Synthesis, reactivity and X-ray crystal structure of an uncomplexed 1-phosphabarrelene: Application to the synthesis of 1,1′-bis(dimethylsilylphosphinine)ferrocenes

Article abstract of DOI:10.1039/b103779j

The 5,6-diphenyl-3-tertiobutyl-1,2-azaphosphinine 3 reacts with bis(phenylethynyldimethylsilyl)ferrocene, 2, to afford a mixture of the phosphinine 4, resulting from the cycloaddition of 3 with one alkynyl group of 2, and 1-phosphabarrelene, 5, whose formation results from an intramolecular [4+2] cycloaddition between the remaining alkynyl group of the ferrocenyl ligand and the 1,4-phosphabutadienic system of 4. The X-ray structure of compound 5 was obtained and shows no particular strain in the molecule. Competitive experiments have shown that, at high temperature, phosphinine 4 equilibrates with barrelene 5. Synthesis of a bidentate ligand 6, incorporating two dimethylsilyl-substituted phosphinines, was achieved by reacting the azaphosphinine 3 with half an equivalent of the ferrocene derivative 2. The mixed ligand 8, incorporating two different phosphinine subunits, was also prepared using a two-step sequence by reacting a mixture of 4 and 5 with diazaphosphinine 1. This reaction first produced an intermediate azaphosphinine-phosphinine ligand 7, which was then trapped with trimethylsilylacetylene to afford ligand 8.

Full text of DOI:10.1039/b103779j

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Synthesis, reactivity and X-ray crystal structure of an uncomplexed
1-phosphabarrelene: application to the synthesis of
1,1º-bis(dimethylsilylphosphinine)ferrocenes
Sebastien Welfele, Nicolas Mezailles, Nicole Maigrot, Louis Ricard, Francois Mathey* and
Pascal Le Floch*
L aboratoire Heteroelements et Coordination (CNRS UMR 7653), Ecole Polytechnique,
91128 Palaiseau cedex, France. E-mail: leÑoch=poly.polytechnique.fr
Received (in Montpellier, France) 26th April 2001, Accepted 27th June 2001
First published as an Advance Article on the web 4th September 2001
The 5,6-diphenyl-3-tertiobutyl-1,2-azaphosphinine 3 reacts with bis(phenylethynyldimethylsilyl)ferrocene, 2, to
a†ord a mixture of the phosphinine 4, resulting from the cycloaddition of 3 with one alkynyl group of 2, and
1-phosphabarrelene, 5, whose formation results from an intramolecular [4 ] 2] cycloaddition between the
remaining alkynyl group of the ferrocenyl ligand and the 1,4-phosphabutadienic system of 4. The X-ray structure of
compound 5 was obtained and shows no particular strain in the molecule. Competitive experiments have shown
that, at high temperature, phosphinine 4 equilibrates with barrelene 5. Synthesis of a bidentate ligand 6,
incorporating two dimethylsilyl-substituted phosphinines, was achieved by reacting the azaphosphinine 3 with half
an equivalent of the ferrocene derivative 2. The mixed ligand 8, incorporating two di†erent phosphinine subunits,
was also prepared using a two-step sequence by reacting a mixture of 4 and 5 with diazaphosphinine 1. This
reaction Ðrst produced an intermediate azaphosphinine-phosphinine ligand 7, which was then trapped with
trimethylsilylacetylene to a†ord ligand 8.
It has been shown that the delocalized structure of
phosphinines1,2 is very sensitive towards the substitution
pattern of the ring. Thus, the replacement of a CH unit by a
nitrogen atom,3 the inclusion of the ring in a fused system
containing a more aromatic neighbor,4 or the complexation of
the phosphorus atom lone pair5 have been shown to reinforce
the dienic and/or the dienophilic character of the ring. Various
types of adducts resulting from [4 ] 2] cycloaddition of 1,3-
dienes at the P2C double bond or of alkynes at the 1-
phosphabutadienyl skeleton of phosphinines have thus been
characterized.5,6 Reactions involving unactivated phos-
phinines in such [4 ] 2] cycloaddition processes are very rare.
To the best of our knowledge, the unique known example was
provided by the groups of Markl and Ashe who reported the
successful synthesis of 1-phosphabarrelenes from the reaction
of 2,6-disubstituted-4-phenylphosphinines or from the parent
compound C H P with the highly electron-deÐcient alkynes
hexaÑuoro-2-butyne and dicyanoethylene (Scheme 1).7
Herein we will demonstrate that intramolecular constraints
can be exploited to favor the reversible formation of 1-
phosphabarrelenes from unactivated phosphinines. Addi-
tionally, we also report on the synthesis of a new type of
phosphinine-based bidentate ligand incorporating a ferrocenyl
spacer.
skeleton to give phosphinines via a [4 ] 2] cycloaddition/
cyloreversion sequence. The general scheme of these syntheses
is summarized in Scheme 2.
As part of a program aimed at exploring the elaboration of
sophisticated phosphinine-based bidentate ligands, we recent-
ly expanded our studies to the synthesis of 1,1@-substituted fer-
rocenyl derivatives. 1,1@-Bis(phosphino)substituted ferrocenes
are indeed a class of phosphorus bidentate ligands that has
found a very wide range of applications in the Ðeld of homo-
geneous catalysis.9 As previously noted in our works, the use
of silyl-substituted alkynes is a determining factor that allows
regioselective cycloaddition processes onto diazaphosphinine
1. Therefore, we Ðrst turned our attention toward the synthe-
sis of the 1,1@-bis(phenylethynyl)ferrocene 2.10 Its preparation
was readily achieved by reacting the 1,1@-dilithioferrocene
with two equivalents of (phenylethynyl)chlorodimethylsilane
(Scheme 3).11
In order to test the reactivity of 1 towards diyne 2, our Ðrst
experiments focused on the synthesis of a monodentate ligand.
Reaction of equimolar amounts of monoazaphosphinine 3,
and precursor 2 led to a quite unexpected result. Contrary to
what was expected, the phosphinine 4, resulting from the
cycloaddition of 3 with one alkyne function of 2, was not
exclusively formed (Scheme 4). In addition to the very charac-
teristic signal of 4 at low Ðeld (d \ 244.0 in toluene), the
31P-NMR spectrum of the crude reaction mixture indicated
the presence of a second compound 5 whose signal appeared
at high Ðeld ([43.0 ppm in toluene) with a comparable inten-
sity. Whatever the conditions used (concentration, duration)
further heating of this mixture did not modify the ratio
between 4 and 5. Whereas the formulation of 4 could be
unambiguously conÐrmed on the basis of NMR data, that of 5
remained unclear. The two most signiÐcant pieces of data
were obtained from the mass spectrum, which indicated that
compound 5 has the same molecular weight as phosphinine 4,
and by the 1H-NMR spectrum, which reveals the presence of
5
5
Results and discussion
We recently reported some synthetic strategies allowing the
preparation of phosphinine-based bi- and tridentate ligands
and macrocycles.8 All these approaches rely on the reactivity
of 1,3,2-diazaphosphinines and 1,2-azaphosphinines such as 1
towards alkynes and diynes. Being substantially less aromatic
than phosphinines (see discussion above),2 these compounds
behave as 1,4-dipoles through their 1,2-phosphaazabutadiene
1264
New J. Chem., 2001, 25, 1264È1268
DOI: 10.1039/b103779j
This journal is ( The Royal Society of Chemistry and the Centre National de la Recherche ScientiÐque 2001

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Scheme 1 Synthesis of phosphabarrelenes from phosphinines and
hexaÑuoro-2-butyne.
four sets of magnetically inequivalent cyclopentadienyl
protons (see Experimental).
The formulation of 5 was deÐnitively established by an
X-ray crystal structure analysis. The structure of one molecule
of 5 is shown in Fig. 1; crystallographic data are collected in
Table 1. As can be seen, compound 5 is a 1-phosphabarrelene
resulting from the intramolecular [4 ] 2] cycloaddition of
phosphinine 4 with the second alkyne function of the fer-
rocenyl substituent. Contrary to what might be thought at
Ðrst sight, the structure of 5 is not particularly strained. Thus,
in the ferrocenyl unit, which adopts an eclipsed conformation,
the two cyclopentadienyl ligands are roughly coplanar
(H \ 4¡). Moreover, in the phosphabarrelene backbone, PÈC
bond distances are nearly equivalent (average 1.863 A).
Fig. 1 ORTEP view of one molecule of phosphabarrelene 5. Dis-
placement ellipsoids are shown at the 50% probability level. The
numbering is arbitrary and di†erent from that used in the NMR
spectra. Selected bond distances (A) and angles (¡) are as follows.
P1ÈC1, 1.864(2); P1ÈC5, 1.868(2); P1ÈC6, 1.860(2); C1ÈC2, 1.342(2);
C2ÈC3, 1.538(2); C3ÈC4, 1.544(2); C4ÈC5, 1.335(2); C6ÈC7, 1.345(2);
C3ÈC7, 1.533(2); C1ÈSi1 1.877(2); Si1ÈC8, 1.865(2): C1ÈP1ÈC5,
95.62(6); P1ÈC1ÈC2, 112.9(1); P1ÈC5ÈC4, 113.4(1); C1ÈC2ÈC3,
118.0(1); C2ÈC3ÈC4, 108.5(1); C4ÈC3ÈC7, 108.4(1); P1ÈC6ÈC7,
115.0(1); C6ÈP1ÈC5, 96.41(6); C6ÈP1ÈC1, 96.86(7); C6ÈC7ÈC3,
115.8(1); P1ÈC1ÈSi1, 116.03(8); C1ÈSi1ÈC8, 104.30(7).
Finally, bond lengths and bond angles in the two dimethylsilyl
linkers fall in the usual range.
The formation of 5 thus raises several questions. First of all,
it appears that 5 is the unique example of a stable phos-
phabarrelene resulting from the reaction of an unactivated
phosphinine and alkyne. Indeed, whatever the conditions used
(temperature, amount of reagents), additional experiments
carried out by heating a series of 2-trimethylsilyl-substituted
phosphinines with various phenyl- and silyl-substituted
alkynes exclusively led to the recovery of the starting com-
pounds. This tends to show that the formation of 5 is favored
by geometrical factors. A second important point concerns the
isolation of phosphinine 4, which is the ““openÏÏ form of 5.
Competitive experiments showed that 4 and 5 equilibrate in
solution. Variable temperature 31P-NMR experiments
allowed us to extract the thermodynamic values *S¡ and *H¡
associated with this equilibrium. The transition state between
Scheme
2
General scheme describing the synthetic approach
towards phosphinine-based bidentate ligands.
Scheme 3
Table 1 Crystallographic data and data collection details for com-
pound 5
Empirical formula
Formula weight
C
808.93
H
FePSi É C H
45 41
2
6
12
T /K
150.0(1)
Triclinic
P1
Crystal system
Space group
a/A
b/A
c/A
a/¡
11.197(5)
12.256(5)
16.462(5)
83.370(5)
80.060(5)
67.750(5)
2056.4(14)
2
b/¡
c/¡
U/A
Ž
3
Z
k/cm~1
0.500
16 825
11 913
Total reÑect.
Indep. ReÑect.
R
0.0298
0.0399, 0.1107
int
Final R , wR [I [ 2p(I)]
1
2
Scheme 4
New J. Chem., 2001, 25, 1264È1268
1265

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the geometry of the diyne employed is particularly well suited
to achieve an intramolecular [4 ] 2] cycloaddition, it is prob-
able that many other types of functional diynes could display
the same behavior. Additionally, we also synthesized a new
type of bis-phosphinine ligand including a ferrocenyl spacer.
Studies aimed at exploring their coordination chemistry as
well as their use in homogeneous catalysis are currently
underway in our laboratory.
Scheme 5
4 and 5 being highly ordered, a high negative value of [35
e.u. was calculated, as expected. A *H¡ of [8.9 kJ mol~1 was
found, leading to an equilibrium constant K¡ of 0.52 (Scheme
5). As additional evidence, conÐrming the equilibrium between
4 and 5, we found that 1-phosphabarrelene 5 could be used as
a precursor for the synthesis of the bis-phosphinine 6 upon
reaction with an equivalent of monoazaphosphinine 3. Fol-
lowing a more straightforward route, compound 6 can also be
prepared by reacting two equivalents of azaphosphinine 3
with one equivalent of 2 as depicted in Scheme 6.
Characterization of 6 was achieved by 1H and 13C-NMR
spectroscopy, elemental analysis and mass spectrometry. In
order to expand the scope of this study, we also investigated
the synthesis of mixed ferrocenyl ligands incorporating two
di†erent phosphinine subunits. Following our discovery, syn-
thesis of the bis(phosphinine) 8, including 2-dimethylsilyl-
3,5,6-triphenylphosphinine and 2,6-bis-silylated-3-phenylphos-
phinine subunits, could be achieved using a one-pot sequence.
Reaction of a mixture of 4 and 5, prepared as described above,
with one equivalent of diazaphosphinine 1 yielded interme-
diate 7 whose formulation was unambiguously established on
the basis of the 31P-NMR spectrum. The presence of the aza-
phosphinine unit is evidenced by a strongly deshielded singlet
at 304.0 ppm whereas the chemical shift of the phosphinine
Experimental
General procedures
All reactions were routinely performed under an inert atmo-
sphere of nitrogen by using Schlenk techniques and dry
deoxygenated solvents. Dry THF, hexanes and toluene were
obtained by distillation from Na/benzophenone. Dry Celite
was used for Ðltration. Nuclear magnetic resonance spectra
were recorded on a Bruker AC-200 SY spectrometer. Chemi-
cal shifts are expressed in parts per million downÐeld from
external TMS (1H and 13C) and 85% H PO (31P), and coup-
3
4
ling constants are given in hertz. Mass spectra were obtained
at 70 eV with an HP 5989 B spectrometer coupled with an
HP 5890 chromatograph by the direct inlet method. The fol-
lowing abbreviations are used: s, singlet; d, doublet; t, triplet;
m, multiplet; v, virtual. Elemental analyses were performed by
the ““Service dÏAnalyse du CNRSÏÏ, Gif sur Yvette, France.
Syntheses
Bis(phenylethynyldimethylsilyl)ferrocene, 2. A solution of
butyllithium (38.4 mL, 54 mmol, 1.6 mol L~1 in hexane) was
added at room temperature to a solution of ferrocene (5.0 g,
27 mmol) in hexane (100 mL) and TMEDA (8.05 mL, 54
mmol). The reaction mixture was then heated at 60 ¡C for 1 h.
A small volume of THF (10 mL) was then added to solubilize
a part of the dilithio derivative and the mixture was the
cooled to [80 ¡C. Phenylethynyldimethylchlorosilane (10.5 g,
54 mmol) was added and the resulting mixture was then
slowly warmed to room temperature. After 1 h stirring at
25 ¡C, Celite (5.0 g) was added to the mixture and the solvents
were evaporated. The coated Celite was then loaded onto the
top of a silica gel packed Ñash column for chromatography. A
Ðrst fraction eluted with hexane yielded unreacted ferrocene. A
second fraction eluted with a mixture of hexaneÈtoluene
(90 : 10) yielded compound 2, which was recovered as an
orange solid. Yield: 9.50 g (70%). 1H-NMR (200 MHz,
subunit is identical to that recorded for compound
4
(d \ 244.0 in toluene). Further heating of this mixture with
trimethylsilylacetylene cleanly a†orded the expected
bis(phosphinine) 8 (Scheme 7) which was characterized by
NMR techniques, mass spectroscopy and elemental analyses.
In conclusion, we have shown that proximity e†ects can
overcome the energetic barrier provided by the aromaticity of
phosphinines. This led to the isolation and structural charac-
terization of a stable 1-phosphabarrelene. Though in this case
CDCl ): d 0.51 (s, 12H, SiMe ), 4.31 (vt, AA@BB@, 4H, &J
\
3
2
HH
14.3, C H ), 4.31 (vt, AA@BB@, 4H, &J \ 14.3, C H ), 7.34È
HH
5
4
5 4
7.58 (m, 10H, C H ). 13C-NMR (50 MHz, CDCl ): d [0.7 (s,
6
5
3
Scheme 6
SiMe ), 69.3 (s, C
of C H ), 73.0 (s, CH of C H ), 74.3
2
ipso
5
4
5 4
C H ), 93.9 (s, C of alkyne), 106.2 (s, CÈSi of alkyne), 123.8 (s,
5
ipso
4
C
of C H ), 128.9, 129.2, 132.6 (s, CH of C H ). MS m/z
(ion, relative intensity): 502 (M [ 10), 401 (M [ CCPh, 100).
Anal. calc. for C
6
5
6 5
H
FeSi , MW \ 502.5: C, 71.69; H, 6.02;
30 30
2
found: C, 71.75; H, 6.08%.
Phosphinine, 4, and phosphabarrelene, 5. Diazaphosphinine
(1 mmol) in toluene (20 mL) was reacted with
1
diphenylacetylene (0.178 g, 1 mmol) at 110 ¡C for 15 h. A
31P-NMR control indicated the complete formation of aza-
phosphinine 3. Diyne 2 (0.50 g, 1 mmol) was then added to the
reaction mixture and the resulting solution was heated at
110 ¡C for 30 h. Celite (2 g) was then added and the solvent
was evaporated, yielding a brown powder that was then
deposited onto the top of a silica gel column. A Ðrst fraction
eluted with a mixture of hexaneÈtoluene (90 : 10) yielded
traces of unreacted diyne 2 and phosphabarrelene 5. Com-
pound 5 was easily separated from unreacted diyne by
washing with methanol. A second fraction eluted with the
same solvent yielded a mixture of barrelene 5 phosphinine 4.
Finally, a last fraction eluted with a mixture of hexaneÈ
toluene (85 : 15) yielded traces of bis(phosphinine) 6. Washing
Scheme 7
1266
New J. Chem., 2001, 25, 1264È1268

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with hexanes (3 ] 25 mL) allowed separation of barrelene 5
and phosphinine 4 (only 4 is soluble in hexanes). Following
this procedure, compounds 4 and 5 were recovered as orange
powders.
lets at d 31P 304.0 (azaphosphinine subunit) and 244.0
(phosphinine subunit). Additional traces of unreacted diaza-
phosphinine 1 could also be detected. Trimethylsilylacetylene
(0.28 mL, 2 mmol) was then added to the reaction mixture and
the resulting solution was heated at 90 ¡C for 24 h. The
solvent was then evaporated in the presence of Celite (2 g).
The brown solid obtained was deposited onto the top of a
silica gel column for chromatography. A fraction eluted with
hexane allowed the separation of traces of the 2,6-bis(tri-
methylsilyl)phosphinine formed by reaction of 1 with excess
4. Yield: 255 mg (35%). 31P-NMR (81 MHz, CDCl ): d
3
242.0. 1H-NMR (200 MHz, CDCl ): d 0.38 (d, 6H, 4J \ 1.8,
3
PH
SiMe ), 0.43 (s, 6H, SiMe ), 4.08 (vt, AA@BB@, 2H, &J \ 3.4,
2
2
HH
C H ), 4.18 (vt, AA@BB@, 2H, &J \ 3.4, C H ), 4.30 (vt,
HH
AA@BB@, 2H, &J \ 3.4, C H ), 4.43 (vt, AA@BB@, 2H, &J
HH HH
3.4, C H ), 7.12È7.35 (m, 25H, C H ). 13C-NMR (50 MHz,
5
4
5 4
\
5
4
5
4
6 5
CDCl ): d 0.7 (s, SiMe ), 1.5 (s, 3J \ 11.4, SiMe ), 72.5 (s,
PC
C H ), 72.6 (s, C H ), 74.1 (s, C H ), 74.9 (s, C H ), 93.9 (s,
trimethylsilylacetylene. A second fraction eluted with a
3
2
2
mixture of hexaneÈtoluene (60 : 40) allowed isolation of the
5
4
5
4
5
4
5 4
3CÈSi), 106.3 (s, 3 C); 127.2È137.2 (m, C H ), 135.4 (d, 3J
PC
of C H ),
\
bis(phosphinine) 8, which was recovered as an orange solid.
6
5
16.5, C4), 142.5 (s, C
143.2 (s, C
of C H ), 142.7 (s, C
Yield: 460 mg (55%). 31P-NMR (81 MHz, CDCl ): d 261.0
ipso
of C H ), 146.1 (d, 2J \ 9.6, C or C ), 153.4
PC
(s, 2J \ 12.6, C or C ), 168.0 (d, 1J \ 73.7, C or C ),
PC PC
6
5
ipso
3
6
5
3
(disilyl-substituted phosphinine) and 242.0. 1H-NMR (200
ipso
6
5
5
MHz, CDCl ): d 0.40 (d, 12H, 4J \ 1.7, SiMe ), 0.45 (d, 9H,
3
5
2
6
3
PH
2
168.2 (d, 1J \ 72.1, C or C ). MS m/z (ion, relative
3J \ 2.8, SiMe ), 3.99 (pt, AA@BB@, 2H, &J \ 3.4, C H ),
PC
2
6
PH
4.04 (pt, AA@BB@, 2H, &J \ 3.4, C H ), 4.27 (pt, AA@BB@, 2H,
HH
&J \ 3.4, C H ); 4.30 (pt, AA@BB@, 2H, &J \ 3.4, C H ),
HH HH
7.16È7.45 (m, 22H, H of phosphinines and C H ), 8.01 (d,
3
HH
5 4
intensity): 726 (M [ 100). Anal. calc. for C
MW \ 724.8: C, 74.57; H, 5.70; found: C, 74.68; H, 5.71.
H
FePSi ,
45 41
2
5 4
5
4
5 4
5: Yield: 255 mg (35%). 31P-NMR (81 MHz, CDCl ): d
3
4
6 5
[42.0. 1H-NMR (200 MHz, CDCl ): d [0.37 (s, 6H, SiMe ),
J
\ 1.2, H of bis(silyl)phosphinine). MS m/z (ion, relative
3
2
PH
5
0.54 (s, 6H, SiMe ), 3.86 (m, 2H, C H ), 4.27 (m, 2H, C H ),
intensity): 868 (M [ 100). Anal. calc. for C
H
FeP Si ,
2
5
4
5
4
51 52
2 2
4.38 (m, 2H, C H ), 4.84 (m, 2H, C H ), 5.74 (d, 1H, 4J
PH
1.5, C of phosphinine), 7.08È7.31 (m, 20H, C H ). 13C-NMR
\
MW \ 838.92: C, 73.02; H, 6.25; found: C, 73.30; H, 6.15%.
5
4
5 4
4
6 5
X-Ray crystallography
(50 MHz, CDCl ): d [0.4 (d, 3J \ 7.2, SiMe ), 1.7 (d,
PC
3J \ 7.2, SiMe ), 55.4 (d, 3J \ 3.0, C of barrelene), 70.5 (s,
3
2
Single crystals of compound 5 suitable for X-ray crystallog-
raphy were obtained by di†using cyclohexane into a dichloro-
methane solution of the compound in a tube. Data were
collected on a Nonius Kappa CCD di†ractometer using an
Mo-Ka (j \ 0.710 70 A) X-ray source and a graphite mono-
chromator. Experimental details are described in Table 1. The
crystal structures were solved using SIR 9712 and SHELXL-
97.13 ORTEP drawings were made using ORTEP III for
Windows.14
PC
2
PC
4
C H ), 71.9 (s, C H ), 75.3 (s, C H ), 75.5 (s, C H ) 75.6 (s,
5
4
4
5
4
5
4
5
ipso
4
C H ), 126.8È130.5 (m, CH of C H ), 141.0 (s, C
of C H ),
5
6
5
6 5
141.4 (d, 1J \ 64.4, C of barrelene), 141.6 (d, 1J \ 92.3,
PC
7
PC
C
of barrelene), 144.0 (d, 2J \ 2.8, C
144.7 (d, 2J \ 30.6, C of barrelene), 155.1 (s, C
of barrelene),
2, 6
PC
3, 5
of C H ),
PC
PC
8
ipso
ipso
6 5
170.9 (d, J \ 2.7, C
of C H ). MS m/z (ion, relative
6 5
intensity): 725 (M [ 1, 100). Anal. calc. for C
H
FePSi ,
45 41
2
MW \ 724.8: C, 74.57; H, 5.70; found: C, 74.75; H, 5.82%.
CCDC reference number 168236. See http://www.rsc.org/
suppdata/nj/b1/b103779j/ for crystallographic data in CIF or
other electronic format.
Bis(phosphinine), 6. A solution of azaphosphinine 3 (1
mmol), prepared as described above, was reacted with diyne 2
(0.25 g, 0.5 mmol) at 110 ¡C for 50 h. After this period, a 31P
NMR spectrum of the reaction mixture showed formation of
bis(phosphinine) 6. Celite (2 g) was then added to the reaction
mixture. The resulting mixture was evaporated to dryness,
yielding a brown powder that was deposited onto the top of a
silica gel column for chromatography. A Ðrst fraction eluted
Acknowledgements
This work was supported by the Centre National de la
Recherche ScientiÐque and by the Ecole Polytechnique.
with
a
mixture of hexaneÈtoluene (90 : 10) yielded
References
bis(phosphinine) 6, which was recovered as an orange solid.
Yield: 310 mg (65%). 31P-NMR (81 MHz, CDCl ): d 242.0.
1
For general reviews on phosphinine chemistry, see: (a) G. Markl,
in Multiple Bonds and L ow Coordination in Phosphorus Chem-
istry, ed. M. Regitz and O. J. Scherer, Georg Thieme Verlag,
Stuttgart, 1990, p. 220; (b) K. B. Dillon, F. Mathey and J. F.
Nixon, Phosphorus: T he Carbon Copy, Wiley, Chichester, 1998;
(c) N. Mezailles, F. Mathey and P. Le Floch, Prog. Inorg. Chem.,
2001, 49, 455.
3
1H-NMR (200 MHz, CDCl ): d 0.45 (d, 12H, 4J \ 1.7,
3
PH
SiMe ), 4.10 (pt, AA@BB@, 4H, &J \ 3.4, C H ), 4.35 (pt,
2
HH
AA@BB@, 4H, &J \ 3.4, C H ), 7.21È7.47 (m, 32H, H and
HH
C H ). 13C-NMR (50 MHz, CDCl ): d 2.1 (d, 3J \ 11.4,
PC
SiMe ), 72.2 (s, C H ), 74.0 (s, C H ), 127.0È131.0 (m, C H ),
5 4
5
4
4
6
5
2
3
5
4
5
4
6 5
135.5 (d, 3J \ 16.5, C ), 142.2 (s, C
PC
of C H ), 143.0 (s, C
of C H ), 142.5 (s,
2
3
For articles discussing the aromatic behavior of phosphinines,
see: (a) J. Waluk, H.-P. Klein, A. J. Ashe III and J. Michl,
Organometallics, 1989, 8, 2804; (b) G. Frison, A. Sevin, N. Avar-
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(a) G. Markl and G. Dorfmeister, T etrahedron L ett., 1987, 28,
1093; (b) G. Markl, C. Dorges, T. Riedl, F. G. Klarner and C.
Lodwig, T etrahedron L ett., 1990, 31, 4589; (c) G. Markl and S.
Dorsch, T etrahedron L ett., 1995, 36, 3839; (d) G. Markl and C.
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11978.
4
ipso
of C H ), 146.1 (d, 2J \ 9.2, C
PC
or C of phosphinine), 153.4 (d, 2J \ 12.3, C or C of
PC
phosphinine), 168.0 (d, 1J \ 73.7, C or C of phosphinine),
PC
168.2 (d, 1J \ 72.0, C or C of phosphinine). MS m/z (ion,
PC
6 5
C
ipso
6
5
ipso
6
5
3
5
5
3
2
6
6
2
relative intensity): 948 (M [ 30). Anal. calc. for
C
H
FeP Si , MW \ 947.02: C, 76.10; H, 5.53; found: C,
60 52
2 2
76.40; H, 5.68%.
Bis(phosphinine), 8. A solution of azaphosphinine 3 (1
mmol) in toluene (10 mL), prepared as described above, was
heated with diyne 2 (0.50 g) at 110 ¡C in toluene. After 30 h,
the 31P NMR spectrum of the crude mixture showed the for-
mation of phosphinine 4 and phosphabarrelene 5 in equal
amounts. A solution of diazaphosphinine 1 (1 mmol) in
toluene (10 mL) was then added to this mixture and the
resulting solution was heated at 110 ¡C. After 25 h, the reac-
tion was complete and the 31P NMR spectrum showed the
presence of intermediate 7, which is characterized by two sing-
4
5
(a) G. Markl and K. H. Heier, T etrahedron L ett., 1974, 49–50,
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1971, 17, 1249.
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L. Ziegler and B. Nuber, Angew. Chem., Int. Ed. Engl., 1987, 26,
1134; ( f ) N. Mezailles, L. Ricard, F. Mathey and P. Le Floch,
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1267

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