Extremely base-resistant organic phosphazenium cations

Article abstract of DOI:10.1002/chem.200500837

A series of peralkylated polyaminophosphazenium cations exhibiting extraordinary base resistance under phase-transfer conditions were efficiently synthesized from readily available starting materials. Their half lives under these conditions exceed those of the most stable conventional organic cations by factors of up to 3000.

Full text of DOI:10.1002/chem.200500837

FULL PAPER
DOI: 10.1002/chem.200500837
Extremely Base-Resistant Organic Phosphazenium Cations
Reinhard Schwesinger,*[a] Reinhard Link,[b] Peter Wenzl,[c] Sebastian Kossek,[d] and
Manfred Keller[a]
Abstract: A series of peralkylated polyaminophosphazenium cations exhibiting ex-
traordinary base resistance under phase-transfer conditions were efficiently synthe-
sized from readily available starting materials. Their half lives under these condi-
tions exceed those of the most stable conventional organic cations by factors of up
to 3000.
Keywords: cations · phase-transfer
catalysis
·
phosphazenes
·
phosphorus
Introduction
ions[7] (Table 1), tetraalkylphosphonium,[3,7,8] and N-alkyl-4-
dialkylaminopyridinium ions.[4]
Lipophilic organic cations in molar or catalytic amounts are
indispensable auxiliaries for solubilization of anionic re-
agents in organic media. The catalytic application, phase-
transfer catalysis, has become an essential methodology par-
ticularly for industrial processes.[1] Among these the most
important processes are base catalyzed and often utilize
aqueous alkali hydroxides as second phase. A vast variety of
organic cations has been used as catalysts for such reactions,
but conventional organic cations have limited base resist-
ance. This instability can be due to Hofmann degrada-
tion,[2–4] nucleophilic dealkylation,[4,5] Sommelet–Hauser re-
arrangement, or benzylic deprotonation with subsequent
Stevens rearrangement in the case of quaternary ammonium
ions[6] or by hydrolysis in the case of bis(triphenylphospha-
ne)iminium ion,[4] tetraphenylarsonium[4] and -phosphonium
In context with our workon extremely strong uncharged
bases we[9–11] and others[4,12–15] learnt about the unique stabil-
ity of polyaminophosphazenium cations under basic condi-
tions. In this paper we detail our longstanding efforts to
identify or develop phosphazenium cations with maximum
base resistance.
Results and Discussion
A survey of phosphazenium ions to be discussed in this
paper is given in Figure 1. The parameters considered were
the size of the conjugated system and the nature of the alkyl
substituents on nitrogen atoms.
Table 1. Half lives of phase transfer catalysts in 50% NaOH/chloroben-
zene at 1008C.
[a] Prof. Dr. R. Schwesinger, Dr. M. Keller
Chemisches Laboratorium
1
Entry
Compound
t = [h]
2
Institut für Organische Chemie und Biochemie
der Universität Freiburg
Albertstrasse 21, 79104 Freiburg (Germany)
Fax : (+49)761-203-8712
1
2
3
4
5
6
7
8
Bu4P+Clꢀ
Ph4As+Clꢀ
Ph3PNPPh3+Clꢀ
Bu4N+Clꢀ
1a·Cl
1b·Cl
1e·Cl
1 f·Cl
2a·Cl
2b·Cl
2c·Cl
2d·Cl
3·Cl
4a·Cl
4b·Cl
0.08/208C[4]
2/208C[a]
1.1/208C[a]
0.33
0.33
0.9
67
E-mail: rschwesi@chemie.uni-freiburg.de
[b] Dr. R. Link
Current address: CU-Chemie Uetikon GmbH
Raiffeisenstrasse 4, 77933 Lahr (Germany)
6
9
8 (9[4]
21
)
[c] Dr. P. Wenzl
Current address: Fluka-Chemie AG, Industrie-Strasse 25
9471 Buchs, SG (Switzerland)
10
11
12
13
14
15
7
8
[d] Dr. S. Kossek
3.7
33/1108C
477/1108C
Current address: Protiveris
9700 Great Seneca Hwy, Rockville, MD 20850 (USA)
Supporting information for this article is available on the WWW
under http://www.chemeurj.org/ or from the author.
[a] CH2Cl2 as solvent.[4]
Chem. Eur. J. 2006, 12, 429 – 437
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
429

Figure 1. Phosphazenium ions and their structures described in this paper derived from molecular modeling studies.
For the conception of phosphazenium ions of maximum
base resistance it is essential to know their potential paths
of decay. For tetrakis(dialkylamino)phosphonium ions 1+
four such paths have been observed (Scheme 1):[16]
3) b-Elimination with formation of an imine and a phos-
phorous acid amide.
4) Hydrolysis by attackof hydroxide at the phosphorus
atom.
1) Hofmann degradation.
2) Nucleophilic substitution on (alkyl-)carbon.
It was reasonable to assume that the ease of decay of per-
alkylated polyaminophosphazenium ions like 1+, 2+, 3+,
and 4+ correlates with the
degree of charge delocalization
(hence with the base strength
of the product of dealkylation
by means of path 1 or 2), as in
all four modes of decay merely
complete loss of the cationic
resonance in the rate-limiting
step is involved. The rate of
decay in path 4 also depends on
steric shielding at the phospho-
rus nuclei. The relative impor-
tance of the two factors was, a
priori, not evident.
To evaluate the influence of
the size of the conjugated
system we first investigated the
stabilities within the series of
permethylated cations 1a+, 2a+,
Scheme 1. Modes of decay of peralkylated tetraaminophosphonium cations (paths 1–4).
3+, and 4a+.
430
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Chem. Eur. J. 2006, 12, 429 – 437

Phosphazenium Cations
FULL PAPER
Permethylated systems: The P1 cation 1a+[17,18] has long
been known, yet prepared rather inefficiently. An improved
synthesis from our lab has been reported.[19]
followed by anion exchange with NH4BF4, respectively
(Scheme 3).
For 2a+[20] we envisioned an improvement of our original
[21]
route (Scheme 2)[9] through the coupling of 5·BF4
and
6a,[11,18,22,23] now starting with the readily available perchloro-
diphosphazenium salt 7·PCl6.[24,26,27]
Scheme 3. Syntheses of 3·BF4 and 4·BF4.
The stability of the phosphazenium cations 1a+, 2a+, 3+,
and 4a+ was evaluated by determining their half lives as
chlorides in the system 50% NaOH/chlorobenzene at 1008C
+
(Table 1). The order of increasing stability is P1+ <P3+ <P2
+
<P5 (entries 5, 9, 13, 14), with 1a+ already being as stable
Scheme 2. Syntheses of 2·BF4.
as Bu4N+. Except for P3+ <P2+, this is the order of increas-
ing resonance.
ꢀ
For the exchange of the PCl6 ion in 7·PCl6 there is no
straight forward protocol.[28] We thus had to settle with the
fact that aminolysis also produced equimolar amounts of the
corresponding P1 cations 1+. For a one-pot conversion a sol-
vent was needed that is stable to PCl5 as well as secondary
amines. Reaction of PCl5 with NH4Cl in a 3:1 molar ratio in
MeNO2 furnished 7·PCl6, which on reaction with dimethyla-
Pyrollidinyl-substituted systems: Substitution of the dime-
thylamino groups for 1-pyrrolidinyl groups enhances the ba-
sicity of phosphazene bases by some 1.5 pK units[10,11] and
should, therefore, improve the stability of cations by en-
hancing resonance. On the other hand, this substitution
allows for the competition by Hofmann degradation and,
due to reduction of the C-N-C angle, possibly reduces steric
shielding of the phosphorus nuclei against attackby hydrox-
ide (path 4). Due to the relatively low stability of 3+, only
the 1a+, 2a+, and 4a+ ions were modified. The ions 1b+[30]
and 2b+ were synthesized in excellent yields in analogy to
the permethylated systems. Ion 4b+ was synthesized from
6b.[11] It turned out, that 1b+, 2b+, and 4b+ are more stable
than the appropriate methylated system by factors of 2.7 to
15 (Table 1).
mine provided 2a+ as the BF4 salt in good yield together
ꢀ
with two unexpected products, HMPA and 8·BF4.[25] When
PCl5 was used instead of 7·PCl6 the 8+ ion was also formed
and presumably arises from a cascade reaction of MeNO2
with 5+ involving a fulminate!cyanate rearrangement,[29]
possibly via a tris(dimethylamino)isocyanatophosphonium
ion as intermediate.[20]
Because of literature reports on the potentially explosive
nature of MeNO2 in presence of strong Lewis acids, the ex-
plosive nature of fulminates, and the environmental con-
cerns about HMPA as a molar byproduct, this one-pot pro-
tocol was rejected in favor of a two-step alternative with
POCl3 as solvent for the first step.[24,27] Taking off the solvent
in vacuo, aminolysis of 7·PCl6 in chlorobenzene and treat-
ment with NH4BF4 afforded 2a·BF4 together with 1a·BF4,
from which 2a·BF4 can be separated readily by crystalliza-
tion.
Piperidinyl-substituted systems: Substitution of dimethyl-
amino groups by 1-piperidinyl groups in the P2 system
(2c+), unexpectedly, did not enhance stability.
To impede Hofmann degradation in 2c+, methyl groups
were introduced by reaction of 7·PCl6 with cis-3,5-dimethyl-
piperidine. These methyl groups in 2d+ enforce either syn-
elimination or anti-elimination from a ring-inverted con-
former with two axial methyl groups (Scheme 4). The latter
path would cost some 6 kcalmolꢀ1 of conformational energy
according to force-field modeling studies.
The P3 and P5 systems 3·BF4 and 4a·BF4, respectively,
[11]
could be obtained through the coupling of 6a and 9·BF4
and through the reaction of 6a with PCl5 in chlorobenzene
Chem. Eur. J. 2006, 12, 429 – 437
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431

R. Schwesinger et al.
Scheme 4. Conformational preequilibrium for the Hofmann elimination
in cis-3,5-dimethylpiperidinyl-substituted phosphazenium cations.
Experimentally the methyl groups had no significant influ-
ence on the stability towards aqueous NaOH (Table 1), indi-
cating that in phosphazenium ions with two or more phos-
phorus atoms the Hofmann degradation (path 1) is not dom-
inant in the destruction of the cations by hydroxide. In fact,
according to modeling studies (Figure 1) the additional
methyl groups in 2d+ do not significantly enhance steric
shielding at phosphorus atom relative to 2c+.
Scheme 6. Synthesis of 1e,f·BF4.
According to modeling studies, the ion 1e+ can occur in
three nearly isoenergetic symmetrical conformations (within
1.8 kcalmolꢀ1; Figure 2).
sec-Alkyl-substituted systems: If in fact path 4 governs the
decay, sec-alkyl groups provide better steric protection from
degradation. Cyclohexyl-substituted phosphazenium cations
again would have to either undergo syn-elimination or
switch to anti-elimination from an energetically disfavored
ring-inverted conformer with axial leaving group
(Scheme 5).
Figure 2. Low-energy conformations derived from molecular modeling
Scheme 5. Conformational prerequisites for the Hofmann elimination in
studies of 1e+ in the order of increasing energy.
sec-alkyl(methyl)aminophosphonium cations 1e,f+.
In all the conformers the nitrogen atoms are in equatorial
positions. One nitrogen atom in an axial position should
raise the energy by some 5 kcalmolꢀ1. The total release of
strain on Hofmann degradation of conformer S4(I) was pre-
dicted to be only approximately 8–9 kcalmolꢀ1, so that the
much lower release of steric strain in the transition state
should probably not outbalance the unfortunate conforma-
tional prerequisites.
In the series of quaternary ammonium ions this concept
has so far not been rewarding; the extremely crowded tricy-
clohexylmethylammonium ion is less stable towards bases
than a tetra-N-alkylammonium ion.[4] The much higher re-
lease of steric energy in the transition state of the Hofmann
degradation of the former presumably outbalances confor-
mational effects.
As the Hofmann degradation is not dominant under
phase-transfer conditions in systems with two (or more)
phosphorus atoms, we envisioned being able to apply this
concept to the more readily available P1 systems. As a P1
cation with four dicyclohexylamino substituents seemed in-
accessible for steric reasons, 1e+ with four cyclohexyl-
(methyl)amino substituents was the next target.
X-ray analyses of 1e·BF4 (Figure 3), 1e·PF6, and
[32]
1e·O3SC4F9
provided further insight into the conforma-
tional situation. In all three salts the same low-energy S4(I)
conformation depicted in Figure 2 is met. In contrast to the
structure derived from molecular modeling studies, the tet-
rahedral geometry around the phosphorus atom is slightly
distorted with two N-P-N angles at 110.8–112.18 and two at
104.3–105.48.
The synthesis of 10a·I has already been reported.[31a] We
utilized a modified protocol with improved yield. Ion 1e+
proved to be very easily obtainable by means of phase-trans-
fer methylation of 10a·BF4 (Scheme 6).
In fact, although only a P1 system, 1e+ turned out to be
extremely stable under phase-transfer conditions; it is com-
parable to the P5 system 4a+ and is only beaten by 4b+.
432
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Chem. Eur. J. 2006, 12, 429 – 437

Phosphazenium Cations
FULL PAPER
1) Greatly enhanced stability towards aqueous base.
2) High anionic reactivity due to comparatively weakshort-
range cation–anion interactions (e.g. like hydrogen
bridges in Bu4N+[33]
)
3) With respect to a given molecular weight the compara-
tively spherical shape of the novel cations (e.g. versus
Bu4N+, see Figure 1) leads to a maximized cation–anion
separation in the ion pairs and thus improves anion reac-
tivities for electrostatic reasons.
In particular, ball-shaped 4a+ has already found broad
application.[13–15,34] A number of the described cations have
been evaluated as counterions for the generation of anhy-
drous fluoride salts.[35]
Figure 3. X-ray crystal structure of 1e·BF4.
Experimental Section
General: Melting points (m.p.; uncorrected): Apparatus Dr. Tottoli and
BockMonoscop M; IR: Perkin–Elmer 457 and Philips PU 9706 spec-
trometers; elemental analyses: Perkin–Elmer Elemental Analyzer 240;
1H NMR (internal standards TMS=tetramethylsilane): 90 MHz Varian
CM 390, 250 MHz Bruker AC 250, and 400 MHz Bruker AM 400 spec-
trometer; 13C NMR (internal standard TMS): 25.2 MHz Bruker WP 80
and 100.6 MHz Bruker AM 400 spectrometer; 31P NMR (external stan-
dard): Bruker AM 400 spectrometer. MM2-based modeling studies were
performed with PCModel 8.5 with additional parameters gained by fitting
to X-ray structures.
In the isopropyl-substituted ion 1 f+, synthesized analo-
gously from 10b·I,[31] anti-periplanar N-C-C-H alignments
are present in all conformers (Scheme 5). In 1 f+, the calcu-
lated energy window of the three conformers is only
1.3 kcalmolꢀ1 with the same sequence as in 1e+. X-ray anal-
ysis of 1 f·BF4 confirms the preference of 1 f+ for the S4(I)-
conformation (Figure 4).
MeCN was purchased from Fluka Chemie AG (Switzerland) and stored
over molecular sieves 3 Š, H2O content <0.001%.
Aqueous NH3, powdered charcoal, Na2O, NaOH, NaCl, Na2SO4,
NaBPh4, NaBF4, NH4BF4, KI, MgSO4, BaO, H3PO4, EtOH, EtOAc,
MeOAc, iPrOAc, and Me2CO were used as purchased from Fluka
Chemie AG (Switzerland). KCl and PCl5 were used as purchased from
Riedel-deHan. 70% aqueous EtNH2 was used as purchased from
Merck/Darmstadt. POCl3 was distilled under N2; MeNO2 was distilled
from CaCl2 and stored over molecular sieves 3 Š; CH2Cl2 and PhCl,
specified as “absolute” were distilled over P2O5 and stored over molecu-
lar sieves 3 Š; EtCN was stirred over KMnO4 until the violet color per-
sisted, filtered and distilled over P2O5; other solvents were purified by
simple distillation; NEt3 was first distilled from p-toluenesulfonyl chlo-
ride (ca. 2 mol-%), then over Na2O or BaO; pyrrolidine, piperidine, gas-
eous amines, and NH3 were distilled or passed over Na2O or BaO; MeI
was distilled and stored over 4 Š molecular sieves. NH4Cl was dried in
high vacuum for 1 h at 508C.
Tetrakis(cyclohexylamino)phosphonium iodide (10a·I)[31a] and tetrakis-
(cyclohexylamino)phosphonium tetrafluoroborate (10a·BF4): Cyclohexyl-
amine (54.56 g, 550 mmol) was dissolved in absolute CH2Cl2 (125 mL)
and cooled to ꢀ408C. With cooling in a dry-ice bath, PCl5 (11.45 g,
55 mmol) was added at such a rate that the temperature did not exceed
ꢀ308C. The mixture was then allowed to warm to room temperature
until all PCl5 had dissolved. It was then gradually heated to reflux, held
at reflux for 4 h, and cooled to room temperature. The solvent was re-
moved, the residue was dissolved in H2O/MeOH 2:1 (ca. 750 mL), KI
(10.0 g, 60 mmol) in H2O (20 mL) was added, and the was mixture kept
at 48C for 20 h. The precipitate was isolated by suction, washed with a
small amount of H2O/MeOH 2:1 at ꢀ48C, and dried in high vacuum, af-
Figure 4. X-ray crystal structure of 1 f·BF4.
Indeed, 1 f+ (Table 1) turned out clearly less stable than
1e+.
Conclusion
1
fording colorless crystals (27.5 g, 90%). M.p. 2568C; H NMR (250 MHz,
CDCl3, 308C, TMS): d=1.02–2.11 (m, 40H; CH2), 3.04 (m, 4H; CH),
4.18 ppm (m, 4H; NH).
The novel phosphazenium ions offer several advantages as
counterions particularly in reactions with strongly basic and/
or strongly nucleophilic anions. These advantages include:
10a·BF4: 10a·I was dissolved in CH2Cl2 and shaken three times with a
twofold excess of saturated aqueous NaBF4. The organic layer was dried
with MgSO4 and the solvent was removed in vacuo, affording a crystal-
Chem. Eur. J. 2006, 12, 429 – 437
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433

R. Schwesinger et al.
line residue (m.p. 2228C). The 1H NMR spectrum corresponded to that
of 10a·I.
CCDC-270540 (1e·PF6), and CCDC-270541 (1e·BF4) contain the supple-
mentary crystallographic data for this paper. These data can be obtained
free of charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
Tetrakis[cyclohexyl(methyl)amino]phosphonium
tetrafluoroborate
(1e·BF4): In a two-necked 500 mL flask with dropping funnel and reflux
condenser chlorobenzene (100 mL) and 50% aqueous NaOH (100 mL)
were added to 10a·BF4 (15.0 g, 29.0 mmol). Dimethyl sulfate (18.53 g,
147 mmol) was added with vigorous stirring, whereby the mixture
warmed up to boiling temperature and 10a·BF4 dissolved completely.
After 12 h of stirring, the mixture was quenched with H2O (200 mL), the
organic phase was diluted with CH2Cl2 (100 mL) and separated, and the
aqueous phase was extracted once with CH2Cl2 (100 mL). The combined
organic phases were dried over MgSO4 and the solvent was removed in
vacuo. Recrystallization from iPrOH afforded colorless crystals (14.65 g,
88%). M.p. 3158C (decomp); 1H NMR (250 MHz, CDCl3, 308C, TMS):
d=1.00–2.00 (m, 40H; CH2), 2.68 (d, 3J(P,H)=10 Hz, 12H; CH3),
3.01 ppm (m, 4H; CH); 31P NMR (202 MHz, CDCl3, 308C, 85 % H3PO4):
d=45.9 ppm (s); IR (KBr): n˜ =2934 (s), 2861 (s), 1475 (s), 1454 (m),
1386 (w), 1276 (m), 1223 (m), 1171 (m), 1150 (m), 1087 (vs), 1050 (vs),
1008 (vs), 977 (vs), 898 (w), 856 (w), 819 (w), 609 cmꢀ1 (w); elemental
analysis calcd (%) for C28H56N4BF4P (566.6): C 59.36, H 9.96, N 9.89;
found: C 59.16, H 9.84, N 9.87.
1,1,1,3,3,3-Hexakis(dimethylamino)-1l5,3l5-diphosphazenium tetrafluoro-
borate (2a·BF4) and tetrakis(dimethylamino)phosphonium tetrafluorobo-
rate (1a·BF4)
Method 1: see reference [24]: Yield 103–127 g, 72–89%; IR (KBr): n˜ =
3056, 2900, 2854, 2808, 2350, 2036, 1814, 1756, 1663, 1638, 1617, 1559,
1491, 1466, 1417, 1395, 1297, 1179, 1095, 1067, 1053, 981, 741, 631 cmꢀ1
;
elemental analysis calcd (%) for C12H36N7BF4P2 (427.2): C 33.74, H 8.49,
N 22.55; found: C 33.85, H 8.50, N 22.78.
For the isolation of 1a·BF4, a solution of NaBF4 (66 g, 0.60 mol) in H2O
(300 mL) was added with vigorous stirring to the combined aqueous
phases from which the salts of 2a+ were extracted. The solvent was
evaporated to dryness, and the residue was extracted with CH2Cl2 and fil-
tered from inorganic salts. The solvent was again evaporated to dryness
and the crude product was recrystallized from EtOH, yielding colorless
crystals (58 g, 60%); m.p. >2608C.
Methods 2 and 3: see the Supporting Information.
[Bis(dimethylamino)methyleneimino]tris(dimethylamino)phosphonium
X-ray structures of 1e·BF4, 1e·PF6, and 1 f·BF4: Suitable crystals of
1e·BF4 were obtained by slowly cooling a hot saturated solution of the
salt in iPrOH. Suitable crystals of 1e·PF6 were obtained by slow evapora-
tion of a saturated solution of the salt in Me2CO. Suitable crystals of
1 f·BF4 were obtained by slowly cooling a hot saturated solution of the
salt in iPrOH/H2O. Radiation: MoKa wavelength 0.71073 Š; absorption
correction: semiempirical from equivalents. The structures were solved
with SIR97[36] and refined with full-matrix least-squares methods on F2
with SHELXL-97.[37] Details of the data collection and refinement are
given in Table 2. The coordinates of the H atoms were calculated in ide-
alized positions and refined in a riding model. CCDC-270539 (1 f·BF4),
tetrafluoroborate (8·BF4) (potentially hazardous):
A slurry of PCl5
(20.8 g, 0.100 mol) in MeNO2 (50 mL) was prepared. Under N2 and cool-
ing with an ice bath, Me2NH (45 g, 1.00 mol) was passed into the solution
at such a rate that the temperature did not exceed 108C. The mixture
was then stirred for 2 h at room temperature and set aside for 7 d. Excess
Me2NH and MeNO2 were removed in vacuo at 308C bath temperature
and the residue was dried in high vacuum. The residue was dissolved in
ice/H2O (50 mL), and NaBF4 (20.0 g, 0.18 mol) dissolved in H2O (50 mL)
was added. The mixture was extracted with CH2Cl2 (3”50 mL), the com-
bined organic phases were concentrated in vacuo, dried in high vacuum,
digested several times with iPrOAc, and once more dried in high
vacuum, affording colorless needles
(12.1 g, 33%). M.p. 918C; 1H NMR
(250 MHz, CDCl3, 308C, TMS): d=
2.73 (d, 3J(P,H)=10.5 Hz, 18H; PN-
(CH3)3), 2.99 ppm (d, 5J(P,H)=0.5 Hz,
12H; CN(CH3)2); IR (KBr): n˜ =3450,
2928, 1656, 1546, 1478, 1422, 1406,
1389, 1295, 1181, 1084, 988, 934, 761,
687 cmꢀ1; elemental analysis calcd (%)
for C11H30N6BF4P (364.2): C 36.28, H
8.30, N 23.07; found: C 35.53, H 8.13,
N 22.34. As the purification of 8·BF4
proved troublesome (no suitable sol-
vent for recrystallization was found)
Table 2. Experimental details and results of the X-ray diffraction analyses of the compounds 1e·BF4, 1e·PF6,
and 1e·BF4.
1e·BF4
1e·PF6
1 f·BF4
formula
Mr
C28H56N4BF4P
566.55
C28H56N4F6P2
624.71
C16H40N4BF4P
406.30
T [K]
100 (2)
100 (2)
100 (2) K
crystal system
space group
a [Š]
tetragonal
I4
tetragonal
I4
orthorhombic
Pna21
11.4833 (2)
11.4833 (2)
12.0802 (3)
1592.97 (6)
2/1.181
11.6343 (2)
11.6343 (2)
12.0541 (2)
1631.61(7)
2/1.272
19.0700 (3)
8.6740 (3)
13.5409 (3)
2239.84 (10)
4, 1.205
b [Š]
c [Š]
V [Š3]
ꢀ
ꢀ
the corresponding PF6 and BPh4
salts (see the Supporting Information)
were prepared.
1,1,1,3,3,3-Hexa-1-pyrrolidinyl-1l5,3l5-
Z/1calcd [gcmꢀ3
]
m [mmꢀ1
F(000)
]
0.133
616
0.192
672
0.163
880
crystal size [mm]
q range [8]
index range
0.35”0.3”0.22
2.45–27.47
ꢀ14ꢁhꢁ14
ꢀ14ꢁkꢁ14
ꢀ14ꢁlꢁ15
7887/1830
[R(int)=0.0266]
100% (q=25.008)
0.968/0.927
1830/0/142
1.079
0.4”0.4”0.2
2.43–27.44
ꢀ15ꢁhꢁ15
ꢀ15ꢁkꢁ15
ꢀ15ꢁlꢁ15
7958/1858
[R(int)=0.0239]
99.9% (q=27.448)
0.967/0.880
1858/0/147
1.088
R1=0.0242
wR2=0.0628
R1=0.0247
wR2=0.0632
0.01 (7)
0.50”0.40”0.10
2.14–27.48
ꢀ24ꢁhꢁ24
ꢀ11ꢁkꢁ11
ꢀ17ꢁlꢁ17
19116/4379
[R(int)=0.0371]
99.9%
diphosphazenium
tetrafluoroborate
(2b·BF4) and tetra-1-pyrrolidinylphos-
phonium tetrafluoroborate (1b·BF4):
A slurry of 7·PCl6 (from 0.333 mol of
NH4Cl[24]) in absolute chlorobenzene
(300 mL) was prepared. At ꢀ208C
(dry-ice bath) pyrrolidine (570 g,
8.00 mol) was added with vigorous me-
chanical stirring. The mixture was then
allowed to warm to room temperature,
and was stirred for 1 h at room tem-
perature and then for 1 h at 608C.
NaBF4 (36.7 g, 0.334 mol) in H2O
(500 mL) was added with vigorous stir-
ring. The organic phase was separated
and the aqueous phase (kept for isola-
tion of 1b·BF4) was extracted once
with chlorobenzene (100 mL). The
reflections collected
completeness
max/min transmission
data/restraints/parameters
goodness of fit on F2
final R indices [I>2s]
0.979/0.859
4379/1/247
1.044
R1=0.0258
wR2=0.0662
R1=0.0289
wR2=0.0674
ꢀ0.09 (8)
R1=0.0284
wR2=0.0779
R1=0.0351
wR2=0.0812
ꢀ0.03 (7)
R indices all data
absolute structure parameter
largest difference peak/hole [eŠ
ꢀ3
]
0.228/ꢀ0.320
0.163/ꢀ0.348
0.379/ꢀ0.540
434
www.chemeurj.org
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2006, 12, 429 – 437

Phosphazenium Cations
FULL PAPER
combined organic phases were dried over Na2SO4 and concentrated in
vacuo. The crude product was recrystallized once from MeOH/H2O 1:2
(750 mL, mother liquor kept for isolation of 1b·BF4) and twice from
EtOAc (450 mL), to afford 148 g (84%) of colorless crystals. M.p. 1538C;
1H NMR (250 MHz, CDCl3, 308C, TMS): d=1.85–1.93 (m, 24H;
NCH2CH2), 3.06–3.17 ppm (m, 24H; NCH2CH2); IR (KBr): n˜ =2954
(CH), 2870, 1640, 1512, 1490 (N-CH3), 1457, 1362, 1342, 1293 (BF), 1278,
1238, 1202, 1120, 1081, 1048, 1014 (NC), 911, 868, 761 cmꢀ1; elemental
analysis calcd (%) for C24H48N7BF4P2 (583.5): C 49.41, H 8.29, N 16.80;
found: C 49.41, H 8.24, N 16.68.
57.3 mmol) in absolute chlorobenzene (10 mL) at such a rate that the
temperature did not exceed 08C (ice/NaCl bath). Then the mixture was
allowed to warm to room temperature, was stirred for 1 h at this temper-
ature and then was heated to 1108C. After 3 h the mixture was cooled,
the solvent was removed in vacuo, and the residue was dried in high
vacuum. The resulting oil was dissolved in MeOH (100 mL) and a solu-
tion of NaBPh4 (10 g) in MeOH (100 mL) was added. Brownish crystals
were collected by suction and recrystallized three times from MeOH, to
afford colorless crystals (9.6 g, 56%). M.p. 1208C; 1H NMR (250 MHz,
CDCl3, 308C, TMS): d=2.55 (d, 3J(P,H)=10.5 Hz, 12H; 3-CH3), 2.59 (d,
3
3J(P,H)=10.5 Hz, 36H; 1, 5-CH3), 6.90 (t, J(p-H,m-H)=7 Hz, 1H; Ar-p-
Salt 1b·BF4: The two aqueous phases were combined, and NaBF4 (36.7 g,
0.334 mmol) dissolved in H2O (100 mL) was added; the mixture was ex-
tracted twice with CH2Cl2 (2”200 mL). The solvent was removed in
vacuo and the residue was dried in high vacuum. Recrystallization from
EtOAc afforded colorless crystals (118 g, 90%). M.p. 1588C; 1H NMR
(250 MHz, CDCl3, 308C, TMS): d=1.98 (m, 16H; NCH2CH2), 3.25 ppm
(m, 16H; NCH2CH2); 13C NMR (100.6 MHz, CDCl3, 308C, TMS): d=
26.2 (NCH2CH2), 47.2 ppm (NCH2CH2); IR (KBr): n˜ =2950, 2858, 1478,
1457, 1338, 1292, 1248, 1204, 1114, 1047, 907, 869, 763 cmꢀ1; elemental
analysis calcd (%) for C16H32N4BF4P (398.2): C 48.26, H 8.10, N 14.07;
found: C 48.13, H 8.01, N 13.95.
1,1,1,3,3,3-Hexa-1-piperidinyl-1l5,3l5-diphosphazenium tetrafluoroborate
(2c·BF4): A slurry of 7·PCl6 (from 0.167 mol of NH4Cl[24]) in absolute
chlorobenzene (400 mL) was prepared. Piperidine (340 g, 4.00 mol) was
added with vigorous mechanical stirring at such a rate that the tempera-
ture did not exceed 08C (dry-ice bath). Then the mixture was allowed to
warm to room temperature and kept for 5 d. The solvent was evaporated
in vacuo and traces of chlorobenzene and excess piperidine were re-
moved azeotropically with a small amount of H2O. The product was dis-
solved in MeOH (500 mL), and cleared with powdered charcoal. NaBF4
(36.7 g, 0.334 mol) in H2O (500 mL) was then added with vigorous stir-
ring, and MeOH was removed in vacuo until crystallization occurred.
The crystals were collected by suction, and the crude product was recrys-
tallized once from Me2CO/EtOAc 3:1, to afford colorless crystals (96 g,
87%). M.p. 2258C (decomp); 1H NMR (250 MHz, CDCl3, 308C, TMS):
d=1.56 (m, 24H; NCH2CH2), 1.64 (m, 12H; NCH2CH2CH2), 3.04 ppm
(m, 24H; NCH2CH2); IR (KBr): n˜ =2916, 2836, 1446, 1393, 1351, 1275,
1203, 1157, 1109, 1068, 1021, 952, 852, 718, 658 cmꢀ1; elemental analysis
calcd (%) for C24H48N7BF4P2 (667.6): C 53.97, H 9.06, N 14.63; found: C
53.96, H 9.03, N 14.58.
H), 7.06 (t, 3J(o-H,m-H)=7 Hz, 1H; Ar-o-H), 7.44 ppm (brm, 2H; Ar-
m-H); IR (KBr): n˜ =3044, 2992, 2924, 2800, 1932, 1803, 1753, 1574, 1475,
1448, 1353, 1318, 1287, 1185, 1061, 1028, 982, 839, 796, 736, 727, 702,
650 cmꢀ1; elemental analysis calcd (%) for C40H68N10BP3 (792.8): C 60.60,
H 8.65, N 17.67; found: C 60.62, H 8.58, N 17.56.
1,1,1,3,3,5,5,5-Octakis(dimethylamino)-1l5,3l5,5l5-triphosphazadienium
tetrafluoroborate (3·BF4):
A slurry of 3·BPh4 (9.00 g, 11.3 mmol) in
MeOH (100 mL) was prepared, and Lewatit M500 (50 g, strongly basic
anion exchange resin, Clꢀ form) was added. The mixture was stirred by
rotating the flaskon a rotary evaporator (without vacuum) until the salt
had dissolved (ca. 12 h). The resin was filtered off and washed with
MeOH, and the filtrate was concentrated in vacuo. After dissolving in
H2O (100 mL) and clearing with powdered charcoal, a solution of NaBF4
(2.0 g, 18 mmol) in H2O (50 mL) was added. Precipitated 3·BF4 was iso-
lated by suction, dried in high vacuum, and recrystallized from ethyl piva-
late (crystallized at ꢀ1008C), to afford colorless crystals (3.9 g, 62%).
M.p. 2058C; 1H NMR (250 MHz, CDCl3, 308C, TMS): d=2.59 (d, 3J-
(P,H)=11 Hz, 12H; 3-CH3), 2.66 ppm (d, 3J(P,H)=10 Hz, 36H; 1, 5-
CH3); IR (KBr): n˜ =3500, 2992 (CH), 2916, 2802, 1804, 1725, 1541, 1481
(N-CH3), 1355, 1316 (BF), 1185, 1087, 1047, 981 (NC), 844, 791, 740,
647 cmꢀ1; elemental analysis calcd (%) for C16H48N10BF4P3 (560.4): C
34.30, H 8.63, N 25.00; found: C 34.06, H 8.51, N 24.49.
Tetrakis{[tris(dimethylamino)phosphoranyliden]amino}phosphonium tet-
rafluoroborate (4a·BF4): Compound 6a[11,22,23] (330 g, 1.85 mol) was dis-
solved in absolute chlorobenzene (280 mL) and cooled to ꢀ208C under
N2. With cooling in a dry-ice bath, PCl5 (42.4 g, 0.20 mol) was added at
such a rate that the temperature did not exceed ꢀ108C. Then the mixture
was gradually heated to reflux, was held at reflux for 6 h, and was cooled
to room temperature. A solution of NH4BF4 (130 g, 1.24 mol) in H2O
(700 mL) was added, the mixture was carefully shaken in a separating
funnel, and the organic phase (lower layer) was separated. The aqueous
phase was extracted once with chlorobenzene (100 mL), and the com-
bined organic phases were washed once with H2O (100 mL). The organic
phase was dried over MgSO4 and concentrated in vacuo. The residue was
dried in high vacuum, was recrystallized from MeOH/H2O 2:1 (600 mL)
and again was dried in high vacuum. Recrystallization from THF
(600 mL, cooling to ꢀ208C) yielded colorless crystals (149 g, 90%). M.p.
>2708C (decomp); 1H NMR (250 MHz, CDCl3, 308C, TMS): d=
2.62 ppm (d, 3J(P,H)=10 Hz); 13C NMR (100.6 MHz, CDCl3, 308C,
TMS): d=37.1 ppm (d, 2J(P,C)=4.7 Hz); 31P NMR (121.5 MHz, CDCl3,
308C): d=ꢀ34.8 (quint, 2J(P,P)=54,3 Hz, 1P), 6.3 ppm (d, 4P); IR
(KBr): n˜ =3086, 2992, 2882, 2798, 1482, 1457, 1394, 1288, 1190, 1090,
cis-3,5-Dimethylpiperidine: see the Supporting Information.
1,1,1,3,3,3-Hexakis[1-(cis-3,5-dimethylpiperidinyl)]-1l5,3l5-diphosphaze-
nium tetrafluoroborate (2d·BF4): A slurry of 7·PCl6 (21.76 mmol of crude
product[24]) in absolute chlorobenzene (20 mL) was prepared. At ꢀ408C,
cis-3,5-dimethylpiperidine (26.56 g, 0.237 mol) and NEt3 (22.01 g,
0.217 mol) were then successively added at such a rate that the tempera-
ture did not exceed ꢀ208C. The mixture was then slowly warmed to
reflux. After refluxing for 12 h the mixture was cooled to room tempera-
ture, and the solvent was removed in vacuo. A solution of NaBF4 (4.0 g,
36 mmol) in H2O (150 mL) was added, and the mixture was extracted
with CH2Cl2 (3”100 mL). The combined organic phases were concentrat-
ed in vacuo, and the residue was dried in high vacuum and recrystallized
from aqueous EtNH2 (ca. 0.5 L, 70%) to give colorless crystals (4.0 g,
33%). M.p. 2158C (decomp); 1H NMR (250 MHz, CDCl3, 308C, TMS):
d=0.75 (dt, 2J(4,4)=13.1 Hz, 3J(4,3/5)=11.8 Hz, 6H; 4-H), 0.90 (d, 3J(3/
5,CH3)=6.4 Hz, 36H; CH3), 1.52 (m, 12H; 3-,5-H), 1.88 (dt, 6H; 4-H),
2.15 (dd, 2J(2/6,2/6)=11.3 Hz, 3J(2/6,3/5)=12.2 Hz, 12H; 2-,6-H),
3.27 ppm (dd, 3J(2/6,3/5)=4.9 Hz, 12H; 2-,6-H); 13C NMR (100 MHz,
CDCl3, 308C, TMS): d=19.1 (CH3), 32.0 (d, 3J(2/6,3/5)=4.9 Hz, CH),
32.1 (CH), 41.9 (g-CH2), 52.5 ppm (a-CH2); 31P NMR (202 MHz, CDCl3,
308C, 85 % H3PO4): d=7.7 ppm (s); IR (KBr): n˜ =2948 (s, br), 2868 (s,
br), 1461 (m), 1390 (m, br) 1352 (s), 1290 (w), 1190 (s), 1164 (m), 1128 (s,
br), 1088 (m), 1051 (vs), 1037 (s, br), 952 (m), 929 (m), 851 (m), 800 (m),
747 cmꢀ1 (w); elemental analysis calcd (%) for C42H84N7BF4P2 (835.9): C
60.35, H 10.13, N 11.73; found: C 60.39, H 9.98, N 11.73.
1066, 1051, 996, 814, 734 cmꢀ1
; elemental analysis calcd (%) for
C24H72N16BF4P5 (826.5): C 34.87, H 8.78, N 27.11; found: C 35.00, H 8.76,
N 27.01.
Tetrakis[(tri-1-pyrrolidinylphosphoranyliden)amino]phosphonium tetra-
fluoroborate (4b·BF4): Compound 6b[11] (46.4 g, 182 mmol) was dissolved
in absolute chlorobenzene (40 mL) and cooled to ꢀ308C under N2. With
cooling in a dry-ice bath, PCl5 (4.24 g, 20 mmol) was added at such a rate
that the temperature did not exceed ꢀ108C. Then the mixture was al-
lowed to warm to room temperature until all PCl5 had dissolved. It was
then gradually heated to reflux, was held at reflux for 10.5 h, and was
cooled to room temperature. A solution of NH4BF4 (12.8 g, 122 mmol) in
H2O (100 mL) was added, the mixture was carefully shaken in a separat-
ing funnel, and the organic (lower) phase was separated. The aqueous
phase was extracted once with chlorobenzene (100 mL) and the com-
bined organic phases were washed once with H2O (100 mL), dried over
1,1,1,3,3,5,5,5-Octakis(dimethylamino)-1l5,3l5,5l5-triphosphazadienium
[11]
tetraphenylborate (3·BPh4): Salt 9·BF4 (9.7 g, 23.0 mmol) dissolved in
absolute chlorobenzene (10 mL) was added to a solution of 6a (10.2 g,
Chem. Eur. J. 2006, 12, 429 – 437
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
435

R. Schwesinger et al.
MgSO4, and concentrated in vacuo. The tan residue was dried in high
vacuum, was recrystallized from MeOH/H2O 7:1 (300 mL), and again
was dried in high vacuum to afford colorless crystals (18.6 g, 82%). M.p.
>2108C (decomp); 6b·HBF4 could be recovered almost quantitatively
from the mother liquor; 1H NMR (250 MHz, CDCl3, 308C, TMS): d=
1.75 (m, 48H; NCH2CH2), 3.14 ppm (m, 48H; NCH2CH2); 13C NMR
(100 MHz, CDCl3, 308C, TMS): d=26.4 (d, 3J(P,C)=9 Hz, NCH2CH2),
46.4 ppm (d, 2J(P,C)=6 Hz, NCH2CH2); 31P NMR (202 MHz, CDCl3,
308C, 85% H3PO4): d=ꢀ33.8 (quint, 2J(P,P)=51 Hz, 1P), 6.25 ppm (d,
4P); IR (KBr): n˜ =2956 (vs), 2860 (vs), 2660 (w), 2080 (w), 1480 (w),
1453 (m), 1355 (s), 1263 (vs, br), 1196 (s), 1124 (s), 1082 (vs), 1047 (vs),
1008 (vs), 909 (w), 867 (w), 803 (m), 760 (w), 721 cmꢀ1 (w); elemental
analysis calcd (%) for C48H96N16BF4P5 (1139.1): C 50.62, H 8.50, N 19.67;
found: C 50.46, H 8.53, N 19.56.
Acknowledgements
This workwas supported by the Deutsche Forschungsgemeinschaft.
[1] M. E. Halpern, Process Chemistry in the Pharmaceutical Industry
1999, pp. 283–298; M. Makosza, M. Fedorynski in Interfacial Cataly-
sis (Ed.: A. G. Volkov), Dekker, New York, Basel, 2003, pp. 159–
201; D. Albanese in Interfacial Catalysis (Ed.: A. G. Volkov),
Dekker, New York, Basel, 2003, pp. 203–226.
[2] D. Landini, A. Maia, J. Chem. Soc. Chem. Commun. 1984, 1041–
1042; D. Landini, A. Maia, A. Rampoldi, J. Org. Chem. 1986, 51,
5475–5476.
Stability test of phosphonium- and phosphazenium cations under phase-
transfer conditions: The corresponding tetrafluoroborate salt
(0.500 mmol) was dissolved in a minimum amount of MeOH, a solution
of KCl (45 mg, 0.600 mmol) in H2O (150 mL) was added with stirring, the
precipitate was filtered off, and the solution concentrated in vacuo, yield-
ing the crude chloride. Chlorobenzene (7 mL), H2O (3.5 mL), and NaOH
(3.5 g) were added and the mixture was heated to 1008C (if not otherwise
indicated) in a Teflon flaskwith stirring. Then both phases were diluted
by addition of chlorobenzene (20 mL) as well as H2O (20 mL) and sepa-
rated; the aqueous phase was extracted with chlorobenzene (2”30 mL)
and the combined organic phases were washed with brine (20 mL). The
combined organic phases were concentrated in vacuo, the residue was
dissolved in MeOH (25 mL), and NaBPh4 or NaBF4 (200 mg) in MeOH
(5 mL) was added. The colorless precipitates were filtered off, washed
with a small amount of MeOH, and dried in vacuo to afford the corre-
sponding salts. From the yield (assuming first-order kinetics with respect
to the cation) the half lives of the cations were calculated. In case of 4a+
the precipitate contained cation salts derived from decomposition prod-
[3] D. Landini, A. Maia, A. Rampoldi, J. Org. Chem. 1986, 51, 3187–
3191.
[4] E. V. Dehmlow, V. Knufinke, J. Chem. Res. Synop. 1989, 224–225.
[5] H. J.-M. Dou, R. Gallo, P. Hassanaly, J. Metzger, J. Org. Chem.
1977, 42, 4275–4276.
[6] I. E. Markó in Comprehensive Organic Synthesis, Vol. 3 (Eds.: B. M.
Trost, I. Fleming), Pergamon, Oxford, 1991, pp. 913–974; E. M.
Arnett, P. C. Wernett, J. Org. Chem. 1993, 58, 301–303; X.-M.
Zhang, F. G. Bordwell, M. Van Der Puy, H. E. Fried, J. Org. Chem.
1993, 58, 3060–3066; L. Vial, M.-H. GonÅalves, P.-Y. Morgantini, J.
Weber, G. Bernardinelli, J. Lacour, Synlett 2004, 1565–1568.
[7] J. G. Dawber, J. C. Tebby, A. A. C. Waite, J. Chem. Soc. Perkin
Trans. 2 1983, 1923–1925.
[8] G. W. Fenton, C. K. Ingold, J. Chem. Soc. 1929, 2342–2357.
[9] R. Schwesinger, H. Schlemper, Angew. Chem. 1987, 99, 1212–1214;
Angew. Chem. Int. Ed. Engl. 1987, 26, 1167–1169.
[10] R. Schwesinger, C. Hasenfratz, H. Schlemper, L. Walz, E.-M. Peters,
K. Peters and H. G. von Schnering, Angew. Chem. 1993, 105, 1420–
1422; Angew. Chem. Int. Ed. Engl. 1993, 32, 1361–1363.
[11] R. Schwesinger, H. Schlemper, C. Hasenfratz, J. Willaredt, T. Dam-
bacher, T. Breuer, C. Ottaway, M. Fletschinger, J. Boele, H. Fritz, D.
Putzas, H. W. Rotter, F. G. Bordwell, A. V. Satish, G.-Z. Ji, E.-M.
Peters, K. Peters, H. G. von Schnering, L. Walz, Liebigs Ann. 1996,
1055–1081.
1
ucts;[35] a H NMR analysis was performed to evaluate the amount of un-
decomposed 4a+.
1
Salt 1a·BF4: 26 mg, 88 mmol, 18% after 75 min; t = =20 min.
2
1
Salt 1b·BPh4: 243 mg, 387 mmol, 77% after 20 min; t = =54 min; m.p.
2
2138C; 1H NMR (250 MHz, CDCl3, 308C, TMS): d=1.88 (m, 16H;
NCH2CH2), 3.13 (m, 16H; NCH2CH2), 6.88 (m, 4H; p-Harom), 7.22 (m,
[12] A. P. Marchenko, G. N. Koidan, A. M. Pinchuk, Zh. Obshch. Khim.
1983, 53, 670–677; J. Gen. Chem. 1983, 53, 583–589.
8H; o-Harom), 7.45 ppm (m, 8H; m-Harom).
1
Salt 1e·BPh4: 561 mg, 603 mmol, 65% after 42.5 h; t = =67 h, m.p. 2308C;
2
[13] E. V. Dehmlow, U. Fastabend, Gazz. Chim. Ital. 1996, 126, 53–55;
T. Nobori, T. Suzuki, S. Kiyono, M. Kouno, K. Mizutani, Y. Sonobe,
U. Takaki (Mitsui Toatsu Chemicals, Inc., Japan), EP 791600 A1,
1997 [Chem. Abstr. 1997, 127, 234743]; T. Nobori, T. Hayashi, S.
Kiyono, U. Takaki (Mitsui Chemicals, Inc., Japan), EP 879838 A2,
1998 [Chem. Abstr. 1999, 130, 38836]; M. Isobe, K. Ohkubo, S.
Sakai, U. Takaki, T. Nobori, T. Izukawa, S. Yamasaki (Mitsui Toatsu
Chemicals, Inc., Japan), EP 897940 A2, 1999 [Chem. Abstr. 1999,
130, 197636]; S. Yamasaki, I. Hara, S. Tamura, F. Yamazaki, H. Wa-
tanabe, M. Matsufuji, S. Matsumoto, A. Nishikawa, T. Izukawa, M.
Aoki, T. Nobori, U. Takaki (Mitsui Chemicals, Inc., Japan), EP
916686 A1, 1999 [Chem. Abstr. 1999, 130, 52838]; P. C. Hupfield,
R. G. Taylor, J. Inorg. Organomet. Polym. 1999, 9, 17–34; P. Hup-
field, A. Surgenor, R. Taylor (Dow Corning Corporation, USA), EP
1008610 A2, 2000 [Chem. Abstr. 2000, 133, 31350]; G. Moloney, P.
Hupfield, A. Surgenor, R. Taylor (Dow Corning Corporation,
USA), EP 1008612 A2, 1999 [Chem. Abstr. 2000, 133, 31352]; M.
Isobe, K. Ohkubo, S. Sakai (Mitsui Toatsu Chemicals, Inc., Japan),
EP 1028133 A1, 2000 [Chem. Abstr. 2000, 133, 164974]; D. Baskaran,
A. H. E. Müller, Macromol. Rapid Commun. 2000, 21, 390–395; S.
Yamasaki, Y. Hara, T. Kunihiro, F. Yamazaki, M. Matsufuji, A.
Nishikawa, S. Matsumoto, T. Izukawa, M. Isobe, K. Ohkubo, K.
Ueno (Mitsui Toatsu Chemicals, Inc., Japan), EP 104100 A1, 2000
[Chem. Abstr. 2000, 132, 308867]; S. Ota, S. Moriya, R. Mori, T.
Koda, J. Tan, S. Kojoh, H. Kaneko, S. Hama, T. Nobori, T. Matsugi,
N. Kashiwa (Mitsui Chemicals, Inc., Japan), EP 1275670 A1, 2001
[Chem. Abstr. 2001, 135, 137856]; A. Grzelka, J. Chojnowski, M.
Cypryk, W. Fortuniak, P. C. Hupfield, R. G. Taylor, J. Organomet.
Chem. 2002, 660, 14–26; A. Grzelka, J. Chojnowski, W. Fortuniak,
1H NMR (250 MHz, CDCl3, 308C, TMS): d=1.00–1.95 (m, 40H; CH2),
2.50 (d, 3J(P,H)=10 Hz, 12H; CH3), 2.92 (m, 4H; CH), 6.80–7.08 (m,
12H; Harom), 7.25–7.42 ppm (m, 8H; Harom); 13C NMR (100 MHz, CDCl3,
308C, TMS): d=25.1 (s, CH2), 26.1 (s, CH2), 29.9 (d, 2J(P,C)=3.2 Hz,
2
CH), 30.5 (s, CH2), 55.8 (d, J(P,C)=4.7 Hz, CH3), 116.8, 121.8, 125.6 (2J-
(B,C)=2.6 Hz), 136.2 ppm; elemental analysis calcd (%) for C52H76N4BP
(799.0): C 78.17, H 9.59, N 7.01; found: C 78.15, H 9.61, N 7.07.
1
Salt 1 f·BPh4: 539 mg, 1327 mmol, 85% after 1.5 h; t = =6 h; m.p. 2348C
2
(decomp); 1H NMR (250 MHz, CDCl3, 308C, TMS): d=1.10 (d, 3J=
3
8 Hz, 24H; CCH3), 2.35 (d, J(P,H)=10 Hz, 12H; NCH3), 3.30 (sept, 4H;
CH), 6.90 (m, 4H; Harom), 7.05 (m, 8H; Harom), 7.42 ppm (m, 8H; Harom);
elemental analysis calcd (%) for C40H60N4BP (638.7): C 75.22, H 9.47, N
8.77; found: C 75.28, H 9.49, N 8.85.
1
Salt 2a·BF4: 130 mg, 304 mmol, 61% after 6 h; t = =8 h.
2
1
Salt 2b·BF4: 239 mg, 410 mmol, 82% after 6 h; t = =21 h.
2
1
Salt 2c·BF4: 265 mg, 265 mmol, 53% after 6 h; t = =7 h.
2
1
Salt 2d·BF4: 253 mg, 301 mmol, 60% after 6 h; t = =8 h.
2
1
Salt 4a·BPh4: 29.2 mg, 28.9 mmol, 2.2% after 184 h at 1108C; t = =33 h.
2
1
Salt 4b·BPh4: 524 mg, 460 mmol, 91% after 65 h at 1108C, t = =477 h;
2
m.p. 2488C (decomp); 1H NMR (250 MHz, CDCl3, 308C, TMS): d=1.74
(m, 48H; NCH2CH2), 3.13 (m, 48H; NCH2CH2), 6.90 (m, 4H; p-Harom),
7.07 (m, 8H; m-Harom), 7.44 ppm (m, 8H; o-Harom); for the analysis of the
decomposition products, the mother liquor was concentrated in vacuo
and the residue checked by NMR spectroscopy: 1H NMR (250 MHz,
CDCl3, 308C, TMS): d=1.75 (m, integr. 70 mm), 3.03 (m, 22 mm), 3.15
(m, 34 mm) 6.78–7.02 (m, 10.5 mm), 7.08 (m, 15 mm), 7.30–7.50 (m,
19 mm), 7.62 ppm (m, 2 mm).
436
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Chem. Eur. J. 2006, 12, 429 – 437

Phosphazenium Cations
FULL PAPER
R. G. Taylor, P. C. Hupfield, J. Inorg. Organomet. Polym. 2004, 14,
85–99.
[14] T. Nobori, S. Fujiyoshi, I. Hara, T. Hayashi, A. Shibahara, K.
Funaki, K. Mizutani, S. Kiyono (Mitsui Chemicals, Inc., Japan), EP
1275630 A1, 2001 [Chem. Abstr. 2001, 135, 344378].
Phosphorus Sulfur Silicon Relat. Elem. 1993, 78, 37–46; b) V. G.
Kostina, E. K. Rutkovskii, N. G. Feshchenko, Zh. Obshch. Khim.
1987, 57, 1072–1077; J. Gen. Chem. 1987, 57, 955–960.
[32] The quality of the X-ray structure of 1e·O3SC4F9 was not sufficient
to justify a presentation within this paper: M. Keller, University of
Freiburg, unpublished results.
[33] K. M. Harmon, I. Gennick, S. L. Madeira, J. Phys. Chem. 1974, 78,
2585–2591; A.-R. Mahjoub, X. Zhang, K. Seppelt, Chem. Eur. J.
1995, 1, 261–265; R. Goddard, H. M. Herzog, M. T. Reetz, Tetrahe-
dron 2002, 58, 7847–7850, and references therein.
[15] The phosphazenium salts 2a·BF4 and 4a·Cl are commercially avail-
able.[22,23]
[16] A. P. Marchenko, G. N. Koidan, A. M. Pinchuk, Zh. Obshch. Khim.
1984, 54, 2691–2696; J. Gen. Chem. 1984, 54, 2405–2409.
[17] H. G. Ang, G. Manoussakis, Y. O. El Nigumi, J. Inorg. Nucl. Chem.
1968, 30, 1715–1717; Y. O. El Nigumi, H. J. EmelØus, J. Inorg. Nucl.
Chem. 1970, 32, 3211–3212; K. Issleib, M. Lischewski, Synth. React.
Inorg. Met.-Org. Chem. 1973, 3, 255–266.
[18] G. N. Koidan, A. P. Marchenko, A. A. Kudryavtsev, A. M. Pinchuk,
Zh. Obshch. Khim. 1982, 52, 2001–2011; J. Gen. Chem. 1982, 52,
1779–1787.
[19] R. Schwesinger, J. Willaredt, H. Schlemper, M. Keller, D. Schmitt,
H. Fritz, Chem. Ber. 1994, 127, 2435–2454.
[20] A. P. Marchenko, S. I. Shaposhnikov, G. N. Koidan, A. V. Kharchen-
ko, A. M. Pinchuk, Zh. Obshch. Khim. 1988, 58, 2230–2237; J. Gen.
Chem. 1988, 58, 1985–1992.
[21] H. Nçth, H. J. Vetter, Chem. Ber. 1965, 98, 1981–1987; B. Castro, J.-
R. Dormoy, B. Dourtoglou, G. Evin, C. Selve, J.-C. Ziegler, Synthesis
1976, 751–752; J.-R. Dormoy, B. Castro, Tetrahedron Lett. 1979, 20,
3321–3322.
[22] Commercially available from Aldrich Chemical Company.
[23] Commercially available from Fluka Chemie AG (Switzerland).
[24] R. Link, R. Schwesinger, Angew. Chem. 1992, 104, 864; Angew.
Chem. Int. Ed. Engl. 1992, 31, 850.
[25] R. Schwesinger, R. Link. G. Thiele, H. Rotter, D. Honert, H.-H.
Limbach, F. Männle, Angew. Chem. 1991, 103, 1376–1378; Angew.
Chem. Int. Ed. Engl. 1991, 30, 1372–1375.
[26] M. Becke-Goehring, W. Lehr, Chem. Ber. 1961, 94, 1591–1594.
[27] L. Seglin, M. R. Lutz, H. Stange (FMC Corporation, US), US
3231327, 1966 [Chem. Abstr. 1966, 64, 58007]; D. Bougeard, C. BrØ-
mard, R. de Jaeger, Y. Lemmouchi, Phosphorus Sulfur Silicon Relat.
Elem. 1993, 79, 147–159.
[34] E. V. Dehmlow, S. Schrader, Z. Naturforsch. B 1990, 45, 409–412;
E. V. Dehmlow, G. O. Torossian, Z. Naturforsch. B 1990, 45, 1091–
1092; E. V. Dehmlow, J. Wilkenloh, Liebigs Ann. Chem. 1990, 125–
128; E. V. Dehmlow, R. Richter, Chem. Ber. 1993, 126, 2765–2766;
E. V. Dehmlow, U. Fastabend, J. Chem. Soc. Chem. Commun. 1993,
1241–1242; E. V. Dehmlow, R. Richter, A. B. Zhivich, J. Chem. Res.
Synop. 1993, 504–505; E. V. Dehmlow, R. Klauck, J. Chem. Res.
Synop. 1994, 448–449; E. V. Dehmlow, J. Kinnius, J. Prakt. Chem.
1995, 337, 153–155; S. Schrader, E. V. Dehmlow, Org. Prep. Proced.
Int. 1996, 28, 634–637; M. Fischer (BASF Aktiengesellschaft, Lud-
wigshafen), EP 0691334 A1, 1996 [Chem. Abstr. 1996, 124, 264009];
M. Missfeldt, J. Willsau, R. Büscher, P. Bell, H.-U. Borst (Agfa-Ge-
vaert AG, Germany), EP 0762202 A1, 1997 [Chem. Abstr. 1997, 126,
257014]; H. Jin Lee, U. Sun Kong, D. Kwon Lee, J. Ho Shin, H.
Nam, G. Sig Cha, Anal. Chem. 1998, 70, 3377–3383; M. Hwan Kim,
K. Moon Lee, H. Joon Oh, H. Choll Cho, D. Hoe Cho, H. Nam, G.
Sig Cha, K.-J. Paeng, Anal. Sci. 2001, 17, 995–997; E. V. Dehmlow,
M. Kaiser, J. Bollhçfer, New J. Chem. 2001, 25, 588–590; W. Klein,
M. Jansen, Z. Naturforsch. B 2001, 56, 287–292; N. Okawa (Dow
Corning Toray Silicone Co. Ltd., Japan), JP 2003073476 A2, 2003
[Chem. Abstr. 2003, 138, 222300]; T. Okawa (Dow Corning Toray
Silicone Co. Ltd., Japan), JP 2003252996 A2, 2003 [Chem. Abstr.
2003, 139, 231135]; S. Funaki, Y. Taniguchi, T. Nobori, Y. Yamamo-
to, I. Hara, T. Hayashi, K. Mizutani, S. Kiyono, EP 1486479 A1,
2004 [Chem. Abstr. 2004, 142, 55652].
[35] Succeeding paper.
[36] A. Altonare, M. C. Burla, M. Carnalli, G. Gascarano, C. Giacovazzo,
A. Guagliardi, A. G. G. Moliterni, G. Polidori, R. Spagan, J. Appl.
Crystallogr. 1999, 32, 115–122.
[28] E. Fluck, E. Schmid, W. Haubold, Z. Anorg. Allg. Chem. 1977, 433,
229–236.
[29] H. Wieland, A. Hçchtlein, Justus Liebigs Ann. Chem. 1933, 505,
237–247.
[37] G. Sheldrick, SHELXL-97, Program for Crystal Structure Refine-
ment, University of Gçttingen, Gçttingen (Germany).
[30] The chloride salt 1b·Cl has already been described: B. Schiemenz,
T. Wessel, R. Pfirmann, A. Beck, W. Hahn, (Clariant GmbH, Ger-
many), EP 11070724, 2001 [Chem. Abstr. 2001, 134, 101014].
[31] a) No spectroscopic data have been reported for the compound:
T. B. Cameron, H. N. Hanson, G. F. de la Fuente, J. E. Huheey,
Received: May 2, 2005
Revised: July 18, 2005
Published online: September 28, 2005
Chem. Eur. J. 2006, 12, 429 – 437
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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