The Phosphonium Ion [Cy3PCHCl2]+: Synthesis and Properties

Article abstract of DOI:10.1002/ejic.201800532

The synthetic pathway to the functional phosphonium cation [Cy₃PCHCl₂]⁺ (3) has been evaluated by using in situ ³¹P NMR spectroscopy and mass spectrometry. The synthesis is only successful if CCl₄/CHCl₃ mixtures are used. A mechanism for the varying reactivity in different solvents is given as well as a mechanism for the observed equilibrium between ions [Cy₃PCHCl₂]⁺ and [Cy₃PCH₂Cl]⁺ (12). Through the anticipated hydrogen bonding interaction between [Cy₃PCHCl₂]⁺ and the corresponding anion, crystal structures of the compounds [Cy₃PCHCl₂]Cl·2CHCl₃ (3a) and [Cy₃PCHCl₂]₃[H₃O][H₅O₂]Cl₅·C₆D₆ (3b) could be obtained and evaluated.

Full text of DOI:10.1002/ejic.201800532

A Journal of
Accepted Article
Title: The phosphonium ion [Cy3PCHCl2]+: synthesis and properties
Authors: Nils Spang, Matthias Müller, and Magnus Richard Buchner
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Eur. J. Inorg. Chem. 10.1002/ejic.201800532
Link to VoR: http://dx.doi.org/10.1002/ejic.201800532

10.1002/ejic.201800532
European Journal of Inorganic Chemistry
COMMUNICATION
The phosphonium ion [Cy3PCHCl2]+: synthesis and properties
Nils Spang,[a] Matthias Müller,[a] and Magnus R. Buchner*[a]
Abstract: The synthetic pathway to the functional phosphonium
cation [Cy3PCHCl2]+ (3) has been evaluated via in situ 31P NMR
spectroscopy and mass spectrometry. The synthesis is only
successful if CCl4/CHCl3 mixtures are used. A mechanism for the
varying reactivity in different solvents is given as well as a for the
observed equilibrium between ions [Cy3PCHCl2]+ and [Cy3PCH2Cl]+
(12). Through the anticipated hydrogen bonding interaction between
[Cy3PCHCl2]+ and the corresponding anion, crystal structures of the
organic media but should also be promising in phosphonium ion
catalyzed reactions.[13]
compounds
[Cy3PCHCl2]Cl · 2CHCl3
(3a)
and
Figure 1. Tetraphenylphosphonium (1), triphenyl dichloromethyl phosphonium
(2) and tricyclohexyl dichloromethyl phosphonium (3) cations.
[Cy3PCHCl2]3[H3O][H5O2]Cl5  C6D6 (3b) could be obtained and
evaluated.
Results and Discussion
Introduction
Appel and Huppertz reported the synthesis of alkyl diphenyl
Tetraphenyl phosphonium (1) (figure 1) is widely employed as a
weakly coordinating cation.[1] Even though the weak interaction
between the phosphonium ion and the investigated anion is
generally desirable this has the drawback, that the anions are
frequently disordered in the crystal lattice.[2] This problem is
more severe with small anions. To facilitate ordered
crystallization some interaction between cation and anion is
necessary.[3] This has been achieved for example in pyridinium
dichloromethyl
phosphonium
salts
from
alkyl
diphenylphosphines (4) in non-polar aprotic solvents. They
describe, that the phosphine is converted to alkyl diphenyl
trichloromethyl phosphonium chloride (5) by reaction with CCl4.
The salt 5 is subsequently attacked by free phosphine 4 to yield
alkyl diphenyl dichloromethylene phosphoranes 6 and alkyl
diphenyl chloro phosphonium chlorides 7. Ylide
6 then
deprotonates phosphonium salt 7 to produce the desired alkyl
diphenyl dichloromethyl phosphonium salts 8 and diphenyl
chloro ylides 9 and the latter rearranges to α-chloroalkyl diphenyl
phosphine 10.[14] This reaction cascade is summarized in
scheme 1. In analogy to this synthesis we reacted
tricyclohexylphosphine with CCl4 in toluene following the
conditions described by Appel and Huppertz. However we were
neither able to isolate pure tricyclohexyl dichloromethyl
hexafluorotitanates,[4]
imidazolium
hexafluorophosphates,[5]
diamidopyridinium phosphates[6] and cyclam salts[7] which all
form cation-anion hydrogen bonds.[8] However most of these
systems have the drawback, that they are only soluble in water
or at least highly protic solvents. Therefore phosphonium cations
are of interest, which bear three bulky organic groups to still
facilitate solubility in organic solvents, but also have a group
which is able to coordinate to the anion. Thus C-H-acidic groups
like (di)chloro methylene, which can form hydrogen bonds with
anions would be ideal. However there are only very little
examples of such cations with [Ph3PCHCl2]+ (2) being by far the
most prominent.[9] Though this phosphonium salt is extremely C-
H-acidic, which results in easy deprotonation with the
subsequent formation of the phosphorus ylide. Hence cation 2 is
exclusively used as substrate for Wittig reactions.[10] To reduce
the C-H-acidity of the methylene group more electron donating
substituents like tricyclohexyl are necessary at the phosphorus
phosphonium
chloride
(3a)
nor
an
α-chloro
tricyclohexylphosphine. Instead we observed the formation of
salt 3a together with tricyclohexyl dichloro phosphorane (11)[15]
in the 31P NMR spectrum of the reaction product.
Two column scheme, please see penultimate page of the document
Scheme 1. Reaction of n-propyl diphenylphosphine with CCl4 in non-polar
aprotic solvents described by Appel and Huppertz.[14]
atom. However there are only two examples of
12]
tricyclohexylphosphonium ions.[11,
We therefore decided to
It was unclear whether the different reactivities observed for
PCy3 and alkyl diphenylphosphines 4 were caused by the higher
electron density at the phosphorus atom in the prior phosphine
or through different solubilities. Therefore we reacted PCy3 with
CCl4 in benzene (aprotic solvent without dipole moment),
dichloromethane (aprotic solvent with dipole moment) and
chloroform (protic). Additionally we also investigated the
reactivity of PCy3 with chloroform in the absence of CCl4. Upon
addition of CCl4 to a dichloromethane solution of PCy3 the
reaction mixtures turned intensely yellow. Also the benzene/CCl4
solution with PCy3 turned yellow overnight, while the reaction
solutions containing chloroform stayed colorless. In situ reaction
monitoring via 31P NMR spectroscopy revealed, that PCy3 was
establish
a synthetic route to tricyclohexyl dichloromethyl
phosphonium cation 3. This cation would not only be an ideal
cation to facilitate the ordered crystallization of small anions from
[a]
N. Spang, M. Müller, Dr. M. R. Buchner
Anorganische Chemie, Nachwuchsgruppe Berylliumchemie
Fachbereich Chemie, Philipps-Universität Marburg
Hans-Meerwein-Strasse 4, 35032 Marburg (Germany)
E-mail: magnus.buchner@chemie.uni-marburg.de
http://www.uni-marburg.de/fb15/ag-buchner [a] Initial(s),
Supporting information for this article is given via a link at the end of
the document.
This article is protected by copyright. All rights reserved.

10.1002/ejic.201800532
European Journal of Inorganic Chemistry
COMMUNICATION
completely converted to two different species in the
chloroform/CCl4 mixture overnight. The 31P NMR signals of
these two species were observed at 40.8 and 34.2 ppm with an
integral ratio of ca. 6.6:1 and are assigned to the phosphonium
To confirm our assignments of the phosphonium salts high
resolution LIFDI mass spectrometry was performed on the
reaction solutions. Table 1 summarizes the observed cations
and gives the relative signal intensities. In all solutions
containing CCl4 the phosphonium ions 3 and 12 were observed
together with the tricyclohexyl trichloromethyl phosphonium
cation 13 and [Cy3PCH3]+. Additionally aggregates of two
phosphonium cations with one chloride anion could be detected,
which are similar to known {[Ph3PCl]Cl[ClPPh3]}+.[18] This shows
that these phosphonium cation can indeed interact with anions
through hydrogen bonds as anticipated. In contrast to the CCl4
containing solutions only signals for cations 12 and [Cy3PCH3]+
cations
3
and
[Cy3PCH2Cl]+
(12)
respectively.
In
dichloromethane/CCl4 and benzene/CCl4 mixtures four different
species were observed after 12 h. The most intense signal was
again observed at 40.8 ppm while additional signals at 64.8,
98.7 and 107.7 ppm were observed. The signal at 98.7 ppm is
assigned to known phosphorane 11[16] while the one at
107.7 ppm belongs to [Cy3PCl]+, the corresponding
phosphonium form.[17] In benzene/CCl4 the signal at 64.8 ppm
disappears after 36 h while this takes several days in
CH2Cl2/CCl4. In the absence of CCl4 no conversion of PCy3 in
chloroform was observed at ambient temperature. However after
heating this solution to 80 °C for 12 h in a closed vessel two
more signals besides the one for PCy3 could be observed in the
31P NMR spectrum. The major one at 34.2 ppm being
phosphonium salt 12 and one at 21.2 ppm which we assign to
[Cy3PCH3]+. The final 31P NMR spectra of these four reaction
mixtures are depicted in figure 2.
together
with
the
corresponding
aggregate
{[Cy3PCH2Cl]Cl[Cy3PCH3]}+ could be detected in the chloroform
solution.
To gain insights into the nature of the intermediate species
accountable for the 31P NMR signal at 64.8 ppm LIFDI mass
spectrometry was performed on PCy3 solutions in
dichloromethane / CCl4 mixtures after different reaction times (SI
Table S1). Only the cations 13 and 3 were observed, with the
prior initially being the dominant species. The intensity of this
signal diminished rapidly over time while the one for ion 3
increased and after 115 h only species 3 could be detected. We
therefore assign the signal at 64.8 ppm to [Cy3PCCl3]+.
Table 1. Summary of observed cations in LIFDI mass spectrometry (FD+
ionization mode) and their relative signal intensities in the reaction solutions of
PCy3 with benzene / CCl4, dichloromethane / CCl4, chloroform / CCl4 mixtures
and with neat chloroform after two weeks reaction time.
Two column table, please see penultimate page of the document
In accordance with our findings from NMR spectroscopy and
mass spectrometry we therefore propose the following reaction
mechanism in the presence of CCl4. Tricyclohexylphosphine
reacts instantaneously with CCl4 to give [Cy3PCCl3]+ (13), which
is in agreement with the analogous reaction of
triphenylphosphine that yields [Ph3PCCl3]+.[9] Cation 13 then
reacts with chloride to the ylide Cy3P=CCl2 (14) and chlorine,
even though the equilibrium should be far on the side of cation
13. In chloroform ylide 14 is instantaneously protonated by the
solvent due to the relatively high C-H-acidity, generating cation 3
and dichlorocarbene. The latter then traps the chlorine in
solution and forms CCl4. In the case of the less C-H-acidic
solvents, benzene and dichloromethane, ylide 14 is more stable.
Therefore the formed chlorine is trapped faster by excess
phosphine than solvent deprotonation occurs, so phosphorane
11 is formed.[19] Ylide 14 subsequently deprotonates the solvent
giving cation 3. However due to the lack of chlorine the
deprotonated solvent can react with further solvent molecules to
form oligomeric species which account for the yellow color of the
reaction solutions. The described mechanism is depicted in
scheme 2.
Figure 2. 31P NMR spectra of Cy3P in a) benzene / CCl4, b)
dichloromethane / CCl4, c) chloroform / CCl4 mixtures and d) neat chloroform
after a)-c) two weeks at rt and d) 13 days at rt and 12 h at 80 °C. Relative
signal integrals: a) [Cy3PCl]+ : Cy3PCl2 : [Cy3PCHCl2]+ = 2.8 : 1 : 6.3 , b)
[Cy3PCl]+
: Cy3PCl2 : = 5.1 : 1 : :
[Cy3PCHCl2]+ 9.3, c) [Cy3PCHCl2]+
[Cy3PCH2Cl]+ = 5.9 : 1 and d) [Cy3PCH2Cl]+ : [Cy3PCH3]+ : Cy3P = 6.9 : 1.5 : 1.
This article is protected by copyright. All rights reserved.

10.1002/ejic.201800532
European Journal of Inorganic Chemistry
COMMUNICATION
Scheme 3. Proposed equilibrium between the tricyclohexyl dichloromethyl
phosphonium (3) and tricyclohexyl chloromethyl phosphonium (12) cations
(black) and suggested exchange mechanism (grey).
Therefore tricyclohexyl dichloromethyl phosphonium chloride
was prepared by stirring Cy3P for three days in a 1:2 mixture of
CHCl3 and CCl4. Layering of the reaction mixture with n-pentane
Scheme 2. Proposed reaction cascade for the formation of phosphonium ion 3
and phosphorane 11.
gave
colorless
crystals
of
the
chloride
salt
[Cy3PCHCl2]Cl · 2CHCl3 (3a) in 36 % isolated yield.
Crystallographic details are given in table 2. Compound 3a
crystallizes in the monoclinic space group P21/c (14). The
structure of cation 3 is shown in figure 3.
In accordance with this reaction mechanism in chloroform we
tested if catalytic amounts of CCl4 are sufficient to convert PCy3
to phophonium cation 3. However we observed the formation of
phosphonium cations 3 and 12 in a ratio of 1:1.2 via 31P NMR
spectroscopy. This is presumable caused by an equilibrium
between these two phosphonium ions. Due to the steric bulk of
the cyclohexyl groups cation 3 may react with chloride under the
formation of chlorine and Cy3P=CHCl (15), which then
deprotonates chloroform to give species 12 and dichlorocarbene
which react with chlorine to CCl4. In the same manor cation 12
may react with chloride to form ylide 15 and hydrogen chloride.
Through reaction with CCl4 ion
3 is then reformed and
dichlorocarbene is generated which now reacts with HCl to
chloroform. This is summarized in scheme 3. Therefore excess
CCl4 is needed to shift the equilibrium to the side of
phosphonium ion 3. This also explains why in the absence of
CCl4 only cations 12 and [Cy3PCH3]+ were observed. Direct
reaction of PCy3 with chloroform gives cation 3. However since
this reaction needs heating to progress at reasonable reaction
rates also the equilibrium is established faster and is shifted
completely onto the side of cation 12 due to the lack of CCl4 in
solution. Via an analogue mechanism also the completely
dechlorinated phosphonium salt [Cy3PCH3]+ can be formed.
Figure 3. Molecular structure of cation 3 in the crystal structure of compound
3a. Displacement ellipsoids are shown at the 70 % probability level at 100 K,
hydrogen atom isotropic with arbitrary radii and cyclohexyl hydrogen atoms
are omitted for clarity.
The phosphorus atom is bound to the four carbon atoms C1, C2,
C8 and C14, which results in tetrahedral coordination around the
phosphorus atom. The cyclohexyl substituents and the
substituents at the C1 atom adopt a staggered conformation.
The P-C distances to the three cyclohexyl carbon atoms (C2, C8
This article is protected by copyright. All rights reserved.

10.1002/ejic.201800532
European Journal of Inorganic Chemistry
COMMUNICATION
and C14) directly bound to the phosphorus atom are with
1.8163(15)-1.8433(15) Å slightly shorter than the corresponding
distances in PCy3 (1.865(5)-1.871(7) Å)[20] and comparable to
the ones found in [Cy3P(C6H4F)]+ (1.815(5)-1.822(4) Å)[12] and
[Cy3PH]+ (1.817(2)-1.823(2) Å).[11] The reduction in bond length
by approximately 0.02 Å is in accordance with the smaller P-C
distances observed in [Ph4P]Cl (1.781(2)-1.793(2) Å)[21] [Ph4P]Br
(1.768(5)-1.792(4) Å) and [Ph4P]I (1.799(4) Å)[22] compared to
PPh3 (1.822(5)-1.831(5) Å).[23] The distance of the phosphorus
atom to the methylene carbon atom (C1) is with 1.8467(17) Å
comparable to the other P-C distances in salt 3a. The C-C
distances in the cyclohexyl rings are with 1.518(3)-1.545(2) Å
comparable to the ones found in PCy3,[20] [Cy3P(C6H4F)]+[12] and
[Cy3PH]+.[11] The C-Cl distances in the methylene subunit are
with 1.7756(16) and 1.7783(17) Å similar to the ones found in
CH2Cl2 (1.7684(14) Å)[24] and CHCl3 (1.7587(12)-1.7613(7) Å).[25]
Due to the sterics the Cl1-C1-Cl2 bond angle is with 109.53(9)°
smaller than in CH2Cl2 (112.009(4)°)[24] and comparable to
CHCl3 (109.65(6)-111.16(4)°).[25] The C2-P1-C14 and C8-P1-
C14 angles are with 110.61(7)° and 114.58(7)° respectively
larger than the C2-P1-C8 angle of 108.24(7)°, which is due to
carbon atom C14 standing into the sterically most crowded
quadrant where the two chloride atoms at the methylene carbon
atom C1 are situated. In accordance to this the C1-P1-C14
angle is with 109.99(8)° larger than the C1-P1-C8 (109.41(7)°)
and C1-P1-C2 (103.41(7)°) angles.
Table 2. Selected crystallographic data for compound 3a and 3b.
3a
3b
Empirical formula
C21H36Cl9P
colorless needle
638.52
C60H113Cl11O3P3
colorless block
1365.36
Color and appearance
Molecular mass / g·mol−1
Crystal system
monoclinic
P21/c (14)
10.9200(4)
13.9926(6)
19.8402(8)
101.640(1)
2969.2(2)
monoclinic
C2/c (15)
Space group type (No.)
a / Å
b / Å
c / Å
β / °
27.235(6)
15.953(3)
33.640(7)
106.17(3)
V / Å3
Z
14038(5)
4
8
λ / Å
T / K
µ / mm−1
θmax
0.71073 (Mo-Kα)
100(2)
1.54186 (Cu-Kα)
100(2)
0.913
4.939
28.229
65.080
hklmax
−14 ≤ h ≤ 13
−18 ≤ k ≤ 18
−26 ≤ l ≤ 26
0.2  0.07  0.07
0.050, 0.021
0.032, 0.043
0.074, 0.079
0.98
−26 ≤ h ≤ 32
−10 ≤ k ≤ 18
−39 ≤ l ≤ 34
0.055  0.050 · 0.040
0.117, 0.122
0.054, 0.130
0.109, 0.127
1.02
Size / mm3
Rint, Rσ
R(F) (I ≥ 2σ(I), all data)
wR(F2) (I ≥ 2σ(I), all data)
S (all data)
Data, parameter, restraints
Δρmax, Δρmin / e·Å−3
7320, 424, 0
0.72 / −0.52
11415, 726, 0
0.50 / −0.78
Attempts to synthesize cation 3 via the route of Appel and
Huppertz[14] as described above resulted in the serendipitous
Figure 4. Hydrogen bonding of cation 3 and chloroform to chloride in the
crystal structure of compounds 3a. Displacement ellipsoids are shown at the
70 % probability level at 100 K, hydrogen atoms isotropic with arbitrary radii
and the cyclohexyl groups as wireframe image for clarity.
formation of
a
complex salt with the composition
[Cy3PCHCl2]3[H3O][H5O2]Cl5  C6D6 (3b) in which three cations 3
co-crystallized with one hydronium (H3O+) and one Zundel ion
+
(H5O2 ). This compound presumably formed when the
precipitate of the reaction of PCy3 with CCl4 in toluene was
dissolved in non-dried benzene-d6 and layered with non-dried n-
pentane under air. Likely phosphorane 11 reacted with traces of
water to give HCl and phosphine oxide. The HCl subsequently
reacted with further water molecules to the hydronium and
Zundel ions. Compound 3b crystallizes in the monoclinic space
group C2/c (15) (figure 5).
Hydrogen bonds between the hydrogen atom of the methylene
group (H1) as well as the hydrogen atoms at the two chloroform
molecules (H35 & H36) to the chloride anion are present,
resulting in a distorted T-shaped coordination mode at chloride
atom Cl3, with DA distances of 3.359(2) Å (C1Cl3),
3.338(2) Å (C20Cl3) and 3.382(2) Å (C21Cl3), which is in the
typical range of H-bonding interactions. (figure 4).[26]
This article is protected by copyright. All rights reserved.

10.1002/ejic.201800532
European Journal of Inorganic Chemistry
COMMUNICATION
Figure 6. Hydrogen bonding of three phosphonium cations 3 towards one
chloride in the crystal structure of compound 3b. Displacement ellipsoids are
shown at the 70 % probability level at 100 K, hydrogen atoms isotropic with
arbitrary radii and the cyclohexyl groups as wireframe image for clarity.
One chloride ion is coordinated via three hydrogen bonds to the
methylene groups of the three phosphonium cations. This
results in a trigonal planar coordination of the chlorine atom Cl11
by the hydrogen atoms H1, H2 and H3 (figure 6). The DA
distances of 3.505(5) Å (C1Cl3), 3.442(5) Å (C2Cl3) and
3.405(5) Å (C3Cl3) are slightly longer than the ones found in
salt 3a but still in the typical range for H-bonding interactions.[26]
The remaining chloride ions bridge hydronium and Zundel ions
to infinite chains (figure 7). The structural parameters of the
[H3O]+ and [H5O2]+ cations compare well with reference
compounds.[27] Two Zundel ions are bridged by chlorine atom
Cl10 directly on the side of the O3 oxygen atom, while they are
bridged on the side of the O2 oxygen atom via chlorine atoms
Cl7 and Cl9 to the hydronium ion. The free hydrogen-bonding
site at the hydronium ion is saturated by coordination to chlorine
atom Cl8.
Figure 5. A section of the crystal structure of compound 3b. Displacement
ellipsoids are shown at the 70 % probability level at 100 K. For clarity
hydrogen atoms are displayed isotropic with arbitrary radii, the cyclohexyl
groups as wireframe image and crystal benzene is omitted.
The phosphorus atoms in compound 3b show the same
coordination geometry and comparable atom distances and
bond angles found in compound 3a. Again the cyclohexyl
substituents and the substituents at the C1 atom adopt a
staggered conformation, however the difference in the C-P-C
angles is more pronounced with the Cmethylene-P-Ccyclohexyl angle in
the chloride quadrant (vide supra) being in the range of
113.57(18)-114.85(19)°, therefore larger than the other Cmethylene
P-Ccyclohexyl angles with 104.50(18)-105.43(17)° and the Ccyclohexyl
-
-
P-Ccyclohexyl angle opposite to the chlorine quadrant ranging from
107.24(18)° to 109.68(17)° while the other Ccyclohexyl-P-Ccyclohexyl
angles are with 115.85(17)-117.8(2)° sufficiently larger.
This article is protected by copyright. All rights reserved.

10.1002/ejic.201800532
European Journal of Inorganic Chemistry
COMMUNICATION
IR spectroscopy
IR spectra were recorded on a Bruker alpha FTIR spectrometer equipped
with a diamond ATR unit in an argon filled glovebox. Processing of the
spectra was performed with the OPUS software package.[29]
Single crystal X-ray diffraction
Single crystals of 3a were grown from CCl4 / CHCl3 solution by layering
with n-pentane and of 3b by layering a C6D6 solution with n-pentane.
Crystals were selected under exclusion of air in cooled perfluorinated
polyether (Galden, Solvay Solexis) and mounted using the MiTeGen
MicroLoop system. X-ray diffraction data were collected using the
graphite monochromated Mo-Kα radiation of
a Bruker D8 Quest
diffractometer equipped with an Incoatec Microfocus Source and a
CMOS Photon 100 detector and the monochromated Cu-Kα radiation of a
Stoe StadiVari diffractometer equipped with a Xenocs Microfocus Source
and a Dectris Pilatus 300K detector. The diffraction data were reduced
with the X-Area and APEX software package and corrected for
absorption numerically using X-Red.[30] The structure was solved using
Direct Methods (SHELXS-2013/1) and refined against F2 (SHELXL-
2016/4) using the ShelXle software package.[31] All atoms were located
by Difference Fourier synthesis and non-hydrogen atoms refined
anisotropically. Hydrogen atoms were refined isotropically. CCDC
1840433 and CCDC 1840436 contain the supplementary crystallographic
data for compounds 3a and 3b respectively. These data can be obtained
free of charge from The Cambridge Crystallographic Data Centre.
Figure 7. Hydrogen bond network between chloride, hydronium and Zundel
ions in the crystal structure of compound 3b. Displacement ellipsoids are
shown at the 70 % probability level at 100 K, hydrogen atoms isotropic with
arbitrary radii.
Mass spectrometry
Mass spectrometry was performed on a Jeol AccuTOF GCv equipped
with a combined FD / FI / LIFDI source using liquid field desorption
ionization (LIFDI) as ionization technique.
Conclusions
Synthesis and characterization
We were able to synthesize the [Cy3PCHCl2]+ cation 3 which is
able to form hydrogen bonds to anions as anticipated. This is
evident from the species observed in mass spectrometry.
[Cy3PCHCl2]Cl  2 CHCl3 (3a): 500 mg (1.78 mmol) tricyclohexyl
phosphine were weighed into a Schlenk tube, 8.30 ml chloroforme and
15.0 ml CCl4 were added and the reaction mixture stirred for three days
at ambient temperature. The obtained colorless solution was layered with
n-pentane. After 8 days colorless needles had formed, which were
isolated by filtration and dried in vacuo to receive 413 mg (0.647 mmol,
36 %) of product as colorless needles.
Through
[Cy3PCHCl2]Cl · 2CHCl3
this
cation
anion
interaction
(3a)
the
salts
and
[Cy3PCHCl2]3[H3O][H5O2]Cl5  C6D6 (3b) could be crystallized. It
is also evident that the solvent system is crucial to synthesize
the dichloromethylene phosphonium ion 3. Only in the presence
of CCl4 and a protic solvent like chloroform cation 3 is produced
without side reactions. However due to an equilibrium between
ions [Cy3PCHCl2]+ (3) and [Cy3PCH2Cl]+ (12) traces of the latter
cation are always present. Also rather high ratios of CCl4 to
CHCl3 are necessary to drive the equilibrium onto the side of the
desired compound 3.
1H NMR (500 MHz, CD2Cl2) δ = 1.27 – 1.53 (m, 9H, HCy), 1.71 – 1.86 (m,
9H, HCy), 1.94 – 2.03 (m, 6H, HCy), 2.17 – 2.26 (m, 6H, HCy), 2.93 (dtt, 3H,
3
3
2JPH = 12.9 Hz, JHH = 12.9 Hz, JHH = 2.7 Hz, PCH(CH2)2), 7.36 (s, 2H,
CHCl3), 8.28 (d, 1H, 2JPH = 1.9 Hz, PCHCl2). 13C NMR (126 MHz, CD2Cl2)
4
2
δ = 25.8 (d, JPC = 1.6 Hz, CCy), 27.3 (d, JPC = 12.1 Hz, CCy), 27.8 (d,
3JPC = 4.2 Hz, CCy), 32.7 (d, JPC = 33.5 Hz, PC(CH2)2), 60.8 (d,
1
1JPC = 41.2 Hz, PCHCl2), 78.1 (s, CH3Cl). 31P NMR (202 MHz, CD2Cl2) δ
= 40.8. FT-IR (cm-1): 2925 (m), 2851 (m), 2804 (w), 2435 (w), 1445 (m),
1252 (m), 1177 (w), 1108 (w), 1085 (w), 1039 (w), 1002 (w), 918 (w), 891
(w), 849 (w), 828 (w), 742 (vs), 701 (w), 659 (m), 622 (w), 531 (m), 523
(m), 502 (w), 474 (w), 449 (w), 425 (w). MS (FD+): m/z (%) 295.27
[(Cy3PCH3)+] (25), 329.23 [(Cy3PCH2Cl)+] (100), 363.19 [(Cy3PCHCl2)+]
(45),
659.45
[{(Cy3PCH3)Cl(Cy3PCH2Cl)}+]
(17),
693.41
729.38
763.33
[{(Cy3PCH2Cl)Cl(Cy3PCH2Cl)}+]
[{(Cy3PCHCl2)Cl(Cy3PCH2Cl)}+]
(65),
(63),
Experimental Section
[{(Cy3PCHCl2)Cl(Cy3PCHCl2)}+] (50). HR-MS (FD+): m/z calcd. for
[(Cy3PCHCl2)+]: 363.17697; found: 363.18914. Anal. calcd. for
[Cy3PCHCl2]Cl  2 CHCl3: C, 39.50; H 5.68. Found: C, 39.64; H, 5.59.
General experimental techniques
All manipulations were performed either under solvent vapor pressure or
dry argon using glovebox and Schlenk techniques if not stated otherwise.
Glassware was flame-dried prior to use. Chlorinated solvents were dried
over CaH2, benzene and toluene over sodium and C6D6 over Na/K-alloy
and distilled prior to use. Tricyclohexylphosphine was purchased from
ABCR and used as received.
[Cy3PCHCl2]3[H3O][H5O2]Cl5  C6D6
(3b):
700 mg
(2.50 mmol)
tricyclohexyl phosphine in 2.5 ml of toluene was added to a mixture of
5.0 ml of toluene and 2.5 ml of CCl4 at 0 °C. The solution turns orange
and the reaction mixture is warmed to ambient temperature and stirred
for one hour. The formed voluminous white precipitate was isolated by
filtration and dried in vacuo to receive a colorless oil which was triturated
with n-pentane. The obtained off-white solid was dried in vacuo and a
sample dissolved under air in non-dried benzene-d6. This sample was
subsequently layered with n-pentane to yield the product as colorless
blocks.
NMR spectroscopy
1H, 13C and 31P NMR spectra were recorded on Bruker Avance III HD
250, Bruker Avance III HD 300 and Avance III 500 NMR spectrometers.
The latter was equipped with
a
Prodigy Cryo-Probe. 1H NMR
1H NMR (500 MHz, CDCl3) δ = 1.22 – 1.38 (m, 27H, HCy), 1.67 – 1.84 (m,
27H, HCy), 1.93 – 2.06 (m, 18H, HCy), 2.20 – 2.34 (m, 18H, HCy), 3.04 (dt,
(300 / 500 MHz) and 13C NMR (76 / 126 MHz) chemical shifts are given
relative to the solvent signal for CDCl3 (7.26 and 77.2 ppm) and CD2Cl2
(5.32 and 53.8 ppm) while 31P (101 / 122 / 202 MHz) used 85% H3PO4 as
an external standard. NMR spectra were processed with the
MestReNova software.[28]
2
3
9H, JPH = 12.7 Hz, JHH = 12.7 Hz, PCH(CH2)2), 7.18 (bs, 8 H, H3O,
H5O2), 8.79 (d, 3H, 2JPH = 1.9 Hz, PCHCl2). 13C NMR (126 MHz, CDCl3) δ
4
2
= 25.4 (d, JPC = 1.7 Hz, CCy), 26.8 (d, JPC = 12.1 Hz, CCy), 27.5 (d,
3JPC = 4.2 Hz, CCy), 32.2 (d, JPC = 33.6 Hz, PC(CH2)2), 60.9 (d,
1
1JPC = 40.3 Hz, PCHCl2). 31P NMR (202 MHz, CDCl3) δ = 40.6.
This article is protected by copyright. All rights reserved.

10.1002/ejic.201800532
European Journal of Inorganic Chemistry
COMMUNICATION
[3]
S. Subramanian, M. J. Zaworotko, Coord. Chem. Rev. 1994, 137, 357–
401.
[Cy3PCH2Cl]Cl (12a): 97.7 mg (0.35 mmol) tricyclohexyl phosphine was
dissolved in 1.50 ml of chloroform, three drops CCl4 were added and the
solution was stirred at ambient temperature for 12 days. Removal of the
volatiles in vacuo yielded 130 mg of a colorless oil which consisted of a
1:1.2 mixture of [Cy3PCHCl2]Cl and [Cy3PCH2Cl]Cl respectively
according to the NMR spectra.
[4]
[5]
A. Pevec, M. Tekavec, A. Demšar, Polyhedron 2011, 30, 549–555.
J. Fuller, R. T. Carlin, H. C. De Long, D. Haworth, Chem. Commun.
1994, 299–300.
[6]
[7]
S. J. Geib, S. C. Hirst, C. Vicent, A. D. Hamilton, Chem. Commun. 1991,
1283–1285.
1H NMR (500 MHz, CD2Cl2) δ = 1.18 – 1.51 (m, 9H, HCy), 1.59 – 2.01 (m,
15H, HCy), 2.08 (d, 6H, 3JPH = 11.6 Hz, HCy), 2.84 (dtt, 3H, 2JPH = 12.8 Hz,
a) S. Subramanian, M. J. Zaworotko, Chem. Commun. 1993, 952–954;
b) S. Subramanian, M. J. Zaworotko, Can. J. Chem. 1993, 71, 433–440.
E. D’Oria, J. J. Novoa, J. Phys. Chem. A 2011, 115, 13114–13123
R. Appel, W. Morbach, Synthesis 1977, 699–700.
3
2
3JHH = 12.8 Hz, JHH = 2.5 Hz, PCH(CH2)2), 5.11 (d, 2H, JPH = 5.6 Hz,
PCH2Cl). 13C NMR (126 MHz, CD2Cl2) δ = 25.91 (d, JPC = 1.5 Hz, CCy),
4
[8]
[9]
26.69 (s, CCy), 26.80 (d3JPC = 2.9 Hz, CCy), 27.10 (d, 2JPC = 12.2 Hz, CCy),
2
3
27.41 (d, JPC = 11.7 Hz, CCy), 27.55 (d, JPC = 3.9 Hz, CCy), 30.56 (d,
1JPC = 38.5 Hz, PC(CH2)2), 35.56 (d, JPC = 60.2 Hz, PCH2Cl). 31P NMR
1
[10] a) R. Appel, F. Knoll, H. Veltmann, Angew. Chem. 1976, 88, 340–341;
b) R. Appel, H. Veltmann, Tetrahedron Lett. 1977, 18, 399–400; c) C. F.
Marth, e-EROS Encyclopedia of Reagents for Organic Synthesis, John
(202 MHz, CD2Cl2) δ = 34.2. FT-IR (cm-1): 2925 (m), 2851 (m), 1579 (w),
1442 (m), 1302 (w), 1260 (m), 1215 (w), 1179 (w), 1159 (s), 1109 (m),
1081 (m), 1040 (m), 1007 (m), 979 (w), 918 (w), 891 (m), 853 (m), 821
(m), 799 (m), 742 (vs), 691 (m), 669 (w), 657 (m), 563 (w), 546 (m), 532
(s), 502 (w), 780 (m), 471 (m), 442 (m), 435 (m). MS (FD+): m/z (%)
295.26 [(Cy3PCH3)+] (27), 329.22 [(Cy3PCH2Cl)+] (100), 659.42
Wiley
&
Sons,
Ltd.,
Chichester,
UK,
chap.
Dichloromethylenetriphenylphosphorane, 2001, 1–2.
[11] Y. Jiang, B. Schirmer, O. Blacque, T. Fox, S. Grimme, H. Berke, J. Am.
Chem. Soc. 2013, 135, 4088–4102.
[{(Cy3PCH3)Cl(Cy3PCH2Cl)}+]
[{(Cy3PCH2Cl)Cl(Cy3PCH2Cl)}+]
(13),
(44),
693.37
729.34
[12] H. Kawai, W. J. Wolf, A. G. DiPasquale, M. S. Winston, F. D. Toste, J.
Am. Chem. Soc. 2016, 138, 587–593.
[{(Cy3PCHCl2)Cl(Cy3PCH2Cl)}+] (6). HR-MS (FD+): m/z calcd. for
[(Cy3PCH2Cl)+]: 329.21594; found: 329.21528.
[13] T. Werner, Adv. Synth. Catal. 2009, 351, 1469–1481.
[14] R. Appel, M. Huppertz, Z. Anorg. Allg. Chem. 1979, 459, 7–14.
[15] S. M. Godfrey, C. A. McAuliffe, R. G. Pritchard, G. Pritchard, J. M.
Sheffield, G. M. Thompson, J. Chem. Soc., Dalton Trans. 1997, 4823–
4828.
NMR scale reactions: 30 mg (0.10 mmol) tricyclohexyl phosphine was
weighed into a NMR tube, 0.50 ml of a 1:1 solvent mixture (CCl4 / C6H6,
CCl4 / CH2Cl2, CCl4 / CHCl3) or neat chloroform respectively were added
and the tube was flame sealed subsequently.
[16] K. Issleb, A. Brack, Z. Anorg. Allg. Chem. 1954, 277, 258–270.
[17] S. M. Godfrey, I. Mushtaq, R. G. Pritchard, J. Chem. Soc., Dalton Trans.
1999, 1319–1323.
MS reaction monitoring: 30 mg (0.10 mmol) tricyclohexyl phosphine
was weighed into a vessel and 0.50 ml of CH2Cl2 and 0.25 ml of CCl4
were added. The reaction mixture was kept at ambient temperature for
the stated amount of time, subsequently diluted with CH2Cl2 and
analyzed via LIFDI mass spectrometry.
[18] S. M. Godfrey, C. A. McAuliffe, R. G. Pritchard, J. M. Sheffield, Chem.
Commun. 1996, 2521–2522.
[19] S. M. Godfrey, C. A. McAuliffe, R. G. Pritchard, J. M. Sheffield, Chem.
Commun. 1998, 921–922.
[20] J. A. Davies, S. Dutremez, A. A. Pinkerton, Inorg. Chem. 1991, 30,
2380–2387.
[21] J. F. Richardson, J. M. Ball, P. M. Boorman, Acta Cryst. C 1986, 42,
1271–1272.
Acknowledgements
[22] E. E. Schweizer, C. J. Baldacchini, A. L. Rheingold, Acta Cryst. C 1989,
45, 1236–1239.
M.R.B. thanks Prof. F. Kraus for moral and financial support as
well as for the provision of lab space. The authors thank the
NMR-, MS- and X-ray departments for their assistance.
[23] a) J. J. Daly, Z. Kristallogr. 1963, 118, 332–333; b) J. J. Daly, J. Chem.
Soc. 1964, 3799–3810.
[24] T. Kawaguchi, K. Tanaka, T. Takeuchi, T. Watanabé, Bull. Chem. Soc.
Jpn. 1973, 46, 62–66.
Keywords: phosphonium • hydrogen bonds • C-H-acidity •
hydronium ion • Zundel ion
[25] D. S. Yufit, J. A. K. Howard, CrystEngComm 2010, 12, 737–741.
[26] T. Steiner, Acta Cryst. B 1998, 54, 456–463.
[27] a) C. Shi, Y. Wang, X. B. Han, W. Zhang, Eur. J. Inorg. Chem. 2017,
3685–3689; b) V. S. Sergienko, A. B. Ilyukhin, A. V. Luzikova, M. A.
Porai-Koshits, Koord.Khim. 1991, 17, 1489–1496.
[1]
a) D. Naglav, B. Tobey, B. Lyhs, B. Römer, D. Bläser, C. Wölper,
G. Jansen, S. Schulz, Angew. Chem. 2017, 129, 8680–8685; b)
B. Neumüller, K. Dehnicke, Z. Anorg. Allg. Chem. 2003, 629, 2529–
2534; c) B. Neumüller, K. Dehnicke, Z. Anorg. Allg. Chem. 2004, 630,
1374–1376; d) B. Neumüller, K. Dehnicke, Z. Anorg. Allg. Chem. 2004,
630, 1846–1850; e) B. Neumüller, K. Dehnicke, Z. Anorg. Allg. Chem.
2006, 632, 931–933; f) R. Puchta, B. Neumüller, K. Dehnicke, Z. Anorg.
Allg. Chem. 2009, 635, 1196–1199; g) R. Tonner, G. Frenking,
B. Neumüller, K. Dehnicke, Z. Anorg. Allg. Chem. 2007, 633, 1183–
1188.
[28] MestReNova, Mestrelab Research S.L., Santiago de Compostela,
Spain, 2011.
[29] OPUS, Bruker Optik GmbH, Ettlingen, Germany, 2009.
[30] a) X-Area. Stoe & Cie GmbH, Darmstadt, Germany, 2011; b) X-Shape.
Stoe & Cie GmbH, Darmstadt, Germany, 2009; c) X-Red32. Stoe & Cie
GmbH, Darmstadt, Germany, 2009.
[31] a) G. M. Sheldrick, SHELXS-2013/1, Göttingen, Germany, 2013; b) G.
M. Sheldrick, SHELXL-2016/4, Göttingen, Germany, 2016; c) C. B.
Hübschle, G. M. Sheldrick, B. Dittrich, J. Appl. Crystallogr. 2011, 44,
1281–1284.
[2]
A. Bernsdorf, M. Köckerling, Z. Kristallogr. - New Cryst. Struct. 2012,
227, 85–86.
This article is protected by copyright. All rights reserved.

10.1002/ejic.201800532
European Journal of Inorganic Chemistry
COMMUNICATION
Scheme 1. Reaction of n-propyl diphenylphosphine with CCl4 in non-polar aprotic solvents described by Appel and Huppertz.[14]
Table 1. Summary of observed cations in LIFDI mass spectrometry (FD+ ionization mode) and their relative signal intensities in the reaction solutions of PCy3
with benzene / CCl4, dichloromethane / CCl4, chloroform / CCl4 mixtures and with neat chloroform after two weeks reaction time.
Relative signal intensities / %
Ion
m / z
C6H6 / CCl4
CH2Cl2 / CCl4
CHCl3 / CCl4
CHCl3
[Cy3PCH3]+
295.25
329.22
363.18
397.14
659.42
693.41
729.38
763.33
51
100
81
8
10
100
48
2
25
100
45
2
100
5
[Cy3PCH2Cl]+
[Cy3PCHCl2]+
0
[Cy3PCCl3]+
0
{[Cy3PCH3]Cl[Cy3PCH2Cl]}+
{[Cy3PCH2Cl]Cl[Cy3PCH2Cl]}+
{[Cy3PCH2Cl]Cl[Cy3PCHCl2]}+
{[Cy3PCHCl2]Cl[Cy3PCHCl2]}+
15
37
66
70
3
17
65
63
50
2
32
51
43
0
0
0
This article is protected by copyright. All rights reserved.

10.1002/ejic.201800532
European Journal of Inorganic Chemistry
COMMUNICATION
Entry for the Table of Contents (Please choose one layout)
Layout 1:
COMMUNICATION
The functional phosphonium ion
[Cy3PCHCl2]+ could be synthesized
which is able to form hydrogen bonds
to the corresponding anion. Through
these interactions salts
[Cy3PCHCl2]Cl · 2CHCl3 (3a) and
[Cy3PCHCl2]3[H3O][H5O2]Cl5  C6D6
could be stabilized. Also the
Crystallization assistance*
Nils Spang, Matthias Müller, Magnus R.
Buchner*
Page No. – Page No.
The phosphonium ion [Cy3PCHCl2]+:
synthesis and properties
mechanism for the formation of cation
[Cy3PCHCl2]+ has been investigated.
*one or two words that highlight the emphasis of the paper or the field of the study
This article is protected by copyright. All rights reserved.