Fluorinated phosphorus compounds: Part 3. the synthesis of symmetrical and unsymmetrical fluoroalkyl phosphates

Article abstract of DOI:10.1016/S0022-1139(00)00327-4

Treatment of phosphorus pentachloride with four molar equivalents of fluoroalcohol gave symmetrical phosphates (R_FO)₃P=O in isolated yields between 10-92% [R_F=CF₃CH₂, C₂F₅CH₂, HCF₂CF₂CH₂, C₃F₇CH₂, (FCH₂)₂CH, (CF₃)₂CH, C₂F₅(CH₃)CH]. The reaction proceeded best for fluoroalcohols having many fluorine atoms. 2,2-Difluoroethanol HCF₂CH₂OH and 1,3-difluoroisopropanol (FCH₂)₂CHOH did not react cleanly and gave product mixtures. Hexafluoroisopropanol produced a 3:7 mixture of symmetrical phosphate [(CF₃)₂CHO]₃P=O and chlorophosphorane [(CF₃)₂CHO]₄PCl. The latter reacted readily with water and alcohols. Heating the chloridates CF₃CH₂OP(O)Cl₂, (CF₃CH₂O)₂P(O)Cl and (C₂F₅CH₂O)₂P(O)Cl with various fluoroalcohols in the presence of calcium chloride catalyst gave unsymmetrical phosphates in isolated yields between 46-83%. The mixed phosphate (CF₃CH₂O)₂P(O)OCH₂C ₂F₅ did not react with butanol or propylamine in dichloromethane at room temperature.

Full text of DOI:10.1016/S0022-1139(00)00327-4

Journal of Fluorine Chemistry 106 (2000) 153±161
Fluorinated phosphorus compounds
Part 3. The synthesis of symmetrical and unsymmetrical
¯uoroalkyl phosphates
Christopher M. Timperley*, Ian Holden, Ian J. Morton, Matthew J. Waters
Chemical and Biological Defence Sector, Defence Evaluation and Research Agency, Porton Down, Salisbury, Wiltshire SP4 0JQ, UK
Received 19 June 2000; accepted 9 July 2000
Abstract
Treatment of phosphorus pentachloride with four molar equivalents of ¯uoroalcohol gave symmetrical phosphates (RFO)3PˆO in
isolated yields between 10±92% [RFˆCF3CH2, C2F5CH2, HCF2CF2CH2, C3F7CH2, (FCH2)2CH, (CF3)2CH, C2F5(CH3)CH]. The reaction
proceeded best for ¯uoroalcohols having many ¯uorine atoms. 2,2-Di¯uoroethanol HCF2CH2OH and 1,3-di¯uoroisopropanol
(FCH2)2CHOH did not react cleanly and gave product mixtures. Hexa¯uoroisopropanol produced a 3:7 mixture of symmetrical phosphate
[(CF3)2CHO]3PˆO and chlorophosphorane [(CF3)2CHO]4PCl. The latter reacted readily with water and alcohols. Heating the chloridates
CF3CH2OP(O)Cl2, (CF3CH2O)2P(O)Cl and (C2F5CH2O)2P(O)Cl with various ¯uoroalcohols in the presence of calcium chloride catalyst
gave unsymmetrical phosphates in isolated yields between 46±83%. The mixed phosphate (CF3CH2O)2P(O)OCH2C2F5 did not react with
butanol or propylamine in dichloromethane at room temperature. # 2000 Elsevier Science S.A. All rights reserved.
Keywords: Bis(¯uoroalkyl)phosphorochloridate; Bis(¯uoroalkyl)¯uoroalkyl phosphate; Fluorinated phosphate; Tetra(hexa¯uoroisopropoxy)chloropho-
sphorane; Tris(¯uoroalkyl)phosphate
1. Introduction
The lowest members of the symmetrical ¯uoroalkyl
phosphate family were ®rst made in the ®rst half of the
last century by two master ¯uorine chemists: tris(2-¯uoro-
ethyl) phosphate 1 by Knunyants et al. [1] and tris(2,2-
di¯uoroethyl) phosphate 2 by Swarts [2].1 The phosphates
were prepared by the ¯uoroalcoholysis of phosphorus oxy-
chloride (route A) or phosphorus pentabromide (route B).
The ®rst reaction requires a base and an inert solvent,
whereas the second is conducted without solvent. Phosphate
2 has also been made by oxidation of tris(2,2-di¯uoroethyl)-
phosphite (HCF2CH2O)3P with oxygen in the presence of
chloral [3].
Modi®cation of routes A and B has provided other
symmetrical ¯uoroalkyl phosphates, including the third
ethyl analogue, tris(2,2,2-tri¯uoroethyl) phosphate (CF3-
CH2O)3PˆO
[4±7].
Other
homologues
include
(C2F5CH2O)3PˆO [6,7], (C3F7CH2O)3PˆO [5±10] and
[(CF3)2CHO]3PˆO [11]. Fluoroalkyl phosphates with more
remote ¯uorine atoms have received little attention,
although (CF3CH2CH2O)3PˆO has been made [6,7].
Some related phosphates have the general formula
[H(CF2)nCH2O]3PˆO. Members with an even number of
di¯uoromethylene groups (n ˆ 2, 4, 6 or 8) have been
prepared by route A [12,13] or route B [5], by ¯uoro-
alcoholysis of phosphorus pentoxide [14], by dinitrogen
tetraoxide oxidation of tris(¯uoroalkyl) phosphites [15],
or by pyrolysis of bis(¯uoroalkyl) phosphoric acids [15].
* Corresponding author. Tel.: ‡44-1980-613566;
fax: ‡44-1980-613371.
1 Organic phosphorus compounds are named after the corresponding
parent acids. Most of the substances described in this paper are derivatives
of phosphoric acid (HO)3P=O. Compounds of structure (RFO)3P=O are
symmetrical phosphates or tris(fluoroalkyl) phosphates, while those of
0
structure (RFO)2P(O)ORF are unsymmetrical phosphates or bis(fluoro-
alkyl) fluoroalkyl phosphates.
0022-1139/00/$ ± see front matter # 2000 Elsevier Science S.A. All rights reserved.
PII: S 0 0 2 2 - 1 1 3 9 ( 0 0 ) 0 0 3 2 7 - 4

154
C.M. Timperley et al. / Journal of Fluorine Chemistry 106 (2000) 153±161
Table 1
Surprisingly few unsymmetrical tris(¯uoroalkyl) phosphates
have been reported; the molecule (CF3CH2O)2P(O)OC-
(Me)2(CF2)4H is a rare example [16].
Experimental data for symmetrical phosphates (RFO)3P=O
Compound
RF
Yield (%)
Bp (8C/mmHg)
Previous work from this laboratory described the pre-
paration of dialkyl ¯uoroalkyl phosphates (RO)2P(O)ORF
[17] and bis(¯uoroalkyl) alkyl phosphates (RFO)2P(O)OR
[18]. This paper addresses the synthesis of some symme-
trical and unsymmetrical tris(¯uoroalkyl) phosphates. Sym-
metrical phosphates were made by the direct interaction of
phosphorus pentachloride with four molar equivalents of
¯uoroalcohol. The use of linear and branched ¯uoroalcohols
permitted the mechanism of reaction to be deduced.
7
8
CF3CH2
C2F5CH2
73
69
66
76
10
92
21
40/0.6a
64/0.9b
9
H(CF2)2CH2
C3F7CH2
102/0.015c
63/0.08d
49/0.02
mp 248Ce
62/0.8
10
11
12a
18
(FCH2)2CH
(CF3)2CH
C2F5(CH3)CH
a74±758C/9 mmHg [4], 186±1898C [5] and 738C/8 mmHg [6,7].
b678C/1.5 mmHg [6,7].
c250±2558C [5], 1218C/2 mmHg [13] and 1158C/1 mmHg [14].
d220±2238C [5], 968C/2.5 mmHg [6,7] and 78±808C/0.5 mmHg [10].
eThis compound has also been prepared by treatment of phosphorus
oxychloride with three molar equivalents of (CF3)2CHOLi in ether (90%
yield and mp 238C) [11].
Unsymmetrical phosphates were prepared by heating
phosphorochloridates 3±5 with ¯uoroalcohols in the pre-
sence of calcium chloride.
electron-acceptor groups on phosphorus stabilise the ®ve
coordinate state [20]; e.g. penta(tri¯uoroethoxy)phosphor-
ane (CF3CH2O)5P can be distilled without decomposition
[21].
2. Results and discussion
Primary ¯uoroalcohols containing three or more ¯uorine
atoms reacted rapidly with phosphorus pentachloride to
afford phosphates 7±10 in good yield (Table 1).
2.1. Synthesis of tris(fluoroalkyl) phosphates
The reaction of phosphorus pentabromide [2] or pen-
tachloride [5] with four moles of ¯uoroalcohol generates
one mole of tris(tri¯uoroalkyl) phosphate, one mole of
¯uoroalkyl halide, and four moles of hydrogen halide (refer
to route B in the Section 1). Chuganov and Sapgir [5]
reported the reactions of phosphorus pentachloride with
primary ¯uoroalcohols, but experimental details and spec-
troscopic data for the products were not recorded. Their
postulated mechanism involved instant generation of POCl3
(via elimination of ¯uoroalkyl halide from the phosphorane
RFCH2OPCl4) and its subsequent reaction with three mole-
cules of ¯uoroalcohol. However, phosphorus oxychloride is
normally unreactive towards ¯uoroalcohols under neutral or
acidic conditions [8,18]. Our studies were directed at solving
this apparent contradiction.
The secondary ¯uoroalcohol, 1,3-di¯uoroisopropanol,
gave a mixture of products identi®able by GC±MS, which
included mono- and bis-¯uoroalkyl phosphorochloridates
(FCH2)2CHOP(O)Cl2 and [(FCH2)2CHO]2P(O)Cl. Symme-
trical phosphate 11 was separated by fractionation. The low
yield, like that found with 2,2-di¯uoroethanol, shows that
sparsely ¯uorinated alcohols cannot form phosphates as
easily as highly ¯uorinated ones (perhaps as a consequence
of the lower stabilities of the phosphorane intermediates).
The reaction of 2-¯uoroethanol with phosphorus pen-
tachloride was not pursued owing to the high toxicity of
the alcohol [19]. The next homologue, 2,2-di¯uoroethanol,
yielded a mixture of tris(di¯uoroethyl) phosphate 2, phos-
phorochloridates 6a and 6b, and phosphorus oxychloride.
The reaction of hexa¯uoroisopropanol with phosphorus
pentachloride followed an unexpected course and
furnished two products: desired phosphate 12a and stable
intermediate 12b in a 3:7 ratio. The composition of the
mixture remained constant for repeat experiments and could
not be altered by fractionation as both products co-distilled.
The origin of the phosphate is not obvious; it did not
originate from phosphorane hydrolysis as anhydrous con-
ditions were used.
The individual yields parallel the stabilities of the phos-
phorane intermediates and their ease of elimination of
2-chloro-1,1-di¯uoroethane. The stabilities decrease in the
order (HCF2CH2O)4PCl > ꢀHCF2CH2O)3PCl2 > ꢀHCF2-
CH2O)2PCl3 > HCF2CH2OPCl4. It is recognised that

C.M. Timperley et al. / Journal of Fluorine Chemistry 106 (2000) 153±161
155
Tetra(hexa¯uoroisopropoxy)chlorophosphorane 12b is a
missing link in the hexa¯uoroisopropoxy-phosphorane
family: the related entities [(CF3)2CHO]3PCl2 and
[(CF3)2CHO]5P have already been isolated [11]. Like these,
the former is covalent, and is expected to have a trigonal
bipyramidal structure. The phosphorus chemical shift of
chlorophosphorane 12b is d 67 ppm, i.e. in the region typical
of covalent phosphoranes. It did not give a molecular ion in
the high-resolution mass spectrum, but ions of m/z 715 and
m/z 699 were prominent, corresponding respectively to loss
of F and Cl from the molecule. The high stability of 12b
compared to analogues derived from primary ¯uoroalcohols,
e.g. (C2F5CH2O)4PCl, is due to the greater electron-with-
drawing ability of the hexa¯uoroisopropoxy group and its
greater bulk which disfavours the Arbusov rearrangement:
Tetra(hexa¯uoroisopropoxy)chlorophosphorane 12b is
sensitive to moisture. Addition of water to the 3:7 phos-
phate±phosphorane mixture resulted in rapid hydrolysis of
the phosphorane, allowing the isolation of pure tris(hexa-
¯uoroisopropyl) phosphate 12a. Alternative routes to this
compound involve hydrolysis of the phosphoranes
[(CF3)2CHO]3PCl2 and [(CF3)2CHO]5P [11].
Methanolysis of 12b resulted in substitution of the chlor-
ine atom, probably via an octahedral intermediate [21], to
give 50% methoxyphosphorane 13 (Fig. 1). Further reaction
gave the unstable dimethoxyphosphorane 14 which col-
lapsed by two pathways to give 12% bis(hexa¯uoroisopro-
pyl) methyl phosphate 15 (via loss of hexa¯uoroisopropyl
methyl ether) and 6% dimethyl hexa¯uoroisopropyl phos-
phate 16 (via loss of bis(hexa¯uoroisopropyl)ether).
Unstable dimethoxyphosphorane 14 also underwent metha-
nolysis to trimethoxyphosphorane 17 which collapsed, pre-
sumably by loss of bis(hexa¯uoroisopropyl)ether, to give a
trace of trimethyl phosphate.
The products were identi®ed by analysis by NMR and
GC±MS, a standard of compound 15 existing from current
work2 and one of compound 16 existing from previous work
[17]; trimethyl phosphate is available commercially. Meth-
oxyphosphorane 13, like other ¯uoroalkoxy-substituted
phosphoranes [11], did not give a molecular ion in its mass
spectrum, but gave a minor peak at m/z 699 (loss of a
methoxy group) and a major peak at m/z 563 (loss of a
hexa¯uoroisopropoxy group). Its phosphorus chemical shift
is d-83 ppm. The formation of ¯uoroethers as by-products is
assumed. It is however known that Ph3P(OCH2CF3)2 reacts
Fig. 1. The methanolysis of tetra(hexafluoroisopropoxy)chlorophosphor-
ane.
rapidly with alcohols to afford tri¯uoroethyl ethers [22]. The
possibility that phosphates 15 and 16 might arise from
transesteri®cation of the tris(hexa¯uoroisopropyl) phos-
phate in the starting mixture was excluded as its proportion
remained constant before and after the reaction. Tris(¯uoro-
alkyl) phosphates are also unreactive towards alcohols such
as butanol (see Section 2.3).
The multiple reaction pathways clearly show the desta-
bilising effect of increased alkoxy substitution on penta-
coordinate phosphorus. Interestingly, phosphorane 14
bearing hexa¯uoroisopropyl and methoxy groups eliminated
a larger proportion of the unsymmetrical methoxy ether
(CF3)2CHOMe compared to the symmetrical ¯uoroether
(CF3)2CHOCH(CF3)2; ejection of dimethyl ether was not
apparent (see Fig. 1).
The reaction of racemic 3,3,4,4,4-penta¯uoro-2-butanol
with phosphorus pentachloride did not provide a stable
phosphorane, but instead gave the symmetrical phosphate
18 in poor yield. This phosphate contains three chiral ester
groups. A pair of diastereoisomers form, one when the three
2 The synthesis of pure bis(hexafluoroisopropyl) phosphorochloridate
[(CF3)2CHO]2P(O)Cl, a potent electrophile, and its reaction with methanol
and triethylamine in ether to furnish phosphate 15 will be discussed in a
later paper.

Table 2
Spectroscopic data for symmetrical tris(fluoroalkyl) phosphates (RFO)3P=O (NMR data measured in CDCl3)
1
Compound 1H NMR d, J (Hz)
13C NMR d, J (Hz)
19F NMR d, J (Hz)
31P NMR d
IR n (cm
)
HRMS analysis
7
8
4.43 (6H, dq, J ˆ 8, 12, OCH2) 122 (dq, J ˆ 9, 276, CF3),
64.3 (dq, J ˆ 4, 40, OCH2)
74.5 (9F, t, J ˆ 7, CF3)
3.7
1460, 1425, 1288 (P=O), 1178,
1084, 964, 899, 845
Calculated C6H6F9O4P 343.986,
found 343.985 (error 3.4 ppm)
Calculated C9H6F15O4P 493.976,
found 493.975 (error 2.4 ppm)
4.5 (6H, dt, J ˆ 8, 12, OCH2)
118.2 (tq, J ˆ 35, 285, CF3),
111.2 (dtq, J ˆ 10, 257, 36,
CF2), 63.5 (dt, J ˆ 4, 28, OCH2)
124.5 (6F, t, J ˆ 12, CF2),
83.2 (9F, m, J ˆ 12, CF3)
4.0
3.5
3.4
1356, 1308 (P=O), 1205, 1163,
1113, 1068, 1032, 937, 897
9
5.92 (3H, tt, J ˆ 3, 43, CF2H), 113.3 (dtt, J ˆ 9, 30, 250, CF2),
4.46 (6H, dt, J ˆ 5, 13, OCH2) 107 (tt, J ˆ 37, 287, CF2H),
63.6 (dt, J ˆ 6, 31, OCH2)
136.5 (6F, d, J ˆ 43, CF2H),
123.7 (6F, dt, J ˆ 3, 13, CF2)
1460, 1404, 1294 (P=O), 1240,
1215, 1109, 1070, 951, 899, 835
Calculated C9H9F12O4P 440.005,
found 439.999 (error 12.7 ppm)
10
4.55 (6H, dt, J ˆ 8, 12, OCH2) 117.2 (tq, J ˆ 34, 287, CF3),
113.1 (ttd, J ˆ 258, 31,
127.3 (6F, m, CH2CF2),
121.5 (6F, m, CF2CF3),
80.7 (9F, m, CF3)
1460, 1410, 1356, 1301 (P=O),
1232, 1186, 1126, 1086, 1016,
931
Calculated C12H6F21O4P
643.967, found 643.966
(error 0.7 ppm)
9, OCH2CF2), 108.4a
(t, J ˆ 265, CF2CF3),
63.7 (td, J ˆ 25, 3, OCH2)
11
5.1 (3H, complex m, OCH),
4.6 and 4.8 (12H, complex m,
CH2F)b
80 (ddd, J ˆ 174, 7, 7, CH2F),
78.6 (dt, J ˆ 9, 21, OCH)
46.3 (6F, dt, J ˆ 18, 47,
8.6
3.6
1460, 1412, 1290 (P=O), 1088,
1051, 999, 908
Calculated C9H15F6O4P 332.061
‡
CH2F)
([M±CH2FŠ ˆ 299:047),
found 299.046 (error 4.7)
Calculated C9H3F18O4P 547.948,
found 547.948 (error 0.5 ppm)
Calculated C12H12F15O4P
536.023, found 536.017
(error 11 ppm)
12a
18
5.1 (3H, br m, OCH)
119.7 (dq, J ˆ 10, 282, CF3),
74.4 (dsep, J ˆ 14, 35, OCH)
118 (tq, J ˆ 38, 285, CF3),
112 (m, CF2), 72 (br t, OCH),
14.3 (s, CH3)
73.3 (18F, d, J ˆ 5, CF3)
1379, 1355, 1290 (P=O), 1237,
1115, 909, 881, 819
4.87 (3H, m, OCH),
1.55 (9H, br m, CH3)
Very complex due to the
existence of two
diastereoisomers
6.2 and 4.7 1458, 1394, 1327, 1288 (P=O),
1253, 1203, 1159, 1130, 1080,
1045, 991, 968, 843
a Complicated by two sets of 2JC
.
F
b The proton spectrum is second order and is very complex (perhaps an AA0BB0CMX system; this would need a computer simulation to resolve and is not amenable to first order analysis).

C.M. Timperley et al. / Journal of Fluorine Chemistry 106 (2000) 153±161
157
ester groups are of equal con®guration (i.e. RRR or SSS Ð
two possibilities), and the other when they are of mixed
con®guration (i.e. RSS, SSR, RSR, SRS, SRR, RRS Ð six
possibilities). The expected 1:3 mixture was observed by
phosphorus NMR spectroscopy (see Table 2).
Bis(¯uoroethyl)phosphorodichloridate 4 also combined
with primary ¯uoroalcohols to give unsymmetrical phos-
phates 24±26 in reasonable yield (Table 3). The reaction
with penta¯uoropropanol was scaled up to provide over 50 g
of pure bis(tri¯uoroethyl) penta¯uoropropyl phosphate 24
(see Section 4.8)
Tertiary ¯uoroalcohols did not combine with phosphorus
pentachloride; CF3(CH3)2COH, CH3(CF3)2COH and
(CF3)3COH remained unchanged. The cyclic ¯uoroalcohols,
2,2,3,3-tetra¯uorocyclobutanol 19 and (per¯uorocyclohex-
yl)methanol 20, gave complex mixtures; no attempt
was made to purify and characterise the individual compo-
nents.
Similarly, bis(penta¯uoropropyl)phosphorochloridate 5
combined with tetra¯uoropropanol and hepta¯uorobutanol
to afford phosphates 27 and 28 in good yields.
The symmetrical ¯uoroalkyl phosphates that were iso-
lated were colourless stable liquids. Their yields and boiling
points are given in Table 1 and spectroscopic data in Table 2.
Like the symmetrical phosphates, the unsymmetrical
¯uoroalkyl phosphates were isolated as colourless stable
liquids. Their yields and boiling points are given in Table 3
and spectroscopic data in Table 4.
2.2. Synthesis of bis(fluoroalkyl) fluoroalkyl phosphates
The reaction of ¯uorinated alcohols with phosphoryl
chlorides generally takes place in the presence of base
[8,18] but not under neutral or acidic conditions. One
way of facilitating nucleophilic attack is to use a Lewis
acid which increases the positive charge on phosphorus by
coordination to the oxygen atom of the P=O group [16].
Un¯uorinated phosphorus ester groups often undergo clea-
vage of the carbon±oxygen bond under these conditions due
to release of hydrogen chloride. However, as shown in the
¯uoroalcoholysis of phosphorus pentachloride, ¯uorinated
phosphorus ester groups are not cleaved by hydrogen chlor-
ide even on prolonged heating. This has enabled the synth-
esis of many symmetrical phosphates having ¯uoro aliphatic
[7,10,16,23,24] and aromatic [16,25±32] substituents, with
Group I±III metal salts being used as catalysts. In the present
study, some ¯uoroalkyl-substituted phosphoryl chlorides
were found to react with several aliphatic ¯uoroalcohols
in the presence of 5% calcium chloride catalyst to afford
unsymmetrical ¯uoroalkyl phosphates.
2.3. The reactivity of bis(trifluoroethyl) pentafluoropropyl
phosphate to nucleophiles
To end speculation concerning the potential reactivity of
the mixed phosphates to nucleophiles, compound 24 was
treated in separate experiments with molar equivalents of
butanol and propylamine. In both cases, no products were
detected by GC±MS analyses and the starting phosphate was
recovered unchanged (see Section 4.9).
Table 3
Experimental data for unsymmetrical phosphates
0
Compound
RF
RF
Yield (%)
Bp (8C/mmHg)
0
Tri¯uoroethyl phosphorodichloridate 3 combined with
primary ¯uoroalcohols to give phosphates 21±23 in mod-
erate yield (Table 3). The secondary ¯uoroalcohol
(CF3)2CHOH, or the tertiary ¯uoroalcohols CF3(CH3)2COH
and CH3(CF3)2COH, did not react.
Products of general formula RFCH2OP(O)(OCH2RF )2
21
22
23
CF3
CF3
CF3
C2F5
(CF2)2H
C3F7
69
58
65
100/10
124/5
100/1
0
Products of general formula (RFCH2O)2P(O)OCH2RF
24
25
26
27
28
CF3
CF3
CF3
C2F5
C2F5
C2F5
68a
46
55
83
80
82/10
100/10
85/10
94/5
(CF2)2H
C3F7
(CF2)2H
C3F7
104/10
a In the scale-up reaction, an improved yield of 77% was achieved, the
boiling point being 738C/5 mmHg (see Section 4.8).

Table 4
Spectroscopic data for unsymmetrical phosphates RFCH2OP(O)(OCH2RF )2 and (RFCH2O)2P(O)OCH2RF (NMR data measured in CDCl3)
0
0
1
)
Compound 1H NMR d, J (Hz)
13C NMR d, J (Hz)a
19F NMR d, J (Hz)
31P NMR d IR n (cm
HRMS analysis
21
4.51 (4H, dt, J ˆ 4,
12, OCH2C2F5),
4.51 (2H, dq, J ˆ 9, 7,
OCH2CF3)
122 (tq, J ˆ 34, 286, CF2CF3),
121.9 (dq, J ˆ 13, 286, CF3),
113.3 (dtq, J ˆ 9, 255, 37, CF2),
64.3 (q, J ˆ 39, OCH2CF3),
63.4 (t, J ˆ 30, OCH2CF2)
122 (dq, J ˆ 11, 278, CF3),
113.3 (dtt, J ˆ 9, 29, 250,
124.5 (4F, t, J ˆ 13,
CF2), 83.2 (6F, br m,
CF3), 75.2 (3F, t, J ˆ 8,
CH2CF3)
3.9
1460, 1356, 1308, 1282 (P=O), Calculated C8H6F13O4P 443.980,
1207, 1074, 1034, 966, 897 found 443.978 (error 4.5 ppm)
22
5.92 (2H, tt, J ˆ 4, 36, CF2H),
4.46 (4H, dtt, J ˆ 8, 1, 12,
OCH2CF2CF2), 4.42 (2H, dq,
J ˆ 8, 9, OCH2CF3)
137.3 (4F, d, J ˆ 52,
CF2H), 124.5 (4F, t,
J ˆ 13, CH2CF2),
3.6
1458, 1423, 1282 (P=O), 1240, Calculated C8H8F11O4P 407.998
‡
1184, 1076, 964, 899, 835
([M±F] ˆ389.000), found
CH2CF2), 109 (tt, J ˆ 39, 251,
CF2H), 64.3 (dq, J ˆ 5, 39,
CH2CF3), 63.6 (dt, J ˆ 6, 30,
CH2CF2)
388.998 (error 4.2 ppm)
75.3 (3F, t, J ˆ 6, CF3)
23
24
25
4.55 (4H, dt, J ˆ 9, 13,
OCH2CF2), 4.43 (2H, dq,
J ˆ 9, 8, OCH2CF3)
121.9 (dq, J ˆ 10, 278, CH2CF3),
115-110 (m, J obs, CF2CF2),
107 (m, J obs, CF3),
126.7 (4F, br m, CH2CF2),
120.9 (4F, br m, CF2),
3.8
3.8
3.7
1458, 1356, 1282 (P=O), 1230, Calculated C10H6F17O4P
1182, 1082, 1016, 966, 930
543.973, found 543.972
(error 2.8 ppm)
80.1 (6F, t, J ˆ 10, CF3),
74.7 (3F, t, J ˆ 9, CH2CF3)
64.4 (dq, J ˆ 4, 38, CH2CF3),
63.6 (br t, J ˆ 26, CH2CF2)
122 (dq, J ˆ 10, 278, CH2CF3),
118 (tq, J ˆ 34, 286, CF3),
113 (dtq, J ˆ 8, 38, 278, CF2),
64.3 (dq, J ˆ 5, 38, CH2CF3),
63.3 (dt, J ˆ 4, 29, CH2CF2)
122.1 (dq, J ˆ 9, 278, CF3),
113.5 (dtt, J ˆ 9, 28, 250, CF2),
109.1 (tt, J ˆ 36, 251, CF2H),
64.4 (dq, J ˆ 5, 38, OCH2CF3),
63.8 (dt, J ˆ 4, 29, OCH2CF2)
121.9 (dq, J ˆ 13, 280, OCH2CF3),
117.4 (tq, J ˆ 39, 287, CF2CF2CF3),
113 (dtt, J ˆ 10, 33, 258, OCH2CF2),
109 (tq, J ˆ 271, 37, CF2CF2CF3)
118.1 (tq, J ˆ 33, 288, CF3),
4.51 (2H, dtq, J ˆ 8, 12, 1,
OCH2CF2), 4.43 (4H, dq,
J ˆ 9, 8, OCH2CF3)
124.5 (2F, m, CH2CF2),
83.3 (3F, m, CF3),
1459, 1424, 1305, 1279 (P=O), Calculated C7H6F11O4P 393.983,
1179, 1081, 1033, 965, 898,
845, 810
found 393.982 (error 0.9 ppm)
75.2 (6F, m, CH2CF3)
5.92 (1H, tt, J ˆ 4, 56,
CF2H), 4.48 (2H, br dt,
J ˆ 8, OCH2CF2), 4.43 (4H, dq,
J ˆ 9, 8, OCH2CF3)
137.2 (2F, m, J ˆ 61,
1458, 1424, 1274 (P=O), 1239, Calculated C7H7F10O4P 375.992,
1109, 964, 938, 898, 840 found 375.990 (error 6.8 ppm)
CF2H), 124.5 (2F, br m,
CF2), 75.2 (6F, br m, CF3)
26
27
4.6 (2H, dt, J ˆ 7, 13,
OCH2C3F7), 4.43 (4H, dq,
J ˆ 8, 8, OCH2CF3)
126.5 (2F, m, OCH2CF2),
121 (2F, m, CF2CF3),
80 (3F, CF2CF3),
3.7
3.8
1458, 1306, 1279 (P=O), 1234, Calculated C8H6F13O4P 443.980,
1182, 1086, 1016, 966,
903, 845
found 443.789 (error 2.1 ppm)
72.5 (6F, m, CH2CF3)
136.4 (2F, d, J ˆ 52,
5.91 (1H, tt, J ˆ 3, 52, CF2H),
1460, 1356, 1306 (P=O), 1209, Calculated C9H7F14O4P 475.986,
4.5 (4H, m, J ˆ 8, 14, OCH2CF3), 111 (m, J obs, ꢁ64, both types of CF2), CF2H), 123.6 (2F, t,
1113, 1070, 1032, 937, 897,
835
found 475.983 (error 5 ppm)
4.48 (2H, m, J ˆ 8, 6,
109 (tt, J ˆ 36, 251, CF2H),
63.7 (dt, J ˆ 6, 31, CH2CF2CF2),
63.4 (dt, J ˆ 5, 29, CH2C2F5)
J ˆ 14, CF2CF2H),
OCH2CF2CF2H)
123.6 (4F, t, J ˆ 13,
CF2CF3), 82.6 (6F, s, CF3)
126.6 (2F, m, CF2CF2),
123.8 (4F, m, CF2CF3),
120.9 (2F, m, CF2C2F5),
82.7 (6F, m, CF2CF3),
80 (3F, m, CF2CF2CF3)
28
4.55 and 4.51 (4H, each pair ddd, 118.3 (tq, J ˆ 36, 284, CH2CF2CF3),
3.9
1460, 1377, 1356, 1307 (PˆO), Calculated C10H6F17O4P
J ˆ 7, 13, one of coupling
constants obscured because of
overlap, pair of enantiotopic
protons in OCH2C2F5 groups),
4.51 (2H, dt, J ˆ 8, 12,
OCH2C3F7)
117.7 (tq, J ˆ 29, 287), 111.5 (dtq,
J ˆ 9, 257, 36, CH2CF2CF3), 111 and
107 (m, J obs, CH2CF2CF2), 63.8 (dt,
J ˆ 4, 27, OCH2C3F7), 63.6 (dt, J ˆ 4,
29, OCH2C2F5)
1209, 1126, 1074, 1034,
937, 897, 820
543.973, found 543.971
(error 3.3 ppm)
a In the carbon spectra, obs indicates that the signals are obscured due to complex splitting patterns and signal-to-noise problems.

C.M. Timperley et al. / Journal of Fluorine Chemistry 106 (2000) 153±161
159
3. Conclusion
4.1. Reaction of fluoroalcohols with phosphorus
pentachloride
Symmetrical ¯uoroalkyl phosphates can be prepared
from the interaction of primary or secondary ¯uoroalcohols
with phosphorus pentachloride; tertiary ¯uoroalcohols
do not react under these conditions. A requirement for a
high yield of phosphate is the presence of many ¯uorine
atoms in the ¯uoroalcohol. With hexa¯uoroisopropanol
The ¯uoroalcohol (0.2 mol) was added dropwise using a
pressure-equalising dropping funnel (equipped with a cal-
cium chloride guard tube) to ®nely-divided phosphorus
pentachloride (0.05 mol) in a round-bottom ¯ask cooled
to 0±58C. Contact of the ¯uoroalcohol with the solid phos-
phorus pentachloride resulted in dissolution, giving a col-
ourless solution that effervesced due to liberation of HCl and
the respective ¯uoroalkyl chloride. After addition, the mix-
ture was warmed to room temperature and left for 12 h. An
aliquot was then analysed by GC±MS. In cases where good
conversion to the required product had occurred, residual
phosphorus pentachloride was removed by ®ltration. Frac-
tionation under reduced pressure (0.015±0.9 mmHg) gave
tris(¯uoroalkyl)phosphates 7±11 and 18 as colourless
liquids. Yields ranged from 10 to 76% (see Table 1).
the reaction followed
a
surprising course, giving
the expected symmetrical phosphate and the unexpected
tetra-(hexa¯uoroisopropoxy) chlorophosphorane. This out-
come indicates that ¯uoroalcoholysis of PCl5 is mediated
through chlorophosphorane intermediates, rather than by
formation of POCl3 and its subsequent transformation
(as proposed by Chuganov and Sapgir [5]). Unsymmetri-
cal ¯uoroalkyl phosphates can be prepared from the
interaction of primary ¯uoroalcohols with phosphoryl
chlorides in the presence of calcium chloride; secondary
or tertiary ¯uoroalcohols are unreactive under these
conditions.
4.2. Reaction of hexafluoroisopropanol with phosphorus
pentachloride
4. Experimental details
The previous procedure was followed. As some unreacted
phosphorus pentachloride remained after addition of hexa-
¯uoroisopropanol, the mixture was re¯uxed for 2 h, then
distilled under reduced pressure (bp 408C/0.08 mmHg).
Multinuclear NMR analysis showed the distillate to com-
prise 30% tris(hexa¯uoroisopropyl)phosphate 12a and 70%
tetra(hexa¯uoroisopropoxy)chlorophosphorane 12b. A por-
tion of the mixture (10 g) was treated with ice water (5 g) in
chloroform (20 ml). The product, the lowest of three layers,
was separated and concentrated under reduced pressure to
give pure tris(hexa¯uoroisopropyl)phosphate 12a as white
crystals (11.2 g, 92%); mp 248C (lit. mp 238C [11]). HRMS
for phosphorane 12b: calculated for C12H4ClF24O4P
All reagents were of commercial quality: ¯uoroalcohols
were purchased from Apollo Scienti®c Ltd (Derbyshire,
UK) or from Lancaster Synthesis (Morecambe, UK). Anhy-
drous solvents were used for reactions. NMR spectra were
obtained on a JEOL Lambda 500 instrument (operating at
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 in Tables 2 and 4 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, obs:
obscured signal from which coupling constants could
not be extracted), coupling constant (Hz) and assignment.
IR spectra were recorded as liquid ®lms on a Nicolet
SP210 instrument using Omnic sofware. Reaction mixtures
were monitored by gas chromatography±mass spectrometry
(GC±MS) using a Finnigan MAT GCQ instrument with
chemical ionisation (CI) using methane as reagent gas.
Molecular masses of pure products were con®rmed
with methane ‡ve CI data. Elemental analysis was carried
out on the largest stable fragment ion, using high resolution
mass spectrometry (HRMS) on a Micromass Autospec
SQ Double Focusing Magnetic Sector instrument.
Mode: ‡ve ion electron impact, magnet scan m/z 400±
100 (seconds/decade), resolution 2900. Inlet: septum
(1608C), 0.2 ml introduced. Source conditions: temperature
2008C, electron energy 70 eV, and accelerating voltage
8000 V.
‡
‡
733.915 ([M±FŠ ˆ 714:917 and [M±ClŠ ˆ 698:946),
found 714.916 (error 1.1 ppm) and 698.946 (error 1.1 ppm).
4.3. Attempted synthesis of tris(2,2,3,3-
tetrafluorocyclobutyl) phosphate
The method was essentially the same as that outlined in
Section 4.1. After addition of 2,2,3,3-tetra¯uorocyclobuta-
nol 19, the reaction mixture set solid and was left for 14 h.
On heating, it melted and the resulting liquid was re¯uxed
for 3 h, then distilled to give a colourless oil (bp 1188C/
0.5 mmHg) which on standing crystallised to give a
white solid (mp 40±428C). The solid contained two
phosphorus compounds that were not separated or charac-
terised.
4.4. Attempted synthesis of tris[(perfluorocyclohexyl)
methyl] phosphate
The method was essentially the same as that outlined in
Section 4.1. After addition of the (per¯uorocyclohexyl)-

160
C.M. Timperley et al. / Journal of Fluorine Chemistry 106 (2000) 153±161
methanol 20, the mixture was allowed to warm to room
temperature and then re¯uxed for 6 h (until all the solid went
into solution) to produce a very viscous oil. The oil was
distilled (bp 1348C/0.01 mmHg) and shown by multinuclear
NMR analysis to contain ®ve different phosphorus com-
pounds. No attempt was made to separate or characterise the
individual compounds.
pressure gave the title compound as a colourless mobile
liquid (51.8 g, 77%); bp 738C/5 mmHg.
4.9. Attempted reaction of unsymmetrical phosphate (24)
with butanol or propylamine
Butanol or propylamine (6 mmol) were introduced by
syringe into a solution of bis(2,2,2-tri¯uoroethyl) 2,2,3,3,3-
penta¯uoropropyl phosphate 24 (6 mmol) in dichloro-
methane (10 ml) at room temperature under argon. Analysis
by GC±MS showed no reaction to have taken place after
12 h. The starting phosphate was recovered by distillation
under reduced pressure (bp 528C/1 mmHg).
4.5. Methanolysis of tetra(1,1,1,3,3,3-
hexafluoroisopropoxy)chlorophosphorane (12b)
The 3:7 mixture of tris(hexa¯uoroisopropyl)phosphate
12a and tetra(hexa¯uoro-isopropoxy)chlorophosphorane
12b (2 g), made according to the procedure in Section
4.2, was weighed into an oven-dried separating funnel
and methanol added by syringe (0.1 ml). The methanol
formed a top layer that dissolved slowly with evolution
of HCl gas. Analysis by GC±MS and NMR spectro-
scopy showed the mixture to comprise phosphate 12a,
tetra(hexa¯uoroisopropoxy)methoxyphosphorane 13, bis-
(hexa¯uoroisopropyl) methyl phosphate 15, dimethyl hexa-
¯uoroisopropyl phosphate 16 and trimethyl phosphate.
Acknowledgements
Many thanks to Alison Bussey and Steve Marriott for
providing the infrared data. We also wish to thank DERA
Haslar (Environmental Sciences) for funding the work.
References
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