Phosphenium-insertion and chloronium-addition reactions involving the cyclo-phosphanes (t-BuP)n (n≤3, 4)

Article abstract of DOI:10.1071/CH13141

The transfer of a Ph2P+-moiety provided by Ph2PCl and chloronium-addition with PCl5 or PhICl2 to the cyclo-phosphanes (t-BuP)n (n≤3 (4), 4 (5)) were investigated. The reactions strongly depend on the presence of GaCl3 or Me3SiOTf as a halide abstracting reagent. The reaction of 4 with Ph2PCl and GaCl3 quantitatively yields cation [Ph2P(t-BuP)3]+ (6+) as a GaCl4 - salt. Using Me3SiOTf as a halide abstracting reagent leads to the ring expansion of (t-BuP)3 (4) to tetrameric (t-BuP)4 (5) and cation 6+ is only formed as a minor product. Chloronium addition employing the PCl5/GaCl3 or PhICl2/Me3SiOTf systems as Cl+-sources to 4 gives complex reaction mixtures. In contrast, the Cl+-addition to 5 gives cation [Cl(t-BuP)4]+ (8+) quantitatively when the system PCl5/GaCl3 is used. Utilising PhICl2 in the presence of Me3SiOTf gives t-BuPCl2 as the main product.

Full text of DOI:10.1071/CH13141

RESEARCH FRONT
CSIRO PUBLISHING
Aust. J. Chem. 2013, 66, 1155–1162
Full Paper
http://dx.doi.org/10.1071/CH13141
Phosphenium-Insertion and Chloronium-Addition
Reactions Involving the cyclo-Phosphanes
(t-BuP)n (n 5 3, 4)
A
B C
,
B C D
, ,
Michael H. Holthausen, Dane Knackstedt,
and Jan J. Weigand
Neil Burford,
A D
,
A
Department of Chemistry and Food Chemistry, TU Dresden, Mommsenstr. 4, 01062
Dresden, Germany.
B
Department of Chemistry, University of Victoria, PO Box 3065, Stn. CSC, Victoria,
British Columbia, V8W 3V6, Canada.
C
Department of Chemistry, Dalhousie University, Halifax, Nova Scotia
B3H 4J3, Canada.
D
Corresponding authors. Email: nburford@uvic.ca; jan.weigand@tu-dresden.de
The transfer of a Ph2Pþ-moiety provided by Ph2PCl and chloronium-addition with PCl5 or PhICl2 to the cyclo-phosphanes
(t-BuP)n (n ¼ 3 (4), 4 (5)) were investigated. The reactions strongly depend on the presence of GaCl3 or Me3SiOTf as a
halide abstracting reagent. The reaction of 4 with Ph2PCl and GaCl3 quantitatively yields cation [Ph2P(t-BuP)3]þ (6þ) as a
GaClꢀ4 -salt. Using Me3SiOTf as a halide abstracting reagent leads to the ring expansion of (t-BuP)3 (4) to tetrameric
(t-BuP)4 (5) and cation 6þ is only formed as a minor product. Chloronium addition employing the PCl5/GaCl3 or PhICl2/
Me3SiOTf systems as Clþ-sources to 4 gives complex reaction mixtures. In contrast, the Clþ-addition to 5 gives cation
[Cl(t-BuP)4]þ (8þ) quantitatively when the system PCl5/GaCl3 is used. Utilising PhICl2 in the presence of Me3SiOTf gives
t-BuPCl2 as the main product.
Manuscript received: 29 March 2013.
Manuscript accepted: 7 May 2013.
Published online: 31 May 2013.
Introduction
ꢀ
ꢀ
(a)
(b)
The systematic development of polyphosphorus cations is of
considerable current interest in fundamental phosphorus chem-
istry.[1] Polyphosphorus cations feature structures based on cage-
like,[2] cyclo-[3] or catena-phosphanylphosphonium[4] motifs.
Salts of cyclo-phosphanylphosphonium ions are still rare and,
therefore, novelsynthetic procedures are desirable toexpeditethe
development of the chemistry of this class of compounds.
A variety of methods for their systematic synthesis are in place
in which the most common procedures employ alkylation[3] or
protonation[3d] protocols of cyclo-polyphosphanes. Insertion
reactions of phosphenium ions into cyclo-polyphosphanes are
also known and proceed either via a ring-expansion[5,3b,3c] or a
redistribution process.[6,3c] Reductive coupling reactions are also
reported in which the utilisation of chloro-substituted phospha-
nylphosphonium ions,[7] PCl3,[8] or secondary phosphanes[9]
render versatile approaches for the generation of cyclic poly-
phosphorus cations. Only recently, halonium addition reactions
to cyclo-polyphosphanes such as (CyP)4 (1) were reported which
offer a versatile approach to halogen-substituted, cyclo-poly-
phosphorus cations.[10] This was demonstrated by the reaction of
1 with PCl5 as a chloronium ion source and GaCl3 as a chloride
abstracting reagent in various stoichiometries. This allowed for
the stepwise preparation and isolation of cations 2þ and 32þ
as metallate salts (Scheme 1).[10]
ꢀ
2
1
3
Scheme 1. Stepwise chloronium addition to (CyP)4: (a) þ[PCl4][GaCl4],
ꢀPCl3, CH2Cl2, ambient temperature, 2[GaCl4]: 60%; (b) þ2 [PCl4][GaCl4],
þ2 GaCl3, ꢀ2 PCl3, CH2Cl2, ambient temperature, 3[Ga2Cl7]2: 90%.
t-Bu
t-Bu
P
P
t-Bu
t-Bu
P
P
P
P
P
t-Bu
t-Bu
t-Bu
4
5
Fig. 1. cyclo-Tri- and tetraphosphane (t-BuP)n (n ¼ 3 (4) or 4 (5)).
Inthis contribution wereporton the transfer ofaPh2Pþ-moiety
to 4 via the reaction with Ph2PCl and GaCl3 or Me3SiOTf.
The outcome of the reaction strongly depends on the
employed halide abstracting reagent. In the same context, chlor-
onium addition reactions to (t-BuP)n (n ¼ 3 (4), 4 (5), Fig. 1)
Journal compilation Ó CSIRO 2013
www.publish.csiro.au/journals/ajc

1156
M. H. Holthausen et al.
utilising the PCl5/GaCl3 or PhICl2/Me3SiOTf system as Clþ
source were investigated indicating, in part, complex reactions.
Furthermore, in the course of our investigations we developed a
protocol for the smooth conversion of the cyclo-polyphosphane
(t-BuP)3 (4) to (t-BuP)4 (5) which is induced by Me3SiOTf.
crystal structure determination were obtained by diffusion of
n-hexane into concentrated C6H5F solutions of the salts at ꢀ308C.
Table 2 shows crystallographic data and details of the structure
refinement. Theobservedbondlengthsandanglesofthecationsof
both salts are almost equal, thus, only the structural parameters of
cation 6þ in 6[GaCl4] are discussed (Fig. 3).
Results and Discussion
The bond distances and angles are typical for catena-
phosphorus moieties and range from 2.1951(5) to 2.2352
˚
(5) A.
The slow addition of Ph2PCl to a C6H5F solution of 4 and GaCl3
yielded a yellow solution which was investigated by means of
31P{1H} NMR spectroscopy (Fig. 2a). The spectrum shows
only the resonances of an AM2X spin system with the relative
intensities of 1 : 2 : 1 indicating the quantitative formation of
the CS-symmetric cyclo-triphosphanylphosphonium ion 6þ. The
31P{1H} NMR spectroscopic parameters of 6þ are summarised in
Table 1. The addition of n-hexane to the reaction mixture leads to
the precipitation of yellow, microcrystalline 6[GaCl4] which is
conveniently isolated by filtration. Performing the same reaction,
but using Me3SiOTf instead of GaCl3 as the chloride abstracting
agent, gives cation 6þ only in a moderate yield of 35% (Fig. 2b).
The spectrum indicates complete consumption of 4 (absence of
the AX2 spin system; d(PA) ¼ ꢀ108.4ppm, d(PX) ¼ ꢀ70.0ppm,
1JAX ¼ ꢀ201.5 Hz)[11] and two signals in addition to the reso-
nancesofthe AM2Xspin system ofcation 6þ areobserved. One of
the prominent resonances is assigned to unreacted Ph2PCl (d(P) ¼
82.0ppm) and is not displayed in Fig. 1. The singlet resonance at
high field (d(P) ¼ ꢀ57.8 ppm) is assigned to tetrameric (t-BuP)4
(5).[12] The AM2X spin system of cation 6þ is consistent with a
molecular arrangement in which the [Ph2P]þ-moiety is located
between both P atoms substituted with t-Bu-groups in a cis-
arrangement.[3b] The X part of the AM2X spin system is assigned
to the tetra-coordinated P atom by comparison to related deriva-
tives (Table 1; compare [Ph6P5][OTf]: d(PX) ¼ 22ppm).[3c] The
A and M2 parts are assigned to the tri-coordinated P atoms.[3b–3d]
Single crystals of 6[GaCl4] and 6[OTf] suitable for X-ray single
[3,5]
Cation 6þ shows a less puckered four-membered
ring (average P–P–P–P torsion angle: t ¼ 33.0(1)8) compared
with 5 (t ¼ 24.5(1)8).[13] Commonly, cyclo-tetraphosphanes
exhibit an enhanced puckering in order to minimise steric
interactions between substituents on non-adjacent phosphorus
atoms. In contrast, cyclo-triphosphanylphosphonium ions are
less puckered to minimise steric repulsion between the
substituents at the tetra-coordinated P atom and both adjacent
P atoms.[3b]
The formation of (t-BuP)4 (5) in the reaction of 4, PhPCl2, and
Me3SiOTf is unexpected. It is known that cyclo-polyphosphanes
can undergo ring-inversion reactions in protic solvents to give
thermodynamically more favoured ring-sizes.[14] However,
Table 1. 31P{1H} NMR parameters of 6[GaCl4], 6[OTf], 8[GaCl4],
and 8[OTf]
Spin system
6[GaCl4]
6[OTf]
8[GaCl4]
8[OTf]
AM2X
AM2X
AM2X
AM2X
d(PA)
d(PM)
ꢀ22.2
ꢀ12.4
10.9
ꢀ23.0
ꢀ13.0
10.5
ꢀ40.9
ꢀ11.3
99.4
ꢀ42.6
ꢀ11.1
98.4
d(PX)
1J(PAPM)
1J(PMPX)
2J(PAPX)
ꢀ141.9
ꢀ277.3
ꢀ22.3
ꢀ141.7
ꢀ276.0
ꢀ22.4
ꢀ158.6
ꢀ330.7
8.2
ꢀ158.0
ꢀ329.5
7.0
[GaCl4]
[OTf]
(a)
(b)
t-Bu
t-Bu
ꢀ
Ph
P
Ph
Ph
P
ꢀ
Ph
X
P
X
P
C6H5F
C6H5F
P
P
ꢀ Ph2PCl ꢀ GaCl3
t-Bu
t-Bu
P
t-Bu
ꢀ Ph2PCl ꢀ Me3SiOTf
t-Bu
P
M
ꢀ
5
M
P
P
P
P
ꢁMe3SiCl
PA
PA
t-Bu
t-Bu
t-Bu
t-Bu
t-Bu
t-Bu
[OTf]
(yield: 35 %)
4
6
[GaCl4]
6
4
(yield ꢂ98 %)
M
X
M
A
5
X
A
∗
∗
∗
25.0
0
ꢁ25.0
ꢁ50.0 [ppm]
25.0
0
ꢁ25.0
ꢁ50.0
[ppm]
Fig. 2. 31P{1H} NMR spectra of the reaction mixtures of (t-BuP)3 and Ph2PCl with (a) GaCl3 or (b) Me3SiOTf in 1 : 1 : 1 stoichiometry (C6H5F, [D6]benzene
capillary, 258C); experimental (upwards) and fitted (downwards) AM2X spin system of 6[GaCl4] and 6[OTf]; the reaction equation in (b) is not balanced;
unidentified side products are marked with asterisks.

Phosphorus Chemistry
1157
Table 2. Summary of the crystallographic data of 6[GaCl4], 6[OTf], 9[GaCl4], and 8[GaCl4]
6[GaCl4]
6[OTf]
9[GaCl4]
8[GaCl4]
Formula
Mr [g molꢀ1
C24H37Cl4GaP4
660.94
C25H37F3O3P4S
598.49
C16H37Cl4GaP4
564.86
C16H36Cl5GaP4
599.30
]
Dimension [mm3]
0.12 ꢁ 0.10 ꢁ 0.08
Colourless, block
Triclinic
P-1
0.15 ꢁ 0.12 ꢁ 0.05
Colourless, block
Monoclinic
P21/n
0.16 ꢁ 0.06 ꢁ 0.04
Colourless, rod
Orthorhombic
Pnma
0.09 ꢁ 0.05 ꢁ 0.04
Yellow, irregular
Tetragonal
I-4
Colour, habit
Crystal system
Space group
˚
a [A]
˚
b [A]
˚
c [A]
9.6669(7)
12.0355(9)
14.402(1)
81.777(1)
71.486(1)
86.940(1)
1572.5(2)
2
12.3446(5)
18.2397(8)
13.7307(6)
90
17.0102(7)
11.1070(5)
14.7582(6)
90
12.9276(2)
12.9276(2)
8.2956(2)
90
a [8]
b [8]
g [8]
104.233(1)
90
90
90
90
90
3
˚
V [A ]
2996.7(2)
4
2788.3(2)
4
1386.38(5)
2
Z
T [K]
rc [g cmꢀ3
F(000)
153(1)
153(2)
153(2)
153(2)
]
1.396
1.327
1.346
1.436
680
1256
1168
616
˚
l, A
0.71073 (MoKa)
1.431
0.71073 (MoKa)
0.365
1.54178 (CuKa)
7.048
1.54178 (CuKa)
7.988
m [mmꢀ1
]
Absorption correction
Reflections collected
Reflections unique
Rint
SADABS
17567
SADABS
30143
SADABS
15358
SADABS
3854
8428
7130
2687
1231
0.0201
0.0189
0.0619
0.0377
Reflection obs. [F .3s(F)]
7277
6366
2311
1209
ꢀ3
˚
Residual density [e A
]
0.651, ꢀ0.437
307
0.588, ꢀ0.432
398
0.704, ꢀ0.408
146
0.266, ꢀ0.279
69
Parameters
GOOF
1.042
1.037
1.070
1.055
R1 [I .3s(I)]
wR2 (all data)
CCDC number
0.0293
0.0336
0.0427
0.0288
0.0787
0.0937
0.1177
0.0727
931466
931567
931569
931568
ratio without the addition of Ph2PCl. The reaction was monitored
by 31P{1H} NMR spectroscopy and the obtained spectra indicate
that Me3SiOTf indeed promotes the reaction (Fig. 4).
The conversion is completed after 72h. We speculate that the
first step in the reaction is the formation of a complex between
4 and Me3Siþ. The resulting cation may then dissociate to give
t-BuP¼Pt-Bu (which dimerises to 5) and the phosphenium cation
t-BuPSiMeþ3 (which can insert into another molecule of 4),
followed by release of Me3Siþ. The conversion is significantly
accelerated and completed within six hours if Me3SiOTf is
present in ,10mol-%. We suggest that in the 1 :1 reaction
(t-BuP)3 is completely consumed in adduct formation with
Me3SiOTf. Thus, it is proposed that free (t-BuP)3 is also
involved in the conversion of 4 to 5. Variable temperature
investigations are restricted due to the rather high melting point
of C6H5F (Mp ꢀ428C). Analytically pure 5 can be obtained
quantitatively by removing all volatiles under vacuum from the
reaction mixture. This method is interesting from a synthetic
point of view since it allows for a convenient preparation of 5.
Typically, a mixture of 4 and 5 is observed following standard
synthetic routes which requires tedious and low-yielding
separation procedures.[11]
C7
C21
C13
P3
P1
P4
P2
C1
C17
Fig. 3. Molecular structure of cation 6þ in 6[GaCl4] (hydrogen atoms are
omitted for clarity and thermal ellipsoids are displayed at 50 % probability).
˚
Selected bond lengths [A] and angles [8]: P1–P2 2.1998(5), P2–P3 2.2350
(5), P3–P4 2.2352(5), P4–P1 2.1951(5), P1–C1 1.801(2), P1–C7 1.806(2),
P2–C13 1.899(2), P3–C17 1.885(2), P4–C21 1.899(2); P1–P2–P3 83.17(2),
P2–P3–P4 85.80(2), P3–P4–P1 83.27(2), P2–P1–C1 111.00(5), P2–P1–C7
119.13(5), P1–P2–C13 112.49(5), P2–P3–C17 104.08(6), P3–P4–C21
110.20(5), C1–P1–C7 108.43(7).
The chloronium addition to 4 was investigated utilising
[PCl4][GaCl4] as a chloronium ion source.[10] Thus, a suspen-
sion of [PCl4][GaCl4] in C6H5F was added to a solution of 4 in
C6H5F according to Scheme 2.
4 dissolved in C6H5F is stable for at least three weeks without any
evidence of ring-interconversion to 5. Since this conversion
process is not observed in the reaction involving GaCl3, we
investigated the reaction of 4 and Me3SiOTf in C6H5F in a 1 : 1
The colour of the reaction mixture turned immediately
orange and the formation of a large amount of orange precipitate
of unknown constitution was observed. The supernatant solution
was investigated by means of 31P{1H} NMR spectroscopy.

1158
M. H. Holthausen et al.
t-Bu
5
t-Bu
P
A
t-Bu
P
P
t-Bu
P
P
P
P
t-Bu
X
t-Bu
t-Bu
5
4
72 h
X
A
36 h
12 h
1 h
[ppm]
ꢁ120.0
ꢁ60.0
ꢁ80.0
ꢁ100.0
Fig. 4. 31P{1H} NMR spectra of the reaction of 4 and Me3SiOTf in a 1 : 1 stoichiometry over the course of 72 h
(C6H5F, [D6]benzene capillary, 258C).
ꢀ
ꢀ
ꢀ
ꢀ
(a)
ꢀ
ꢀ
ꢀ
ꢀ
8ꢀ
9ꢀ
4
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢁ
ꢀ
“t-BuPꢃPt-Bu”
ꢁ
ꢀ
7ꢀ
5
Scheme 2. Reaction of 4 and [PCl4][GaCl4] (black): (a) þ[PCl4][GaCl4], ꢀPCl3, C6H5F, ambient tempera-
ture. A proposed reaction sequence for the formation of the observed product mixture (grey); the equation
depicts the major products and is not balanced; anions of the products are not depicted as the products were only
observed in solution.
The obtained spectrum indicates a complex product mixture by
the observation of a large series of multiplet resonances of low
intensities and three prominent singlet resonances. The singlet
resonance at lowest field is assigned to PCl3 (d(P) ¼ 220 ppm)
indicating a successful Clþ transfer from PClþ4 . The remaining
singlet resonances are assigned to t-BuPCl2 (d(P) ¼ 192 ppm)
and the phosphonium ion t-Bu2PClþ2 (d(P) ¼ 158 ppm).[15]
The formation of t-BuPCl2 can be rationalised by the interme-
diate formation of 7þ formed via chloronium addition to 4
(Scheme 2). However, 7þ decomposes via nucleophilic attack
of Clꢀ. This leads to the formation of t-BuPCl2 and formally
disphosphene t-BuP¼Pt-Bu which dimerises to tetraphosphane
5. The formation of t-Bu2PClþ2 was previously observed in the
reaction of t-BuPCl2 and AlCl3.[15] Accordingly, it is assumed
that t-Bu2PClþ2 forms via a GaCl3-mediated transfer of a t-Bu-
group. The intermediary formed 2-methylpropan-2-ylium ion is
assumed to act also as a proton source by expelling
2-methylprop-1-ene.[16] The proton is sequestered by the
formed tetraphosphane 5 giving the corresponding cation 9þ.
This species was identified in the reaction mixture in small
amounts by its characteristic AM2X spin system in the proton
decoupled 31P NMR spectrum.[3d] In addition, cation 9þ
crystallised as the GaClꢀ4 -salt by layering the reaction mixture
with n-hexane (ꢀ328C) after four days. Cation 9þ shows
similar bond lengths and angles as observed for the correspond-
ing triflate salt 9[OTf][3d] and Table 2 shows crystallographic
data and details of the structure refinement. The in situ formed
tetraphosphane 5 reacts with PClþ4 via a chloronium transfer to
cation 8þ and PCl3. A small amount of 8þ was confirmed in
the reaction mixture by the observation of its characteristic
AM2X spin system (Table 1). Analytically pure 8[GaCl4] can
be obtained via the direct chloronium addition to 5 (see below).
Mixtures of PhICl2 and Me3SiOTf were previously
employed as versatile reagents for chloronium addition reac-
tions.[10] Thus, 4 was also reacted with PhICl2 and Me3SiOTf in
a 1 : 1 : 1 stoichiometry in C6H5F (Fig. 5). The 31P{1H} NMR
spectrum of the reaction mixture shows resonances associated
with the formation of mainly 5 together with t-BuPCl2.
Tetraphosphane 5 forms according to the Me3SiOTf-induced
ring conversion reaction (see above). t-BuPCl2 is obtained by

Phosphorus Chemistry
1159
t-Bu
t-Bu
P
P
C6H5F
t-Bu ꢀ t-BuPCl2
t-Bu
P
ꢀ
PhlCl2
ꢀ
Me3SiOTf
P
P
P
(ꢂ90 %)
P
t-Bu
t-Bu
t-Bu
4
5
Cl
P
ꢀ
t-Bu
H
ꢀ
P
C6H5F
ꢀ
ꢀ
t-Bu
t-Bu
(CH3)2CCH2
P
P
t-Bu
t-Bu
P
P
(ꢄ10 %)
P
P
t-Bu
t-Bu
10
9ꢀ
t-BuPCl2
5
10
10
9ꢀ
10
200.0
150.0
100.0
50.0
0
ꢁ50.0 [ppm]
Fig. 5. 31P{1H} NMR spectra of the reaction mixtures of (t-BuP)3, PhICl2, and Me3SiOTf in 1 : 1 : 1 stoichiometry
(C6H5F, [D6]benzene capillary, 258C); the equation is not balanced and anions of the products are not depicted as the
products were only observed in solution.
(a)
(b)
t-Bu
t-Bu
[OTf]
[GaCl4]
t-Bu
t-Bu
Cl
ꢀ
Cl
P X
ꢀ
P
P
X
C6H5F
P
C6H5F
t-Bu
t-Bu
P
t-Bu
ꢀ
PCl5
GaCl
t-Bu
t-Bu ꢀ PhlCl2 ꢀ Me3SiOTf
P
ꢀ
t-Bu
t-Bu
P
P
P
t-Bu
P
P
P
5
3
M
M
ꢁMe3SiCl
P
P
PA
t-Bu
[GaCl4]
PA
t-Bu
[OTf]
(quant.)
t-Bu
t-Bu
(ꢄ25 %)
M
8
5
5
8
X
A
t-BuPCl2
M
X
A
ꢁ50.0 [ppm]
200.0
150.0
100.0
50.0
0
ꢁ50.0
[ppm]
100.0
50.0
0
Fig. 6. 31P{1H} NMR spectra of the reaction mixtures of (a) (t-BuP)4, PCl5, and GaCl3 and (b) (t-BuP)4, PhICl2, and Me3SiOTf, both in 1 : 1 : 1
stoichiometries (C6H5F, [D6]benzene capillary, 258C); experimental (upwards) and fitted (downwards) AM2X spin system of 8[GaCl4] and 8[OTf].
the intermediary formation of 7þ followed by subsequent
degradation via nucleophilic attack of Clꢀ as depicted
in Scheme 2. Furthermore, small amounts of cation 9þ and
cyclo-chlorotetraphosphane 10 were identified in the reaction
mixture. Compound 10 was previously synthesised by the
insertion of in situ generated chlorophosphanediyl [P–Cl] in a
P–P bond of 4.[17] A similar reaction might be proposed in this
case. A chloro-group of t-BuPCl2 is sequestered by Me3SiOTf
accompanied by the elimination of a 2-methylpropan-2-ylium
ion. This formally provides the [P–Cl] fragment which reacts

1160
M. H. Holthausen et al.
˚
with 4 to give 10. As previously observed, the 2-methylpropan-
2-ylium ion serves as a proton source and, therefore,
the protonated tetraphosphane 9þ is observed in the reaction
mixture as well. The resonances of cation 9þ in the 31P{1H}
NMR spectrum are not well resolved due to dynamic effects
caused by additional Me3SiOTf in the reaction mixture.
However, cation 9þ was crystallised as the OTfꢀ-salt by layer-
ing the reaction mixture with n-hexane (ꢀ328C) for two days.
The results of the X-ray investigation were identical to the
already reported structure of 9[OTf].[3b]
over 4 A molecular sieves ([D2]dichloromethane, C6H5F)
or potassium mirror (n-hexane). Reagents such as PCl5, GaCl3,
Me3SiOTf, and Ph2PCl were purchased from Sigma-Aldrich.
Ph2PCl and Me3SiOTf were distilled before use. GaCl3 and PCl5
were sublimed before use. Reagents such as (t-BuP)3,[11]
(t-BuP)4,[11] [PCl4][GaCl4],[10] and PhICl2
[18]
were prepared
according to known literature procedures. NMR spectra were
measured on either a Bruker AVANCE III spectrometer
(1H (400.03 MHz), 13C (100.59 MHz), 71Ga (122.02 MHz), 19F
(188.31 MHz) and 31P (161.94 MHz)) or a Bruker AVANCE II
spectrometer (1H (200.13 MHz), 31P (81.01 MHz)) at 300 K
unless otherwisespecified. All 13C NMR spectra were exclusively
recorded with composite pulse decoupling. Chemical shifts were
referenced to TMS d ¼ 0.00 (1H, 13C) or H3PO4 (85 %) d ¼ 0.00
(31P, externally). Chemical shifts (d) are reported in ppm.
Coupling constants (J) are reported in Hz. Yields of products in
solution were determined by integration of all resonances
observed in the corresponding 31P NMR spectra. For com-
pounds which give rise to a higher order spin system in the
31P{1H} NMR spectrum, the resolution enhanced 31P{1H} NMR
spectrum was transferred to the software gNMR, version 5.0, by
Cherwell Scientific.[19] The full line shape iteration procedure of
gNMR was applied to obtain the best match of the fitted to the
experimental spectrum. 1J(31P31P) coupling constants were set
to negative values[20] and all other signs of the coupling con-
stants were obtained accordingly. The designation of the spin
systems were performed by convention. The spin system is
considered to be higher order and consecutive alphabet letters
are assigned if Dd(PiPii)/nJ(PiPii) ,10. For Dd(PiPii)/nJ(PiPii)
.10, the spin system is considered to be pseudo first order and
the assigned letters are separated (alphabet). Melting points
were recorded on an electrochemical melting point apparatus
(Barnstead Electrothermal IA9100) in sealed capillaries under
argon atmosphere and are uncorrected. Infrared (IR) and Raman
spectra were recorded at ambient temperature using a Bruker
Vertex 70 instrument equipped with a RAM II module
(Nd : YAG laser, 1064 nm). The Raman intensities are reported
in percent relative to the most intense peak and are given in
parentheses. An attenuated total reflectance (ATR) unit
(diamond) was used for recording IR spectra. The intensities are
reported relative to the most intense peak and are given in
parentheses using the following abbreviations: vw ¼ very weak,
w ¼ weak, m ¼ medium, s ¼ strong, v ¼ very strong. Elemental
analyses were performed on a Vario EL III CHNS elemental
analyser at the IAAC, University of Mu¨nster, Germany.
The attempted chloronium addition to cyclo-triphosphane
4 indicated that cyclo-tetraphosphane 5 might be a suitable
substrate in such a reaction. Thus, the reactions of 5 with PCl5/
GaCl3 and PhICl2/Me3SiOTf in C6H5F were investigated. The 31
P
{1H} NMR spectra of the reaction mixtures are depicted in Fig. 6.
In both cases the formation of cation 8þ is indicated by its AM2X
spin system (Table 1). The tetra-coordinated phosphorus atom
resonates at lower field (d(PA) ¼ 99.4ppm) compared with
organo-substituted triphosphanylphosphonium ions.[3] This is
caused by the ꢀI effect of the chloro-substituent. In the case of
GaCl3 as the chloride abstracting agent the formation of 8þ is
almost quantitative and the corresponding GaClꢀ4 -salt was
obtained in a high yield (85%) by addition of n-hexane to the
reaction mixture and isolation of the formed precipitate. Single
crystals of 8[GaCl4] were obtained by slow diffusion of n-hexane
(ꢀ328C) into a C6H5F solution and details of the structure
refinement and crystallographic data are shown in Table 2. The
chlorine atom of the cation in 8[GaCl4] exhibits a four-fold
positional disorder with a site occupancy factor of the chlorine
atom of 0.25. Thus, structural parameters of the compound are not
discussed; however, the constitution of the compound is verified.
If PhICl2 is used in combination with Me3SiOTf as a chloride
abstracting agent only little conversion of 5 to 8þ is observed
(,25%). Next to unreacted starting material 5 the phosphane
t-BuPCl2 constitutes oneof the main products(Fig. 6b). Thisisthe
result of nucleophilic degradation by chloride anions and renders
Me3SiOTf as the less suitable chloride abstracting agent.
Conclusions
The insertion of a Ph2Pþ-phosphenium ion, derived from
Ph2PCl and GaCl3 or Me3SiOTf, into a P–P bond of (t-BuP)3, as
well as halonium addition with chloronium ion sources PCl5/GaCl3
or PhICl2/Me3SiOTf to (t-BuP)3 and (t-BuP)4, was investigated.
Both reactions reveal a strong dependency on the chloride
abstracting reagent. GaCl3 is the stronger halide abstracting
reagent yielding quantitatively the cations [Ph2P(t-BuP)3]þ (6þ)
and [(t-BuP)4Cl]þ (8þ) as gallate salts. Only moderate conver-
sion is observed if Me3SiOTf is used. However, an interesting
Me3SiOTf-mediated ring expansion reaction is unveiled
allowing for the smooth conversion of (t-BuP)3 to (t-BuP)4. This
is important from a synthetic point of view since the elaborate
separation of (t-BuP)n (n ¼ 3, 4) can be avoided.
6[GaCl4]
A solution of Ph2PCl (661.9 mg, 3.0 mmol) and GaCl3
(528.2 mg, 3.0 mmol) in C6H5F (10 mL) was slowly added to a
solution of (t-BuP)3 (792.8 mg, 3.0 mmol) in C6H5F (10 mL).
The yellow reaction mixture was stirred for 30 min at ambient
temperature. 31P{1H} NMR investigation of the reaction
mixture indicated complete conversion to 6[GaCl4]. Upon
addition of n-hexane (5 mL) the separation of orange oil was
observed which solidified after removing the supernatant and
adding n-hexane (5 mL) again. The orange solid was washed
with n-hexane (3 ꢁ 5 mL) and dried under vacuum yielding
analytically pure, moisture and air-sensitive 6[GaCl4] (1.3 g,
66 %). Mp 160–1638C (Found: C 43.3, H 5.3. C24H37Cl4GaP4
requires C 43.6, H 5.7 %); Raman n (200 mW)/cmꢀ1 3060 (57),
2958 (33), 2896 (69), 1583 (75), 1459 (21), 1440 (12), 1168 (33),
1089 (28), 1027 (32), 999 (100), 617 (15), 575 (35), 550 (18),
498 (22), 345 (82), 227 (19), 187 (38), 162 (21), 150 (27);
Experimental
General
All reactions were performed in a glove box produced by
MBraun, or using Schlenk techniques under an inert atmosphere
of purified Argon (purchased from Westfalen AG). Dry oxygen-
free C6H5F, CH2Cl2 (drying agent: CaH2) and n-hexane (drying
agent: sodium) were employed. Anhydrous deuterated dichlor-
omethane ([D2]dichloromethane) was purchased from Sigma-
Aldrich. All distilled and deuterated solvents were stored either

Phosphorus Chemistry
1161
n
max(neat)/cmꢀ1 3058 (vw), 2951 (s), 2858 (vw), 1734 (vw),
Ring Expansion of (t-BuP)3 in the Presence of Me3SiOTf
1716 (vw), 1698 (vw), 1684 (vw), 1653 (vw), 1558 (vw), 1541
(w), 1507 (vw), 1457 (m), 1438 (s), 1393 (w), 1364 (m), 1310
(w), 1156 (v.), 1097 (vw), 997 (m), 937 (w), 801 (m), 739 (s),
686 (m), 619 (vw), 593 (w), 548 (m), 502 (w), 471 (s); 1H NMR
([D2]dichloromethane, 400.03 MHz) d 1.30 (9H, d, PMC(CH3)3,
3J(HPM) ¼ 8.4 Hz), 1.32 (9H, d, PMC(CH3)3, 3J(HPM) ¼
8.4 Hz), 1.38 (9H, d, PAC(CH3)3, 3J(HPA) ¼ 14.3 Hz), 7.66–7.96
(10H, m, PX(C6H6)2); 13C{1H} NMR ( [D2]dichloromethane,
A: Me3SiOTf (222.3 mg, 1.0 mmol) was added to a solution of
(t-BuP)3 (264.3 mg, 1.0 mmol) in C6H5F (2 mL). The reaction
mixture was stirred at ambient temperature and the reaction
progress was monitored by 31P{1H} NMR spectroscopy after
1, 12, 36, and 72 h.
B: Me3SiOTf (22.2 mg, 0.1 mmol) was added to a solution of
(t-BuP)3 (264.3 mg, 1.0 mmol) in C6H5F (2 mL). The reaction
mixture was stirred at ambient temperature for 6 h. 31P{1H}
NMR investigation of the reaction mixture indicated complete
conversion to (t-BuP)4 (5).
2
100.59 MHz) d 29.4 (3C, dt, PXC(CH3)3, J(CPX) ¼ 15.9 Hz,
3J(CPM) ¼ 5.0 Hz), 31.3 (6C, m, PMC(CH3)3), 31.9 (1C, m, PXC
(CH3)3), 37.6 (2C, m, PMC(CH3)3), 117.6 (1C, m, i-Ph), 124.3
(1C, m, i-Ph), 131.1 (2C, d, m-Ph, 3J(CPX) ¼ 2.2 Hz), 131.2 (2C,
d, m-Ph, 3J(CPX) ¼ 2.3 Hz), 133.5 (2C, dt, o-Ph, 2J(CPX) ¼
9.9 Hz, 3J(CPM) ¼ 4.8 Hz), 135.0(1C, d, p-Ph, 4J(CPX) ¼ 3.5 Hz),
135.6 (2C, dt, o-Ph, 2J(CPX) ¼ 10.1 Hz, 3J(CPM) ¼ 4.7 Hz),
Inboth cases 5 can be obtainedquantitatively fromthe reaction
mixtures by removing Me3SiOTf and C6H5F under vacuum.
Reaction of (t-BuP)3 with [PCl4][GaCl4]
A suspension of [PCl4][GaCl4] (384.3 mg, 1 mmol) in C6H5F
(5 mL) was added in a single portion to a solution of (t-BuP)3
(264.3 mg, 1.0 mmol) in C6H5F (5 mL). The reaction mixture
turned immediately orange and an orange precipitate formed.
The reaction mixture was stirred at ambient temperature for one
hour. The supernatant solution was investigated by 31P{1H}
NMR spectroscopy. Crystals of 9[GaCl4], which were suitable
for single crystalX-ray structuredetermination, were obtainedby
diffusion of n-hexane into the filtered reaction mixture at ꢀ308C.
4
136.1 (1C, d, p-Ph, J(CPX) ¼ 4.2 Hz); 71Ga{1H} NMR ([D2]
dichloromethane, 122.02 MHz) d 250.3 (s, Dn1/2 ¼ 55 Hz);
31P{1H} NMR ([D2]dichloromethane, 161.94 MHz) AM2X
spin system d(PA) ¼ ꢀ22.2, d(PM) ¼ ꢀ12.4, d(PX) ¼ 10.9,
1J(PAPM) ¼ ꢀ142 Hz,
1J(PMPX) ¼ ꢀ277 Hz,
2J(PAPX) ¼
ꢀ22.3 Hz. Crystals of 6[GaCl4], which were suitable for single
crystal X-ray structure determination, were obtained by diffu-
sion of n-hexane into a C6H5F solution at ꢀ308C.
Reaction of (t-BuP)3 with PhICl2 in the Presence of Me3SiOTf
6[OTf]
A solution of PhICl2 (274.9 mg, 1.0 mmol) in C6H5F (5 mL) was
added dropwise to a solution of (t-BuP)3 (264.3 mg, 1.0 mmol)
and Me3SiOTf (222.3 mg, 1.0 mmol) in C6H5F (5 mL).The
obtained yellow solution was stirred at ambient temperature for
one hour. The reaction mixture was investigated by 31P{1H}
NMR spectroscopy.
A solution of Ph2PCl (220.6 mg, 1.0 mmol) and Me3SiOTf
(222.3 mg, 1.0 mmol) in C6H5F (3 mL) was slowly added to a
solution of (t-BuP)3 (264.3 mg, 1.0 mmol) in C6H5F (5 mL). The
yellow reaction mixture was stirred for one hour at ambient
temperature and investigated by means of 31P{1H} NMR
spectroscopy. The addition of n-hexane (5 mL) to the reaction
mixture initiated the formation of a yellow microcrystalline
material. The solid was washed with n-hexane (3 ꢁ 3 mL) and
dried under vacuum to yield analytically pure, moisture and air-
sensitive 6[OTf] (197 mg, 0.3 mmol, 33 %). Mp: 144–1478C
(Found: C 49.7, H 5.6. C25H37F3O3P4S requires C 50.2, H
6.2 %); Raman n (200 mW)/cmꢀ1 3061 (29), 2896 (36), 2185
(14), 2061 (17), 1584 (35), 1168 (17), 1089 (18), 1027 (18), 999
(33), 345 (100), 227 (33), 187 (19); nmax(neat)/cmꢀ1 2950 (s),
1979 (vw), 1570 (vw), 1457 (m), 1438 (s), 1392 (w), 1364 (s),
1311 (w), 1165 (v.), 1098 (s), 997 (m), 936 (vw), 801 (m), 749
(vw), 738 (m), 687 (s), 619 (w), 593 (w), 548 (s), 501 (w), 471
(m); 1H NMR ([D2]dichloromethane, 400.03 MHz) d 1.30 (9H,
8[GaCl4]
A suspension of [PCl4][GaCl4] (1.54 g, 4.0 mmol) in CH2Cl2
(20 mL) was added to a solution of (t-BuP)4 (1.41 g, 4.0 mmol)
in CH2Cl2 (15 mL) at ꢀ788C within 30 min. The reaction mix-
ture was warmed to ambient temperature, stirred for 30 min and
investigated by means of 31P{1H} NMR spectroscopy. Upon
addition of n-hexane (40 mL) the precipitation of a pale yellow,
microcrystalline solid was observed. The supernatant was
removed and the solid was washed with n-hexane (2 ꢁ 10 mL)
and dried under vacuum yielding analytically pure, moisture and
air-sensitive 8[GaCl4] (1.6 g, 2.7 mmol, 67 %). Mp 160–1618C
(Found: C 31.6, H 5.8. C16H36Cl5GaP4 requires C 32.1, H
6.1 %); Raman n (200 mW)/cmꢀ1 2963 (15), 2934 (11), 2897
(58), 1462 (21), 1441 (7), 1160 (15), 938 (8), 794 (19), 562 (26),
475 (7), 438 (19), 346 (38), 204 (9), 189 (20), 169 (7), 154 (100);
3
d, PMC(CH3)3, J(HPM) ¼ 8.4 Hz), 1.32 (9H, d, PMC(CH3)3,
3J(HPM) ¼ 8.4 Hz), 1.38 (9H, d, PAC(CH3)3, 3J(HPA) ¼
14.3 Hz), 7.66–7.96 (10H, m, PX(C6H6)2); 13C{1H} NMR ([D2]
dichloromethane, 100.59 MHz) d 29.3 (3C, dt, PAC(CH3)3,
2J(CPA) ¼ 15.5 Hz, J(CPM) ¼ 4.8 Hz) 31.1–31.3 (6C, m, PMC
n
max(neat)/cmꢀ1 2950 (s), 2860 (vw), 2341 (vw), 2361 (m), 1716
3
(CH3)3), 31.5–32.2 (1C, m, PAC(CH3)3), 37.3–37.8 (2C, m, PMC
(CH3)3), 117.6 (1C, m, i-Ph), 124.3 (1C, m, i-Ph), 131.1 (2C, d,
m-Ph, 3J(CPX) ¼ 1.3 Hz), 131.2 (2C, d, m-Ph, 3J(CPX) ¼
1.5 Hz), 133.5 (2C, dt, o-Ph, 2J(CPX) ¼ 11.1 Hz, 3J(CPM) ¼
7.1 Hz), 135.0 (1C, d, p-Ph, 4J(CPX)¼ 3.5 Hz), 135.6 (2C, dt, o-Ph,
2J(CPX) ¼ 10.0 Hz, 3J(CPM) ¼ 4.7 Hz), 136.1 (1C, d, p-Ph,
(w), 1698 (vw), 1558 (vw), 1541 (w), 1507 (w), 1463 (s), 1394
(w), 1366 (m), 1245 (w), 1155 (v.), 1007 (m), 937 (w), 791 (m);
1H NMR ([D2]dichloromethane, 400.03 MHz) d 1.49 (9H, d,
PXC(CH3)3, 3J(HPX) ¼ 24.0 Hz), 1.51 (9H, d, PAC(CH3)3,
3J(HPA) ¼ 15.1 Hz), 1.52 (18H, d, PMC(CH3)3, 3J(HPM) ¼
17.5 Hz); 13C{1H} NMR ([D2]dichloromethane, 100.59 MHz)
d 23.2 (3C, td, PXC(CH3)3, 3J(CPX) ¼ 3.2 Hz, 2J(CPM) ¼
2.5 Hz), 28.8 (3C, dt, PAC(CH3)3, 2J(CPA) ¼ 15.7 Hz,
3J(CPM) ¼ 5.0 Hz), 30.0 (6C, ddd, PMC(CH3)3, 2J(CPM) ¼
4J(CPX) ¼ 4.0 Hz);
19F
NMR
([D2]dichloromethane,
188.31 MHz) d ꢀ78.8 (s, CF3); 31P{1H} NMR ([D6]benzene,
161.94 MHz): AM2X spin system d(PA) ¼ ꢀ23.1, d(PM) ¼
ꢀ13.0, d(PX) ¼ 10.5, 1J(PAPM) ¼ ꢀ141 Hz, 1J(PMPX) ¼
3
3
15.6 Hz, J(CPA) ¼ 6.4 Hz, J(CPX) ¼ 4.4 Hz), 32.4 (1C, ddt,
PAC(CH3)3, nJ(CP) ¼ 29.5 Hz, nJ(CP) ¼ 17.7 Hz, nJ(CP) ¼
13.4 Hz), 40.1–40.7 (2C, m, PMC(CH3)3), 45.4–45.8 (1C,
m, PXC(CH3)3); 71Ga{1H}-NMR ([D2]dichloromethane,
2
ꢀ275 Hz, J(PAPX) ¼ ꢀ22 Hz. Crystals of 6[OTf], which were
suitable for single crystal X-ray structure determination, were
obtainedby diffusion of n-hexane intoa C6H5F solutionat ꢀ308C.

1162
M. H. Holthausen et al.
122.02 MHz) d 250.1 (s, Dn1/2 ¼ 52 Hz); 31P{1H} NMR ([D2]
dichloromethane, 166.94 MHz): AM2X spin system d(PA) ¼
ꢀ42.7, d(PM) ¼ ꢀ11.1, d(PX) ¼ 98.5, 1J(PAPM) ¼ ꢀ157 Hz,
1J(PMPX) ¼ ꢀ330 Hz, 2J(PAPX) ¼ 8.8 Hz. Crystals of 9[GaCl4],
which were suitable for single crystal X-ray structure determi-
nation, were obtained by diffusion of n-hexane into a CH2Cl2
solution at ꢀ308C.
(f) M. H. Holthausen, J. J. Weigand, Z. Anorg. Allg. Chem. 2012, 638,
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Crystal Structures
Single crystals were coated with Paratone-N oil, mounted using
a glass fibre pin and frozen in the cold nitrogen stream of the
goniometer. X-ray diffraction data for compound 6[GaCl4]
([Ph2P(t-BuP)3][GaCl4]) and 6[OTf] ([Ph2P(t-BuP)3][OTf])
were collected on a Bruker AXS APEX II CCD diffractometer
equipped with a rotation anode at 153(2) K using graphite-
˚
monochromated MoKa radiation (l ¼ 0.71073 A) with a scan
width of 0.38 and 15 s exposure time. The generator settings
were 50 kV and 170 mA. X-ray diffraction data for compounds 8
[GaCl4] ([(t-BuP4)Cl][GaCl4]) and 9[GaCl4] ([(t-BuP4)H]
[GaCl4]) was collected on a Bruker SMART CCD diffracto-
meter equipped with a rotation anode at 153(2) K using graphite-
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˚
monochromated CuKa radiation (l ¼ 1.54178 A) with a scan
width of 0.58 and 20/40 s exposure times. The generator settings
were 45 kV and 110 mA. For all cases data reduction was done
using the Bruker SMART[21] software package. Data sets were
corrected for absorption effects using SADABS routine (empir-
ical multi-scan method). Structure solutions were found with the
SHELXS-97 package using the direct method and were refined
with SHELXL-97[22] against F2 using first isotropic and later
anisotropic thermal parameters for all non-hydrogen atoms.
Further details are summarised in Table 2 or can be obtained
from the CCDC database with the respective CCDC reference
number provided in Table 2. In the case of 8[GaCl4]
([t-Bu4P4Cl][GaCl4]) the chlorine atom of the cation exhibits a
four-fold positional disorder. The s.o.f. (site occupancy factor)
of the chlorine atom is 0.25. In 6[OTf] ([Ph2P(t-BuP)3][OTf])
the triflate anion is disordered over two positions with an s.o.f. of
52 : 48. Hydrogen atoms were generated with idealised geo-
metries and isotropically refined using a riding model.
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Acknowledgements
1963, 85, 2462. doi:10.1021/JA00899A027
Wethank theNaturalSciencesandEngineeringResearchCouncilofCanada,
the Canada Research Chairs Program, the CanadaFoundationforInnovation,
the Walter C. Sumner Foundation, and the Nova Scotia Research and
Innovation Trust Fund for funding. We also gratefully acknowledge the FCI
(Liebig fellowship for M.H.H.), the European Phosphorus Science Network
(PhoSciNet CM0802) and the DFG (WE 4621/2–1, travel stipend for D.K.).
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