucidated by density functional theory (DFT) studies. The reactivity
of 1 towards various small molecules was probed and compared with
the previously published derivative Ph3PC(Me)BEt2 (2). Both α-BCPs
react with NH3 to undergo heterolytic N–H bond cleavage. Different
dimeric and trimeric ring structures were observed in the reaction
products of 1 with CO (3) and CO2 (4). With PhNCO and PHNCS, the
expected insertion products [Me3PC(H)(PhNCO)B(iBu)2] (5) and
[Me3PC(H)(PhNCO)B(iBu)2] (6) were isolated.
In order to probe whether the reactivity of α-BCPs can be modified
by changing the substituent pattern, we became interested to
study α-BCPs with small Me substituents on the phosphorus atom.
Introduction
Since the discovery of the activation of dihydrogen by a main
group element compound by Power et al. in 2005,[1] and the
reversible cleavage of dihydrogen by Stephan et al. in 2006,[2] the
field of main group element-based molecules mimicking transition
metal chemistry – e.g. small molecule activation – is quickly
developing.[3] The most prominent group of compounds are the so
called “frustrated Lewis pairs” (FLPs) in which a Lewis acid and a
Lewis base are hindered of combining inter- or intramolecularily.[4]
However, FLP-type reactivity is not only observed for unquenched
Lewis pairs. For instance, carbenes inherently featuring
ambiphilic character are also able to react with e.g. H2 or NH3.[5]
Heteroalkenes possessing perturbed element element double
bonds also show FLP-type reactivity towards small molecules.[6]
Stephan et al. reported already in 2008 on the addition of H2 to a
phosphinoborane (Scheme 1).[6h] Recently, it has been
demonstrated that conjugated, boron substituted multiple bonds
show ambiphilic reactivity.[7] In this line of thought, Stephan and
Erker lately pointed out that “borate alkenes can be viewed as
FLPs with adjacent donor and acceptor sites”.[4e, 8] Our group
recently reported on an α-borylated phosphorus ylide (α-BCP)[9]
featuring a highly polarized borata alkene subunit.[10a] We found
that the α-BCP readily reacts with CO, CO2, COS, CS2, PhNCO
and PhNCS (Scheme 1).[10a]
Scheme 1. Structure and reactivity of selected heteroalkenes.
Results and Discussion
We first targeted the smallest possible α-BCP, that is the all-Me
substituted derivative Me3PC(H)BMe2. However, transylidation[11]
of Me3PC(H)2B(Br)Me2 with Me3PCH2 did not lead to the desired
target structure, at least in our hands. The main product of the
reaction was found to be the eight-membered ring [H2C–PMe2–
CH2–BMe2]2. During our studies on phosphorous ylides we found
by chance that the reaction of iBu2B–P(tBu)2 with Me3PCH2 yields
Me3PC(H)B(iBu)2 (1, Scheme 2). The starting material iBu2B–
P(tBu)2 was generated in situ in order to prevent isobutene
elimination. The expected intermediate was isolated and we
successfully obtained NMR spectroscopic evidence for the four-
membered PC2B ring structure, which is known from the
literature.[12] The NMR measurement was conducted in toluene-
d8 at -60 °C. The 31P{1H} resonance is detected at δ = 27.6 ppm,
shifted about 25 ppm downfield compared to 1. The 11B NMR
resonance with a chemical shift of δ = –10.9 ppm is about 60 ppm
upfield compared to 1. Overall, the chemical shifts fit perfectly to
the inner salt character of the four-membered ring structure. The
1H NMR resonances are detected at δ = 0.60 ppm (2JPH = 13.1
Hz, 6H) for the hydrogen atoms of the P-bound methyl groups and
at 0.43 ppm (2JPH = 14.6 Hz, 4H) for the bridging CH2 groups. The
[a]
M.Sc. M. Radius, Dr. E. Sattler, H. Berberich, Prof. Dr. F. Breher
Institute of Inorganic Chemistry, Division Molecular Chemistry
Karlsruhe Institute of Technology (KIT)
Engesserstr. 15, 76131 Karlsruhe (Germany)
E-mail: breher@kit.edu
Supporting information and the ORCID identification number(s) for
the author(s) of this article can be found under:
https ://doi.org/10.1002/chem.xxx
1
couplings collapse if the H NMR spectrum is recorded with 31P
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Figure 1. Calculated [BP86/(ri-)def2-SVP] reaction pathway, electronic energies (in red) and Gibbs free energies (in blue) to 1. The free energies are calculated at
233.15 K.
1
decoupling. We note in passing that the H NMR resonances of
the iBu substituents are not perfectly isochrone, probably due to
the possible endo/exo positions (cf. the structure of the quantum
chemical calculation).
coordination of the ylide to the boron atom and formation of P1 is
slightly exergonic (–4 kJ mol–1, Figure 1). The energy barrier to
the six-membered ring that comprises the transition state for the
proton shift from the methyl group to the phosphorus atom
(product P2) was found to be only 27.9 kJ mol–1 and, thus, quite
low. The subsequent dissociation of tBu2PH is nearly without an
energy barrier. The formations of the PC2B four-membered ring
compound P3 and the open α-BCP structure P4 (i.e. 1) are both
highly exergonic (–119.8 and –136.6 kJ mol–1, respectively). The
rearrangement to the α-BCP 1 can proceed either inter- or
intramolecularily. Overall, these calculated Gibbs free energies
are in good agreement with the reaction conditions.
Further quantum chemical calculations revealed a very similar
electron distribution for 1 as compared to the previously reported
derivative Ph3PC(Me)BEt2 (2).[10a] The calculated frontier orbitals
are depicted in Figure 2 showing the HOMO to comprise mainly
of the p-type C-based lone pair of electrons with a smaller
coefficient on the boron atom. The LUMO mainly comprises of the
vacant p orbital on boron and partly the antibonding P–CMe
orbitals.
Scheme 2. Synthesis of 1.
Since ylides are very strong s-donors,[13] an initial coordination to
the Lewis acidic boron atom of iBu2B–P(tBu)2 is very likely. In
order to shed some light on the reaction mechanisms for the
formation of 1, we calculated the reaction pathway of the
deprotonation of Me3P=CH2 and the formation of a four-
membered ring (Figure 1). The Gibbs free energy for the
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phosphorus atom is significant. This may be due to the higher
Lewis acidity of the PR1 fragment because of lowering of the
3
σ*(P–C) orbitals. These trends correlate well with the group
electronegativity (increasing from Me via Et and iPr to Ph) of the
substituents.[15] Interestingly, the calculated C–B bond lengths
remain almost the same for the whole series of model compounds.
Figure 2. Kohn-Sham HOMO and LUMO of 1 (BP86/def2-TZVPP, isosurface
value of 0.06).
Table 1. Calculated [BP86/def2-SV(P)] fluoride ion affinity (FIA) and C–B bond
lengths for different model compounds.
As for 2, we calculated the fluoride ion affinity (FIA)[14] of 1
(BP86/def2-SVP). The FIA of 1 was found to amount to 196 kJ
mol–1, i.e. ca. 30 kJ mol–1 lower than 2 (224 kJ mol–1). The main
difference in the electronic structure is caused by the substitution
of the Cylide-hydrogen in 1 by the CH3 group in 2. This becomes
clear when the charges of the natural population analysis are
compared. To this end, we calculated the charges for the model
compounds q1H, q2Me and the hypothetical molecules q1Me and
q2H with Me and H substituents on the ylidic carbon atoms,
respectively (Scheme 3).
Entry
Compound
FIA
d(C–B) [pm]
1
2
3
4
5
6
7
8
Me3PC(Me)BMe2 (qMeMe)
Me3PC(Me)BEt2 (qMeEt)
Me3PC(Me)B(iPr)2 (qMePr)
Me3PC(Me)BPh2 (qMePh)
Et3PC(Me)BMe2 (qEtMe)
iPr3PC(Me)BMe2 (qPrMe)
Ph3PC(Me)BMe2 (qPhMe)
Ph3PC(Me)BPh2 (qPhPh)
165
197
221
220
181
196
226
267
151.0
150.8
151.5
150.3
151.1
151.4
151.6
150.8
In order to probe the reactivity of 1, we performed reactions with
various small molecules. As with Ph3PC(Me)BEt2,[10a] 1 does not
react with dihydrogen but the reaction with NH3 possessing a
relatively strong N–H bond (D = 446 kJ mol-1),[16] smoothly
proceeds at room temperature with both ylides 1 and 2. The
corresponding ylide and the amidoborane R2B–NH2 are formed
(Scheme 4), as evidenced by 11B and 31P NMR spectroscopic
investigations. The 31P{1H} NMR chemical shifts clearly indicate
the formation of the ylides. The 11B NMR resonances are shifted
upfield from 56.5 to 48.7 ppm for 2 and from 54.7 ppm to 47.6
ppm for 1, respectively, perfectly matching literature values for
R2B–NH2.[17]
Scheme 3. Natural population analysis charges (BP86/def2-SVP) of q1H, q1Me
q2H and q2Me
,
.
Although the charges on the boron and phosphorus atoms do not
change significantly, the charges on the ylidic carbon atoms for
the model compounds bearing a Cylide–H bond (q1H, q2H) are
more negative (–0.25 e) than for the two methylated analogous
q1Me and q2Me. It appears that this higher charge density is partly
responsible for the lower FIA calculated for 1 and has its origin in
the inability of the H-substituent to participate in negative
hyperconjugation. Nevertheless, the higher charge is not reflected
in the Wiberg bond indices (WBI). The WBIs of the P–Cylide and
the Cylide–B bonds in 1 are calculated to amount to 1.28 and 1.41,
respectively, and are thus very similar to 2 (P–Cylide: 1.25, Cylide
–
Scheme 4. Reaction of 1 and 2 with NH3 at room temperature.
B: 1.42).[10a]
To further elucidate the influence of the other B- and P-bound
substituents, we calculated the FIA for several additional model
compounds (qR1R2 with R1 bound to the phosphorus atom and R2
bound to the boron atom; R1/R2 = Me, Et, iPr, Ph; Table 1). From
this study it becomes clear that for small alkyl substituents such
as Me on boron the FIA is obviously reduced (hyperconjugative
effects). A further increase of the degree of alkylation upon going
from qMeMe to qMeEt to qMePr gradually increases the FIA from
171 to 195 to 219 kJ mol–1, respectively. Aryl groups such as Ph
further increase the FIA to 229 kJ mol–1 (cf. qMePh, entry 4). The
highest FIA was found for the all-Ph derivative qPhPh (entry 8,
258 kJ mol–1). Also, the influence of the substituents on the
It has to be noted that precedents for such a reactivity have been
published before for dialkyl boron compounds. The splitting of
NH3 under formation of R2B–NH2 takes place in boron compounds
featuring Lewis basic substituents such as R2B–SEt or with
[18]
tBuC(O)O–BEt2.
1 reacts at elevated temperatures with CO in toluene. However,
the structure of the product (3) differs from that found for 2. While
the latter forms a dimeric structure (Scheme 5), 1 forms an adduct
with another equivalent of α-BCP.
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for the local geometry of an ylidic carbon atom in solution or the
gas phase. Indeed, we detected in solution two well-separated
chemical shifts for H1 and P2 in the 1H and 31P NMR spectrum,
respectively, both integrating 1:1 (Figure 4). This can most likely
be attributed to the presence of two diastereomers, i.e. a second
stereocenter besides the one at C2 depicted in Figure 4. This
suggests that the local geometry of the ylidic carbon atom is not
planar but (slightly) pyramidal,[20] thus providing a second
stereocenter at C1. Interchange of one diastereomer into another
via pyramidal inversion at C1 leads naturally to the uniformly
distributed intensities (1:1).[21]
Scheme 5. Reaction of 1 with CO to 3 and comparison with the reactivity found
for 2.[10a]
Single crystals of 3 suitable for X-ray diffraction studies were
obtained from hexane solution at room temperature (Figure 3).
The space group for 3 was found to be P21/c and since 3
comprises a stereocenter at C2, both enantiomers are present in
the solid state. The core structure is composed of a five-
membered C2OB2 heterocycle with C2 residing ca. 15° above the
plane spanned by the atoms B2, C3, O1 and B1. The P2–C2 bond
length of 1.716 Å falls in the typical range for stabilized ylidic
bonds.[10a] The analogous P1–C1 bond (1.742 Å) is slightly
elongated. As expected, the distances C1–C3 (1.404 Å) and C3–
O1 (1.329 Å) fall in between typical single and double bond
lengths. The carbon–boron bond lengths are in the expected
range.
Figure 4. Sections of the 1H and 31P{1H} NMR spectra of 3. Atom numbering in
the schematic drawing according to Figure 3.
The different reactivity of 1 towards CO as compared to 2 may at
least in part be explained by the lower FIA of 1. Quantum chemical
calculations predicted the insertion/ylide adduct 3 to be 38 kJ mol-
1
more stable than the hypothetical dimeric insertion product
found for 2.
Scheme 6. Reaction of 1 with CO2 to 4 and comparison with the reactivity found
for 2.
Figure 3. ORTEP view (30% probability ellipsoids) of 3. Hydrogen atoms
(except H1 and H2) and the C(H)Me2 part of the iBu groups are omitted for
clarity. Only the main part of the disordered structure is depicted. Selected bond
lengths (Å) and angles (°): P1–C1 1.716(5), P2–C2 1.742(4), C1–C3 1.404(8),
C3–O1 1.329(7), C3–B2 1.625(7), C2–B2 1.689(6), C2–B1 1.673(5), B1–O1
1.556(5), C3–C1–P1 121.7, O1–C3–C1 114.4(5), C1–C3–B2 129.2(5), B1–C2–
B2 105.7(3).
The reactivity of 1 towards CO2 has also been investigated. Again,
the product (4) differs considerably from the product observed for
2 with CO2 (Scheme 6). Interestingly, the reaction product is
formed by three α-BCPs and four CO2 molecules. Two molecules
of 1 directly react with CO2, each of which with two molecules of
CO2. Six-membered ring structures of the insertion products are
formed, both of which are deprotonated by the third molecule of 1
forming [PMe4]+ and a {B(iBu)2}+ fragment. The latter is attached
to the newly formed six-membered rings furnishing an overall
negatively charged borate. Thus, as in the reaction product of 2
The ylidic carbon atom C1 adopts a trigonal planar coordination
environment in the crystal structure. However, as Mitzel et al.
reported,[19] the solid-state structure is not always representative
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with CO2, the boron atoms are saturated by binding to two oxygen
atoms. In the reaction of 2 with CO2, however, the methyl group
inhibits further reaction like the one displayed by 1.
We note in passing that the reaction products 5 and 6 thermally
decompose easily. In the case of 5, above ca. 60 °C, and in the
case of 6 at slightly higher temperatures at 89 °C. This may be
due to the higher ring strain in the small NBOC four-membered
ring of 5 as compared to the widened NBSC ring of 6.
Single crystals of 5 (space group P21/n) and 6 (space group P-1)
suitable for X-Ray diffraction studies were obtained from benzene
toluene/pentane, respectively. The molecular structures are
depicted in Figure 6 and the bond lengths and angles are very
similar to published values. An interesting structural feature of 6
is the exceptional long B1–S1 bond length of 2.082 Å, which
indicates the formation of a weak B1…S1 contact instead of a
strong bond. The corresponding bond length B1–O1 in 5 (1.593
Å) is slightly elongated compared to the boron oxygen bonds in 3
and 4 (1.54 – 1.56 Å). These structural features, together with the
low decomposition temperature, clearly support the view of
strained four-membered rings. The NMR spectra of 5 and 6 are
very similar (see Experimental Section).
Figure 5. ORTEP view (30% probability ellipsoids) of 4. Hydrogen atoms and
the C(H)Me2 part of the iBu groups are omitted for clarity. Only the main part of
the disordered structure is depicted. Selected bond lengths (Å) and angles (°)
(The structural parameters of only one half of the anion is given since the
second half is metrically similar.): P1–C1 1.74(1), C1–C2 1.439(3), C1–C3
1.406(3), C2–O1 1.241(2), C2–O2 1.304(2), C3–O3 1.284(2), C3–O4 1.288(2),
B1–O2 1.520(3), B1–O3 1.539(3), B2–O4 1.546(2), C2–C1–C3 120.2(2).
Single crystals of 4 suitable for X-ray diffraction studies were
obtained from toluene at room temperature (space group P-1,
Figure 5). The structural parameters of only one half of the anion
is discussed since the second half is metrically similar. The Me4P+
cation shows the expected structural parameters.[22] Although the
C1–C2 bond length of 1.439 Å is slightly longer than the
corresponding C1–C3 bond of 1.406 Å, both still adopt values
between C–C single and double bonds. The carbon oxygen
distances range from 1.241 Å for C2–O1 to 1.304 Å for C2–O2.
The phosphorous carbon bond length P1–C1 (1.744 Å) indicates
a small ylidic contribution. All B–O distances are in the expected
range.[23]
The NMR spectroscopic characterization fully supported the
structure of 4 found in the solid state. For instance, two well-
separated 13C NMR chemical shifts are found for the CCO2
entities at δ = 174.0 and 171.8 ppm. In the 11B NMR spectrum
only one broad resonance is detected at δ = –14.9 ppm. Although
the bridging boron moiety (B2) and the boron moieties in the six
membered rings possess slightly distinct environments, the
differences are probably not significant enough to cause to furnish
two distinct 11B NMR shifts.
Figure 6. ORTEP view (30% probability ellipsoids) of 5 and 6. Hydrogen atoms
(except the ylidic) are omitted for clarity. Selected bond lengths (Å) and angles
(°): 5: P1–C1 1.723(2), C1–C2 1.376(2), N1–C2 1.353(2), O1–C2 1.331(2), N1–
B1 1.603(2), O1–B1 1.593(2), P1–C1–C2 119.2(1), N1–C2–O1 101.3(1), C2–
N1–B1 88.0(1), C2–O1–B1 89.2(1), N1–B1–O1 81.0(1). 6: P1–C1 1.720(2),
C1–C2 1.378(3), N1–C2 1.349(2), S1–C2 1.752(2), N1–B1 1.585(3), S1–B1
2.082(2), P1–C1–C2 124.58(15), N1–C2–S1 102.5(1), C2–N1–B1 102.6(1),
C2–S1–B1 72.92(8), N1–B1–S1 81.9(1).
Conclusions
The α-BCP 1 reacts also with PhNCO and PhNCS. The reaction
products are analogous to the ones observed for 2. In each case,
one PhNCX molecule inserts into the Cylidic–B bond of one α-BCP
and the boron atom is chelated by the nitrogen and the chalcogen
atoms (Scheme 7).[10a]
In conclusion, we note that the fundamental reactivity of an α-BCP
is untouched by the substitution of the P-bound phenyl groups by
methyl groups and reactions occur with NH3, CO, CO2, PhNCO
and PhNCS. However, in the case of CO and CO2, different
products and structures are observed for Me3PC(H)B(iBu)2 (1) as
compared to the previously published derivative Ph3PC(Me)BEt2
(2). In part, the different reaction patterns can be explained by
different fluoride ion affinities of both α-BCPs. Nevertheless, also
the presence of a Cylide–H bond in 1 is responsible for secondary
reactions arising from this reactive functional group.
Scheme 7. Reaction of 1 with PhNCO and PhNCS to 5 and 6.
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6.6 Hz, HiBuCH3, 3H), 1.37 (d, 3JHH = 6.6 Hz, HiBuCH3, 3H), 1.34 (d, 3JHH = 6.6
Hz, HiBuCH3, 3H), 1.29 (d, 3JHH = 6.5 Hz, HiBuCH3, 3H), 1.29 (d, 3JHH = 6.5 Hz,
HiBuCH3, 3H), 1.28 (d, 3JHH = 6.5 Hz, HiBuCH3, 3H), 1.14 (dd, 2JHH = 14.2 Hz,
Experimental Section
All operations were conducted under a dry argon atmosphere using
standard Schlenk and glovebox techniques. Solvents were dried rigorously
and degassed before use. Me3P=CH2,[24] iBu2BCl[25] and LiP(tBu)2[26] were
synthesized according to literature procedures. The chemical shifts are
expressed in parts per millions and 1H and 13C signals are given relative
to TMS. Coupling constants J are given in Hertz as positive values
regardless of their real individual signs. The multiplicity of the signals is
indicated as s, d, q, sept or m for singlets, doublets, quartets, septets or
multiplets, respectively. The assignments were confirmed as necessary
with the use of 2D NMR correlation experiments. Mass spectrometry
measurements were performed on an Advion expressionL CMS mass
spectrometer under atomic pressure chemical ionization (APCI). IR
spectra were measured with a Bruker Alpha spectrometer using the
attenuated total reflection (ATR) technique on powdered samples, and the
data are quoted in wavenumbers (cm–1). The intensity of the absorption
band is indicated as vw (very weak), w (weak), m (medium), s (strong), vs.
(very strong) and br (broad). Melting points were measured with a Thermo
Fischer melting point apparatus and are not corrected. Elemental analyses
were carried out in the institutional technical laboratories of the Karlsruhe
Institute of Technology (KIT).
3JHH = 7.5 Hz, HiBuCH2, 1H), 1.08 (dd, 2JHH = 13.7 Hz, 3JHH = 5.5 Hz, HiBuCH2
1H), 1.00 (d, 2JPH = 12.5 Hz, HBCPMe3, 9H), 0.92 (dd, 2JHH = 12.5 Hz, 3JHH
,
=
5.1 Hz, HiBuCH2, 1H), 0.85 (dd, 2JHH = 12.9 Hz, 3JHH = 6.1 Hz, HiBuCH2, 1H),
0.89 (d, 2JPH = 13.5 Hz, HCCPMe3, 9H), 0.63 (dd, 2JHH = 14.1 Hz, 3JHH = 3.7
Hz, HiBuCH2, 1H), 0.54 (dd, 2JHH = 14.2 Hz, 3JHH = 4.7 Hz, HiBuCH2, 1H), 0.36
2
3
2
(dd, JHH = 12.8 Hz, JHH = 5.0 Hz, HiBuCH2, 1H), 0.32 (d, JPH = 22.8 Hz,
HBC(H)P,1H), 0.31 (dd, 2JHH = 12.2 Hz, 3JHH = 5.1 Hz, HiBuCH2, 1H); 11B NMR
(96 MHz, C6D6, ppm): δ = 7.2 (bs), –9.4 (s); 13C{1H} NMR (75 MHz, C6D6,
ppm): δ = 231.9 (bs, CCO), 59.3 (d, 1JCP = 88.2 Hz, CPCC), 40.2 (bs, CiBuCH2),
29.6 (s, CiBuCH3), 29.1 (s, CiBuCH3), 29.0 (s, CiBuCH3), 28.9 (s, CiBuCH3), 28.6
(s, s, CiBuCH), 28.6 (s, CiBuCH3), 27.7 (s, CiBuCH3), 27.0 (s, CiBuCH), 27.0 (s,
1
CiBuCH), 26.9 (s, CiBuCH3), 15.4 (d, JPC = 52.1 Hz, CBCPMe), 14.6 (bs, CBCP
)
12.4 (d, 1JPC = 58.0 Hz, CCCPMe); 31P{1H} NMR (121 MHz, C6D6, ppm): δ =
22.8 (s,Pdiastereomer1_BCP), 22.7 (s, Pdiastereomer2_BCP), -4.23 (s, PCCP); APCI-
MS: decomposition; melting point: 181° C; elemental analysis:
C25H56B2OP2 calc. C 65.81; H 12.37; found. C 65.64; H 12.32; IR (ATR,
cm-1): ῦ = 2936 (m), 1893 (w), 2850 (s), 2802 (w), 1451 (m), 1437 (s), 1356
(vw), 1331 (w), 1311 (w), 1288 (m), 1242 (w), 1159 (w), 1132 (w), 1107
(m), 1077 (m), 970 (s), 944 (vs), 907 (s), 861 (s), 823 (m), 748 (vs), 718
(s), 691(vs),648 (m), 620 (m), 602 (m), 574 (m), 546 (s), 525 (vs), 497 (s),
485 (s), 469 (m), 459 (m), 449 (m), 440 (m), 430 (s), 421 (s), 410 (m), 401
(m), 392 (m), 382 (m).
Synthesis of 1. To a solution of iBu2BCl (7.67 g, 47.8 mmol) in 200 ml
pentane was slowly added a suspension of LiP(tBu)2 (7.61 g, 50.0 mmol)
in 200 ml pentane at –50 °C. After stirring the suspension at –40 °C for 48
hours the suspension was filtered in the cold and washed with cold
pentane. The residue was extracted with cold toluene. At –50 °C to this
solution was added a solution of Me3P=CH2 (1.85 g, 20.5 mmol) in 50 ml
pentane. White precipitate formed. After cold filtration the precipitate was
washed with cold pentane. (From this precipitate, the NMR spectra of
Me2P(CH2)2B(iBu)2 were measured.) At room temperature, the solid turned
4: A solution of 700 mg (3.27 mmol) of 1 in 10 ml toluene was degassed
with two freeze-pump-thaw cycles and subsequently purged with 1.1 bar
CO2. The solution was stirred and heated to 90 °C overnight. The solvent
and all volatile compounds were evaporated in high vacuum. After
removing all volatiles, the crude product was only slightly soluble in toluene.
Crude 4 was recrystallized in toluene, yielding after removal of the
supernatant layer and drying in high vacuum 538 mg (0.657 mmol, 60 %)
colourless crystalline 4. Crystals suitable for X-ray diffraction were
obtained by solving a small amount of 4 in hot toluene and cooling the
solution very slowly to room temperature: 1H NMR (300 MHz, THF-d8,
liquid. Distillation at high vacuum (p = 3 · 10-6 bar) at 20 °C yields 1 (2.01
g, 9.39 mmol, 52%): 1H NMR (300 MHz, C6D6, ppm): δ = 2.36 (d, JPH
=
2
3
12.1 Hz, Hylid, 1H), 2.26 (nonet, JHH = 6.7 Hz, HiBuCH, 2H), 2.21 (nonet,
3JHH = 6.7 Hz, HiBuCH, 2H), 1.28 (d, 3JHH = 6.8 Hz, HiBuCH2, 2H), 1.27 (d, 3JHH
2
2
ppm): δ = 2.03 (d, JPH = 15.2 Hz, HPMe3, 12H), 1.80 (d, JPH = 14.1 Hz,
= 6.5 Hz, HiBuCH3, 6H), 1.16 (d, 3JHH = 6.5 Hz, HiBuCH3, 6H), 1.12 (d, 3JHH
=
=
3
HPMe4, 18H), 1.76 – 1.65 (m, HiBuCH_ring, 4H) ,1.59 (sept, JHH = 6.5 Hz,
3
2
7.2 Hz, HiBuCH2, 1H), 1.12 (d, JHH = 7.2 Hz, HiBuCH2, 1H), 0.86 (d, JPH
HiBuCH_bridge, 2H), 0.86 (d, J = 6.5 Hz, HiBuCH3_ring, 24H), 0.84 (d, J = 6.5 Hz,
HiBuCH3_bridge, 12H), 0.66 (d, J = 6.9 Hz, HiBuCH2_bridge, 4H) 0.28 (bs,
HiBuCH2_ring, 8H). 11B NMR (96 MHz, THF-d8, ppm): δ = –14.9 (bs); 13C{1H}-
NMR (101 MHz, THF-d8, ppm): δ = 174.0 (bs, CCO2), 171.8 (bs, CCO2), 57.5
(d, 1JPC = 128 Hz, CPCCO) 35.2 (bs, CiBuCH2_ring), 32.6 (bs, CiBuCH2_bridge), 27.9
(s, CiBuCH3_ring), 27.0 (s, CiBuCH3_bridge), 27.0 (s, CiBuCH_bridge), 26.5 (s,
CiBuCH_ring), 13.9 (d, JPC = 62.0 Hz, CPMe3), 9.9 (d, JPC = 44.8 Hz, CPMe4);
31P{1H} NMR (121 MHz, THF-d8, ppm): δ = 25.7 (s, PMe4), 9.9 (s, Pylid);
APCI-MS: decomposition; melting point: 174 °C (decomp.); elemental
analysis (%): C40H84B3O8P3 calc. C, 58.70, H, 10.35 found C, 58.34, H,
10.73; IR (ATR, cm-1): ῦ = 2983 (vw), 2937 (w), 2854 (w), 2792 (vw), 1592
(m), 1579 (m), 1490 (vs), 1452 (vs), 1407 (m), 1373 (vw), 1356 (vw), 1318
(m), 1291 (w), 1245 (m), 1179 (w), 1100 (m), 1058 (w), 982 (s), 964 (s),
947 (s), 898 (w), 865 (w), 840 (m), 816 (w), 789 (m), 756 (m), 729 (vw),
681 (m), 629 (vw), 585 (w), 534 (vw), 506 (vw), 464 (w), 419 (vw), 404 (vw).
12.6 Hz, HPMe3, 9H); 11B-NMR (96 MHz, C6D6, ppm): δ = 54.7 (s); 13C{1H}
NMR (75 MHz, C6D6, ppm): δ = 48.5 (bs, Cylid), 37.2 (bs, CiBuCH2), 36.0 (bs,
CiBuCH2), 27.3 (s, CiBuCH1), 27.3 (s, CiBuCH1), 26.7 (s, CiBuCH3), 26.7 (s,
1
CiBuCH2), 17.6 (d, JPC = 56.2 Hz, CPMe3); 31P{1H} NMR (121 MHz, C6D6,
ppm): δ = 2.03 (s); EI-MS: 214.20214, C12H2811BP, calc. 214.20216;
elemental analysis (%): C12H28BP calc. P, 14.46, B, 5.05 found P, 14.40,
B, 5.08; cryoscopy (benzene, g mol–1): calc. 214.14, found 212.0; IR (ATR,
cm-1): ῦ = 2944 (m), 2891 (w), 2860 (m), 1461 (w), 1419 (w), 1375 (m),
1347 (vs), 1315 (s), 1289 (m), 1250 (w), 1207 (vw), 1155 (w), 1091 (vw),
1056 (vw), 1034 (vw), 980 (s), 936 (s), 890 (w), 858 (w), 816 (w), 750 (w),
731 (m), 697 (w), 647 (vw), 577 (vw), 500 (vw), 412 (vw).
1
1
Synthesis of 3: A Schlenk tube with a solution of 0.864 g (1.00 ml, 4.03
mmol) 1 in 10 ml toluene was degassed with two freeze-pump-thaw cycles
and subsequently purged with CO. The reaction mixture was stirred and
heated to 70 °C for three hours. The solution was evaporated to dryness.
Pentane (20 ml) was added to the residue, yielding a thin suspension. The
suspension was filtered. The filtrate was reduced until crude 3 precipitates.
Recrystallisation in boiling pentane, taking of the supernatant layer and
drying in high vacuum yielded 250 mg (0.548 mmol, 14 %) pure 3 (both
diastereomers) as colourless crystals. Suitable crystals for X-ray diffraction
were obtained by solving 3 in a small amount of boiling hexane and cooling
5: A solution of 500 mg 1 in 8 ml hexane and a solution of 258 mg (2.16
mmol) PhNCO in 8 ml hexane were combined under stirring at room
temperature. Stirring was discontinued and crude 5 crystallised. After one
hour reaction time, the supernatant layer was taken off and the colourless
crystals were dried in high vacuum. The crude product was solved in
benzene and filtered. Evaporation of the solvent and drying in high vacuum
yielded 282 mg (0.846 mg, 39 %) pure 5. Crystals suitable for X-ray
diffraction were obtained by slow solvent evaporation of a benzene
the solution very slowly to room temperature: 1H NMR (signal assignment
2
where necessary with 1H{11B}) (300 MHz, C6D6, ppm): δ = 3.54 (d, JPH
=
,
solution of 5: 1H NMR (300 MHz, C6D6, ppm): δ = 7.28 – 7.26 (m, Hortho/meta
,
2
32.1 Hz, Hdiastereomer1_C=C, 0.5H), 3.53 (d, JPH = 32.1 Hz, Hdiastereomer2_C=C
2
4H), 6.92 – 6.83 (m, Hpara, 1H), 2.62 (d, JPH = 18.2 Hz, Hylide, 1H), 2.15
0.5H), 2.35-2.17 (m, HiBuCH1, 2H), 2.04-1.82 (m, HiBuCH1, 2H), 1.46 (d, 3JHH
= 6.5 Hz, HiBuCH3, 3H) , 1.43 (d, 3JHH = 6.6 Hz, HiBuCH3, 3H), 1.37 (d, 3JHH
(sept, 3JHH = 6.6 Hz, HiBuCH, 2H), 1.29 (d, 3JHH = 6.6 Hz, HiBuCH3, 12H), 1.16
=
(d, JHH = 6.6 Hz, HiBuCH2, 4H), 0.75 (d, JPH = 13.6 Hz, 9H); 11B NMR (96
3
2
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10.1002/chem.201902681
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FULL PAPER
MHz, C6D6, ppm): δ = 16.5 (bs); 13C{1H} NMR (75 MHz, C6D6, ppm): δ =
µ(MoKa) = 0.148, 28135 reflections measured, 15190 unique (Rint
0.0273) which were used in all calculations. The final wR2 was 0.1634 (all
data) and R1 was 0.0523 (I > 2(I)).
=
2
171.2 (d, JPC = 4.7 Hz, CNCO), 143.1 (s, Cipso), 129.3 (s, Cmeta/para), 120.5
1
(s, Cpara), 118.0 (s, Cmeta/para), 35.3 (d, JPC = 115.8 Hz, Cylid), 34.1 (bs,
CiBuCH2), 27.3 (s, CiBuCH3), 26.3 (s, CiBuCH1f), 12.6 (d, 1JPC = 60,7 Hz, CMeP);
31P{1H} NMR (121 MHz, C6D6, ppm): δ = 6.2 (s); APCI-MS: decomposition;
melting point: 62 °C (decomposition); elemental analysis (%):
C19H33BNOP calc. C, 68.48, H, 9.98, N, 4.20 found C, 68.31, H, 9.75, N,
4.28. IR (ATR, cm-1): ῦ = 2942 (vw), 2859 (vw), 1601 (vw), 1573 (vw), 1542
(vs), 1502 (m), 1449 (vw), 1419 (w), 1402 (w), 1374 (vw), 1359 (vw), 1322
(vw), 1308 (vw), 1292 (w), 1253 (vw), 1241 (w), 1165 (vw), 1108 (w), 1075
(vw), 1027 (m), 972 (s), 948 (s), 896 (vw), 880 (vw), 866 (vw), 819 (vw),
806 (vw), 752 (m), 733 (w), 692 (s), 662 (vw), 598 (vw), 570 (vw), 504 (m),
434 (vw).
Crystal Data 5. C19H33BNOP, Mr = 333.24, monoclinic, P21/n (No. 14), a =
11.900(2) Å, b = 13.558(3) Å, c = 12.590(3) Å, b = 95.70(3)°, a = g = 90°,
V = 2021.2(7) Å3, T = 200 K, Z = 4, Z' = 1, µ(MoKa) = 0.140, 14929
reflections measured, 5455 unique (Rint = 0.0579) which were used in all
calculations. The final wR2 was 0.1109 (all data) and R1 was 0.0467 (I >
2(I)).
Crystal Data 6. C19H33BNPS, Mr = 349.30, triclinic, P-1 (No. 2), a =
9.5890(19) Å, b = 10.106(2) Å, c = 11.551(2) Å, a = 86.62(3)°, b =
79.45(3)°, g = 71.20(3)°, V = 1041.7(4) Å3, T = 200 K, Z = 2, Z' = 1,
µ(MoKa) = 0.232, 11612 reflections measured, 5572 unique (Rint = 0.0360)
which were used in all calculations. The final wR2 was 0.1460 (all data)
and R1 was 0.0429 (I > 2(I)).
6: A solution of 250 mg (1.16 mmol) 1 in 5 ml toluene was slowly added to
a solution of 150 mg (1.16 mmol) PhNCS in 5 ml toluene under vigorous
stirring. The solution turned slowly yellow. The solution was stirred at room
temperature overnight and subsequently all volatile compounds removed
in vacuo. The orange residue was solved in 2 ml toluene and layered with
15 ml pentane. After diffusion the solution was filtered off the resulting
precipitate. The precipitate was washed three times, each with 15 ml
pentane. The precipitate was dissolved in 1 ml toluene and layered with
15 ml pentane. After diffusion, the supernatant layer was removed and the
residue was dried in vacuo. This procedure yielded 73 mg (0.21 mmol,
Crystallographic data (excluding structure factors) for the structures
reported in this paper have been deposited with the Cambridge
Crystallographic Data Centre as a supplementary publication no. CCDC-
1920465-1920468.
18%) yellow crystals: 1H NMR (400 MHz, C6D6, ppm): δ = 7.57 – 7.54 (m,
3
Hortho, 2H), 7.26 – 7.21 (m, Hmeta, 2H), 6.92 (tt, JHH = 7.5, 1.1 Hz, Hpara
,
Acknowledgments
1H), 3.55 (d, Hylid, 1H), 2.37 (nonet, 3JHH = 6.6 Hz, HBu-CH, 1H), 2.35 (nonet,
3JHH = 6.6 Hz, HBu-CH, 1H), 1,40 (d, 3JHH = 6.3 Hz, HBu-CH2), 0.78 (d, 3JHH
=
We gratefully acknowledge Dr. Christopher E. Anson and M. Sc.
Hanna Wagner for their help with the crystal structures. We also
gratefully acknowledge M.Sc. Wolfram Feuerstein for carefully
reading the manuscript.
13.4 Hz, HP-Me); 11B NMR (96 MHz, C6D6, ppm): δ = 15.1 (s); 13C{1H} NMR
(101 MHz, C6D6, ppm): δ = 175.8 (d, 2JPC = 13.6 Hz, CNCS), 144.9 (s, Cipso),
129.1 (s, Cmeta), 122.8 (s, Cpara), 122.7 (s, Cortho), 49.6 (d, 1JPC = 122.6 Hz,
Cylid), 36.26 (bs, CBu-CH2), 27.6 (s, CiBuCH), 27.2 (s, CiBuCH3), 12.2 (d, 1JPC
=
60.8 Hz, CP-Me); 31P{1H} NMR (162 MHz, C6D6, ppm): δ = 5.5 (s); APCI-
MS: decomposition; melting point: 89 °C (decomp.); elemental analysis
(%): C19H33BNPS calc. S 9.18; N 4.01; C 65.33; H 9.52 found S 8.78; N
4.02; C 64.98; H 9.23; IR (ATR, cm-1): ῦ = 2949 (w), 2911 (vw), 2863 (vw),
1594 (w), 1493 (s), 1405 (m), 1304 (m), 1260 (w), 1163 (s), 1100 (vs), 979
(vs), 905 (m), 757 (m), 740 (w), 695 (vs), 670 (w), 605 (w), 605 (w), 567
(w), 541 (w), 529 (m), 484 (s), 474 (vs), 464 (vs), 456 (vs), 444 (s), 427
(m), 414 (m), 399 (m), 388 (m), 380 (vw).
Keywords: ylides • boranes • phosphorus • small ring systems •
quantum chemistry
[1]
[2]
[3]
G. H. Spikes, J. C. Fettinger, P. P. Power, J. Am. Chem. Soc. 2005, 127,
12232-12233.
G. C. Welch, R. R. S. Juan, J. D. Masuda, D. W. Stephan, Science 2006,
314, 1124.
a) R. L. Melen, Science 2019, 363, 479; b) M.-A. Légaré, C.
Pranckevicius, H. Braunschweig, Chem. Rev. 2019; c) T. Chu, G. I.
Nikonov, Chem. Rev. 2018, 118, 3608-3680; d) M.-A. Légaré, G.
Bélanger-Chabot, R. D. Dewhurst, E. Welz, I. Krummenacher, B. Engels,
H. Braunschweig, Science 2018, 359, 896; e) S. Dagorne, R.
Wehmschulte, ChemCatChem 2018, 10, 2509-2520; f) M.-A. Légaré, M.-
A. Courtemanche, É. Rochette, F.-G. Fontaine, Science 2015, 349, 513;
g) T. J. Hadlington, M. Driess, C. Jones, Chem. Soc. Rev. 2018, 47,
4176-4197; h) A. Merk, H. Großekappenberg, M. Schmidtmann, M.-P.
Luecke, C. Lorent, M. Driess, M. Oestreich, H. F. T. Klare, T. Müller,
Angew. Chem. 2018, 130, 15487-15492; i) P. P. Power, Acc. Chem. Res.
2011, 44, 627-637; j) P. P. Power, Nature 2010, 463, 171; k) S. Wang, T.
J. Sherbow, L. A. Berben, P. P. Power, J. Am. Chem. Soc. 2018, 140,
590-593; l) C. Weetman, S. Inoue, ChemCatChem 2018, 10, 4213-4228.
a) D. W. Stephan, Science 2016, 354; b) D. W. Stephan, G. Erker, Angew.
Chem. Int. Ed. 2010, 49, 46-76; c) D. W. Stephan, Acc. Chem. Res. 2015,
48, 306-316; d) D. W. Stephan, Dalton Trans. 2009, 3129-3136; e) D. W.
Stephan, G. Erker, Angew. Chem. Int. Ed. 2015, 54, 6400-6441; f) J.
Paradies, Coord. Chem. Rev. 2019, 380, 170-183.
X-Ray crystallographic studies
A suitable crystal was covered in mineral oil (Aldrich) and mounted on a
glass fiber or a mylar loop. The crystal was transferred directly to the cold
stream of a STOE IPDS 2 diffractometer. All structures were solved by
using the programs SHELXS/T[27] using Olex2.[28] The remaining non-
hydrogen atoms were located from successive difference Fourier map
calculations. The refinements were carried out by using full-matrix least-
squares techniques on F2 by using the program SHELXL.[29] In each case,
the locations of the largest peaks in the final difference Fourier map
calculations, as well as the magnitude of the residual electron densities,
were of no chemical significance. Details on the data refinement are
deposited in the Supporting Information.
[4]
Crystal Data 3. C25H56B2OP2, Mr = 456.25, monoclinic, P21/c (No. 14), a =
16.2691(8) Å, b = 10.2295(8) Å, c = 18.3578(10) Å, b = 92.996(4)°, a = g =
90°, V = 3051.0(3) Å3, T = 200 K, Z = 4, Z' = 1, µ(MoKa) = 0.156, 17638
reflections measured, 17638 unique (Rint = 0.0237) which were used in all
calculations. The final wR2 was 0.1390 (all data) and R1 was 0.0630 (I >
2(I)).
[5]
[6]
a) M. Melaimi, R. Jazzar, M. Soleilhavoup, G. Bertrand, Angew. Chem.
2017, 129, 10180-10203; b) G. D. Frey, V. Lavallo, B. Donnadieu, W. W.
Schoeller, G. Bertrand, Science 2007, 316, 439.
a) J. Escudié, C. Couret, H. Ranaivonjatovo, Coord. Chem. Rev. 1998,
178-180, 565-592; b) R. C. Fischer, P. P. Power, Chem. Rev. 2010, 110,
3877-3923; c) V. Y. Lee, A. Sekiguchi, Organometallics 2004, 23, 2822-
2834; d) H. Ottosson, P. G. Steel, Chem. Eur. J. 2006, 12, 1576-1585;
e) K. K. Milnes, L. C. Pavelka, K. M. Baines, Chem. Soc. Rev. 2016, 45,
1019-1035; f) J. W. Taylor, A. McSkimming, C. F. Guzman, W. H.
Harman, J. Am. Chem. Soc. 2017, 139, 11032-11035; g) A.-F.
Pécharman, A. L. Colebatch, M. S. Hill, C. L. McMullin, M. F. Mahon, C.
Weetman, Nat. Commun. 2017, 8, 15022; h) S. J. Geier, T. M. Gilbert, D.
Crystal Data 4. C47H92B3O8P3, Mr = 910.54, triclinic, P-1 (No. 2), a =
10.3051(3) Å, b = 15.3631(5) Å, c = 18.5740(7) Å, a = 82.113(3)°, b =
82.493(3)°, g = 79.034(3)°, V = 2843.0(2) Å3, T = 200(2) K, Z = 2, Z' = 1,
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W. Stephan, J. Am. Chem. Soc. 2008, 130, 12632-12633; i) Z. Dong, L.
Albers, M. Schmidtmann, T. Müller, Chem. Eur. J. 2019, 25, 1098-1105.
[16] J. Berkowitz, G. B. Ellison, D. Gutman, J. Phys. Chem. 1994, 98, 2744-
2765.
[7]
[8]
[9]
a) Y. Su, Y. Li, R. Ganguly, R. Kinjo, Angew. Chem. Int. Ed. 2018, 57,
7846-7849; b) B. Wang, Y. Li, R. Ganguly, H. Hirao, R. Kinjo, Nat.
Commun. 2016, 7, 11871.
[17] H. Nöth, B. Wrackmeyer, Chem. Ber. 1981, 114, 1150-1156.
[18] a) B. M. Mikhailov, Y. N. Bubnov, Zh. Obshch. Khim. 1961, 31, 577-582;
b) E. Rothgery, R. Köster, Liebigs Ann. 1974, 1974, 101-111.
[19] N. W. Mitzel, D. H. Brown, S. Parsons, P. T. Brain, C. R. Pulham, D. W.
H. Rankin, Angew. Chem. Int. Ed. 1998, 37, 1670-1672.
a) T. Tomioka, Y. Takahashi, T. Maejima, Organic & Biomolecular
Chemistry 2012, 10, 5113-5118; b) T. Tomioka, R. Sankranti, T. G.
Vaughan, T. Maejima, T. Yanase, J. Org. Chem. 2011, 76, 8053-8058.
a) H. J. Bestmann, T. Arenz, Angew. Chem. 1984, 96, 363-364; b) O. I.
Kolodiazhnyi, Tetrahedron 1996, 52, 1855-1929; for nice recent
developments in ylide chemistry, see e.g.: c) L. T. Scharf, D. M. Andrada,
G. Frenking, V. H. Gessner, Chem. Eur. J. 2017, 23, 4422-4434; d) T.
Scherpf, K.-S. Feichtner, V. H. Gessner, Angew. Chem. Int. Ed. 2017, 56,
3275-3279; e) C. Schwarz, T. Scherpf, I. Rodstein, J. Weismann, K.-S.
Feichtner, V. H. Gessner, ChemistryOpen 2019, 8, 621-626.
[20] a) M. Schlosser, T. Jenny, B. Schaub, Heteroat. Chem 1990, 1, 151-156;
b) S. M. Bachrach, J. Org. Chem. 1992, 57, 4367-4373.
[21] One referee of this paper suggested that the splitting in the NMR signals
of 3 could also be due to cis-trans isomerism/bond rotation of the C–C
bond of the P–C=C subunit. We thank the reviewer very much for this
helpful hint. Although such an isomerism is also possible, we believe that
the steric repulsion of the Me3P and iBu substituents would most likely
not lead to the 1:1 intensities of the signals. We also noted that T-
dependent NMR measurements at higher temperatures did not alter the
1:1 integration of the signals (see Figures S28 and S29 of the Supporting
Information).
[22] G. Margraf, H.-W. Lerner, M. Bolte, Acta Cryst. E 2002, 58, o546-o547.
[23] C. Chauvier, P. Thuéry, T. Cantat, Chem. Sci. 2016, 7, 5680-5685.
[24] R. Köster, D. Simić, M. A. Grassberger, Liebigs Ann. 1970, 739, 211-219.
[25] U. Höbel, H. Nöth, H. Prigge, Chem. Ber. 1986, 119, 325-337.
[26] J. Meiners, A. Friedrich, E. Herdtweck, S. Schneider, Organometallics
2009, 28, 6331-6338.
[10] a) M. Radius, F. Breher, Chem. Eur. J. 2018, 24, 15744-15749; for a
closely related paper of our group see: b) S. Styra, M. Radius, E. Moos,
A. Bihlmeier, F. Breher, Chem. Eur. J. 2016, 22, 9598-9512.
[11] H. J. Bestmann, Chem. Ber. 1962, 95, 58-63.
[12] a) H. Schmidbaur, Acc. Chem. Res. 1975, 8, 62-70; b) H. Schmidbaur,
U. Deschler, B. Milewski-Mahrla, B. Zimmer-Gasser, Chem. Ber. 1981,
114, 608-619; c) H.-J. Cristau, A. Perraud, E. Manginot, E. Torreilles,
Phosphorus, Sulfur Silicon Relat. Elem. 1993, 75, 7-10; d) H.-J. Cristau,
Chem. Rev. 1994, 94, 1299-1313; e) H.-J. Cristau, Y. Ribeill, F. Plenat,
L. Chiche, Phosphorus, Sulfur Silicon Relat. Elem. 1987, 30, 135-138.
[13] Y. Canac, C. Lepetit, M. Abdalilah, C. Duhayon, R. Chauvin, J. Am.
Chem. Soc. 2008, 130, 8406-8413.
[27] a) G. M. Sheldrick, Crystallographic Computing 3, 1985; b) G. Sheldrick,
Acta Cryst. A 2015, 71, 3-8.
[28] O. V. Dolomanov, L. J. Bourhis, R. J. Gildea, J. A. K. Howard, H.
Puschmann, J. Appl. Crystallogr. 2009, 42, 339-341.
[14] H. Bohrer, N. Trapp, D. Himmel, M. Schleep, I. Krossing, Dalton Trans.
2015, 44, 7489-7499.
[29] G. Sheldrick, Acta Cryst. C 2015, 71, 3-8.
[15] N. Inamoto, S. Masuda, Chem. Lett. 1982, 11, 1003-1006.
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Entry for the Table of Contents (Please choose one layout)
Layout 1:
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The sterically unencumbered α-
borylated phosphorus ylide
Electronic Frustration
M. Radius, E. Sattler, H. Berberich, F.
Breher*
Me3PC(H)B(iBu)2 (1) has been
synthesized, characterized, and
investigated with the aid of density
functional theory calculations. 1 has
been demonstrated to react with
various small molecules such as NH3,
CO, CO2 and the heterocumulenes
PhNCX. In part, different reaction
products are found as compared to
the previously reported derivative
Ph3PC(Me)BEt2.
Page No. – Page No.
Reactivity of a Sterically
Unencumbered α-Borylated
Phosphorus Ylide Towards Small
Molecules
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