On Pentakis(pentafluoroethyl)stannate, [Sn(C2F5)5]?, and the Gas-Free Generation of Pentafluoroethyllithium, LiC2F5

Article abstract of DOI:10.1002/chem.201704807

Pentafluoroethyllithium, LiC₂F₅, has been established as an efficient and versatile reagent for the transfer of the pentafluoroethyl unit to a number of electrophiles. Here, the stability of this species up to ?40 °C is of advantage, particularly in comparison to its smaller congener LiCF₃. The usual production of LiC₂F₅, however, from gaseous HC₂F₅ or IC₂F₅ and strong bases requires specially designed apparatuses, which severely impeded its value as a laboratory reagent. In this contribution we communicate an alternative gas-free and highly efficient protocol for the synthesis of LiC₂F₅ from the already commercialized stannate salt [PPh₄][Sn(C₂F₅)₅]. The [Sn(C₂F₅)₅]^? anion represents not only the first example of a structurally characterized hypervalent pentaalkylstannate but also serves as a precursor for the synthesis of the homoleptic tetrakis(pentafluoroethyl)stannane, Sn(C₂F₅)₄. The reaction of the latter with n-butyllithium provides an insight into the mechanism of LiC₂F₅ generation.

Full text of DOI:10.1002/chem.201704807

A Journal of
Accepted Article
Title: On Pentakis(pentafluoroethyl)stannate, [Sn(C2F5)5]-, and the
gas-free Generation of Pentafluoroethyllithium, LiC2F5
Authors: Markus Wieseman, Johannes Klösener, Beate Neumann,
Hans-Georg Stammler, and Berthold Hoge
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: Chem. Eur. J. 10.1002/chem.201704807
Link to VoR: http://dx.doi.org/10.1002/chem.201704807
Supported by

10.1002/chem.201704807
Chemistry - A European Journal
FULL PAPER
On Pentakis(pentafluoroethyl)stannate, [Sn(C2F5)5]-, and the gas-
free Generation of Pentafluoroethyllithium, LiC2F5
Markus Wiesemann, Johannes Klösener, Beate Neumann, Hans-Georg Stammler and
Berthold Hoge*
[10,11]
[1]
Abstract: Pentafluoroethyllithium, LiC2F5, has been established as an
efficient and versatile reagent for the transfer of the pentafluoroethyl
unit to a number of electrophiles. Here the stability of this species up
to -40 °C is of advantage, particularly in comparison to its smaller
congener LiCF3. The usual production of LiC2F5, however, from
gaseous HC2F5 or IC2F5 and strong bases requires specially designed
apparatuses, which severely impeded its value as a laboratory
reagent. In this contribution we communicate an alternative gas-free
and highly efficient protocol for the synthesis of LiC2F5 from the
already commercialized stannate salt [PPh4][Sn(C2F5)5]. The
C2F4
,
liquid
adducts
of
the
type
D∙IC2F5 ,
pentafluoroethylpropionate[12]
,
pentafluoroethyl sulfones[13] as
well as the fluoride catalysed pentafluoroethylation with
Me3SiC2F5 are described.[14] Additionally, an efficient preparation
of LiC2F5 by direct deprotonation of HC2F5 was established by
Röschenthaler et al..[15] However, in these protocols the
moderately stable and highly reactive LiC2F5 was generated from
cumbersome gaseous starting materials or replaced by less
reactive alternatives.
In this paper we like to present the gas-free synthesis for the
LiC2F5 starting from solid [PPh4][Sn(C2F5)5] as LiC2F5 “reservoir”,
which is now readily accessible and through the results of this
work commercially available.[16]
[Sn(C2F5)5]- anion represents not only the first example of
structurally characterized hypervalent pentaalkylstannate but also
serves as precursor for the synthesis of the homoleptic
a
a
tetrakis(pentafluoroethyl)stannane, Sn(C2F5)4. The reaction of the
latter with n-butyllithium provides an insight into the mechanism of
LiC2F5 generation.
Results and Discussion
A
general method for the preparation of otherwise
inaccessible organolithium compounds is based upon the lithium-
tin exchange with tetraorganostannanes.[17] In keeping with this,
tetrakis(pentafluoroethyl)stannane, Sn(C2F5)4, has to be
envisaged as a promising precursor for LiC2F5. In a similar
reaction P(C2F5)3 was already used for the generation of
LiC2F5.[18]
First evidence for the existence of this species was taken
from the treatment of chlorotris(pentafluoroethyl)stannane with
one equivalent of in situ generated LiC2F5 in dimethyl ether.
This approach, however, was discarded as the starting
Introduction
One important aspect in the chemistry of fluoroorganic species
concerns the ready availability of suitable methods for the
introduction of perfluoroalkyl groups. In particular, for the transfer
of trifluoromethyl groups the tedious handling of gaseous
precursors must be overcome.[1] Therefore a whole series of
commercially available and easy-to-handle trifluoromethylation
reagents comprising the Ruppert-Prakash reagent (Me3SiCF3)[2,3]
,
material required
a
multi-step synthesis which resisted
trifluoromethylcuprates[4], the Langlois and Baran reagent[5] or the
Umemoto and Togni reagent[6] were established, which allow
nucleophilic, radical or electrophilic trifluoromethylation
reactions.[7] From a formal point of view trifluoromethyllithium,
LiCF3, may be regarded as the most simple nucleophilic transfer
reagent of the trifluoromethyl fragment. This compound however,
is notoriously unstable, even at low temperatures, which
obviously limits its scope as a synthetic reagent.[3,8]
upscaling.[19] An alternative was found with the employment of
SnCl4 as a precursor for Sn(C2F5)4. The reaction of an excess of
SnCl4 with an ethereal solution of LiC2F5 did not furnish the
anticipated mixture of pentafluoroethyltin chlorides, ClnSn(C2F5)4-
(n
=
0-4), but led to the selective formation of
n
[Li(OEt2)n][Sn(C2F5)5]. This result was rationalized by the initial
formation of soluble species of the form ClnSn(C F ) (n = 1-3),
n
5 4-
2
which were preferentially converted into the final product,
whereas a considerable amount of poorly soluble SnCl4 etherate
remained in the reaction mixture.[20] [Li(OEt2)n][Sn(C2F5)5] is not
stable in ethereal media and slowly decomposes to Sn(C2F5)4.
This reaction was optimized by treatment of [Li(OEt2)n][Sn(C2F5)5]
with HCl and refluxing the mixture for 48 h in chloroform. By this,
a straightforward two-step synthesis of Sn(C2F5)4 was established,
which was easily scaled up to 14 g (Scheme 1).
In comparison to this, reagents for pentafluoroethylation are
less developed, despite useful properties of pentafluoroethylated
molecules for medicinal issues.[9] Common synthetic protocols
largely mirror the corresponding trifluoromethyl chemistry. Thus,
pentafluoroethylation starting from gaseous XC2F5 (X = H, I),
Dr. M. Wiesemann, Dr. J. Klösener, B. Neumann, Dr. H.-G.
Stammler, Prof. Dr. B. Hoge
Centrum für Molekulare Materialien
Fakultät für Chemie, Universität Bielefeld,
Universitätsstraße 25, 33615 Bielefeld (Germany)
E-Mail: b.hoge@uni-bielefeld.de
This article is protected by copyright. All rights reserved.

10.1002/chem.201704807
Chemistry - A European Journal
FULL PAPER
- rt
-80 °C
2. HCl
1. Et
2O,
of the by-products n-Bu Sn and n-BunSn(C F ) (n = 1-3) was
readily achieved by recrystallization or distillation (Scheme. 2).
n
2 5 4-
4
+
+
"[
F
5 5]"
)
SnCl4
n
5 LiC2F5
H(OEt2) ][Sn(C2
-
5 LiCl
-
CHCl3
reflux, 48
HC2F5
- n
+
Ph
3SnCl
h
Et
2O
Ph
F5
)
3Sn(C2
52
-
LiCl
[a]
%
F
F5
F5
5C2 C2
n
+
-
4
n
-BuLi
F
F5
F5
5C2 C2
Sn
4 LiC2F5
Sn
-Bu
4Sn
F
5C2 C2
F
5C2 C2
+
N)
2PCl
(Et2
N)2PC2F5
(Et2
-
LiCl
Scheme 1. Synthesis of tetrakis(pentafluoroethyl)stannane from SnCl4 and
LiC2F5.
[a]
52
%
Scheme 2. LiC2F5 generation from Sn(C2F5)4 with subsequent
pentafluoroethylation of Ph3SnCl and (Et2N)2PCl. [a] isolated yield.
In the 19F NMR spectrum of Sn(C2F5)4 two signals appear
at -82.9 ppm and -111.4 ppm for the CF3 and CF2 units,
respectively. The 2J(F,Sn) coupling constant of 380 Hz in the high
field resonance as well as a nonet in the 119Sn NMR spectrum at
-388.7 ppm agree with the presence of four pentafluoroethyl
substituents. The molecular structure in the solid state was
elucidated by X-ray diffraction, whereby in situ crystallization of
the compound in a glas capillary was performed (Figure 1). The
molecule exhibits a distorted tetrahedral geometry with an
average Sn-C bond length of 220 pm comparable to those in non-
fluorinated tetraalkyltin compounds.[21]
Having reinforced the efficiency of our novel synthetical method
for LiC2F5 we tried to get a mechanistic insight into this process
by low temperature NMR technique. A mixture of Sn(C2F5)4 with
4.3 equivalents of n-butyllithium at -60 °C shows two signals for
the C2F5 groups in the 19F NMR spectrum (Figure 2). The absence
of tin satellites suggests that the C2F5 group is no longer linked to
a tin atom and that LiC2F5 is formed. Consistently one equivalent
of Sn(C2F5)4 allows the generation of four equivalents of LiC2F5.
Figure 2. 19F NMR spectrum of LiC2F5, obtained from the reaction of Sn(C2F5)4
with 4.3 equivalents of n-butyllithium in diethyl ether at -60 °C.
When a solution of Sn(C2F5)4 was titrated with an n-butyllithium
solution at -50 °C no clean reaction occurred. After the
combination of Sn(C2F5)4 with one equivalent of n-butyllithium a
mixture of all possible stannanes, n-BunSn(C2F5)4-n (n = 0-4) and
even n-Bu4Sn was observed. Another important aspect was the
detection of resonances of [Sn(C2F5)5]-. This anionic species was
obviously formed in a considerable amount as a by-product. It is
conceivable that after the addition of a first n-butyl unit to the
stannane, one C2F5 group was transferred from the transient
stannate to free Sn(C2F5)4 (Scheme 3).
Figure 1. Molecular structure of Sn(C2F5)4. The asymmetric unit contains two
structurally independent Sn(C2F5)4 units (Just the non-disordered is shown).
Thermal ellipsoids are shown at 50 % probability. Selected bond lengths [pm]
and angles [°]: Sn-C1 220.1(3), Sn-C3 220.5(3), Sn-C5 220.4(3), Sn-C7
220.6(3), C1-Sn-C3 116.8(1), C1-Sn-C5 107.5(1), C1-Sn-C7 108.6(1), C3-Sn1-
C5 109.3(1), C3-Sn-C7 106.0(1), C5-Sn-C7 108.5(1).
Encouraged by the ready availability of Sn(C2F5)4 we performed
first orientating pentafluoroethylation studies on the gas-free
generation of LiC2F5 by combining Sn(C2F5)4 and n-butyllithium at
-60 °C. The so produced LiC2F5 was quenched with Ph3SnCl or
(Et2N)2PCl disclosing selectivities like LiC2F5 samples, which
have been generated from HC2F5 and n-butyllithium. The removal
This article is protected by copyright. All rights reserved.

10.1002/chem.201704807
Chemistry - A European Journal
FULL PAPER
F5
C2
5C2 Sn
C2
F
F5
F5
5C2 C2
F5
F5
C2
C2
F5
n
+
-BuLi
+
n
+
+
2
...
F5 3
-BuSn(C2
F
Sn
)
Li
F
5C2 C2
-
"
"
n
+
+
Sn(C2F5
-BuLi
)
4
F5
C2
F5
F5
C2
Li+
F
5C2 Sn
C2
n
-Bu
Scheme 3. [Li(OEt2)n][Sn(C2F5)5] formation in the reaction of n-butyllithium with
an excess of Sn(C2F5)4.
Taking the former NMR spectroscopic results into account leads
to the intriguing disclosur, that [Li(OEt2)n][Sn(C2F5)5] also
represents a source of LiC2F5.
Clearly the chemistry of this species merits an investigation
in more detail. Like almost all penta- and hexacoordinated
perorganostannates,
solutions
of
[Li(OEt2)n][Sn(C2F5)5],
Figure 3. Molecular structure of the anion of [Li(12-crown-4)2][Sn(C2F5)5]. Two
C2F5 groups containing the C5 and C9 atom are disordered and refined
isotropically (ratio 1:1). Thermal ellipsoids are shown at 50 % probability.
Selected bond lengths [pm]: Sn-C1 227.8(3), Sn-C3 230.2(4), Sn-C5 218.8(15),
Sn-C7 240.8(5), Sn-C9 227.1(7).
accessible by direct pentafluoroethylation of SnCl4, suffer from
decomposition. The complete decomposition, however, takes
days. In the 19F NMR spectrum in diethyl ether no discrete signals
for the equatorial and axial C2F5 groups are resolved. Instead only
two resonances at -80.3 and -110.9 ppm for the CF3 and CF2
groups are observed in accordance with a highly fluctional
Beside complexation with crown ether the combination of
[PPh4]Cl with in situ generated [Li(OEt2)n][Sn(C2F5)5] afforded a
stable and isolable [Sn(C2F5)5] salt after filtration and removal of
the solvent (Scheme 4).
structure. It
is known from
previous studies
on
[Li(OEt2)n][Si(C2F5)3] that the lithium cation is a not innocent and
facilitates decomposition.[22] Complexation with 12-crown-4 as
well as salt metathesis with [PPh4]Cl allows the isolation of the
corresponding [Sn(C2F5)5]- salts. In the solid state, the anion of
[Li(12-crown-4)2][Sn(C2F5)5] displays the geometry of a severely
distorted trigonal bipyramide with varying Sn-C bond length
(218.8(15) pm to 240.8(5) pm) (Figure 3). The average Sn-C
bond length (229 ppm) is elongated in comparison to the Sn-C
bond length in Sn(C2F5)4 (220 ppm). Notably, the [Sn(C2F5)5]-
anion is a rare example of hypervalent tin compounds with only
carbon based substituents and represents the first example of a
structural characterized pentaalkylstannate anion.[23]
- rt
-80 °C
[PPh4]Cl
1. Et
2.
2O,
+
+
F5 5
[PPh4][Sn(C2
SnCl4
5 LiC2F5
]
)
-
5 LiCl
Scheme 3. Synthesis of [PPh4][Sn(C2F5)5] by pentafluoroethylation of SnCl4.
[PPh4][Sn(C2F5)5] is perfectly suitable for a gas-free generation of
LiC2F5. It is (i) readily accessible in a one-pot reaction in yields up
to 24 g, (ii) easily isolated by one single filtration, (iii) storable up
to months in an atmosphere of dinitrogen. It may also be handled
in air for a short time. These comfortable characteristics and its
accessibility, which are presented in this work, lead to the
commercialization of [PPh4][Sn(C2F5)5].[16]
Now
pentafluoroethylation
reactions
using
[PPh4][Sn(C2F5)5] were effected by the addition of n-butyllithium
in diethyl ether at -60 °C and the subsequent addition of suitable
electrophiles (Ph2CO, PhCHO, (Et2N)2PCl).[11,24,25] In the 19F-NMR
spectra of the crude product mixtures a complete substitution of
the C2F5 groups is observed. However, for a more readily workup
an excess of the pentafluoroethylation reagent was used. At
temperatures above -40 °C the remaining [cat][C2F5] (cat = Li+,
[PPh4]+) decomposes to HC2F5, tetrafluoroethylene and the
corresponding insoluble fluoride salt. The less hazardous by-
product n-Bu4Sn can be removed by sublimation and
recrystallization, distillation or silica gel column chromatography
(Scheme 5).
This article is protected by copyright. All rights reserved.

10.1002/chem.201704807
Chemistry - A European Journal
FULL PAPER
+
+
4 Ph2CO
HCl/H2O
Ph
Ph
stream and afterwards chilling to 100 K within 15 min. The crystals were
kept at 100.0(1) K during data collection. One of the two Sn(C2F5)4
molecules shows a disorder of two of the four C2F5 ligands in the ratio of
85:15. The anisotropic displacement parameters of the disordered atoms
were pairwisely constrained to be same, their C-C distances were
restrained to be same. The crystal of the [Li(12-crown-4)2][Sn(C2F5)5]
contains a partly disordered anion, two of the five C2F5-groups are
disordered at two position with ratio 1:1. The disordered atoms were
refined isotropically. All chemical equivalent bonds were restrained to be
same within the anion. Two 12-crown-4 molecules are bounded to the
lithium cation, both ones are heavily disordered, no reasonable model for
the disorder could be found, so the "squeeze" routine from OLEX2 was
used. The two 12-crown-4 ligands were included into sum formula and
depending values. The structure model is surely "on the edge", but at least
it confirms the structure of the anion, also if the bond lengths and angles
are minor reliably. The crystal exhibit an inversion twinning with ratio 1:1.
The structures were solved using Olex2[26] and refined with the ShelX
program package[27] using direct methods and least-squares minimization.
Details of the X-ray investigation are given in Table. 1. CCDC 1562131
(Sn(C2F5)4) and 1562132 ([Li(12-crown-4)2][Sn(C2F5)5]) contain the
supplementary crystallographic data for this paper. These data can be
obtained free of charge from the Cambridge Crystallographic Data Centre
via www.ccdc.ac.uk/data_request/cif.
4
HO
F5
C2
-
4 LiCl
-
F5
[PPh4]C2
52 %[a]
n
+
4
-BuLi
-60 °C
+
+
4 PhCHO
HCl/H2O
OH
4 LiC2F5
Et
2O,
+
F
[PPh4][Sn(C2 5)5]
4
-
n
F5
C2
-Bu4Sn
-
4 LiCl
F5
[PPh4]C2
-
F5
[PPh4]C2
34 %[a]
Et2N
Et2N
+
-
4
N)2PCl
(Et2
4
P
F5
C2
-
4 LiCl
F5
73 %[a]
[PPh4]C2
Scheme 5. Selected reactions of pentafluoroethyllithium, LiC2F5, made from
[PPh4][Sn(C2F5)5]. [a] isolated yields.
Conclusions
In conclusion, we presented a gas-free protocol for the generation
of the highly reactive pentafluoroethyllithium, LiC2F5, by tin-lithium
transmetallation.
[PPh4][Sn(C2F5)5]
The
is
already
readily accessible
commercialized[16]
by direct
pentafluoroethylation of SnCl4 and subsequent salt metathesis
with [PPh4]Cl. The efficiency of this gas-free LiC2F5 generation
was documented by the pentafluoroethylation of (Et2N)2PCl,
Ph2CO and PhCHO. The by-product n-Bu4Sn can be removed by
sublimation and recrystallization, distillation as well as silica gel
column chromatography. The electron withdrawing effect of five
Caution: LiC2F5 is highly reactive and tends to
decompose violently at temperatures above -40 °C.
Synthesis of tetrakis(pentafluoroethyl)stannane: HC2F5 (250 mmol)
was condensed onto
a stirred solution of n-butyllithium (97.4 g,
229.18 mmol, 1.6 M in n-hexane) in diethyl ether (500 mL) at -80 °C. After
stirring for 20 min SnCl4 (13.36 g, 51.28 mmol) was added and the
suspension was allowed to reach room temperature overnight. The two
phase system was concentrated under reduced pressure until the upper
phase had vanished. Gaseous HCl (50 mmol) was condensed (-196 °C)
onto the residue. After stirring for 30 min at room temperature all volatile
compounds were removed in high vacuum to obtain a colorless sluggish
residue which was suspended in chloroform (50 mL). After refluxing for
48 h all volatile compounds were removed in high vacuum to obtain two
clear phases in the volatile fraction. After phase separation the lower
phase was fractionally distilled to obtain the product as a colorless liquid
(14.64 g, 24.61 mmol, 54 %). Vapor pressure (22 °C) = 10 mbar. 13C{19F}
NMR ([D3]acetonitrile, 298 K): δ=126.3 (s, 1J(C,Sn)=706/737 Hz; CF2),
119.6 ppm (s, 2J(C,Sn)=97/101 Hz; CF3); 19F NMR ([D3]acetonitrile,
pentafluoroethyl groups lends
a sufficient stability of the
[Sn(C2F5)5]- anion to allow an X-ray structural analysis. The
[Sn(C2F5)5]- anion is not only the first example of a structurally
characterized hypervalent pentaalkylstannate but also serves as
a
precursor
for
the
synthesis
of
the
tetrakis-
(pentafluorethyl)stannane, Sn(C2F5)4. The reaction of the latter
with n-butyllithium provided an insight into the mechanism of the
LiC2F5 generation.
Experimental Section
2
All chemicals were obtained from commercial sources and used without
further purification. Standard high-vacuum techniques were employed
throughout all preparative procedures. Nonvolatile compounds were
handled in a dry N2 atmosphere using Schlenk techniques. The NMR
spectra were recorded on a Bruker Model Avance III 300 spectrometer (1H
300.13 MHz; 19F 282.40 MHz; 31P 121.49 MHz; 119Sn 111.92 MHz; 13C
75.47 MHz) with positive shifts being downfield from the external
standards, (85 %) H3PO4 (31P), CCl3F (19F), TMS (13C, 1H), SnMe4 (119Sn)).
The NMR spectra were recorded in the indicated deuterated solvent or in
relation to [D6]acetone filled capillaries. IR spectra were recorded on an
ALPHA-FT-IR spectrometer (Bruker). ESI mass spectra were recorded
using an Esquire 3000 ion-trap mass spectrometer (Bruker Daltonik GmbH,
Bremen, Germany) equipped with a standard ESI/APCI source. EI mass
spectra were recorded using an Autospec X magnetic sector mass
spectrometer with EBE geometry (Vacuum Generators, Manchester, UK)
equipped with a standard EI or CI source. Melting points were measured
on a Mettler Toledo Mp70 Melting Point System. Vapor pressures were
determined with a VAP 5 (Vacuubrand), a piezo vacuum gauge. The
crystal data were collected on an Agilent Supernova diffractometer using
Mo-Kα radiation (λ = 71.073 pm). Single crystals of Sn(C2F4)4 were in situ
grown at 200 K by translation of the capillary perpendicular to the cold
298 K): δ=-82.9 (s, 12F; CF3), -111.4 ppm (s, J(F,Sn)=380 Hz, 8F; CF2);
119Sn{1H} NMR ([D3]acetonitrile, 298 K): δ=-388.7 ppm (nonet,
2J(Sn,F)=385 Hz); 119Sn{19F} NMR ([D3]acetonitrile, 298 K): δ=-388.8 ppm
(s); MS (EI, 70 eV, pos.) {m/z (%) [assignment]}: 476.9 (1) [Sn(C2F5)3]+,
376.9 (48) [Sn(C2F5)2F]+, 276.9 (19) [Sn(C2F5)F2]+, 138.9 (85) [SnF]+,
~
100.0 (100) [C2F4]⋅+, 69.0 (16) [CF3]+; IR (gas phase): ν=1321 (s), 1300
(m), 1230 (s), 1121 (s), 939 (m), 743 (m), 608 (w), 589 (w), 536 (w) cm-1.
Generation of LiC2F5 from tetrakis(pentafluoroethyl)stannane: In a
Young valve NMR tube Sn(C2F5)4 (0.08 g, 0.13 mmol) was combined with
n-butyllithium (0.24 g, 0.56 mmol, 1.6 M in n-hexane) in diethyl ether
(1 mL) at -196 °C. The resulting solution was NMR spectroscopically
investigated at -60 °C. 19F NMR (diethyl ether/[D6]acetone, 298 K): δ=-84.5
(m, 3F; CF3), -127.3 (q, 3J(F,F)=8 Hz, 2F; CF2), -132.2 ppm (s, 0.07F;
C2F4); 1H,119SnH HMBC NMR (diethyl ether/[D6]acetone, 298 K): δ=1.2/-
10.4 ppm (n-Bu4Sn).
Synthesis
of
triphenyl(pentafluoroethyl)stannane
from
tetrakis(pentafluoroethyl)stannane: Sn(C2F5)4 (0.65 g, 1.09 mmol) was
condensed onto a solution of n-butyllithium (0.93 g, 2.19 mmol, 1.6 M in n-
hexane) in diethyl ether (50 mL) at -196 °C. After stirring for 4 h at -60 °C
This article is protected by copyright. All rights reserved.

10.1002/chem.201704807
Chemistry - A European Journal
FULL PAPER
Ph3SnCl (0.84 g, 2.18 mmol) was added and the suspension was allowed
to reach room temperature overnight. After filtration all volatile compounds
were removed. After recrystallization from toluene the product was
0.80 mmol, 40 %, purity 90%). 1H NMR (CH2Cl2/[D6]acetone, 298 K):
δ=3.58 ppm (s, 16H; 12-crown-4); 13C{1H} NMR (CH2Cl2/[D6]acetone,
298 K): δ=67.5 (s; 12-crown-4); 13C{19F} NMR (CH2Cl2/[D6]acetone,
298 K): δ=129.0 (s, 1J(C,Sn)=485/508 Hz; CF2), 121.0 ppm (s,
2J(C,Sn)=78/81 Hz; CF3); 19F NMR (CH2Cl2/[D6]acetone, 298 K): δ=-80.3
(s, 15F; CF3), -111.2 ppm (s, 2J(F,Sn)=319 Hz, 10F; CF2); 119Sn{19F} NMR
(CH2Cl2/[D6]acetone, 298 K): δ=-417.2 (s).
obtained as
a
colorless solid (0.53 g, 1.13 mmol, 52 %). 1H NMR
([D]chloroform, 298 K): δ=7.8-7.4 ppm (m, 15H; Ar-H); 19F NMR
([D]chloroform, 298 K): δ=-82.1 (t, 3J(F,F)=2 Hz, 3F; CF3), -116.4 ppm (q,
3J(F,F)=2 Hz, 2J(F,Sn)=228/237 Hz, 2F; CF2); 119Sn{1H} NMR
([D]chloroform, 298 K): δ=-149.9 ppm (t, 2J(Sn,F)=238 Hz).[19]
Synthesis of bis(diethylamino)(pentafluoroethyl)phosphane from
[PPh4][Sn(C2F5)5] and separation of n-Bu4Sn by (i) distillation:
[PPh4][Sn(C2F5)5] (4.96 g, 4.71 mmol) and n-butyllithium (9.20 g, 13.5 mL,
21.6 mmol, 1.6 M in n-hexane) were combined in diethyl ether (50 mL) at
-60 °C to obtain an orange solution. After stirring for 20 min at this
temperature (Et2N)2PCl (3.88 g, 18.42 mmol) was added. The suspension
was stirred overnight and was allowed to reach room temperature.
Removing all volatile compounds at a reduced pressure furnished a black
oily residue. At 150 °C all low-volatile compounds were removed in high
vacuum (1x10-3 mbar) to obtain a brown oil. After distillation (47 °C at
10-3 mbar) the product was obtained as a colorless liquid (3.94 g,
13.39 mmol; 73 %). In the NMR-spectra the resonances for (Et2N)2PC2F5
were detected (see top). The n-Bu4Sn remains in the residue.
Synthesis of bis(diethylamino)(pentafluoroethyl)phosphane from
tetrakis(pentafluoroethyl)stannane: Sn(C2F5)4 (2.65 g, 4.46 mmol) in
diethyl ether (50 mL) was combined with n-butyllithium (7.27 g,
17.11 mmol, 1.6 M in n-hexane) at -60 °C. After stirring for 20 min at -60 °C
(Et2N)2PCl (3.62 g, 17.18 mmol) was added. The colorless suspension
was allowed to reach room temperature overnight. After removing all highly
volatile compounds under reduced pressure the residue was fractionally
distilled in high vacuum (25 °C at 1x10-3 mbar) to obtain the product as a
colorless liquid (2.64 g, 8.97 mmol, 52 %). 1H NMR ([D]chloroform, 298 K):
δ=3.19 (m, 8H; CH2), 1.11 ppm (t, 3J(H,H)=7.2 Hz, 12H; CH3); 13C{1H}
NMR ([D]chloroform, 298 K): δ=44.2 (d, 2J(C,P)=20 Hz; CH2), 14.1 ppm (d,
3J(C,P)=3 Hz; CH3); 13C{19F} NMR ([D]chloroform, 298 K): δ=120.1 (d,
2J(C,P)=25 Hz; CF3), 119.5 (d, 1J(C,P)=52 Hz; CF2), 44.2 (t, q, d,
1J(C,H)=136 Hz, 2J(C,H)=4 Hz, 2J(C,P)=20 Hz; CH2), 14.1 ppm (q, t, d,
1J(C,H)=126 Hz, 2J(C,H)=3 Hz, 3J(C,P)=3 Hz; CH3); 19F NMR
Synthesis of
2,2,3,3,3-pentafluoro-1,1-diphenylpropan-1-ol from
[PPh4][Sn(C2F5)5] and separation of n-Bu4Sn by (ii) sublimation and
recrystallization: [PPh4][Sn(C2F5)5] (5.11 g, 4.85 mmol) and n-
butyllithium (8.00 g, 11.8 mL, 18.8 mmol, 1.6 M in n-hexane) were
combined in diethyl ether (50 mL) at -60 °C to obtain an orange solution.
After stirring for 20 min at this temperature benzophenone (3.35 g,
18.38 mmol) was added. The solution was stirred overnight and was
allowed to reach room temperature. Aqueous HCl (100 mL; 0.5 M) was
added to the black solution, which decolored within minutes. After phase
separation and extraction of the aqueous phase with diethyl ether
(2x50 mL) the combined diethyl ether solutions were washed with water
and dried over MgSO4. Filtration and solvent separation under reduced
pressure furnished a clear oil. After sublimation (140 °C at 1x10-3 mbar)
and recrystallization from n-heptane and the product was obtained as a
colorless solid (2.87 g, 9.50 mmol; 52 %). M.p.: 84 °C; 1H NMR
([D]chloroform, 298 K): δ=7.58 (m, 4H; Ar-H), 7.36 (m, 6H; Ar-H), 2.87 ppm
(s, 1H; OH); 13C{1H} NMR (D]chloroform, 298 K): δ=139.8, 128.4, 128.2 (s;
arom. C), 127.1 (t, J(C,F)=2 Hz; arom. C), 78.8 ppm (t, 2J(C,F)=24 Hz;
COH); 13C{19F} NMR ([D]chloroform, 298 K): δ=119.1 (s; CF3), 115.3 ppm
(s; CF2); 19F NMR ([D]chloroform, 298 K): δ=-77.1 (s, 3F; CF3), -116.4 (s,
([D]chloroform, 298 K): δ=-81.8 (d, m, 3J(F,P)=22 Hz, 3F; CF3),
-
117.6 ppm (d, 2J(F,P)=72 Hz, 2F; CF2); 31P{1H} NMR ([D]chloroform,
298 K): δ=72.5 ppm (t, q, 2J(P,F)=72 Hz, 3J(F,P)=22 Hz).[25]
Synthesis of tetraphenylphosphoniumpentakis(pentafluoroethyl)-
stannate: A solution of n-butyllithium (67.67 g, 159 mmol, 1.6 M in n-
hexane) in diethyl ether (500 mL) was cooled to -80 °C and degassed.
HC2F5 (175 mmol) was condensed onto the solution. After stirring for
20 min SnCl4 (10.14 g, 38.92 mmol) was added dropwise. The colorless
suspension was stirred overnight and allowed to reach ambient
temperature. [PPh4]Cl (12.47 g, 33.27 mmol) was added and the
suspension was stirred for additional 24 h. After filtration all volatile
compounds were removed in high vacuum. The product was obtained as
a colorless solid (24.19 g, 22.97 mmol, 72 %). M.p: 95 °C; 1H NMR
([D]chloroform, 298 K): δ=7.91 (m, 4H; Ar-H), 7.75 (m, 8H; Ar-H), 7.60 ppm
(m, 8H; Ar-H); 13C{1H} NMR (D]chloroform, 298 K): δ=135.8 (d,
4J(C,P)=3 Hz; para-C), 134.2 (d, 2J(C,P)=10 Hz; ortho-C), 130.7 (d,
3J(C,P)=13 Hz; meta-C), 117.4 ppm (d, 1J(C,P)=90 Hz; ipso-C); 13C{19F}
NMR ([D]chloroform, 298 K): δ=129.0 (s, 1J(C,Sn)=483/508 Hz; CF2),
121.0 ppm (s, 2J(C,Sn)=79/83 Hz; CF3); 19F NMR ([D]chloroform, 298 K):
δ=-79.8 (m, 15F; CF3), -110.9 ppm (m, 2J(F,Sn)=318 Hz, 10F; CF2);
119Sn{1H} NMR ([D]chloroform, 298 K): δ=-417.3 ppm (undecet (only nonet
resolved), 2J(Sn,F)=322 Hz); 119Sn{19F} NMR ([D]chloroform, 298 K): δ=-
417.3 ppm (s); MS (ESI, pos.) {m/z (%) [assignment]}: 339.2 (100) [PPh4]+;
MS (ESI, neg.) {m/z (%) [assignment]}: 982.5 (33), 714.7 (88) [Sn(C2F5)5]-,
~
2F; CF2); IR (ATR): ν=3533 (m), 3067 (w), 1600 (w), 1495 (w), 1450 (w),
1354 (w), 1332 (w), 1285 (w), 1220 (s), 1199 (s), 1170 (s), 1156 (s), 1139
(s), 1062 (s), 1050 (s), 1002 (m), 935 (w), 899 (w), 863 (m), 767 (m), 757
(m), 738 (s), 697 (s), 676 (s), 653 (m), 626 (m), 592 (w), 562 (w), 522 (w),
472 (w), 431 (m), 417 (m) cm-1.[24]
Synthesis
of
2,2,3,3,3-pentafluoro-1-phenylpropan-1-ol
from
~
614.8 (100) [Sn(C2F5)4F]-; IR (ATR): ν=3412 (w, broad), 1588 (w), 1485
[PPh4][Sn(C2F5)5] and separation of n-Bu4Sn by (iii) silica gel column
chromatography: [PPh4][Sn(C2F5)5] (2.08 g, 1.97 mmol) and n-
butyllithium (3.33 g, 7.84 mmol, 1.6 M in n-hexane) were combined in
diethyl ether (50 mL) at -60 °C to obtain an orange solution. After stirring
for 20 min at this temperature benzaldehyde (0.90 g, 8.48 mmol) was
added. The solution was stirred overnight and was allowed to reach room
temperature. Aqueous HCl (100 mL; 0.5 M) was added to the brown
solution, which decolored within minutes. After phase separation and
extraction of the aqueous phase with diethyl ether (2x50 mL) the combined
diethyl ether solutions were washed with water and dried over MgSO4.
Filtration and solvent separation under reduced pressure furnished a
yellowish oil. The raw product was purified via silica gel column
chromatography using cyclohexane/ethyl acetate (4:1) (Rf = 0.7; Rf = 1 for
n-Bu4Sn). Removing the solvent in high vacuum (1x10-3 mbar) furnished
the product as a colorless liquid (0.65 g, 2.87 mmol, 34 %, purity 98 %).1H
(w), 1439 (w), 1287 (m), 1198 (s), 1161 (s), 1108 (s), 1079 (s), 1015 (m),
997 (m), 899 (m), 751 (s), 723 (s), 587 (w), 525 (s) cm-1.
Synthesis of [Li(12-crown-4)2][Sn(C2F5)5]: To a chilled (-78 °C) solution
of n-butyllithium (2.5 mL, 4.0 mmol, 1.6 M in n-hexane) and diethyl ether
(10 ml) pentafluoroethane (4.4 mmol) was condensed. After stirring for
20 min tris(pentafluoroethyl)tin bromide (1.11 g, 2.00 mmol) was added
and the reaction mixture was allowed to reach ambient temperature (3 h).
All volatile compounds were removed under reduced pressure. To the
obtained white solid residue CH2Cl2 (5 mL) was added. After filtration 12-
crown-4 (0.70 g, 3.97 mmol) was added. After removing all volatile
compounds under reduced pressure 1.37 g of a solid residue were
obtained. The crude product was recrystallized from CH2Cl2 to obtain
[Li(12-crown-4)2][Sn(C2F5)5] as
a colorless crystalline solid (0.86 g,
This article is protected by copyright. All rights reserved.

10.1002/chem.201704807
Chemistry - A European Journal
FULL PAPER
NMR ([D]chloroform, 298 K): δ=7.46 (m, 5H; Ar-H), 5.12 (dd,
3J(H,F)=17 Hz; 3J(H,F)=7 Hz, 1H; OCH), 2.71 ppm (s, 1H; OH); 13C{1H}
NMR ([D]chloroform, 298 K): δ=133.9, 129.7, 128.6, 127.9 (s; arom. C),
72.0 ppm (dd, 2J(C,F)=29 Hz, 2J(C,F)=22 Hz; COH); 13C{19F} NMR
([D]chloroform, 298 K): δ=119.1 (s; CF3), 113 ppm (m (broad); CF2); 19F
NMR ([D]chloroform, 298 K): δ=-81.5 (s, 3F; CF3), -120.0 (dd,
2J(F,F)=276 Hz, 3J(F,H)=6 Hz, 1F; CF2), -130.3 (dd, 2J(F,F)=275 Hz,
3J(F,H)=18 Hz, 1F; CF2); MS (EI, 70 eV, pos.) {m/z (%) [assignment]}:
225.9 (3) [HOCH(Ph)C2F5]∙+, 107.0 (100) [HOCPh]+, 79.0 (75); IR
Acknowledgements
This work was financially supported by Merck KGaA (Darmstadt,
Germany) and Solvay (Hannover, Germany) which is gratefully
acknowledged. We acknowledge the support by the Deutsche
Forschungsgemeinschaft (Core Facility GED@BI, Mi477/21-1)
and we thank Prof. Dr. Lothar Weber and Dr. Julia Bader for
helpful discussions.
~
(ATR): ν=3421 (w, broad), 3070 (w), 3039 (w), 1496 (w), 1457 (w), 1364
(w), 1339 (w), 1206 (s), 1178 (s), 1123 (s), 1063 (m), 1031 (s), 1008 (s),
923 (w), 852 (w), 821 (w), 757 (m), 697 (m), 641 (w), 622 (w), 585 (w), 535
(m) cm-1.[14]
Keywords: pentafluoroethyllithium • tin-lithium exchange •
perfluoroalkylation • gas-free • pentafluoroethyltin
Table 1. Structure refinement data of Sn(C2F5)4 and
[Li(12-crown-4)2][Sn(C2F5)5].
[1]
[2]
[3]
[4]
F. Sladojevich, E. McNeill, J. Borgel, S.-L. Zheng, T. Ritter, Angew.
Chem. Int. Ed. 2015, 54, 3712–3716.
[Li(12-crown-4)2]
[Sn(C2F5)5]
Sn(C2F5)4
I. Ruppert, K. Schlich, W. Volbach, Tetrahedron Lett. 1984, 25, 2195–
2198.
Crystallographic section
G. K. S. Prakash, R. Krishnamurti, G. A. Olah, J. Am. Chem. Soc. 1989,
111, 393–395.
empirical formula
a / pm
C8F20Sn
9.64809(11)
26.3233(3)
12.27281(17)
91.9279(11)
3115.16(7)
8
C26H32LiO8F25Sn
1615.53(5)
1206.96(2)
1955.50(6)
90
a) H. Morimoto, T. Tsubogo, N. D. Litvinas, J. F. Hartwig, Angew. Chem.
Int. Ed. 2011, 50, 3793–3798; b) A. Zanardi, M. A. Novikov, E. Martin, J.
Benet-Buchholz, V. V. Grushin, J. Am. Chem. Soc. 2011, 133, 20901–
20913.
b / pm
c / pm
β / °
[5]
a) B. R. Langlois, E. Laurent, N. Roidot, Tetrahedron Lett. 1991, 32,
7525–7528; b) Y. Fujiwara, J. A. Dixon, F. O'Hara, E. D. Funder, D. D.
Dixon, R. A. Rodriguez, R. D. Baxter, B. Herlé, N. Sach, M. R. Collins et
al., Nature 2012, 492, 95–99; c) F. O'Hara, D. G. Blackmond, P. S. Baran,
J. Am. Chem. Soc. 2013, 135, 12122–12134; d) A. G. O'Brien, A.
Maruyama, Y. Inokuma, M. Fujita, P. S. Baran, D. G. Blackmond, Angew.
Chem. Int. Ed. 2014, 53, 11868–11871.
V / 106 pm3
3812.96(18)
4
Z
ρcalc / mg∙mm-3
crystal system
space group
shape / color
crystal size / mm-3
2.536
1.869
monoclinic
P21/n
orthorhombic
Pna21
[6]
[7]
a) T. Umemoto, Y. Kuriu, H. Shuyama, O. Miyano, S.-I. Nakayama, J.
Fluorine Chem. 1986, 31, 37–56; b) I. Kieltsch, P. Eisenberger, A. Togni,
Angew. Chem. Int. Ed. 2007, 46, 754–757.
colorless in a capillary
0.59 × 0.15 × 0.13
Data collection
Agilent Supernova
1.857
colorless fragment
0.24 × 0.09 × 0.09
a) G. K. S. Prakash, A. K. Yudin, Chem. Rev. 1997, 97, 757–786; b) O.
A. Tomashenko, V. V. Grushin, Chem. Rev. 2011, 111, 4475–4521; c) A.
Studer, Angew. Chem. Int. Ed. 2012, 51, 8950–8958; d) T. Umemoto,
Chem. Rev. 1996, 96, 1757–1778.
diffractometer
Agilent Supernova
0.837
1
‑
μ / mm
T / K
[8]
[9]
G. K. S. Prakash, F. Wang, Z. Zhang, R. Haiges, M. Rahm, K. O. Christe,
T. Mathew, G. A. Olah, Angew. Chem. Int. Ed. 2014, 53, 11575–11578.
a) A. Johansson, A. Poliakov, E. Åkerblom, K. Wiklund, G. Lindeberg, S.
Winiwarter, U. Danielson, B. Samuelsson, A. Hallberg, Bioorg. Med.
Chem. 2003, 11, 2551–2568; b) M. Andrzejewska, L. Yépez-Mulia, R.
Cedillo-Rivera, A. Tapia, L. Vilpo, J. Vilpo, Z. Kazimierczuk, Eur. J. Med.
Chem. 2002, 37, 973–978.
100(1)
100(1)
F(000)
2224
2120
2θ range for data
collection / °
5.7 to 63.1
6.1 to 60.0
-14 ≤ h ≤ 14
-38 ≤ k ≤ 38
-17 ≤ l ≤ 17
-22 ≤ h ≤ 19
-16 ≤ k ≤ 16
-25 ≤ l ≤ 27
index ranges
[10] a) P. G. Gassman, N. J. O'Reilly, J. Org. Chem. 1987, 52, 2481–2490;
b) A. Lishchynskyi, V. V. Grushin, J. Am. Chem. Soc. 2013, 135, 12584–
12587; c) L. Li, C. Ni, Q. Xie, M. Hu, F. Wang, J. Hu, Angew. Chem. Int.
Ed. 2017, 56, 9971–9975; d) V. A. Petrov, Tetrahedron Lett. 2001, 42,
3267–3269; e) T. Umemoto, Y. Kuriu, H. Shuyama, O. Miyano, S.-I.
Nakayama, J. Fluorine Chem. 1982, 20, 695–698.
reflections collected
182656
10120
38887
10728
independent
reflections
R(int)
0.0527
0.0259
[11] C. Pooput, W. R. Dolbier, JR, M. Medebielle, J. Org. Chem. 2006, 71,
3564–3568.
data/restraints/param
eters
10120/1/593
10728/107/312
[12] K. Aikawa, K. Mikami, Org. Lett. 2014, 16, 3456–3459.
[13] G. K. S. Prakash, Y. Wang, R. Mogi, J. Hu, T. Mathew, G. A. Olah, Org.
Lett. 2010, 12, 2932–2935.
goodness-of-fit on F2
R1 / wR2 [I>2σ(I)]
R1 / wR2 (all data)
Δρmax/min / e Å-3
1.202
1.057
0.0391 / 0.0679
0.0475 / 0.0703
2.14 / -2.12
1562131
0.0367 / 0.1034
0.0412 / 0.1088
1.96 / -0.55
1562132
[14] R. Krishnamurti, D. R. Bellew, G. K. S. Prakash, J. Org. Chem. 1991, 56,
984–989.
[15] a) A. A. Kolomeitsev, A. A. Kadyrov, J. Szczepkowska-Sztolcman, M.
Milewska, H. Koroniak, G. Bissky, J. A. Barten, G.-V. Röschenthaler,
Tetrahedron Lett. 2003, 44, 8273–8277; b) N. E. Shevchenko, V. G.
Nenajdenko, G.-V. Röschenthaler, J. Fluorine Chem. 2008, 129, 390–
396; c) M. Henrich, A. Marhold, A. Kolomeitsev, A. Kadyrov, G.-V.
CCDC number
Röschenthaler, J. Barten, DE 101 28 703
A 1, 2001; d) M. H.
This article is protected by copyright. All rights reserved.

10.1002/chem.201704807
Chemistry - A European Journal
FULL PAPER
Königsmann, PhD thesis, Universität Bremen, Bremen, 2005; e) B.
Waerder, S. Steinhauer, B. Neumann, H.-G. Stammler, A. Mix, Y. V.
Vishnevskiy, B. Hoge, N. W. Mitzel, Angew. Chem. Int. Ed. 2014, 53,
11640–11644.
[23] a) M. Saito, S. Imaizumi, T. Tajima, K. Ishimura, S. Nagase, J. Am. Chem.
Soc. 2007, 129, 10974–10975; b) I. Schrader, K. Zeckert, S. Zahn,
Angew. Chem. Int. Ed. 2014, 53, 13698–13700.
[24] L. S. Chen, C. Tamborski, J. Fluorine Chem. 1982, 20, 341–348.
[25] N. Allefeld, B. Kurscheid, B. Neumann, H.-G. Stammler, N. Ignat'ev, B.
Hoge, Chem. Eur. J. 2015, 21, 13666–13675.
[16] abcr GmbH, www.abcr.de, Catalog No.: AB473271.
[17] a) A. G. Davies, Organotin chemistry, Wiley-VCH, Weinheim, 2004; b) D.
Seyferth, M. A. Weiner, J. Am. Chem. Soc. 1961, 83, 3583–3586.
[18] S. Solyntjes, J. Bader, B. Neumann, H.-G. Stammler, N. Ignat'ev, B.
Hoge, Chem. Eur. J. 2017, 23, 1557–1567.
[26] O. V. Dolomanov, L. J. Bourhis, R. J. Gildea, J. A. K. Howard, H.
Puschmann, J. Appl. Cryst. 2009, 42, 339–341.
[27] a) G. M. Sheldrick, Acta Cryst. A 2008, 64, 112–122; b) G. M. Sheldrick,
Acta Cryst. C 2015, 71, 3–8.
[19] J. Klösener, M. Wiesemann, M. Niemann, B. Neumann, H.-G. Stammler,
B. Hoge, Chem. Eur. J. 2017, 23, 8295–8303.
[20] P. Pfeiffer, O. Halperin, Z. Anorg. Chem. 1914, 87, 335–352.
[21] V. Coeffard, E. Le Grognec, I. Beaudet, M. Evain, J.-P. Quintard, J. Org.
Chem. 2009, 74, 5822–5838.
[22] N. Schwarze, S. Steinhauer, B. Neumann, H.-G. Stammler, B. Hoge,
Angew. Chem. Int. Ed. 2016, 55, 16156–16160.
This article is protected by copyright. All rights reserved.

10.1002/chem.201704807
Chemistry - A European Journal
FULL PAPER
COMMUNICATION
Markus Wiesemann, Johannes
Klösener, Beate Neumann, Hans-Georg
Stammler and Berthold Hoge*
Page No. – Page No.
On
Pentakis(pentafluoroethyl)stannate,
[Sn(C2F5)5]-, and the gas-free
Generation of
Gas-free pentafluoroethylation: Perfluoroalkylation reactions are often charac-
terized by the tedious handling of gases which led to the development of numerous
easy-to-handle perfluoroalkylation reagents. In the course of this the hypervalent
[PPh4][Sn(C2F5)5] represents an easily accessible, storable and solid precursor for
the generation of the highly reactive LiC2F5. Its reactivity and the separation of tin-
containing by-products were proven in several pentafluoroethylation reactions.
Pentafluoroethyllithium, LiC2F5
This article is protected by copyright. All rights reserved.