A rare example of a rearrangement involving four structural isomers: α-Phosphinonitrile/c-phosphinoketenimine/ 1-Aza-4-phosphabutadiene/1,2-dihydro-1,2-azaphosphete

Article abstract of DOI:10.1002/1521-3765(20021202)8:23<5305::AID-CHEM5305>3.0.CO;2-6

The stable compound [bis(dicyclohexylamino)phosphino](trimethylsilyl)carbene (1) reacts with dimethyl cyanamide to afford the original 1,2-dihydro-1,2- azaphosphete 4a (51% yield). The surprising formation of this heterocycle involves the transient format

Full text of DOI:10.1002/1521-3765(20021202)8:23<5305::AID-CHEM5305>3.0.CO;2-6

G. Bertrand, A. Baceiredo et al.
Chem. Eur. J. 2002, 8, No. 23
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5305

FULL PAPER
A Rare Example of a Rearrangement Involving Four Structural Isomers:
a-Phosphinonitrile/C-Phosphinoketenimine/1-Aza-4-phosphabutadiene/
1,2-Dihydro-1,2-azaphosphete
De¬borah Amsallem,[b] Ste¬phane Mazie¡res,[b] Vale¬rie Piquet-Faure¬,[b] Heinz Gornitzka,[b]
Antoine Baceiredo,*[b] and Guy Bertrand*[a]
Abstract: The stable compound [bis(dicyclohexylamino)phosphino](trimethylsilyl)-
carbene (1) reacts with dimethyl cyanamide to afford the original 1,2-dihydro-1,2-
azaphosphete 4a (51% yield). The surprising formation of this heterocycle involves
the transient formation of a nitrile, a keteneimine, and a 1-aza-4l3-phosphabutadiene
derivative. By using substituent effects and different synthetic routes, all of these
structural isomers have been isolated.
Keywords: cumulenes ¥ heterocyc-
les ¥ phosphorus ¥ rearrangements
of interest to investigate the scope and limitation of such a
route for the synthesis of azirines. Here we report a detailed
study of the reaction of 1 with dimethyl cyanamide, which
surprisingly cleanly affords the 1,2-dihydro-1,2l3-azaphos-
phete 4a instead of the expected azirine (Scheme 1). Note
that although the chemistry of 1,2-dihydro-1,2-diphosphetes is
well developed,[4] only a few examples of dihydroazaphos-
phetes have been reported.[5] Of particular interest, rear-
rangements involving four different structural isomers of
dihydroazaphosphetes are described.
Introduction
Advances in synthetic methodology continue to afford access
to new classes of small heterocycles, which in turn opens the
route to structure and reactivity studies of these often-unusual
compounds. In the course of our study concerning the
reactivity of stable (phosphino)(silyl)carbenes,[1] we have
shown that the carbene 1 undergoes a [1‡2] cycloaddition
reaction with benzonitrile giving rise to the corresponding
2-phosphino-2H-azirine 2, which can be isomerized to the 1,2-
l5-azaphosphete 3 (Scheme 1).[2, 3] Since the cycloaddition of
transient carbenes with nitriles has never been described, it is
Results and Discussion
Synthesis of the 1,2-dihydro-1,2l3-azaphosphete 4a: [Bis(di-
cyclohexylamino)phosphino](trimethylsilyl)carbene
(1)[6]
À ꢀ
readily reacts with Me2N C N at room temperature to give
the original four-membered heterocycle 4a, which was
isolated in 51% yield (Scheme 1). The 31P NMR spectrum
(proton coupled) shows a broad triplet at d ˆ 58.7 ppm
(3J(P,H) ˆ 14.6 Hz) consistent with the presence of only one
cyclohexylamino (c-Hex2N) group directly bonded to the
phosphorus atom. Indeed, in the 13C NMR spectrum two
CHN groups appear as two doublets with rather large
phosphorus carbon coupling constants[7] at d ˆ 54.1
(2J(P,C) ˆ 16.5 Hz) and 54.0 ppm (2J(P,C) ˆ 12.5 Hz), which
supports the presence of a chiral l3-phosphorus center, while
the two other CHN groups appear as a singlet at d ˆ 58.0 ppm
confirming the migration of a dicyclohexylamino group from
phosphorus to a carbon atom. The unsaturated nature of 4a
was deduced from the signals at d ˆ 124.0 (1J(P,C) ˆ 0 Hz) and
146.0 ppm (2J(P,C) ˆ 19.0 Hz) in the 13C NMR spectrum. The
Scheme 1.
[a] Prof. G. Bertrand
UCR-CNRS Joint Research Chemistry Laboratory, UMR 2282
Department of Chemistry
University of California, Riverside, CA 92521-0403 (USA)
Fax : (‡1)909-787-2725
E-mail: gbertran@mail.ucr.edu
¡
[b] Dr. A. Baceiredo, Dr. D. Amsallem, Dr. S. Mazieres,
¬
Dr. V. Piquet-Faure, Dr. H. Gornitzka
¬ ¬
¬
Laboratoire Heterochimie Fondamentale et Appliquee, UMR 5069,
¬
Universite Paul Sabatier
118 Route de Narbonne, 31062 Toulouse Cedex 04 (France)
5306
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Chem. Eur. J. 2002, 8, No. 23

Rearrangements
5305 5311
structure of 4a was unequivocally established by a single-
crystal X-ray diffraction analysis (Table 1). The solid-state
structure of the molecule is illustrated in Figure 1. The four-
membered ring is planar (maximum deviation 6 pm), and both
phosphorus and nitrogen atoms are strongly pyramidalized
(sum of the angles: 291.948 and 329.468, respectively). The
bene carbon atom to the nitrogen end of the cyanamide, 2) a
dicyclohexylamino shifts from the phosphorus atom to the
À
carbene carbon atom, and 3) the Me2N C fragment inserts
into the phosphorus-carbon bond of 1. Scheme 2 summarizes
our working hypothesis, which was based on recent observa-
tions. We have shown that Lewis bases such as phosphines
react with 1 to give the corresponding phosphorus ylide
À
À
À
À
P1 N1 (1.81 ä), P1 C2 (1.82 ä), C1 N1 (1.45 ä), and C1 C2
(1.35 ä) bond lengths are con-
sistent with three single and one
double bond, respectively.
Evidently, a multistep mech-
anism has to be postulated for
the formation of 4a. Indeed,
from the starting reagents to
the formation of 4a 1) the silyl
group migrates from the car-
Scheme 2.
(Scheme 3);[8] therefore the first step might be the transient
formation of the nitrogen ylide 5a, which would easily
rearrange by a Stevens rearrangement[9] into the a-phosphi-
nonitrile 6a. Then a 1,3-silyl migration would lead to the
Table 1. Crystallographic data for compounds 4a and 9a.
4a
9a
formula
Mr
C31H59N4PSi
546.88
C28H51N4PS
506.76
crystal system
space group
a [ä]
b [ä]
c [ä]
triclinic
P1
orthorhombic
Pbca
10.470(1)
19.106(3)
29.001(3)
90
5801.40(12)
2224
8
≈
9.625 (1)
11.270 (1)
16.127(2)
103.650(10)
1628.4(3)
604
b [8]
V [ä3]
F(000)
Z
2
1calcd [gcmÀ3
T [K]
]
1.115
173
1.160
193
m (MoKa) [mmÀ1
2q range [8]
data collected
unique data
R(int)
parameters
goodness-of-fit
R1
]
0.146
3.78 47.06
18996
4571
0.0536
339328
0.884
0.0312
0.0663
0.169/ À 0.180
0.190
4.48 46.52
47089
3991
0.0715
Scheme 3.
keteneimine 7a, which could rearrange into the 1-aza-4-
phosphabutadiene 8a. Lastly an electrocyclic ring closure
would give the isolated 1,2-dihydro-1,2l3-azaphosphete 4a.
Indeed, carbene 1 reacts with tert-butyl isonitrile to give the
corresponding stable keteneimine 7b,[10] whereas with the
pentafluorophenyl isonitrile the 1,2-dihydro-1,2-azaphos-
phete 4c was obtained[11] (Scheme 3). Therefore, it is reason-
able to postulate that the formation of 4a and 4c involves the
rearrangement of the initially formed keteimine 7a and 7c.
Lastly, in the related diphosphete system, the existence of an
equilibrium between the 1,4-diphosphadiene and the 1,2-
dihydro-1,2-diphosphete has been demonstrated.[12]
1.009
0.0439
0.1165
0.568/ À 0.204
wR2
(D/1) max/min [eäÀ3
]
Hydrolysis of the 1,2-dihydro-1,2s3-azaphosphete 4a: Com-
pound 4a is extremely moisture sensitive and its hydrolysis in
toluene at room temperature, in the presence of Bu4NF,
resulted in the formation of the a-phosphinonitrile 6'a, which
has been isolated after addition of an excess of elemental
sulfur as the corresponding thioxophosphoranyl derivative 9a
in 55% yield (Scheme 4). The 31P NMR spectrum (proton
coupled) for 9a shows a doublet of quintuplets at d ˆ
Figure 1. Thermal ellipsoid diagram (30% probability) of 4a showing the
atom numbering scheme. Pertinent bond lengths (ä) and bond angles (deg)
2
64.8 ppm (3J(P,H) ˆ 17.2 Hz, J(P,H) ˆ 16.1 Hz) in agreement
À
À
À
are as follows: P1 C2 1.8183(17), P1 N1 1.8096(14), P1 N3 1.6742(15),
with the presence of two dicyclohexylamino groups directly
bonded to the phosphorus atom. The 13C NMR spectrum
revealed a doublet for both the PCH group (d ˆ 63.7 ppm,
À
À
À
À
C1 C2 1.347(2), C1 N1 1.452(2), N1 Si1 1.7610(14), C1 N4 1.393(2),
À
C2 N2 1.423(2), N1-P1-N3 109.37(7), N1-P1-C2 74.69(7), N3-P1-C2
107.88(8), C1-N1-Si1 123.65(11), C1-N1-P1 88.85(9), Si1-N1-P1 116.96(8).
Chem. Eur. J. 2002, 8, No. 23
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5307

G. Bertrand, A. Baceiredo et al.
FULL PAPER
attack (C- or N-alkylation), despite the fact that they exist as
N-lithio, rather than C-lithio derivatives, both in solution and
in the solid state.[15] Consequently, the silylation of a-
phosphinonitriles 6 should give in a first step either the
corresponding a-silylated nitriles or the isomeric a N-silylke-
teneimines 7, which according to our hypothesis could
ultimately rearrange into the dihydroazaphosphetes 4.
The lithium salts of 6'a,b and 6c,d have been prepared by
using one equivalent of nBuLi or LDA in THF at À788C, and
were first silylated by addition of trimethylsilyl chloride
(Scheme 5). In the case of the non-C-substituted a-phosphi-
nonitrile 6c, the new phosphinonitrile 6e was isolated in 92%
Scheme 4.
1J(P,C) ˆ 115.3 Hz) and the nitrile carbon (d ˆ 113.1 ppm,
2
ꢀ
J(P,C) ˆ 11.3 Hz). The presence of the C N group was
confirmed by an IR absorption at nÄ ˆ 2210 cmÀ1. The forma-
tion of 6'a was so unexpected, that we confirmed its structure
by an X-ray diffraction study of 9a (Table 1, Figure 2).
Scheme 5.
yield. The presence of the nitrile group was confirm by IR
absorption n(CN) ˆ 2210 cmÀ1 and by the 13C NMR signal for
CN (d ˆ 121 ppm). The silylation of the lithium salt of C-
methylated a-phosphinonitrile 6d led to the formation of N-
trimethylsilyl ketene imine 7d. The structure of 7d was
unambiguously established by the two characteristic 13C NMR
resonances at d ˆ 185.2 (J(PC) ˆ 9.4 Hz) and 38.6 ppm
(J(PC) ˆ 8.8 Hz) for the a and b carbons of keteneimines,[16]
and the n(CCN) absorption located at 2028 cmÀ1 in the IR
spectrum.[17] Finally, in the case of the C-dimethylamino-
substituted phosphinonitriles 6'a,b, the dihydroazaphosphetes
4a,b were cleanly obtained. The structure of 4a was con-
firmed by comparison with an authentic sample, and the data
for 4b compared well with those for 4a.
These results leave no doubt on the possible rearrangement
of N-silylketeneimines of type 7 into dihydroazaphosphetes 4.
To demonstrate the possible involvement of 1-aza-4-phos-
phabutadienes of type 8 in the rearrangement of keteneimines
7 into heterocycles 4, we performed triisopropyl silylation
reactions of the lithium salts of 6'b and 6c,d (Scheme 6).
Indeed, it has been shown that bulky substituents prevent the
ring closure of the related 1,4-diphosphabutadiene into 1,2-
dihydrodiphosphete.[18] With 6c and 6d ketenimines 7'c and
Figure 2. Thermal ellipsoid diagram (30% probability) of 9a showing the
atom numbering scheme. Pertinent bond lengths (ä) and bond angles (deg)
À
À
À
À
are as follows: P1 C25 1.865(3), P1 S1 1.9399(9), P1 N1 1.662(2), P1 N3
1.670(2), N1-P1-N2 112.58(11), N1-P1-C25 104.18(11), N2-P1-C25
102.31(11), N1-P1-S1 114.38(8), N2-P1-S1 112.32(8), C25-P1-S1 110.01(9).
Derivative 6'a is analogous to the postulated intermediate
6a in the formation of the 1,2-dihydro-1,2-azaphosphete 4a
(Scheme 2), the silyl group being replaced by a proton.
Therefore, its formation probably involves the reverse steps of
the formation of the four-membered ring 4a. The initial
À
cleavage of the N Si bond would destabilize the correspond-
ing azaphosphete 4'a as well as the open form, the 1-aza-4-
phosphabutadiene 8'a, which would rearrange into a transient
keteneimime 7'a by a 1,3-migration of a dicyclohexylamino
group from C to P;[13] lastly a 1,3-hydrogen shift would give the
isolated a-phosphinonitrile 6'a (Scheme 4).
Metalation silylation of a-phosphinonitriles 6'a, 6'b, 6c, and
6d: These results as a whole seem to indicate that the a-
phosphinonitriles 6a and 6'a are in equilibrium with the
corresponding dihydroazaphosphetes 4a and 4'a via the
keteneimines 7a and 7'a and the azaphosphabutadienes 8a
and 8'a. To confirm this hypothesis, the sequential metal-
ation silylation of a-phosphinonitriles 6'a,b and 6c,d was
performed. Indeed, there are many examples in the literature
that demonstrate the ambident character of carbanions a to
nitriles;[14] this offers two potential sites for electrophilic
Scheme 6.
5308
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Chem. Eur. J. 2002, 8, No. 23

Rearrangements
5305 5311
a-Phosphinonitrile 6a via hydrolysis of 4a: A solution of azaphosphete 4a
(0.22 g, 0.39mmol) in toluene (3 mL) was treated at room temperature
with Bu4NF (1 equiv, 3.9 mL of a 1m solution in THF). After the solution
mixture was stirred at room temperature for 1 h, 31P NMR spectroscopy
indicated the quantitative formation of the a-phosphinonitrile 6a, which
7'd were isolated in 91% and 69% yield, respectively.
However, in the case of the lithium salt of the C-dimethyl-
amino-substituted a-phosphinonitrile 6'b, the formation of
the desired 1-aza-4-phosphabutadiene 8b was observed. The
31P {1H}NMR spectrum for 8b a singlet at d ˆ 111.7 ppm, in
the region expected for this type of s2-phosphorus atom,[19]
was observed. In the 13C NMR spectrum, the signals for the
dicoordinate carbon atoms appeared as doublets at d ˆ 180.5
was characterized in solution. 31P{1H} NMR (CDCl3): d ˆ 55.9ppm;
2
1H NMR (CDCl3): d ˆ 3.95 (d, J(P,H) ˆ 6.2 Hz, 1H; CH P), 2.74 (m,
À
4H; CHN), 2.33 (s, 6H; CH3N), 1.27 0.98 (m, 40H; CH2); 13C{1H} NMR
2
2
(CDCl3): d ˆ 116.6 (d, JP, C ˆ 27.0 Hz, CN), 57.9(d, JP, C ˆ 10.0 Hz, CHN),
57.5 (d, 2JP, C ˆ 15.0 Hz, CHN), 57.2 (s, CH P), 43.2 (d, JP, C ˆ 7.4 Hz, CH3N),
3
À
1
2
35.1, 34.7, 27.0, 26.8, 25.7, 25.6 ppm (s, CH2); IR (toluene): nÄ ˆ 2210 cmÀ1
ˆ
[ J(P,C) ˆ 97.5 Hz (P C)] and 152.7 ppm [ J(P,C) ˆ 34.1 Hz
ˆ
(CN).
(N C)].
a-Thioxophosphoranylnitrile (9a): Treatment of a solution of nitrile 6a
(0.19g, 0.4 mmol) in toluene (5 mL) with an excess of elemental sulfur led
after 24 h at 808C to the corresponding thioxophosphoranyl derivative 9a.
After the solvent was removed under vacuum, the residue extracted with
hexane, and after filtration, compound 9a was crystallized from a solution
in Et2O at À208C as colorless crystals (0.11 g; 55%). M.p. 213 2158C;
Conclusion
These results, as a whole, suggest the existence of reversible
rearrangements between four structural isomers, namely a-
phosphinonitriles 6, C-phosphino ketenimines 7, 1-aza-4l3-
phosphabutadienes 8, and 1,2-dihydro-1,2-azaphosphetse 4.
Smaller substituents favored the nitrile form 6 over the
ketenimine isomer 7, which has already been demonstrated.[14]
Similarly, smaller substituents favor the formation of the 1,2-
dihydro-1,2-azaphosphete 4 over the 1-aza-4l3-phosphabuta-
diene 8, which is reminiscent of the already reported 1,2-
dihydro-1,2diphosphete/1l3,4l3-diphosphabutadiene system.
More difficult to rationalize are the factors governing the
1,3-amino group migration from P to C, which allows the
formation of the butadiene system 8 from the ketenimine 7
and vice-versa. Our observations seem to indicate that the
keteneimines rearrange into 8 when a p- or s-donor at C
(NMe2 or SiMe3) and a p-electron-withdrawing group at N are
present (SiR3 or C6F5), in other words in the case of push pull
substituted keteneimines.
31P{1H} NMR (CDCl3): d ˆ 64.8 ppm; 1H NMR (CDCl3): d ˆ 4.01 (d, 2JP, H
ˆ
À
19.3Hz, 1H; CH P), 3.39(m, 4H; CHN), 2.56 (s, 6H; CH 3N), 1.33
2
1.12 ppm (m, 40H; CH2); 13C{1H} NMR (CDCl3): d ˆ 113.1 (d, JP, C
ˆ
1
11.3 Hz, CN), 63.7 (d, JP, C ˆ 115.3 Hz, CH-P), 58.9(d, 2JP, C ˆ 2.7 Hz,
2
3
CHN), 57.9(d, JP, C ˆ 1.9Hz, CHN), 44.0 (d, JP, C ˆ 6.6 Hz, CH3N), 35.2,
34.5, 34.3, 34.0, 27.5, 27.4, 27.2, 25.7, 25.5 ppm (s, CH2); MS (EI): m/z: 506
[M ]; elemental analysis calcd (%) for C28H51N4PS: C 66.36, H 10.14, N
‡
11.05; found: C 66.41, H 10.20, N 11.06.
Synthesis of a-phosphinonitrile 6'b from an iminium salt: A solution of the
[bis(diisopropylamino)phosphanyl] (dimethylamino)carbenium salt[20]
(5.67 g, 13.4 mmol) in THF (50 mL) was added to a solution of KCN
(16.9mmol) and [18]crown-6 (4.5 g, 17.0 mmol) in THF (15 mL). After the
solution mixture was stirred a room temperature for 18 h, the solvent was
removed under vacuum, and the residue was extracted with diethyl ether
(20 mL). Compound 6'b was crystallized from a solution in Et2O at À208C
as white crystals (2.58 g, 61%). M.p. 94 958C; 31P{1H} NMR (CDCl3): d ˆ
2
48.9ppm; 1H NMR (CDCl3): d ˆ 4.04 (d, JP, H ˆ 5.7 Hz, 1H; CH P), 3.36
À
3
3
(sept d, JH,H ˆ 6.6 Hz, JP, H ˆ 1.4 Hz, 4H; CHN), 2.37 (s, 6H; CH3N), 1.23
(d, 3JH,H ˆ 6.6 Hz, 6H; CH3CH), 1.22 (d, 3JH,H ˆ 6.6 Hz, 6H; CH3CH), 1.20
(d, 3JH,H ˆ 6.6 Hz, 6H; CH3CH), 1.13 ppm (d, 3JH,H ˆ 6.6 Hz, 6H; CH3CH);
13C{1H} NMR (CDCl3): d ˆ 117.0 (d, JP, C ˆ 26.8 Hz, CN), 56.8 (s, CH P),
2
À
47.5 (d, 2JP, C ˆ 11.2 Hz, CHN), 47.4 (d, 2JP, C ˆ 11.2 Hz, CHN), 43.4 (d, 3JP, C
ˆ
Work is in progress to study the possible peculiar reactivity
of a variety of push pull ketenimines.
7.7 Hz, CH3N), 24.5 (d, 2JP,C ˆ 5.3 Hz, CH3C), 24.3 (d, 2JP, C ˆ 7.7 Hz, CH3C),
23.9ppm (d, JP, C ˆ 6.9Hz, CH3C); IR (pentane): nÄ ˆ 2212 cmÀ1 (CN); MS
2
‡
(EI): m/z: 314 [M ]; elemental analysis calcd (%) for C16H35N4P: C 61.11, H
11.22, N 17.82; found: C 61.02, H 11.16, N 17.78.
a-Phosphinonitrile 6c from a chlorophosphine: A solution of bis(diiso-
propylamino)chlorophosphine (2.6 g, 9.7 mmol), ClCH2CN (0.75 g,
10 mmol), and zinc powder (0.69g, 10.7 mmol) in THF (15 mL) was
sonicated at room temperature for 6 h. After the reaction was completed
(the evolution of the reaction was monitored by 31P NMR spectroscopy),
the solvent was removed under vacuum, and the residue was extracted with
Et2O (20 mL). From the concentrated Et2O solution, compound 6c
crystallized at À208C as white crystals (1.75 g, 66%). M.p. 78 798C;
Experimental Section
General remarks: All manipulations were performed under an inert
atmosphere of argon by using standard Schlenk techniques. Dry, oxygen-
free solvents were employed. 1H, 13C, 31P, and 29Si NMR spectra were
recorded on Brucker AC80, AC200, WM250, or AMX400 spectrometers.
1H, 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 external 85% H3PO4. Infrared spectra
were recorded on a Perkin Elmer FT-IR Spectrometer 1725X. Mass
spectra were obtained on a Ribermag R10 10E instrument.
1
31P{1H} NMR (CDCl3): d ˆ 44.0 ppm; H NMR (CDCl3): d ˆ 3.40 (sept d,
2
3JH,H ˆ 6.7 Hz, 3JP, H ˆ 4.9Hz, 4H; CHN), 2.60 (d, JP, H ˆ 8.7 Hz, 2H; PCH2),
3
3
1.20 (d, JH,H ˆ 6.7 Hz, 12H; CH3CH), 1.16 ppm (d, JH,H ˆ 6.7 Hz, 12H;
CH3CH); 13C{1H} NMR (CDCl3): d ˆ 118.8 (d, 2JP, C ˆ 14.1 Hz, CN), 46.9(d,
2JP, C ˆ 11.7 Hz, CHN), 24.1 (d, JP, C ˆ 8.1 Hz, CH3C), 23.9(d, JP, C ˆ 6.5 Hz,
2
2
1,3-Bis(dicyclohexylamino)-4-dimethylamino-2-trimethylsilyl-1,2-dihydro-
1,2-azaphosphete (4a) from carbene 1: Dimethylcyanamide (2 equiv,
1.56 mL, 19.44 mmol) was added to solution of 1 (4.63 g, 9.72 mmol) in
toluene (30 mL) at room temperature. The solvent was removed under
vacuum, and the residue was extracted with pentane. After filtration,
derivative 4a slowly crystallizes at À208C as colorless crystals (2.71 g,
51%). M.p. 129 130 8C; 31P{1H} NMR (CDCl3): d ˆ 58.7 ppm; 1H NMR
(CDCl3): d ˆ 3.15 (m, 4H; CHN), 2.50 (s, 6H; CH3N), 1.96 1.01 (m, 40H;
CH3C), 16.9ppm (d, JP, C ˆ 23.3 Hz, PCH2); IR (pentane): nÄ ˆ 2236 cmÀ1
1
(CN); elemental analysis calcd (%) for C14H30N3P: C 61.96, H 11.14, N
15.48; found: C 61.89, H 11.07, N 15.52.
Phosphinonitrile 6d by methylation of 6c: nBuLi in hexanes (1 equiv) was
added to a solution of 6c (0.25 g, 0.9mmol) in THF (10 mL) at À788C.
After warming up to 08C, the solution mixture was stirred at this
temperature for 45 min. The mixture was then cooled again to À788C,
and CH3I (1 equiv, 0.13 g, 0.9mmol) was added. After the solution was
allowed to warm to room temperature, the solvent was removed under
vacuum, and the residue was extracted with pentane (20 mL). Compound
6d crystallized at À208C from the concentrated pentane solution as white
crystals (0.216 g, 82%). M.p. 88 98C; 31P{1H} NMR (CDCl3): d ˆ
CH2), 0.13 ppm (s, 9H; CH3Si); 13C{1H} NMR (CDCl3): d ˆ 146.0 (d, JPC
ˆ
ˆ
À ˆ
À ˆ
À ˆ
19.0 Hz; P C C), 124.0 (s; P C C ), 58.0 (s; CHN C ), 54.1 (d, JPC
À
À
16.5 Hz; CHN P), 54.0 (d, JPC ˆ 12.5 Hz; CHN P), 46.0 (d, JPC ˆ 4.2 Hz;
CH3N), 38.4 (d, JPC ˆ 10.0 Hz; CH2), 36.0 (d, JPC ˆ 16.0 Hz; CH2), 33.0, 31.0,
27.0, 26.5, 26.4, 26.1 (s; CH2), 1.85 ppm (d, JPC ˆ 5.8 Hz; CH3Si); 29Si{1H}
NMR (CDCl3): d ˆ 0.7 ppm (d, JPSi ˆ 8.9Hz); elemental analysis calcd (%)
for C31H59N4SiP: C 68.08, H 10.87, N 10.24; found: C 68.01, H 10.95, N 10.20.
3
3
56.0 ppm; 1H NMR (CDCl3): d ˆ 3.30 (sept d, JH,H ˆ 6.6 Hz, JP, H
ˆ
3
3
11.4 Hz, 2H; CHN), 3.00 (sept d, JH,H ˆ 6.6 Hz, JP,H ˆ 11.1 Hz, 2H;
Chem. Eur. J. 2002, 8, No. 23
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5309

G. Bertrand, A. Baceiredo et al.
FULL PAPER
2
3
3
3
3
CHN), 2.64 (dq, JP, H ˆ 3.6 Hz, JH,H ˆ 7.1 Hz, 2H; PCH2), 1.32 (d, JH,H
ˆ
ˆ
(d, JP, H ˆ 6.6 Hz, 12H; CH3CH), 1.33 (d, JH,H ˆ 6.6 Hz, 12H; CH3CH),
1.18 (s, 3H; CH3CHSi), 1.15 ppm (s, 18H; CH3CHSi); 13C{1H} NMR
(C6D6): d ˆ 180.5 (d, 1JP, C ˆ 97.5 Hz, P ˆ C), 153.5 (d, 2JP, C ˆ 35.2 Hz, C ˆ N),
51.2 (d, 2JP, C ˆ 5.7 Hz, CHN), 47.2 (s, CHN), 46.0 (s, CHN), 41.4 (s, CH3N),
3
3
6.6 Hz, 6H; CH3CH), 1.22 (d, JH,H ˆ 7.1 Hz, 3H; CH3CP), 1.11 (d, JH,H
3
6.6 Hz, 6H; CH3CH), 1.07 (d, JH,H ˆ 6.6 Hz, 6H; CH3CH), 0.90 ppm (d,
3JH,H ˆ 6.6 Hz, 6H; CH3CH); 13C{1H} NMR (CDCl3): d ˆ 123.4 (d, JP, C
ˆ
2
12.0 Hz, CN), 47.7 (d, 2JP, C ˆ 11.7 Hz, CHN), 47.1 (d, 2JP,C ˆ 11.2 Hz, CHN),
24.9(d, JP, C ˆ 6.5 Hz, CH3CHNP), 24.7 (d, 2JP, C ˆ 6.3 Hz, CH3CHNP), 19.6
2
24.7 (d, 2JP, C ˆ 6.6 Hz, CH3C), 24.5 (d, 2JP, C ˆ 6.7 Hz, CH3C), 24.4 (d, 2JP, C
ˆ
ˆ
(s, CH3CHN), 19.3 (s, CH3CHN), 18.5 (s, CH3CSi), 14.4 ppm (s, CHSi);
29Si{1H} NMR (C6D6): d ˆ À28.7 ppm.
2
1
6.4 Hz, CH3C), 22.6 (d, JP, C ˆ 16.9Hz, CH3CP), 16.1 ppm (d, JP, C
24.3 Hz, PCH); IR (pentane): nÄ ˆ 2232 cmÀ1 (CN); MS (EI): m/z: 285
Crystal structure determination for 4a and 9a: Crystal data for both
structures are presented in Table 1. All data were collected at low
temperatures by using an oil-coated shock-cooled crystal on a STOE-
IPDS diffractometer. The structures were solved by direct methods
(SHELXS-97)[21] and refined by using the least-squares method on F 2.[22]
All non-hydrogen atoms were refined anisotropically. The hydrogen atoms
of the molecules were geometrically idealized and refined using a riding
model. A numerical absorption correction was employed for structure 9a;
‡
[M ]; elemental analysis calcd (%) for C15H32N3P: C 63.12, H 11.30, N
14.72; found: C 63.18, H 11.38, N 14.70
General procedure for the metalation silylation of phosphinonitriles 6'a,
6'b, 6c, and 6d: One equivalent of base (n-BuLi or LDA) was added to a
solution of the nitrile 6'a, 6'b, 6c, or 6d (1 mmol) in THF (10 mL) at
À788C. After the temperature increased to 08C, the solution mixture was
stirred at this temperature for 45 min. The mixture was then cooled again at
À788C, and one equivalent of R3SiCl (R ˆ Me or iPr) was added. After the
solution was slowly heated to room temperature (30 min), the solvent was
removed under vacuum, and the residue was extracted with pentane
(20 mL).
the min/max transmissions were 0.8338/0.9375. Two positions for
disordered cyclohexyl group in 9a were refined anisotropically by using
197 ADP and distance restraints.
a
CCDC-185685 and CCDC-185686 contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of charge via
www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cambridge Crys-
tallographic Data Centre, 12 Union road, Cambridge CB21EZ, UK; (fax:
(‡44)1223 336 033; or e-mail: deposit@ccdc.cam.ac.uk).
a-Phosphinonitrile 6e: Yellow oil (92% yield); 31P{1H} NMR (C6D6): d ˆ
1
3
3
47.4 ppm; H NMR (C6D6): d ˆ 3.57 (sept d, JH,H ˆ 6.6 Hz, JP, H ˆ 12.1 Hz,
2H; CHN), 3.38 (sept d, 3JH,H ˆ 6.6 Hz, 3JP, H ˆ 11.9Hz, 2H; CHN), 1.89(d,
2JP, H ˆ 2.5 Hz, 1H; PCH), 1.25 (d, JH,H ˆ 6.6 Hz, 6H; CH3CH), 1.14 (d,
3
3JH,H ˆ 6.6 Hz, 6H; CH3CH), 1.07 (d, 3JH,H ˆ 6.6 Hz, 6H; CH3CH), 0.99 (d,
3JH,H ˆ 6.6 Hz, 6H; CH3CH), 0.22 ppm (s, 9H; CH3Si); 13C{1H} NMR
2
2
(C6D6): d ˆ 121.1 (s, CN), 48.3 (d, JP,C ˆ 5.7 Hz, CHN), 48.0 (d, JP, C
ˆ
2
2
7.0 Hz, CHN), 25.1 (d, JP, C ˆ 6.5 Hz, CH3C), 24.4 (d, JP, C ˆ 8.5 Hz,
2
2
Acknowledgements
CH3C), 24.1 (d, JP, C ˆ 8.8 Hz, CH3C), 24.0 (d, JP, C ˆ 9.1 Hz, CH3C), 21.3
1
3
(d, JP, C ˆ 56.6 Hz, PCH), À1.3 ppm (d, JP, C ˆ 6.3 Hz, CH3Si); IR (C6D6):
nÄ ˆ 2210 cmÀ1 (CN).
Thanks are due to the CNRS and UCR for financial support of this work.
Ketenimine 7d: Yellow oil (89% yield); 31P{1H} NMR (C6D6): d ˆ
61.4 ppm; 1H NMR (C6D6): d ˆ 3.57 (sept d, JH,H ˆ 6.6 Hz, JP, H
ˆ
3
3
3
3
12.1 Hz, 2H; CHN), 3.38 (sept d, JH,H ˆ 6.6 Hz, JP, H ˆ 11.9Hz, 2H;
[1] a) A. Igau, H. Gr¸tzmacher, A. Baceiredo, G. Bertrand, J. Am. Chem.
Soc. 1988, 110, 6463; b) D. Bourissou, O. Guerret, F. P. Gabbai, G.
Bertrand, Chem. Rev. 2000, 100, 39 .
[2] G. Alcaraz, U. Wecker, A. Baceiredo, F. Dahan, G. Bertrand, Angew.
Chem. 1995, 107, 1358; Angew. Chem. Int. Ed. Engl. 1995, 34, 1246.
[3] a) V. Piquet, A. Baceiredo, H. Gornitzka, F. Dahan, G. Bertrand,
Chem. Eur. J. 1997, 3, 1757; b) V. Piquet, A. Baceiredo, F. Dahan, G.
Bertrand, C. R. Acad. Sci. Ser. IIc 1998, 123.
[4] a) F. Mathey, C. Charrier, N. Maigrot, A. Marinetti, L. Ricard, N. H.
Tran Huy, Comments Inorg. Chem. 1992, 13, 61; b) S. Kummer, U.
Zenneck, in Comprehensive Heterocyclic Chemistry II, Vol. 1b (Eds.:
A. R. Katritzky, C. W. Rees, E. F. Scriven), Pergamon, Oxford, 1996,
p. 1157.
[5] a) H. Gr¸tzmacher, H. Pritzkow, Chem. Ber. 1989, 122, 1417; b) N. V.
Lukashev, A. D. Averin, P. E. Zhichkin, M. A. Kazankova, I. P.
Beletskaya, Phosphorus, Sulfur Silicon Relat. Elem. 1996, 109 110,
609.
[6] G. Alcaraz, R. Reed, A. Baceiredo, G. Bertrand, J. Chem. Soc. Chem.
Commun. 1993, 1354.
[7] R. Reed, G. Bertrand, in Phosphorus-31NMR Spectral Properties in
Compound Characterisation and Structural Analysis (Eds.: L. D. Quin,
J. G. Verkade), VCH, New York, 1994, pp. 189 200.
[8] S. Goumri-Magnet, O. Polishchuk, H. Gornitzka, C. J. Marsden, A.
Baceiredo, G. Bertrand, Angew. Chem. 1999, 111, 3938; Angew. Chem.
Int. Ed. 1999, 38, 3727.
[9] a) T. S. Stevens, E. M. Creighton, A. B. Gordon, M. McNicol, J. Chem.
Soc. 1928, 3193; b) Advanced Organic Chemistry, 4th ed. (Ed.: J.
March), Wiley-Interscience, New York, 1992, pp. 1100 1102.
[10] A. Igau, A. Baceiredo, G. Trinquier, G. Bertrand, Angew. Chem. 1989,
101, 617; Angew. Chem. Int. Ed. Engl. 1989, 28, 621.
3
3
CHN), 1.89(d, JP,H ˆ 9.0 Hz, 3H; PCCH3), 1.21 (d, JH,H ˆ 6.6 Hz, 6H;
3
CH3CH), 1.19(d, JH,H ˆ 6.6 Hz, 6H; CH3CH), 1.06 (d, 3JH,H ˆ 6.6 Hz, 12H;
CH3CH), 0.38 ppm (s, 9H; CH3Si); 13C{1H} NMR (C6D6): d ˆ 185.2 (d,
2JP, C ˆ 9.4 Hz, P-C ˆ C), 48.1 (d, JP, C ˆ 8.1 Hz, CHN), 47.3 (d, JP, C
ˆ
2
2
1
2
À
10.9Hz, CHN), 38.6 (d, JP, C ˆ 8.8 Hz, P C), 25.3 (d, JP, C ˆ 6.0 Hz,
2
2
CH3C), 24.9(d, JP,C ˆ 6.7 Hz, CH3C), 24.8 (d, JP, C ˆ 6.8 Hz, CH3C), 24.3
2
2
(d, JP, C ˆ 6.5 Hz, CH3C), 22.0 (d, JP, C ˆ 63.5 Hz, PCCH3), 1.7 ppm (s,
CH3Si); IR (C6D6): nÄ ˆ 2028 cmÀ1 (C C N).
ˆ ˆ
1,2-Dihydro-1,2-azaphosphete 4b: 31P{1H} NMR (CDCl3): d ˆ 59.1 ppm;
1H NMR (CDCl3): d ˆ 3.61 (sept, JHH ˆ 6.6 Hz, 2H; CHN), 3.34 (sept d,
3
3JH,H ˆ 6.6 Hz, JPH ˆ 8.6 Hz, 2H; CHN), 2.34 (s, 6H; CH3N), 1.19(d,
3
3JHH ˆ 6.6 Hz, 6H; CH3CH), 1.18 (d, JH,H ˆ 6.6 Hz, 6H; CH3CH), 1.17 (d,
3
3JH,H ˆ 6.6 Hz, 6H; CH3CH), 1.11 (d, JH,H ˆ 6.6 Hz, 6H; CH3CH),
3
0.12 ppm (s, 9H; CH3Si); 13C{1H} NMR (CDCl3): d ˆ 146.9(d, JP, C
ˆ
ˆ
2
2
À ˆ
À ˆ
À ˆ
19.1 Hz, P C C), 123.6 (s, P C C ), 49.0 (s, CHN C ), 46.7 (d, JP, C
À
4.2 Hz, CHN P), 43.7 (brd, CH3N), 23.2 (s, CH3C), 21.9(s, CH3C), 2.1 ppm
3
(d, JP, C ˆ 5.8 Hz, CH3Si).
Ketenimine 7'c: Yellow oil (91% yield); 31P{1H} NMR (C6D6): d ˆ
53.1 ppm; 1H NMR (C6D6): d ˆ 3.60 (sept d, JH,H ˆ 6.8 Hz, JP, H
ˆ
ˆ
3
3
2
3
11.0 Hz, 4H; CHN), 3.27 (d, JP, H ˆ 10.2 Hz, 1H; PCH), 1.43 (d, JH,H
6.8 Hz, 12H; CH3CH), 1.42 (d, 3JH,H ˆ 6.8 Hz, 12H; CH3CH), 1.31 ppm (m,
21H; CH3CHSi); 13C{1H} NMR (C6D6): d ˆ 175.7 (d, JP, C ˆ 36.6 Hz,
2
2
1
ˆ
PC C), 47.4 (d, JP, C ˆ 11.0 Hz, CHN), 27.4 (d, JP, C ˆ 8.8 Hz, PC), 24.7 (d,
2JP, C ˆ 5.8 Hz, CH3C), 24.5 (d, JP, C ˆ 9.2 Hz, CH3C), 18.3 (s, CH3CSi),
2
12.7 ppm (s, CHSi); IR (C6D6): nÄ ˆ 2044 cmÀ1 (C C N).
ˆ ˆ
Ketenimine 7'd: Yellow oil (69% yield); 31P{1H} NMR (C6D6): d ˆ
61.4 ppm; 1H NMR (C6D6): d ˆ 3.46 (sept d, JH,H ˆ 6.6 Hz, JP,H ˆ 11.0 Hz,
3
3
3
3
4H; CHN), 1.86 (d, JP, H ˆ 9.4 Hz, 3H; PCCH3), 1.27 (d, JH,H ˆ 6.6 Hz,
3
12H; CH3CH), 1.25 (d, JH,H ˆ 6.6 Hz, 12H; CH3CH), 1.11 (s, 18H;
[11] D. Lentz, M. Anibaro, D. Preugschat, G. Bertrand, J. Fluorine Chem.
1999, 89, 73.
CH3CHSi), 1.04 ppm (s, 3H; CHSi); 13C{1H} NMR (C6D6): d ˆ 184.7 (d,
2JP, C ˆ 11.1 Hz, PC ˆ C), 48.7 (d, JP, C ˆ 11.8 Hz, CHN), 40.9(d, JP, C
ˆ
2
1
[12] a) R. Appel, V. Barth, F. Knoch, Tetrahedron Lett. 1980, 21, 1923;
b) R. Appel, V. Barth, F. Knoch, Chem. Ber. 1983, 116, 9 38; c) N.
Maigrot, C. Charrier, L. Ricard, F. Mathey, Polyhedron 1990, 9, 1363;
d) W. W. Schoeller, U. Tubbesing, A. B. Rozhenko, Eur. J. Inorg.
Chem. 1998, 951; e) O. Schmidt, A. Fuchs, D. Gudat, M. Nieger, W.
Hoffbauer, E. Niecke, W. W. Schoeller, Angew. Chem. 1998, 110, 9 9 5;
Angew. Chem. Int. Ed. Engl. 1998, 37, 949; f) E. Niecke, A. Fuchs, M.
2
2
4.7 Hz, PC), 25.8 (d, JP, C ˆ 8.0 Hz, CH3C), 25.3 (d, JP, C ˆ 7.0 Hz, CH3C),
2
20.1 (d, JP, C ˆ 6.4 Hz, PCCH3), 17.1 (s, CH3CSi), 13.5 ppm (s, CHSi); IR
(C6D6): nÄ ˆ 2026 cmÀ1 (C C N).
ˆ ˆ
1,4-Azaphosphabutadiene 8b: Yellow oil (58% yield); 31P{1H} NMR
(C6D6): d ˆ 113.1 ppm; 1H NMR (C6D6): d ˆ 4.30 (sept, JH,H ˆ 6.6 Hz,
3
2H; CHN), 3.28 (sept, 3JH,H ˆ 6.6 Hz, 2H; CHN), 2.66 (s, 6H; CH3N), 1.36
5310
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Chem. Eur. J. 2002, 8, No. 23

Rearrangements
5305 5311
Nieger, Angew. Chem. 1999, 111, 3213; Angew. Chem. Int. Ed. Engl.
1999, 38, 3028.
Barbieux-Flammang, R. Flammang, C. Wentrup, Chem. Eur. J. 1996,
2, 1318; c) J. Finnerty, U. Mitschke, C. Wentrup, J. Org. Chem. 2002, 67,
1084.
[13] This rearrangement can be related to the 1,3-shifts of electron-
donating substituents in the case of oxoketenimines and imidoylke-
tenes : a) C. Wentrup, V. V. R. Rao, W. Frank, B. E. Fullon, D. W. J.
Moloney, T. Mosandl, J. Org. Chem. 1999, 64, 3608; b) J. Finnerty, J.
Andraos, Y. Yamamoto, M. W. Wong, C. Wentrup, J. Am. Chem. Soc.
1998, 120, 1701, and references therein.
[14] a) R. F. Cunico, C. P. Kuan, J. Org. Chem. 1992, 57, 1202; b) L. F.
Clarke, A. F. Hegarty, J. Org. Chem. 1992, 57, 1940, and references
therein.
[15] a) G. Boche, M. Marsch, K. Harms, Angew. Chem. 1986, 98, 373;
Angew. Chem. Int. Ed. Engl. 1986, 25, 373; b) D. Croisat, J. Seyden-
Penne, T. Strzalko, L. Wartski, J. Corset, F. Froment, J. Org. Chem.
1992, 57, 6435.
[17] G. R. Krow, Angew. Chem. 1971, 83, 455; Angew. Chem. Int. Ed. Engl.
1971, 10, 435.
[18] R. Appel, J. H¸nerbein, N. Siabalis, Angew. Chem. 1987, 99, 810;
Angew. Chem. Int. Ed. Engl. 1987, 26, 779.
[19] L. N. Markovski, V. D. Romanenko, A. V. Ruban, Chemistry of
Acyclic Compounds of Two-Coordinated Phosphorus, Naukova
Dumka, Kiev, 1988.
[20] S. Goumri, Y. Leriche, H. Gornitzka, A. Baceiredo, G. Bertrand, Eur.
J. Inorg. Chem. 1998, 1539.
[21] G. M. Sheldrick, Acta Crystallogr. Sect. A 1990, 46, 467.
[22] G. M. Sheldrick, SHELXL-97, Program for Crystal Structure Refine-
ment, University of Gˆttingen, Gˆttingen (Germany), 1997.
[16] a) R. Wolf, M. W. Wong, C. H. L. Kennard, C. Wentrup, J. Am. Chem.
Soc. 1995, 117, 6789; b) R. Wolf, S. Stadtm¸ller, M. W. Wong, M.
Received: May 21, 2002 [F4106]
Chem. Eur. J. 2002, 8, No. 23
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5311