Investigations of the tautomeric equilibria between phosphane oxides and their corresponding phosphinous acids bearing electron-withdrawing perfluoroaryl groups

Article abstract of DOI:10.1002/ejic.201100984

The unusual form of a phosphinous acid can be stabilized by strongly electron-withdrawing substituents such as trifluoromethyl and pentafluoroethyl groups. The less electron-withdrawing pentafluorophenyl group favors the phosphane oxide tautomer (R_f)₂P(O)H in the solid state, whereas in solution a solvent-dependent equilibrium with the phosphinous acid tautomer (R_f)₂POH is observed. The increasing donating ability of the solvent leads to an increasing amount of the corresponding phosphinous acid tautomer. In accord with quantum chemical calculations, the electron-withdrawing effects of the p-tetrafluoropyridyl and 2,4-bis(trifluoromethyl)phenyl groups exceed the pentafluorophenyl group and should therefore be ideally suited to stabilize the corresponding phosphinous acid tautomer (R_f)₂POH. The syntheses of bis(tetrafluoropyridyl)- and bis[2,4-bis(trifluoromethyl)phenyl]phosphane oxide enabled the investigation of the solvent-dependent tautomerism by NMR spectroscopy. Introduction of the tetrafluoropyridyl group shifts the tautomeric equilibrium significantly towards the phosphinous acid. Surprisingly, the comparably electron-withdrawing but more bulky 2,4-bis(trifluoromethyl)phenyl group favors the oxide tautomer. The experimental results have been confirmed by DFT calculations. In summary, electron-withdrawing substituents stabilize the phosphinous acid tautomer, whereas it is destabilized by space-demanding groups by an increased C-P-C angle. The solvent-dependent tautomeric equilibria between secondary phosphane oxides and their corresponding phosphinous acids bearing electron-withdrawing fluoroaryl groups is reported. Copyright

Full text of DOI:10.1002/ejic.201100984

FULL PAPER
DOI: 10.1002/ejic.201100984
Investigations of the Tautomeric Equilibria between Phosphane Oxides and
Their Corresponding Phosphinous Acids Bearing Electron-Withdrawing
Perfluoroaryl Groups
Boris Kurscheid,[a] Waldemar Wiebe,[a] Beate Neumann,[a] Hans-Georg Stammler,[a] and
Berthold Hoge*[a]
Keywords: Phosphorus / Substitent effects / Tautomerism / Solvent effects
The unusual form of a phosphinous acid can be stabilized by
strongly electron-withdrawing substituents such as trifluoro-
methyl and pentafluoroethyl groups. The less electron-with-
drawing pentafluorophenyl group favors the phosphane ox-
ide tautomer (Rf)2P(O)H in the solid state, whereas in solution
a solvent-dependent equilibrium with the phosphinous acid
tautomer (Rf)2POH is observed. The increasing donating abil-
ity of the solvent leads to an increasing amount of the corre-
sponding phosphinous acid tautomer. In accord with quan-
tum chemical calculations, the electron-withdrawing effects
of the p-tetrafluoropyridyl and 2,4-bis(trifluoromethyl)phenyl
groups exceed the pentafluorophenyl group and should
therefore be ideally suited to stabilize the corresponding
phosphinous acid tautomer (Rf)2POH. The syntheses of bis-
(tetrafluoropyridyl)- and bis[2,4-bis(trifluoromethyl)phenyl]-
phosphane oxide enabled the investigation of the solvent-
dependent tautomerism by NMR spectroscopy. Introduction
of the tetrafluoropyridyl group shifts the tautomeric equilib-
rium significantly towards the phosphinous acid. Surpris-
ingly, the comparably electron-withdrawing but more bulky
2,4-bis(trifluoromethyl)phenyl group favors the oxide tauto-
mer. The experimental results have been confirmed by DFT
calculations. In summary, electron-withdrawing substituents
stabilize the phosphinous acid tautomer, whereas it is desta-
bilized by space-demanding groups by an increased C–P–C
angle.
drawing aryls than the pentafluorophenyl group. The elec-
tron-withdrawing effect of a variety of differently substi-
tuted phenyl groups can be classified on the basis of the C–
O or C–N bond lengths in the corresponding phenolate or
amide ions (Ar–O– and Ar–NH–), respectively, which are
accessible by DFT calculations.[6] According to these, an
increase in the electron-withdrawing effect of the aromatic
group leads to a shortened C–O and C–N distance in the
corresponding ions.
Introduction
Trivalent phosphinous acids, R2POH, are related to
pentavalent phosphane oxides, R2P(O)H, by tautomerism.
For electron-donating alkyl and aryl groups R the tauto-
meric equilibrium is completely shifted towards the phos-
phane oxide, see Equation (1).
The difference between the C–E bond lengths in the
XC6H4–E derivatives and the parent compound C6H5–E is
denoted by Δ(E)m,p. For E = O– and NH–, the values of
Δ(E)m,p exhibit the same tendency as the corresponding
Hammett constants. Therefore the values Δ(E)m,p are useful
for classifying the electron-withdrawing effect of various
kinds of substituents on phenyl or aryl groups. We calcu-
lated the electron-withdrawing effect to increase in the series
below.[6]
(1)
To stabilize the unfavored phosphinous acid structure the
introduction of strongly electron-withdrawing substituents,
such as trifluoromethyl and pentafluoroethyl groups, is nec-
essary.[1,2] The employment of the weaker electron-de-
manding pentafluorophenyl group favors the phosphane
oxide tautomer [(F5C6)2P(O)H, 1] in the solid state whereas
in solution a solvent-dependent equilibrium is observed.[3,4]
With increasing solvent donicity (DN),[5] an increasing
amount of the phosphinous acid tautomer is observed.
The aim of this work was to stabilize the phosphinous
acid tautomer by introducing more strongly electron-with-
[a] Fakultät für Chemie, Anorganische Chemie, Universität
Bielefeld,
Based on this theoretical model an increased stabilization
of the phosphinous acid was expected by introducing the
Universitätsstr. 25, 33615 Bielefeld, Germany
E-mail: b.hoge@uni-bielefeld.de
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B. Kurscheid, W. Wiebe, B. Neumann, H.-G. Stammler, B. Hoge
FULL PAPER
more strongly electron-withdrawing p-tetrafluoropyridyl
and 2,4-bis(trifluoromethyl)phenyl groups. Herein we de-
scribe the synthesis of the corresponding phosphane oxides
(Rf)2P(O)H and our study of the electronic as well as the
steric effects of the chosen aryl groups Rf on the formation
of the corresponding phosphinous acid tautomer (Rf)2P–
OH.
Results and Discussion
Bis(tetrafluoropyridyl)phosphane oxide has previously
been generated by the hydrolysis of P(C5NF4)3 under basic
conditions.[3] In this paper we describe an efficient synthesis
of the phosphane oxide (C5NF4)2P(O)H starting from p-
tetrafluoropyridine. Metalating p-C5NF4H with n-butyllith-
ium and the subsequent addition of dichloro(diethylamino)-
phosphane, Cl2PNEt2, selectively resulted in the forma-
tion of bis(tetrafluoropyridyl)(diethylamino)phosphane,
(C5NF4)2PNEt2 (Scheme 1). Evaporating the solvent and
distillation of the residue afforded the product as a yellow
liquid in 88% yield. Cleavage of the P–N bond and hydroly-
sis to give bis(tetrafluoropyridyl)phosphane oxide (2) was
achieved in a two-phase system of conc. hydrochloric acid
Scheme 1. Reaction of dichloro(diethylamino)phosphane with lithi-
ated tetrafluoropyridine and subsequent hydrolysis of the interme-
diate to give bis(tetrafluoropyridyl)phosphane oxide (2).
and toluene (Scheme 1). The product was obtained in a no phosphinous acid was detected in CH3CN solution,
yield of 70% as a colorless solid that melts at 94 °C. The 78% of the tetrafluoropyridyl derivative exists as the phos-
vibrational spectrum of the solid supports the phosphane phinous acid tautomer.[7]
oxide structure: the band at ν = 2430 cm–1 (KBr) for the P–
In addition to the tetrafluoropyridyl group, the 2,4-bis-
H stretching vibration compares well with the correspond- (trifluoromethyl)phenyl group is also more electron-de-
ing band of (C F ) P(O)H at ν = 2472 cm–1.[3,7]
manding than the pentafluorophenyl group and therefore
˜
˜
6
5 2
A solvent-dependent equilibrium between the bis(tetra- should be suitable for shifting the tautomeric equilibrium
fluoropyridyl)phosphane oxide (2) and the corresponding towards the phosphinous acid. Bis[2,4-bis(trifluoromethyl)-
acid tautomer 2a was observed.[3,7] As expected, the intro- phenyl]phosphane oxide (3) is accessible on a multigram
duction of the stronger electron-withdrawing C5NF4 sub- scale by a known protocol starting from 1,3-bis(trifluoro-
stituent led to a significant shift of the equilibrium towards methyl)benzene.[8] The reaction of 1,3-bis(trifluoromethyl)-
the phosphinous acid. Although with the C6F5 derivative benzene with n-butyllithium in the absence of auxiliary li-
Scheme 2. Reaction of dichloro(diethylamino)phosphane with lithiated 1,3-bis(trifluoromethyl)benzene, P–N bond cleavage to the inter-
mediate chlorophosphane, and its eventual hydrolysis to bis[2,4-bis(trifluoromethyl)phenyl]phosphane oxide (3).
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Tautomerism of Phosphinous Acids
gands, such as TMEDA, resulted in the formation of a mix-
ture of 2,4- and 2,6-bis(trifluoromethyl)phenyllithium
(Scheme 2).[8–12] For a selective synthesis of bis[2,4-bis(tri-
fluoromethyl)phenyl]phosphane derivatives we utilized the
steric demand of the diethylamino group to discriminate
between the two aryllithiums.[8] In keeping with this, the
reaction of dichloro(diethylamino)phosphane with an ex-
cess of 2,4- and 2,6-bis(trifluoromethyl)phenyllithium led to
the selective formation of the aminophosphane. Cleavage
of the P–N bond in a chloroform/conc. hydrochloric acid
mixture afforded the corresponding diarylchlorophosphane.
Surprisingly, no hydrolysis to the corresponding secondary
phosphane oxide 3 was observed under these conditions,
contrary to the hydrolysis of the corresponding diphenyl-,
Figure 1. Molecular structure of bis[2,4-bis(trifluoromethyl)phen-
yl]phosphane oxide (3) (ellipsoids are drawn at 50% probability
level; all C-bonded hydrogen atoms have been omitted for clarity).
Selected bond lengths [pm] and angles [°]: P1–O1 148.5(1), P1–C1
181.7(2), P1–H1 1.29(2), P1–C9 182.3(2), C1–P–C9 106.0(1).
In the solid state, compound 3 exists as the oxide tauto-
bis(pentafluorophenyl)-, and bis(p-tetrafluoropyridyl)chlo- mer, whereas in solution a solvent-dependent equilibrium
rophosphanes, R2PCl, which hydrolyze under comparable was observed analogous to the pentafluorophenyl- and p-
conditions to the corresponding secondary phosphane ox- tetrafluoropyridyl-substituted derivatives.
ides, R2P(O)H.
Figure 2 shows the 31P NMR spectra of a mixture of
However, the reaction of a THF solution of [2,4- [2,4-(CF3)2C6H3]2P(O)H (3) and the phosphinous acid [2,4-
(CF3)2C6H3]2PCl with water readily afforded the corre- (CF3)2C6H3]2P–OH (3a) in [D6]DMSO. The resonance of
sponding phosphane oxide [2,4-(CF3)2C6H3]2P(O)H (3) in the phosphinous acid 3a is observed at δ = 77.3 ppm as a
3
4
87% yield after recrystallization from CH2Cl2 solution. The doublet of septets with couplings J(P,H) and J(P,F) of 9
structure of 3 was determined by X-ray diffraction analysis and 57 Hz, respectively. The resonance of the phosphane
(Figure 1). The colorless [2,4-(CF3)2C6H3]2P(O)H (3) crys- oxide isomer 3 is upfield-shifted by about 70 ppm and dis-
tallizes in the monoclinic space group C2/c (No. 15). The plays the expected 1J(P,H) coupling of 561 Hz (Figure 2,
4
P–O distance of 148.5(1) pm is typical for a P=O double bottom). The J(P,F) coupling of the trivalent phosphorus
bond and proves the existence of the phosphane oxide iso- derivative with bis(trifluoromethyl)phenyl substituents de-
mer in the solid state. H1 was refined isotropically.
creases significantly on going to the pentavalent phosphane
Figure 2. 31P{1H} NMR (top) and 31P NMR (bottom) spectra of the tautomeric phosphane oxide 3 and the corresponding phosphinous
acid 3a in [D6]DMSO at room temp.
Eur. J. Inorg. Chem. 2011, 5523–5529
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B. Kurscheid, W. Wiebe, B. Neumann, H.-G. Stammler, B. Hoge
FULL PAPER
Figure 3. 2D 31P EXSY NMR spectrum of bis[2,4-bis(trifluoromethyl)phenyl]phosphane oxide (3) in [D6]DMSO at room temp.
4
oxide derivative with a J(P,F) coupling of only 8 Hz (Fig- in all the investigated solvents is significantly lower than
ure 2). To prove the dynamic nature of the exchange process those featuring C6F5 or C5NF4 groups (Table 1).
between the phosphinous acid and phosphane oxide tauto-
The relative proportion of the phosphinous acid tauto-
mer a two-dimensional 31P EXSY NMR spectrum was re- mer decreases along the series tetrafluoropyridyl, penta-
corded. The observation of cross peaks between the reso- fluorophenyl, and 2,4-bis(trifluoromethyl)phenyl. This ob-
nances of the phosphinous acid and the oxide isomer proves servation contrasts with the estimated electron-withdrawing
the tautomeric nature in DMSO solution (Figure 3).
effects of the chosen aryl groups. As the electronic effects
Interestingly, in the equilibrium between 3 and 3a in of C5NF4 and 2,4-(CF3)2C6H3 are comparable, the stabili-
DMSO solution, only 31% of the phosphinous acid isomer zation of the corresponding phosphinous acid tautomers
was detected. This value is unexpectedly low in comparison and consequently the relative proportions of 2a and 3a
with the pentafluorophenyl- and tetrafluoropyridyl-substi- should also be comparable. Quantum chemical calculations
tuted derivatives. Only in an extremely donating solvent, support these experimental findings. The C5NF4-substi-
such as HMPA (hexamethylphosphoramide), does the tuted phosphinous acid 2a is 10.5 kJ/mol lower in energy
amount of acid tautomer 3a exceed the amount of the cor- than the corresponding phosphane oxide 2, whereas the
responding phosphane oxide 3 (Table 1). The relative pro- pentafluorophenyl derivatives 1a and 1 have similar energies
portion of the acid tautomer with 2,4-(CF3)2C6H3 groups (cf. Table 1).[3] In contrast, with the 2,4-bis(trifluorometh-
Table 1. Dependence of the amounts of phosphinous acid tautomers 1a, 2a, and 3a on the chosen solvent.[a]
Solvent
(C5NF4)2P–OH (2a)
(C6F5)2P–OH (1a)[b]
[2,4-(CF3)2C6H3]2P–OH (3a)
DN[c]
EZP (acid) – Ezp (oxide)[d]
–10.5
–1.7
19.6
Chloroform
Toluene
Acetonitrile
THF
Diethyl ether
DMF
DMSO
Pyridine
NMP
21
46
78
0
0
0
55
60
67
76
(80)
90[e]
n.p.
0
0
0
10
10
20
31
36
41
95
–
–
14.1
20.0
19.2
24.0
29.8
33.1
27.3
38.8
99
100
100
n.p.
(100)
n.p.
n.p.
HMPA
[a] Percentage distribution from the integration of the 31P NMR resonances; n.p. = not performed [b] Values of (F6F5)2P–OH are
literature-known.[3] [c] DN = solvent donicity (see ref.[5]). [d] Calculations were performed at the B3LYP/6-311G(2d,p) level of theory.
[e] Recent work.
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Tautomerism of Phosphinous Acids
yl)phenyl groups, the phosphane oxide 3 is stabilized by
19.6 kJ/mol. Thus, the experimental findings as well as the
theoretical results underline that the stabilization of phos-
phinous acids is not only a function of the electronic nature
of the aryl substituents but is also equally governed by ste-
ric effects.
As predicted from the Lewis structures, DFT calcula-
tions confirmed that phosphinous acids exhibit smaller C–
P–C angles than the corresponding phosphane oxide iso-
mers (Scheme 3). This leads to the assumption that steri-
cally demanding groups cause a destabilization of the phos-
phinous acid form.
Figure 4. Dependence of the potential energies of H2P–OH and
H3PO on the H–P–H angle [relaxed potential energy scan at the
B3PW91/6-311G(3d,p) level of theory].
ploying the coupled-cluster series gave a comparable
value.[13] In solution, the energy gap is significantly
larger.[13] Recently, Peruzzini and co-workers succeeded in
generating the phosphane oxide H3PO in solution by elec-
trochemical methods.[14] The phosphinous acid tautomer
could be trapped by coordination to ruthenium complexes.
Conclusions
Based on DFT calculations, the p-tetrafluoropyridyl and
2,4-bis(trifluoromethyl)phenyl groups are more electron-de-
manding than the pentafluorophenyl ring, which should
stabilize the phosphinous acid isomer. The introduction of
the p-tetrafluoropyridyl group led, as expected, to a shift in
the equilibrium towards the phosphinous acid in compari-
son to the weaker electron-withdrawing pentafluorophenyl
group.
The experimental and theoretical investigations of the
tautomerism of bis[2,4-bis(trifluoromethyl)phenyl]phos-
phane oxide, however, indicate that steric effects also influ-
ence the tautomeric equilibrium. Thus, the increased spatial
demand of the 2,4-bis(trifluoromethyl)phenyl substituent
leads to a widened C–P–C angle and therefore to a destabi-
lization of the acid isomer (Rf)2P–OH.
Scheme 3. Experimental (in brackets) and calculated [B3LYP/6-
311G(2d,p)] C–P–C angles of the diarylphosphane oxides 1–3 and
the corresponding phosphinous acids 1a–3a.
To gain a closer insight into the relative energies of the
phosphinous acids and their phosphane oxide tautomers, a
relaxed potential energy scan was performed by varying the
H–P–H angle in the phosphinous acid, H2P–OH, and the
phosphane oxide, H3PO. As depicted in Figure 4, for H–P–
H angles below 95° the phosphinous acid isomer is energeti-
cally favored, whereas H–P–H angles larger than 95° stabi-
lize the phosphane oxide isomer. Further increasing the H–
P–H angle leads to an increase in the energy gap between
the phosphane oxide structure and the phosphinous acid
isomer.
Experimental Section
General: Dichloro(diethylamino)phosphane was prepared accord-
ing to the procedure of Burg and Slota by treating PCl3 with
2 equiv. of HNEt2 in hexane solution.[15] All other chemicals were
obtained from commercial sources and used without further purifi-
cation. Standard high-vacuum techniques were employed through-
out the work. Nonvolatile compounds were handled under dry N2
using Schlenk techniques.
With the optimized H–P–H angles, the phosphane oxide
H3PO is, at the B3LYP/6-311G(3d,p) level of theory, stabi-
lized by 4.3 kJ/mol with respect to the phosphinous acid
NMR spectra were recorded with a Bruker Model Avance III 300
spectrometer (31P NMR: 111.92 MHz; 19F NMR: 282.40 MHz; 13
C
NMR: 75.47 MHz; 1H NMR: 300.13 MHz) with positive shifts be-
tautomer H2P–OH. Complete basis set extrapolations em- ing downfield from the external standards [85% orthophosphoric
Eur. J. Inorg. Chem. 2011, 5523–5529
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B. Kurscheid, W. Wiebe, B. Neumann, H.-G. Stammler, B. Hoge
3-F, 5-F), –93.6 (m, 2-F, 6-F) ppm. 31P NMR (111.92 MHz,
FULL PAPER
acid (31P), CCl3F (19F), and TMS (1H)]. EI mass spectra were re-
corded with a Finnigan MAT 95 spectrometer (20 eV). Intensities
are referenced to the most intense peak within a spectrum. Isotope
patterns for comparison were calculated with the program Iso-
pro.[16]
3
CD3CN): δ = 69.9 [quint, J(P,F) = 28 Hz, (C5NF4)2P-OH] ppm.
MS (EI, 20 eV): m/z (%) = 348 (100) [(C5NF4)2POH]+, 332 (4)
[(C5NF4)2PH]+, 198 (23) [(C5NF4)POH]+, 181 (2) [(C5NF4)P]+, 151
(12) [C5NF4H]+, 132 (6) [C5NF3H]+. C10HF8N2OP (348.1): calcd.
C 34.50, H 0.29, N 8.05; found C 34.39, H 0.24, N 7.86.
Melting and visible decomposition points were determined by
using a HWS Mainz 2000 apparatus. C, H, and N analyses were
carried out with a HEKAtech Euro EA 3000 apparatus.
Solvent-Dependent Equilibria: The 31P NMR spectroscopic investi-
gations of the solvent-dependent equilibria were carried out with
150 mg of each phosphane oxide dissolved in 0.7 mL of the chosen
solvent in an NMR tube. The measurements were repeated on two
consecutive days to observe possible changes in the integrals.
Bis(tetrafluoropyridyl)(diethylamino)phosphane: At –78 °C, a 1.6 m
n-butyllithium solution (29.0 mL, 46.4 mmol) in hexane was added
to a solution of p-tetrafluoropyridine (6.8 g, 45.1 mmol) in diethyl
ether (170 mL). After stirring the reaction mixture for 1 h at
–78 °C, the temperature was raised to –30 °C for 15 min to com-
plete the reaction. After cooling to –78 °C, dichloro(diethylamino)-
phosphane (3.9 g, 22.4 mmol) in diethyl ether (15 mL ) was added.
The mixture was warmed to room temperature and the precipitates
were removed by filtration. After evaporation of the solvent, the
product was obtained by vacuum distillation at 98 °C as a yellow
liquid in 88% yield (8.1 g, 19.9 mmol). 1H NMR (300.13 MHz,
CDCl3): δ = 3.20 [dq, 3J(P,H) = 11, 3J(H,H) = 7 Hz, 4 H, CH2],
1.00 [t, 3J(H,H) = 7 Hz, 6 H, CH3] ppm. 13C NMR (CDCl3,
75.47 MHz): δ = 143.4 [dm, 1J(C,F) = 249 Hz, C-2, C-6], 141.2
[dm, 1J(C,F) = 256 Hz, C-3, C-5], 132.0 [dtt, 1J(P,C) = 46, 2/3J(F,C)
= 20/3 Hz, C-4], 47.4 [tdq, J(C,H) = 136, J(P,C) = 18, J(C,H) =
4 Hz, CH2], 14.0 [qdt, 1J(C,H) = 126, 2J(P,C) = 4, 2J(C,H) = 3 Hz,
CH3] ppm. 19F NMR (282.40 MHz, CDCl3): δ = –136.1 (m, 3-F,
5-F), –90.5 (m, 2-F, 6-F) ppm. 31P NMR (111.92 MHz, CDCl3): δ
= 21.2 [quint-quint (tridec), 3J(P,F) = 22, 3J(P,H) = 11 Hz] ppm.
MS (EI, 20 eV): m/z (%) = 404 (41) [(C5NF4)2PNHEt2]+, 389 (100)
[(C5NF4)2PNHEtMe]+, 361 (13) [(C5NF4)2PNMe]+, 332 (4)
[(C5NF4)2P]+, 240 (14) [(C5NF4)PNEtMe]+. C14H10F8N3P (403.2):
calcd. C 41.70, H 2.49, N 10.42; found C 42.18, H 2.24, N 10.62.
X-ray Structure Determination: The crystal data for 3 were collected
with a Bruker Nonius–Kappa CCD diffractometer using graphite-
monochromated Mo-Kα radiation (71.073 pm). The structure was
solved by direct methods and refined by full-matrix least-square
cycles (programs SHELXS-97 and SHELXL-97).[17] Details of the
crystallographic measurements can be found in Table 2.
Table 2. Crystal data and refinement characteristics for phosphane
oxide 3.
[2,4-(CF3)2C6H3]2P(O)H (3)
1
2
2
Empirical formula
a [pm]
b [pm]
C16H7F12OP
1985.0(1)
1823.1(1)
2871.7(1)
93.06(1)
10377.5(2)
24
c [pm]
β [°]
V [106 pm3]
Z
Dx [gcm–3]
Crystal system
Space group
Shape/color
Crystal size [mm3]
T [K]
1.821
monoclinic
C2/c (No. 15)
column/colorless
0.30ϫ0.30ϫ0.26
100(2)
θ range
Index range
3.04/30.00
–27 Յ h Յ 27
–25 Յ k Յ 25
–40 Յ l Յ 40
126453
Total data collected
Unique data
15098
Observed data (I Ͼ 2σ)
μ [mm–1] (numerical)
Tmin/max
Absorption correction
R1/wR2 [IϾ2σ(I)]
R1/wR2 (all data)
11347
0.289
0.9287/0.9184
multi-scan
0.043/0.104
0.064/0.115
1.045
0.046
0.840/–0.624
5616
Bis(tetrafluoropyridyl)phosphane Oxide (2): Bis(tetrafluoropyrid-
yl)aminophosphane (2.11 g, 12.0 mmol) was dissolved in toluene
(15 mL) and extracted three times with conc. hydrochloric acid
(15 mL) at 0 °C. The solvent of the resulting organic phase was
removed in vacuo to yield 1.27 g (70%, 8.4 mmol) of bis(tetra-
fluoropyridyl)phosphane oxide (2) as a colorless solid (m.p. 94 °C).
Goodness of fit (Sall
R(int.)/R(σ)
)
NMR spectroscopic data for (C5NF4)2P(O)H in CD3CN: 1H NMR
(300.13 MHz, CD3CN): δ = 8.90 [d, 1J(P,H) = 605 Hz, (C5NF4)2P-
(O)H] ppm. 13C{19F} NMR (CD3CN, 75.47 MHz): δ = 121.8 [dd,
1J(P,C) = 91, 2J(C,H) = 13 Hz, C-4] ppm. 13C NMR (CD3CN,
100 MHz): δ = 142.5 [m, 1J(C,F) ≈ 250 Hz, C-3, C-5], 143.5 [m,
Δρmax./min. [106 epm–3]
F(000)
CCDC-833430 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
1J(C,F)
≈
250 Hz, C-2, C-6] ppm. 19F NMR (282.40 MHz,
CD3CN): δ = –136.7 (m, 3-F, 5-F), –90.6 (m, 2-F, 6-F) ppm. 31P
NMR (111.92 MHz, CD3CN): δ = –19.9 [d, 1J(P,H) = 605 Hz,
(C5NF4)2P(O)H] ppm.
NMR spectroscopic data for (C5NF4)2P–OH in CD3CN: 1H NMR
(300.13 MHz, CD3CN): δ = 6.60 [s, (C5NF4)2P-OH] ppm. 13C{19F}
NMR (CD3CN, 75.47 MHz): δ = 133.0 [d, 1J(P,C) = 48 Hz, C-
Acknowledgments
1
4] ppm. 13C NMR (CD3CN, 75.47 MHz): δ = 141.7 [dm, J(C,F)
Merck KGaA (Darmstadt, Germany) is acknowledged for finan-
cial support. We want to thank Dr. N. Ignatiev (Merck KGaA),
= 256, 2J(P,C) = 12 Hz, C-3, C-5], 143.3 [dm, 1J(C,F) = 246 Hz,
C-2, C-6] ppm. 19F NMR (282.40 MHz, CD3CN): δ = –137.4 (m, Prof. L. Weber, and Dr. J. Bader for helpful discussions.
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© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2011, 5523–5529

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Received: September 15, 2011
Published Online: November 15, 2011
Eur. J. Inorg. Chem. 2011, 5523–5529
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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