Synthesis and rearrangement of diphosphorus analogues of amidinium salts

Article abstract of DOI:10.1021/ja010347h

Transient diphosphinocarbocations IIP are generated either by addition of phosphenium salts to the stable [bis(diisopropylamino)phosphino](silyl)carbene or by chloride abstraction from C-phosphino-P-chloro phosphorus ylides. In contrast to their nitrogen anlogues (amidinium salts) IIN, which feature a planar 3-center-4p-electron system, calculations show that IIP should exist as IIPb, in which one phosphorus is planar, while the other remains pyramidal. With small substituents at phosphorus, derivatives of type IIP rearrange by a 1,3-shift of a phosphorus substituent to the other phosphorus center to give C-phosphoniophosphaalkenes. When bulky substituents are present at phosphorus, derivatives IIP undergo ring closure, giving rise to the corresponding cyclic valence isomers IIIP, in which the carbon atom bears a negative charge. Diphosphinocarbocations IIP can be trapped by acetonitrile giving regioselectively the corresponding [2 + 3] cycloadduct.

Full text of DOI:10.1021/ja010347h

Published on Web 02/26/2002
Synthesis and Rearrangement of Diphosphorus Analogues of
Amidinium Salts
Tsuyoshi Kato,† Heinz Gornitzka,† Antoine Baceiredo,†
Wolfgang W. Schoeller,*,‡ and Guy Bertrand*,†,§
Contribution from the Laboratoire d’He´te´rochimie Fondamentale et Applique´e, UMR CNRS
5069, UniVersite´ Paul Sabatier, 118, route de Narbonne, F-31062 Toulouse Cedex 04, France,
Fakulta¨t fu¨r Chemie der UniVersita¨t, Postfach 10 01 31, D-33615 Bielefeld, Germany, and
UCR-CNRS Joint Research Chemistry Laboratory, UMR 2282, Department of Chemistry,
UniVersity of California, RiVerside, California 92521-0403
Received February 7, 2001. Revised Manuscript Received October 29, 2001
Abstract: Transient diphosphinocarbocations IIP are generated either by addition of phosphenium salts to
the stable [bis(diisopropylamino)phosphino](silyl)carbene or by chloride abstraction from C-phosphino-P-
chloro phosphorus ylides. In contrast to their nitrogen anlogues (amidinium salts) IIN, which feature a planar
3-center-4p-electron system, calculations show that IIP should exist as IIPb, in which one phosphorus is
planar, while the other remains pyramidal. With small substituents at phosphorus, derivatives of type IIP
rearrange by a 1,3-shift of a phosphorus substituent to the other phosphorus center to give C-
phosphoniophosphaalkenes. When bulky substituents are present at phosphorus, derivatives IIP undergo
ring closure, giving rise to the corresponding cyclic valence isomers IIIP, in which the carbon atom bears
a negative charge. Diphosphinocarbocations IIP can be trapped by acetonitrile giving regioselectively the
corresponding [2 + 3] cycloadduct.
Scheme 1
Introduction
Nitrogen-substituted carbocations, namely the iminium IN,
amidinium IIN, and guanidinium ions, are well-known stable
species, which have found widespread use in synthetic chem-
istry, biological processes, and molecular materials science1
(Scheme 1). Contrastingly, for the heavier analogues, only the
“monophosphorus”-substituted cations, the highly reactive
methylenephosphonium ions IP, have been isolated;2 no ex-
perimental studies had been undertaken before this work3
concerning the bis- and trisphosphinocarbenium ions.4
The origin of the stability of the aminocarbocations lies in
the π-donation of the nitrogen lone pair into the formally unfilled
2p(π)-orbital of the adjacent carbon center, which overcom-
pensates the σ-attracting effect due to the electronegativity of
† Universite´ Paul Sabatier.
‡ Fakulta¨t fu¨r Chemie der Universita¨t.
§ University of California.
(1) (a) Olah, G. A.; Schleyer, P. v. R. Carbonium Ions; Wiley: New York,
1976. (b) Volkmann, R. A. In ComprehensiVe Organic Synthesis; Trost,
B. M., Ed.; Pergamon Press: Oxford, 1991; Vol. 1, pp 355-396. (c) Olah,
G. A. Angew. Chem., Int. Ed. Engl. 1995, 34, 1393. (d) Saunders: M.;
Jime´nez-Vazquez, H. A. Chem. ReV. 1991, 91, 375. (f) Ehmann, A.;
Gompper, R.; Hartmann, H.; Mu¨ller, T. J. J.; Polborn, K.; Schu¨tz, R. Angew.
Chem., Int. Ed. Engl. 1994, 33, 572. Hannon, C. L.; Anslyn, E. V. In
Bioorganic Chemistry Frontiers; Dugas, H., Ed.; Springer-Verlag: Berlin,
1993; pp 193-255.
(2) (a) Igau, A.; Baceiredo, A.; Gru¨tzmacher, H.; Pritzkow, H.; Bertrand, G.
J. Am. Chem. Soc. 1989, 111, 6853. (b) Guerret, O.; Bertrand, G. Acc.
Chem. Res. 1997, 30, 486. (c) Gru¨tzmacher, H.; Pritzkow, H. Angew. Chem.,
Int. Ed. Engl. 1991, 30, 709.
(3) For a preliminary account of this work, see: Kato, T.; Gornitzka, H.;
Baceiredo, A.; Schoeller, W. W.; Bertrand, G. Science 2000, 289, 754.
(4) For a theoretical study of tris(phosphanyl)carbenium ions: Schoeller, W.
W.; Tubbesing, U. Inorg. Chem. 1998, 37, 3183.
nitrogen. According to Schleyer et al.,5 “the inherent π donor
capabilities of the heavier elements are as large as or larger
(5) Kapp, J.; Schade, C.; El-Nahasa, A. M.; Schleyer, P. v. R. Angew. Chem.,
Int. Ed. Engl. 1996, 35, 2236.
9
2506 VOL. 124, NO. 11, 2002 J. AM. CHEM. SOC.
10.1021/ja010347h CCC: $22.00 © 2002 American Chemical Society

Diphosphorus Analogues of Amidinium Salts
A R T I C L E S
Scheme 2
Scheme 3
than their second row counterparts”, and since phosphorus is
more electropositive than carbon, and of course nitrogen,
phosphinocarbocations should be more stable than their amino
analogues. However, Schleyer et al also stated that “the
apparently superior ability of nitrogen to act as a π donor is
due, in part, to the ease in achieving the optimum planar
configurations with sp2 hybridization” (inversion barriers at
B3LYP/6-31g* level: PH3, 37.3 kcal mol-1; NH3, 5.8 kcal
mol-1).
On the basis of calculated energies of isodesmic reactions,
replacing one hydrogen atom of IN by an additional amino
group further stabilizes the amidinium salt IIN by about 44 kcal/
mol.6 Interestingly, introduction of a second phosphino group
only stabilizes IIP over IP by 12 kcal/mol.7 Amidinium salts
IIN adopt a planar structure due to the 3-center-4π-electron
system, while it was predicted for IIP that a similar structure,
IIPa, would not even be a minimum on the potential energy
surface. Depending on the level of calculation, it was found
that either one (IIPb)8 or two phosphorus centers (IIPc)7b would
be pyramidalized (Scheme 1). This is due to the electropositivity
of the phosphino groups, which shifts a surplus of electron
density to the central atom, preventing the π-donation and
therefore the planarization of the phosphorus atom(s). Interest-
ingly, calculations on the parent compounds showed that IIP
was not the global minimum on the P2CH5 hypersurface.7b The
unsymmetrical three-membered ring VP and the phosphonio-
phosphaalkene IVP9 were found to be lower in energy than IIP,
while the symmetrical three-membered heterocycle IIIP was
predicted to be by far the least stable isomer. Surprisingly, we
have recently found3 that when a dichloromethane solution of
bis(diisopropylamino)phosphenium trifluoromethanesulfonate10
was added to a pentane solution of the carbene 111 at 0 °C,
neither IIP1 nor its rearranged isomers IVP1 and VP1 were
obtained, but instead, their three-membered heterocycle isomer
IIIP1 was isolated as extremely air-sensitive white crystals (66%
yield) (Scheme 1).
This experimental observation is at first glance in total
contradiction to the theoretical predictions drawn from the parent
system P2CH5. Therefore, it was of interest to investigate the
role of the substituents on the fate of the reaction. Moreover,
two mechanisms could account for the formation of IIIP1.
Indeed, phosphenium salts are known to react with multiple
bonds to give the corresponding three-membered rings.12 Since
the phosphinocarbene 1 features phosphorus-carbon multiple
bond character,11c the formation of compounds IIIP1 might
result from a concerted [2 + 1] cycloaddition. Alternatively,
IIIP1 could come from the ring closure of the primary formed
allylic type cation IIP1. The demonstration of the latter
hypothesis would prove that derivative IIIP1 results from a
“cascade stabilization” of the electron deficient carbocation
center: the first phosphorus atom gives electrons to the
carbocationic center and becomes positively charged and,
therefore, highly electrophilic, and the second phosphorus atom
then acts as a Lewis base toward the first. The overall process
transforms the carbocationic center into a carbanionic center.
Since this type of transformation is unlikely to be unique, it
should be of significant synthetic utility (Scheme 2).
Here, we report evidence for the transient formation of bis-
(phosphino)carbocations of type IIP, as well as their rearrange-
ment into isomers of types IIIP and IVP.
Results
Bis(dicyclohexylamino)phosphenium triflate and the cyclic
phosphenium salt 213 react with carbene 1 to give IIIP2 and
IIIP3, respectively (Scheme 3). Salt IIIP2 was not stable enough
to be isolated but was identified in solution by 31P NMR
spectroscopy. Indeed, its three-membered ring structure was
clearly indicated by a characteristic high field14 AB system
centered at 8.0 ppm (1JPP ) 130 Hz). The triflate salt of
heterocycle IIIP3 was isolated as a yellow oil in 30% yield. Its
ionic nature was indicated by its very low solubility in nonpolar
solvents. Apart from the characteristic high-field 31P NMR AB
system at 7.5 ppm (1JPP ) 164 Hz), a doublet of doublets
corresponding to the carbon bonded to the two phosphorus atoms
13
was observed in the C NMR spectrum (dC ) 67.7 ppm, JPC
) 5.2 and 7.1 Hz), confirming the presence of two magnetically
nonequivalent phosphorus nuclei. A single-crystal X-ray dif-
fraction analysis of the corresponding gallium tetrachloride salt
definitively proved the structure (vide infra).
Since the abstraction of chloride from P-chloro phosphorus
ylides is a known method for obtaining the corresponding
methylenephosphonium salts IP,2c the C-phosphino-P-chloro
phosphorus ylide 3 was prepared by adding 1 equiv of the
corresponding chlorophosphine to a pentane solution of the
carbene 1 (Scheme 4). [Note that the more crowded bis-
(diisopropylamino) and bis(dicyclohexylamino)chloro phos-
phines do not react with the carbene 1.] Addition of aluminum
(6) Gobbi, A.; Frenking, G. J. Am. Chem. Soc. 1993, 115, 2362.
(7) (a) Frenking, G.; Fau, S.; Marchand, C. M.; Gru¨tzmacher, H. J. Am. Chem.
Soc. 1997, 119, 6648. (b) Gru¨tzmacher, H.; Marchand, C. M. Coord. Chem.
ReV. 1997, 163, 287.
(8) This work.
(9) A few examples of phosphoniophosphaalkenes IVP have been synthe-
sized: Gru¨tzmacher, H.; Pritzkow, H. Angew. Chem., Int. Ed. Engl. 1989,
28, 740.
(10) Cowley, A. H.; Cushner, M. C.; Szobota, J. S. J. Am. Chem. Soc. 1974,
100, 7784.
(11) (a) Igau, A.; Gru¨tzmacher, H.; Baceiredo, A.; Bertrand, G. J. Am. Chem.
Soc. 1988, 110, 6463-6466. (b) Igau, A.; Baceiredo, A.; Trinquier, G.;
Bertrand, G. Angew. Chem., Int. Ed. Engl. 1989, 28, 621-622. (c)
Bourissou, D.; Guerret, O.; Gabbai, F. P.; Bertrand, G. Chem. ReV. 2000,
100, 39. (d) Buron, C.; Gornitzka, H.; Romanenko, V.; Bertrand, G. Science,
2000, 288, 834.
(12) Sanchez, M.; Mazie`res, M. R.; Lamande´, L.; Wolf, R. In Multiple Bonds
and Low Coordination in Phosphorus Chemistry; Regitz, M.; Schere, O.,
Eds.; Thieme: Stuutgart, 1990; pp 129-148.
(13) Veith, M.; Bertsch, B.; Huch, V. Z. Anorg. Allg. Chem. 1988, 559, 73.
(14) Mathey, F. Chem. ReV. 1990, 90, 997.
9
J. AM. CHEM. SOC. VOL. 124, NO. 11, 2002 2507

A R T I C L E S
Kato et al.
Scheme 4
Scheme 5
Figure 1. Solid-state structure of compound IIIP3. Selected bond lengths
(Å) and angles (deg): P(1)-P(2), 2.1209(12); P(1)-C(1), 1.737(3); P(2)-
C(1), 1.706(3); C(1)-Si(1), 1.872(3); P(1)-N(1), 1.664(3); P(1)-N(2),
1.661(3); P(2)-N(3), 1.671(3); P(2)-N(4), 1.669(3); P(1)-C(1)-P(2),
76.05(14); P(1)-C(1)-Si(1), 147.3(2); P(2)-C(1)-Si(1), 136.6(2); C(1)-
P(1)-P(2), 51.30(11); C(1)-P(2)-P(1), 52.65(12).
Table 1. Crystallographic Data for Compounds IIIP3 and 7
IIIP3
7
formula
C26H61Cl4GaN4Si2P2 C30H50Cl4GaN3P2Si
formula weight
759.43
754.28
cryst system, space group monoclinic, P21/c
triclinic, P-1
11.103(2)
12.865(3)
14.354(3)
93.476(3)
104.064(3)
107.433(3)
1877.8(7)
2
1.334
1.158
17042
9383
a, Å
b, Å
c, Å
9.9435(4)
21.9177(8)
18.3228(7)
R, deg
â, deg
γ, deg
V, Å3
Z
90.2780(10)
and gallium trichloride to phosphorus ylide 3 again leads to
the formation of heterocyclic salts IIIP3(AlCl4) and IIIP3-
(GaCl4), respectively, which feature spectroscopic data identical
with those of the previously isolated triflate salt (Scheme 5).
The gallium salt was characterized by a single-crystal X-ray
diffraction study (Figure 1, Table 1). Not surprisingly, the
geometric parameters observed for IIIP3 are very similar to
those previously observed for IIIP1.3 The carbon center is planar
(sum of bond angles 359.9°), the P-P (2.12 Å) and P-C (1.74
and 1.71 Å) bond lengths being slightly shorter than would be
expected for single bonds. The electronic structure of IIIP1 has
been discussed in details in the primary account of this work.3
The C-phosphino-P-chloro phosphorus ylides 4-6 were also
synthesized in good yields by adding 1 equiv of the desired
chlorophosphine to carbene 1 (Scheme 4). In the case of
3993.2(3)
4
1.263
1.119
52994
d
calcd, Mg/m3
absorp coeff, mm-1
no. total reflections
no. unique reflections
R1 (I > 2σ(I))
5716
0.0469
0.1192
0.453 and -0.604
0.0316
0.0834
0.922 and -0.643
wR2,a (all data)
(∆/G)max [e Å-3
]
2
2
2
a wR2 ) {[∑w(Fo - Fc )2]/[∑w(Fo )2]}1/2
.
C-P carbon atom is a doublet of doublets at 104.8 ppm (1JPC
) 70.6 and 72.4 Hz), lying in the range observed previously
for similar compounds.9,15 Last, in the case of the diphenylphos-
phino derivative 6, the C-phosphonio phosphaalkene IVP6 has
been isolated in 55% yield as colorless crystals, with no trace
of the isomeric three-membered ring of type IIIP6 detectable
(Scheme 5). The 31P NMR spectrum for IVP6 exhibited an AX
system at 52.0 (σ4-P) and 341.0 (σ2-P) ppm (2JPP ) 154.2 Hz),
while in the 13C NMR spectrum the carbon atom bonded to the
two phosphorus centers was observed as a doublet of doublets
at 107.7 (1JPC ) 74.8 and 49.8 Hz).
In none of the reactions described above could the formation
of the open form IIP be detected. However, when a dichlo-
romethane solution of C-phosphino-P-chloro phosphorus ylide
6 was treated at -78 °C with gallium trichloride, in the presence
of a large excess of acetonitrile, five-membered heterocycle 7
was cleanly obtained and isolated in 75% yield (Scheme 6).
This compound was fully characterized in solution and by a
single-crystal X-ray diffraction study (Figure 2, Table 1). We
t
Pr2N(Ph)P-Cl and Bu2P-Cl, the reaction requires 3 days at
room temperature and 1 week at 40 °C, respectively, while the
diphenylchlorophosphine-derived ylide 6 was readily formed
at low temperature. The di-tert-butylphosphino derivative 4
reacts at -78 °C with GaCl3 to give, once again, the corre-
sponding three-membered ring IIIP4. This compound has been
fully characterized by multinuclear NMR spectroscopy. In
contrast, addition of 1 equiv of GaCl3 to the (diisopropylamino)-
phenylphosphino derivative 5 afforded a mixture of three-
membered ring IIIP5 and C-phosphoniophosphaalkene IVP5
in a 20/80 ratio (according to 31P NMR spectroscopy). Both
compounds were characterized in solution by NMR spectros-
copy. In the 31P NMR spectrum, the three-membered ring IIIP5
displays a characteristic high-field AX-system at δ 8.5 and
-68.5 ppm (2JPP ) 254.6 Hz), while IVP5 gives the expected
low-field AX-system at 66.7 (σ4-P) and 343.3 ppm (σ2-P) (2JPP
) 162.2 Hz). In the 13C NMR spectrum, the signal for the Pd
(15) Markovskii, L. N.; Romanenko, V. D.; Ruban, A. V. Chemistry of Acyclic
Compounds of Two-Coordinate Phosphorus; Naukova Dumka: Kiev, 1988.
9
2508 J. AM. CHEM. SOC. VOL. 124, NO. 11, 2002

Diphosphorus Analogues of Amidinium Salts
A R T I C L E S
Scheme 7
Scheme 8
Figure 2. Solid-state structure of compound 7. Selected bond lengths (Å)
and angles (deg): P(1)-C(1), 1.7274(16); P(2)-C(1), 1.7046(16); C(1)-
Si(1), 1.8653(16); P(1)-N(1), 1.7102(14); P(2)-C(29), 1.8613(17); N(1)-
C(29), 1.273(2); C(29)-C(30), 1.492(2); P(1)-C(1)-P(2), 105.95(8); P(1)-
C(1)-Si(1), 131.04(9); P(2)-C(1)-Si(1) 122.56(9); P(1)-N(1)-C(29),
114.55(11); N(1)-C(29)-P(2), 113.79(12); C(29)-P(2)-C(1), 99.60(7).
Scheme 6
cleanly obtained (66% yield). Note that, as in the previous
reactions leading to 7 and 8, only one regioisomer is formed.
Discussion
As mentioned in the Introduction, the formation of IIIP2 and
IIIP3 by addition of a phosphenium salt to the carbene 1 could
have been rationalized by a concerted [2 + 1] cycloaddition
involving the multiple bond character of the carbene. However,
the formation of IIIP3 by chloride abstraction from the
C-phosphino-P-chloro phosphorus ylide 3 (Scheme 5) clearly
demonstrates that the open form of type IIP is indeed the
intermediate leading to the heterocyclic system. This is con-
firmed by the formation of the five-membered heterocycle 8
(Scheme 6), which results from a [3 + 2] cycloaddition of IIP3
with acetonitrile (Scheme 8). Note that although IIIP3 slowly
reacts at room temperature with acetonitrile to give 8, no reaction
occurred at -78 °C, which proves the involvement of IIP3 in
the low-temperature experiment, but does not exclude a possible
equilibrium between IIP3 and IIIP3, at room temperature.
To gain more insight into the electronic structure of species
IIP, ab initio calculations at the B3LYP/6-31 g* level16 with
additional zero-point vibrational energy correction were per-
formed on the model compound IIIP7 (SiH3 at carbon and NH2
at phosphorus). As predicted by the previous calculations on
the parent compounds, we found that the open planar form (C2V
symmetry) of type IIP7a, analogous to that of amidinium salts
have checked that the C-phosphoniophosphaalkene IVP6 did
not react with acetonitrile.
When the reaction of C-phosphino-P-chloro phosphorus ylide
3 with gallium trichloride, in the presence of a large excess of
acetonitrile, was monitored at -78 °C by 31P NMR spectros-
copy, a 1/1 mixture of IIIP3 and the five-membered heterocycle
8 was obtained (Scheme 6). After stirring of the reaction mixture
at room temperature for 6 h, the three-membered heterocycle
IIIP3 was totally transformed into 8. We have checked that
IIIP3 does not react with acetonitrile at -78 °C, but it appears
that it does react at room temperature, cleanly affording 8 after
6 h. Note that IIIP1 (diisopropylamino substituents at both
phosphorus) does not react with acetonitrile, even under heating
at 50 °C for 12 h; under more drastic conditions, decomposition
of IIIP1 occurred.
Evolution of nitrogen was observed when the bis(diisopro-
pylamino)phosphenium salt was added at -78 °C to a dichlo-
romethane solution of the bis(diisopropylamino)phosphino-
diazomethane 9. After workup, the heterocyclic salt 10 was
isolated in 62% yield (Scheme 7). The 31P NMR spectrum show
two singlets at 53.1 and 46.0 ppm in a 1/2 ratio, while in the
13C NMR spectrum, a triplet at 17.0 ppm (JPC ) 148.1 Hz)
suggested the presence of an ylidic carbon bonded to two
magnetically equivalent phosphorus nuclei. The PC(H)P skel-
eton was confirmed by a triplet at 1.64 ppm (JPH ) 12.5 Hz) in
(16) All quantum chemical calculations were performed at the B3LYP/6-31g*
level with the Gaussian-98 set of programs: Frisch, M. J.; Trucks, G. W.;
Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.;
Zakrzewski, V. G.; Montgomery, J. A.; Stratmann, R. E.; Burant, J. C.;
Dapprich, S.; Millam, J. M.; Daniels, A. D.; Kudin, K. N.; Strain, M. C.;
Farkas, O.; Tomasi, J.; Barone, V.; Cossi, M.; Gammi, R.; Mennucci, B.;
Pomelli, C.; Adamo, C.; Clifford, S.; Ochterski, J.; Petersson, G. A.; Ayala,
P. Y.; Cui, Q.; Morokuma, K.; Malick, D. K.; Rabuck, A. D.; Raghavachari,
K.; Foresman, J. B.; Cioslowski, J. Ortiz, J. V.; Stefanov, B. B.; Liu, G.;
Liashenko, A.; Piskorz, P.; Komaromi, I.; Gomperts, R.; Martin, R. L.;
Fox, D. J.; Keith, T.; Al-Laham, M. A.; Peng, C. Y.; Nanayakkara, A.;
Gonzalez, C.; Challacombe, M.; Gill, P. M. W.; Johnson, B. G.; Chen,
W.; Wong, M. W.; Andres, J. L.; Head-Gordon, M.; Replogle, E. S.; Pople,
J. A. Gaussian, Inc., Pittsburgh, PA, 1998.
1
the H NMR spectrum. The azine proton was apparent by the
presence of a doublet at 7.85 ppm (JPH ) 148.1 Hz), while the
corresponding carbon atom gave a broad doublet at 159.6 ppm.
When the same reaction was carried out in acetonitrile, the
formation of 10 was totally inhibited and the adduct 11 was
9
J. AM. CHEM. SOC. VOL. 124, NO. 11, 2002 2509

A R T I C L E S
Kato et al.
Table 2. Energy between Both Valence Isomers: IIPb and IIIP
C substituent
P substituents
∆E (kcal/mol)a
NH2
H
H
CH3
SiH3
SiMe3
NH2
H
NH2
NH2
NH2
NiPr2
only IIPb is stable
34.6
3.7
6.5
5.8
-6.1
a Ering - Eallyl
.
IIN, is not a minimum on the potential energy surface. This
illustrates the striking difference between the chemistry of
phosphorus and nitrogen (Scheme 1). However, pyramidalization
of one of the phosphorus atoms leads to IIP7b, which is not
only an energy minimum but also lower in energy than the cyclic
form IIIP7 by 5.8 kcal/mol.
From Scheme 5, it is clear that the evolution of the open
form of type IIP is strongly dependent on the nature of the
substituents. The calculations indicate that IIP7 prefers to
rearrange to the C-phosphoniophosphaalkene form IVP7, which
is much lower in energy than IIIP7. To understand the factors
that allow for the formation of the cyclic isomer of type IIIP,
calculations were performed with varying substitution patterns
(Table 2). The given values have been verified by the corre-
sponding vibrational analysis (at the density functional level)
as energy minima on the electronic hypersurfaces (except for
SiMe3 at carbon and NiPr2 at phosphorus, for which a vibrational
analysis is prohibited due the size of the structure). Somewhat
surprising is the almost negligible effect of the carbon substituent
on going from H to CH3 and SiH3; of course, with an amino
group at carbon, the three-membered ring is no longer a
minimum, because of stabilization of the positive charge by the
amino group, giving rise to an iminium structure. Amino
substituents at the phosphorus atoms favor the ring structure.
This is due to the σ-withdrawing effect of the amino group,
which increases the tendency for pyramidalization at phospho-
rus. As a consequence, the open structure is destabilized and
the energy difference between structures IIP and IIIP decreases;
isomers IIP stay lower in energy than IIIP, except for IIIP1
(observed experimentally). The only reasonable explanation to
rationalize the reverse order of stability of IIP and IIIP, when
replacing NH2 by the bulky NiPr2 substituents at phosphorus,
is to believe that the steric demand in the linear form is larger
than in the cyclic system (Figure 3). This is in line with the
experimental observation of cyclic derivatives IIIP2-5.
From the calculations and the experimental results, it appears
that intermediates IIP easily rearrange via 1,3-shift of a
P-substituent to the other phosphorus atom, giving IVP, except
when bulky substituents are present at both phosphorus, since
the phosphorus centers cannot accommodate a further substituent
anymore. However, in this case, the three-membered ring
structure IIIP is favored with respect to the open form IIP.
Since the carbon substituent has apparently no effect on the
relative stability of compounds IIP and IIIP, a possibility to
enable the isolation of the open form was to decrease the steric
Figure 3. Optimized geometries of IIP1 and IIIP1.
hindrance at the carbon center. The results described in Scheme
7 demonstrate the difficulty of the task, which is due to the
high reactivity of the diphosphinocarbocation IIP. Indeed, 10
obviously results from a [3 + 1] cycloaddition reaction involving
the open form IIP9 and the starting diazo precursor 9. This is
further demonstrated by the reaction in acetonitrile, which leads
to the [3 + 2] cycloadduct 11. All attempts to spectroscopically
observe IIP9 failed, but in agreement with our hypothesis, no
1,3-shift is observed, nor is the formation of the corresponding
three-membered heterocycle.
The regioselectivity of the cycloaddition reations leading to
7 and 8 can be explained by the different nature of the two
phosphorus atoms. The amino substituents stabilize the positive
charge at phosphorus, and therefore, the amino-substituted
phosphorus is the electrophilic site of the molecule and reacts
with the nitrogen end of acetonitrile. This is also true for 8, for
which the silicon atom of the four-membered ring makes the
nitrogen less of a π-donor.
Conclusion
Diaminocarbocations IIN (amidinium salts) have a planar
allylic-type structure featuring a 3-center-4p-electron system.
In contrast, the diphosphinocarbocations IIP should exist as
IIPb, in which one phosphorus is planar, while the other remains
pyramidal.
Whenever one of the phosphorus ends can accommodate a
further substituent, derivatives IIP rearrange into the thermo-
dynamically more stable phosphoniophosphaalkenes IVP. This
1,3-shift is prevented when sterically hindered substituents are
used at both phosphorus atoms, but in this case the diphosphi-
9
2510 J. AM. CHEM. SOC. VOL. 124, NO. 11, 2002

Diphosphorus Analogues of Amidinium Salts
A R T I C L E S
(s broad, CHN), 50.9 (d, JPC ) 14.8 Hz, CCH3), 58.3 (dd, JPC ) 115.5
and 92.9 Hz, PCP). Anal. Calcd for C26H61N4Si2P2Cl: C, 53.53; H,
10.54; N, 9.60. Found: C, 53.68; H, 10.46; N, 9.48.
4: 31P{1H} NMR (CDCl3) δ 40.2 and 90.1 (AX system, 2JPP ) 257.4
Hz).
nocarbocations IIP undergo a ring closure into three-membered
heterocycles IIIP featuring a carbanionic center. This is due to
the fact that the steric demand in the linear form is larger than
in the cyclic system. This type of transformation of a cationic
into an anionic center is unlikely to be unique and should be of
significant synthetic utility.
Interestingly, intermediates IIP appear to be highly reactive
1,3-dipoles, which can be efficiently trapped by acetonitrile,
leading regioselectively to the corresponding five-membered
heterocycles. Since intermolecular trapping reactions are faster
than both the 1,3-shift and the ring closure, one can conclude
that diphosphinocarbocations possess a non-negligible lifetime.
However, all our attempts to spectroscopically characterized a
compound of type IIP failed, and this remains an exciting
challenge.
5: yellow oil. 31P{1H} NMR (CDCl3) δ 50.5 and 84.2 (2JPP ) 246.3
Hz); 13C{1H} NMR (CDCl3) δ 5.9 (d, JPC ) 4.7 Hz, SiCH3), 23.7 (s,
JPC ) 6.4 Hz, CHCH3), 24.2 (d, JPC ) 7.3 Hz, CHCH3), 24.7 (d, JPC
) 3.1 Hz, CHCH3), 24.8 (d, JPC ) 2.3 Hz, CHCH3), 24.9 (s, CHCH3),
35.6 (dd, JPC ) 119.4 and 45.3 Hz, PCP), 46.3(s, CHN), 49.0 (d, JPC
) 6.8 Hz, CHN), 49.3 (d, JPC ) 5.4 Hz, CHN), 125.2 (d, JPC ) 1.7
Hz, Caro), 126.8 (d, JPC ) 3.4 Hz, Caro), 131.3 (d, JPC ) 19.5 Hz, Caro),
148.0 (tlike, JPC ) 20.0 Hz, Caro).
6: white crystals (82%); mp 65-69 °C; 31P{1H} NMR (CDCl3) δ
1
0.3 and 86.5 (2JPP ) 228.6 Hz); H NMR (CDCl3) δ -0.11 (s, 9 H,
3
3
SiCH3), 1.20 (d, JHH ) 7.0 Hz, 12 H, CHCH3), 1.44 (d, JHH ) 7.0
Hz, 12 H, CHCH3), 4.21 (sept d, 3JHH ) 7.0 Hz, 3JPH ) 14.0 Hz, 4 H,
NCH), 7.20-7.47 (m, 10 H, Haro); 13C{1H} NMR (CDCl3) δ 4.3 (s,
SiCH3), 23.8 (d, JPC ) 3.3 Hz, CHCH3), 23.9 (d, JPC ) 3.1 Hz, CHCH3),
24.5 (d, JPC ) 3.8 Hz, CHCH3), 24.6 (d, JPC ) 3.9 Hz, CHCH3), 26.3
Experimental Section
All manipulations were performed under an inert atmosphere of
argon using standard Schlenk techniques. Dry, oxygen-free solvents
were employed. 1H, 13C, 19F, 29Si, and 31P NMR spectra were recorded
2
(dd, JPC ) 134.6 and 23.4 Hz, PCP), 49.2 (d, JPC ) 5.3 Hz, CHN),
127.4 (d, JPC ) 4.0 Hz, Caro), 132.1 (d, JPC ) 19.6 Hz, Caro), 134.3 (t,
JPC ) 13.0 Hz, Caro), 143.0 (t, JPC ) 19.4 Hz, Caro). Anal. Calcd for
C28H47N2SiP2Cl: C, 62.61; H, 8.82; N, 5.21. Found: C, 62.42; H, 8.71;
N, 5.25.
1
on Bruker AC200, WM250, or AMX400 spectrometers. H, 13C, and
29Si chemical shifts are reported in ppm relative to Me4Si as external
standard. 31P NMR downfield chemical shifts are expressed with a
positive sign, in ppm, relative to an external standard of 85% H3PO4.
Synthesis of Three-Membered Heterocycles IIIP1-3, by Addition
of the Corresponding Phosphenium Salts to the Carbene 1. In a
typical experiment, a CH2Cl2 solution (2.5 mL) of 1 equiv of
phosphenium trifluoromethane sulfonate was added to a pentane
solution (5 mL) of the carbene 1 (0.3 mmol) at 0 °C. After the solution
mixture had been stirred for 30 min at room temperature, the solvent
was removed under vacuum. Derivative IIIP1 was isolated as a white
powder by adding Et2O (5 mL) to the residue and recrystallized from
a THF solution at -5 °C (66% yield). Heterocycle IIIP2 was only
characterized in solution, while IIIP3 was isolated as a yellow oil in
Synthesis of Three-Membered Heterocycles IIIP3-5 and Phos-
phoniophosphaalkene IVP5,6 by Chloride Abstraction from Ylides
3-6. In a typical experiment, a CH2Cl2 solution (3 mL) of 1 equiv of
AlCl3 or GaCl3 was added to a CH2Cl2 solution (5 mL) of ylide (0.3
mmol) at -78 °C. After the mixture had been stirred for 1 h at room
temperature, the solvent was removed under vacuum. Heterocycle IIIP3
was slowly crystallized from a CH2Cl2 solution at -30 °C, while IIIP4
was obtained as an oil. Derivatives IIIP5 and IVP5 were characterized
in the solution mixture. The phosphoniophosphaalkene IVP6 was
crystallized from a CH2Cl2/toluene solution at -20 °C.
IIIP3(GaCl4): colorless crystals (39%); mp 100 °C (dec);31P{1H}
NMR (CD2Cl2) δ 8.0 and 6.9 (1JPP ) 164.0 Hz); 29Si{1H} NMR
-
30% yield. The latter compound was fully characterized with GaCl4
2
2
as counterion (vide infra).
(CDCl3) δ -10.4 (tlike, JPSi ) 10.6 Hz CSiCH3), 6.3 (tlike, JPSi ) 2.5
IIIP1: mp 89-90 °C;31P{1H} NMR (CDCl3) δ 7.3; 29Si{1H} NMR
Hz NSiCH3); 1H NMR (CDCl3) δ 0.20 (s, 9 H, CSiCH3), 0.60 (s, 3 H,
2
1
3
(CDCl3) δ -10.7 (t, JPSi ) 10.6 Hz); H NMR (CDCl3) δ 0.22 (s, 9
H, SiCH3), 1.34 (d, 3JHH ) 6.7 Hz, 24 H, CHCH3), 1.38 (d, 3JHH ) 6.7
Hz, 24 H, CHCH3), 3.83 (sept t, 3JHH ) 6.7 Hz, 3JHP ) 4JHP ) 6.9 Hz,
NSiCH3), 0.62 (s, 3 H, NSiCH3), 1.39 (s, 18 H, CCH3), 1.41 (d, JHH
) 7.0 Hz, 12 H, CHCH3), 1.43 (d, 3JHH ) 7.0 Hz, 12 H, CHCH3), 3.71
(sept, 3JHH ) 7.0 Hz, NCH); 13C{1H} NMR (CDCl3) δ 2.5 (tlike, 3JPC
)
3
8 H, NCH); 13C{1H} NMR (CDCl3) δ 2.9 (t, JPC ) 4.1 Hz, SiCH3),
4.3 Hz, CSiCH3), 4.2 (s, NSiCH3), 5.2 (dd, JPC ) 5.0 and 7.9 Hz,
3
4
3
4
NSiCH3), 23.4 (tlike, 3JPC ) 3.4 Hz, CHCH3), 24.8 (tlike, 3JPC ) 2.6 Hz,
23.9 (tlike, JPC ) JPC ) 3.1 Hz, CHCH3), 25.1 (tlike, JPC ) JPC < 2
Hz, CHCH3), 49.3 (s, NCH), 49.6 (t, 1JPC ) 7.3 Hz, C-SiMe3), 120.6
(q, JFC ) 320.1 Hz, CF3). Anal. Calcd for C29H65N4O3F3SiP2S: C,
3
CHCH3), 32.7 (tlike, JPC ) 3.6 Hz, NCCH3), 49.6 (s, NCH), 54.1 (s,
1
1
NCCH3), 67.7 (dd, JPC ) 5.2 and 7.1 Hz, PC). Anal. Calcd for
49.98; H, 9.40; N, 8.04. Found: C, 50.17; H, 9.48; N, 8.24.
IIIP2: 31P{1H} NMR (CD2Cl2) δ 9.0 and 7.1 (1JPP ) 130 Hz).
IIIP3: vide infra.
C26H61N4Si2P2GaCl4: C, 41.12; H, 8.10; N, 7.38. Found: C, 41.33; H,
8.15; N, 7.35.
IIIP4(GaCl4): yellow oil (60%). 31P{1H} NMR (CDCl3) δ -21.5
and 10.4 (1JPP ) 136.0 Hz); 1H NMR (CDCl3) δ 0.28 (s, 9 H, CSiCH3),
1.40 (d, 3JHH ) 6.8 Hz, 12 H, CHCH3), 1.43 (d, 3JHH ) 6.8 Hz, 12 H,
CHCH3), 1.44 (s, 9 H, CCH3), 1.53 (s, 9 H, CCH3), 3.95 (sept d, 3JHH
Preparation of C-Phosphino-P-Chloro Phosphorus Ylides 3-6.
In a typical experiment, a pentane solution (2 mL) of 1 equiv of
chlorophosphine was added to a pentane solution (3 mL) of the carbene
1 (0.3 mmol) at -78 °C. The reaction was monitored by 31P NMR
spectroscopy. Ylides 3 and 6 were readily obtained after the solution
mixture was warmed to room temperature. In the case of the more
3
) 6.8 Hz, JPH ) 1.8 Hz, NCH); 13C{1H} NMR (CDCl3) δ 3.4 (dd,
3JPC ) 1.8 and 2.8 Hz, SiCH3), 23.5 (d, 3JPC ) 6.4 Hz, CHCH3), 24.9
(dd, 3JPC ) 2.8 and 4.6 Hz, CHCH3), 29.9 (tlike, 3JPC < 1.8 Hz, CCH3),
50.6 (d, 2JPC ) 5.5 Hz, NCH), 43.9 (dd, JPC ) 8.3 and 2.7 Hz, PCCH3).
IIIP5(AlCl4): 31P{1H} NMR (CDCl3) δ -68.0 and 8.5 (1JPP ) 254.5
Hz).
t
crowded chlorophosphines [(iPr2N)PhPCl and Bu2PCl], the reaction
was complete after 3 days at room temperature and 1 week at 40 °C,
respectively. After filtration, the solution mixture was concentrated and
the corresponding ylides 3, 4, and 6 were obtained by slow crystal-
lization at -20 °C, and derivative 5 was obtained as an oil.
IVP5(AlCl4): 31P{1H} NMR (CDCl3) δ 66.7 and 343.3 (1JPP ) 162.2
Hz); 13C{1H} NMR (CDCl3) δ 104.8 (dd, JPC ) 70.6 and 72.4 Hz,
PCP),
3: white crystals (52%); mp 175 °C (dec);31P{1H} NMR (CDCl3) δ
84.2 and 143.8 (2JPP ) 189.6 Hz); H NMR (CDCl3) δ 0.30 (s, 3 H,
IVP6(AlCl4): Colorless crystals (55% yield); mp 96-97 °C; 31P-
1
1
SiCH3), 0.37 (s, 9 H, SiCH3), 0.39 (s, 3 H, SiCH3), 1.18-1.45 (m, 42
H, CH3), 3.86-4.41 (m, 4 H, NCH); 13C{1H} NMR (CDCl3) δ 6.1 (d,
JPC ) 4.5 Hz, SiCH3), 6.3 (s, SiCH3), 7.6 (d, JPC ) 5.1 Hz, SiCH3),
23.2-26.5 (m, CHCH3), 32.2 (d, JPC ) 5.3 Hz, CCH3), 48.6 and 49.4
{1H} NMR (CDCl3) δ 52.0 and 341.0 (2JPP ) 152.6 Hz); H NMR
(CDCl3) δ -0.10 (s, 9 H, SiCH3), 1.11 (d, 12 H, JHH ) 6.8 Hz, CH3),
1.38 (d, 12 H, JHH ) 6.7 Hz, CH3), 3.47 (d sept, 2 H, JHH ) 6.8 Hz,
JPH ) 15.4 Hz, NCH), 4.38 (m, 2 H, NCH), 7.70-8.13 (m, 10 H, Haro);
9
J. AM. CHEM. SOC. VOL. 124, NO. 11, 2002 2511

A R T I C L E S
Kato et al.
3
13C{1H} NMR (CDCl3) δ 3.4 (s, SiCH3), 23.5 (dd, JPC ) 3.3 and 1.9
Hz, CHCH3), 24.9 (m, CHCH3), 51.1 (dd, JPC ) 1.9 and 3.6 Hz, CHN),
53.5 (m, CHN), 102.7 (dd, JPC ) 49.8 and 74.8 Hz, PCP), 126.5 (dd,
JPC ) 105.4 and 3.8 Hz, Ci), 129.7 (d, JPC ) 11.1 Hz, Co), 133.0 (s
broad, Cm), 134.5 (s, Cp). Anal. Calcd for C28H47N2SiP2AlCl4: C, 50.15;
H, 7.06; N, 4.18. Found: C, 50.20; H, 7.14; N, 4.24.
Hz, 24 H, CHCH3), 1.36 (d, JHH ) 7.0 Hz, 24 H, CHCH3), 1.64 (t,
2JPH ) 12.5 Hz, 1 H, PCHP), 3.33 (sept d, 3JHH ) 7.0 Hz, 3JPH ) 14.0
3
2
Hz, 8 H, NCH), 3.98 (sept, JHH ) 6.6 Hz, 4 H, NCH), 7.85 (d, JPH
) 29.6 Hz, 1 H, NdCH); 13C{1H} NMR (CDCl3) δ 17.0 (t, JPC
)
148.1 Hz, PCP), 23.4-25.6 (m, CHCH3), 48.0 (s br, CHN), 49.5 (s,
CHN), 120.6 (q, JFC ) 320.1 Hz, CF3), 159.8 (s br, CdN).
Five-Membered Heterocycle 7. To a CH2Cl2 solution (2 mL) of
ylide 6 (0.11 g, 0.21 mmol) was added a CH3CN solution of GaCl3
(0.04 g, 0.23 mmol) at -78 °C. After the solution was warmed slowly
to room temperature, the solvent was removed under vacuum, and the
residue was washed with ether. Derivative 7 was recrystallized from a
CH2Cl2/ether solution at -20 °C. (0.12 g, 75%): mp 77-78 °C; 31P-
{1H} NMR (CDCl3) δ 40.1 and 87.9 (2JPP ) 124.4 Hz); 1H NMR
(CDCl3) δ 0.06 (s, 9 H, SiCH3), 1.34 (d, 3JHH ) 7.1 Hz, 12 H, CHCH3),
Five-Membered heterocycle 11. To a CH2Cl2 solution (5 mL) of
bis(diisopropylamino)phosphinodiazomethane 9 (0.13 g, 0.48 mmol)
was added an acetonitrile solution (1 mL) of solution of bis-
(diisopropylamino)phosphenium salt (0.18 g, 0.48 mmol) at 0 °C. After
the solution was warmed slowly to room temperature, the solvent was
removed under vacuum, and the residue was washed with ether.
Derivative 11 was recrystallized from a CH2Cl2/toluene solution at -30
°C (0.21 g, 66%): mp 313 °C (dec); 31P{1H} NMR (CDCl3) δ 60.0
3
1
3
and 66.2 (2JPP ) 196.5 Hz); H NMR (CDCl3) δ 1.26 (d, JHH ) 7.0
1.38 (d, JHH ) 7.1 Hz, 12 H, CHCH3), 2.60 (dd, JPH ) 7.1 and 2.1
Hz, 3 H, NdCCH3), 4.15 (sept d, 3JHH ) 7.1 Hz, 3JPH ) 13.9 Hz, 4 H,
NCH), 7.60-7.80 (m, 10 H, Haro); 13C{1H} NMR (CDCl3) δ 1.0 (s,
3
Hz, 12 H, CHCH3), 1.30 (d, JHH ) 7.0 Hz, 12 H, CHCH3), 1.35 (d,
3JHH ) 7.0 Hz, 12 H, CHCH3), 1.40 (d, 3JHH ) 7.0 Hz, 12 H, CHCH3),
3
2
SiCH3), 2.3 (d, JPC ) 3.4 Hz, NdCCH3), 24.3 (d, JPC ) 3.0 Hz,
1.78 (t, JPH ) 8.9 Hz, 1 H, PCHP), 2.63 (dd, JPH ) 5.5 and 1.1 Hz,
CHCH3), 24.7 (d, JPC ) 3.0 Hz, CHCH3), 48.9 (d, 2JPC ) 5.7 Hz, CHN),
122.9 (dd, JPC ) 79.3 and 8.1 Hz, Ci), 130.3 (d, JPC ) 12.0 Hz, Co),
133.0 (d, JPC ) 10.9 Hz, Cm), 134.9 (d, JPC ) 3.3 Hz, Cp), 181.0 (d,
JPC ) 33.5 Hz, CdN), PCP carbon was not observed.
3
3
3 H, NdCCH3), 3.81 (sept d, JHH ) 7.0 Hz, JPH ) 14.0 Hz, 4 H,
3
3
NCH), 3.92 (sept d, JHH ) 7.0 Hz, JPH ) 14.0 Hz, 4 H, NCH); 13C-
{1H} NMR (CDCl3) δ 1.0 (t, JPC ) 2.7 Hz, NdCCH3), 13.4 (dd, JPC
) 151.5 and 156.6 Hz, PCP), 23.1 (d, JPC ) 3.6 Hz, CHCH3), 24.0 (d,
JPC ) 3.9 Hz, CHCH3), 24.3 (s, CHCH3), 25.1 (d, JPC ) 2.5 Hz,
CHCH3), 47.8 (d, JPC ) 6.1 Hz, CHN), 48.4 (d, JPC ) 6.1 Hz, CHN),
120.6 (q, JFC ) 320.1 Hz, CF3), 186.6 (d, JPC ) 69.1 Hz, CdN).
X-ray Crystallographic Studies of Compounds IIIP3 and 7.
Crystal data for both structures are presented in Table 1. Data were
collected at low temperatures on a Bruker-AXS CCD 1000 diffracto-
meter with Mo Ka (λ ) 0.71073 Å). The structures were solved by
direct methods by means of SHELXS-9717 and refined with all data
on F2 by means of SHELXL-97.18 All non-hydrogen atoms were refined
anisotropically. The hydrogen atoms of the molecules were geo-
metrically idealized and refined using a riding model. A disorder of
three chlorine atoms of the GaCl4 anion in IIIP3 was refined on two
positions with the help of 92 ADP and distances restraints.
Five-Membered Heterocycle 8. To a CH2Cl2 solution (2 mL) of
ylide 3 (0.16 g, 0.27 mmol) was added an acetonitrile solution of GaCl3
(0.05 g, 0.27 mmol) at -78 °C. The cold bath was removed and the
solution mixture was stirred at room temperature for 6 h. Then, the
solvent was removed under vacuum, and the residue was washed with
ether. Derivative 8 was recrystallized from a CH2Cl2/ether solution at
-20 °C (0.05 g, 25%): mp 192 °C (dec); 31P{1H} NMR (CDCl3) δ
1
50.7 and 79.3 (2JPP ) 129.0 Hz); H NMR (CDCl3) δ 0.04 (s, 9 H,
SiCH3), 0.71 (s, 3 H, NSiCH3), 0.83 (s, 3 H, NSiCH3), 1.30 (s, 18 H,
3
3
NCCH3), 1.36 (d, JHH ) 7.1 Hz, 12 H, CHCH3), 1.40 (d, JHH ) 7.1
Hz, 12 H, CHCH3), 2.57 (dd, JPH ) 7.1 and 2.0 Hz, 3 H, NdCCH3),
3.93 (sept d, JHH ) 7.1 Hz, JPH ) 10.7 Hz, 4 H, NCH); 13C{1H}
NMR (CDCl3) δ 3.3 (t, JPC ) 4.3 Hz, CSiCH3), 4.6 (s, NSiCH3), 5.1
(m, NSiCH3), 20.7 (t, JPC ) 29.4 Hz, NdCCH3), 24.8 (d, JPC ) 3.7
Hz, CHCH3), 25.0 (d, JPC ) 5.5 Hz, CHCH3), 32.4 (d, JPC ) 2.6 Hz,
CCH3), 49.0 (d, 2JPC ) 6.4 Hz, CHN), 53.3 (s, NCCH3), 189.0 (dd, JPC
) 48.7 and 1.8 Hz, CdN), PCP carbon was not observed.
3
3
Acknowledgment. Thanks are due to the French Embassy
in Tokyo for a grant to (T.K.), the CNRS, the Deutsche
Forschungsgmeinschaft, and UCR for financial support of this
work.
Four-Membered Heterocycle 10. To a CH2Cl2 solution (5 mL) of
bis(diisopropylamino)phosphinodiazomethane 9 (0.14 g, 0.48 mmol)
was added a dichloromethane solution (1 mL) of bis(diisopropylamino)-
phosphenium salt (0.09 g, 0.24 mmol) at 0 °C. After the solution was
warmed slowly to room temperature, the solvent was removed under
vacuum, and the residue was washed with ether. Heterocycle 10 was
recrystallized from a CH2Cl2/toluene solution at -30 °C (0.11 g,
62%): mp 118-120 °C; 31P{1H} NMR (CDCl3) δ 46.0 (s, 2 P) and
Supporting Information Available: X-ray crystallographic
data for compounds IIIP3 and 7 (print/PDF). This material is
available free of charge via the Internet at http/::pubs.acs.org.
JA010347H
(17) Sheldrick, G. M. Acta Crystallogr. Sect. A 1990, 46, 467.
(18) Sheldrick, G. M., SHELXL-97, Program for Crystal Structure Refinement;
Universitat Gottingen, 1997.
3
53.1 (s, 1 P); 1H NMR (CDCl3) δ 1.09 (d, JHH ) 6.6 Hz, 12 H,
3
3
CHCH3), 1.18 (d, JHH ) 6.6 Hz, 12 H, CHCH3), 1.34 (d, JHH ) 7.0
9
2512 J. AM. CHEM. SOC. VOL. 124, NO. 11, 2002