A new and convenient approach towards bis(iminophosphoranyl)methane ligands and their dicationic, cationic, anionic and dianionic derivatives

Article abstract of DOI:10.1039/b610049j

The availability of bis(aminophosphoranes) 2a-c through a straightforward synthesis yielded access to a whole family of N,N ligands via sequential deprotonation. The obtained cationic 3a-c, neutral 4a-c, anionic 5a-c and dianionic 6a-c compounds were full

Full text of DOI:10.1039/b610049j

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PAPER
www.rsc.org/njc | New Journal of Chemistry
A new and convenient approach towards bis(iminophosphoranyl)methane
ligands and their dicationic, cationic, anionic and dianionic derivativeswz
Matthieu Demange, Leila Boubekeur, Audrey Auffrant, Nicolas Mezailles,
´
Louis Ricard, Xavier Le Goff and Pascal Le Floch*
Received (in Montpellier, France) 13th July 2006, Accepted 30th August 2006
First published as an Advance Article on the web 22nd September 2006
DOI: 10.1039/b610049j
The availability of bis(aminophosphoranes) 2a–c through a straightforward synthesis yielded
access to a whole family of N,N ligands via sequential deprotonation. The obtained cationic 3a–c,
neutral 4a–c, anionic 5a–c and dianionic 6a–c compounds were fully characterized by NMR and
X-ray crystallography. Monocations 3a–c were shown to result from the deprotonation of 2a–c at
the bridging methylene carbon. DFT calculations evidenced a substantial negative charge at this
carbon. For the neutral bis(iminophosphoranes) 4a–c, two different forms were experimentally
observed depending on the nature of the substituent at nitrogen. In the presence of an aryl group,
a bis(iminophosphorane) is obtained whereas with alkyl substituent a tautomeric form resulting
from a (1,3) hydrogen shift is observed. Theoretical studies were in good agreement with
experimental results showing that these two forms are close in energy. The structure obtained for
monoanion 5a reveals that a substantial interaction occurs between the anionic carbon and the
lithium cation. The X-ray crystal structure of the optically pure dianion 6b has also been
recorded.
chemistry of such a dianionic derivative (N-TMS) with lantha-
1
Introduction
8–22
nides and transition metals.
Several groups have focused
There is a continuing interest in devising new bidentate nitro-
gen ligands that exhibit tailored electronic properties. Past
years have witnessed the developments of new classes of
on the coordination chemistry of monoanionic derivatives of
23–32
bis(iminophosphorane).
In particular, Cadierno et al.
performed the deprotonation of the anion in the coordination
sphere of the ruthenium to yield a carbene complex whose
33,34
2
neutral and monoanionic ligands featuring sp hybridized
nitrogen atoms. Though most efforts focused on the chemistry
chemistry was subsequently studied.
of CQN based ligands, recent studies showed that ylidic
The monoanionic ligand was also recently employed in the
elaboration of efficient lanthanide catalysts by Roesky and co-
3
structures such as iminophosphoranes (R PQNR) behave as
efficient ligands for the elaboration of various transition metal
1
workers. Thus, the yttrium, samarium complex of the
ꢀ
–10
complexes.
These ligands deserve attention because they
[
CH(PPh NSiMe ) ] anionic ligand was found to be a very
3 2
2
exhibit both different steric and electronic properties com-
pared to imines. Indeed the absence of a real p-system and the
presence of a formal positive charge at the phosphorus atom
efficient catalyst for the hydroamination/cyclization, hydro-
silylation and the sequential hydroamination/hydrosilylation
35–40
processes.
In these studies however, the effect of nitrogen
2
make the nitrogen atom a harder donor than classical sp -
substitution on the coordination behavior of the ligands as
well as on the catalytic activities of the complexes was not
envisaged since they were performed with either one of N-silyl,
N-aryl or N-phosphonate derivatives. This situation mainly
results from the poor availability of N-functional derivatives
of iminophosphoranes and bis(iminophosphoranes) in general.
hybridized nitrogen atoms such as imines or related hetero-
cyclic derivatives. Bis(iminophosphorane)methane ligands are
most interesting species because of their potential chelating
1
1–14
behavior.
Furthermore, the presence of two acidic protons
at the methylene bridge offers the possibility to generate
anionic derivatives which are structurally related to acetylace-
tonates and b-diketiminates, and even geminal dianions via
Indeed most of the syntheses rely on the Staudinger reaction
41–44
involving an azide and a tertiary phosphine.
However, this
1
5–17
double deprotonation.
This was nicely illustrated by
straightforward approach suffers from severe limitations since
functional azides are in most cases not readily available. Last
year, as part of a related program, we were interested in
elaborating a new class of P B N ligands featuring one
Cavell and coworkers who have studied the coordination
Laboratoire He´te´roe´le´ments et Coordination UMR CNRS 7653,
De´partement de Chimie, Ecole Polytechnique, Route de Saclay,
F-91128 Palaiseau. E-mail: lefloch@poly.polytechnique.fr
w Electronic supplementary information (ESI) available: Theoretical
A B A B
structures of IIa, IIIa, IVa , IVa , IVc , IVc ; X-ray structures of 2b,
3a, 4c, 5c, 6b. See DOI: 10.1039/b610049j
7
phosphino group and one iminophosphorane ligand. For this
purpose, we devised a very simple synthetic approach based on
5
the Kirsanov reaction (Scheme 1).
4
We found that formation of N-functionalized phosphine-
iminophosphorane bidentate ligands could be easily achieved
through the deprotonation of the corresponding hydrobromide
zco Tl oh ue r Hi mT aMg eL s .v ersion of this article has been enhanced with additional
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Scheme 1 Synthesis of phosphino-iminophosphoranes.
aminophosphonium salts. The most attractive feature of this
approach is the availability of these salts which can be
prepared in a one pot reaction through the reaction of primary
amines with bis(diphenylphosphonium)methane dibromide.
In this article we wish to report on the extension of this
method to the synthesis of several functional derivatives of
bis(iminophosphorane)methane derivatives and their respec-
tive mono- and dicationic, anionic and dianionic derivatives.
Fig. 1 Molecular structure of compound 2b, showing the atomic
Results and discussion
numbering scheme. Ellipsoids are drawn at 50% probability level.
Synthesis of bis salts 2a–c
All our experiments were conducted with dppm (dppm ¼ 1,2-
bis-diphenylphosphinomethane) as starting precursor. The
first step of the synthesis is analogous to that previously
reported except that two equivalents of bromine are employed.
Bromination takes place in dichloromethane at ꢀ78 1C to
6
.85 ppm). Analogously, the NH are significantly deshielded
(
6.86 and 6.75 ppm for 2a and 2b, respectively).
The bis salt formulation was corroborated by an X-ray
crystal structure analysis of 2b. Single crystals of this salt were
grown by diffusing hexanes (mixture of isomers) into a di-
chloromethane solution of the compound at room tempera-
ture. A view of one molecule of 2b is presented in Fig. 1 and
selected bond lengths and bond angles are listed in Table 1.
The most significant structural feature concerns the arrange-
ment of the two phenyls due to p-stacking (from 3.379 to
3
1
yield the bis(bromophosphonium) salt 1 quantitatively by
P
NMR spectroscopy. Adduct 1 which is only partially soluble
in dichloromethane at room temperature appears as a singlet
at d ¼ 48.0 ppm. In a second step, without further purification,
1
was reacted with two equivalents of a primary amine in the
presence of a base (2 equivalents) at ꢀ78 1C to yield the
corresponding salts 2a–c which precipitate from the solution.
4
6
˚
˚
3
.683 A, on average 3.534 A). y
3
In all cases Bu N can be employed because of the solubility of
its ammonium hydrobromide salt in THF which allows for its
easy removal. For 2c, the reaction can also be efficiently
conducted with four equivalents of aniline. Three different
amines were employed to vary the nature of the R-group on
nitrogen: isopropylamine, (S)-2-methyl-butylamine to extend
this methodology to the synthesis of enantiomerically pure
bis(iminophosphoranes) which are still unknown and aniline
to assess the effect of aromatic substituents (Scheme 2).
Salts 2a–c were characterized by conventional NMR tech-
Synthesis of mono salts 3a–c
Four protons are susceptible to removal upon deprotonation
of 2, those of the methylene bridge and those of the amine
groups, thus potentially opening an access to monocationic,
neutral, monoanionic and dianionic derivatives. In a first step,
compounds 2a–c were reacted with various bases, such as
3
Bu N (in excess) or MeLi (one equivalent) in THF at low
temperature. Each reaction cleanly yielded the corresponding
monocationic salt 3a–c which was obtained as an air and
moisture stable white solid after conventional work-up (see
Experimental section). A comparable monocationic derivative
was reported by Avis et al. as a by-product in a coordination
3
1
1
13
niques ( P, H, C) and data are fully consistent with the
3
1
formula proposed. In P NMR spectroscopy the three salts
a–c appear as a singlet at 33.7, 35.2, 29.7 ppm, respectively.
2
1
Two important pieces of data in the H NMR spectra are the
resonances of the bridging CH and that of the protons of the
4
7
reaction.
The abstraction of one proton only results in a weak
2
NH moiety. As expected, the methylene group appears as a
triplet, due to coupling with the two magnetically equivalent
phosphorus atoms, at rather high frequency (between 6.41 and
3
1
shielding in P NMR spectrum (about 3 ppm) and most
importantly, each compound appears as a singlet attesting to
a symmetrical structure in solution. However, two symmetri-
cal structures can be proposed which can not be distinguished
3
1
on the basis of these P NMR data alone. In the first
structure, deprotonation would have occurred at the nitrogen
atom to yield a salt in which one proton bridges the two
nitrogen atoms (form A). In the second structure, deprotona-
tion would have taken place on the methylene bridge to yield a
y CCDC reference numbers 619345–619349. For crystallographic data
in CIF or other electronic format see DOI: 10.1039/b610049j
Scheme 2 Synthesis of bis(aminophosphonium) salts 2a–c.
1
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˚
Table 1 Selected bond lengths (A) and angles (1) for 2b, 3a, 4c, 5c
and 6b
2b
3a
4c
5c
6b
P(1)–C(1)
P(2)–C(1)
P(1)–N(1)
P(2)–N(2)
P–Carom
1.828(3) 1.699(2) 1.830(2) 1.720(2) 1.686(2)
1.818(3) 1.690(2) 1.831(1) 1.722(2) 1.686(2)
1.606(3) 1.636(2) 1.566(1) 1.603(1) 1.634(2)
1.624(3) 1.633(2) 1.565(1) 1.597(1) 1.631(2)
1.790(3) 1.808(2) 1.810(2) 1.822(2) 1.833(2)
P(1)–C(1)–P(2) 119.6(2) 127.5(1) 115.97(7) 125.9(1) 133.6(1)
C(1)–P(1)–N(1) 114.3(1) 112.6(1) 113.57(7) 108.91(7) 102.6(1)
C(1)–P(2)–N(2) 110.3(1) 113.3(1) 113.95(6) 108.75(7) 102.0(1)
Fig. 3 Theoretical structure of compound IIIa.
NMR spectrum this signal can unambiguously be attributed to
1
13
a ‘‘CH’’ moiety. The H and C NMR data are then fully
consistent with ‘‘form B’’ for 3a–c. One may note that the
magnitude of the changes is less important between 2c and 3c.
Definitive evidence was given by an X-ray crystal structure
analysis of salt 3a. Single crystals of 3a were grown by
diffusing a solution of hexanes (mixture of isomers) into a
dichloromethane solution of the compound at room tempera-
ture. A view of one molecule of 3a is presented in Fig. 2
and the most significant bond metric parameters are listed in
Table 1.
Scheme 3 Synthesis of salts 3a–c.
salt in which two protons remain on the two nitrogen atoms
(
form B) (Scheme 3).
1
Interestingly, the H NMR spectra of 3a–c show that two
The most significant structural data concern the planarity of
the central carbon atom C(1) (S angles at C ¼ 359.91) and the
P(1)-C(1) and P(2)-C(1) bond distances which are rather short
˚
at 1.698(2) A compared to those recorded in the structure of
˚
compound 2b (1.83 A on average). On the other hand, the
protons reside on the nitrogen atoms and only one on the
carbon atom of the bridge. This proton which appears as a
triplet is strongly low frequency shielded at around 2.00 ppm
(
|Dd| 4 4 ppm compared to 2a–c) attesting to the increase of
electronic density on the carbon atom. In line with this
P(1)-N(1) and P(2)-N(2) bond lengths are not significantly
modified and are in good agreement with a single bond
character. DFT calculations were carried out on two models
of salts 2a,b and 3a,b, (respectively noted IIa and IIIa) in
which the alkyl groups were replaced by a methyl group. These
calculations were carried out using the ONIOM method by
using a combination of the B3PW91 functional associated
with the 6-31G* basis set for all atoms except those of the
phenyl which were computed using the UFF force field. A
view of the computed structure IIIa is presented in Fig. 3. A
good agreement was found between experimental and theore-
1
observation, the C NMR chemical shift of this carbon atom
3
in 3a–c is also strongly shielded (for example d ¼ 9.9 ppm in 3a
1
vs. 21.0 in 2a) and the signal exhibits a large JPC coupling
1
3
constant (138.0 Hz for 3a). Moreover, in the DEPT 135
C
tical data. Thus the P(1)-C(1) and P(2)-C(2) bond lengths at
˚
1
.714 A were found to be slightly longer that the experimental
values and the P–N bond lengths were found to be quite
˚
similar (1.669 A in IIIa).
NBO analysis which was carried out at the B3PW91/6-31G*
level of theory is informative. As expected examination of
NBO charges reveals that the central carbon atom has gained
electron density and the Wiberg bond indices show that the
bond order of the P–C bonds has increased (from 0.86 to 1.11
on going from IIa to IIIa) (Scheme 4).
Fig. 2 Molecular structure of compound 3a, showing the atomic
numbering scheme. The two methyl groups of the i-Pr substituents
have been omitted for clarity. Ellipsoids are drawn at 50% probability
level.
Synthesis of the neutral species 4a–c
Deprotonation of salts 2a–c was then carried out using two
equivalents of methyllithium in THF at ꢀ78 1C. Contrary to
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Scheme 4 NBO charges in theoretical structures of IIa and IIIa.
what we had expected, the formation of the corresponding
iminophosphoranes was not systematically observed and the
outcome of the reaction depends to a large extent on the
nature of the substituent at nitrogen.
Thus, reaction of 2a,b with methyllithium cleanly afforded
3
1
Fig. 4 Molecular structure of compound 4c, showing the atomic
compounds 4a,b which both appear in the P NMR spectrum
as singlets at d ¼ 27.1 and 26.8 ppm, respectively. These
chemical shifts are very unusual for iminophosphoranes (be-
tween ꢀ15 and 10 ppm in most cases) and close to that
recorded for the monocationic derivatives 3a–c. On the other
hand, double deprotonation of 2c yielded compound 4c whose
numbering scheme. Ellipsoids are drawn at 50% probability level.
methylene group to one nitrogen atom) during their studies
on the coordination behavior of the bis(iminophosphorane)
derivative [(ArNPQPh )CH ] (Ar ¼ p-Me-C H ) with rho-
2
2
6
4
3
1
11,47–51
P NMR chemical shift at d ¼ ꢀ2.8 ppm suggested that the
dium and platinum precursors.
Complexes resulting
1
3
expected bis(iminophosphorane) had been formed. C NMR
data of compounds 4a–c also indicate that, whereas only one
proton is present on the central carbon atom of the bridge in
compounds 4a,b (‘‘CH’’ signal at d ¼ 1.01 ppm in 4b for
from coordination of the bis(iminophosphorane) tautomeric
form were characterized in the crude reaction mixture by
NMR techniques but not isolated. On the basis of this and
our own results, one may conclude that the electron donating
capacity of the substituent at nitrogen is the predominant
factor in the (1,3) hydrogen shift. Alkyl groups favor the (1,3)
shift of one hydrogen atom of the methylene group to the
nitrogen atom.
2
example), compound 4c features a methylene group (‘‘CH ’’
1
triplet at d ¼ 29.2 ppm). Additionally, the H NMR spectra of
4
a,b also reveal the presence of a NH proton at d ¼ 6.99 and
6
.12 ppm, respectively, this was not found in 4c. This chemical
shift is close to those recorded for protons of amino groups in
compounds 2a–c and 3a–c, thus suggesting that this proton
bridges the two nitrogen atoms. Compounds 4a–c which were
isolated as white powders after usual work-up proved to be
very air and moisture sensitive.
In order to shed some light on this isomerization process,
DFT calculations were performed on compounds IVa and IVc
which feature a methyl or a phenyl group on the nitrogen
atom, respectively. For both compounds two forms were
considered, the bis(iminophosphorane) form (IVaA and IVcA)
Single crystals of compound 4c were grown by slowly
diffusing hexanes (mixture of isomers) into a THF solution
of the compound. As can be seen in Fig. 4 compound 4c is the
expected bis(iminophosphorane) derivative. The most signifi-
cant metric parameters of 4c are listed in Table 1. The bond
lengths are in good agreement with those previously reported
for similar structures. Note that the two hydrogen atoms on
the methylene bridge have been localized. As expected, a
and the tautomeric structure (IVaB and IVc ) in which the
B
proton was located between the two nitrogen atoms. These
calculations were carried out using the ONIOM method
(mixed QM/MM method). The phenyl groups at phosphorus
were computed using the UFF force field, all other atoms
being considered at the QM level using the B3PW91 functional
associated with the 6-31G* basis set. Single point calculations
were carried out on the optimized structures at the QM level
˚
lengthening of the P–C bond distances (1.815 A on average)
for all atoms (including those of the PPh groups). The results
2
is observed concomitantly with shortening of the P–N bond
˚
lengths (1.565 A on average) which has acquired a pseudo
of these calculations are summarized in Scheme 6. As can be
double bond character through negative hyperconjugation.
Compounds 4a,b could not be crystallized, and further
information could not be gained by performing variable
3
1
temperature P NMR experiments either. Indeed, the signal
of both compounds remained unmodified even at low tem-
perature indicating that a rapid exchange of the proton
between the two nitrogen atoms takes place. On the basis
of NMR data a tautomeric form can be proposed for com-
pounds 4a,b (see Scheme 5). The existence of this tautomeric
form is in fact not unprecedented. In 1990s, Elsevier and
coworkers observed a (1,3) shift of a proton (from the
Scheme 5 Synthesis of compounds 4a–c by deprotonation of salts
2a–c.
1
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Fig. 5 Molecular structure of compound 5c, showing the atomic
numbering scheme. Only the ipso carbon atoms of phenyl groups are
represented for clarity. Ellipsoids are drawn at 50% probability level.
Scheme 6 Respective free enthalpies of compounds IVa and IVc and
results of NBO calculations (in parentheses).
seen in both cases, theoretical results are qualitatively in good
agreement with experimental observations. That is, the
bis(iminophosphorane) form is more stable in both cases but
Hz in 5a). Anions 5a and 5b were found to be too moisture
sensitive to furnish satisfactory elemental data. Anion 5c
proved to be more reactive than its alkyl counterparts and
ꢀ
1
for R ¼ Ph by only 7.1 kJ mol , while the energy difference
ꢀ
1
31
for R ¼ Me increases to 33.9 kJ mol but in favour of the
shifted form. Despite several attempts, no transition state
connecting the two forms through a (1,3) hydrogen shift could
be located. Due to the size of the molecules no attempts were
made to modelize a bimolecular pathway.
characterization was limited to P NMR spectroscopy. How-
ever, its formulation was confirmed by an X-ray crystal
structure analysis. Single crystals of 5c were grown in ether
at room temperature. A view of one molecule is presented in
Fig. 5. The most significant metric parameters of 5c are listed
in Table 1. The anion is a monomeric structure where the
lithium cation is coordinated by the two nitrogen atoms, one
molecule of ether completing its coordination sphere. As can
be seen the 6-membered ring adopts a boat conformation and
the anionic carbon atom is planar (S angles ¼ 3581). Interest-
On the other hand, NBO calculations which were carried
out on form A reveal that the charge on the nitrogen atom is
slightly more negative in the case of the methyl derivative
(
Scheme 6).
˚
ingly, we note that the Li(1)-C(1) bond distance (2.578(3) A) is
Synthesis of the anions 5a–c
shorter than the sum of covalent radii but much longer than
In pursuing our investigations on the successive deprotonation
of salts 2 we found that the monoanionic salt of iminopho-
sphorane 5a–c could be easily generated in solution by reacting
those recorded in the structure of the tetrameric salts
˚
[
PhLi ꢂ (OEt) ] (2.27–2.32 A) and [MeLi ꢂ (OEt) ] (2.23–
2
4
2 4
˚
.27 A). Therefore the C–Li interaction in anion 5c is probably
2
2
a–c with three equivalents of MeLi in THF or Et O at
2
weak.
Salts 5a–c are not the first example of monoanionic deriva-
ꢀ78 1C. Anions 5 were isolated as white highly moisture
sensitive powders after solvent evaporation (Scheme 7).
tives of iminophosphoranes. Indeed, the first synthesis was
13
reported by Elsevier et al. in 1990, but the first structurally
Compounds 5a,b were characterized by NMR techniques
1
3
1
13
31
(
P, H, C). In P NMR 5a,b appear as singlets at around
0 ppm. The formation of the anion was also evidenced by
2 2
characterized anion [CH(PPh N-TMS) ] was only reported in
2
the early 2000s by Cavell and coworkers. In the solid state a
dimeric form was obtained when crystallization was carried
18
the appearance of a characteristic triplet at low frequency
1
1
(
d ¼ 0.86 ppm, JHP ¼ 3.0 Hz in 5a) in the H NMR spectrum
out in toluene, whereas a monomeric form was observed
3
which accounts for the presence of an anionic sp hybridized
1
carbon atom. In the C NMR spectra this carbon atom also
in the presence of solvents which can coordinate the alkali
52
center (THF).
3
1
resonates at low frequency (d ¼ 17.9 ppm with a J ¼ 143.5
PC
Synthesis of the dianions 6a–c
To complete this study we then explored the synthesis of
dianionic salts of iminophosphoranes from 2a–c. Only one
example of such dianion is known so far, reported indepen-
1
5,16
dently by Cavell’s and Stephan’s group in 1999.
It has
subsequently been used with great success by Cavell in the
synthesis of alkylidene or carbene complexes of several metal
centers (transition metals and lanthanides). We found that
dianions 6a–c were readily synthesized by reacting four
Scheme 7 Synthesis of salt anions 5a–c forms salts 2a–c.
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Scheme 8 Synthesis of salts dianions 6a–c from salts 2a–c.
equivalents of MeLi with salts 2a–c in diethyl ether (Scheme
). Here the use of ether as solvent turns out to be crucial as
obtained is presented in Fig. 6 and the most relevant bond
distances and bond angles are listed in Table 1. Despite several
attempts no X-ray diffraction quality crystals of 6a and 6c
were obtained. However the formulation of 6a and 6c as
dianions could be unambigously established by both hydro-
lysis and deuterolysis. Indeed, reaction of the dianion with
8
the same experiments carried out in THF at low temperature
only yielded monoanions 5a–c through deprotonation of the
solvent. Moreover addition of TMEDA (4 equivalents) was
necessary to obtain 6c.
As reported by Cavell and Stephan, these dianions are
highly sensitive towards moisture. Furthermore they were
2
H O led to the formation of the corresponding salt 2. The lack
1
of signal in the H NMR spectrum upon deuterolysis for the
‘‘methylene’’ bridge in 2D confirmed the quantitative forma-
tion of the dianions 6.
8 6 6
found to be poorly soluble in d -toluene or C D and com-
3
1
pounds 6a and 6c were characterised by P NMR spectro-
scopy only. The chemical shift of 6a (d ¼ 19.2 ppm) and 6b
Like its N-trimethylsilyl derivative anion 6b adopts a di-
(
d ¼ 18.5 ppm) are close to that reported by Cavell for the
2 4
meric structure which is organised around an C Li octa-
[
C(Ph
2
P ¼ N-TMS)
2
]
2
[Li
2
] dianion (d ¼ 13.7 ppm). Fortu-
hedron, each lithium atom being coordinated by the two
dianionic carbon atoms C(1) and C(36) and one nitrogen
atom of the iminophosphorane moieties. This structure is very
close to those reported by Cavell and Stephan and does not
deserve further comments.
3
1
nately dianion 6b ( P NMR d ¼ 18.5 ppm) proved to be
sufficiently soluble in d -benzene to be characterized also by
6
1
13
H and C NMR spectroscopies. The central PCP carbon
1
3
1
appears in the C spectrum as a triplet at 15.5 ( J ¼ 23.0
CP
Hz), which is very close to the chemical shift of the PCHP
carbon in the monoanion 5b. Suitable crystals of dianion 6b
for a X-ray crystallographic study were obtained by slowly
evaporating a diethyl ether solution. A view of the structure
Conclusion
A straighforward synthetic route allowing the synthesis of
dicationic derivatives of iminophosphoranes 2a–c has been
devised. Importantly, we showed that these salts can be used
as efficient precusors of cationic 3a–c, neutral 4a–c, anionic
5
a–c and dianionic derivatives 6a–c upon reaction with bases
such as methyllithium. This new synthetic approach opens the
way for a systematic investigation of the chemistry of alkyl
and aryl derivatives substituted derivatives. Further studies
aiming at investigating the synthesis and the use in catalysis of
transition metal complexes of these functional derivatives are
currently underway in our laboratories.
Experimental
General
All experiments were performed under an atmosphere of dry
nitrogen or argon using standard schlenk and glove box
techniques. Solvents were freshly distilled under argon from
Na/benzophenone (THF, diethylether, hexane), from P
2 5
O
(
dichloromethane, NEt ). Isopropylamine, DPPM, tributyl-
3
amine, (S)-3-methyl-2-butylamine, isopropylamine and aniline
were obtained from Aldrich and used without further purifica-
tion. Nuclear magnetic resonance spectra were recorded on
Bruker Avance 300 spectrometer operating at 300 MHz for
Fig. 6 Molecular structure of compound 6b, showing the atomic
numbering scheme. Only the carbon atom of the MeCH(i-Pr) group
linked to nitrogen and the ipso carbon atoms of the phenyl groups
have been represented for clarity. Ellipsoids are drawn at 50%
probability level.
1
13
31
1
13
H, 75.5 MHz for C and 121.5 MHz for P. H and
C
chemical shifts are reported in ppm relative to Me Si as
4
3
external standard. P are relative to a 85% H PO external
1
3
4
reference. Coupling constants are expressed in Hz. The
1
750 | New J. Chem., 2006, 30, 1745–1754
This journal is ꢁc the Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2006

View Article Online
following abbreviations are used: b, broad; s, singlet; d,
doublet; dd, doublet of doublets; t, triplet; m, multiplet; v,
virtual. Elemental analyses were performed by the ‘‘Service
d’analyse du CNRS’’, at Gif sur Yvette, France.
was washed with THF (2 ꢃ 20 mL). 2c was obtained as a white
solid after drying.
3
1
1
R ¼ Ph. 2c. Yield 68% (2.59 g). P { H} (CDCl
3
) d
P
29.7 (s,
2
P), 6.85
1
P). H (CDCl
2
3
) d
H
6.67 (2H, t, JHP ¼ 15.5 Hz, PCH
3
3
General procedure for the preparation of
bis(aminophosphonium) bromide 2a–c
(4H, v t, JHH ¼ 7.5 Hz, m-H (NPh)), 6.89 (2H, t, JHH ¼ 7.5
3
Hz, p-H (NPh)), 7.01 (4H, d, JHH ¼ 7.5 Hz, o-H (NPh)), 7.53
3
(
8H, br s, o-H (Ph
2
P)), 7.66 (4H, t,
J
HH ¼ 7.0 Hz, p-H
Preparation of DPPMBr
added dropwise to a solution of dppm (1.0 g, 2.61 mmol) in
CH Cl
(30 mL) at ꢀ78 1C. The cold bath was removed and
the reaction mixture was allowed to warm to room tem-
2
: Bromine (267 mL, 5.22 mmol) was
3
Ph P)), 8.18 (8H, dd, J
4
(
¼ 7.5 Hz, J ¼ 11.5 Hz m-H
HP
2
HH
13 1
Ph)), H of NH not observed. C { H} (CDCl ) d 23.8 (t,
(
1
3
C
2
2
1
JCP ¼ 59.0 Hz, PCH P), 118.4 (d, J ¼ 103.5 Hz, C
2
CP
ipso
2
(
(
(
(
Ph P)), 119.8 (t, J ¼ 4.0 Hz, o-CH (NPh)), 123.7 (s, p-CH
2
3
1
1
2
CP
perature giving rise to a white precipitate. P { H} (CH
2 2
Cl )
NPh)), 129.4 (s, m-CH (NPh)), 130.0 (t, JCP ¼ 7.0 Hz, o-CH
d
P
48 (s).
3
Ph
Ph
2
P)), 133.8 (t, JCP ¼ 6.1 Hz, m-CH (Ph
2
P)), 135.5 (s, p-CH
2
P)), 118.4 (s, Cipso NPh). Anal. Calc. for C37
H
2 2 2
34Br N P :
Method 1. Bu N (1.24 mL, 5.22 mmol) and the amine (5.22
3
C, 61.01; H, 4.70; N, 3.85. Found: C, 61.17; H, 4.63; N, 3.98.
mmol) were added to a solution of DPPMBr
2
at ꢀ78 1C.
While warming the reaction mixture to room temperature, the
suspension disappeared. Stirring was maintained for 2 h at
General procedure for the preparation of monocations 3a–c
Method 1. Bu N (108 mL, 0.46 mmol) was added to a
3
2 2
room temperature, then CH Cl was removed under vacuum.
solution of bis(aminophosphonium) 2a–b (0.152 mmol) in
The residue was washed with THF (2 ꢃ 20 mL) and 2 was
CH
2
Cl
2
(5mL) cooled to ꢀ78 1C. After removal of the cold
obtained as a white solid after drying.
bath, the reaction mixture was stirred for 30 min at room
temperature. Then CH Cl was evaporated in vacuum and the
i
31
1
2
2
R ¼ Pr. 2a: Yield 68% (2.13 g). P { H} (CDCl
3
) d
P
33.7 (s,
1
P). H (CDCl
3
residue was washed with ether (2 ꢃ 20 mL). In each case, the
monocation 3a–b was recovered as a white solid after drying.
3
) d
H
0.94 (12H, d, JHH ¼ 6.5 Hz, Me), 3.02 (2H,
2
br s, NCH), 6.41 (2H, t, JHP ¼ 16.0 Hz, PCH
2
P), 6.86 (2H,
3
2
3
dd, JHP ¼ 10.0 Hz, JHH ¼ 6.4 Hz, NH), 7.57 (8H, dd, JHP
¼
i
31
1
R ¼ Pr. 3a. Yield 67% (0.059 g). P { H} (CDCl
3
) d
P
30.6
3
3
1
3.5 Hz, JHH ¼ 7.0 Hz, o-H (Ph
2
P)), 7.70 (4H, t, JHH ¼ 7.0
1
s, P). H (CDCl
3
(
3
) d
H
1.00 (12H, d, JHH ¼ 6.5 Hz, Me), 1.94
4
3
Hz, p-H (Ph
2
P)), 7.96 (8H, dd, JHP ¼ 13.5 Hz, JHH ¼ 7.0 Hz,
2
(
1H, t, JHP ¼ 4.0 Hz, PCHP), 2.94 (2H, br s, NCH), 5.44 (2H,
1
P)). C { H} (CDCl
3
1
1
m-H (Ph
PCH
2
3
) d
C
21.0 (t, JCP ¼ 63.0 Hz,
4
br s, NH), 7.23 (8H, v t, JHH ¼ 7.0 Hz, m-H (Ph
2
P)), 7.37 (4H,
3
2
P), 22.3 (t, JCP ¼ 2.5 Hz, Me), 45.3 (br s, NCH), 118.2
4
3
t, JHH ¼ 7.0 Hz, p-H (Ph
2
P)), 7.47 (8H, dd, JHP ¼ 12.0 Hz,
1
2
(
d, J ¼ 104.0 Hz, C
(Ph P)), 127.8 (t, J ¼ 7.0 Hz,
3
13
P)). C { H} (CDCl
1
1
CP
ipso
3
2
CP
J
¼
¼
HH ¼ 7.0 Hz, o-H (Ph
2
) d
3 C
9.9 (t, JCP
o-CH (Ph P)), 131.9 (t, J ¼ 6.0 Hz, m-CH (Ph P)), 133.3
3
2
2
CP
2
138.0 Hz, PCHP), 24.7 (t, JCP ¼ 2.5 Hz, Me), 45.4 (t, JCP
(
s, p-CH (Ph P)). Anal. Calc. for C H Br N P : C, 56.38;
2
2
31 38
2
2 2
2.5 Hz, NCH), 128.5 (t, J ¼ 6.5 Hz, m-CH (Ph P)), 131.8
CP
2
H, 5.80; N, 4.24. Found: C, 56.11; H, 6.02; N, 4.16.
3
(
s, p-CH (Ph P)), 132.3 (t, J ¼ 5.5 Hz, o-CH (Ph P)), C
2
CP
2
ipso
of Ph P not observed. Anal. Calc. for C H BrN P : C, 64.25;
2
3
1
1
31 37
2 2
R ¼ CH(CH
3 3 2
)CH(CH ) . 2b. Yield 61% (1.10 g). P { H}
H, 6.44; N, 4.83. Found: C, 64.43; H, 6.28; N, 5.02.
1
3
(
CDCl ) d 35.2 (s, P). H (CDCl
3
P
3
) d
H
0.60 (6H, d, JHH ¼ 6.5
3
Hz, NCHMe), 0.64 (6H, d, J ¼ 7.0 Hz, CHMe ), 0.74 (6H,
31
HH
2
R ¼ CH(CH )CH(CH ) . 3b. Yield 78% (0.075 g).
P
3
3 2
1
3
d, J
3
¼ 7.0 Hz, CHMe ), 1.34 (2H, hept d, J
¼ 6.5 Hz,
1
3
HH
2
HH
{ H} (CDCl ) d 31.7 (s, P). H (CDCl ) d 0.69 (6H, d, J
3
P
3
H
HH
4
3
3
JHP ¼ 3.0 Hz, CHMe ), 2.66 (2H, qd, J
¼ 7.0 Hz, J
¼
3
2
HH
HP
¼ 7.0 Hz, NCHMe), 0.85 (6H, d, J
¼ 7.0 Hz, CHMe ),
3
HH
2
2
4
.0 Hz, NCH), 6.75 (2H, br s, NH), 6.85 (2H, t, J ¼ 16.5
HP
3
0.94 (6H, d, J ¼ 7.0 Hz, CHMe ), 1.55 (2H, qd, J ¼ 7.0
HH
3 2
2
HH
3
3
Hz, PCH
2
P), 7.54 (8H, dt, JHH ¼ 7.5 Hz, JHP ¼ 14.0 Hz, o-H
Hz, J
¼ 5.0 Hz, NCHMe), 2.11 (1H, t, J ¼ 6.0 Hz,
HP
2
HP
3
(
3
Ph
2
P)), 7.72 (2H, t, JHH ¼ 7.5 Hz, p-H (Ph
2
P)), 7.73 (2H, t,
3
PCHP), 2.68 (2H, br s, CHMe
2
), 5.35 (2H, br d, JHP ¼ 10.0
3
J
HH ¼ 7.5 Hz, p-H (Ph
2
P)), 7.91 (8H, dt, JHH ¼ 7.5 Hz, JHP
3
Hz, NH), 7.31 (8H, v t, JHH ¼ 7.0 Hz, m-H (Ph
2
P)), 7.44 (4H,
1
3
1
¼
13.0 Hz, m-H (Ph
2
P)). C { H} (CDCl
), 20.2 (s, CHMe ), 22.5 (t, JCP
), 55.8 (br s,
) d
3 C
15.3 (s,
3
3
t, JHH ¼ 7.0 Hz, p-H (Ph
2
P)), 7.53 (8H, dt, JHH ¼ 7.0 Hz,
1
NCHMe), 16.6 (s, CHMe
2
3
2
¼
3
13 1
P)). C { H} (CDCl
1
J
HP ¼ 8.5 Hz, o-H (Ph
2
3
) d
C
9.8 (t, JCP
6
2.0 Hz, PCH
2
P), 34.8 (t, JCP ¼ 4.5 Hz, CHMe
2
¼
141.0 Hz, PCHP), 17.4 (s, CHMe ), 20.1 (s, NCHMe), 34.4
2
1
1
NCH), 117.7 (d, JCP ¼ 109.0 Hz, Cipso (Ph
2
P)), 123.1 (d, JCP
2
3
(
t, JCP ¼ 3.0 Hz, NCH), 54.3 (br s, t, JCP ¼ 2.0 Hz, CHMe
2
),
2
¼
98.0 Hz, Cipso (Ph P)), 129.5 (t, JCP ¼ 7.0 Hz, m-CH
3
2
128.5 (t, J ¼ 5.5 Hz, m-CH (Ph P)), 131.8 (s, p-CH (Ph P)),
CP
2
2
2
3
(
Ph P)), 129.9 (t, J ¼ 7.0 Hz, o-CH (Ph P)), 133.2 (t, J
¼
3
2
CP
2
CP
131.9 (s, p-CH (Ph P)), 132.4 (t, J ¼ 5.5 Hz, o-CH (Ph P)),
2
CP
2
3
6
1
C
.0 Hz, m-CH (Ph P)), 134.9 (t, J ¼ 6.0 Hz, m-CH (Ph P)),
3
2
CP
2
132.7 (t, JCP ¼ 5.5 Hz, o-CH (Ph P)), C
of Ph P not
2
2
ipso
35.1 (s, p-CH (Ph P)), 135.4 (s, p-CH (Ph P)). Anal. Calc. for
2
2
observed. Anal. Calc. for C H BrN P : C, 66.14; H, 7.14; N,
35 45 2 2
35
H
46Br
N
2 2
P
2
: C, 58.67; H, 6.47; N, 3.91. Found: C, 58.83;
4
.41. Found: C, 66.06; H, 7.22; N, 4.33.
H, 6.62; N, 4.05.
Method 2
Method 2. Aniline (843 ml, 10.4 mmol) was added to the
R = Ph. MeLi (234 mL, 0.375 mmol) was added to a
solution of DPPMBr at ꢀ78 1C. The precipitate disappeared
suspension of the bis(aminophosphonium) 2c (0.273 g, 0.375
mmol) in THF (5 mL) at ꢀ78 1C. The cold bath was removed
and the resulting solution was stirred for an additional hour at
2
and the reaction mixture was stirred for 2 h at room tempera-
ture. Then CH Cl was removed under vacuum. The residue
2
2
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New J. Chem., 2006, 30, 1745–1754 | 1751

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1
room temperature. After concentration under vacuum, mono-
cation 3c slowly precipitated as a white solid which is filtrated
out of the solution and washed with diethylether (3 ꢃ 10 mL).
Hz, o-CH (Ph
2
P)), 126.4 (d, JCP ¼ 114.0 Hz, Cipso–(Ph
CP ¼ 5.0 Hz, m-CH (Ph P)), 132.0 (v s,
Cipso–(Ph P)), 151.0 (b s, C –(NPh)).
2
P)),
2
132.1 (t,
J
2
2
ipso
3
1
1
1
3
a. Yield 73% (0.177 g). P { H} (CDCl ) d 26.6 (s, P). H
3
P
2
General procedure for the preparation of monoanions 5a–c
(
CDCl ) dH 2.09 (1H, t, J ¼ 4.0 Hz, PCHP), 6.70 (2H, br t,
3
HP
3
3
JHH ¼ 8.0 Hz, m-H (NPh)), 6.93 (4H, br d, J
¼ 8.0 Hz,
MeLi (350 mL, 0.56 mmol) was added to a suspension of
bis(aminophosphonium) 2a–c (0.19 mmol) in THF (5 mL) at
ꢀ78 1C. The cold bath was then removed and the resulting
solution was stirred for 3 h at room temperature. The solvent
HH
3
o-H (NPh)), 6.98 (4H, br t, JHH ¼ 8.0 Hz, m-H (NPh)), 7.27
3
4
(
3
8H, dt, JHH ¼ 8.0, JHP ¼ 2.0 Hz, m-H (Ph
2
P)), 7.42 (4H, t,
3
3
J
HH ¼ 7.5 Hz, p-H (Ph
2
P)), 7.68 (8H, dd, JHH ¼ 8.0, JHP ¼
13 1
3.0 Hz, o-H (Ph P)), 8.89 (2H, br s, NH). C { H} (CDCl
8
1
2
3
)
was then carefully removed in vacuo, THF-d was added and
1
1
d
C
C
14.9 (t, JCP ¼ 128.0 Hz, PCHP), 115.3 (d, JCP ¼ 42.0 Hz,
monoanion 5a–c was characterized.
2
ipso–(NPh)), 120.0 (t, JCP ¼ 3.5 Hz, o-CH (NPh)), 121.7 (s,
1
Method
i
p-CH (NPh)), 126.7 (d, JCP ¼ 114.0 Hz, Cipso–(Ph
2
P)), 128.5
31
1
8
1
8
4
P
R = Pr. 5a. P { H} (THF-d ) d 21.2 (s, P). H (THF-d )
(
(
(
s, m-CH (NPh)), 128.8 (t, J ¼ 6.5 Hz, m-CH (Ph P)), 132.4
CP
2
2
3
3
3
d
H
0.86 (1H, t, JHP ¼ 3.0 Hz, PCHP), 1.05 (12H, d, JHH ¼
t, J ¼ 1.5 Hz, m-CH (NPh)), 132.5 (t, J ¼ 5.5 Hz, o-CH
CP
CP
3 3
.0 Hz, Me), 3.18 (2H, hept d, JHH ¼ 6.0 Hz, JHP ¼ 19.5 Hz,
3 3
6
Ph P)), 141.0 (s, p-CH (Ph P)). Anal. Calc. for
2
2
NCHMe
2
), 7.26 (8H, t, JHH ¼ 7.5 Hz, JHH ¼ 7.0 Hz, o-H
C H BrN P : C, 68.63; H, 5.14; N, 4.33. Found: C, 68.55;
33
3
7
2 2
3
(
Ph
2
P)), 7.34 (4H, t, JHH ¼ 7.5 Hz, p-H (Ph
2
P)), 7.59 (8H, t,
H, 5.01; N, 4.11.
1
3
1
8
1
m-H (Ph
2
P)). C { H} (THF-d ) d
C
17.9 (t, JCP ¼ 143.5 Hz,
3
2
General procedure for the preparation of
bis(iminophosphoranes) 4a–c
PCHP), 28.8 (t, J ¼ 6.0 Hz, Me), 46.1 (t, J ¼ 3.0 Hz,
CP
CP
2
J
NCHMe ), 127.5 (t,
2
¼ 5.0 Hz, o-CH (Ph P)), 129.0
CP
2
3
J
(
s, p-CH (Ph P)), 131.9 (t,
2
¼ 4.5 Hz, m-CH (Ph P)),
CP
2
MeLi (300 mL, 0.48 mmol) was added to a suspension of
bis(aminophosphonium) 2a–c (0.24 mmol) in THF-d (2 mL)
1
3
8
140.6 (dd, JCP ¼ 85.0 Hz, JCP ¼ 1.5 Hz, Cipso–Ph
P).
2
3
1
1
8
at ꢀ78 1C. The resulting solution was stirred overnight at
R ¼ CH(CH
3
)CH(CH
8
3
)
2
P
. 5b. P { H} (THF-d ) d 20.5
(s, P). H (THF-d ) d 0.76 (t, 6H, J
8
1
4
room temperature. After evaporation of the solvent, THF-d
¼ 7.0 Hz, CHMe ),
H
HH
2
4
0.84 (6H, J
4
was added and the iminophosphorane 4a–c was characterized.
¼ 6.5 Hz, NCHMe), 0.89 (6H, J
¼ 7.0 Hz,
HH
HH
3
4
CHMe
CHMe
2
2
), 1.48 (2H, hept d, JHH ¼ 7.0 Hz, JHP ¼ 4.0 Hz,
Method
3 3
), 2.90 (2H, qd,
J
HH ¼ 6.5 Hz,
J
HP ¼ 16.0 Hz,
i
31
1
8
1
8
R = Pr. 4a. P { H} (THF-d ) d
dH 0.82 (1H, br s, PCHP), 0.96 (12H, d, JHH ¼ 5.0 Hz, Me),
.19 (2H, br s, NCH), 6.99 (1H, br s, NH), 7.32 (12H, br s, o-H
P
27.1 (s, P). H (THF-d )
3
NCHMe), 7.21 (8H, t,
3
4H, t, J
J
HH ¼ 6.5 Hz, m-H (Ph
2
P)), 7.28
3
3
(
¼ 6.5 Hz, p-H (Ph P)), 7.52 (8H, dt, J
¼ 6.5
HH
2
HH
3
3
13
1
8
Hz, J ¼ 14.0 Hz, o-H (Ph P)). C { H} (THF-d ) d 16.5
1
3
1
HP
2
C
and p-H (Ph P)), 7.67 (8H, br s, m-H (Ph P)). C { H} (THF-
2
2
1
2
(
s, CHMe ), 16.3 (t, J ¼ 65.5 Hz, PCHP), 19.5 (t, J ¼ 5.0
3
8
1
2
CP
CP
d ) d 9.2 (v s, J not measurable, PCHP), 27.1 (br s, Me),
C
CP
Hz, NCHMe), 20.0 (s, CHMe ), 36.4 (t,
2
J
¼ 5.5 Hz,
CP
4
5.2 (br s, NCH), 128.0 (br s, o-CH Ph
Ph P)), 132.1 (br s, m-CH (Ph P)), CH of PCHP and Cipso of
P not observed.
2
P), 130.1 (s, p-CH
2
4
CHMe
2
), 54.9 (t, JCP ¼ 3.5 Hz, NCHMe), 126.9 (t, JCP
¼
(
2
2
4
4
.0 Hz, m-CH (Ph
(
2
2
P)), 127.0 (t,
5
J
CP ¼ 3.5 Hz, m-CH
Ph
2
V)
(
(
Ph
P
)), 128.5 (v t,
J
CP ¼ 1.5 Hz, p-CH (Ph
2
P)), 131.4
3
3
J
3
1
1
8
t,
J
CP ¼ 4.5 Hz, o-CH (Ph
2
P)), 131.5 (t,
CP ¼ 5.0 Hz,
R ¼ CH(CH )CH(CH ) . 4b. P { H} (THF-d ) d 26.8
3
3
2
P
2
1
8
3
o-CH (Ph
2
(
2
P)), 139.4 (d, JCP ¼ 21.5 Hz, Cipso–(Ph
2
P), 140.7
(
s, P). H (THF-d ) d 0.73 (6H, d, J
¼ 7.0 Hz, CHMe ),
H
HH
2
3
.79 (6H, d, J
3
d, JCP ¼ 21.0 Hz, Cipso–(Ph
2
P).
0
¼ 6.5 Hz, CHMe ), 0.81 (6H, d, J
¼ 7.0
HH
2
HH
2
Hz, NCHMe), 1.01 (1H, t, J ¼ 4.0 Hz, PCHP), 1.51 (2H,
HP
R ¼ Ph. This deprotonation process was preferentially
3
4
hept d, JHH ¼ 7.0 Hz, JHP ¼ 2.5 Hz, CHMe
2
), 2.98 (2H, br q,
conducted in Et O as solvent. As anion 5c proved to be more
2
3
J
HH ¼ 6.5 Hz, NCH), 6.12 (1H, br s, NH), 7.31–7.40 (12H, m,
reactive than its alkyl counterparts, its characterization was
31
3 3
o-H, p-H (Ph
2
P)), 7.73 (8H, td, JHH ¼ 8.0 Hz, JHH ¼ 11.0
limited to P NMR spectroscopy exclusively.
31
1
3
1
8
1
Hz, m-H (Ph
2
P)). C { H} (THF-d ) d
C
10.1 (t, JCP ¼ 134.0
1
8
5
P
c. P { H} (THF-d ) d 15.0 (s, P).
Hz, PCHP), 17.2 (br s, CHMe
3
2
), 19.3 (br s, NCHMe), 35.3 (t,
3
J
CP ¼ 5.5 Hz, NCHMe), 53.9 (t, JCP ¼ 2.5 Hz, CHMe
2
),
General procedure for the preparation of dianions 6a–c
3
2
1
27.3 (t, JCP ¼ 4.0 Hz, o-CH (Ph
2
P)), 127.5 (t, JCP ¼ 4.0 Hz,
Method 1. MeLi (330 mL, 0.53 mmol) was added to a
suspension of bis(aminophosphonium) 2a–c (0.13 mmol) in
3
o-CH (Ph P)), 129.6 (br s, p-CH (Ph P)), 131.8 (t, J ¼ 2.5
2
2
CP
3
Hz, m-CH (Ph P)), 131.9 (t, J ¼ 2.5 Hz, m-CH (Ph P)),
2
CP
2
Et O (5 mL) at ꢀ78 1C. The mixture was warmed to room
1
3
2
1
37.9 (dd, J ¼ 96.0 Hz, J ¼ 1.5 Hz, C –(Ph P)).
CP
CP
ipso
2
temperature and stirred for 3 d at this temperature. The
solvent was removed under vacuum to yield a white solid.
3
1
1
8
1
8
R ¼ Ph. 4c. P { H} (THF-d ) d ꢀ2.8 (s, P). H (THF-d )
P
2
3
P), 6.58 (6H, v d, JHH
d
8
H
4.12 (2H, t, JHP ¼ 14.0 Hz, PCH
2
¼
i
31
1
R ¼ Pr. 6a. P { H} (Et
R ¼ CH(CH )CH(CH
2
P
O) d 19.2 (s, P).
3
.0 Hz, o-H and p-H (NPh)), 6.88 (4H, JHH ¼ 8.0 Hz, m-H
3
31
1
(
3
NPh)), 7.39 (8H, b t, JHH ¼ 7.0 Hz, m-H (Ph
2
P)), 7.49 (4H, t,
3
3
3
)
2
. 6b. P { H} (Et
2
O) d
P
18.5 (s,
0.53 (d, 6H, JHH ¼ 6.7
¼ 7.0 Hz, CHMe ), 0.78 (2H,
3
1
3
J
HH ¼ 7.0 Hz, p-H (Ph
2
P)), 7.91 (8H, dd, JHH ¼ 7.0 Hz, JHP
P). (C ) d 20.2 (s, P). H (C
D
6 6
6
D
6
) d
H
1
3
1
8
1
3
Hz, CHMe ), 0.59 (d, 6H, J
¼
11.0 Hz, o-H (Ph P)). C { H} (THF-d ) d 29.2 (t, J
¼
2
C
CP
2
HH
2
2
3
6
1.5 Hz, PCH P), 116.2 (s, p-CH (NPh)), 122.9 (t, J ¼ 3.5
m, CHMe ), 1.38 (6H, J ¼ 6.5 Hz, NCHMe), 3.18 (2H, m,
2
CP
2
HH
2
13 1
NCHMe), 6.78–7.74 (20H, Ph). C { H} (C D ) d 15.5
Hz, o-CH (NPh)), 127.7 (s, m-CH (NPh)), 128.0 (t, J ¼ 6.0
CP
6
6
C
1
752 | New J. Chem., 2006, 30, 1745–1754
This journal is ꢁc the Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2006

View Article Online
Table 2 Crystallographic data
Compound
2b
3a
4c
5c
6b
Empirical formula
Molecular weight
Crystal system
Space group
C
35
H
46
N
2
P
2
,C
4
H
8
O, 2Br
C
31
H
37
N
2
P
2
,C
4
H
8
O,Br
C
37
H
32
N
2
P
2
C
41
H
41LiN
646.64
Monoclinic
P2 /c
2
OP
2
C
70
H
84Li
1207.17
Monoclinic
P2
4 4 4 4 10
N P ,C H O
788.60
Orthorhombic
P2
11.1170(10)
18.7140(10)
18.9410(10)
90.00
90.00
90.00
3940.6(5)
4
1.329
2.170
12 758
8375
0.0260
6923
437
0.0758
0.0342
0.0348; 0.0000
1.038
651.58
Monoclinic
P2 /n
11.0500(10)
17.6970(10)
17.8390(10)
90.00
97.3220(10)
90.00
3460.0(4)
4
1.251
1.309
11 954
6778
0.0362
4610
380
0.0809
0.0364
0.0335; 0.0000
0.955
566.59
Monoclinic
P2 /c
14.2200(10)
10.2780(10)
20.4620(10)
90.00
93.9270(10)
90.00
2983.6(4)
4
1.261
0.175
12 293
6826
0.0174
5522
376
0.1102
0.0379
2
1 1
2
1
1
1
1
1
˚
a/A
15.7990(10)
10.9450(10)
20.5520(10)
90.00
98.3490(10)
90.00
3516.2(4)
4
1.222
18.3440(10)
16.7080(10)
25.5700(10)
90.00
106.4060(10)
90.00
7517.9(7)
4
1.067
˚
b/A
˚
c/A
a/1
b/1
g/1
3
˚
V/A
Z
ꢀ
1
3
r/g cm
m/cm
Reflections collected
ꢀ
0.158
0.142
16 600
10 259
0.0297
6982
430
0.1341
0.0463
29 363
29 363
24 710
1553
Independent reflections
R
int
Reflections used
Parameters refined
wR2 [I 4 2S(I)]
R1 [I 4 2S(I)]
Weights a, b
GoF
0.1020
0.0393
ꢀ0.04(3)
0.0569; 0.5967
1.055
0.0639; 0.2055
1.057
0.0598; 0.0000
0.998
0.238(0.040)
Difference
Peak/hole/e A
0.659(0.057)/ꢀ
0.275(0.057)/ꢀ
0.286(0.039)/ꢀ
0.934(0.053)/ꢀ
ꢀ
3
˚
0.295(0.057)
0.304(0.057)
0.371(0.039)
0.427(0.053)
/ꢀ0.242(0.040)
1
0
65
Shelxl-97. ORTEP drawings were made using ORTEP III
(
t, JCP ¼ 23.0 Hz, PCP), 17.2 (s, CHMe
2
), 19.5 (AXX , SJCP
6
6
¼
15.3 Hz, NCHMe), 21.5 (s, CHMe
2
), 34.9 (s, CHMe
s, NCHMe), 127.1 (d, JCP ¼ 5.0 Hz, m-CH (Ph P)), 128.1 (d,
P)), 129.0 (s,
2
), 54.0
for Windows.
4
(
2
4
J
CP ¼ 5.0 Hz, m-CH (Ph
2 2
P)), 128.7 (s, p-CH (Ph
0
Acknowledgements
p-CH (Ph
2
P)), 131.5 (AXX , SJCP ¼ 14.8 Hz, o-CH (Ph
2
P)),
0
0
1
39.1 (AXX , SJCP ¼ 122.4 Hz, Cipso–(Ph
2
P), 140.2 (AXX ,
The authors thank the CNRS and the Ecole Polytechnique for
financial support of this work. IDRIS (Project No. 061616) is
also acknowledged for allowance of computational time.
SJCP ¼ 125.5 Hz, Cipso–(Ph
2
P).
Method 2
R = Ph. In this case, the deprotonation was conducted in
presence of TMEDA (4 equivalents). The formed dianion
precipitated out of the solution and was isolated by filtration
and washing with ether. Because of its insolubility, dianion 6c
could not be characterized by NMR but indirectly by addi-
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This journal is ꢁc the Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2006