Synthesis and characterization of per/polyfluorophenoxy derivatives of octachlorocyclotetraphosphazenes

Article abstract of DOI:10.1016/S0022-1139(01)00516-4

Octachlorocyclotetraphosphazene was treated with various fluorinated phenols to form partially and completely substituted cyclotetraphosphazenes. The mono-substitution reactions were carried out using a base in benzene while for complete substitution sodium salts of the corresponding phenoxides were used. All compounds were characterized by ¹H, ¹⁹F, and ³¹P NMR, IR and mass spectroscopic methods. A crystal structure was obtained for N₄P₄(OC₆F₅)₈, and shows that the phosphazene ring is puckered. The angle of the planes N2P2N1P1N4 to N4P4N3P3N2 is 45.5° and the angle of the planes N1P1N4P4N3 to N3P3N2P2N1 is 43.8°.

Full text of DOI:10.1016/S0022-1139(01)00516-4

Journal of Fluorine Chemistry 112 42001) 307±312
Synthesis and characterization of per/poly¯uorophenoxy
derivatives of octachlorocyclotetraphosphazenes
Krista L. Rule, Immanuel I. Selvaraj, Robert L. Kirchmeier*
Department of Chemistry, University of Idaho, Moscow, ID 83844-2343, USA
Received 31 July 2001; accepted 31 August 2001
Abstract
Octachlorocyclotetraphosphazene was treated with various ¯uorinated phenols to form partially and completely substituted cyclotetra-
phosphazenes. The mono-substitution reactions were carried out using a base in benzene while for complete substitution sodium salts of the
corresponding phenoxides were used. All compounds were characterized by 1H, 19F, and 31P NMR, IR and mass spectroscopic methods. A
crystal structure was obtained for N4P44OC6F5)8, and shows that the phosphazene ring is puckered. The angle of the planes N2P2N1P1N4 to
N4P4N3P3N2 is 45.58 and the angle of the planes N1P1N4P4N3 to N3P3N2P2N1 is 43.88. # 2001 Elsevier Science B.V. All rights reserved.
Keywords: Phosphazene; Tetramer; Fluoroalkoxide; Single crystal analysis
1. Introduction
Sodium hydride, triethylamine, p-¯uorophenol, penta¯uor-
ophenol, p-tri¯uoromethyl-phenol 4Aldrich) were used as
received. 4-Hydroxy-40-vinylbiphenyl was synthesized
according to [13].
Cyclotriphosphazenes 4I), 4Fig. 1) are one of the most
well studied inorganic heterocyclic systems known [1]. The
linear analogue polyphosphazenes 4II) are well known for
their use as membranes, polymer solid electrolytes, drug
carriers, and ¯ame retardants, etc. [2]. Although studies of
the cyclic trimer and the linear polyphosphazenes have been
well documented, the cyclotetraphosphazene 4III) systems
have not been well studied. Cyclotriphosphazenes contain-
ing ¯uorinated phenoxy groups are useful as lubricants and
for surface coatings in magnetic tapes and other end use
applications [3,4]. The ultimate focus of our research is the
preparation of organic polymers containing cyclotetrapho-
sphazenes as pendant groups [5] and the characterization of
these materials as surface coatings. In this study we report
the synthesis and characterization of mono-, di-, and octa-
substituted ¯uorophenoxycyclotetraphosphazenes. Some of
these compounds have been reported previously but were
poorly characterized [6].
2.2. Methods
1H and 19F NMR spectra were obtained on a Bruker
AC200 or Bruker AC300 instrument in CDCl3 solvent.
Chemical shift values were reported relative to TMS and
CCl3F for proton and ¯uorine, respectively. Infrared spectra
were recorded on a Perkin-Elmer 1710 FTIR spectrometer
‡
with KBr disks. Mass spectral data 4EI, FAB , and accurate
mass) were obtained using a Jeol JMS AX505HA mass
spectrometer.
2.2.1. X-ray diffraction studies
The X-ray diffraction data for compound 5 was collected
on a Siemens SMART diffractometer with a CCD detector at
À90 8C. Data collection parameters are listed in Table 1.
The frame data were acquired with the SMART [14±17]
software using a Siemens three-circle platform using Mo Ka
2. Experimental
Ê
radiation 4l ˆ 0:71073 A) from a ®ne-focus tube. The w-
axis on this platform is ®xed at 54.748, and the diffract-
ometer is equipped with a CCD detector maintained near
À54 8C. Cell constants are determined from 60, 10 s,
frames. A complete hemisphere of data is scanned on o
40.38) with a run time of 10 s per frame at a detector
resolution of 512 Â 512 pixels. A total of 1271 frames were
collected in three sets, and a ®nal set of 50 frames, were also
2.1. Materials
Octachlorocyclotetraphosphazene 4Otsuka Chemical Co.,
Ltd., Japan) was sublimed and recrystallized prior to use.
* Corresponding author. Fax: ‡1-208-885-6173.
E-mail address: rlkirch@uidaho.edu 4R.L. Kirchmeier).
0022-1139/01/$ ± see front matter # 2001 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 1 1 3 9 4 0 1 ) 0 0 5 1 6 - 4

308
K.L. Rule et al. / Journal of Fluorine Chemistry 112 12001) 307±312
Fig. 1. Phosphazene structures.
collected to determine the crystal decay. The frames were
then processed on a SGI-Indy/Indigo 2 workstation using
SAINT software, to give the hkl ®le corrected for Lp/decay.
The structure was solved by the direct method using the
SHELX-90 program and re®ned by a least squares method on
F2, SHELX-93, incorporated in SHELXTL-PC Version 5.03.
product 41) as a white solid 4yield, 44%). Melting point
‡
4mp) 65 8C. MS 4EI‡) 4species, intensity): 622 4M , 100);
accurate mass 4EI‡): 621.7679, 623.7644 4found) and
621.7674, 623.7645 4calculated); 31P NMR 4d, ppm):
1
À4.0 to À5.8 4mult), À10.7 4t, ±P4OR)Cl, J ˆ 34 Hz); H
NMR 4d, ppm): 7.7±7.2 4m, biphenyl, 8H); 6.8 4dd, ±CH,
1H, J ˆ 14 Hz); 5.8 4d, ±CH2, 1H, J ˆ 9 Hz); 5.3 4d, ±CH2,
1H, J ˆ 5 Hz); IR 4KBr, cmÀ1): 14934s); 1337 4vs); 1305
4vs); 1224 4s); 1196 4s); 1166 4s); 1019 4m); 970 4vs); 914
4m); 827 4s); 784 4m); 758 4m); 706 4m); 642 4m); 590 4vs);
575 4vs); 508 4vs).
2.2.2. Synthesis of N4P4Cl7±OC6H4±C6H4±CH=CH2 11)
To a stirred solution of dry benzene containing octachlor-
ocyclotetraphosphazene 42.0 g, 4.3 mmol), a solution of
4-hydroxy-40-vinyl-biphenyl 40.84 g, 4.3 mmol) and triethy-
lamine 40.4g, 4.3 mmol) in dry benzene was added slowly
over a period of 30 min at room temperature. The reaction
mixture was stirred for an additional 3 h. After removing the
triethyl amine hydrochloride formed in the reaction, the
solvent was removed under vacuum. The crude product was
puri®ed by column chromatography on silica gel using
hexanes:methylene chloride in a 4:1 ratio to afford the
2.2.3. Synthesis of N4P4Cl71OC6H4F-p) 12)
To a stirred solution of benzene containing 0.4 ml of
triethylamine, 1.0 g of octachlorocyclotetraphosphazene
and 0.24 g of p-¯uorophenol were added slowly under
nitrogen. The solution was stirred for 16 h at room tem-
perature under nitrogen. Benzene was removed and the
product was puri®ed with a silica gel column using 3:1
hexane/methylene chloride as mobile phase. The product
obtained 42) was an oil 40.61 g, 53% yield). MS 4EI‡)
Table 1
X-ray crystal data and intensity collection parameters for compound 5
‡
‡
4species, intensity): 538 4M À 1, 100); 426 4M ±OC6H4F,
29.1); accurate mass 4EI‡) m/z 539.1966 4found), 539.1869
4calculated); 31P NMR 4d, ppm): À12.0 4t, J ˆ 40 Hz); À6.2
Empirical formula
Color
C48F40N4O8P4
Colorless
Cryst size 4mm)
Cryst system, space group
0.38 Â 0.15 Â 0.05
Orthorhombic, Pbca
4mult); À6.3 4mult); 1H NMR 4d, ppm): 7.3±7.0 4mult); 19
F
NMR 4d, ppm): À116 4t, J ˆ 7:5 Hz); IR 4KBr, cmÀ1): 3082
4w); 2213 4w); 2018 4m); 1873 4w); 1641 4w); 1599 4w);
1502 4s); 1309 4vs); 1175 4vs); 1090 4m);1006 4w); 972 4s);
925 4w); 903 4m); 837 4s); 785 4m); 727 4m); 707 4m); 685
4m); 634 4w); 605 4vs); 497 4vs); 456 4m).
Unit cell dimension
Ê
a 4A)
Ê
b 4A)
24.067544)
17.622640)
26.111540)
90
Ê
c 4A)
a 48)
b 48)
g 48)
90
90
2.2.4. Synthesis of N4P4Cl61OC6H4F-p)2 13)
Ê 3
Volume 4A )
11074.742)
8
To a stirred solution of dry THF containing 0.07 g of
sodium hydride, 0.36 g of p-¯uorophenol in dry THF was
added slowly under nitrogen. The resulting solution was
added slowly to 1.0 g of octachlorocyclotetra-phosphazene
in dry THF. The reaction mixture was allowed to stir for 16 h
at room temperature under nitrogen. THF was removed and
the product was puri®ed using a silica gel column with 5:1
hexane/methylene chloride mobile phase. The product 43)
was obtained as an oil 40.47 g, 35% yield). MS 4EI‡)
Z
rcalc 4Mg mÀ3
F40 0 0)
)
1.972
6400
Absorption coefficient 4mmÀ1
Temperature 4K)
ymax 48)
Number of reflections collected
Final indices 42d data), R14wR2)
All data, R14wR2)
Goodness-of-fit, S4F2)
)
0.406
18342)
22.50
66517
0.091240.1384)
0.148740.1594)
1.100
Ê À3
‡
‡
Largest difference peak 4electron A
Ê À3
)
0.278
4species, intensity): 613 4M , 39), 503 4M ±OC6H4F,
100); accurate mass 4EI‡): 614.8375 4found), 614.8300
Largest difference hole 4electron A
)
À0.322

K.L. Rule et al. / Journal of Fluorine Chemistry 112 12001) 307±312
309
1
4calculated); H NMR 4d, ppm); 7.3±7.0 4mult); 19F NMR
4w); 1948 4w); 1872 4m); 1641 4m); 1602 4m); 1496 4s); 1366
4vs); 1346 4vs); 1229 4vs); 1179 4vs); 1090 4s); 945 4vs); 826
4vs); 791 4s); 744 4m); 718 4s); 671 4m); 633 4m); 554 4s).
4d, ppm): À116 4s); IR 4KBr, cmÀ1) 3083 4w); 2889 4w);
2360 4w); 2331 4w); 2239 4w); 2023 4w); 1874 4m); 1734
4w); 1642 4w); 1600 4m); 1501 4s); 1318 4vs); 1175 4vs);
1091 4m); 1011 4m); 966 4s); 927 4m); 909 4m); 782 4m); 726
4m); 708 4m); 683 4m); 635 4m); 592 4s); 510 4s).
2.2.6. Synthesis of N4P4 1OC6F5)8 15)
To a stirred solution of dry THF containing 0.13 g of
sodium hydride, 0.99 g of penta¯uorophenol in dry THF was
slowly added under nitrogen. The resulting sodium phen-
oxide was added slowly to 0.25 g of octachlorocyclotetra-
phosphazene in dry THF. The reaction mixture was re¯uxed
for 16 h under nitrogen. THF was removed and the product
was puri®ed on a silica gel column with a 3:1 hexane/
methylene chloride mobile phase. The product 45) was
obtained as a white crystaline solid. 40.54 g, 61% yield).
2.2.5. Synthesis of N4P41OC6H4F-p)8 14)
To a stirred solution of dry THF containing 0.11 g of
sodium hydride, 0.48 g of p-¯uorophenol in dry THF was
slowly added under nitrogen. The resulting sodium phen-
oxide was added slowly to 0.25 g of octachlorocyclotetra-
phosphazene in dry THF. The reaction mixture was re¯uxed
for 16 h under nitrogen. THF was removed and the product
was puri®ed using a silica gel column with a 2:1 hexane:-
methylene chloride mobile phase. This gave 44) as a white
solid 40.31 g, 54%). Accurate mass 4EI‡): 1068.1213
4found), 1068.1043 4calculated); 31P NMR 4d, ppm)
‡
‡
MS 4EI‡) 4species, intensity): 1643 4M 21) 1460 4M ±
OC6F5, 100), 31P NMR 4d, ppm) À10.9 4s); 19F NMR 4d,
ppm) À155 4d, J ˆ 10 Hz), À159 4t, J ˆ 12 Hz), À163
4mult); IR 4KBr, cmÀ1): 3438 4w); 2676 4w); 2470 4w);
2156 4w); 1752 4w); 1513 4s); 1482 4m); 1356 4s); 1308 4s);
1153 4s); 1025 4vs); 889 4m); 862 4m); 819 4w); 759 4s); 721
4m); 600 4m); 567 4m).
1
À11.5 4s); H NMR 4d): 6.8 4mult), 1.3 4s), 0.9 4mult);
19F NMR 4d, ppm); À118 4mult); IR 4KBr, cmÀ1): 3119 4m);
3083 4m); 2926 4m); 2562 4w); 2418 4w); 2331 4w); 2033
Scheme 1. Synthetic methods of title compounds.

310
K.L. Rule et al. / Journal of Fluorine Chemistry 112 12001) 307±312
2.2.7. Synthesis of N4P4 1OC6H4CF3-p)8 16)
phenoxides. Compounds 1, 4±6 were obtained as colorless
solids while 2 and 3 were viscous oils. Yields of 4±6, where
excess phenoxide was employed, were all high. The mono-
and di- substituted p-¯uorophenoxy derivatives were
obtained in low yields after puri®cation using a silica gel
column. The reason for the low yields is related to the
reactivity of the P±Cl bonds. After substitution of one of
the chlorines, the remaining P±Cl bonds become very reac-
tive giving multiply substituted products. Also, due to its
structural ¯exibility, the eight-membered ring is signi®-
cantly more reactive than the planar six-membered trimer
[6,7]. Several minor multiply substituted products were
separated from the main products in each reaction via thin
layer chromatography 4TLC) using hexanes and methylene
chloride in a 5:1 ratio on silica gel columns.
The phosphazene tetramers were characterized by multi-
nuclear NMR, IR, and mass spectral techniques. 31P NMR
showed three different phosphorus atoms in a AB2X
complex spectrum for 1. An up-®eld chemical shift cen-
tered at À10.7 ppm from the starting material 4À6.9 ppm)
was assigned to the biphenylyloxy substituted phosphorous
atom. The two phosphorous atoms adjacent to the sub-
stituted phosphorous and the fourth phosphorus atom
showed complex multiplets centered at approximately
À4.8 ppm 4Fig. 2). The same spectral pattern was obtained
for compound 2, the singly substituted p-¯uorophenoxy
derivative.
To a stirred solution of dry THF containing 0.14 g of
sodium hydride, 0.88 g of p-tri¯uoromethylphenol in dry
THF was slowly added under nitrogen. The resulting sodium
phenoxide was added slowly to 0.25 g of octachlorocyclo-
tetraphosphazene in dry THF. The reaction mixture was
allowed to stir at room temperature for 16 h under nitrogen.
THF was removed and the product was puri®ed using a
silica gel column with a 2:1 hexane/methylene chloride
mobile phase. The product 46) was obtained as a white solid
‡
40.53 g, 67%). MS 4EI‡) 4species, intensity) 1468 4M À 1,
‡
25), 1306 4M ±OC6H4CF3, 100); accurate mass 4EI‡):
1468.7518 4found), 1468.7514 4calculated); 31P NMR 4d,
ppm) À13.5 4s); 19F NMR 4d, ppm) À62.6 4s); IR 4KBr,
cmÀ1): 3086 4w); 1909 4w); 1781 4w); 1614 4s); 1513 4s); 1315
4vs); 1104 4vs); 1069 4s); 1018 4m); 964 4vs); 845 4s); 798 4m);
772 4m); 729 4m); 655 4s); 638 4m); 589 4m); 543 4m).
3. Results and discussion
Scheme 1 shows the synthetic methods used to prepare the
title compounds.
For the mono- and di-substituted products, triethylamine
was used as a hydrogen chloride scavenger. Complete
substitution of the chlorine present in the tetramer was
achieved by using the sodium salt of the corresponding
Fig. 2. 31P NMR spectra for N4P4Cl7±OC6H4±C6H4±CH=CH2 41).

K.L. Rule et al. / Journal of Fluorine Chemistry 112 12001) 307±312
311
Table 2
Previous studies reported in the literature have also
Ê
Selected bond lengths 4A) and bond angles 48) for N4P44OC6F5)8 45)
explored the chemistry of the complete replacement of
chlorine by ¯uoroalkoxy groups on cyclophosphazenes
[8±10]. Several studies on these reactions using various
equivalents of the substituting group showed such replace-
ments occur at non-geminal chlorine atoms [8,11]. Our
experience in this study is consistent with these earlier
reports. For example, mass spectral data obtained for pro-
duct 3 indicates non-geminal substitution. While it is
expected that the electron-accepting character of ¯uoroalk-
oxy groups would favor geminal nucleophilic substitution,
the substitution pattern seen is likely due to strengthening of
the P±Cl bonds as a result of the electron pairs on oxygen
[8].The single crystal X-ray experimental parameters for
compound 5 are given in Table 1. Table 2 shows selected
bond angles and bond distances. The P±N±P bond angles
were 133.244), 133.144), 133.844), and 136.444)8. Bond
angles found for the N±P±N bonds are 123.843), 122.543),
123.343), and 120.743)8. These values are greater than those
found for the trimeric system N3P34OC6H4F-p)6 [12]. The
N1±P2
N1±P1
N2±P3
N2±P2
N3±P3
N3±P4
N4±P4
1.55746)
1.56246)
1.55446)
1.56046)
1.54246)
1.57246)
1.55746)
N4±P1
O1±P1
O2±P1
O1±P2
O2±P2
O1±P3
O2±P3
O1±P4
O2±P4
1.55946)
1.58945)
1.58245)
1.59345)
1.58445)
1.59545)
1.58745)
1.60046)
1.58345)
P2±N1±P1
P3±N2±P2
P3±N3±P4
P4±N4±P1
133.244)
133.144)
133.844)
136.444)
Ê
average P±O bond distance of 1.589 A was similar to what
O2±P1±O1
O4±P2±O3
O6±P3±O5
O8±P4±O7
105.243)
101.743)
104.043)
100.043)
was found in the case of N3P34OC6H4F-p)6 [12]. The O±P±O
bond angles [105.243), 101.743), 104.043), and 100.043)8]
were signi®cantly larger than those found in the p-¯uorphe-
noxy trimer, i.e. 98.941), 94.742) and 99.241)8. The angle of
the planes N2P2N1P1N4 to N4P4N3P3N2 is 45.58. and the
angle of the planes N1P1N4P4N3 to N3P3N2P2N1 is 43.88
4Fig. 3).
N1±P1±N4
N1±P2±N2
N3±P3±N2
N4±P4±N3
123.843)
122.543)
123.343)
120.743)
Fig. 3. Crystal structure of N4P44OC6F5)8 45)

312
K.L. Rule et al. / Journal of Fluorine Chemistry 112 12001) 307±312
[5] I.I. Selvaraj, K.L. Rule, R.L. Kirchmeier, accepted for publication in
Acknowledgements
Journal of Polymer Science, 2001.
[6] S.S. Krishnamurthy, P.M. Sundaram, J. Chem. Soc., Dalton. Trans.
41982) 67.
We thank DoD-EPSCoR-ONR 4N00014-98-1-0587) for
®nancial support to carry out this research. The authors also
thank Dr. Michio Sasaoka, Otsuka Chemical Co., Ltd., for
the generous gift of octachlorocyclotetraphosphazene and
Dr. Gary Knerr for obtaining mass spectral data.
[7] P.O. Gitel', L.F. Osipova, O.P. Solovova, Zh. Obsh. Khim. 45 41975)
1749.
[8] V.N. Sharov, V. N Prons, V.V. Korol'ko, A.L. Klebanskii, G.P.
Kondratenkov, Zh. Obsh. Khim. 45 41975) 1953.
[9] J.L. Shmutz, J.R. Allcock, Inorg. Chem. 14 41975) 2433.
[10] R. Ratz, H. Schroeder, H. Ulrich, E. Kober, C. Grundmann, J. Am.
Chem. Soc. 84 41962) 55.
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