Fluorinated phosphorus compounds - Part 6. The synthesis of bis(fluoroalkyl) phosphites and bis(fluoroalkyl) phosphorohalidates

Article abstract of DOI:10.1016/S0022-1139(01)00468-7

Reaction of phosphorus trichloride with tert-butanol and fluoroalcohols gave bis(fluoroalkyl) phosphites (R_FO)₂P(O)H in 42-89% yield, where R_F = HCF₂CH₂, H(CF₂)₂CH₂, H(CF₂)₄CH₂, CF₃CH₂, C₂F₅CH₂, C₃F₇CH₂, (CF₃)₂CH, (FCH₂)₂CH, CF₃(CH₃)₂C, (CF₃)₂CH₃C, CF₃CH₂CH₂, C₄F₉CH₂CH₂ and C₆F₁₃CH₂CH₂. Treatment of these with chlorine in dichloromethane gave the bis(fluoroalkyl) phosphorochloridates (R_FO)₂P(O)Cl in 49-96% yield. The chloridate (CF₃CH₂O)₂P(O)Cl was isolated in much lower yield from the interaction of thionyl chloride with bis(trifluoroethyl) phosphite. Heating the latter in dichloromethane with potassium fluoride and a catalytic amount of trifluoroacetic acid gave the corresponding fluoridate (CF₃CH₂O)₂P(O)F in 84% yield. Treatment of bis(trifluoroethyl) phosphite with bromine or iodine gave the bromidate (CF₃CH₂O)₂P(O)Br and iodidate (CF₃CH₂O)₂P(O)I in 51 and 46% yield, respectively. The iodidate is the first dialkyl phosphoroiodidate to have been isolated and characterised properly - its discovery lags behind the first isolation of a dialkyl phosphorochloridate by over 130 years. The fluoroalkyl phosphoryl compounds are generally more stable than known unfluorinated counterparts.

Full text of DOI:10.1016/S0022-1139(01)00468-7

Journal of Fluorine Chemistry 113 ꢀ2002) 65±78
Fluorinated phosphorus compounds
Part 6. The synthesis of bisꢀ¯uoroalkyl) phosphites
and bisꢀ¯uoroalkyl) phosphorohalidates
Christopher M. Timperley*, Robert E. Arbon, Sally A. Saunders, Matthew J. Waters
Defence Science and Technology Laboratory, Chemical and Biological Defence Sciences, Porton Down, Salisbury, Wiltshire SP4 0JQ, UK
Received 18 June 2001; accepted 25 July 2001
Abstract
Reaction of phosphorus trichloride with tert-butanol and ¯uoroalcohols gave bisꢀ¯uoroalkyl) phosphites ꢀRFO)2PꢀO)H in 42±89% yield,
where RF ˆ HCF2CH2, HꢀCF2)2CH2, HꢀCF2)4CH2, CF3CH2, C2F5CH2, C3F7CH2, ꢀCF3)2CH, ꢀFCH2)2CH, CF3ꢀCH3)2C, ꢀCF3)2CH3C,
CF3CH2CH2, C4F9CH2CH2 and C6F13CH2CH2. Treatment of these with chlorine in dichloromethane gave the bisꢀ¯uoroalkyl)
phosphorochloridates ꢀRFO)2PꢀO)Cl in 49±96% yield. The chloridate ꢀCF3CH2O)2PꢀO)Cl was isolated in much lower yield from the
interaction of thionyl chloride with bisꢀtri¯uoroethyl) phosphite. Heating the latter in dichloromethane with potassium ¯uoride and a
catalytic amount of tri¯uoroacetic acid gave the corresponding ¯uoridate ꢀCF3CH2O)2PꢀO)F in 84% yield. Treatment of bisꢀtri¯uoroethyl)
phosphite with bromine or iodine gave the bromidate ꢀCF3CH2O)2PꢀO)Br and iodidate ꢀCF3CH2O)2PꢀO)I in 51 and 46% yield, respectively.
The iodidate is the ®rst dialkyl phosphoroiodidate to have been isolated and characterised properlyÐits discovery lags behind the ®rst
isolation of a dialkyl phosphorochloridate by over 130 years. The ¯uoroalkyl phosphoryl compounds are generally more stable than known
un¯uorinated counterparts. # 2002 Elsevier Science B.V. All rights reserved.
Keywords: Bisꢀ¯uoroalkyl) phosphite; Bisꢀtri¯uoroethyl) phosphorobromidate; Bisꢀ¯uoroalkyl) phosphorochloridate; Bisꢀtri¯uoroethyl) phosphoro¯uor-
idate; Bisꢀtri¯uoroethyl) phosphoroiodidate
1. Introduction
phates B [4], bisꢀ¯uoroalkyl) phosphoramidates C [4],
bisꢀ¯uoroalkyl) alkylphosphonates D [5] and trisꢀ¯uor-
oalkyl) phosphates E [6]. Attention has focused on their
biological [7] and physical properties [8] in a search for
novel ®re extinguishants [9].
Fluoroalkyl phosphoryl compounds contain the group
RFO±P=O. They have structures analogous to familiar
alkyl phosphoryl compounds, but in some instances, struc-
tures unparalleled in organophosphorus chemistry. The
¯uoroalkyl group, abbreviated to RF, is usually derived
from a ¯uoroalcohol. Since tri¯uoromethanol CF3OH is
unstable, decomposing to COF2 and HF, the lower mem-
bers are hypothetical with the exception of trisꢀtri¯uoro-
methyl) phosphate ꢀCF3O)3P=O; it is also unstable and
disproportionates over 3 days at 60 8C to give 3 mol of
¯uorophosgene COF2 and 1 mol of phosphorus oxy¯uoride
POF3 [1]. Stable phosphoryl molecules have primary or
sec-¯uoro-ester groups, e.g. CF3CH2O±P or ꢀCF3)2CHO±P.
Few with tert-¯uoro-ester groups have been prepared [2].
Compounds previously reported by us include dialkyl
¯uoroalkyl phosphates A [3], bisꢀ¯uoroalkyl) alkyl phos-
So far, investigation of ¯uoroalkyl phosphoryl com-
pounds of structure ꢀRFO)2PꢀO)X, where X is OR, NR2,
SR, etc. has been hampered by a lack of phosphorohalidate
reagents; only derivatives with RF ˆ CF3 and C2F5 have
been explored in any detail [4]. Here, we describe a
two-stage route to bisꢀ¯uoroalkyl) phosphites F and
* Corresponding author. Fax: ‡44-1980-613-834.
E-mail address: cmtimperley@dstl.gov.uk ꢀC.M. Timperley).
0022-1139/02/$ ± see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 1 1 3 9 ꢀ 0 1 ) 0 0 4 6 8 - 7

66
C.M. Timperley et al. / Journal of Fluorine Chemistry 113 *2002) 65±78
bisꢀ¯uoroalkyl) phosphorochloridates G starting from phos-
phorus trichloride.1
The analogous reaction with ¯uoroethanol takes place to
give ꢀFCH2CH2O)2PꢀO)H in 75% yield [18]. When the
alcohol contains many ¯uorine atoms, as in tri¯uoroethanol,
the trisꢀ¯uoroalkyl) phosphite is obtained [19,20]. The
difference in behaviour is due to the higher basicity of
the FCH2CH2O± oxygen atom compared to the CF3CH2O±
oxygen atom, and the greater propensity of the former group
to dealkylation:
PCl3 ‡ 3 CF3CH2OH no solvent
!
ꢀCF3CH2O†3P
To highlight synthetic applications of the new materials,
we prepared the series of bisꢀtri¯uoroethyl) phosphorohali-
dates H which offer exciting possibilities as phosphorylation
reagents.
À3HCl
78À80%
Routes to bisꢀ¯uoroalkyl) phosphites are shown in Fig. 1.
They include acidolysis of a tert-phosphite. Glacial acetic
acid is suitable ꢀroute 1A), but the by-product is the ¯uor-
oalkyl acetate. The use of phosphorous acid ꢀroute 1B)
avoids loss of a ¯uoroalkyl group. Other methods start with
phosphorus trichloride and involve dealkylation of the
alkoxy groups by liberated HCl. The scheme involving
methanol ꢀroute 1C) is not selective: some of the methanol
reacts with the product to give around 10% mixed phosphite
HꢀCF2)nCH2OꢀMeO)PꢀO)H; this must be removed by care-
ful fractionation. The tert-butanolysis of phosphorus
trichloride ꢀroute 1D) produces Cl2PꢀO)H which can add
two moles of ¯uoroalcohol to furnish the bisꢀ¯uoroalkyl)
phosphite. This route is the most economical and gives a
pure product. We investigated its wider applicability to the
synthesis of a range of bisꢀ¯uoroalkyl) phosphites.
The phosphoro¯uoridate is the ®fth, and the phosphoro-
bromidate the third, example of such ¯uoro-ester species.
Bisꢀtri¯uoroethyl) phosphoroiodidate is one of only two
dialkyl phosphoroiodidatesÐthe other being [ꢀCF3)2CHO]2-
PꢀO)IÐto have been isolated and characterised in a pure
state [10]: the corresponding un¯uorinated dialkyl phos-
phoroiodidates are stable only in solution.
o,a,a-Trihydroper¯uoroalcohols gave phosphites ꢀ1a±
3a) in acceptable yield. Curiously, phosphite 1a and the
2. Results and discussion
2.1. Synthesis of bis*fluoroalkyl) phosphites
Bisꢀ¯uoroalkyl) phosphites with identical ¯uoro-ester
groups are known; routes to mixed systems, RFOꢀR0FO†-
PꢀO†H, have not yet been devised. Of the former, ®ve appear
in the literature and all have primary ¯uoro-ester groups:
ꢀFCH2CH2O)2PꢀO)H [11], [HꢀCF2)nCH2O]2PꢀO)H, where
n ˆ 2, 4 or 6 [12±14], and ꢀCF3CH2O)2PꢀO)H [15] which is
available commercially [16]. The preparation of dialkyl
phosphites by alcoholysis of phosphorus trichloride has
been known for a long time and studied in detail. For
example, in the following scheme, the triethyl phosphite
®rst formed is dealkylated by liberated HCl to give diethyl
phosphite in high yield [17].
1 Some of this work was described in a lecture entitled ``The Synthesis
and Properties of some Fluoroalkyl Phosphoryl Compounds'', given by
one of the authors ꢀC.M.T.) at the 16th International Symposium of
Fluorine Chemistry, Durham University, UK, on 17 July 2000. In this
paper, we refer to compounds of structure ꢀRO)2PꢀO)H and ꢀRFO)2PꢀO)H
as dialkyl phosphites and bisꢀfluoroalkyl) phosphites. This nomenclature,
although correct, is somewhat old-fashioned; modern names are dialkyl
hydrogen phosphonates or bisꢀfluoroalkyl) hydrogen phosphonates ꢀor H-
phosphonates).
Fig. 1. Literature routes to bisꢀfluoroalkyl) phosphites.

C.M. Timperley et al. / Journal of Fluorine Chemistry 113 *2002) 65±78
67
Table 1
corresponding phosphorochloridate 1b ꢀsee Section 2.4) are
Experimental data for bisꢀfluoroalkyl) phosphites ꢀRFO)2PꢀO)H
only the second and third neutral molecules to be made that
contain the HCF2CH2O±P group. The ®rst, trisꢀdi¯uoroethyl)
phosphate ꢀHCF2CH2O)3P=O, was prepared by Swarts in
1909 from di¯uoroethanol, bromine and red phosphorus [21].
Compound
RF
Yield ꢀ%)
Boiling point
ꢀ8C/mmHg)
1a
2a
HCF2CH2
42
77
59
89
74
68
71
86
55
57
58
73
74
79/1
HꢀCF2)2CH2
HꢀCF2)4CH2
CF3CH2
119/0.06a
104/0.1
62/10b
76/10
69/2
3a
4a
5a
6a
C2F5CH2
C3F7CH2
7a
8a
ꢀCF3)2CH
62/8
ꢀFCH2)2CH
CF3ꢀCH3)2C
ꢀCF3)2CH3C
CF3CH2CH2
C4F9CH2CH2
C6F13CH2CH2
116/1
71/10
41/10
67/0.04
42/5
9a
10a
11a
12a
13a
Normal and branched ¯uoroalcohols gave phosphites
4a±13a. Steric effects are not too importantÐsec- and
tert-¯uoroalcohols underwent double substitution without
dif®culty. Dominance of electronic effects over steric effects
is a feature of ¯uoroalkyl phosphoryl chemistry and operates,
for example, during the ¯uoroalcoholysis of alkylphos-
phonic dichlorides [5].
136/0.02
a Previously made in 83 and 90% yield by heating [HꢀCF2)2CH2O]3P
with glacial acetic acid or phosphorous acid, respectively ꢀliterature bp 86±
87 8C/1 mmHg [12] and 117±119 8C/5 mmHg [13]).
b Previously made in 82% yield using a similar procedure ꢀliterature bp
43±44 8C/2 mmHg) [15].
have branched ¯uoro-ester groups. These effects have been
commented on before and are general for ¯uoroalkyl phos-
phoryl species [8].
In line with their un¯uorinated analogues, the bisꢀ¯uor-
oalkyl) phosphites show clear evidence of the PꢀO)H struc-
ture. A doublet is observed in the proton NMRspectrum for
the phosphorus-bonded hydrogen atom; the JPH coupling
constant lies between 714 and 795 Hz. Phosphorus chemical
shifts for 1a±13a range between À3.6 and 7.9 ppm. In the
infrared spectra, stretching vibrations for the P=O bond are
strong and occur at 1288±1221 cmÀ1 ꢀTable 2).
Un¯uorinated counterparts of bisꢀ¯uoroalkyl) phosphites
ꢀ1a±13a) are known [22], as are some chloro- or bromo-
analogues. Most can be distilled under vacuum, but some
cannot due to thermal instability. Pronounced effects are
seen among diisopropyl phosphites having chloro- or
bromo-ester groups: [ꢀClCH2)CH3CHO]2PꢀO)H is moder-
ately stable to heat [23], [ꢀClCH2)2CHO]2PꢀO)H has a
tendency to decompose on distillation [24], and [ꢀBrCH2)2-
CHO]2PꢀO)H and [ꢀClCH2)ꢀBrCH2)CHO]2PꢀO)H cannot be
distilled [23]. In contrast, bisꢀdi¯uoroisopropyl) phosphite
[ꢀFCH2)2CHO]2PꢀO)H ꢀ8a) distilled without decompo-
sition. Also, di-tert-butyl phosphite [ꢀCH3)3CO]2PꢀO)H
decomposes with great ease on distillation [25,26], but
the ¯uorologues2 [CF3ꢀCH3)2CO]2PꢀO)H ꢀ9a) and [ꢀCF3)2-
ꢀCH3)CO]2PꢀO)H ꢀ10a) distil without dif®culty. It can be
concluded that ¯uorinated species have enhanced thermal
stability.
The reaction of non a¯uoro-tert-butanol ꢀCF3)3COH pre-
cipitated a white wax that could not be analysed due to its
insolubility in organic solvents. The phosphite [ꢀCF3)3CO]2-
PꢀO)H is therefore inaccessible using the chemistry
described, but this is not surprising given the bulkiness
and poor nucleophilicity of the ¯uoroalcohol. Experiments
using penta¯uorophenol were also unsuccessful; analysis of
reaction mixtures by gas chromatography±mass spectrome-
try ꢀGC±MS) showed that the intermediate Cl2PꢀO)H did not
react, and no ꢀC6F5O)2PꢀO)H formed.
2.2. Physical properties of bis*fluoroalkyl) phosphites
Bisꢀ¯uoroalkyl) phosphites ꢀ1a±13a) are colourless
mobile liquids; compound 13a solidi®ed to an opaque white
glass when stored in a refrigerator, but rapidly melted on
warming to room temperature. Boiling points depend on the
nature of the ¯uoro-ester groups ꢀTable 1). Molecules with
HꢀCF2)nCH2O± groups have higher boiling points than those
with CnF2n‡1CH2O± groups. The lowest boiling species
2 The term `fluorologue', derived from the Greek word logos meaning
`ratio or proportion', is used here to denote a fluorinated analogue of a
hydrocarbon compound. Likewise, the term `hydrologue' can be suggested
for a hydrocarbon analogue of a fluorocarbon compound. Using this
terminology, CF4 is a fluorologue of CH4 ꢀand CH4 is a hydrologue of
CF4). Its adoption saves writing, e.g. `the fluorinated counterpart of' or
`the hydrocarbon analogue of', which becomes cumbersome.

Table 2
Spectroscopic data for bisꢀfluoroalkyl) phosphites ꢀRFO)2PꢀO)H ꢀNMRdata measured in CDCl
)
3
Compound 1H NMR d, J ꢀHz)
13C NMR d, J ꢀHz)
19F NMR d
31P NMR d IR n ꢀcmÀ1
)
GC±MS analysisa
1a
6.77 ꢀ1H, d, J ˆ 740, P±H),
112.4 ꢀtt, J ˆ 36, 249, CF2H),
À125.9 ꢀ4F, ddt, J ˆ 3, 55, 13, CF2H)
7.6
1456, 1429, 1375, 1329, 1263
ꢀP=O), 1086, 982, 838
C4H7F4O3P Mw 210
5.98 ꢀ2H, tt, J ˆ 3, 55, CF2H),
4.29 ꢀ4H, ddt, J ˆ 4, 10, 13, OCH2)
7.02 ꢀ1H, d, J ˆ 751, P±H),
5.95 ꢀ2H, tt, J ˆ 5, 52, CF2H),
4.48 ꢀ4H, dt, J ˆ 11, 11 plus
smaller coupling, OCH2)
63.3 ꢀbr, OCH2)
2a
113.8 ꢀdtt, J ˆ 7, 28, 251,
CF2), 109.3 ꢀtt, J ˆ 36, 249,
CF2H), 61.3 ꢀbr m, OCH2)
À136.8 ꢀ4F, d, J ˆ 52, CF2H),
À123.8 ꢀ4F, dt, J ˆ 2, 13, CF2)
7.4
1456, 1404, 1273 ꢀP=O), 1238,
1107, 984, 870, 837
C6H7F8O3P Mw 310
3a
7.06 ꢀ1H, d, J ˆ 757, P±H),
6.06 ꢀ2H, tt, J ˆ 5, 52, CF2H),
4.57 ꢀ4H, m, OCH2)
113.9 ꢀdtt, J ˆ 7, 28, 251, CF2),
107.5 ꢀtt, J ˆ 36, 249, CF2H),
110±109 ꢀm, CF2CF2),
À136.5 ꢀ4F, m, CF2H), À129,
7.3
1458, 1404, 1269 ꢀP=O), 1171,
1130, 987, 903, 806
C10H7F16O3P Mw 510
À124.3 and À119.2 ꢀ12F, m, CF2)
61.3 ꢀbr m, OCH2)
4a
5a
7.1 ꢀ1H, d, J ˆ 755, P±H),
4.46 ꢀ4H, m, OCH2)
122 ꢀdq, J ˆ 6, 227, CF3),
61.7 ꢀdt, J ˆ 5, 38, OCH2)
118.5 ꢀtq, J ˆ 36, 287, CF3),
111.4 ꢀdq, J ˆ 7, 256, CF2),
60.9 ꢀdt, J ˆ 6, 29, OCH2)
117.5 ꢀtq, J ˆ 33, 287, CF3),
113.3 ꢀdt, J ˆ 6, 34, CF2),
108.5 ꢀttq, J ˆ 5, 39, 265, CF2),
61.2 ꢀdt, J ˆ 5, 27, OCH2)
119.7 ꢀdq, J ˆ 13, 283, CF3),
70 ꢀdsep, J ˆ 4, 37, OCH)
81.8 and 81.7 ꢀdd, J ˆ 7, 173,
FCH2), 73.3 ꢀdt, J ˆ 6, 20, CO)
À74.8 ꢀ6F, m, CF3)
7.0
7.2
1458, 1421, 1288 ꢀP=O), 1174,
1109, 995, 962, 839
C4H5F6O3P Mw 246
C6H5F10O3P Mw 346
7.05 ꢀ1H, d, J ˆ 758, P±H),
4.52 ꢀ4H, complex m, OCH2)
À123.6 ꢀ4F, t, J ˆ 13, CF2),
À82.7 ꢀ6F, m, CF3)
1460, 1408, 1377, 1356, 1277
ꢀP=O), 1203, 1165, 1130, 1038,
985, 935, 870
6a
7.06 ꢀ1H, d, J ˆ 759, P±H),
À126.9 ꢀ4F, m, CF2), À121 ꢀ4F, m,
CF2), À80.4 ꢀ6F, t, J ˆ 10, CF3)
7.3
1356, 1230 ꢀP=O), 1186,
1126, 968, 926, 870
C8H5F14O3P Mw 446
4.58 ꢀ4H, complex m, OCH2)
7a
7.29 ꢀ1H, d, J ˆ 795, P±H),
5.22 ꢀ2H, m, OCH)
À74.2 ꢀ12F, br d, J ˆ 38, CF3)
7.9
6.7
1381, 1300, 1267, 1232 ꢀP=O),
1131, 1111, 1065, 984, 904, 880
1462, 1412, 1365, 1261 ꢀP=O),
1105, 1043, 964, 903, 795
C6H3F12O3P Mw 382
C6H11F4O3P Mw 238
8ab
7.07 ꢀ1H, d, J ˆ 738, P±H),
4.91 ꢀ2H, m, OCH), 4.69 and
4.59 ꢀ8H, complex m, FCH2)
7.1 ꢀ1H, d, J ˆ 729, P±H),
1.71 ꢀ12H, d, J ˆ 5, CH3)
À30.6 ꢀ2F, dt, J ˆ 20, 48, FCH2),
À30.3 ꢀ2F, dt, J ˆ 20, 48, FCH2)
9a
124.6 ꢀdq, J ˆ 10, 283, CF3),
82 ꢀdq, J ˆ 7, 32, CO),
22.4 ꢀd, J ˆ 36, CH3)
À83.6 ꢀ6F, m, CF3)
À77.5 ꢀ12F, m, CF3)
À64.6 ꢀ6F, m, CF3)
À3.6
À4.1
6.3
1475, 1400, 1381, 1335, 1279,
1234 ꢀP=O), 1169, 1132, 1036,
978, 931
C8H13F6O3P Mw 302
C8H7F12O3P Mw 410
C6H9F6O3P Mw 274
10a
11a
7.24 ꢀ1H, d, J ˆ 780, P±H),
119.9 ꢀdq, J ˆ 13, 285, CF3),
81.7 ꢀdsep, J ˆ 5, 38, CO),
15.5 ꢀm, CH3)
1464, 1400, 1309, 1223 ꢀP=O),
1132, 1090, 976, 879, 831
1.98 ꢀ6H, m, CH3)
6.88 ꢀ1H, d, J ˆ 716, P±H),
4.33 ꢀ4H, dt, J ˆ 6.4 and
6.2, 6, CH2), 2.55
125 ꢀq, J ˆ 277, CF3),
58.6 ꢀdq, J ˆ 4, 6, OCH2),
34.9 ꢀq, J ˆ 6, 30, CH2)
1477, 1437, 1394, 1354, 1300,
1255 ꢀP=O), 1159, 1136, 1078,
985, 928
ꢀ4H, qt, J ˆ 6, 4, CH2)
6.5 ꢀ1H, d, J ˆ 719, P±H),
3.9 ꢀ4H, m, OCH2),
12a
13a
120±111 ꢀcomplex m, C4F9),
58.8 ꢀd, J ˆ 22, OCH2),
32.9 ꢀm, CH2)
À125, À124, À113.7, À81
6.3
6.4
1358, 1221 ꢀP=O), 1132, 1078,
1003, 876, 833
C12H9F18O3P Mw 574
ꢀ18F, complex m, C4F9)
2.0 ꢀ4H, m, CH2)
6.9 ꢀ1H, d, J ˆ 714, P±H),
4.39 ꢀ4H, dd, J ˆ 6, 13, OCH2),
2.55 ꢀ4H, m, CH2)
121±107 ꢀcomplex m,
C6F13), 58.2 ꢀd, J ˆ 5,
OCH2), 32.5 ꢀm, CH2)
À126, À124, À123, À122, À113,
1484, 1433, 1367, 1317, 1240
C16H9F26O3P Mw 774
À81 ꢀ26F, all complex m, C6F13
)
ꢀP=O), 1205, 1146, 1084, 979, 810
a All mass spectra ꢀchemical ionisation) displayed a prominent molecular ion M ‡ 1 peak.
b The carbon, hydrogen and fluorine atoms of the side-chains are prochiral, hence, complex second-order splitting patterns.

C.M. Timperley et al. / Journal of Fluorine Chemistry 113 *2002) 65±78
69
2.3. Synthesis of other bis*2,2,2-trihaloethyl) phosphites
Tri¯uoroethanol combines with the intermediate from
tert-butanolysis of phosphorus trichloride, but other triha-
loethanols do not. Trichloroethanol furnished an undistill-
able mixture of mono and bis substitution products
ꢀpercentages determined by GC±MS analysis).
Tribromoethanol did not react under the same conditions,
or even after heating under re¯ux for a further 8 h in the
presence of added 4-dimethylaminopyridine, often a useful
phosphorylation catalyst [4]. The order of reactivity
CF3CH2OH > CCl3CH2OH > CBr3CH2OH is explained
by differences in the electronegativity and size of the
trihaloethoxy groups.
2.4. Synthesis of bis*fluoroalkyl) phosphorochloridates
Methods for the synthesis of dialkyl phosphorochloridates
are not always useful for the synthesis of bisꢀ¯uoroalkyl)
phosphorochloridates. For example, chlorination of trialkyl
phosphites proceeds through a phosphorane that collapses to
give the dialkyl phosphorochloridate in good yield [17].
Fig. 2. Literature routes to bisꢀfluoroalkyl) phosphorochloridates.
Phosphoranes derived from trisꢀ¯uoroalkyl) phosphites
are more stable than their hydrologues: the greater the size
and electronegativity of the ¯uoroalkyl groups, the higher
the phosphorane stability, and this can prevent the second
stage of the reaction. In contrast to triisopropyl phosphite
which gives the chloridate [ꢀCH3)2CHO]2PꢀO)Cl in good
yield, trisꢀhexa¯uoroisopropyl) phosphite gives the stable
phosphorane [ꢀCF3)2CHO]3PCl2 in 83% yield; it does not
decompose even on distillation [27]. However, tri-n-propyl
phosphite and trisꢀtetra¯uoropropyl) phosphite give the
chloridates ꢀCH3CH2CH2O)2PꢀO)Cl and ꢀHCF2CF2CH2O)2-
PꢀO)Cl in high yield [28].
Some routes to bisꢀ¯uoroalkyl) phosphorochloridates are
shown in Fig. 2. The ®rst involves treatment of phosphorus
oxychloride with a ¯uoroalcohol and a base, usually triethy-
lamine or pyridine, in ether ꢀroute 2A). Disadvantages,
especially for large scale work, lie in the large quantities
of base required ꢀremoval of base hydrochloride is some-
times dif®cult) and the fact that a range of substitution
products are produced even under conditions favouring
the formation of bisꢀ¯uoroalkyl) phosphorochloridates
ꢀe.g. using an excess of phosphorus oxychloride); puri®ca-
tion involves repeat fractionations which lower the yields. A
way round using an amine base is to heat phosphorus
oxychloride with a ¯uoroalcohol in the presence of a cat-
alytic amount of calcium chloride ꢀroute 2B), but this
modi®cation also gives a range of substitution products.
Although the reaction of trisꢀ¯uoroalkyl) phosphites with
chlorine is satisfactory in some cases, it is costly because of
the expensive methods needed for the synthesis of the
¯uorinated phosphite and because it results in loss of a
¯uoroalkyl group ꢀroute 2C). This dif®culty is avoided by
starting with the bisꢀ¯uoroalkyl) phosphite. The reaction of
sulphuryl chloride with dialkyl phosphites, pioneered by

70
C.M. Timperley et al. / Journal of Fluorine Chemistry 113 *2002) 65±78
Todd and co-workers [35], has been extended to bisꢀ¯uor-
oalkyl) phosphites with considerable success ꢀroute 2D).
Only one example of the reaction of chlorine with a
bisꢀ¯uoroalkyl) phosphite has been reported ꢀroute 2E).
The last two routes represent the best methods for the
synthesis of bisꢀ¯uoroalkyl) phosphorochloridates as both
reactions are clean and the by-products are gaseous.
We investigated the chlorination of bisꢀ¯uoroalkyl) phos-
phites in cold dichloromethane. Decolourisation took place
the instant chlorine entered the solution; a yellow coloura-
tion indicated the end-point. Bisꢀo,a,a-trihydroper¯uor-
oalkyl) phosphites ꢀ1a±3a) gave the chloridates 1b±3b in
excellent yield.
The tautomer ꢀRFO)2P±OH was not detected by NMR
studies in dichloromethane or chloroform, but is assumed to
be in equilibrium with the form ꢀRFO)2PꢀO)H. Only a tiny
amount of the `enol' form ꢀP±OH) is present in solutions of
dialkyl phosphites [38]: the equilibrium constant for diethyl
phosphite, e.g. is 107 in favour of the ꢀEtO)2PꢀO)H form [39]
and the ꢀEtO)2P±OH form has never been detected directly
by any spectroscopic technique. Thus, the phosphorus NMR
spectrum for this compound, like those of the bisꢀ¯uor-
oalkyl) phosphites, shows only the signal from the P±H
1
form, easily recognised by the very large H±31P coupling
constant, e.g. 691 Hz for ꢀEtO)2PꢀO)H [40] and 775 Hz for
ꢀCF3CH2O)2PꢀO)H.
Whether thebisꢀ¯uoroethyl)phosphitesꢀRFO)2PꢀO)Hcon-
tain a higher proportion of the `enol' form compared to the
corresponding dialkyl phosphites ꢀRO)2PꢀO)H remains unan-
swered. The electronegative ¯uoroalkoxy groups should sta-
bilise the P±OH form to some extent; it is known that when
two ꢀbut not one) tri¯uoromethyl groups are present on
phosphorus, as in ꢀCF3)2P±OH, electron-attraction is so pro-
nounced that the lone pair is unable to accept hydrogen from
the OH groupÐin this case, no ꢀCF3)2PꢀO)H can be detected
[41].
Chlorination of bisꢀ¯uoroalkyl) phosphites ꢀ4a±13a) gave
the chloridates 4b±13b in good yield and in a state of high
purity. Replacement of dichloromethane with other chlori-
nated solvents, such as chloroform, did not alter the yields.
2.5. Physical properties of bis*fluoroalkyl)
phosphorochloridates
Bisꢀ¯uoroalkyl) phosphorochloridates ꢀ1b±12b) are col-
ourless mobile liquids. An exception is the long-chain
compound 13b that is a white solid ꢀmp 27 8C). Whereas
bisꢀ¯uoroethyl) phosphorochloridate ꢀFCH2CH2O)2PꢀO)Cl
rapidly decomposes on standing [29], compounds 1b±13b
are stable inde®nitely when stored in the absence of moisture
in a refrigerator. Their boiling points depend on the ¯uoro-
ester groups ꢀTable 3) and follow the same trends as the
bisꢀ¯uoroalkyl) phosphites. The ¯uorologue ꢀCF3CH2O)2-
PꢀO)Cl ꢀ4b) ꢀbp 62 8C/10 mmHg) boils at a lower tempera-
ture than its hydrologue ꢀCH3CH2O)2PꢀO)Cl ꢀbp 94 8C/
10 mmHg) [42]. The chlorinated analogue ꢀCCl3CH2O)2-
PꢀO)Cl is a solid ꢀmp 48±49 8C) [43].
Spectroscopic data for bisꢀ¯uoroalkyl) phosphorochlor-
idates ꢀ1b±13b) appear in Table 4. Their phosphorus che-
mical shifts are between À7.2 and 8.9 ppm. The phosphoryl
vibration appears in the range 1309±1288 cmÀ1 in the
infrared spectra.
Un¯uorinated counterparts of bisꢀ¯uoroalkyl) phosphor-
ochloridates ꢀ1b±13b) are known [42,44±46] as are a few
halogenated analogues. As noted in Section 2.2, the presence
of ¯uorine atoms in the ester groups can impart high thermal
stability. For example, bisꢀdichloroisopropyl) phosphoro-
chloridate [ꢀClCH2)2CHO]2PꢀO)Cl decomposes readily dur-
ing distillation [24], and di-tert-butyl phosphorochloridate
[ꢀCH3)3CO]2PꢀO)Cl decomposes spontaneously at room
temperature after several hours [47]. The ¯uorologues
[ꢀFCH2)2CHO]2PꢀO)Cl and [ꢀCH3)2CF3CO]2PꢀO)Cl could
be distilled without appreciable decomposition.
Reactions of halogens with bisꢀ¯uoroalkyl) phosphites
most likely involve nucleophilic attack by the trivalent
phosphite tautomer that forms in the rate-determining step
[36,37].

C.M. Timperley et al. / Journal of Fluorine Chemistry 113 *2002) 65±78
71
Table 3
The mechanism most likely involves attack of the lone
pair of the `enol' phosphite form on the sulphur atom of
thionyl chloride.
Experimental data for bisꢀfluoroalkyl) phosphorochloridates ꢀRFO)2PꢀO)Cl
Compound
RF
Yield ꢀ%)
Boiling point
ꢀ8C/mmHg)
1b
2b
HCF2CH2
91
83
89
94
84
90
82
79
88
62
76
49
96
76/0.1
HꢀCF2)2CH2
HꢀCF2)4CH2
CF3CH2
115/0.08a
100/0.1b
62/10c
3b
4b
5b
6b
C2F5CH2
C3F7CH2
71/10d
68/2e
7b
8b
ꢀCF3)2CH
48/10
ꢀFCH2)2CH
CF3ꢀCH3)2C
ꢀCF3)2CH3C
CF3CH2CH2
C4F9CH2CH2
C6F13CH2CH2
154/0.2
80/10
9b
10b
11b
12b
13b
54/10
77/0.08f
141/6
Solid ꢀmp 27 8C)g
a Previously made in 81% yield by treatment of [HꢀCF2)2CH2O]2-
PꢀO)H with sulphuryl chloride ꢀliterature bp 101 8C/1 mmHg) [33], in 67%
yield by chlorination of [HꢀCF2)2CH2O]2PꢀO)H ꢀliterature bp 111±112 8C/
6 mmHg) [34] and in 88% yield by chlorination of [HꢀCF2)2CH2O]3P
ꢀliterature bp 60±62 8C/0.05 mmHg) [28]; the boiling points given in the
last two references do not match those we found for the pure substance.
b Previously made in 77% yield by treatment of [HꢀCF2)4CH2O]2-
PꢀO)H with sulphuryl chloride ꢀliterature bp 127 8C/1 mmHg) [33].
c Previously made in 93% yield by treatment of ꢀCF3CH2O)2PꢀO)H with
sulphuryl chloride ꢀliterature bp 67±70 8C/14 mmHg) [32] and in yields
between 40 and 65% by trifluoroethanolysis of phosphorus oxychloride in
the presence of triethylamine or pyridine ꢀliterature bp 45 8C/5 mmHg [19],
67±68 8C/14 mmHg [30] and 61±62 8C/10 mmHg [4]).
The unstable species ꢀRFO)2PꢀO)SOCl breaks down to
give the bisꢀ¯uoroalkyl) phosphorochloridate plus sulphur
monoxide. Evidence for the latter is provided by formation
of sulphur during distillation: sulphur monoxide readily
disproportionates to sulphur and sulphur dioxide [49].
Another possibility is disproportionation of the phosphorus
intermediate:
2 ꢀRFO† PꢀO†SOCl ÀS; ÀSO
!
2 2 ꢀRFO†2PꢀO†Cl
2
d Previously made in 45% yield by fluoroalcoholysis of phosphorus
oxychloride in the presence of triethylamine ꢀliterature bp 74±76 8C/
10 mmHg) [4].
Identical mechanistic arguments were proposed by Posh-
kus and Herweh [49] who studied the reaction of trialkyl
phosphites with thionyl chloride.
e Previously made in 50% yield by fluoroalcoholysis of phosphorus
oxychloride in the presence of calcium chloride catalyst ꢀbp 89±90 8C/
9 mmHg) [31].
2.7. Synthesis of bis*trifluoroethyl)
phosphorofluoridate
f Previously made in 48% yield by fluoroalcoholysis of phosphorus
oxychloride in the presence of calcium chloride catalyst ꢀliterature bp 110±
111 8C/9 mmHg) [31].
g Crude material was 98% pure by multinuclear NMRanalysis after
chlorination and removal of solventÐrecrystallisation was not attempted
and would have lowered the yield.
Among the ®rst dialkyl phosphoro¯uoridates, described
by Lange and von KruÈeger [50], was the diethyl derivative
ꢀCH3CH2O)2PꢀO)F ꢀbp 63 8C/12 mmHg). It was isolated in
poor yield by heating the di-silver salt of phosphoro¯uoridic
acid ꢀAgO)2PꢀO)F with two molar equivalents of ethyl
iodide. More ef®cient routes to this and related compounds
were developed during the 1940s by Saunders in the UK and
by Schrader in Germany [51]. Both research groups found
that dialkyl phosphoro¯uoridates could be prepared much
more easily, and in high yield, by alcoholysis of phosphoryl
dichloro¯uoride Cl2PꢀO)F, or by heating the corresponding
phosphorochloridates ꢀRO)2PꢀO)Cl with an alkali metal
¯uoride ꢀe.g. NaF or KF) in an inert solvent ꢀe.g. benzene
or acetonitrile).
This discovery prompted the synthesis of the ®rst dia-
lkyl phosphoro¯uoridates with ¯uoro-ester groups, all
derived formally from the parent compound ꢀCH3CH2O)2-
PꢀO)F. The work of Saunders led to ¯uoridate 14 [52,53]
and that of Schrader to ¯uoridates 15 and 16 [54]. The
most recent bisꢀ¯uoroalkyl) phosphoro¯uoridate ꢀ17),
reported by Fokin et al. [55], was isolated from a 1:1
mixture of phosphorus pentoxide and tetra¯uoropropanol
2.6. Chlorination of bis*trifluoroethyl) phosphite with
thionyl chloride
The reactions of un¯uorinated phosphites [48] and
bisꢀ¯uoroalkyl) phosphites [32,33] with sulphuryl chloride
produces the chloridates ꢀRO)2PꢀO)Cl or ꢀRFO)2PꢀO)Cl in
moderate to high yields. Analogous reactions with thionyl
chloride are known only in the case of un¯uorinated phos-
phites [49]. For this reason, we examined the reaction of
bisꢀtri¯uoroethyl) phosphite with thionyl chloride in ether.
The desired chloridate 4b was isolated in poor yield. A
yellow solid, presumed to be sulphur [49], sublimed in the
distillation apparatus.

Table 4
Spectroscopic data for bisꢀfluoroalkyl) phosphorochloridates ꢀRFO)2PꢀO)Cl ꢀNMRdata measured in CDCl
)
3
Compound 1H NMR d, J ꢀHz)
13C NMR d, J ꢀHz)
19F NMR d
31P NMR d IR n ꢀcmÀ1
)
GC±MS analysisa
1b
2b
6.01 ꢀ2H, tt, J ˆ 4, 54, CF2H),
111.8 ꢀdt, J ˆ 10, 42, CF2H),
66.3 ꢀdt, J ˆ 6, 30, OCH2)
113.1 ꢀdtt, J ˆ 10, 29, 251,
CF2), 108.9 ꢀtt, J ˆ 37, 251,
CF2H), 64.1 ꢀdt, J ˆ 5,
À126.1 ꢀ4F, dt, J ˆ 13, 53, CF2H)
4.6
4.5
1456, 1429, 1375, 1302 ꢀP=O),
1086, 962, 903, 827
C4H6ClF4O3P Mw 244
4.36 ꢀ4H, complex m, OCH2)
5.94 ꢀ2H, tt, J ˆ 6, 53, CF2H),
4.55 ꢀ4H, complex m, OCH2)
À136.6 ꢀ4F, d, J ˆ 53, CF2H),
À123.5 ꢀ4F, dt, J ˆ 3, 12, CF2)
1458, 1404, 1300 ꢀP=O), 1259,
1238, 1213, 1109, 1063, 951, 895
C6H6ClF8O3P Mw 344
30, OCH2)
3b
6.06 ꢀ4H, tt, J ˆ 6, 52, HCF2),
113 ꢀdtt, J ˆ 6, 31, 251, CF2),
107.8 ꢀtt, J ˆ 37, 249, CF2H),
110±109 ꢀm, CF2CF2),
À138 ꢀ4F, m, CF2H), À130,
4.7
1458, 1404, 1298 ꢀP=O),
1173, 1132, 1078, 1011,
989, 958, 904, 808
C10H6ClF16O3P Mw 544
4.64 ꢀ2H, m, OCH2)
À126.5 and À119.8 ꢀ12F, m, CF2)
64.2 ꢀdt, J ˆ 28, OCH2)
121.8 ꢀdq, J ˆ 11, 277, CF3),
64.7 ꢀdq, J ˆ 6, 34, OCH2)
4b
5b
4.55 and 4.51 ꢀ4H, qdd, J ˆ 3.3,
7.6, 15.3, OCH2)
À74.2 ꢀ6F, t, J ˆ 7, CF3)
4.7
4.6
1456, 1421, 1304 ꢀP=O), 1279,
1178, 1078, 964, 897, 847
1458, 1409, 1306 ꢀP=O),
1271, 1205, 1163, 1111,
1030, 957, 935, 893
C4H4ClF6O3P Mw 280
C6H4ClF10O3P Mw 380
4.61 ꢀ4H, broad m, OCH2)
117.2 ꢀm, CF3), 111.3 ꢀm, CF2), À123.5 ꢀ4F, m, CF2)
63.8 ꢀm, OCH2)
À82.8 ꢀ6F, m, CF3)
6b
4.64 ꢀ4H, complex m, OCH2)
117.5 ꢀtq, J ˆ 33, 288, CF3),
113.1 ꢀttd, J ˆ 11, 31, 258,
CF2), 108.6 ꢀtqd, J ˆ 5, 40,
264, CF2), 64.2 ꢀdt, J ˆ 5,
28, OCH2)
À126.7 ꢀ4F, m, CF2),
À120.5 ꢀ4F, m, CF2),
À80.2 ꢀ6F, t, J ˆ 10, CF3)
4.8
8.9
1356, 1302 ꢀP=O), 1232, 1186,
1132, 1078, 1014, 970, 933
C8H4ClF14O3P Mw 480
7b
5.32 ꢀ2H, dsept,
119.7 ꢀdq, J ˆ 5, 281, CF3)
À73.6 ꢀ6F, m, CF3) and
1379, 1298 ꢀP=O), 1267, 1234,
1205, 1113, 1018, 930, 904, 883
C6H2ClF12O3P Mw 416
J ˆ 3.7, 5.2, OCH)
and 119.6 ꢀdq, J ˆ 5, 283, CF3), À73.2 ꢀ6F, br d, J ˆ 38, CF3)
72.6 ꢀdsep, J ˆ 4.3, 36.6, OCH)
8bb
9b
4.95 ꢀ2H, m, OCH), 4.60 and
4.75 ꢀ8H, m complex, FCH2)
1.77 ꢀ12H, d, J ˆ 5, CH3)
81.8 and 81.7 ꢀdd, J ˆ 7, 173,
À31 ꢀ2F, dt, J ˆ 18, 46, FCH2),
4.2
1460, 1414, 1365, 1288 ꢀP=O),
1093, 1047, 1001, 904
C6H10ClF4O3P Mw 272
C8H12ClF6O3P Mw 336
FCH2), 73.3 ꢀdt, J ˆ 6, 20, CO) À31.6 ꢀ2F, dt, J ˆ 18, 48, FCH2)
124 ꢀdq, J ˆ 14, 283, CF3), 84.7 À83.6 ꢀ6F, m, CF3)
ꢀdq, J ˆ 6, 32, CO), 21.6
À7.2
1477, 1402, 1381, 1335,
1298 ꢀP=O), 1236, 1171,
1128, 1024, 931
ꢀd, J ˆ 36, CH3)
10b
11b
12b
13b
2.07 ꢀ6H, m, CH3)
121 ꢀqm, J ˆ 287, ꢁ8, CF3),
82.9 ꢀdsep, J ˆ 6, 33, CO),
14.3 ꢀm, CH3)
À98.7 ꢀ6F, q, J ˆ 8 CF3),
À98.3 ꢀ6F, q, J ˆ 8, CF3)
À7.7
2.7
1462, 1400, 1309 ꢀP=O), 1228,
1167, 1134, 1093, 1012, 879, 835
C8H6ClF12O3P Mw 444
C6H8ClF6O3P Mw 308
C12H8ClF18O3P Mw 608
C16H8ClF26O3PMw 808
4.42 ꢀ4H, m, OCH2),
2.61 ꢀ4H, m, CH2)
125 ꢀq, J ˆ 277, CF3),
62.1 ꢀm, OCH2), 34.3
À64.6 ꢀ6F, CF3)
1437, 1394, 1354, 1300 ꢀP=O),
1257, 1163, 1136, 1070, 1026, 937
ꢀdq, J ˆ 30, CH2)
4.5 ꢀ4H, m, OCH2),
2.6 ꢀ4H, m, CH2)
120±105 ꢀcomplex m, C4F9),
61.5 ꢀdt, J ˆ 5, 6, OCH2),
31.7 ꢀdt, J ˆ 8, 21, CH2)
121 to 108 ꢀcomplex m, C6F13),
61.9 ꢀd, J ˆ 6.2, OCH2),
31.9 ꢀdt, 8.3, 20.7, CH2)
À125.7, À124.1, À113.4,
3.0
1365, 1302 ꢀP=O), 1223, 1134,
1051, 1014, 877, 835
À80.7 ꢀ18F, complex m, C4F9)
4.41 ꢀ4H, m, OCH2),
2.52 ꢀ4H, m, CH2)
À125.8, À123.1, À122.4,
À121, À113, À80.9 ꢀ26F,
2.3
1483, 1430, 1343, 1299 ꢀP=O),
1240, 1205, 1146, 1078, 843, 810
complex m, C6F13
)
a All mass spectra ꢀchemical ionisation) displayed a prominent molecular ion M ‡ 1 peak.
b The carbon, hydrogen and fluorine atoms of the side-chains are prochiral, hence, complex second-order splitting patterns.

C.M. Timperley et al. / Journal of Fluorine Chemistry 113 *2002) 65±78
73
that had been heated at 170±180 8C for 2±3 h.
Di¯uoridate 19 gave a characteristic triplet in its phos-
phorus NMRspectrum ꢀ dP À8.3, JPF 1000 Hz). It is only the
second ¯uoroalkyl phosphorodi¯uoridate to have been
identi®ed; the ®rst was HꢀCF2)2CH2OPꢀO)F2 by Fokin
et al. [55]. The identity of phosphate 20 was con®rmed
by comparison of its spectroscopic data with that of a pure
specimen prepared previously in our laboratories [6]. How
are compounds 19 and 20 produced? The best explanation is
that some ¯uoridate 18 reacts with ¯uoride ion, with loss of
a tri¯uoroethoxy group, thus giving di¯uoridate 19. The
liberated tri¯uoroethanol presumably reacts with ¯uoridate
18 to give the ¯uoroalkyl phosphate 20.
We sought to prepare bisꢀtri¯uoroethyl) phosphoro¯uor-
idate ꢀCF3CH2O)2PꢀO)F, but heating chloridate 4b with NaF
or KF in dichloromethane did not result in ¯uorination. As
¯uoro-ester groups are stable to acids, an acid catalyst could
be used. Conversion of chloridate 4b to ¯uoridate 18 was
effected using potassium ¯uoride and a catalytic amount of
tri¯uoroacetic acid. Bisꢀtri¯uoroethyl) phosphoro¯uoridate
ꢀ18) is a colourless mobile liquid ꢀbp 61 8C/40 mmHg).
2.8. Synthesis of bis*trifluoroethyl) phosphorobromidate
Few dialkyl phosphorobromidates are known. Reasons for
this are two-fold. First, dialkyl phosphorochloridates are
easily accessible and combine with nucleophiles under mild
conditions; the corresponding bromidates furnish the same
products, but the bromidates are more dif®cult to obtain
pure. Second, chlorination of dialkyl phosphites gives the
chloridate plus hydrogen chloride. The reaction with bro-
mine liberates hydrogen bromide, a better dealkylating agent
than hydrogen chloride. Thus, bromination of phosphites is
often accompanied by side-reactions, the produced HBr
reacting with the phosphorobromidate to give the bromo
acids HOꢀRO)PꢀO)Br and/or ꢀHO)2PꢀO)Br with loss of alkyl
bromide [56]. Dealkylation occurs by an SN2 process where
the bromide ion, a soft base, attacks the a-carbon of the ester
group, a soft acid ꢀfor an account of the concept of hard and
soft acids and bases applied to multi-centre reactions, refer
to [57]).
The mechanism of catalysis presumably involves displa-
cement of HF from potassium ¯uoride by tri¯uoroacetic
acid. The HF then converts the chloridate into ¯uoridate,
with released HCl reacting with potassium ¯uoride to lib-
erate more hydrogen ¯uoride.
Another reagent for introducing the P±F bond is triethy-
lamine hydro¯uoride ꢀmade by dilution of commercial
triethylamine trihydro¯uoride with triethylamine). It converts
amidochloridates to amido¯uoridates, e.g. Me2NPꢀO)Cl2 to
Me2NPꢀO)F2 in 42% yield [4]. Its potential for ¯uorination of
other phosphorus halides is presently unknown, but requires
exploration. We examined its effect on bisꢀtri¯uoroethyl)
phosphorochloridate ꢀ4b). The three products that formed
could not be separated by fractional distillation: bisꢀtri¯uor-
oethyl) phosphoro¯uoridate ꢀ18), tri¯uoroethyl phosphoro-
di¯uoridate ꢀ19) and trisꢀtri¯uoroethyl) phosphate ꢀ20).
The ®rst method to suppress dealkylation of the product is
to use a dialkyl phosphite with hindered ester groups:
Gerrard et al. [58] isolated ꢀtert-BuCH2O)2PꢀO)Br from
treatment of the dialkyl phosphite with bromine in the
absence of solvent. The second method is to use a dialkyl
phosphite with electronegative ester groups. Their lower
basicity prevents protonation, and renders the a-carbon atom
a harder acid, and hence, the ester groups are less susceptible
to attack by the soft halide ion. Fluoroester groups resist
dealkylation more than ester groups: heavily ¯uorinated
ester groups are less vulnerable than lightly ¯uorinated ones.
We recognised the potential of bisꢀ¯uoroalkyl) phosphites as
precursors to a range of hitherto inaccessible ¯uoroalkyl
phosphorobromidates, many of which are expected to have
unstable hydrologues. Treatment of bisꢀtri¯uoroethyl) phos-
phite ꢀ4a) with bromine in benzene or dichloromethane gave

Table 5
Spectroscopic data for bisꢀtrifluoroethyl) phosphorohalidates ꢀCF3CH2O)2PꢀO)X ꢀNMRdata measured in CDCl
)
3
Compound
X
F
1H NMR d, J ꢀHz)
13C NMR d, J ꢀHz)
19F NMR d
31P NMR d
IR n ꢀcmÀ1
)
GC±MS analysis
18
4.53 ꢀ4H, dt, J ˆ 10, 8, OCH2) 123 ꢀdq, J ˆ 9, 278, CF3),
63.7 ꢀdq, J ˆ 3, 39, OCH2)
À78.4 ꢀ1F, d, JP±F ˆ 1002, À12 ꢀd, JP±F ˆ 1002) 1458, 1425, 1333, 1306 ꢀP=O), C4H4F7O3P 265 ꢀM ‡ 1, 95)
P±F), À74.7 ꢀ6F, br s, CF3)
121.8 ꢀdq, J ˆ 11, 277, CF3), À74.2 ꢀ6F, t, J ˆ 7, CF3)
64.7 ꢀdq, J ˆ 6, 34, OCH2)
1282, 1182, 1086, 966, 922, 843 245 ꢀM À F, 48)
4ba
21
Cl 4.55 and 4.51 ꢀ4H, qdd,
4.7
1456, 1421, 1304 ꢀP=O), 1279, C4H4ClF6O3P 281 ꢀM ‡ 1, 100)
J ˆ 3, 8, 15, OCH2)
1178, 1078, 964, 897, 847
261 ꢀM À F, 12) 245 ꢀM À Cl, 8)
‡
Br 4.52 ꢀ4H, m, J ˆ 2, 8, OCH2) 121.7 ꢀdq, J ˆ 11, 278, CF3), À73.9 ꢀ6F, t, J ˆ 7, CF3)
64.6 ꢀdq, J ˆ 6, 34, OCH2)
À8.6
1454, 1421, 1302 ꢀP=O), 1275, C4H4BrF6O3P 325 ꢀM , 100) 305
1178, 1070, 964, 910, 849, 737 ꢀM À F, 32) 245 ꢀM À Br, 28)
1454, 1421, 1296 ꢀP=O), 1174, C4H4F6IO3P 373 ꢀM ‡ 1, 100)
22b
I
4.45 ꢀ4H, m, OCH2)
121.4 ꢀdq, J ˆ 13, 278, CF3), À74.1 ꢀ6F, t, J ˆ 7, CF3)
À47.7
69.4 ꢀdq, J ˆ 5, 37, OCH2)
1070, 962, 883, 849
353 ꢀM À F, 18) 245 ꢀM À I, 36)
a High resolution mass spectral data for this chloridate appears elsewhere [4].
b High resolution mass spectral data for this iodidate appears elsewhere [10].

C.M. Timperley et al. / Journal of Fluorine Chemistry 113 *2002) 65±78
75
the phosphorobromidate 21 as a colourless mobile liquid ꢀbp
38 8C/0.8 mmHg).
Compound 22 is the ®rst of two dialkyl phosphoroiodi-
dates ever to have been isolated and characterised ꢀsee [10]
for further details). Its discovery, which lags behind the ®rst
isolation of a dialkyl phosphorochloridate by over 130 years,
opens up new frontiers in organic phosphorus and iodine
chemistry. The method of performing the reaction is
described in the note referred to and need not be repeated
in Section 4.
Bromidate 21 is apparently formed when the phosphorane
ꢀCF3CH2O)3PBr2, from bromination of trisꢀtri¯uoroethyl)
phosphite, decomposes at temperatures above À40 8C [59];
however, until now it has not been isolated or characterised
properly. When pure, it is stable at room temperature, but
best stored in a refrigerator, where it keeps for long periods
of time without degradation. This contrasts with the
un¯uorinated analogue ꢀCH3CH2O)2PꢀO)Br ꢀbp 75 8C/
1.5 mmHg) which decomposes readily, giving ethyl bromide
and a polymeric, bromine-free residue after 72 h at 17 8C or
20 min at 100 8C [60]. Interestingly, the trichloroethyl ana-
logue ꢀCCl3CH2O)2PꢀO)Br, prepared by heating the phos-
phorane ꢀCCl3CH2O)3PBr2 at 130 8C, is a solid compound
ꢀmp 51±53 8C) [43].
Compound 21 is only the third bisꢀ¯uoroalkyl) phosphor-
obromidate to have been characterised. The other two
compounds [HꢀCF2)2CH2O]2PꢀO)Br and [HꢀCF2)4CH2O]2-
PꢀO)Br, were isolated in 74 and 76% yield from reaction of
the trisꢀ¯uoroalkyl) phosphites with bromine in carbon
tetrachloride [28]. Bisꢀa,a,o-trihydroper¯uorobutyl) phos-
phorobromidate [HꢀCF2)2CH2O]2PꢀO)Br was also isolated
after treating the corresponding bisꢀ¯uoroalkyl) phosphite
with bromine in dichloromethane at À208C ꢀyield not
quoted) [61] and by treatment of the trisꢀ¯uoroalkyl)
phosphite with cyanogen bromide ꢀspectroscopic support
not provided) [62]. The homologue [HꢀCF2)4CH2O]2-
PꢀO)Br also formed in 38% yield on oxidation of the
dibromidate HꢀCF2)4CH2OPBr2 by dimethyl sulfoxide;
however, it could not be separated from the two other
products: HꢀCF2)4CH2OPꢀO)Br2 and [HꢀCF2)4CH2O]3-
P=O [63].
2.10. Physical properties of bis*2,2,2-trifluoroethyl)
phosphorohalidates
The bisꢀtri¯uoroethyl) phosphorohalidates are liquids.
Their spectroscopic data appear in Table 5. The phosphorus
chemical shifts, measured in deuteriochloroform, are char-
acteristic of each class of compound, but as with all phos-
phorus NMRdata, dif®cult to rationalise theoretically. The
greater shielding observed for ꢀCF3CH2O)2PꢀO)F ꢀdP
À12 ppm) compared to the corresponding chloridate
ꢀCF3CH2O)2PꢀO)Cl ꢀdP ‡4.7 ppm) may be attributed to
the former having increased positive charge on phosphorus.
This in turn causes increased back-bonding from the phos-
phoryl oxygen. Literature phosphorus shifts for diethyl
phosphorohalidates ꢀCH3CH2O)2PꢀO)Br and ꢀCH3CH2O)2-
PꢀO)I in chloroethane are À9.7 and À41 ppm, respectively
[65]. The corresponding values for bisꢀtri¯uoroethyl) phos-
phorohalidates in deuteriochloroform are À8.6 and
À47.7 ppm. The strong shielding observed for the phos-
phoroiodidate probably results from expansion of the P±O
bond angles due to the large size of the iodine atom.
The frequency of the phosphoryl vibration ꢀnP=O) rises as
the electronegativity of the substituents on phosphorus
increases. For the bisꢀtri¯uoroethyl) phosphorohalidates,
nP=O decreases as expected: P±F ꢀ1306 cmÀ1† > P±Cl
ꢀ1304 cmÀ1† > P±Br ꢀ1302 cmÀ1† > P±I ꢀ1296 cmÀ1).
The literature value for diethyl phosphoroiodidate is
1270 cmÀ1 [66], considerably lower than that for bisꢀtri-
¯uoroethyl) phosphoroiodidate. The chemical ionisation
mass spectra of bisꢀtri¯uoroethyl) phosphorohalidates com-
prised a main M ‡ 1 peak of high intensity and M À F and
M À halogen peaks of much lower intensity.
2.9. Synthesis of bis*trifluoroethyl) phosphoroiodidate
No dialkyl phosphoroiodidates of structure ꢀRO)2PꢀO)I
have been isolated out of solution. Treatment of triethyl
phosphite ꢀEtO)3P with iodine in ether, or chloroethane,
gives diethyl phosphoroiodidate ꢀEtO)2PꢀO)I which is
thermally unstable and decomposes during work-up
[64±66]. Diethyl phosphite ꢀEtO)2PꢀO)H, initially stated
to remain unchanged by the action of iodine [64], was
later said to give a mixture of dealkylation products due to
ester cleavage by liberated hydrogen iodide [56]. In con-
trast, we found exposure of bisꢀtri¯uoroethyl) phosphite
ꢀ4a) to a solution of iodine in toluene, with argon blowing
through the mixture, gave phosphoroiodidate 22 which
survived puri®cation by vacuum distillation ꢀbp 40 8C/
0.02 mmHg).
3. Conclusion
We have described facile routes to bisꢀ¯uoroalkyl)
phosphites and bisꢀ¯uoroalkyl) phosphorochloridates that
have enabled the synthesis of pure materials. The methods
in Section 4 were reproduced successfully by several
chemists in our laboratories and we intend to submit some

76
C.M. Timperley et al. / Journal of Fluorine Chemistry 113 *2002) 65±78
for publication in ``Organic Syntheses''. Their discovery
will have a marked effect on the course of ¯uoroalkyl
phosphoryl chemistry as it is now possible to prepare a
range of bisꢀ¯uoroalkyl) phosphorohalidates from readily
accessible starting materials. By the reactions of amines,
alcohols and thiols on the bisꢀ¯uoroalkyl) phosphorochlor-
idates in the presence of triethylamine, the corresponding
amidates ꢀRFO)2PꢀO)NR2, phosphates ꢀRFO)2PꢀO)ORand
thiolates ꢀRFO)2PꢀO)SRare produced, and we hope shortly
to publish details of their preparation and general proper-
ties.
Finally, the use of the new bisꢀ¯uoroalkyl) phosphites
and phosphorohalidates as reagents for the synthesis of
polynucleotides by the phosphotriester approach is an
area that merits investigation. The use of P±OCH2CCl3
species as protected phosphoric or phosphonic acids in
nucleotide synthesis is recognised [67±72]. However, the
application of P±ORF species to the preparation of nucleo-
tides is in its infancy; only two references could be found
and these describe ꢀCF3CH2O)2PꢀO)H as the phosphoryla-
tion reagent [15,73]. The new bisꢀ¯uoroalkyl) phosphites
could also be used, in principle, to obtain phosphonic-
based oligonucleotides: the Michaelis±Becker reaction
of sodium bisꢀtri¯uoroethyl) phosphite ꢀCF3CH2O)2P±
ONa with a-haloesters XCHRCO2R0, e.g. gave the corre-
sponding phosphonates ꢀCF3CH2O)2PꢀO)CHRCO2R0
albeit in low yield [74]. The synthesis and properties of
oligonucleotides containing ¯uoroalkoxy-substituted phos-
phoryl and phosphonyl units are awaited with much
interest.
4.1. General procedure for bis*fluoroalkyl) phosphites
*1a±13a)
A solution of anhydrous tert-butanol ꢀ1 mol) in dichlor-
omethane ꢀ100 ml) was added dropwise over a period of
45 min to a stirred solution of phosphorus trichloride ꢀ1 mol)
in dichloromethane ꢀ200 ml) cooled at 0±5 8C. The mixture
was stirred at this temperature for a further hour. The
¯uoroalcohol ꢀ2 mol)3 in dichloromethane ꢀ100 ml) was
added dropwise over a period of 30 min to the cooled
solution. The mixture was left at room temperature for
12 h. It was heated under re¯ux for 3 h to drive out any
dissolved hydrogen chloride. The solvent was removed.
Distillation of the residue under reduced pressure gave a
forerun of unreacted alcohol and a main fraction of the
bisꢀ¯uoroalkyl) phosphite ꢀ1a±13a) as a colourless liquid.
Experimental and spectroscopic data appear in Tables 1 and
2.
4.2. General procedure for bis*fluoroalkyl)
phosphorochloridates *1b±13b)
Chlorine gas was bubbled into a solution of bisꢀ¯uoro-
alkyl) phosphite ꢀ0.2 mol) in dichloromethane or chloroform
ꢀ50 ml) until a yellow colour persisted in the reaction
mixture. The solvent was removed. Distillation of the resi-
due gave the bisꢀ¯uoroalkyl) phosphorochloridate ꢀ1b±12b)
as a colourless liquid. Bisꢀ1H,1H,2H,2H-per¯uoro-1-octyl)
phosphite ꢀ13b) was not distilled; removal of solvent gave
pure material as a white solid. Experimental and spectro-
scopic data appear in Tables 3 and 4.
4. Experimental details
4.3. Reaction of bis*2,2,2-trifluoroethyl) phosphite with
thionyl chloride
All reagents were of commercial quality: ¯uoroalcohols
were obtained from Apollo Scienti®c Ltd. ꢀUK). Anhydrous
solvents were used for reactions. NMRspectra were
obtained on a JEOL Lambda 500 instrument ꢀoperating at
A solution of thionyl chloride ꢀ11.8 g, 0.1 mol) in ether
ꢀ50 ml)wasaddeddropwisetoasolutionofbisꢀ2,2,2-tri¯uoro-
ethyl) phosphite ꢀ24.6 g, 0.1 mol) in ether ꢀ50 ml) at room
temperature.Thereactionwasmildlyexothermic.Analysisby
GC±MSshowedthattheexpectedproduct,bisꢀ2,2,2-tri¯uoro-
ethyl) phosphorochloridate, predominated. The solvent was
removed and the residue fractionated under reduced pressure
to give chloridate 4b as a colourless liquid ꢀ6.5 g, 23%) at bp
61±62 8C/10 mmHg. A cloudy brown residue remained in the
distillation ¯ask and a yellow sublimate, presumably sulphur,
adhered to the fractionating column.
1
500 MHz for H, 125 MHz for 13C, 470 MHz for 19F, and
202 MHz for 31P spectra) or a JEOL Lambda 300 instrument
ꢀoperating at 300 MHz for 1H, 75 MHz for 13C, 282 MHz for
19F, and 121.5 MHz for 31P spectra) as solutions in CDCl3,
with internal reference SiMe4 for 1H and 13C, external
CFCl3 for 19F and external ꢀMeO)3P ꢀd 140 ppm) for 31P
spectra. Data are recorded as follows: chemical shifts in
ppm from reference on the d scale, integration, multiplicity
ꢀs: singlet, d: doublet, t: triplet, q: quartet, m: multiplet
and sep: septet; br: broad), coupling constant ꢀJ, Hz)
and assignment. IRspectra were recorded as liquid ®lms
on a Nicolet SP210 instrument using Omnic software.
Reaction mixtures were monitored by GC±MS using a
Finnigan MAT GCQ instrument with chemical ionisation
ꢀCI) using methane as reagent gas. Molecular weights of
pure products were con®rmed with methane positive CI
data. They gave satisfactory microanalyses: C Æ 0:13,
H Æ 0:11, O Æ 0:12.
4.4. Synthesis of bis*2,2,2-trifluoroethyl)
phosphorofluoridate *18)
Finely-dividedKFꢀ1.7 g,28.7 mmol)wasaddedtoastirred
solution of bisꢀ2,2,2-tri¯uoroethyl) phosphorochloridate
3 1H,1H,2H,2H-perfluoro-1-octanol is insoluble in dichloromethane: the
two-phase mixture was added and became homogeneous as the phosphite
formed.

C.M. Timperley et al. / Journal of Fluorine Chemistry 113 *2002) 65±78
77
G.N. Molchanova, M.A. Kurykin, P.V. Petrovskii, T.M. Shcherbina,
A.P. Laretina, Russ. J. Gen. Chem. 64 ꢀ1994).
ꢀ4 g, 14.4 mmol) in dichloromethane ꢀ40 ml). The resultant
suspension was heated under re¯ux for 2 h, then assayed by
GC±MS analysis; only a trace of product was present. Tri-
¯uoroacetic acid ꢀ0.15 ml, 2 mmol) was added by syringe and
themixtureheatedunderre¯uxforafurther2 h.Aheavywhite
precipitate of KClformed. Analysisof the reactionmixture by
GC±MS showed excellent conversion to the desired product.
The solids were removed by ®ltration and the ®ltrate con-
centrated. Fractionation of the residue under reduced pressure
gave the title compound as a volatile colourless liquid ꢀ3.2 g,
84%) at bp 61 8C/40 mmHg.
[3] C.M. Timperley, I.J. Morton, M.J. Waters, J.L. Yarwood, J. Fluorine
Chem. 96 ꢀ1999) 95.
[4] C.M. Timperley, M. Bird, J.F. Broderick, I. Holden, I.J. Morton, M.J.
Waters, J. Fluorine Chem. 104 ꢀ2000) 215.
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J. Fluorine Chem. 106 ꢀ2000) 43.
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Chem. 106 ꢀ2000) 153.
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ꢀ2001) 155.
[8] C.M. Timperley, M.J. Waters, J. Fluorine Chem. 109 ꢀ2001) 103.
[9] J. Riches, K. Grant, L. Knutsen, Laboratory testing of some
phosphorus-containing compounds as fire suppressants, in: Proceed-
ings of the Halon Options Technical Working Conference, Albu-
querque, USA, 27±29 April 1999, p. 444.
4.5. Reaction of bis*2,2,2-trifluoroethyl)
phosphorochloridate with triethylamine hydrofluoride
[10] C.M. Timperley, M. Waters, Chem. Commun. 9 ꢀ2001) 797.
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I.G.E. Wilding, S.J. Woodcock, J. Chem. Soc. ꢀ1949) 2921.
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Pasevina, O.V. Verenikin, Izv. Akad. Nauk. SSSR, Ser. Khim. 1
ꢀ1979) 152 ꢀEngl. Transl.).
A solution of triethylamine ꢀ1.34 ml, 9.6 mmol) and
triethylamine trishydro¯uoride ꢀ0.78 ml, 4.8 mmol) in
dichloromethane ꢀ20 ml) was added dropwise to a stirred
solution of bisꢀ2,2,2-tri¯uoroethyl) phosphorochloridate
ꢀ4.03 g, 14.4 mmol) in dichloromethane ꢀ30 ml). An
exothermic reaction ensued. The mixture was left for
12 h. Colourless needles of triethylamine hydrochloride
had formed. The mixture was ®ltered and the ®ltrate con-
centrated to an oily white residue. Addition of ether ꢀ10 ml)
and passage of the resultant suspension through a short
plug of silica gave a clear solution. Removal of solvent
and bulb-to-bulb distillation yielded a mixture comprising
bisꢀtri¯uoroethyl) phosphoro¯uoridate ꢀ18) ꢀ84%), tri¯uoro-
ethyl phosphorodi¯uoridate ꢀ19) ꢀ14%) and trisꢀtri¯uoro-
ethyl) phosphate ꢀ20) ꢀ2%); percentages of components
were determined by phosphorus NMRanalysis.
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ꢀ1985) 1321 ꢀEngl. Transl.).
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4.6. Bis*2,2,2-trifluoroethyl) phosphorobromidate *21)
A solution of bromine ꢀ3.2 g, 0.02 mol) in dichloro-
methane ꢀ20 ml) was added dropwise to a solution of
bisꢀ2,2,2-tri¯uoroethyl) phosphite ꢀ4.9 g, 0.02 mol) in
dichloromethane ꢀ30 ml) at 0±5 8C with stirring. After
addition, the solution was warmed to room temperature
and left for 14 h; the yellow colour of the bromine had
faded. The dichloromethane was removed. Fractionation of
the residue under reduced pressure gave the title compound
as a colourless liquid ꢀ3.3 g, 51%) at bp 38 8C/0.8 mmHg.
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Acknowledgements
[32] R.A. Bowman, J.R. Stock, J.A. Jackson, Org. Prep. Proc. Int. 31
ꢀ1999) 230.
We are indebted to Dr. John M. Harrison for suggesting
tri¯uoroacetic acid as a catalyst for ¯uorination of bisꢀtri-
¯uoroethyl) phosphorochloridate. We also thank the Min-
istry of Defence, UK for funding the work.
[33] V.A. Chauzov, Yu.N. Studnev, L.I. Ragulin, A.A. Ustinov, A.V.
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