Synthesis and structural studies (1H, 13C, 31P NMR and X-ray) of new C-bonded cyclotriphosphazenes with heterocyclic substituents from novel phosphinic acid derivatives

Article abstract of DOI:10.1039/b311046j

Three new C-bonded cyclotriphosphazenes, [N₃P ₃(2-thienyl)₆], 2, [N₃P₃(3-thienyl) ₆], 4, and [N₃P₃(3,3′-bithienyl-2, 2′-ylene)₃], 6, have been prepared by two new synthetic procedures and are the first examples of non-spiro and trispirocyclotriphosphazene derivatives composed of thiophene and 3,3′-dithiophene substituents, respectively. Their ¹H, ¹³C and ³¹P NMR parameters are given. The solid state structures of 2, 4 and 6 have been determined by X-ray crystallography.

Full text of DOI:10.1039/b311046j

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P A P E R
13
31
Synthesis and structural studies (1H, C, P NMR and X-ray) of
new C-bonded cyclotriphosphazenes with heterocyclic substituents
from novel phosphinic acid derivatives
Virginie Vicente,a Alain Fruchier,a Marc Taillefer,a Corinne Combes-Chamalet,a
b
a
a
´
Ian J. Scowen, Franc¸oise Plenat and Henri-Jean Cristau*
a
Laboratoire de Chimie Organique (CNRS UMR. 5076), E. N. S. C. M., 8 rue de l’Ecole
Normale, 34296, Montpellier cedex 5, France. E-mail: cristau@cit.enscm.fr and
taillefe@cit.enscm.fr; Fax: +33 (0)4 67 14 43 19; Tel: +33 (0)4 67 14 43 12
Chemical and Forensic Sciences, University of Bradford, Bradford BD7 1DP, UK.
E-mail: i.scowen@Bradford.ac.uk; Fax: +44 (0)7769 886722; Tel: +44 (0)7769 886722
b
Received (in Toulouse, France) 10th September 2003, Accepted 24th October 2003
First published as an Advance Article on the web 13th February 2004
Three new C-bonded cyclotriphosphazenes, [N3P3(2-thienyl)6], 2, [N3P3(3-thienyl)6], 4, and [N3P3(3,30-bithienyl-
2,20-ylene)3], 6, have been prepared by two new synthetic procedures and are the first examples of non-spiro
and trispirocyclotriphosphazene derivatives composed of thiophene and 3,30-dithiophene substituents,
1
respectively. Their H, 13C and 31P NMR parameters are given. The solid state structures of 2, 4 and 6 have
been determined by X-ray crystallography.
triphosphazenes with heterocyclic substituents attached to the
P3N3 ring by phosphorus–carbon bonds, respectively the
Introduction
As compared with cyclotriphosphazenes (CTP) having P–O
or P–N side groups, cyclotriphosphazenes with substituents
linked to the skeleton via P–C bonds have been much less
described. However, both higher chemical and thermal stabili-
ties could be expected for this type of CTP, as already known
for polyphosphazenes.1–3 We describe here a new class of
stable hexasubstituted symmetric cyclotriphosphazenes having
P–C side groups (2,4 and 6; Scheme 1), which could be consid-
ered as potential materials precursors. Indeed, in these
cyclotriphosphazenes, the phosphorus substituents are either
free-rotating thienyl groups around the P–C bonds or rigidified
bithienyl groups. These compounds, thanks to their geometri-
cal properties, could lead by coordination of the free hetero-
atoms with transition metals to stacked structures (Fig. 1)
with potentially interesting electronic properties.
hexa(2-thienyl)- and hexa(3-thienyl)cyclotriphosphazenes
2
and 4 and the tri(3,30-bithienyl-2,20-ylene)cyclotriphosphazene
6 (Scheme 1).
Results and discussion
The nucleophilic substitution of hexahalogenocyclotriphos-
phazene N3P3X6 (X ¼ F, Cl) constitutes the more usual route
to prepare symmetric cyclotriphosphazenes substituted by
aromatic side groups through P–O or P–N bonds.4,5 This
method failed to produce the hexaphenylcyclotriphosphazene
N3P3Ph6 ,6 giving only partially substituted products when
N3P3Cl6 or N3P3F6 are allowed to react with nucleophilic spe-
cies like phenyl Grignard reagent7 or phenyllithium.8,9 For
example, the reaction of phenyllithium with N3P3F6 leads to
the creation of no more than five P–C bonds to give
N3P3FPh5 .8
We have thus developed synthetic methods that allowed
us to prepare the first examples of non-spiro and trispirocyclo-
Accordingly, we applied another pathway, previously used
in our laboratory10 to form the phosphazenic ring, to
the syntheses of hexa(2-thienyl)cyclotriphosphazene (2),
Scheme 1 Synthesis of cyclotriphosphazenes 2, 4 and 6: (i) 1.2 PPh3/
CCl4/Et3N in CH2Cl2 , 5 h, 40 ꢀC.
Fig. 1
T h i s j o u r n a l i s Q T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 4
418
N e w . J . C h e m . , 2 0 0 4 , 2 8 , 4 1 8 – 4 2 4

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hexa(3-thienyl)cyclotriphosphazene (4) and tri(3,30-bithienyl-
2,20-ylene)cyclotriphosphazene (6). This route (Scheme 1)
involves reaction of the appropriate phosphinic amide with
the Appel reagent11 (a mixture of triphenylphosphine, carbon
tetrachloride and triethylamine).
Synthesis of hexa(2-thienyl)cyclotriphosphazene (2)
Di(2-thienyl)phosphinic amide (1) has been prepared for the
first time according to the multistep synthesis described in
Scheme 2. Firstly, the N,N-diethylphosphinic amide 7 was
obtained (66%) by reaction of dichloro-N,N-diethylphosphinic
amide12 with the Grignard reagent of 2-bromothiophene.13
Then, in the presence of concentrated hydrochloric acid, it
gave di(2-thienyl)phosphinic acid (8), which was easily recov-
ered by filtration of the reaction mixture (98%). The phosphi-
nic acid 8 itself led to di(2-thienyl)phosphinic amide (1) in two
steps. The reaction of compound 8 with phosphorus pen-
tachloride gave the di(2-thienyl)phosphinic chloride 9, which
has not been isolated but directly added to a biphasic 1:1
diethyl ether–aqueous ammonia mixture to yield di(2-thienyl)-
phosphinic amide (1), recovered by column chromatography
(65%). The reaction of 1 with the Appel reagent (Scheme 1)
gave the expected cyclotriphosphazene 2 (34%), together with
triphenylphosphine oxide.11 N-Di(2-thienyl)phosphinyltriphe-
Scheme 3 New pathway for the synthesis of phosphinic amides 1
and 3.
to record the spectra in gated-decoupling mode or without
1H irradiation (Fig. 2). Another difference that may be useful
1
to identify the 31P signals of 1 and 10 is the value of JPC
,
which is 154.0 Hz in 1 and 127.9 Hz in 10. This coupling con-
stant is accessible from the 13C satellites of the 31P signals.
The best conditions were found to be a stoichiometry of
1 equiv. of P(O)Cl3 for 2 equiv. of the Grignard reagent at
ꢁ20 ꢀC. The intermediate halogenated compounds were not
isolated and the crude product was directly added to a biphasic
1:1 mixture of diethyl ether and 28% aqueous ammonia. The
phosphinic amide 1 and the tri(2-thienyl)phosphine oxide
1014,15 were readily separated by column chromatography.
Some traces of an unidentified monothiophenic compound,
detected from its 31P signal, were also observed.
=
nylphosphine imine [Ph3P N–P(O)R2] and (chloromethyl)tri-
phenylphosphonium chloride [Ph3PCH2Clþ Clꢁ] were also
obtained as by-products, as explained by the cyclisation
reaction mechanism given by Appel et al.11
This new pathway allowed us to obtain the phosphinic
amide 1 in two steps (yield of the one-pot procedure is 18%)
instead of five steps for the usual synthesis described in Scheme
2 (overall yield 37%).
With the aim to reduce the number of steps needed to
synthesise the di(2-thienyl)-phosphinic amide 1, trichlorophos-
phine oxide was allowed to react with varying amounts of the
Grignard reagent of 2-bromothiophene13 in THF (Scheme 3).
The reaction was followed by recording 31P spectra of the reac-
tion mixtures using conditions for quantitative measurements
(see Experimental). At the same time, it was found that the
31P signals of 1 and 10 were strongly dependent on solvent
and that the best way to identify them without ambiguity is
Synthesis of hexa(3-thienyl)cyclotriphosphazene (4)
The new phosphinic amide 3, required to synthesise the cyclo-
triphosphazene 4, was obtained according to the method
reported in Scheme 3. As previously, the 31P spectra of the
organic phase show the presence of nearly equal amounts of
the di(3-thienyl)phosphinic amide 3 and its corresponding
phosphine oxide 11.15 The pure compounds were isolated with
18% (3) and 14% (11) yields.
The presence of the two compounds 3 and 11 in the reaction
medium was ascertained by recording the 1H coupled 31P spec-
trum followed by a simulation of the corresponding [ABC]2X
and [ABC]3X spin systems as previously. Then a selective irra-
diation of the two 31P signals allowed the assignment of the 1H
signals to each of the compounds 3 and 11. As for the couple
1 and 10, their 31P signals may also be identified from their
Fig. 2 31P NMR spectra of compounds 1 and 10 in CDCl3 , recorded
Scheme 2 Multistep synthesis of the di(2-thienyl)phosphinic amide 1.
without 1H broad-band irradiation.
T h i s j o u r n a l i s Q T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 4
N e w . J . C h e m . , 2 0 0 4 , 2 8 , 4 1 8 – 4 2 4
419

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values of 1JPC (139.2 Hz for 3 and 113.9 Hz for 11). No mono-
thiophenic compounds were observed in this reaction. One
may notice that the stoichiometry of 3 and 11 can be confirmed
by the integral ratios of the two compounds in the mixture: if
the concentration ratio [11]/[3] is found to be n in the 31P spec-
trum, it has to be 3n/2 in the 1H spectrum of the same sample.
Finally, the new hexa(3-thienyl)cyclotriphosphazene 4 was
obtained in 29% yield by the same procedure used for the
hexa(2-thienyl)cyclotriphosphazene 2 (Scheme 1).
by the strain due to the presence of three phosphole rings in
the same structure.
NMR spectroscopy
All compounds with only one phosphorus atom (i.e., 1, 3, 5,
7–11, 13–15) show simple H spectra that gave chemical shifts
1
and coupling constants using first-order analysis, except for
compound 3, which shows a ABMX system (see Table 2
below) because the signals of H-4 and H-5 are very close in
CDCl3 (Dn ¼ 5.5 Hz at 250.13 MHz).
Much more complex are the {1H}13C spectra of cyclotriphos-
phazenes when a symmetry exists in the three phosphorus spin
system,18–21 as in the case of compounds 2, 4 and 6. They show
second-order spectra from which, however, 31P–13C
coupling constants can be easily obtained.21 These parameters
are gathered in Table 1 with the 13C chemical shifts.
Synthesis of tri(3,30-bithienyl-2,20-ylene)cyclotriphosphazene (6)
Unfortunately, the preparation of the (3,30-bithienyl-2,20-yle-
ne)phosphinic amide 5 with the new short procedure described
in Scheme 3 was unsuccessful. Its synthesis required the
previous multistep method represented in Scheme 4.
From Table 1, one may observe that 1JPC is weakly affected
by a bridge between two gem thiophenic substituents (157.3 Hz
for freely rotating thiophenes in 2 versus 155.1 Hz for bridged
thiophenes in 6), whereas 2JPC shows at the same time the lar-
gest variation (12.5 Hz in 2 versus 24.1 Hz in 6). For the cor-
responding phosphinic amides (1 and 5) we find that the
Step 1. Dichloro-N,N-diethylphosphinic amide16 was
allowed to react with the 3,30-bithienyl-2,20-dilithium salt.17
The intermediate aminophosphine was not isolated but
directly oxidised to give the N,N-diethylphosphinic amide 13
in 45% isolated yield.
2
1
remark involving JPC is valid whereas the variation of JPC
is larger for the phosphinic amides 1 and 5 (154.0 and 142.8
Hz, respectively) than for the corresponding phosphazenes 2
and 6. In general, the cyclisation of phosphinic amides into
cyclotriphosphazenes induces, for the carbons not linked to
the phosphorus, a decrease of the chemical shifts and an
increase of the JPC coupling constant (Table 1).
Step 2. (3,30-Bithienyl-2,20-ylene)phosphinic acid 14 was
synthesised by stirring a mixture of phosphinic amide 13 and
12 N hydrochloric acid at 0 ꢀC during 15 min, then at 25 ꢀC
for 5 h.
The 1H spectra of the cyclotriphosphazenes 2, 4 and 6
are theoretically much more complex than the 13C spectra
because 1H is not a rare spin.21 Nevertheless, with the help
Step 3. The phosphinic acid 14 has been readily converted
into the phosphinic chloride 15 through reaction with phos-
phorus pentachloride (Scheme 4). The product 15 was not
isolated but directly used for the next step.
1
of homonuclear H selective irradiations and {31P}1H spectra,
all chemical shifts and coupling constants have been obtained
and are collected in Table 2 with those of the corresponding
phosphinic amides.
Step 4. It seemed convenient to prepare 5 by the previous
method (Scheme 2), which allowed us to synthesise the di(2-
It can be seen that the formation of the phosphazenic ring
from the phosphinic amide has a significative influence (þ0.4
Hz) on the coupling constants between the phosphorus and
the hydrogen atoms ‘‘ortho’’ to the phosphorus substituent
only, this kind of hydrogen being absent in compound 6. In
the same way, the coupling constants JHP of the cyclotriphos-
phazene 2 with free rotating groups are larger than those of the
cyclotriphosphazene 6 with rigid substituents. A larger relative
difference is observed for the coupling constant 4JHP , which is
reduced by 0.9 Hz (about 40%) from 2 to 6.
thienyl)phosphinic amide
1 from di(2-thienyl)phosphinic
chloride in biphasic diethyl ether and aqueous ammonia med-
ium. This method applied to the phosphinic chloride 15 did not
lead to the precipitation of the phosphinic amide 5. After eva-
poration of solvents under vacuum, only degradation products
were recovered. Actually, the expected phosphinic amide 5
was isolated in a correct yield (50%) by addition of 15 to an
anhydrous solution of gaseous ammonia in ether.
Finally, the tri(3,30-bithienyl-2,20-ylene)cyclotriphosphazene
6 has been obtained, as for cyclotriphosphazenes 2 and 4, by
cyclisation of the phosphinic amide 5 (Scheme 1).10,11 This
new cyclotriphosphazene 6 is the first to possess rigid hetero-
cyclic substituents. The very low yield (5%) may be explained
Due to the poor solubility of these products, all spectra were
not recorded in the same solvent, preventing any comparison
of their chemical shifts.
Table 1 13C NMR chemical shifts and JPC coupling constants (in
parentheses) of phosphinic amides 1, 3, 5 and cyclotriphosphazenes
2, 4, 6; 2-th ¼ 2-thienyl, 3-th ¼ 3-thienyl, bith ¼ 3,30-bithienyl-2,20-
ylene (numbering system in Scheme 1)
Compound
(solvent)
d(C-2)
d(C-3)
d(C-4) d(C-5)
(2-th)2P(O)NH2 134.20
136.57
(11.5)
134.44
128.36 133.80
1 (CDCl3) (154.0)
N3P3(2-th)6 140.03
2 (d6-DMSO) (157.3, 3.1, 3.1)
(16.0)
127.61 132.12
(6.5)
(6.0)
(12.5, 0.7, 0.7) (16.6)
(3-th)2P(O)NH2 134.86
135.20
(139.2)
140.31
129.30 127.35
(16.0) (16.8)
128.72 126.72
3 (CDCl3)
N3P3(3-th)6
4 (CDCl3)
(16.0)
132.47
(18.6, 2.0, 2.0)
132.08
(142.8)
(141.6, 2.5, 2.5) (17.9) (17.1)
bithP(O)NH2
5 (CDCl3)
N3P3bith3
147.53
(23.4)
146.81
(24.1)
120.55 136.84
(13.9) (5.9)
121.09 137.56
(14.1) (6.6)
Scheme 4 Synthesis of the (3,30-bithienyl-2,20-ylene)phosphinic
amide 5: (i) Et2NPCl2 , 0 ꢀC (M ¼ MgBr, Li); (ii) H2O2 (3%), 1 h,
10 ꢀC; (iii) 12 N HCl (17 equiv.), 15 min, 0 ꢀC; 5 h, 25 ꢀC; (iv) PCl5/
benzene, 1 h, 80 ꢀC; (v) NH3(g)/Et2O, 0 ꢀC.
134.56
6 (d6-DMSO) (155.1)
T h i s j o u r n a l i s Q T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 4
420
N e w . J . C h e m . , 2 0 0 4 , 2 8 , 4 1 8 – 4 2 4

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Table 2 1H NMR chemical shifts and JHH and JHP coupling
constants of phosphinic amides 1, 3, 5 and cyclotriphosphazenes 2,
4, 6 (numbering system in Scheme 1)
Compound 1
Solvent
2
CD3OD d6-DMSO CDCl3 CDCl3 CD3OD d6-DMSO
3
4
5
6
d(H-2)
d(H-3)
d(H-4)
d(H-5)
4J24
–
–
8.003 7.670
–
–
–
–
7.698
7.214
7.864
–
7.481
7.149
7.895
–
–
–
7.358
7.374 7.325 7.204
7.396 7.339 7.676
8.050
–
1.2
2.9
–
1.1
2.9
–
–
4J25
–
–
–
–
3J34
3.6
1.1
4.8
–
3.5
1.2
4.8
–
–
–
4J35
–
–
–
–
3J45
5.0
7.8
–
4.9
8.2
–
4.6
–
4.6
–
3J2P
3J3P
7.7
–
8.1
–
–
–
3J4P
3.8
–
4.3
–
–
–
4J4P
2.4
4.7
2.4
4.9
1.6
4.6
1.5
4.6
4J5P
2.5
2.1
Crystal structures of compounds 2, 4 and 6
The molecular structures of compounds 2, 4 and 6 consist of a
central six-membered ring of alternating nitrogen and phos-
phorus atoms with each phosphorus atom bonded to two thio-
phenic substituents for 2 and 4 and to a bithiophene unit for 6,
which has adopted the ‘‘paddlewheel’’ conformation common
to trispirocyclotriphosphazene compounds, with the cyclotri-
phosphazene and bithienyl heterocycles in nearly orthogonal
planes.10,22 The molecular structure of 2, 4 and 6 are depicted
in Fig. 3.
The nitrogen–phosphorus bond lengths in 2, 4 and 6 are
˚
approximately equivalent with a mean value of 1.597 A. The
N–P–N bond angles within the N3P3 ring are approximately
equal with a mean value of 117.4ꢀ for 2 and 4 and 116.1ꢀ for
6. The P–N–P bond angles have a mean value of 121.5ꢀ,
121.7ꢀ and 122.0ꢀ, respectively. The phosphorus–carbon bond
˚
lengths are all very similar with a mean value of 1.785 A for 2,
˚
˚
1.791 A for 4 and 1.798 A for 6. The largest difference existing
between these two kinds of compounds (2 and 4 versus 6) lies in
the C–P–C mean angle values, which are equal to 107.9ꢀ for 2,
103.8ꢀ for 4, and 89.2ꢀ for 6.
The influence of spiro substituents on the C–P–C angles was
also reported in an earlier work for hexaphenylcyclotriphos-
phazene (16) and trispiro(biphenyl)cyclotriphosphazene
(17).10 It was shown that the size of the C–P–C angles is smal-
ler in compound 17 (91.7ꢀ) than in 16 (103.8ꢀ), as is observed
for products 6 and 2. It can be seen also that the C–P–C angles
in the spiro compound 6 are smaller than in 17 with biphenyl
substituents. These values of the C–P–C angles reflect the
strong steric constraint existing in the spiro cyclotriphospha-
zenes 6 and 17. This observation may explain the reported
difficulties in synthesising these two compounds.
As for compound 17, the crystal arrangement of 6 shows
the presence of tunnels (Fig. 4) resulting from the stacking of
individual molecules along their C3 symmetry axis. This
phenomenon, which allows clathrate formation,23 is com-
monly observed in spirocyclotriphosphazenes24,25 and has
permitted the use of these compounds to trap selectively some
molecules.22,25,26
Fig. 3 Molecular structure of compounds 2, 4 and 6.
the bridged molecules. These compounds, which are the first
cyclotriphosphazenes with heteroaryl substituents linked to
the P3N3 skeleton by P–C bonds, are stable and will be soon
tested in coordination chemistry with the aim to obtain
stacked structures such as these sketched in Fig. 1. It is worthy
of note that among the cyclotriphosphazenes obtained, com-
pound 6 is particularly promising thanks to the arrangement
of the six potentially coordinating sulfur atoms around its C3
symmetry axis.
Conclusions
In this work we have synthesised three new cyclotriphospha-
zenes bearing free rotating or bridged thiophenic substituents.
1
Their H and 13C NMR spectra have been analysed and com-
pared to those of the corresponding phosphinic amides. The
recorded X-ray crystal structures reveal a steric constraint in
T h i s j o u r n a l i s Q T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 4
N e w . J . C h e m . , 2 0 0 4 , 2 8 , 4 1 8 – 4 2 4
421

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2
3
3.9, CH3), 39.27 (d, JPC ¼ 4.3, CH2), 128.07 (d, JPC ¼ 15.3,
C-4), 133.46 (d, 3JPC ¼ 5.7, C-5), 134.27 (d, 1JPC ¼ 149.1, C-2),
136.52 (d, 2JPC ¼ 11.0, C-3). 31P NMR (CDCl3): d ¼ 16.8.
Di(2-thienyl)phosphinic acid (8). Phosphinic amide (7; 35.0
mmol) was added to hydrochloric acid (12 N, 0.34 mol, 28
mL) and heated at 80ꢀ for 20 min. After cooling the crude pro-
duct was filtered off and the solid washed with water and dried
under vacuum with P2O5 . Yield 98%. M.p. 190 ꢀC (lit.29
192 ꢀC). MS (EI): m/z ¼ 230 [M]þ. 1H NMR (CD3OD):
d ¼ 7.20 (ddd, 3JHH ¼ 4.8, 3JHH ¼ 3.6, 4JHP ¼ 2.5, H-4), 7.61
3
4
3
(ddd, JHH ¼ 3.6, JHH ¼ 1.1, JHP ¼ 7.9, H-3), 7.84 (ddd,
4JHH ¼ 1.1, JHH ¼ 4.8, JHP ¼ 5.0, H-5). 13C NMR
3
4
3
(CD3OD): d ¼ 128.92 (d, JPC ¼ 16.3, C-4), 134.41 (d,
3JPC ¼ 6.5, C-5), 135.08 (d, JPC ¼ 163.9, C-2), 136.39 (d,
1
2JPC ¼ 12.2, C-3). 31P NMR (CD3OD): d ¼ 14.3.
Di(2-thienyl)phosphinic amide (1). An equimolar solution of
di(2-thienyl)phosphinic acid (8; 20.6 mmol) and phosphorus
pentachloride in benzene (30 mL) was heated to 80 ꢀC during
1 h before removal of the solvent and trichlorophosphine oxide
by distillation. The di(2-thienyl)phosphinic chloride 9 is nor-
mally not isolated but is used directly in the next step without
further purification. However, the first time the reaction was
made, this chloride was isolated and characterised. Yield
Fig. 4 The crystal packing of 6ꢃCHCl3 viewed down the b axis of
the unit cell. The cavity defined by layers of the 4-molecule motif of
6, shown here as an upper layer and a lower layer, encloses two
chloroform solvate molecules.
Experimental
3
100%. 1H NMR (CDCl3): d ¼ 7.22 (ddd, JHH ¼ 4.8,
General remarks
4
3
4
3JHH ¼ 3.7, JHP ¼ 2.9, H-4), 7.59 (ddd, JHH ¼ 3.7, JHH
¼
3
4
3
All reactions were carried out with careful exclusion of moist-
ure and air. The THF and diethylether used were dried with
sodium/benzophenone and freshly distilled prior to use.
The 1H, 13C and 31P NMR spectra were recorded on Bruker
AC-200, Avance-250 and Avance-400 spectrometers working
at 200.130, 250.130 and 400.130 MHz, respectively. The chemi-
cal shifts (in ppm) were referenced to internal TMS for 1H and
13C, using the substitution method,27 or to external 85%
H3PO4 for 31P, and the coupling constants are expressed in
Hz. For coupling constant measurements, zero-filling was
applied to FID recorded with TD and SW chosen to give digi-
tal resolutions below 0.1 Hz per point. Quantitative 31P spectra
have been recorded using the following conditions: no 1H
broad-band irradiation to suppress the nuclear Overhauser
effect and 30ꢀ pulse angles with which it has been verified that
relaxation delays D1 longer than 5 s are not needed, owing to
the relaxation times below 10 s28 for the studied compounds in
undegassed solutions.
1.2, JHP ¼ 7.6, H-3), 7.68 (ddd, JHH ¼ 1.2, JHH ¼ 4.8,
4JHP ¼ 4.7, H-5). 13C NMR (CDCl3): d ¼ 128.48 (d,
3JPC ¼ 18.2, C-4), 134.29 (d, JPC ¼ 151.2, C-2), 135.33 (d,
1
3JPC ¼ 7.4, C-5), 137.12 (d, JPC ¼ 13.4, C-3). 31P NMR
2
(CDCl3): d ¼ 23.8.
9 was dissolved in chloroform (23 mL) and added under
nitrogen to a mixture of diethyl ether (150 mL) and aqueous
ammonia (28%, 150 mL) cooled to 0 ꢀC, then the mixture
was stirred at 25 ꢀC during 1 h. The resulting precipitate was
filtered off (solid A). The two phases of the filtrate were sepa-
rated; the aqueous phase was saturated with NaCl and
extracted with chloroform (3 ꢂ 100 mL). The organic phases
were dried (Na2CO3) and the solvent removed under reduced
pressure (solid B). The solids A and B were collected and
extracted with a Soxhlet apparatus using chloroform as solvent
to give 1. Yield 65%. M.p. (CHCl3) 163 ꢀC. MS (EI):
1
m/z ¼ 229 [M]þ. H NMR: see Table 2. 13C NMR: see Table
1. 31P NMR (CDCl3): d ¼ 10.39. C8H8NOPS2 (229.3) calcd C
Mass spectra were recorded using a JEOL JMS-DX 300
spectrometer at the Laboratoire de Mesures Physiques (Uni-
41.91, H 3.51, N 6.11; found C 41.90, H 3.70, N 6.10.
´
versite Montpellier 2). The elemental analyses were carried
Synthesis of phosphinic amides 1 and 3 (procedure 2)
out by the Laboratoire Central de Microanalyse du CNRS
(Lyon) and the X-ray analyses of compounds 2 and 4 at the
Laboratoire de Chimie de Coordination (LCC) (Toulouse).
This procedure was used to synthesise the phosphinic amides 1
and 3. A solution of 2- or 3-thienyl magnesium bromide13 (26.0
mmol) in dry THF (40 mL) was added slowly to a solution,
cooled to ꢁ20 ꢀC, containing trichlorophosphine oxide (13.0
mmol) in THF (40 mL). At the end of the addition, the tem-
perature of the mixture was allowed to return to 25 ꢀC. The
solution was stirred during 1 h then added, under nitrogen,
to a mixture of diethyl ether (200 mL) and aqueous ammonia
(28%, 200 mL), cooled to 0 ꢀC, and left 1 h at this temperature
before rewarming to room temperature. The two phases were
separated and the aqueous phase was extracted with chloro-
form (3 ꢂ 100 mL). The organic phases were dried (MgSO4)
and the solvent evaporated off. The solid was purified by chro-
matography to give the phosphinic amide 1 or 3 (yield 18% for
both) and the corresponding phosphine oxide 10 or 11 (yields
of 22 and 14%, respectively).14,15
Synthesis of phosphinic amide 1 (procedure 1)
N,N-Diethyl-di(2-thienyl)phosphinic amide (7). A solution of
dichloro-N,N-diethylphosphinic amide (59.4 mmol)12 in dry
THF (10 mL) was added slowly at 21 ꢀC to a solution of 2-thie-
nyl magnesium bromide (136.0 mmol)13 in THF (160 mL). The
reaction mixture was heated at 66 ꢀC for 3 h before cooling to
0 ꢀC and hydrolysis (55 mL of water). The two phases were
separated and the aqueous phase was extracted with chloro-
form (3 ꢂ 55 mL). The organic phases were dried (MgSO4),
concentrated and the solid recrystallised from acetone. Yield
66%. M.p. (acetone) 122 ꢀC (lit.29 122–124 ꢀC). MS: m/z ¼
285 [M]þ. 1H NMR (CDCl3):d ¼ 1.12(t, 3JHH ¼ 7.1, CH3), 3.14
3
3
3
(qd, JHH ¼ 7.1, JHP ¼ 11.5, CH2), 7.15 (ddd, JHH ¼ 4.7,
3JHH ¼ 3.6, JHP ¼ 2.2, H-4), 7.63 (ddd, JHH ¼ 3.6, JHH
¼
Di(3-thienyl)phosphinic amide (3). Rf (alumina, CH2Cl2–
AcOEt 8:2) ¼ 0.06. M.p. 174 ꢀC. MS (FABþ): m/z ¼ 230
[M þ H]þ. 1H NMR: see Table 2. 13C NMR: see Table 1.
4
3
4
3
4
3
1.1, JHP ¼ 7.6, H-3), 7.68 (ddd, JHH ¼ 1.1, JHH ¼ 4.7,
4JHP ¼ 4.7, H-5). 13C NMR (CDCl3): d ¼ 14.11 (d, 3JPC ¼ 3.9,
T h i s j o u r n a l i s Q T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 4
422
N e w . J . C h e m . , 2 0 0 4 , 2 8 , 4 1 8 – 4 2 4

View Article Online
31P NMR (CDCl3): d ¼ 12.39. C8H8NOPS2 (229.25) calcd C
(3,30-Bithienyl-2,20-ylene)phosphinic amide (5). 15 (2.2 mmol)
was dissolved in chloroform (15 mL) and added over 5 min to
a saturated solution of ammonia in diethyl ether (100 mL)
cooled to 0 ꢀC. The solvent was removed under reduced pres-
sure at 25 ꢀC to give a white solid, which was washed with
hot chloroform and filtered. The filtrate was concentrated,
then recrystallised from chloroform–hexane (5–95%). Yield
41.91, H 3.52, N 6.11; found C 41.74, H 3.51, N 6.14.
Tri(2-thienyl)phosphine oxide (10)14,15. Rf (alumina, CH2Cl2–
hexane 8:2) ¼ 0.2. MS (FABþ): m/z ¼ 297 [M þ 1]þ. 1H
3
3
NMR (CDCl3): d ¼ 7.23 (ddd, JHH ¼ 3.6, JHH ¼ 4.6,
3
4
3
4JHP ¼ 2.0, H-4), 7.62 (ddd, JHH ¼ 3.6, JHH ¼ 1.2, JHP
¼
1
50%. M.p. 180 ꢀC. MS (EI): m/z ¼ 227 [M]þ. H NMR: see
4
3
4
8.0, H-3), 7.79 (td, JHH ¼ 1.2, JHH ¼ 4.6, JHP ¼ 4.6,
Table 2. 13C NMR: see Table 1. 31P NMR (CDCl3):
d ¼ 19.0. C8H6NOPS2 (227.24) calcd C 42.24, H 2.63, N
6.14, S 28.10; found C 42.1, H 2.6, N 6.0, S 28.0.
H-5). 13C NMR (CDCl3): d ¼ 128.27 (d, JPC ¼ 15.2, C-4),
3
3
1
134.26 (d, JPC ¼ 5.9, C-5), 134.54 (d, JPC ¼ 127.9, C-2),
136.81 (d, JPC ¼ 11.4, C-3). 31P NMR (CDCl3): d ¼ 7.83.
2
Formation of the phosphazenic ring
Tri(3-thienyl)phosphine oxide (11)14,15. Rf (alumina, CH2Cl2–
AcOEt 8:2) ¼ 0.41, MS (FABþ): m/z ¼ 297 [M þ 1]þ. 1H
This general procedure was used to synthesise hexa(2-thienyl)-
cyclotriphosphazene (2), hexa(3-thienyl)cyclotriphosphazene
(4) and tri(3,30-bithienyl-2,20-ylene)cyclotriphosphazene (6).
Triphenylphosphine (10 mmol), phosphinic amide (8.3 mmol),
triethylamine (8.3 mmol) and carbon tetrachloride (8.3 mmol)
were heated at reflux from methylene chloride (40 mL) for 5 h
(higher yields were not obtained by increasing the reaction
time). The solvent was removed under vacuum to give a
powder, which was purified by chromatography to give the
cyclotriphosphazene.
3
4
NMR (CDCl3): d ¼ 7.27 (ddd, JHH ¼ 5.0, JHH ¼ 1.2,
3
4
4
3JHP ¼ 4.0, H-4), 7.475 (ddd, JHH ¼ 5.0, JHH ¼ 2.8, JHP
¼
4
4
3
2.2, H-5), 7.81 (ddd, JHH ¼ 1.2, JHH ¼ 2.8, JHP ¼ 7.9,
H-2), 13C NMR (CDCl3): d ¼ 128.27 (d, JPC ¼ 16.1, C-4),
2
3
2
134.26 (d, JPC ¼ 15.7, C-5), 134.54 (d, JPC ¼ 15.4, C-2),
136.81 (d, JPC ¼ 113.9, C-3). 31P NMR (CDCl3): d ¼ 9.96.
1
Synthesis of phosphinic amide 5
N,N-Diethyl(3,30-bithienyl-2,20-ylene)phosphinic amide (13).
Dichloro-N,N-diethylphosphinic amide (3.1 mmol)16 dissolved
in diethyl ether (5 mL) was added over 40 min to a solution of
2,20-dilithio-3,30-bithienyl (3.1 mmol)17 cooled to 10 ꢀC. The
mixture was stirred 1 h, then treated with 3% hydrogen perox-
ide (7 mL) and stirred again for 1 h at 10 ꢀC. The organic layer
was washed with an aqueous saturated solution of NaCl, dried
(MgSO4) and filtered. The solvent was removed under reduced
pressure and purified by chromatography to give 13. Yield
45%. Rf ¼ 0.3 (silica gel, 1:1 CH2Cl2–Et2O). M.p. 138 ꢀC.
MS (EI): m/z ¼ 283 [M]þ. 1H NMR (CDCl3): d ¼ 1.09 (q,
3JHH ¼ 7.1, 4JHP ¼ 7.1, CH3), 3.09 (td, 3JHH ¼ 7.1,
Hexa(2-thienyl)cyclotriphosphazene (2). Yield 34%. M.p.
269 ꢀC. Rf ¼ 0.5 (silica gel, CH2Cl2). MS (EI): m/z ¼ 633
[M]þ. 1H NMR: see Table 2. 13C NMR: see Table 1. 31P
NMR (CDCl3): d ¼ 3.21. C24H18N3P3S6 (633.74) calcd C
45.44, H 2.84, N 6.63; found C 45.80, H 3.40, N 6.70.
Hexa(3-thienyl)cyclotriphosphazene (4). Yield 2þ9%. M.p.
250 ꢀC. Rf ¼ 0.38 (silica gel, CH2Cl2). MS (FAB ): m/z ¼
1
634 [M þ 1]þ. H NMR: see Table 2. 13C NMR: see Table 1.
31P NMR (CDCl3): d ¼ 4.59. C24H18N3P3S6 (633.74) calcd C
45.44, H 2.84, N 6.63; found C 45.33, H 2.85, N 6.70.
3
4
3JHP ¼ 12.5, CH2), 7.09 (dd, JHH ¼ 4.6, JHP ¼ 1.7, H-4),
3
4
7.65 (dd, JHH ¼ 4.6, JHP ¼ 4.9, H-5). 13C NMR (CDCl3):
Tri(3,30-bithienyl-2,20-ylene)cyclotriphosphazene (6). Yield
5%. M.p. 278 ꢀC. Rf ¼ 0.4 (silica gel, CH2Cl2). MS (EI): m/z ¼
3
2
d ¼ 13.89 (d, JPC ¼ 2.9, CH3), 38.36 (d, JPC ¼ 5.4, CH2),
3
1
1
627 [M]þ. H NMR: see Table 2. 13C NMR: see Table 1. 31P
120.59 (d, JPC ¼ 13.6, C-4), 131.23 (d, JPC ¼ 139.2, C-2),
3
2
136.70 (d, JPC ¼ 5.6, C-5), 148.09 (d, JPC ¼ 22.0, C-3). 31P
NMR (CDCl3): d ¼ 22.8. C12H14NOPS2 (283.35) calcd C
50.82; H 4.94; N 4.94; S 22.5; found C 50.80, H 5.10, N 4.9,
S 22.60.
NMR (CDCl3): d ¼ 13.6. C24H12N3P3S6ꢃCHCl3 (753.14)
calcd C 40.18, H 1.74, N 5.62; S 25.72; found C 40.5, H
1.5, N 5.5, S 25.3.
X-Ray crystallographic studyy of cyclotriphosphazenes 2, 4 and 6
(3,30-Bithienyl-2,20-ylene)phosphinic acid (14). Hydrochloric
acid (12 N; 12 mmol, 1 mL) was added to 13 (0.7 mmol) cooled
to 0 ꢀC. The viscous mixture obtained was allowed to reach
25 ꢀC. After 5 h, crystalline solid 14 was filtered off and washed
with water before drying under vaþcuum. Yield 100%. M.p.
152 ꢀC. MS (EI): m/z ¼ 228 [M] . 1H NMR (CD3OD):
For 2 and 4, data were collected on a Stoe IPDS diffract-
ometer. The final unit cell parameters were obtained by the
least-squares refinement of 5000 or 8000 reflections. Only sta-
tistical fluctuations were observed in the intensity monitors
over the course of the data collections. The structures were
solved by direct methods (SIR97)30 and refined by least-
squares procedures on F 2. All H atoms attached were intro-
duced in the calculations in idealised positions [d(CH) ¼ 0.96
3
4
d ¼ 7.29 (dd, JHH ¼ 4.6, JHP ¼ 1.9, H-4), 7.88 (dd,
3JHH ¼ 4.6, 4JHP ¼ 5.2, H-5). 13C NMR (CD3OD):
3
1
d ¼ 121.95 (d, JPC ¼ 14.6, C-4), 131.25 (d, JPC ¼ 154.8, C-
˚
A] and treated as riding models with isotropic thermal para-
3
2
2), 138.14 (d, JPC ¼ 6.1, C-5), 148.79 (d, JPC ¼ 24.8, C-3).
31P NMR (CD3OD): d ¼ 21.8. C8H5O2PS2 (228.23) calcd C
42.10, H 2.19; found C 42.30, H 2.90.
meters 20% higher than those of the carbon to which they
are attached. In both compounds, some of the thiophene rings
present a disordered arrangement with the positions on the
ring occupied partially by S and C atoms. These disordered
molecules were treated using the available restraints (SAME,
SADI and FLAT) in SHELXL-97.31 Least-squares refine-
ments were carried out by minimising the function
Sw(F2o ꢁ F2c)2, where Fo and Fc are the observed and calcu-
lated structure factors. The weighting scheme used in the last
refinement cycles was w ¼ 1/[s2(Fo2) þ (aP)2 þ bP] where
P ¼ (F2o þ 2F2c)/3. Models reached convergence with
(3,30-Bithienyl-2,20-ylene)phosphinic chloride (15). 14 (0.45
mmol) and phosphorus pentachloride (0.45 mmol) dissolved
in benzene (3 mL) were heated to reflux for 1 h. The solvent
and phosphorus oxychloride were removed by distillation to
give yellow solid 15. Yield 92%. MS (EI): m/z ¼ 246 (61%)
[M]þ, 248 (27%) [M þ 2]þ. 1H NMR (CDCl3): d ¼ 7.16 (dd,
4
3
4
3JHH ¼ 4.5, JHP ¼ 2.5, H-4), 7.79 (dd, JHH ¼ 4.5, JHP
¼
6.1, H-5). 13C NMR (CDCl3): d ¼ 120.66 (d, JPC ¼ 16.0,
3
1
3
C-4), 130.79 (d, JPC ¼ 148.5, C-2), 138.95 (d, JPC ¼ 7.3,
y CCDC reference numbers 184619 (2), 184574 (4) and 204454 (6). See
http://www.rsc.org/suppdata/nj/b3/b311046j/ for crystallographic
data in .cif or other electronic format.
C-5), 147.26 (d, JPC ¼ 27.3, C-3). 31P NMR (CDCl3):
2
d ¼ 22.6.
T h i s j o u r n a l i s Q T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 4
N e w . J . C h e m . , 2 0 0 4 , 2 8 , 4 1 8 – 4 2 4
423

View Article Online
References
Table 3 Crystal data and structure refinement details for 2, 4 and 6
1
2
H. R. Allcock, Acc. Chem. Res., 1979, 12, 351.
R. H. Neilson, R. Haini, P. Wisian-Neilson, J.-J. Meister, A. K.
2
4ꢃCHCl3
6ꢃCHCl3
Roy and G. L. Hagnauer, Macromolecules, 1987, 20, 910.
C. T. Laurencin, M. E. Norman, H. M. Elgendy, S. F. El-Amin,
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M. H. Rosset, Ac. Sci., 1925, 180, 750.
T. Moeller and F. Tsang, Chem. Ind., 1962, 24, 361.
M. Biddlestone and R. A. Shaw, Phosphorus, 1973, 3, 95.
Empirical
formula
Formula
weight
C24 H18
C25 H19Cl3
N3 P3 S6
753.14
C25H13Cl3
N3P3S6
747.09
3
N3 P3 S6
633.74
4
5
T/K
Crystal
160(2)
Monoclinic
180(2)
Orthorhombic
293(2)
Monoclinic
6
system
Space group
P21
Pnma
I2/a
7
8
9
˚
a/A
11.2770(16)
9.1335(10)
13.561(2)
101.04
1370.9(3)
2
9.828(2)
15.632(3)
20.084(4)
90
19.420(2)
15.7094(16)
20.428(4)
96.673(7)
6190.0(14)
8
˚
b/A
˚
c/A
´
10 C. Combes-Chamalet, H.-J. Cristau, M. McPartlin, F. Plenat, I. J.
Scowen and T. M. Woodroffe, J. Chem. Soc., Perkin Trans. 2,
1997, 15.
b/ꢀ
U/A
3
˚
3085.5(11)
4
0.883
11 R. Appel and H. Einig, Chem. Ber., 1975, 108, 914.
12 R. F. Borch and R. R. Valente, J. Med. Chem., 1991, 34,
3052.
13 Y. Goldberg, R. Sturkovich and E. Lukevics, Synth. Commun.,
1993, 23, 1235.
14 H. J. Jakobsen and J. A. Nielsen, J. Mol. Spectrosc., 1969,
31, 230.
15 H. J. Jakobsen and J. A. Nielsen, J. Mol. Spectrosc., 1970,
33, 474.
16 J. W. Perich and R. B. Johns, Synthesis, 1988, 142.
17 T. Kauffmann, B. Greving, R. Kriegesmann, A. Mitschker and
A. Woltermann, Chem. Ber., 1978, 111, 1330.
18 R. K. Harris and E. G. Finer, Bull. Soc. Chim. Fr., 1968,
2805.
Z
m/mmꢁ1
Reflections
collected
0.696
13 519
0.88
6293
14 257
Independent
reflections
Rint
5198
2472
5446
0.0250
0.0268
0.0712
0.0284
0.0721
0.0512
0.0407
0.1031
0.0479
0.1078
0.0346
0.0593
0.1099
0.1220
0.1338
R1 [I > 2s(I)]
wR2 [I > 2s(I)]
R1 (all data)
wR2 (all data)
19 J. Reuben, Magn. Reson. Chem., 1987, 25, 1049.
20 W. F. Deutsch, H. G. Parkes and R. A. Shaw, Magn. Reson.
Chem., 1989, 27, 207.
21 V. Vicente, A. Fruchier and H. J. Cristau, Magn. Reson. Chem.,
2003, 41, 183.
22 C. Combes-Chamalet, Ph.D. Thesis, University of Montpellier,
Montpellier, France, 1996.
23 C. Combes, H. J. Cristau, W. S. Li, M. McPartlin, F. Plenat and
I. J. Scowen, J. Chem. Res., (S), 1994, 134.
24 H. R. Allcock and L. A. Siegel, J. Am. Chem. Soc., 1964, 86,
5140.
25 A. P. Primrose, M. Parvez and H. R. Allcock, Macromolecules,
1997, 30, 670.
26 H. R. Allcock, A. P. Primrose, N. E. Silverberg, K. B. Visscher,
A. L. Rheingold, A. I. Guzei and M. Parvez, Chem. Mater.,
2000, 12, 2530.
27 R. K. Harris, E. D. Becker, S. M. Cabral de Menezes, R.
Goodfellow and P. Granger, Magn. Reson. Chem., 2002,
40, 489.
28 V. Vicente, Ph.D. Thesis, University of Montpellier, Montpellier,
France, 2002.
R1 ¼ S(kFo| ꢁ |Fck)/S(|Fo|)
and
wR2 ¼ {Sw(F 2o ꢁ F c2)2/
Sw(F 2o)2}1/2 having the values listed in Table 3. The
calculations were carried out with the SHELXL-97 program
using the integrated system WINGX(1.63).32 Molecular views
were realised with the help of ORTEP-3 for Windows (Version
1.076).33
For 6 data were collected on a colourless crystal of 6ꢃCHCl3
on a Siemens P4 four-circle diffractometer using Mo-Ka radia-
tion. The structure was solved by direct methods (SHELXTL)
and from this and subsequent difference Fourier maps the posi-
tions of all the non-hydrogen atoms were located. Extended
areas of electron density associated with the chloroform sol-
vate molecules arising from rotational disorder of the chlorine
atoms around the C–H axis of the molecule were modelled as
two components in a population ratio of 60:40. Hydrogen
atoms were placed in idealised positions with UH ¼ 1.2 Ueq
of the parent carbon. In the final cycles of full-matrix least-
squares refinement on F2, anisotropic thermal parameters were
assigned to non-hydrogen atoms of the asymmetric unit.
29 C. N. Lieske, J. H. Clark, H. G. Meyer, L. Boldt, M. D. Green,
J. R. Lowe, W. E. Sultan, P. Blumberg and M. A. Priest, Pestic.
Biochem. Physiol., 1984, 22, 285.
30 A. Altomare, M. C. Burla, M. Camalli, G. L. Cascarano, C.
Giacovazzo, A. Guagliardi, A. G. G. Moliterni, G. Polidori and
R. Spagn, J. Appl. Crystallogr., 1999, 32, 115.
31 G. M. Sheldrick, SHELXL-97, Program for refinement of crystal
structures, University of Go¨ttingen, Germany, 1997.
32 L. J. Farrugia, J. Appl. Crystallogr., 1999, 32, 837.
33 L. J. Farrugia, J. Appl. Crystallogr., 1997, 30, 565.
Acknowledgements
We thank Dr. Jean-Claude Daran (LCC, Toulouse) for his
help in recording some of the crystallographic data (com-
pounds 2 and 4).
T h i s j o u r n a l i s Q T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 4
424
N e w . J . C h e m . , 2 0 0 4 , 2 8 , 4 1 8 – 4 2 4