Synthesis of Stable Salts Containing the Hydridophosphate Anion [P(C2F5)3F2H]–

Article abstract of DOI:10.1002/ejic.201701375

The reaction of the industrial product (C₂F₅)₃PF₂ with LiAlH₄ in THF solution selectively furnished the hydridophosphate anion [P(C₂F₅)₃F₂H]^–. The compound [PPh₄][P(C₂F₅)₃F₂H] is obtained as a colorless solid on a multigram scale by salt metathesis in aqueous THF. Combining [P(C₂F₅)₃F₂H]^– with various imidazolium and pyridinium cations affords ionic liquids with melting points well below room temperature. (C₂F₅)₃PF₂ also abstracts hydrides from amines, affording the hydridophosphate anion [P(C₂F₅)₃F₂H]^– and the corresponding imminium cations which add a second amine moiety by intra- or intermolecular adduct formation.

Full text of DOI:10.1002/ejic.201701375

DOI: 10.1002/ejic.201701375
Full Paper
Hydridophosphates | Very Important Paper |
Synthesis of Stable Salts Containing the Hydridophosphate
Anion [P(C2F5)3F2H]–
Julia Bader,[a] Nikolai Ignat'ev,[b] and Berthold Hoge*[a]
Abstract: The reaction of the industrial product (C2F5)3PF2 with with melting points well below room temperature. (C2F5)3PF2
LiAlH4 in THF solution selectively furnished the hydridophos-
phate anion [P(C2F5)3F2H]–. The compound [PPh4][P(C2F5)3F2H]
is obtained as a colorless solid on a multigram scale by salt
metathesis in aqueous THF. Combining [P(C2F5)3F2H]– with vari-
ous imidazolium and pyridinium cations affords ionic liquids
also abstracts hydrides from amines, affording the hydridophos-
phate anion [P(C2F5)3F2H]– and the corresponding imminium
cations which add a second amine moiety by intra- or inter-
molecular adduct formation.
Introduction
acetonitrile.[11] KHF2 was also used for the synthesis of
K[P(CF3)2F3H] starting from (CF3)2PF.[13] Accordingly, treatment
of PF3 with KHF2 resulted in the formation of K[PF5H].[14] The
direct reaction of PF3 with HF and metal fluorides afforded
HPF4, while the formation of the expected hydridophosphate
[PF5H]– could not be observed under these conditions.[15] The
compound H2PF3 is converted into the stable hydridophos-
phates M[PF4H2] (M = K, Cs) by treatment with KF and CsF.[16]
The formation of complex anions with hydrido substituents
can also be achieved by the hydride abstraction from amines
by strong Lewis acids. B(C6F5)3 is able to abstract a hydride from
NEt3 to give [B(C6F5)3H]–,[17] but due to its high price it is not
suitable for technical applications. Usually, hydrides are ab-
stracted from amines by their reaction with carbocations like
Weakly coordinating anions (WCAs) are of great academic as
well as industrial interest. Based on the pioneering work of
Strauss, Reed, and Krossing, WCAs have been established as
constituents of ionic liquids, for lithium ion batteries as well as
for the stabilization of reactive cations.[1] Thereby perfluor-
inated WCAs like [B(C6F5)4]–, [Al{OC(CF3)3}4]– and [P(C2F5)3F3]–
exhibit an enormous potential in synthesis and application.[2]
The familiar hexafluorophosphate anion, [PF6]–, is used as a
lithium salt in lithium ion batteries[2] or in combination with
organic cations like imidazolium derivatives in ionic liquids.[3–5]
One disadvantage of [PF6]–, however, is the sensitivity of the PF
bond towards hydrolysis.[6,7] To circumvent this obstacle, per-
fluoroalkyl substituents are incorporated which enhance the
hydrolytic stability of the phosphate anion. Fluoroperfluoro-
alkylphosphate derivatives have been known for about 40
years.[8] The trifluorotris(pentafluoroethyl)phosphate ion,
[P(C2F5)3F3]–, which is used in commercially available ionic liq-
uids, exhibits a significantly reduced charge density in compari-
son to [PF6]–. The reaction of the technical product (C2F5)3PF2
with an aqueous HF solution selectively affords the correspond-
ing phosphoric acid [H(OH2)n][P(C2F5)3F3] as a precursor of a
variety of ionic liquids of surprising hydrolytic, thermal, and
electrochemical stability.[9–11]
CPh3 .
+ [18,19] The resulting imminium ion is a strong electrophile
and reacts with excess amines under adduct formation.[20,21]
With tetramethylethylenediamine (TMEDA) and 1,8-bis(dimeth-
ylamino)naphthalene (DMAN), for example, adduct formation
results in a ring closing reaction to a heterocyclic cation.[17,22]
Knoll and Krumm found that the imminium ion [Me2N=CH2]+
forms adducts with bases with a pKa value above 6, whereas
stronger bases with a pKa value above 10 like NEt3 deprotonate
the imminium ion.[23]
Fluorohydridophosphates are known since 1964 when Cavell
and Nixon reported the formation of [Me2NH2][P(CF3)F4H] by
the aminolysis of CF3PF2 with Me2NH.[12] [P(CF3)F4H]– was also
synthesized selectively by the reaction of CF3PF2 with KHF2 in
Results and Discussion
The synthesis of the difluorohydridotris(pentafluoroethyl)phos-
phate anion, [P(C2F5)3F2H]–, from (C2F5)3PF2 was recently real-
ized by a hydride transfer reaction.[24] This process strongly de-
pends on the reaction conditions.
The reaction of neat (C2F5)3PF2 with NaBH4 at elevated tem-
peratures only affords (C2F5)3P and (C2F5)2PH.[25] If the reduction
is carried out with LiAlH4 in diethyl ether, a mixture of (C2F5)3P,
(C2F5)2PH and C2F5PH2 is obtained. The selective conversion of
(C2F5)3PF2 to Li[P(C2F5)3F2H] is achieved with LiAlH4 in THF as a
solvent (Scheme 1).
[a] Centrum für Molekulare Materialien, Fakultät für Chemie,
Anorganische Chemie, Universität Bielefeld,
Universitätsstraße 25, 33615 Bielefeld, Germany
b.hoge@uni-bielefeld.de
http://www.uni-bielefeld.de/chemie/acii/hoge
[b] Consultant, Merck KGaA,
Frankfurter Str. 250, 64293 Darmstadt, Germany
ORCID(s) from the author(s) for this article is/are available on the WWW
under https://doi.org/10.1002/ejic.201701375.
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pling to the P–F fluorine atoms FA as well as the 3J(HF) coupling
to the fluorine atoms of the trans located CF2 unit is detected.
A cation exchange of in situ generated Li[P(C2F5)3F2H], 1a,
with different imidazolium chlorides and a pyridinium salt leads
to ionic liquids with melting points below room temperature
(Scheme 2). These products are insoluble in water and thus
can easily be separated from the aqueous reaction mixture.
Their melting points are well below room temperature and
range from –2.6 °C {[BMIm][P(C2F5)3F2H], 1d} over –2.4 °C
{[EMIm][P(C2F5)3F2H], 1c} to +9.6 °C {[BMMIm][P(C2F5)3F2H], 1e}
(see Scheme 2). For comparison, the trifluoro derivative
[BMIM][P(C2F5)3F3] melts at 3 °C,[26] while [EMIm][P(C2F5)3F3] ex-
hibits a melting point of –1 °C[26] (–37 °C[10]) and decomposes
at 300 °C.
Scheme 1. Reduction products of (C2F5)3PF2.
Li[P(C2F5)3F2H], 1a, however, decomposed during the con-
centration of the reaction solution in vacuo. The preparation of
a stable salt was achieved by the treatment of the dissolved
Li[P(C2F5)3F2H] with [PPh4]Cl in aqueous THF to give
[PPh4][P(C2F5)3F2H], 1b, as a colorless solid in an 82 % yield. The
oxygen- and moisture stable salt melts at 114–116 °C. Aqueous
solutions of the compound can be kept for several days at room
temperature without any sign of decomposition; the pure solid
can be stored under N2 without decomposition.
The 19F NMR spectrum exhibits one resonance for the
fluorine atoms bound directly to the phosphorus atom at
δ(19F) = –114.7 ppm. In addition to the J(PF) coupling of J =
1
737 Hz, a 2J(FH) coupling of J = 58 Hz leads to a broad doublet
of doublets, as evidenced by a 19F{1H} NMR spectrum. The 31P
NMR spectrum (Figure 1) displays a first-order spectrum in
which the coupling of the phosphorus atom to the fluorine
atoms of the CF3 units is not resolved. The signal is split into a
1
triplets by the J(PF) coupling to the P–F fluorine atoms FA. A
2
further quintet of triplets splitting results from the J(PF) cou-
pling to the fluorine atoms of the chemically inequivalent
pentafluoroethyl groups. In addition, a doublet with a 1J(PH)
coupling constant of J = 678 Hz is observed. The same coupling
Scheme 2. Synthesis of ionic liquids 1c–f of the [P(C2F5)3F2H]– anion.
1
is detected in the resonance of the hydrogen atom in the H
Related hydridophosphate salts decompose at a much lower
NMR spectrum which is split into a doublet of triplets of triplets temperature {[EMIm][P(C2F5)3F2H], 1c: 176 °C; [BMIm][P(C2F5)3-
1
2
at 5.6 ppm. In addition to the J(PH) coupling, the J(HF) cou- F2H], 1d: 177 °C; [BMMIm][P(C2F5)3F2H], 1e: 179 °C}. For the ther-
Figure 1. Experimental (top) and calculated (bottom) 31P NMR spectrum of [P(C2F5)3F2H]– as [PPh4]+ salt.
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mal decomposition of the pyridinium derivative [HPy][P(C2F5)3- corresponding product, [Me2NCH2NMe3][P(C2F5)3F2H], 2b, is iso-
F2H], 1f, an even lower decomposition temperature of 166 °C is lated quantitatively as a colorless solid.
found.
This transformation was conducted in the absence of any
[BMIm][P(C2F5)3F2H], 1d, exhibits a density of 1.58 g/cm3 at solvent. Furthermore, the stoichiometry is non-relevant, as both
20 °C (Table 1). This value is close to that of the analogous excess (C2F5)3PF2 or excess NMe3 are volatile species that can
trifluoro salt [BMIm][P(C2F5)3F3][27] but significantly larger than easily be removed from the solid product. Evaporating a flask
that of the hexafluorophosphate salt [BMIm][PF6].[28] The dy- with 2 g of 2b overnight, however, results in a complete re-
namic viscosity of [BMIm][P(C2F5)3F2H], 1d, (96 mPa s at 20 °C) moval of the salt, which indicates that the reaction of (C2F5)3PF2
lies in the same range as [BMIm][P(C2F5)3F3][27] and is considera- with NMe3 is reversible even at room temperature.
bly lower than that of [BMIm][PF6] (261 mPa s).[28]
The treatment of 2b with diphenylphosphonic ester fur-
nishes the substituted phosphonic ester Me2NCH2P(O)(OPh)2
and [HNMe3][P(C2F5)3F2H], 2c (Scheme 4). The reaction of 2b
with PMe3 leads under liberation of NMe3 to the phosphonium
Table 1. Density and dynamic viscosity of phosphate salts.
ρ /g cm3
η /mPa s
M.p. /°C
salt [Me2NCH2PMe3][P(C2F5)3F2H], 3.
[BMIm][P(C2F5)3F2H] (1d)
[BMIm][P(C2F5)3F3]
[BMIm][PF6]
1.58
96
–2.6
1.63[27]
1.36[28]
93[27]
261[28]
+3[26]
10.4[29]
In contrast to B(C6F5)3, which abstracts a hydride from NEt3
to give [B(C6F5)3H]–,[17] PF5 forms a colorless solid adduct with
NMe3. Substitution of three fluorine atoms of PF5 by penta-
fluoroethyl groups increases the Lewis acidity of the resulting
phosphorane (C2F5)3PF2 drastically. In keeping with this, the re-
action of (C2F5)3PF2 with NMe3 results in a hydride abstraction
by the phosphorane with an initial formation of the imminium
hydridophosphate [Me2NCH2][P(C2F5)3F2H], 2a (Scheme 3). The
Lewis acidic imminium ion adds a second equivalent of trimeth-
ylamine to form the ammonium ion [Me2NCH2NMe3]+.[20] The
Scheme 4. Reactions of the aminomethylammonium cation [Me2NCH2NMe3]+
with (PhO)2PHO and PMe3.
The solvent-free reaction of Me2NC2H4NMe2 (tetramethyleth-
ylenediamine, TMEDA) with (C2F5)3PF2 was performed similarly.
A hydride is transferred to the phosphorane (C2F5)3PF2, afford-
ing the hydridophosphate anion [P(C2F5)3F2H]–. The resulting
imminium cation [H2C(Me)NC2H4NMe2]+ of 4a, reacted with the
second amine functionality by an intramolecular ring closing
reaction[22] to afford [C6H15N2][P(C2F5)3F2H], 4b, as a viscous
hydrophobic liquid (Scheme 5). A density of 1.62 g/cm3 and a
dynamic viscosity of 298 mPa s at 20 °C were determined.
The treatment of 4b with PMe3 leads to the formation of the
corresponding phosphonium salt
(Scheme 5).
5
by ring opening
Scheme 3. Reaction of (C2F5)3PF2 with NMe3.
Scheme 5. Mechanism of the reaction of (C2F5)3PF2 with TMEDA.
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stirred for 20 min. The solution was hydrolyzed with formation of a
colorless precipitate, before a CHCl3 solution (5 mL) of [PPh4]Cl
(1.89 g, 5.04 mmol) was added. The precipitate was filtered off and
washed with chloroform. The aqueous phase was removed and the
chloroform phase was dried in vacuo. A colorless solid remained
Conclusions
The generation of the fluoro(perfluoroalkyl)hydridophosphate
anion [P(C2F5)3F2H]– strongly depends on the reaction condi-
tions. A selective synthesis was achieved by the reaction of
(C2F5)3PF2 with LiAlH4 in THF solution. The derivative
[PPh4][P(C2F5)3F2H], 1b, was obtained as a colorless solid by salt
metathesis with [PPh4]Cl. The cation exchange with differently
substituted imidazolium and pyridinium salts resulted in hydro-
phobic room temperature ionic liquids 1c–f.
Another successful generation of the [P(C2F5)3F2H]– anion
makes use of the hydride abstraction from amines. The strong
Lewis acid (C2F5)3PF2 abstracts a hydride ion from NMe3 and
TMEDA, respectively, to afford the hydridophosphate anion,
[P(C2F5)3F2H]–, and the corresponding imminium cations. The
initially formed [Me2NCH2]+ adds a second equivalent of
NMe3 to give the cation [Me2NCH2NMe3]+. The corresponding
hydridophosphate salt [Me2NCH2NMe3][P(C2F5)3F2H], 2b, was
isolated quantitatively. The reaction between (C2F5)3PF2 and
NMe3 is reversible at room temperature. The imminium ion gen-
erated from TMEDA, [H2C(Me)NC2H4NMe2]+, is stabilized by the
second amine functionality by intramolecular cyclization. The
product, [C6H15N2][P(C2F5)3F2H], 4b, represents a hydrophobic
room temperature ionic liquid. Both imminium cations display
the typical behavior towards PMe3 to furnish the corresponding
phosphonium cations.
1
(3.18 g, 82 %). M.p.: 114–116 °C. H NMR (CDCl3): δ = 5.6 {d, t, quin,
1
2
3
m, J(PH) = 678, J(HF) = 64, J(HFtrans) = 13 Hz, 1 H, [P(C2F5)3F2H]},
7.6–7.9 ppm {m, 20 H, [P(C6H5)4]+}. H{19F} NMR (CDCl3): δ = 5.6 {d,
1
1J(PH) = 678, 2J(HC) = 37 Hz, 1 H, [P(C2F5)3F2H]}, 7.6–7.9 ppm {m,
20 H, [P(C6H5)4]+}. 13C{1H} NMR (CDCl3): δ = 117.5 [d, 1J(PC) = 90 Hz,
2
3
ipso-C], 130.7 [d, J(PC) = 13 Hz, ortho-C], 134.2 [d, J(PC) = 13 Hz,
meta-C], 135.7 ppm [d, 4J(PC) = 3 Hz, para-C]. 13C{19F} NMR (CDCl3):
δ = 117.6 [d, 1J(PC) = 211 Hz, trans-CF2], 117.7 [d, 1J(PC) = 102,
2J(CH) = 37 Hz, cis-CF2], 120.3 [d, 2J(PC) = 28 Hz, trans-CF3],
120.9 ppm [d, 2J(PC) = 21 Hz, cis-CF3]. 19F NMR (CDCl3): δ = –81.4
(m, 3 F, trans-CF3), –83.1 (m, 6 F, cis-CF3), –113.9 [d, d, m, 1J(PF) =
737, 2J(FH) = 58 Hz, 2 F, PF], –120.6 [d, m, 2J(PF) = 104 Hz, 2 F, trans-
CF2], –127.3 ppm [d, m, 2J(PF) = 93 Hz, 4 F, cis-CF2]. 31P NMR (CDCl3):
δ = –154.9 {d, t, quin, t, 1J(PH) = 678, 1J(PF) = 738, 2J(PFcis) = 93,
2J(PFtrans) = 104 Hz, [P(C2F5)3F2H]–}, 23.4 ppm (m, [PPh4]+). ESI-MS
(neg.): m/z {(%) [assignment]} = 427.2 (100) [M]–, 307.2 (19) [M –
C2F5H]–. EI-MS (20 eV): m/z {(%) [assignment]}
= 414 (13)
[{PPh}{P(C2F5)2F2}]·+, 337 (53) [PPh4]+, 262 (100) [PPh3]·+, 183 (23)
[P(C2F5)FH]·+. IR (ATR): ν = 2325 (vw), 2245 (vw), 1588 (vw), 1486
˜
(vw), 1439 (w), 1310 (w), 1271 (w), 1207 (m), 1172 (m), 1124 (m),
1108 (m), 1069 (m), 1038 (w), 997 (w), 954 (m), 768 (m), 751 (w),
737 (w), 722 (s), 688 (m), 633 (vw), 613 (w), 594 (w), 556 (m), 523
(vs), 452 (w), 440 (w), 428 (m) cm–1. C30H21F17P2 (766.4): calcd. C
47.01, H 2.76; found C 47.15, H 2.87.
Synthesis of Ionic Liquids
Experimental Section
General Procedure: (C2F5)3PF2 was added at 0 °C to 1.1 equiv. of a
LiAlH4/THF solution (1 M) and stirred for 30 min. The resulting clear
(C2F5)3PF2 was provided by the Merck KGaA, Darmstadt, Germany.
All other chemicals were obtained from commercial sources. Tetra-
methylethylenediamine was dried with CaH2. All other chemicals
were used without further purification. Standard high-vacuum tech-
niques were employed throughout all preparative procedures. Non-
volatile compounds were handled in a dry N2 atmosphere using
Schlenk techniques. NMR spectra were recorded with a Bruker
Avance II 300 and a Bruker Model Avance III 300 (1H: 300.13 MHz;
13C: 75.47 MHz; 19F: 282.40 MHz; 31P: 111.92 MHz) with positive
shifts being downfield from the external standards [85 % ortho-
phosphoric acid (31P), CCl3F (19F) and TMS (1H, 13C)]. Computer sim-
ulation of the 31P NMR spectrum of [P(C2F5)3F2H]– was carried out
with the program gNMR.[30] C, H, and N analyses were carried out
with a HEKAtech Euro EA 3000 apparatus. 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. The spectra were recorded with a Bruker Daltonik
esquireNT 5.2 esquireControl software by the accumulation and av-
eraging of several single spectra. Data analysis software 3.4 was
used for processing the spectra. EI mass spectra were recorded with
a Finnigan MAT 95 spectrometer (20 eV). Melting points were deter-
mined using a HWS Mainz 2000 apparatus. IR spectra were recorded
on an Alpha FTIR spectrometer equipped with an ATR unit (Bruker)
in a range of 4000 cm–1 to 400 cm–1. The moisture content of ionic
liquids was measured by a Karl-Fischer titration (831 KF-Coulometer,
Metrohm) and the content of chloride and fluoride ions by ion-
chromatography (830 Metrohm). Viscosity, density and thermal sta-
bility (DSC) of ionic liquids were measured using a Viscosimeter
SVM 3000 (Anton Paar) and a Netzsch DSC 204 instrument.
solution was hydrolyzed with formation of a colorless precipitate.
Thereafter, one equivalent of [cat]Cl [cat = 1-Ethyl-3-methylimid-
azolium (EMIm), 1-Butyl-3-methylimidazolium (BMIm), 1-Hexylpyr-
idinium (HPy), 1-Butyl-2,3-dimethylimidazolium (BMMIm)], dis-
solved in 2 mL of H2O, was added. After stirring for 20 min, the
precipitate was filtered off. The filtrate consists of a two-phase sys-
tem. After the removal of the aqueous phase, the ionic liquids were
extracted two times with water and dried in vacuo, yielding color-
less liquids (1c–f) in yields of 30–60 %.
1c: Yield 3.4 g (33 %). 1H NMR ([D6]acetone): δ = 1.6 [t, 3J(HH) =
7 Hz, 3 H, CH2CH3], 4.0 (s, 1 H, CH3), 4.4 [q, 3J(HH) = 7 Hz, 2 H, CH2],
5.7 {d, t, t, m, 1J(PH) = 675, 2J(FH) = 63, 3J(FH) = 13 Hz, 1 H,
[P(C2F5)3F2H]}, 7.7/7.8 [t, 3J(HH) = 2, NCHCHN], 9.0 ppm (s, 1 H,
NCHN). 13C{1H} NMR ([D6]acetone): δ = 14.5 (s, CH2CH3), 35.6 (s,
CH3), 44.9 (s, CH2), 122.2 (s, EtNCHCH), 123.9 (s, MeNCHCH),
136.2 ppm (s, NCHN). 13C{19F} NMR ([D6]acetone): δ = 119.9 (m, CF2),
122.9 ppm (m, CF3). 19F NMR ([D6]acetone): δ = –81.1 [m, d, 4J(FH) =
1 Hz, 3 F, trans-CF3], –82.3 [quin, d, 3J(PF) = 9, 4J(FH) = 2 Hz, 6 F, cis-
1
2
CF3], –114.1 [d, d, m, J(PF) = 736, J(FH) = 64 Hz, 2 F, PF2], –119.7
[d, m, 2J(PF) = 104 Hz, 2 F, trans-CF2], –126.3 ppm [d, m, 2J(PF) =
93 Hz, 4 F, cis-CF2]. 31P NMR ([D6]acetone): δ = –154.4 ppm {d, t,
quin, t, 1J(PH) = 678, 1J(PF) = 735, 2J(PF) = 93, 2J(PF) = 104 Hz,
[P(C2F5)3F2H]–}.
1
1d: Yield 10.2 g (64 %). H NMR ([D6]acetone): δ = 0.9 [t, 3J(HH) =
7 Hz, 3 H, CH2CH3], 1.4 [pseudo-sext, 3J(HH) = 8 Hz, 2 H, CH2CH3],
1.9 [pseudo-quin, 3J(HH) = 7 Hz, 2 H, CH2C2H5], 4.0 (s, 3 H, CH3), 4.4
[t, 3J(HH) = 8 Hz, 2 H, CH2C3H7], 5.7 {d, t, t, m, 1J(PH) = 675, 2J(FH) =
63, 3J(FH) = 13 Hz, 1 H, [P(C2F5)3F2H]}, 7.7 (m, 2 H, NCHCHN),
9.1 ppm (s, 1 H, NCHN). 13C{1H} NMR ([D6]acetone): δ = 12.7 (s,
CH2CH3), 19.0 (s, CH2CH3), 31.8 (s, CH2C2H5), 35.7 (s, CH3), 49.4 (s,
[PPh4][P(C2F5)3F2H] (1b): (C2F5)3PF2 (2.38 g, 5.59 mmol) was added
slowly to a LiAlH4/THF solution (1
M, 5.6 mL, 5.6 mmol) at 0 °C and
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CH2C3H7), 122.5 (s, MeNCHCH), 123.9 (s, BuNCHCH), 136.4 ppm (s,
NCHN). 13C{19F} NMR ([D6]acetone): δ = 118.9 (m, CF2), 122.5 ppm
(m, CF3). 19F NMR ([D6]acetone): δ = –80.8 (m, 3 F, trans-CF3), –81.9
(m, 6 F, cis-CF3), –115.0 [d, d, m, 1J(PF) = 724, 2J(FH) = 65 Hz, 2 F,
PF2], –119.1 [d, m, 2J(PF) = 107 Hz, 2 F, trans-CF2], –125.7 ppm [d,
m, 2J(PF) = 92 Hz, 4 F, cis-CF2]. 31P NMR ([D6]acetone): δ =
–154.2 ppm {d, t, quin, t, 1J(PH) = 676, 1J(PF) = 737, 2J(PF) = 94,
2J(PF) = 104 Hz, [P(C2F5)3F2H]–}.
Reaction of 2b with (PhO)2PHO: Excess (PhO)2PHO was added to
a solution of [Me2NCH2NMe3][P(C2F5)3F2H] in CH2Cl2 to afford 2c
and Me2NCH2P(O)(OPh)2. The solution was analyzed by multi-
nuclear NMR spectroscopy. 13C{1H} NMR (CH2Cl2): δ = 44.7 {s,
3
1
[HN(CH3)3]+}, 45.1 [d, J(PC) = 5 Hz, (CH3)2N], 51.4 ppm [d, J(PC) =
157 Hz, Me2NCH2]. 19F NMR (CH2Cl2): δ = –80.8 (m, 3 F, trans-CF3),
1
2
–81.9 (m, 6 F, cis-CF3), –114.4 [d, d, m, J(PF) = 731, J(FH) = 63 Hz,
2
2 F, PF2], –119.3 [d, m, J(PF) = 103 Hz, 2 F, trans-CF2], –125.9 ppm
[d, m, 2J(PF) = 94 Hz, 4 F, cis-CF2]. 31P NMR (CH2Cl2): δ =
1e: Yield 9.1 g (55 %). 1H NMR ([D6]acetone): δ = 1.0 [t, 3J(HH) =
7 Hz, 3 H, CH2CH3], 1.4 [pseudo-sext, 3J(HH) = 7 Hz, 2 H, CH2CH3],
1.9 [pseudo-quin, 3J(HH) = 7 Hz, 2 H, CH2C2H5], 2.8 (s, 3 H, NCCH3N),
2
7.3 [t, J(PH) = 13 Hz, Me2NCH2P(O)(OPh)2], –153.8 ppm {d, t, quin,
t, 1J(PH) = 678, 1J(PF) = 731, 2J(PF) = 93, 2J(PF) = 104 Hz,
[P(C2F5)3F2H]–}.
3
3.9 (s, 1 H, CH3), 4.3 [t, J(HH) = 7 Hz, 2 H, CH2C3H7], 5.7 {d, t, t, m,
1J(PH) = 675, 2J(FH) = 63, 3J(FH) = 13 Hz, 1 H, [P(C2F5)3F2H]}, 7.6 ppm
(m, 2 H, NCHCHN). 13C{1H} NMR ([D6]acetone): δ = 8.9 (s, NCCH3N),
12.7 (s, CH2CH3), 19.1 (s, CH2CH3), 31.2 (s, CH2C2H5), 34.6 (s, CH3),
48.0 (s, CH2C3H7), 120.8 (s, NCHCHN), 122.2 (s, NCHCHN), 144.4 ppm
(s, NCMeN). 19F NMR ([D6]acetone): δ = –79.9 (m, 3 F, trans-CF3),
[Me2NCH2PMe3][P(C2F5)3F2H] (3): PMe3 (9.5 mmol) was con-
densed onto a solution of [Me2NCH2NMe3][P(C2F5)3F2H], 2b, (4.58 g,
8.42 mmol) in CH2Cl2 and the mixture was stirred for 30 min. Vola-
tile compounds were removed in vacuo. Colorless solid 3 remained
1
2
(4.72 g, 100 %). M.p.: 51.3 °C. H NMR (CD2Cl2): δ = 1.8 {d, J(PH) =
14 Hz, 9 H, [Me2NCH2P(CH3)3]+}, 2.4 {s, 6 H, [(CH3)2NCH2PMe3]+}, 3.3
[d, 2J(PH) = 5 Hz, 2 H, (Me2NCH2PMe3)+], 5.7 ppm {d, t, quin, m,
1J(PH) = 678, 2J(FH) = 64, 3J(FH) = 14 Hz, 1 H, [P(C2F5)3F2H]–}. 13C{1H}
1
2
–81.1 (m, 6 F, cis-CF3), –112.9 [d, d, m, J(PF) = 737, J(FH) = 65 Hz,
2
2 F, PF2], –118.6 [d, m, J(PF) = 105 Hz, 2 F, trans-CF2], –125.1 ppm
[d, m, 2J(PF) = 95 Hz, 4 F, cis-CF2]. 31P NMR ([D6]acetone): δ =
–153.7 ppm {d, t, quin, t, 1J(PH) = 674, 1J(PF) = 737, 2J(PF) = 92,
2J(PF) = 104 Hz, [P(C2F5)3F2H]–}.
1
NMR (CD2Cl2): δ = 6.5 {d, J(PC) = 54 Hz, [Me2NCH2P(CH3)3]+}, 47.6
3
1
{d, J(PC) = 7 Hz, [(CH3)2NCH2PMe3]+}, 52.9 ppm [d, J(PC) = 74 Hz,
(Me2NCH2PMe3)+]. 19F NMR (CD2Cl2): δ = –80.8 (m, 3 F, trans-CF3),
–82.0 (m, 6 F, cis-CF3), –113.9 [d, d, m, J(PF) = 730, J(FH) = 63 Hz,
1f: Yield 10.0 g (59 %). 1H NMR ([D6]acetone): δ = 0.9 (m, 3 H, CH3),
1
2
3
1.3–1.9 (m, 8 H, CH2), 4.5 [t, J(HH) = 7 Hz, 2 H, NCH2], 5.6 {d, t, t,
2
1
2
3
2 F, PF2], –119.2 [d, m, J(PF) = 105 Hz, 2 F, trans-CF2], –125.7 ppm
m, J(PH) = 673, J(FH) = 63, J(FH) = 13 Hz, 1 H, [P(C2F5)3F2H]}, 8.0
[d, m, J(PF) = 93 Hz, 4 F, cis-CF2]. 31P NMR (CD2Cl2): δ = –154.1 {d,
2
3
(m, 2 H, NCHCH), 8.5 [t, J(HH) = 8 Hz, 1 H, NC2H2CH], 8.7 ppm [d,
t, quin, t, 1J(PH) = 678, 1J(PF) = 728, 2J(PF) = 93, 2J(PF) = 105 Hz,
[P(C2F5)3F2H]–}, 24.3 ppm [dec, t, 2J(PH) = 13, 2J(PH) = 4 Hz,
(Me2NCH2PMe3)+]. 31P{1H} NMR (CD2Cl2): δ = –154.1 {t, quin, t,
3J(HH) = 6 Hz, 2 H, NCH]. 13C{1H} NMR ([D6]acetone): δ = 13.1 (s,
CH3), 22.0 (s, CH2CH3), 25.2 (s, CH2C2H5), 30.7 (s, NC2H4CH2), 30.8
(s, NCH2CH2), 61.9 (s, NCH2), 128.4 (s, NC2H2CH), 144.4 (s, NCHCH),
145.7 ppm (s, NCH). 13C{19F} NMR ([D6]acetone): δ = 118.2 (m, CF2),
120.9 ppm (m, CF3). 19F NMR ([D6]acetone): δ = –79.9 (m, 3 F, trans-
CF3), –81.1 (m, 6 F, cis-CF3), –112.9 [d, d, m, 1J(PF) = 737, 2J(FH) =
61 Hz, 2 F, PF2], –118.6 [d, m, 2J(PF) = 105 Hz, 2 F, trans-CF2],
–125.2 ppm [d, m, 2J(PF) = 92 Hz, 4 F, cis-CF2]. 31P NMR ([D6]-
1J(PF) = 728, J(PF) = 93, J(PF) = 105 Hz, [P(C2F5)3F2H]–}, 24.3 ppm
2
2
1
1
[s, J(PC) = 74, J(PC) = 54 Hz, (Me2NCH2PMe3)+]. IR (ATR): ν = 3375
˜
(vw, br), 3010 (vw), 2845 (vw), 2797 (vw), 2231 (vw), 1470 (vw), 1423
(vw), 1304 (w), 1274 (w), 1203 (s), 1179 (vs), 1119 (s), 1087 (w), 1063
(m), 1041 (w), 958 (vs), 913 (vw), 880 (vw), 827 (vw), 751 (s), 691
(vw), 664 (vw), 623 (w), 614 (m), 596 (m), 557 (s), 522 (s), 428 (w)
1
acetone): δ = –152.7 ppm {d, t, quin, t, 1J(PH) = 676, J(PF) = 737,
cm–1
.
2
2J(PF) = 94, J(PF) = 104 Hz, [P(C2F5)3F2H]–} (Table 2).
[Me2NCH2NMe3][P(C2F5)3F2H] (2b): NMe3 (7.3 mmol) was con-
[C6H15N2][P(C2F5)3F2H] (4b): (C2F5)3PF2 (14.59 g, 34.25 mmol) was
densed onto (C2F5)3PF2 (5.14 g, 12.1 mmol) and the mixture was
combined with tetramethylethylenediamine, TMEDA, (3.59 g,
stirred for 24 h at room temperature. Volatile compounds were re- 30.9 mmol) and the mixture was stirred for 3 days at room tempera-
moved in vacuo. A colorless solid remained (2.15 g, 100 %). 1H NMR
(CD3CN): δ = 2.6 [s, 6 H, (CH3)2N-], 2.8 [s, 9 H, -N(CH3)3], 4.0 (s, 2 H,
-NCH2N-), 5.7 ppm {d, t, quin, 1J(PH) = 675, 2J(FH) = 63, 3J(FH) =
ture. Volatile compounds were removed in vacuo, whereby 4b re-
mained as a colorless liquid (15.89 g, 95 %). H NMR (CD3CN): δ =
1
2.5 [s, 3 H, -N(CH3)], 2.8 (m, 2 H, MeNCH2), 3.2 [s, 6 H, N(CH3)2], 3.6
14 Hz, 1 H, [P(C2F5)3F2H]–}. 13C{1H} NMR (CD3CN): δ = 45.3 [s, (m, 2 H, Me2NCH2), 3.9 (s, 2 H, NCH2N), 5.6 ppm {d, t, quin, m,
(CH3)2N-], 48.4 [s, -N(CH3)3], 90.5 ppm (s, -NCH2N-). 19F NMR (CD3CN):
δ = –80.6 (m, 3 F, trans-CF3), –81.8 (m, 6 F, cis-CF3), –113.6 [d, d, m,
1J(PH) = 675, 2J(FH) = 63, 3J(FH) = 14 Hz, 1 H, [P(C2F5)3F2H]–}. 13C{1H}
NMR (CD3CN): δ = 37.3 [t, 1J(C14N) = 1.6 Hz, (CH3)N], 51.8 (s,
2
2
1J(PF) = 733, J(FH) = 62 Hz, 2 F, PF2], –119.1 [d, m, J(PF) = 104 Hz,
MeNCH2), 52.8 [t, 1J(C14N) = 4.4 Hz, N(CH3)2], 64.4 [t, 1J(C14N) =
2 F, trans-CF2], –125.7 ppm [d, m, 2J(PF) = 94 Hz, 4 F, cis-CF2]. 31P 3.9 Hz, Me2NCH2], 86.0 ppm [t, J(C14N) = 3.7 Hz, NCH2N]. 19F NMR
1
1
1
NMR (CD3CN): δ = –153.7 ppm {d, t, quin, t, J(PH) = 674, J(PF) =
(CD3CN): δ = –81.3 (m, 3 F, trans-CF3), –82.5 (m, 6 F, cis-CF3), –114.3
733, J(PF) = 94, J(PF) = 104 Hz, [P(C2F5)3F2H]–}.
[d, d, m, 1J(PF) = 734, 2J(FH) = 63 Hz, 2 F, PF2], –119.8 [d, m, 2J(PF) =
2
2
Table 2. Selected analytical data for salts of the composition [cat][P(C2F5)3F2H], 1c–f.
1c: [EMIm][a]
1d: [BMIm][b]
1e: [BMMIm][c]
1f: [HPy][d]
Yield /%
33
64
55
59
Glass transition /°C
Cold crystallization /°C
Melting point /°C
Decomposition point /°C
Content of H2O /ppm
Content of Cl– /ppm
Content of F– /ppm
–
–
–86
–38
–2.6
177
40.4
< 5
47.9
–78
–24
9.6
179
122.1
5.9
–76
–
–
166
26.8
142.54
7175
–2.4
176
43.1
< 5
111.9
197.5
[a] 1-Ethyl-3-methylimidazolium. [b] 1-Butyl-3-methylimidazolium. [c] 1-Butyl-2,3-dimethylimidazolium. [d] 1-Hexylpyridinium.
Eur. J. Inorg. Chem. 2018, 861–866 www.eurjic.org © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Full Paper
104 Hz, 2 F, trans-CF2], –126.5 ppm [d, m, 2J(PF) = 94 Hz, 4 F, cis-
[5] P. Wasserscheid, T. Welton, Ionic Liquids in Synthesis, Wiley-VCH, 2002, p.
1.
[6] A. V. Plakhotnyk, L. Ernst, R. Schmutzler, J. Fluorine Chem. 2005, 126, 27–
31.
[7] M. Ponikvar, B. Žemva, J. F. Liebman, J. Fluorine Chem. 2003, 123, 217–
220.
[8] S. S. Chan, C. J. Willis, Can. J. Chem. 1968, 46, 1237–1248.
[9] N. V. Ignatyev, M. Schmidt, A. Kuehner, V. Hilarius, U. Heider, A. Kucher-
yna, P. Sartori, H. Willner (Merck Patent GmbH), WO 03/002579, 2003.
[10] M. Schmidt, U. Heider, A. Kuehner, R. Oesten, M. Jungnitz, N. Ignat'ev, P.
Sartori, J. Power Sources 2001, 97–98, 557–560; N. V. Ignat'ev, H. Willner,
P. Sartori, J. Fluorine Chem. 2009, 130, 1183–1191.
1
CF2]. 31P NMR (CD3CN): δ = –154.4 ppm {d, t, quin, t, J(PH) = 676,
1J(PF) = 733, 2J(PF) = 93, 2J(PF) = 104 Hz, [P(C2F5)3F2H]–}. ESI-MS
(pos.): m/z {(%) [assignment]} = 115.0 (100) [C6H15N2]+. ESI-MS
(neg.): m/z {(%) [assignment]} = 426.6 (46) [P(C2F5)3F2H]–, 306.6 (100)
[P(C2F5)2F2]–, 118.8 (47) [C2F5]–. IR (ATR): ν = 2986 (vw), 2865 (vw),
˜
2823 (vw), 2795 (vw), 1472 (w), 1311 (w), 1271 (w), 1203 (s), 1175
(vs), 1122 (vs), 1070 (w), 1043 (m), 957 (s), 872 (w), 811 (w), 757 (s),
738 (m), 634 (w), 614 (m), 595 (m), 556 (s), 522 (s), 428 (m) cm–1
.
C12H16F17N2P (542.2): calcd. C 26.56, H 2.97, N 5.17; found C 26.71,
H 2.94, N 5.23.
[11] N. V. Ignat'ev, U. Welz-Biermann, A. Kucheryna, G. Bissky, H. Willner, J.
Fluorine Chem. 2005, 126, 1150–1159.
Reaction of 4b with PMe3: Excess PMe3 was added to a solution
of 4b in CH2Cl2. The resulting solution of 5 was analyzed by multi-
nuclear NMR spectroscopy. 1H NMR (CH2Cl2): δ = 1.8 [d, 2J(PH) =
14 Hz, 9 H, CH2P(CH3)3], 2.1 [s, 6 H, (CH3)2N], 3.1 [s, 3 H, (CH3)NCH2P],
[12] R. G. Cavell, J. F. Nixon, Proc. Chem. Soc. 1964, 201–248.
[13] J. F. Nixon, J. R. Swain, J. Chem. Soc. A 1970, 2075–2080.
[14] J. F. Nixon, J. R. Swain, Inorg. Nucl. Chem. Lett. 1969, 5, 295–299.
[15] K. O. Christe, D. A. Dixon, W. W. Wilson, J. Am. Chem. Soc. 1994, 116,
7123–7128.
2
1
3.4 [d, J(PH) = 4 Hz, 2 H, NCH2P], 5.6 ppm {d, t, quin, m, J(PH) =
678, 2J(FH) = 63, 3J(FH) = 14 Hz, 1 H, [P(C2F5)3F2H]–}. 13C{1H} NMR
(CH2Cl2): δ = 6.6 [d, 1J(PC) = 54 Hz, CH2P(CH3)3], 45.0 [s, (CH3)2N],
45.4 [d, 3J(PC) = 4 Hz, (CH3)NCH2P], 51.6 [d, 1J(PC) = 73, NCH2P],
56.6 [d, 3J(PC) = 9, CH2NCH2P], 57.6 ppm (s, Me2NCH2). 31P NMR
(CH2Cl2): δ = –154.0 {d, t, quin, t, 1J(PH) = 677, 1J(PF) = 730, 2J(PF) =
93, 2J(PF) = 104 Hz, [P(C2F5)3F2H]–}, 24.0 ppm {dec, t, 2J(PH) = 14,
2J(PH) = 4 Hz, [Me2NC2H4N(Me)CH2PMe3]+}. 31P{1H} NMR (CH2Cl2):
δ = –154.0 {t, quin, t, 1J(PF) = 730, 2J(PF) = 93, 2J(PF) = 104 Hz,
[16] K. O. Christe, C. J. Schack, E. C. Curtis, Inorg. Chem. 1976, 15, 843–848.
[17] A. Di Saverio, F. Focante, I. Camurati, L. Resconi, T. Beringhelli, G. D'Al-
fonso, D. Donghi, D. Maggioni, P. Mercandelli, A. Sironi, Inorg. Chem.
2005, 44, 5030–5041; S. N. Gamage, R. H. Morris, S. J. Rettig, D. C. Thack-
ray, I. S. Thorburn, B. R. James, J. Chem. Soc., Chem. Commun. 1987, 894–
895; R. P. Hughes, I. Kovacik, D. C. Lindner, J. M. Smith, S. Willemsen, D.
Zhang, I. A. Guzei, A. L. Rheingold, Organometallics 2001, 20, 3190–3197;
A. F. Pozharskii, M. A. Povalyakhina, A. V. Degtyarev, O. V. Ryabtsova, V. A.
Ozeryanskii, O. V. Dyablo, A. V. Tkachuk, O. N. Kazheva, A. N. Chekhlov,
O. A. Dyachenko, Org. Biomol. Chem. 2011, 9, 1887–1900.
[18] M. T. Reetz, W. Stephan, W. F. Maier, Synth. Commun. 1980, 10, 867–871.
[19] H. Volz, H.-H. Kiltz, Justus Liebigs Ann. Chem. 1971, 752, 86–101.
[20] A. R. Mahjoub, D. Leopold, K. Seppelt, Z. Anorg. Allg. Chem. 1992, 618,
83–88.
1
[P(C2F5)3F2H]–}, 24.0 {s, J(PC) = 54 Hz, [Me2NC2H4N(Me)CH2PMe3]+}
ppm.
Acknowledgments
This work was financially supported by Merck KGaA (Darmstadt,
Germany). Solvay (Hannover, Germany) is gratefully acknowl-
edged for donating chemicals. We thank Prof. Dr. Lothar Weber
for helpful discussions.
[21] R. Kiesel, E. P. Schram, Inorg. Chem. 1973, 12, 1090–1095.
[22] V. Kokozay, A. V. Sienkiewicz, Polyhedron 1995, 14, 1547–1551; D. J. Peter-
son, J. F. Ward, J. Organomet. Chem. 1974, 66, 209–217.
[23] F. Knoll, U. Krumm, Chem. Ber. 1971, 104, 31–39.
[24] B. Hoge, J. Bader, M. Schulte, N. Ignatiev (Merck Patent GmbH), EP 2 513
123 B1, 2011.
[25] U. Welz-Biermann, N. Ignatyev, M. Weiden, M. Schmidt, U. Heider, A. Mil-
ler, H. Willner, P. Sartori (Merck Patent GmbH), WO 03/087113 A1, 2003.
[26] H. Li, F. Endres, R. Atkin, Phys. Chem. Chem. Phys. 2013, 15, 14624–14633.
[27] J. Safarov, F. Lesch, K. Suleymanli, A. Aliyev, A. Shahverdiyev, E. Hassel, I.
Abdulagatov, J. Chem. Eng. Data 2017, 62, 3620–3631.
[28] W. Li, Z. Zhang, B. Han, S. Hu, Y. Xie, G. Yang, J. Phys. Chem. B 2007, 111,
6452–6456.
[29] G. J. Kabo, A. V. Blokhin, Y. U. Paulechka, A. G. Kabo, M. P. Shymanovich,
J. Chem. Eng. Data 2004, 49, 453–461.
[30] P. H. M. Budzelaar, g NMR Version 4.1, Cherwell Scientific Publishing Ltd.,
Oxford 1999.
Keywords: Hydridophosphates · Anions · Hydride
abstraction · Fluorine · Ionic liquids
[1] Review: C. Reed, Acc. Chem. Res. 1998, 31, 133–139; S. H. Strauss, Chem.
Rev. 1993, 93, 927–942; I. Krossing, I. Raabe, Angew. Chem. Int. Ed. 2004,
43, 2066–2090; Angew. Chem. 2004, 116, 2116–2142.
[2] G. Y. Gu, S. Bouvier, C. Wu, R. Laura, M. Rzeznik, K. M. Abraham, Electro-
chim. Acta 2000, 45, 3127–3139.
[3] J. Fuller, R. T. Carlin, H. C. De Long, D. Haworth, J. Chem. Soc., Chem.
Commun. 1994, 299–300.
[4] Y. Chauvin, L. Mussmann, H. Olivier, Angew. Chem. Int. Ed. Engl. 1995, 34,
2698–2700; Angew. Chem. 1995, 107, 2941.
Received: November 23, 2017
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