The first structurally characterised cyclotriphosphazene substituted with a sulfonamide nitrogen

Article abstract of DOI:10.1016/j.inoche.2007.05.014

The reaction between two equivalents of N-(2-hydroxyphenyl)-p-toluenesulfonamide (H₂sulf) and [N₃P₃(biph)₂Cl₂] (H₂biph = 2,2′-biphenol) produces the compound bis(2,2′-biphenylato)bis(2-oxyphenyl)-p-toluenesulfonamide cyclotriphosphazene (H₂L) containing two geminal Hsulf moieties. Further reaction of H₂L in basic conditions results in the removal of the sulfonamide arm and the slow formation of a novel phosphazene containing the spirocyclic sulf moiety. When this occurs in the presence of [Pd(bpy)Cl₂] the reaction is facile and the new complex [Pd(bpy)(sulf)] (2) is also formed. Compounds H₂L, 1 and 2 have all been characterised by single crystal X-ray crystallography.

Full text of DOI:10.1016/j.inoche.2007.05.014

Inorganic Chemistry Communications 10 (2007) 1005–1008
www.elsevier.com/locate/inoche
The first structurally characterised cyclotriphosphazene substituted
with a sulfonamide nitrogen
*
*
Eric W. Ainscough , Andrew M. Brodie , Ross J. Davidson, Carl A. Otter
Chemistry – Institute of Fundamental Sciences, Massey University, Private Bag 11 222, Palmerston North, New Zealand
Received 17 April 2007; accepted 15 May 2007
Available online 26 May 2007
Abstract
The reaction between two equivalents of N-(2-hydroxyphenyl)-p-toluenesulfonamide (H2sulf) and [N3P3(biph)2Cl2] (H2biph = 2,20-
biphenol) produces the compound bis(2,20-biphenylato)bis(2-oxyphenyl)-p-toluenesulfonamide cyclotriphosphazene (H2L) containing
two geminal Hsulf moieties. Further reaction of H2L in basic conditions results in the removal of the sulfonamide arm and the slow
formation of a novel phosphazene containing the spirocyclic sulf moiety. When this occurs in the presence of [Pd(bpy)Cl2] the reaction
is facile and the new complex [Pd(bpy)(sulf)] (2) is also formed. Compounds H2L, 1 and 2 have all been characterised by single crystal
X-ray crystallography.
Ó 2007 Elsevier B.V. All rights reserved.
Keywords: Cyclotriphosphazene; N-(2-hydroxyphenyl)-p-toluenesulfonamide; Palladium; 2,20-Bipyridine; X-ray structure
As part of our program to investigate the coordination
chemistry of ligands bound to the cyclotriphosphazene
core [1–6], we have examined the reactivity of a potentially
dianionic ligand, H2L, which contains a bis-sulfonamide
donor set (see Scheme 1). In this communication, we report
that when H2L reacts with [Pd(bpy)Cl2] in the presence of
triethylamine (NEt3) in an attempt to prepare the complex
[Pd(bpy)L], an unexpected reaction occurs in which a sul-
fonamide moiety is lost from H2L to afford a new spirocy-
clic phosphazene, [N3P3(biph)2(sulf)] (1). Although
substitution on the phosphorus atoms of cyclotriphosphaz-
enes has been performed using numerous different nucleo-
philes, compound 1 represents the first structurally
characterised example in which a ring phosphorus atom
has been substituted by the nitrogen atom of a sulfonamide
moiety.
quent reaction of H2L with [Pd(bpy)Cl2] using NEt3 as
base, results in the removal of a sulfonamide arm from
H2L, forming the new spirocyclic phosphazene 1 and com-
pound 2 (Scheme 1). Compound 2 was also prepared from
the reaction between [Pd(bpy)Cl2] and H2sulf and charac-
terised by X-ray crystallography.
The IR spectrum (KBr disk) of H2L shows bands at
1123 and 1175 cmꢀ1 assigned to the PN ring stretching
modes. Similar strong bands are observed in the spectrum
of 1 at 1232, 1224, 1201 and 1192 cmꢀ1 for PN stretches.
The SO2 stretches are tentatively assigned to bands at
1158 and 1160 cmꢀ1 for H2L and 1, respectively. The SO2
stretch in H2sulf occurs at 1155 cmꢀ1 and this moves to
1139 cmꢀ1 in the complex 2, which is consistent with
deprotonated sulfonamide nitrogen binding and has been
observed in other complexes containing sulfonamide
ligands [8].
Two equivalents of H2sulf and [N3P3(biph)2Cl2] react at
room temperature in acetone in the presence of Cs2CO3 as
base, to produce the new phosphazene, H2L [7]. The subse-
The X-ray structural data [9] obtained for H2L confirm
the double substitution of the chloride ions in [N3P3-
(biph)2Cl2] with sulfonamide moieties (Fig. 1). The com-
pound shows standard length P–N bonds in the phosphazene
*
Corresponding authors. Tel.: +64 6 3569099; fax: +64 6 3505682.
˚
ring, ranging between 1.557(7) and 1.591(7) A. The N–P–N
E-mail addresses: e.ainscough@massey.ac.nz (E.W. Ainscough),
angles [between 118.4(4) and 119.0(4)°] and P–N–P angles
a.brodie@massey.ac.nz (A.M. Brodie).
1387-7003/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.inoche.2007.05.014

1006
E.W. Ainscough et al. / Inorganic Chemistry Communications 10 (2007) 1005–1008
O
S
N
O
O
P
N
N
P
N
O
O
P
O
O
O
O
O
S
S
S
O
Cl
N
P
Cl
N
P
HO HN
O
P
N
O
[Pd(bpy)Cl2]
NEt3
NH
HN
Cs2CO3
O
O
O
1
O
O
N
P
O
CH2Cl2
P
N
Acetone
N
O
O
O
O
P
O
S
N
O
N
Pd
O
N
2
H2L
Scheme 1.
[between 122.2(5) and 120.4(4)°] are also in the normal range
adjacent molecules. Specifically, the donor–acceptor dis-
tances for the arrays N5–H5Nꢁ ꢁ ꢁO9# (symmetry opera-
tion: x + 1, y, z) and N4–H4Nꢁ ꢁ ꢁO12# (symmetry
and the rms standard deviation of the phosphazene ring
˚
atoms from their mean plane is 0.0403 A.
˚
The sulfonamide arms are orientated such that they fold
back above and below the plane of the phosphazene ring.
There are weak intramolecular H–p interactions between
H40 and H37 of different spirocyclic biphenyl rings and tol-
uene rings C7–C12 and C20–C25, respectively. This
arrangement of the arms exposes the NH sulfonamide pro-
tons which engage in intermolecular hydrogen bonding
interactions with sulfonamide oxygen atoms on different
operation: x ꢀ 1, y, z) are 3.044(9) and 2.884(9) A,
respectively.
The X-ray structure [10] of the phosphazene 1 is shown
in Fig. 2 and this compound represents the first structurally
characterised cyclotriphosphazene in which a ring phos-
phorus atom has been substituted with a sulfonamide
nitrogen. The geometries around the phosphazene ring
Fig. 1. Crystal structure of H2L with most of the hydrogen atoms
˚
removed for clarity. Selected bond lengths (A) and angles (°): P1–N1,
Fig. 2. Crystal structure of 1 with hydrogen atoms removed for clarity.
˚
1.571(7); P1–N2, 1.557(7); P2–N2, 1.578(7); P2–N3, 1.591(7); P3–N1,
1.579(7); P3–N3, 1.572(7); N4–S1, 1.642(7); N5–S2, 1.631(6); S1–O7,
1.426(6); S1–O8, 1.429(6); S2–O10, 1.426(6); S2–O9, 1.437(6); P1–N1–P2,
122.2(5); P1–N3–P3, 120.5(4); P2–N2–P3, 120.4(4); N1–P1–N3, 118.4(4);
N1–P2–N2, 118.5(4); N2–P3–N3, 119.0(4); N4–S1–O7, 104.6(4); N4–S1–
O8, 108.5(4); O7–S1–O8, 118.7(4); N5–S2–O10, 109.6(4); N5–S2–O9,
104.5(4); O9–S2–O10, 119.4(4).
Selected bond lengths (A) and angles (°): P1–N1, 1.585(4); P1–N2,
1.577(4); P2–N3, 1.578(4); P2–N2, 1.580(4); P3–N1, 1.581(4); P3–N3,
1.574(4); P1–N4, 1.708(4); P1–O1, 1.614(3); N4–S1, 1.641(4); S1–O2,
1.434(3); S1–O3, 1.434(3); P1–N2–P2, 121.8(2); P2–N3–P3, 121.8(2); P1–
N1–P3, 120.3(2); N1–P1–N2, 118.32(19); N2–P2–N3, 117.75(19); N1–P3–
N3, 117.85(19); O1–P1–N4, 93.18(17); N4–S1–O3, 108.8(2); N4–S1–O2,
104.06(19); O2–S1–O3, 119.3(2).

E.W. Ainscough et al. / Inorganic Chemistry Communications 10 (2007) 1005–1008
1007
are normal for cyclotriphosphazenes with P–N–P angles
between 120.3(2) and 121.9(2)° and N–P–N angles between
117.75(19) and 118.32(19)°. The phosphazene ring is essen-
tially planar with the mean deviation of the atoms from the
plex deviate somewhat from a regular square planar geome-
try, lying between 80.38(13) and 102.00(13)°. The largest
deviation is for the angle N3–Pd–N1 between pyridyl and
sulfonamide donors and may be due to the steric impediment
provided by the bulky sulfonamide moiety. The bite angle of
83.97(12)° for the sulf ligand is similar to that observed [14]
for catecholate dianion [85.6(1)°] in the complex
[Pd(bpy)(cat)].
˚
plane of the ring being 0.0508 A and the largest deviations
˚
are for P3 and N1, which lie 0.0929 A above and below the
plane. The P–N bond lengths in the ring range between
˚
1.574(4) and 1.585(4) A. The P–O1 bond length is
˚
1.614(3) A and similar to the P–O bond lengths reported
Since we had not observed 1 during the preparation of
H2L in acetone with Cs2CO3 as base, we conducted a series
of reactions to determine whether the compound was
accessible under other conditions. The reactions were mon-
itored by 31P NMR and a table of results is given in the
supplementary information. When Cs2CO3 is used with
only one equivalent of H2sulf (rather than two) over the
same period, the major product observed is still H2L and
this is present in a near 1:1 mixture with the unreacted
starting material and a trace amount of the spirocyclic
product 1. At room temperature in THF, the reactions
between one equivalent of H2sulf and [N3P3(biph)2Cl2] pro-
ceed slowly, there being little reaction after several days at
room temperature with the base, NaH, and none with
NEt3. Similar results are obtained at room temperature
when two equivalents of H2sulf are used in the reaction.
When the reactions are performed in THF at reflux
using NEt3 or NaH as a base H2L does form, however,
as the reactions are driven to completion, 1 also begins to
form and hence the reactions give a mixture of products.
If a solution containing H2L and NEt3 is allowed to stir
at room temperature then decomposition of H2L into 1 is
also observed. It seems likely that when the stronger bases,
NEt3 or NaH, are present, geminal substitution to form
H2L occurs initially followed by decomposition into the
spirocyclic 1 possibly according to Scheme 2. Hence
[Pd(bpy)Cl2] is not required for the decomposition of
H2L but appears to facilitate the process, presumably by
either forming an intermediate with a deprotonated form
of H2L or by removing the ejected sulf ligand from the
reaction mixture via complexation.
in [N3P3(cat)3] (H2cat = catechol) [11]. The P–N4 bond
length of 1.708(4) is typical for a P–N single bond and sim-
ilar to other P–Nsulfonamide bonds [12]. Where the O–P–O
angles for the spirocyclic 2,20-biphenylato moieties are
103.38(16) and 103.76(16)°, the O1–P–N4 angle formed
by the five membered ring of the spirocyclic sulf group is
expectedly smaller at 93.18(17)° and more closely resembles
the O–P–O angles in [N3P3(cat)3] which are 97.4(8)° [11].
The X-ray structure [13] of the palladium complex is
shown in Fig. 3. Some disorder exists in the crystals of the
molecule and the tosyl ring was modelled in two slightly dif-
ferent orientations with approximately 0.81:0.19 occupancy.
The Pd(II) centre has a distorted square planar geometry
comprised of a ‘N3O’ donor set. The Pd–N bonds are of sim-
˚
ilar length [between 2.006(3) and 2.022(3) A] with the Pd–O
˚
bond being slightly shorter at 1.984(3) A. The Pd–N bond
lengths are similar to those observed in a related palladium
complex containing a sulfonamide ligand [8] and the Pd–N
and Pd–O bond lengths are similar to those in [Pd(bpy)(cat)]
[14]. The bond angles between donor atoms within the com-
In conclusion, the sulfonamide H2sulf can react with
[N3P3(biph)2Cl2] in the presence of base to form either the
spirocyclic product 1 or the doubly substituted product
H2L. A preference for the doubly substituted product is
found when Cs2CO3 is used as a base in acetone or THF
but mixtures of both species are obtained when NaH or
B
O
O
S
O
S
H
O
O
N
S
NH
N
O
O
P
N
N
P
N
O
O
O
O
O
P
P
N
N
N
P
O
˚
Fig. 3. Crystal structure of 2. Selected bond lengths (A) and angles (°):
O
O
O
P
Pd1–O1, 1.984(3); Pd1–N1, 2.022(3); Pd1–N2, 2.006(3); Pd1–N3, 2.018(3);
N1–S1, 1.615(3); S1–O2, 1.444(3); S1–O3, 1.439(3); O1–Pd1–N1,
83.97(12); O1–Pd1–N2, 93.53(12); N2–Pd1–N3,80.38(13); N1–Pd1–N3,
102.00(13); O1–Pd1–N3, 172.88(11); N1–Pd1–N2, 176.93(13), O2–S1–N1,
107.89(16); O3–S1–N1, 110.68(17); O2–S1–O3, 116.90(17).
O
1
Scheme 2.

1008
E.W. Ainscough et al. / Inorganic Chemistry Communications 10 (2007) 1005–1008
[2] E.W. Ainscough, A.M. Brodie, C.V. Depree, B. Moubaraki, K.S.
Murray, C.A. Otter, Dalton Trans. (2005) 3337.
[3] E.W. Ainscough, A.M. Brodie, C.V. Depree, G.B. Jameson, C.A.
Otter, Inorg. Chem. 44 (2005) 7325.
[4] E.W. Ainscough, A.M. Brodie, C.V. Depree, C.A. Otter, Polyhedron
25 (2006) 2341.
[5] E.W. Ainscough, A.M. Brodie, A.B. Chaplin, J.M. O’Conner, C.A.
Otter, Dalton Trans. (2006) 1264.
NEt3 are used in THF. This observation would be consistent
with the weaker carbonate base being unlikely to deproto-
nate the sulfonamide nitrogen. When H2L is treated with
NEt3, the spirocyclic compound 1 may be formed slowly.
This process is accelerated in the presence of [Pd(bpy)Cl2]
in which case the new complex 2 is also formed.
[6] E.W. Ainscough, A.M. Brodie, G.B. Jameson, C.A. Otter, Polyhe-
dron 26 (2007) 460.
Acknowledgements
[7] See supplementary data for experimental conditions.
[8] C.A. Otter, S.M. Couchman, J.C. Jeffery, K.L.V. Mann, E. Psillakis,
M.D. Ward, Inorg. Chim. Acta 278 (1998) 178.
We acknowledge financial support, including a postdoc-
toral fellowship (to C.A.O.) from the RSNZ Marsden
Fund (MAU208) and a summer scholarship (to R.J.D.)
from the Massey University Research Fund. We thank
[9] Crystal refinement data for H2L: C50H40N5O10P3S2, Mr = 1027.90,
Monoclinic, P2(1)/n, a = 8.9340(6), b = 26.9133(19), c = 19.4925(14),
3
˚
b = 92.667(2), V = 4681.8(6) A , Z = 4,
qcalc = 1.458, T = 84(2),
the Otsuka Chemical Co. Ltd. for
hexachlorocyclotriphosphazene.
a
gift of
l = 0.283, independent reflections 6688, final R indices [I > 2r(I)]
are R1 = 0.0898, wR2 = 0.1508; R indices (all data), R1 = 0.2044,
wR2 = 0.1878 and the goodness of fit on F2 is 1.059.
[10] Crystal refinement data for 1.0.5C5H12
:
C39.5H33N4O7P3S,
Appendix A. Supplementary material
ꢀ
˚
˚
Mr = 800.70, triclinic, P1, a = 10.9621(3) A, b = 11.2188(3) A,
˚
c = 16.5503(4) A, a = 10.9621(3)°, b=11.2188(3) °, c=16.5503(4)°,
V = 1775.32(8) A , Z = 2, qcalc = 1.497, T = 84(2), l = 0.261, inde-
3
CCDC 635419, 635420, and 635421 contain the supple-
mentary crystallographic data for H2L, 1, and 2. These data
can be obtained free of charge via http://www.ccdc.cam.
ac.uk/conts/retrieving.html, or from the Cambridge Crys-
tallographic Data Centre, 12 Union Road, Cambridge
CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: depos-
it@ccdc.cam.ac.uk. Supplementary data associated with
this paper can be found, in the online version, at
doi:10.1016/j.inoche.2007.05.014.
˚
pendent reflections 6706, final R indices [I > 2r(I)] are R1 = 0.0714,
wR2 = 0.1365; R indices (all data), R1 = 0.1197, wR2 = 0.1549 and the
goodness of fit on F2 is 1.058.
[11] H.R. Allcock, R.W. Allen, E.C. Bissell, L.A. Smeltz, M. Teeter, J.
Am. Chem. Soc. 98 (1976) 5120.
[12] M. Szabo, D. Ban, C. Rat, A. Silvestru, J.E. Drake, M.B.
Hursthouse, M.E. Light, Inorg. Chim. Acta 357 (2004) 3595.
[13] Crystal refinement data for 2: CHCl3 Æ 0.5C5H12:C26.5H26Cl3N3O3PdS,
˚
˚
Mr = 679.36, Monoclinic, C2/c, a = 20.6821(8) A, b = 8.4112(3) A,
3
˚
˚
c = 31.9672 A, b=103.223(1)°, V = 5413.6(4) A , Z = 8, qcalc = 1.667,
T = 89(2), l = 1.094, independent reflections 4946, final R indices
References
[I > 2r(I)] are R1 = 0.0413, wR2 = 0.1016;
R indices (all data),
R1 = 0.0483, wR2 = 0.1052 and the goodness of fit on F2 is 0.903.
[14] N. Okabe, T. Aziyama, M. Odoko, Acta Cryst. Sect. E E61 (2005)
m1943.
[1] E.W. Ainscough, A.M. Brodie, C.V. Depree, J. Chem. Soc. Dalton
Trans. (1999) 4123.