Stable phosphinous acids

Article abstract of DOI:10.1016/j.jorganchem.2004.09.041

The electronic properties of organyl element compounds are strongly influenced by the electronic characteristics of the organic substituents. The bonding of two CF₃ groups to a phosphorus atom effects a drastically decreased basicity. That is the phosphorus atom is the least basic centre in the compound (CF₃)₂POH. This compound, synthesized in 1960 by Burg and Griffiths, is the only known example of a phosphinous acid, although there should be a general interest in this class of compounds. However, only a few investigations have been reported which may be explained by the tedious and risky synthesis. In this paper a safe one step and high yield synthesis of (CF₃)₂POH is described. The compound (C₆F ₅)₂POH, originally claimed as a phosphinous acid, is proved to exist at room temperature exclusively in the tautomeric oxide form. (C₆F₅)₂P(O)H crystallizes in the triclinic space group P1? (no. 2) with a 992.9(1) pm; b 1501.9(2) pm; c 1539.4(2) pm; α 117.48(1)°; β 100.39(1)°; γ 96.02(1)° and Z 6. Quantum chemical investigations prove the electron withdrawing effect of s-triazinyl groups (1,3,5-triazin-4-yl derivatives) to be much stronger than that of pentafluorophenyl groups. Quantum chemical calculations at the B3PW91/6-311G(3d,p) level of theory predict for the bis(s-triazinyl) derivative (C₃N₃H₂)₂POH the phosphinous acid isomer to be favored by ΔE_ZP = 22 kJ/mol in relation to the corresponding phosphane oxide isomer. The phosphinous acid (CF₃) ₂POH (C_s symmetry) is favored at the same level of theory by about ΔE_ZP = 14 kJ/mol compared with the phosphane oxide structure (C_s symmetry).

Full text of DOI:10.1016/j.jorganchem.2004.09.041

Journal of Organometallic Chemistry 690 (2005) 2382–2387
www.elsevier.com/locate/jorganchem
Stable phosphinous acids
*
Berthold Hoge , Stefan Neufeind, Sonja Hettel, Waldemar Wiebe, Christoph Thosen
¨
Institut fu¨r Anorganische Chemie, Universita¨t zu Ko¨ln, Greinstr. 6, D-50939 Ko¨ln, Germany
Received 21 June 2004; accepted 10 September 2004
Abstract
The electronic properties of organyl element compounds are strongly influenced by the electronic characteristics of the organic
substituents. The bonding of two CF3 groups to a phosphorus atom effects a drastically decreased basicity. That is the phosphorus
atom is the least basic centre in the compound (CF3)2POH. This compound, synthesized in 1960 by Burg and Griffiths, is the only
known example of a phosphinous acid, although there should be a general interest in this class of compounds. However, only a few
investigations have been reported which may be explained by the tedious and risky synthesis. In this paper a safe one step and high
yield synthesis of (CF3)2POH is described. The compound (C6F5)2POH, originally claimed as a phosphinous acid, is proved to exist
ꢀ
at room temperature exclusively in the tautomeric oxide form. (C6F5)2P(O)H crystallizes in the triclinic space group P1 (no. 2) with a
992.9(1) pm; b 1501.9(2) pm; c 1539.4(2) pm; a 117.48(1)°; b 100.39(1)°; c 96.02(1)° and Z 6.
Quantum chemical investigations prove the electron withdrawing effect of s-triazinyl groups (1,3,5-triazin-4-yl derivatives) to be
much stronger than that of pentafluorophenyl groups. Quantum chemical calculations at the B3PW91/6-311G(3d,p) level of theory
predict for the bis(s-triazinyl) derivative (C3N3H2)2POH the phosphinous acid isomer to be favored by DEZP = 22 kJ/mol in relation
to the corresponding phosphane oxide isomer. The phosphinous acid (CF3)2POH (Cs symmetry) is favored at the same level of the-
ory by about DEZP = 14 kJ/mol compared with the phosphane oxide structure (Cs symmetry).
Ó 2004 Elsevier B.V. All rights reserved.
Keywords: Phosphinous acids; Phosphane oxide; Trifluoromethyl; Pentafluorophenyl
1. Introduction
The electronic properties of perfluoroorganyl element
compounds are strongly influenced by the electronic
characteristics of the perfluoroorganyl groups. The high
group electronegativities of perfluoroorganyl groups ef-
fect a strong electron withdrawing effect. The group elec-
tronegativity of a trifluoromethyl group for example
exceeds the electronegativity of a chlorine atom [3].
Therefore perfluoroorganylphosphanes exhibit higher
ionisation energies [4] and reduced Lewis basicities [5]
in comparison with their non-fluorinated counterparts.
The high Lewis acidities [6] of perfluoroorganylphos-
phane derivatives are depicted by the readily addition
of nucleophilic groups forming phosphoranides, PRꢀ4 [7].
The bonding of two CF3 groups to a phosphorus
atom effects a drastically decreased basicity. That is
the phosphorus atom is the least basic centre in the com-
pound (CF3)2POH. This compound is, to our knowl-
Phosphinous acids R2POH (R = Alkyl and Aryl)
with a trivalent central phosphorus atom are unstable
in relation to the tautomeric pentavalent phosphorus
oxides [1]:
O
R2P-O-H
R2P
ð1Þ
H
R = Alkyl, Aryl
However, it is possible to stabilize phosphinous acid
derivatives by coordination to transition metal com-
plexes [2].
*
Corresponding author. Tel.: +49 221 470 3911; fax: +49 221 470
5196.
E-mail address: b.hoge@uni-koeln.de (B. Hoge).
0022-328X/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2004.09.041

B. Hoge et al. / Journal of Organometallic Chemistry 690 (2005) 2382–2387
2383
edge [8], the only well characterized example of a phos-
phinous acid, which is even stable at ambient
temperature
Bis(trifluoromethyl)halogenophosphanes like (CF3)2PBr
are accessible by reacting (CF3)2PNEt2 with gaseous
HBr. Bis(trifluoromethyl)bromophosphane reacts easily
with H2O to yield (CF3)2POH and HBr
O
F3C
H2O
ƒƒ!
ꢀHBr
2HBr
ƒƒƒƒƒ!
ðCF3Þ P–NEt2
ðCF Þ P–Br
ðCF Þ P–O–H
ð2Þ
P
OH
P
3
3
2
2
2
F3C
F3C
ꢀ½NEt2H2ꢁBr
H
F3C
ð6Þ
Although this extraordinary compound, which was syn-
thesized already in 1960 by Burg and Griffiths, should
exhibit an outstanding chemistry, due to the tedious
and risky synthesis [9,10], only a few investigations have
been reported.
The reaction of (CF3)2PI with silver carbonate results
in a 80% yield of the diphosphoxane (CF3)2POP(CF3)2.
Before the product can be isolated via fractional con-
densation, the part of (CF3)2PI which has not reacted
has to be converted by AgCl to the removable
(CF3)2PCl
Attempts to separate (CF3)2POH from the reaction mix-
ture were less successful, and yielded a mixture of
(CF3)2POH and its product of continued hydrolysis
compound CF3PH(O)OH [12]. Under strong acidic con-
ditions (CF3)2POH is stable towards hydrolysis. In neu-
tral or even basic conditions (CF3)2POH is very sensitive
towards hydrolysis. During the work up of the reaction
mixture of (CF3)2PBr and H2O (cf. Eq. (6)), via frac-
tional condensation, we obtained
a mixture of
(CF3)2POH (b.p. 61 °C [9]) and H2O. In the absence
of HBr, this mixture, upon warming to room tempera-
ture, immediately reacts according to
2ðCF3Þ PIþAg2CO3 ! ðCF3Þ POPðCF3Þ þCO2 þ2AgI
2
2
2
ð3Þ
O
P
The diphosphoxane (CF3)2POP(CF3)2 represents a un-
ique compound showing no rearrangement to a phos-
phane oxide. It can be cleaved by gaseous HCl
yielding (CF3)2PCl and (CF3)2POH (86 h, 100 °C).
The phosphinous acid is separated in a 90% yield via a
trap to trap condensation of the gaseous mixture, which
reacts very violently on contact with air
(CF3)2P-O-H + H2O
HCF3 +
F3C
OH
ð7Þ
H
The acidic cleavage of the P–N bond in (CF3)2P–
NEt2 and the following hydrolysis (cf. Eq. (6)) can be
performed in one step in a two phase system, treating
a CH2Cl2 solution of (CF3)2PNEt2 with concentrated
aqueous HCl. Nevertheless, after the work up of the
CH2Cl2 solution of (CF3)2POH via fractional condensa-
tion we end up with a mixture of (CF3)2POH and
CF3PH(O)OH. In fact it is possible to separate these
two compounds, but the yields are low.
In 1982 Dahl postulated the existence of reactive pho-
sphenium derivatives R2PþCF3SO3ꢀ, cleaving a P–N
bond of R2PNMe2 derivatives with R = Ph, NMe2 on
treatment with trifluoromethylsulfonic acid [13]. On
treatment of (CF3)2PNEt2 with CF3SO3H we postulate
the formation of a comparable compound (CF3)2P–O–
SO2CF3 though with a covalent rather than an ionic
bonding situation. Indeed, the mixed anhydride
(CF3)2P–O–SO2CF3 could not be observed, but its prod-
ucts of rearrangement, the symmetric anhydrides
(CF3)2P–O–P(CF3)2 and CF3SO2–O–SO2CF3
2ðCF3Þ P–O–PðCF3Þ þ HCl
2
2
! ðCF3Þ P–O–H þ Cl–PðCF3Þ
ð4Þ
2
2
The presumed (CF3)2POH structure was supported by
the infrared spectrum showing the O–H stretching fre-
quency at 3620 cmꢀ1 and the very strong P–O stretching
at 854 cmꢀ1. The tautomeric oxide form (CF3)2P(O)H
can be excluded by the absence of a P@O stretching
band, which should be expected near 1285 cmꢀ1 by com-
parison with 1328 cmꢀ1 for (CF3)3P@O and 1415 cmꢀ1
for F3P@O [9]. A deeper inspection of the infrared spec-
trum of (CF3)2POH reveals two O–H stretching frequen-
cies, which were attributed to rotational isomers [10].
2. Improved synthesis of the bis(trifluoromethyl) phosphi-
nous acid
To explore the chemistry of the extraordinary bis(tri-
fluoromethyl)phosphinous acid a safer and easier access
would be desirable. An easily and safely manageable
bis(trifluoromethyl)phosphane derivative is (CF3)2P-
NEt2 which is synthesized in a 200 g scale via the Rup-
pert procedure – reacting Cl2PNEt2 with CF3Br in the
presence of P(NEt2)3 [11]:
2 HOSO2CF3
(CF3)2P-NEt2
(CF3)2P-O-SO2CF3
x 2
- [NEt2H2]SO3CF3
CF3SO2-O-SO2CF3 + (CF3)2P-O-P(CF3)2
2CF3–Br=PðNEt2Þ3
Cl2P–NEt2
ðCF Þ P–NEt
ð5Þ
ƒƒƒƒƒƒƒƒ!
3
2
2
ð8Þ
ꢀ2½PðClÞðNEt2Þ3ꢁBr

2384
B. Hoge et al. / Journal of Organometallic Chemistry 690 (2005) 2382–2387
ppm
103.0 102.0 101.0 100.0
99.0
98.0
97.0
96.0
95.0
Fig. 1. Experimental (top) and calculated (bottom) 31P NMR spectrum (81.01 MHz) of (CF3)2POP(CF3)2 (compare text).
The formed diphosphoxane (CF3)2POP(CF3)2 is charac-
terized by its very characteristic 19F and 31P NMR reso-
nances. The experimental higher order 31P NMR
resonance is shown in the upper trace of Fig. 1. The
(CF3)2P-NEt2 + 3 TosOH
Tos-O-Tos + [NEtH2]+TosO-
(CF3)2POH
+
4
2J(PF) and the long range J(PF) couplings with values
ð10Þ
The reaction pathway of the one step and high yield syn-
thesis of (CF3)2POH is described in Scheme 1.
of 92 and 5 Hz, respectively, give rise to magnetic non-
equivalence of the two P(CF3)2 moieties, resulting in a
high order [AX6]2 spin system with A = P and X = F.
The experimental high order 31P NMR spectrum (Fig.
1) is in excellent agreement with the calculated spectrum
displayed in the bottom trace. Because 2J(PF) couplings
are, in contrast to the always negative 1J(PF) couplings,
positive [14], the analysis of the 31P NMR spectrum as
an A6A06XX0 spin system favours a positive sign for
3. Diarylphosphinous acids and outlook
In 1966 Magnelli et al. [16] postulated the phosphin-
ous acid (C6F5)2POH to be formed in the hydrolysis of
(C6F5)2PCl
4
the J(PF) coupling. For spin systems which are based
on a AA0XX0 system only the relative signs of the
AX- and AX0 couplings are assignable [15].
ðC6F5Þ PCl þ H2O ! ðC6F5Þ POH þ HCl
ð11Þ
2
2
The composition of the crystalline white solid was
proved by elemental analysis. Unfortunately, the
authors were not able to assign any vibrational mode
in the observed infrared spectrum to identify the com-
pound as the phosphinous acid or phosphane oxide.
Therefore they measured a proton magnetic resonance
spectrum in CDCl3. The two signals observed at 4.0
and 13.3 ppm were assigned to the phosphane oxide
and phosphinous acid, respectively. Following these
The phosphinous acid (CF3)2POH is always observed
as a side product of the reaction of (CF3)2PNEt2 with
two equivalents of CF3SO3H, caused by the reaction
of (CF3)2POP(CF3)2 with CF3SO3H
ðCF3Þ P–O–PðCF3Þ þ HOSO2CF3
2
2
Â
Ã
! ðCF3Þ P–O–SO2CF3 z þ ðCF3Þ POH
ð9Þ
2
2
assignments
they
described
the
compound
Finally, the treatment of (CF3)2PNEt2 with at least three
equivalents of carefully dried p-toluenesulfonic acid (To-
(C6F5)2POH as an equilibrium mixture of the two tau-
tomeric forms:
sOH) results in
a
complete transformation of
(CF3)2PNEt2 into (CF3)2POH. If the less volatile solvent
1,6-dibromohexane is used, the product is removed in
vacuo as the only volatile compound in a 90% yield
O
ð12Þ
(C6F5)2P
(C6F5)2P-O-H
H

B. Hoge et al. / Journal of Organometallic Chemistry 690 (2005) 2382–2387
2385
O
S
O
S
Et2N-P(CF3)2 + 2
OH
O
P(CF3)2
- NEt2H2+ Tos-O-
O
O
(Tos-OH)
x2
(CF3)2P-O-P(CF3)2 + Tos-O-Tos
+ Tos-OH
x2
Tos-O-P(CF3)2
(CF3)2POH
+
Scheme 1. Reaction pathway of the improved synthesis of (CF3)2POH.
Because the compound (C6F5)2POH is sensitive towards
hydrolysis in basic conditions we treated a CH2Cl2 solu-
tion of (C6F5)2PBr with concentrated aqueous HCl at 0
°C. Evaporation of the organic phase yields the product
in a 80% yield as a white solid. The proton magnetic res-
onance spectrum of the product dissolved in CDCl3
exhibits, in contrast to MagnelliÕs observations, two sig-
nals at 7.3 and 10.1 ppm – a doublet centered at 8.7 ppm
with a splitting of 560 Hz. The 31P NMR spectrum
exhibits a doublet at ꢀ18.5 ppm with a 1J(PH) coupling
of 560 Hz. Therefore the equilibrium (12) is shifted to
the right side.
The phosphane oxide (C6F5)2P(O)H adds at room
temperature to the carbon oxygen double bond of benz-
aldehyde. The product, a white crystalline solid, exhibits
one 31P NMR resonance at 22.7 ppm, while the 19F
NMR spectrum shows six resonances, three for each
diastereomeric C6F5 ring
O
P
OH
O
O
H
(C6F5)2P
+
H
F5C6
F5C6
Ph
H
Ph
δ(31P) 22.7
The two 1H NMR signals, observed by Magnelli
et al., exhibit a difference of 9.3 ppm. Assuming, that
these authors used a 60 MHz NMR spectrometer, this
difference is calculated to 558 Hz. Therefore Magnelli
et al. collected the right data, a doublet at 8.6 ppm
ð13Þ
The reaction mixture of (C6F5)2P(O)H and acetone
exhibits, surprisingly, three resonances: one doublet
1
with a J(PH) coupling of 558 Hz, which are compa-
rable with our data, but the interpretation of these
data by Magnelli et al. is wrong. The multinuclear
NMR spectra of the compound (C6F5)2POH dissolved
in CDCl3 exhibit only signals for the phosphane
oxide.
The vibrational spectra of the solid compound sup-
port the formulation of a phosphane oxide, interpreting
the signals at 1209 and 2472 cmꢀ1 as the P@O and P–H
valence modes, respectively. Further evidence is ob-
tained by a single crystal X-ray structure analysis. The
phosphane oxide (C6F5)2P(O)H crystallizes in the tri-
O1
F10
C12
F5
P1
C6
H1
C10
C1
C2
C7
F6
C9
F7
F1
ꢀ
clinic space group P1. The averaged P–O distance of
Fig. 2. Molecular structure of one of three crystallographic independ-
ent (C6F5)2P(O)H molecules showing the atom numbering scheme and
thermal ellipsoids (50%). Selected bond lengths (pm) and angles (°):
P(1)–O(1) 147.6(3); P(1)–H(1) 133(3); P(1)–C(1) 181.6(3); P(1)–C(7)
181.8(3); C(1)–P(1)–C(7) 105.9(1); C(1)–P(1)–O(1) 111.6(1); C(7)–P(1)–
O(1) 113.7(1).
the three crystallographically independent molecules of
146.9 pm describes a typical P–O double bond. The col-
lected X-ray data allowed an isotropic refinement of the
hydrogen atoms bonded to the phosphorus atoms (cf.
Fig. 2).

2386
B. Hoge et al. / Journal of Organometallic Chemistry 690 (2005) 2382–2387
for unchanged (C6F5)2P(O)H at ꢀ19.1 ppm, a singlet at
29.2 ppm for the addition product (C6F5)2P(O)-
C(OH)Me2 and a quintet at 74.5 ppm (3J(PF) = 34
Hz). On evaporation of the reaction mixture to dryness,
the remaining white solid exhibits the same weight as the
starting material of (C6F5)2P(O)H. Dissolving this resi-
due in CDCl3 and examining its multinuclear NMR
spectra reveals exclusively the NMR resonances for
the phosphane oxide (C6F5)2P(O)H. Evaporation to
dryness and redissolving of the residue in acetone again
results in the described three resonances in the 31P NMR
spectrum.
The solvent dependent tautomeric equilibrium be-
tween (C6F5)2P(O)H and (C6F5)2P–O–H does not sur-
prise, if DFT calculations at the B3LYP/6-311G(2d,p)
level are taken into account. The phosphinous acid is
favored by only DEZPE 1.7 kJ/mol. The relative energetic
difference between the tautomeric forms of the bis(tri-
fluoromethyl) derivatives is calculated at the B3PW91/
6-311G(3d,p) level to be DEZPE 14 kJ/mol. This may ex-
plain why (CF3)2POH does not exhibit a solvent
dependent tautomeric equilibrium.
In order to synthesize a diarylphosphinous acid
which is more stabilized towards the tautomeric diaryl-
phosphane oxide than the C6F5 derivative, it is necessary
to increase the electron withdrawing effect of the aryl
groups.
In a recent paper we demonstrated that the phospho-
rus-carbon distances in corresponding arylphospha-
nides, ArPHꢀ, are a useful indicator for the evaluation
of the electron withdrawing effect of aryl groups exerted
on a phosphorus atom. Corresponding quantum chem-
ical calculations indicate increasing electron withdraw-
ing capacity of perfluoroaryl groups on successive
substitution of fluorine atoms by CF3 groups or even
stronger on successive substitution of CF units by isolo-
bal nitrogen atoms [8]. Following these ideas the tetra-
fluoropyridin-4-yl substituent should exhibit a stronger
electron withdrawing capacity than a C6F5 group. This
explains why the phosphinous acid (C5NF4)2POH is fav-
ored by DEZPE 10.5 kJ/mol over the comparable phos-
phane oxide at the B3LYP/6-311G(2d,p) level. Both
compounds can be observed in an equilibrium within
the hydrolysis of P(C5NF4)3 under basic conditions:
To assign the 31P NMR resonance at 74.5 ppm the
1H, 19F and 31P NMR spectra of (C6F5)2P(O)H are
collected using different solvents. Solutions of
(C6F5)2P(O)H in toluene, dichloromethane, chloroform
and acetonitrile exhibit only one resonance in the 31P
NMR spectrum – a doublet at around ꢀ19 ppm with
a
1J(PH) coupling in the range of 560–600 Hz for
the phosphane oxide (cf. Table 1.). Solutions of
(C6F5)2P(O)H in methanol, DME, THF, Ether, DMF
and DMSO exhibit an additional resonance with an
increasing relative intensity at around 74 ppm: a quintet
with a 3J(PF) coupling of around 34 Hz. This resonance,
which is comparable to the resonance of (CF3)2POH
(d(31P) 79.0 (sept); 2J(PF) 83 Hz), is assigned to the
phosphinous acid. The 1H NMR resonance of
(C6F5)2POH in THF-d8, a singlet at 7.0 ppm at room
temperature exhibits a temperature depending shift from
5.5 to 8.1 ppm between +50 and ꢀ70 °C. The ratio of the
two tautomeric forms, the phosphane oxide and the
phosphinous acid reveals no temperature dependency.
1
The relative intensities of H, 19F and 31P NMR reso-
nances of the tautomeric forms exhibit no significant
temperature dependency within the investigated temper-
ature range.
(C5NF4)2P-O-H
δ(31P) 75.8 (m)
Na2CO3
P(C5NF4)3 + H2O
HC5NF4 +
δ(31P) -8.1 (d)
O
(C5NF4)2P
H
1J(PH) 559 Hz
ð14Þ
Table 1
Solvent dependent tautomeric equilibrium between bis(pentafluoro-
phenyl)phosphane oxide and the bis(pentafluorophenyl)phosphinous
Investigations, to establish whether the compound
(C5NF4)2POH favors the tautomeric form of a phosph-
inous acid or the phosphane oxide form in the solid
state, are in progress.
a
acid
O
H
Solvent
(C6F5)2P
(C6F5)2P-O-H
Threefold substitution of CF units in C6F5 groups by
isolobal nitrogen atoms will create s-triazinyl substitu-
ents (1,3,5-triazin-2-yl). Using the method to evaluate
the electron withdrawing effect of aryl groups exerted
on a phosphorus atom by means of the phosphorus-car-
bon distances in corresponding arylphosphanides,
ArPHꢀ, leads to the prediction that an s-triazinyl group
will show a much stronger electron withdrawing effect
than a tetrafluoropyridinyl or a pentafluorophenyl
group. It seems to be reasonable that even non fluori-
nated s-triazinyl groups exhibit a strong electron
Toluene
Dichloromethane
Chloroform
Acetonitrile
Methanol
DME
100
0
0
100
100
100
82
0
0
18
43
55
60
67
76
57
45
THF
Ether
40
33
DMF
DMSO
24
a
Percentages obtained from the integration of the 31P and 19F
NMR spectra.

B. Hoge et al. / Journal of Organometallic Chemistry 690 (2005) 2382–2387
2387
withdrawing effect, comparable to that of a CF3 group
[8].
Quantum chemical calculations at the B3PW91/6-
References
[1] D.E.C. Corbridge, Phosphorus, An Outline of its Chemistry,
Biochemistry and Uses, fifith ed., Elsevier Science B.V., Amster-
dam, 1995, p. 336.
311G(3d,p) level of theory predict for a bis(s-triazinyl)
derivative (I) (cf. Eq. (15)) that the phosphinous acid
isomer to be favored above the corresponding phos-
phane oxide isomer. Besides the strong electron with-
drawing effect of the s-triazinyl group, intramolecular
OH–N bridges with distances of 216 and 286 pm (cf.
Eq. (15)) seem to be responsible for the stabilization of
the phosphinous acid (C3N3H2)POH of DEZP = 22 kJ/
mol (C1 symmetry at B3PW91/6-311G(3d,p) level) with
respect to the corresponding phosphane oxide isomer
(Cs symmetry), (cf. Eq. (15)) [8]
[2] For example: C.S. Kraihanzel, C.M. Bartish, J. Am. Chem. Soc.
94 (1972) 3572;
E. Lindner, B. Schilling, Chem. Ber. 110 (1977) 3266.
[3] S.G. Bratch, J. Chem. Educ. 65 (1988) 223;
J.E. Huheey, J. Phys. Chem. 69 (1965) 3284.
[4] For example: R. Gleiter, W.D. Goodmann, W. Scha¨fer, J. Grobe,
J. Apel, Chem. Ber. 116 (1983) 3745;
S. Elbel, H.T. Dieck, J. Fluorine Chem. 19 (1982) 349.
[5] For example: J. Apel, J. Grobe, Z. Anorg. Allg. Chem. 453 (1979)
53.
[6] For example: A. Kolomeitsev, M. Go¨rg, U. Dieckbreder, E.
Lork, G.-V. Ro¨schenthaler, Phosphorus Sulfur Silicon Relat.
Elem. 109–110 (1996) 597;
R.M.K. Deng, K.B. Dillon, W.S. Sheldrick, J. Chem. Soc.,
Dalton Trans. (1990) 551.
[7] G.-V. Ro¨schenthaler, O. Shyshkov, A. Kolomeitsev, B. Hoge, in:
16th Winter Fluorine Conference, St. Pete Beach, Florida, Paper
54, 2003;
A. Kolomeitsev, M. Go¨rg, U. Dieckbreder, E. Lork, G.-V.
Ro¨schenthaler, Phosphorus Sulfur Silicon Relat. Elem. 109–110
(1996) 597;
ð15Þ
K.B. Dillon, Chem. Rev. 94 (1994) 1441;
R.M.K. Deng, D.B. Dillon, W.S. Sheldrick, J. Chem. Soc.,
Dalton Trans. (1990) 551;
Conceivable mesoionic compounds, formed by an intra-
molecular acid base reaction of the acidic function of the
phosphinous acid (C3N3H2)2POH with an ortho or para
oriented basic function of s-triazinyl substituents are less
stable by about 80 kJ/mol at the same level of theory [8].
The realization of these predictions implies that our
future work will be focused on a general investigation
of the s-triazinyl phosphorus chemistry.
R. Ali, K.B. Dillon, J. Chem. Soc., Dalton Trans. (1990) 2593.
[8] B. Hoge, C. Tho¨sen, T. Herrmann, P. Panne, I. Pantenburg, J.
Fluorine Chem. 125 (2004) 831.
[9] J.E. Griffiths, A.B. Burg, J. Am. Chem. Soc. 82 (1960) 1507;
J.E. Griffiths, A.B. Burg, J. Am. Chem. Soc. 84 (1962) 3442.
[10] R.C. Dobbie, B.P. Straughan, Spectrochim. Acta 27 (1971) 255.
[11] A. Kolomeitsev, M. Go¨rg, U. Dieckbreder, E. Lork, G.-V.
Ro¨schenthaler, Phosphorus Sulfur Silicon 109–110 (1996) 597.
´
[12] H.T. Emeleus, R.N. Haszeldine, R.C. Paul, J. Chem. Soc. (1955)
563.
Acknowledgements
[13] O. Dahl, Tetrahedron Lett. 23 (1982) 1493.
[14] S. Berger, S. Braun, H.-O. Kalinowski, NMR-Spektroskopie von
Nichtmetallen, Georg Thieme Verlag Stuttgart, New York, 1993,
p. 147.
We are grateful to Prof. Dr. D. Naumann for his gen-
erous support. Dr. K. Glinka is acknowledged for help-
ful discussions. The Deutsche Forschungsgemeinschaft
(DFG) and the Fonds der Chemischen Industrie are
acknowledged for financial support.
[15] H. Gunther, in: NMR-Spektroskopie, third ed., Georg Thieme
¨
Verlag Stuttgart, New York, 1992, p. 175.
[16] D.D. Magnelli, G. Tesi, J.U. Lowe, W.E. McQuistion, Inorg.
Chem. 5 (1966) 457.