Stabilization and Transfer of the Transient [MesP4]- Butterfly Anion Using BPh3

Article abstract of DOI:10.1002/anie.201508916

The transient bicyclo[1.1.0]tetraphosphabutane anion, generated from white phosphorus (P₄) and MesLi (Mes=2,4,6-tBu₃C₆H₂), can be trapped by BPh₃ in THF. This Lewis acid stabilized anion can be used as an [RP₄]^- transfer agent, reacting cleanly with neutral Lewis acids (B(C₆F₅)₃, BH₃, and W(CO)₅) to afford unique singly and doubly coordinated butterfly anions, and with the trityl cation to form a neutral, nonsymmetrical, all-carbon-substituted P₄derivative. This reaction path enables a simple, stepwise functionalization of white phosphorus. Trap and transfer: The bicyclo[1.1.0]tetraphosphabutane anion (see scheme, center), generated from P₄ and MesLi (Mes=2,4,6-tBu₃C₆H₂), can be trapped by BPh₃ in THF. The anion can be used as an [RP₄]^- transfer agent, reacting with neutral Lewis acids (B(C₆F₅)₃, BH₃, and W(CO)₅) to afford unique singly and doubly coordinated butterfly anions and with the trityl cation to form a neutral, nonsymmetrical P₄ derivative.

Full text of DOI:10.1002/anie.201508916

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Communications
Chemie
International Edition: DOI: 10.1002/anie.201508916
German Edition: DOI: 10.1002/ange.201508916
P4 Functionalization
À
Stabilization and Transfer of the Transient [Mes*P ] Butterfly Anion
4
Using BPh3
Jaap E. Borger, Andreas W. Ehlers, Martin Lutz, J. Chris Slootweg, and Koop Lammertsma*
Abstract: The transient bicyclo[1.1.0]tetraphosphabutane
anion, generated from white phosphorus (P ) and Mes*Li
4
(
Mes* = 2,4,6-tBu C H ), can be trapped by BPh in THF. This
3 6 2 3
À
Lewis acid stabilized anion can be used as an [RP ] transfer
4
agent, reacting cleanly with neutral Lewis acids (B(C F ) ,
6
5 3
BH , and W(CO) ) to afford unique singly and doubly
3
5
coordinated butterfly anions, and with the trityl cation to
form neutral, nonsymmetrical, all-carbon-substituted
a
P derivative. This reaction path enables a simple, stepwise
4
functionalization of white phosphorus.
Scheme 1. Previous approaches toward the stepwise functionalization
of P4.
F
unctionalizing white phosphorus directly is imperative if
chlorinated intermediates are to be avoided in producing
[
1]
organophosphorus compounds. However, the high and
reacts in toluene with ArLi (Ar= Dmp (2,6-dimesitylphenyl)
or Mes* (2,4,6-tBu C H )) and B(C F ) to give the stabilized
unpredictable reactivity of the P4 tetrahedron makes it
a challenge to develop such processes. Lately, encouraging
progress has been made by several groups aimed at the
3
6
2
6
5 3
[2]
À
[ArP ] anion (D) of which the nucleophilic LA-coordinated
4
phosphorus atom can be endo-alkylated with MeI, thereby
controlled, stepwise functionalization of P . For example,
illustrating that P4 can be substituted with two different
C groups in two controlled steps. However, there are also
4
[3]
[14]
Scheer and co-workers generated symmetrically disubsti-
R
tuted bicyclo[1.1.0]tetraphosphabutanes (A) with Cp
limitations. Not only does the strongly stabilizing B(C F )
5 3
6
[
4]
R
[5,6]
organic radicals (Scheme 1; Cp = C R ), Wolf et al.
reduce the reactivity of D to a degree that an analogy with
5
5
used an organometallic nickel(I) radical to obtain a similar
neutral phosphanes (R P) may be more appropriate, also the
3
P butterfly,
Bertrand
et al.
demonstrated
diverse
apolar solvent hampers their synthesis. The further develop-
ment of this novel chemistry demands that the role of the
Lewis acid is addressed. In the present study, we begin by
4
[7]
P activations with various carbenes,
Weigand et al.
4
+
reported stepwise R P cation insertions into the P cage
2
4
[
8]
+
(
B) with subsequent NHC-induced fragmentation into P
describing the use of the far milder BPh as trapping agent,
3
3
[
9]
À
and P species, and Hill and co-workers used a nucleophilic
which provides a convenient source of the stabilized [RP4]
2
2
À
[10]
approach to obtain the [nBu P ]
coordinating Mg complexes to stabilize the otherwise
unstable phosphides. The group of Schulz addressed the
role of Lewis acids (LA) in, for example, the interconversion
of exo–exo and endo–exo disubstituted P isomers, which
can also serve as chelating ligands for Cu , as reported
recently by Scheer.
a frustrated Lewis pair (FLP) approach, we showed that P4
dianion (C)
with
ion in THF. We show that this weaker adduct enables the
smooth transfer of the tetraphosphide anion to other Lewis
acids and C electrophiles, which significantly facilitates the
2
4
2
+
[11]
selective, stepwise functionalization of the P scaffold.
4
[
12]
Addition of Mes*Li to a THF solution of P and BPh at
4
4
3
+
08C gave only bicyclo[1.1.0]tetraphosphabutanide 1 (76%
yield of the isolated product after washing with benzene/n-
[13]
In an exploratory study, mimicking
31
1
pentane; Scheme 2), according to the P{ H} NMR spectrum
that shows only three signals in a 1:1:2 ratio (AMX spin
2
system) at d = À112.5(P4), À149.0(P1), and À306.5 ppm
[
*] J. E. Borger, Dr. A. W. Ehlers, Dr. J. C. Slootweg,
Prof. Dr. K. Lammertsma
[15]
(
P2,3). The synthesis is suited for multigram scale and is,
Department of Chemistry and Pharmaceutical Sciences
VU University Amsterdam
De Boelelaan 1083, 1081 HV Amsterdam (The Netherlands)
E-mail: K.Lammertsma@vu.nl
because of the solubility of Mes*Li in THF, complete within
1 hour, as opposed to the 4 weeks needed for D. Notably, in
contrast to B(C F ) , BPh does not form an adduct with
ethers, which allows the use of THF as solvent for the
synthesis of 1.
6
5
3
3
Dr. M. Lutz
Crystal and Structural Chemistry
Bijvoet Center for Biomolecular Research, Utrecht University
Padualaan 8, 3584 CH Utrecht (The Netherlands)
Crystals of 1, suitable for X-ray diffraction, were grown by
layering a THF solution with n-hexane. The molecular
structure of 1 (Figure 1a) reveals the BPh adduct of the
3
Prof. Dr. K. Lammertsma
Department of Chemistry, University of Johannesburg
Auckland Park, Johannesburg, 2006 (South Africa)
+
Mes*P anion with the Li cation coordinated by four THF
4
molecules (not shown) and shows an exo,exo configuration.
The bridgehead P2ÀP3 bond (2.1562(12) Š), the slightly
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/anie.201508916.
longer bonds connecting the flanking P1 and P4 atoms
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À
4
Scheme 2. Synthesis of the BPh -stabilized [Mes*P ] butterfly anion.
3
Scheme 3. The exchange of BPh in 1 with B(C F ) to give 2.
3
6 5 3
a) B(C F ) (1.1 equiv), toluene, RT.
6
5 3
1
to obtain exo,exo-2 and not the exo,endo isomer may suggest
a dissociative process by first breaking the PÀB bond (DE =
À1
3
7.7 kcalmol ), but an associative path is more likely in light
of the mild and apolar reaction conditions (toluene, RT). This
pathway would entail the intermediate formation of the
À
mixed bisborane [Mes*P ·(endo-B(C F ) )(exo-BPh )] and
4
6
5
3
3
subsequently formation of exo,endo-2 by dissociation of
[18]
BPh3. Compound exo,endo-2 should then convert into the
exo,exo isomer, for example, via a bis(B(C F ) ) adduct, as has
6
5 3
been reported for the related phosphide [Li(12-crown-4)]-
[
19]
[
H P·(B(C F ) ) ].
DFT calculations at the wB97X-D/6–
2
6
5 3 2
3
11 + G(d,p)/PCM(toluene)//6-31G(d) level of theory sup-
port this course of events (Scheme 4), revealing the 13.4 kcal
[17]
Figure 1. a) Molecular structure of 1a in the crystal (thermal ellip-
+
soids are set at 30% probability; H atoms, the [Li(THF)4] counterion,
and noncoordinated THF are omitted for clarity). Only one conforma-
tion of the disordered tert-butyl group is shown. Selected bond lengths
[
2
2
Š] and torsion angle [8]: P1ÀP2/P3 2.2234(12)/2.2245(12), P4ÀP2/P3
.2117(12)/2.2048(12), P2ÀP3 2.1562(12), C1ÀP1 1.881(3), P4ÀB1
.064(3); P1-P2-P3-P4 95.87(5). b) HOMO of the optimized geometry
of anion 1.
Scheme 4. Relative computed wB97X-D/6-311+G(d,p)/PCM-
À1
(toluene)//6-31G(d) energies (in kcalmol ) for the conversion of
exo,exo-1 into exo,exo-2.
(
2
P1ÀP2/P3 2.2234(12)/2.2245(12) Š, P4ÀP2/P3 2.2117(12)/
o
À1
.2048(12) Š), and the P1-P2-P3-P4 torsion angle (95.87(5) )
mol favored formation of exo,endo-2. The formation of the
[
14]
are similar to those found for D
and related neutral
exo,exo isomer from exo,endo-2, via the congested symmet-
[
3,4–6,12]
À1
À
P compounds.
4
Importantly, the 37.7 kcalmol strong
rical bisborane adduct [Mes*P ·(B(C F ) ) ] (DE = 1.3 kcal
4
6
5
3
2
À
À1
À1
PÀB bond of 1 , computed at the wB97X-D/6-311 + G(d,p)//
mol ), is favored by a further 2.0 kcalmol .
[16]
À1
6
-31 + G(d,p) level of theory, is 24.4 kcalmol weaker than
The B(C F ) -induced exchange between exo,endo-2 and
exo,exo-2 is supported by analysis of the P and B NMR
spectra. A stoichiometric mixture of B(C F ) and exo,exo-2
6
5 3
À
À1
31
11
that computed for D (DE = 62.1 kcalmol ), whereas the
[20]
bond lengths are similar (PÀBPh 2.0785 Š, observed
3
6 5 3
[14]
2
.064(3) Š; PÀB(C F ) 2.0877 Š, observed
2.064(2) Š).
in [D ]toluene showed at room temperature broadened
8
6
5
3
31
1
11
1
The highest occupied molecular orbital (HOMO) of 1 shows
the expected strong nucleophilic character with a large
coefficient on the readily accessible wingtip P4 atom
P{ H} resonance signals and a single B{ H} signal at d =
À14.5 ppm, but the bridgehead P2 and P3 atoms gave two
nonequivalent, baseline-separated signals at À608C (d =
À316.7 and À323.8 ppm, ratio 1.5:1; coalescence at À108C;
(
Figure 1b).
À
°
À1 [21]
Functionalizing the P core of BPh -stabilized [RP ]
estimated DG
= 11.2 kcalmol ) at which temperature
263K
4
3
4
effectively calls for convenient replacement of its LA. To
obtain the necessary insight, we first examined borane
exchange and reacted 1.1 equiv of B(C F ) with a suspension
also the resonance signals for the wingtip atoms (d =
À124.1(P1) and À152.9 ppm (P4)) and the borane broadened.
A
control experiment showed that rapid cooling of
6
5 3
of 1 in toluene at room temperature to selectively obtain the
a [D ]toluene solution of only exo,exo-2 to À608C (no
8
[14]
known exo,exo-2 (D; Ar= Mes*)
which was isolated in
B(C F ) present) did not show broadening or splitting of
6
5 3
31
1
11
1
8
2% yield (Scheme 3; d = À132.2(P1), À159.9(P4), and
the P{ H} and B{ H} NMR resonance signals. We interpret
À
[22]
À310.4 ppm (P2,P3)). Transferring [Mes*P ] from exo,exo-
these results as supportive of an associative mechanism for
4
6
14
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[23]
the rapidly exchanging isomers of 2. In contrast, at ambient
temperature exo,exo-1 does not undergo exchange with BPh
3
31
1
as it shows a sharp AMX spin system in the P{ H} NMR
2
11
spectrum and an additional B signal for the free borane at
d = 49.4 ppm. DFT calculations concur with the apparent lack
of dynamics, as the bis(BPh ) intermediate (compare with
3
À1
Scheme 4) is a significant 15.3 kcalmol less stable than
exo,exo-1, which inhibits rapid exchange at room temper-
ature.
We next set out to investigate whether or not a bisborane–
À
[
RP ] is experimentally accessible. We felt that two boranes
4
[17]
Figure 2. Molecular structure of 3b in the crystal (thermal ellip-
should be able to effectively stabilize both lone pairs of the
wingtip phosphorus, but that the size of their substituents (Ph,
C F ) might be sterically too demanding to allow isolation of
the bisborane adduct. The smallest of the boranes, BH , was
targeted successfully for stabilizing [Mes*P ] . Adding an
+
soids are set at 50% probability; H atoms, the [PPh4] counterion,
and a cocrystallized THF molecule are omitted for clarity). Selected
bond lengths [Š], angle, and torsion angle [8]: P1ÀP2/P3 2.2249(6)/
2.2287(6), P4ÀP2/P3 2.1884(6)/2.1868(6), P2ÀP3 2.1985(6), C1ÀP1
6
5
3
À
À
À
1
.8787(16), P4 B1 1.961(2), P4 B2 1.957(2); B1-P4-B2 122.84(10);
4
P1-P2-P3-P4 105.41(3).
excess of Me S·BH to a suspension of 1 in n-pentane enabled
2
3
isolation of the desired bisborane 3a, which was isolated in
11
6
8% yield (Scheme 5a). Its B NMR spectrum showed two
differ slightly from each other (P4ÀB1 39.8, P4ÀB2 36.4 kcal
À1
mol ) with the exo-BH group having the strongest bond. We
3
note 3 to be the first isolable P butterfly with two small
4
coordinating groups on a flanking phosphorus atom that
maintains its anionic character, thereby favorably contrasting
bicyclic tetraphosphanes with large, sterically encumbered
[
3–6,12,14,25]
groups that hamper controlled functionalization.
À
Next, we targeted the transfer of [Mes*P ] to the metal-
4
based Lewis acid W(CO) , which is isolobal with BH ,
5
3
Scheme 5. Transfer reactions of the BPh -stabilized Mes*P butterfly-
expecting a similar trisubstituted anion as 3. Stirring 1 and
3
4
type anion 1. a) Me S·BH (2.5 equiv), n-pentane, RT; b) 3a, Ph PBr
2
3
4
[(MeCN)W(CO) ] in THF in a 1:2.1 ratio showed indeed the
5
(
1.1 equiv), THF, RT; c) [(MeCN)W(CO) ] (2.1 equiv), THF, RT; d) 4a,
5
selective formation of the anticipated new ditungstate 4a,
Ph PBr (1.1 equiv), THF, RT.
4
which was isolated in 81% yield as a thick brown oil
[27]
31
(Scheme 5c).
The P NMR spectrum of compound 4a
shows characteristic resonance signals at d = À56.4(P1),
broad quartets at d = À30.9 and À37.9 ppm and the expected
À171.3(P4), and À259.0 ppm (P2,P3; AMX spin system).
2
31
1
AMX spin system in the P{ H} NMR spectrum with
Salt metathesis using Ph PBr afforded phosphonium salt 4b
2
4
resonance signals at d = À60(P4), À109.0(P1), and
À275.3 ppm (P2,P3). The resonance signal for the P4 nucleus
is significantly deshielded compared to that of exo,exo-1 and
compares well to that of the structurally related neutral
(65% yield; Scheme 5d) of which crystals suitable for X-ray
structure determination were obtained.
The molecular structure of 4b (Figure 3) confirms the
presence of two W(CO) groups coordinating to P4 at similar
5
[14]
DmpP Me·B(C F )
(À57.5 ppm)
and
Ga P tBu
distances (P4ÀW1 2.5811(4), P4ÀW2 2.5912(4) Š) with a W1-
4
6
24]
5
3
2
4
6
+
[
(
À50.7 ppm). Salt metathesis enabled exchange of the Li
P4-W2 angle of 125.069(16)8. These structural parameters are
+
cation for Ph P to give 3b which was isolated in 25% yield
akin to those reported for the related diphosphide [Ph P]-
4
4
[
28]
(
Scheme 5b). Crystals of 3b suitable for X-ray diffraction
[((CO) W) PH ]. In the IR spectrum, the CO stretching
5
2
2
À1
were grown and the obtained molecular structure confirmed
modes
(4b:
2060,
2048,
1921
and
1861 cm ;
À
À
À1
its identity as
a
bis(BH )-stabilized [Mes*P4] anion
[((CO) W) PH ] : 2048, 1930, 1872 cm ) also suggest that
5 2 2
the donor strength of the anionic [RP ] core is similar to that
of PH2 . The P fold angle of 4b (101.83(2)8) is, like that for
3
À
(
Figure 2). The P1-P2-P3-P4 torsion angle of 105.41(3)8 is
4
À
nearly 108 larger than for 1, which suggests repulsion between
the endo-BH3 group (B2) and the lone pair on P1. This
widening of the butterfly is also observed in the related
4
3b (105.41(3)8), larger than for bifunctionalized P spe-
4
[3–6,14]
cies.
However, the P1ÀP2/P3 (2.2170(6)/2.2296(6) Š)
[
14]
trisubstituted DmpP Me·B(C F ) (102.98(2)8) and cationic
and P4ÀP2/P3 (2.2113(6)/2.2175(6) Š) bond lengths are
4
6
5 3
+
[
Mes* P Cl] (À101.68(3)8) on which the group of Schulz
similar to those of bifunctionalized P species and no ring
2
4
4
[
25]
reported recently,
but is less pronounced than in the
contraction like in 3b is found.
1
:3 1:1
2+
tetrasubstituted [{CpRu(PPh ) } (m ,h -P H )]
cation
The exo PÀW(CO) bond of 4 is slightly stronger
3
2
2
4
2
5
[
26]
À1
(
134.28) isolated by Stoppioni et al. The P4ÀP2 and P4À (1.5 kcalmol ) than its endo bond, just like for the borane
À1
P3 bonds (2.1884(6), 2.1868(6) Š) are slightly contracted
groups of 3, but both are about 25 kcalmol stronger (DE:
À1
compared to the P1ÀP2 and P1ÀP3 bonds (2.2249(6),
P4ÀW1 63.7; DE: P4ÀW2 62.2 kcalmol ) than the PÀB
2
.2287(6) Š), likely as a result of the Lewis acidity of the
bonds, suggesting a more prominent charge transfer from the
À
BH groups. The calculated PÀB bond strengths of anionic 3
[RP4] core to the metal complexes. This effect is also
3
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+
À
+
À
6
[
17]
Scheme 6. Top: Reaction of 1 with Ph
C
3
PF
6
; a) Ph
3
C PF
Figure 3. Molecular structure of 4b in the crystal (thermal ellipsoids
+
(1.1 equiv), pyridine (5 equiv), DME, RT. Bottom: Molecular structure
of 5 in the crystal (thermal ellipsoids are set at 50% probability;
H atoms are omitted for clarity). Selected bond lengths [Š], angle, and
are set at 50% probability; H atoms and the [PPh4] counterion are
omitted for clarity). Selected bond lengths [Š], angle, and torsion angle
8]: P1ÀP2/P3 2.2170(6)/2.2296(6), P4ÀP2/P3 2.2113(6)/2.2175(6),
P2ÀP3 2.1780(6), C1ÀP1 1.8707(16), P4ÀW1 2.5811(4), P4ÀW2
.5912(4); W1-P4-W2 125.069(16); P1-P2-P3-P4 101.83(2).
[17]
[
torsion angle [8]: P1ÀP2/P3 2.2257(6)/2.2294(6), P4ÀP2/P3 2.2001(6)/
2
.2243(6), P2ÀP3 2.1737(6), C1ÀP1 1.8700(16), P4ÀC19 1.9446(15);
2
P1-P2-P3-P4 93.93(2).
reflected in the different energies of the MOs of the lone pair
on P1, that is, À0.18 eV (HOMO) for 3, À0.21 eV (HOMO-6)
P core. This novel transfer approach enables facile additional
functionalization of bicyclo[1.1.0]tetraphosphabutane anions.
We are now exploring the reactivity pattern of these intrigu-
4
31
for 4. Equally indicative is the P NMR resonance signal for
the P1 center of 4a at d = À56.4 ppm, which is significantly
deshielded (Dd = 52.6 ppm) from that of 3a as a result of the
ing new P -derived species and their utility in subsequent
4
À
difference in overlap of the HOMO of [Mes*P4] with the
controlled transformations.
LUMO of the two Lewis acids; W(CO) gives a better overlap
5
than BH , resulting in a smaller energy gap of 0.01 versus
3
0
.08 eV, respectively.
Extending the [RP ] transfer strategy, we aimed for PÀC
Acknowledgements
À
4
bond formation using the carbon-based Lewis acid
Ph C PF . Stirring 1 with 1.1 equiv of the tritylium salt in
dimethoxyethane (DME) resulted indeed directly in full
This work was supported by the Council for Chemical
Sciences of the Netherlands Organization for Scientific
Research (NWO/CW).
+
À
6
3
conversion to the desired borane-free 5, which on separation
from BPh by addition of pyridine to form the insoluble
Keywords: anions · boranes · Lewis acids ·
3
Py·BPh adduct could be isolated in 33% yield (Scheme 6). In
organophosphorus compounds · phosphorus
3
3
1
the P NMR spectrum of 5, resonance signals at d =
À105.5(P4), À127.5(P1), and À308.8 ppm (P2,P3) confirm
How to cite: Angew. Chem. Int. Ed. 2016, 55, 613–617
Angew. Chem. 2016, 128, 623–627
that the bicyclic P framework remained intact. The molec-
4
ular structure of 5 (Scheme 6; bottom), obtained by an X-ray
crystal structure determination, shows an exo,exo-disubsti-
[
1] D. E. C. Corbridge, Phosphorus 2000, Elsevier, Amsterdam,
000.
2] For reviews, see: a) M. Scheer, G. Balµzs, A. Seitz, Chem. Rev.
010, 110, 4236 – 4256; b) N. A. Giffin, J. D. Masuda, Coord.
tuted P butterfly with comparable peripheral PÀP bonds and
4
2
a fold angle of 93.93(2)8, similar to those of other bifunction-
[
[
3–6,12,14]
alized species.
Interestingly, in contrast to the previ-
2
À
ously reported endo methylation of [DmpP ·B(C F ) ] with
MeI, addition of the tritylium salt only yields the exo,exo
Chem. Rev. 2011, 255, 1342 – 1359; c) B. M. Cossairt, N. A. Piro,
C. C. Cummins, Chem. Rev. 2010, 110, 4164 – 4177; d) M.
Caporali, L. Gonsalvi, A. Rossin, M. Peruzzini, Chem. Rev.
2010, 110, 4178 – 4235; e) M. Peruzzini, L. Gonsalvi, A. Romer-
osa, Chem. Soc. Rev. 2005, 34, 1038 – 1047.
4
6
5 3
[
14]
product devoid of the Lewis acid. Presumably, BPh departs
3
À
on endo PÀC bond formation between the [RP ] ion and the
4
+
Ph C ion with concurrent isomerization. The resulting
3
[
3] S. Heinl, S. Reisinger, C. Schwarzmaier, M. Bodensteiner, M.
Scheer, Angew. Chem. Int. Ed. 2014, 53, 7639 – 7642; Angew.
Chem. 2014, 126, 7769 – 7773.
exo,exo-bicyclo[1.1.0]tetraphosphane 5 is the first stable,
nonsymmetrical all-hydrocarbon-substituted butterfly deriv-
ative generated directly from P in two simple steps.
[4] The use of bulky main-group radicals has been explored in
a number of cases, giving similar butterfly-type products. See:
a) J.-P. Bezombes, P. B. Hitchcock, M. F. Lappert, J. E. Nycz,
Dalton Trans. 2004, 499 – 501; b) B. M. Cossairt, C. C. Cummins,
New J. Chem. 2010, 34, 1533 – 1536; c) N. A. Giffin, A. D.
Hendsbee, T. L. Roemmele, M. D. Lumsden, C. C. Pye, J. D.
Masuda, Inorg. Chem. 2012, 51, 11837 – 11850; d) S. Khan, R.
Michel, J. M. Dieterich, R. A. Mata, H. W. Roesky, J.-P. Demers,
A. Lange, D. Stalke, J. Am. Chem. Soc. 2011, 133, 17889 – 17894.
4
À
In summary, transient [Mes*P4] can be conveniently
À
trapped with the mild Lewis acid BPh . The [Mes*P ] core of
3
4
the stabilized anion can be transferred to both the bulky
B(C F ) and small BH Lewis acid as well as to W(CO) to
6
5
3
3
5
À
afford unique singly and doubly coordinated [RP4] tetra-
phosphides. Transfer to the tritylium cation leads to formation
of a new PÀC bond, thereby further functionalizing the
6
16
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ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2016, 55, 613 –617

Angewandte
Communications
Chemie
[
[
5] S. Pelties, D. Herrmann, B. de Bruin, F. Hartl, R. Wolf, Chem.
[17] CCDC 1425046 (1a), 1425047 (3b), 1425048 (4b), and 1425049
Commun. 2014, 50, 7014 – 7016.
(5) contain the supplementary crystallographic data for this
paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre.
6] For selected other examples of transition-metal-based radical-
type activation of P4 giving butterfly species, see: a) O. J.
Scherer, T. Hilt, G. Wolmershäuser, Organometallics 1998, 17,
[18] The mixed borane complex [Mes*P ·(endo-B(C F ) )(exo-
4
6 5 3
À
31
4
3
110 – 4112; b) S. Heinl, M. Scheer, Chem. Sci. 2014, 5, 3221 –
225; c) C. Schwarzmaier, A. Y. Timoshkin, G. Balµzs, M.
BPh )] could not be detected by P NMR spectroscopy.
3
[19] A.-M. Fuller, A. J. Mountford, M. L. Scott, S. J. Coles, P. N.
Horton, D. L. Hughes, M. B. Hursthouse, S. J. Lancaster, Inorg.
Chem. 2009, 48, 11474 – 11482.
Scheer, Angew. Chem. Int. Ed. 2014, 53, 9077 – 9081; Angew.
Chem. 2014, 126, 9223 – 9227.
[
[
[
7] a) J. D. Masuda, W. W. Schoeller, B. Donnadieu, G. Bertrand,
Angew. Chem. Int. Ed. 2007, 46, 7052 – 7055; Angew. Chem.
[20] While the exo,exo isomer is the most documented form of
bicyclo[1.1.0]tetraphosphabutanes
(see
Refs. [3–6,14,25]),
2
007, 119, 7182 – 7185; b) O. Back, G. Kuchenbeiser, B. Donna-
examples of the exo,endo product, or evidence thereof, have
been reported: a) E. Niecke, R. Rüger, B. Krebs, Angew. Chem.
Int. Ed. Engl. 1982, 21, 544 – 545; Angew. Chem. 1982, 94, 553 –
554; b) A. R. Fox, R. J. Wright, E. Rivard, P. P. Power, Angew.
Chem. Int. Ed. 2005, 44, 7729 – 7733; Angew. Chem. 2005, 117,
7907 – 7911; c) Ref. [9]; d) Ref. [12].
dieu, G. Bertrand, Angew. Chem. Int. Ed. 2009, 48, 5530 – 5533;
Angew. Chem. 2009, 121, 5638 – 5641.
8] a) M. H. Holthausen, J. J. Weigand, Chem. Soc. Rev. 2014, 43,
6
639 – 6657; b) J. J. Weigand, M. Holthausen, R. Frçhlich,
Angew. Chem. Int. Ed. 2009, 48, 295 – 298; Angew. Chem. 2009,
21, 301 – 304; c) M. H. Holthausen, J. J. Weigand, J. Am. Chem.
1
[21] See the Supporting Information for further details.
3
1
1
Soc. 2009, 131, 14210 – 14211.
[22] The endo isomer could not be detected by P{ H} NMR
spectroscopy when 1 was reacted with a “deficit” (0.8 equiv) of
B(C F ) in [D ]toluene.
9] M. H. Holthausen, S. K. Surmiak, P. Jerabek, G. Frenking, J. J.
Weigand, Angew. Chem. Int. Ed. 2013, 52, 11078 – 11082; Angew.
Chem. 2013, 125, 11284 – 11288.
6
5
3
8
[23] The chemical shift differences for the two products detected at
[
[
10] M. Arrowsmith, M. S. Hill, A. L. Johnson, G. Kociok-Kçhn,
M. F. Mahon, Angew. Chem. Int. Ed. 2015, 54, 7882 – 7885;
Angew. Chem. 2015, 127, 7993 – 7996.
À608C are in the same range as detected for the rac and
meso isomers of the symmetrically substituted 1,4-P [P(N-
4
[4a]
(SiMe ) (NiPr )] , reported by Lappert et al. , which show
3
2
2
2
11] Reacting organo-alkali reagents with P gives complex product
three resonance signals for the bridgehead P atoms (d = À325.8
(rac), À332.9 (meso), and À338.0 ppm (rac)) and also only one
for the wingtip P atoms (À139.5 ppm).
4
mixtures: a) M. M. Rauhut, A. M. Semsel, J. Org. Chem. 1963,
2
1
8, 471 – 472; b) M. M. Rauhut, A. M. Semsel, J. Org. Chem.
963, 28, 473 – 477.
[24] M. B. Power, A. R. Barron, Angew. Chem. Int. Ed. Engl. 1991,
30, 1353 – 1354; Angew. Chem. 1991, 103, 1403 – 1404.
[25] J. Bresien, K. Faust, A. Schulz, A. Villinger, Angew. Chem. Int.
Ed. 2015, 54, 6926 – 6930; Angew. Chem. 2015, 127, 7030 – 7034.
[26] P. Barbaro, C. Bazzicalupi, M. Peruzzini, S. Seniori Constantini,
P. Stoppioni, Angew. Chem. Int. Ed. 2012, 51, 8628 – 8631;
Angew. Chem. 2012, 124, 8756 – 8759.
[
[
12] J. Bresien, K. Faust, C. Hering-Junghaus, J. Rothe, A. Schulz, A.
Villinger, Dalton Trans. 2015, DOI: 10.1039/C5DT02757H.
13] C. Schwarzmaier, S. Heinl, G. Balµzs, M. Scheer, Angew. Chem.
Int. Ed. 2015, 54, 13116 – 13121; Angew. Chem. 2015, 127, 13309 –
1
3314.
[
[
14] J. E. Borger, A. W. Ehlers, M. Lutz, J. C. Slootweg, K. Lam-
mertsma, Angew. Chem. Int. Ed. 2014, 53, 12836 – 12839; Angew.
Chem. 2014, 126, 13050 – 13053.
[27] No monosubstituted product could be detected when only one
equivalent of the tungsten precursor was used.
[28] U. Vogel, K.-C. Schwan, M. Scheer, Eur. J. Inorg. Chem. 2004,
2062 – 2065.
1
15] Based on the H NMR spectrum recorded immediately after
mixing Mes*Li and BPh in [D ]THF at RT, these reagents do
3
8
not show any direct quenching. However, upon standing over-
night a reaction does occur showing full conversion to unidenti-
fied products.
[
16] J.-D. Chai, M. Head-Gordon, Phys. Chem. Chem. Phys. 2008, 10,
6
615 – 6620. DFT calculations were performed at wB97X-D
Received: September 23, 2015
Revised: October 27, 2015
Published online: November 27, 2015
using Gaussian09 (Revision D.01); see the Supporting Informa-
tion for further details.
Angew. Chem. Int. Ed. 2016, 55, 613 –617
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
617