Preparation and characterization of hexakis[2-methoxy-4-(2,3- dimethylphenylimino)phenylato]cyclotriphosphazene

Article abstract of DOI:10.1080/10426501003692078

Hexakis[2-methoxy-4-(2,3-dimethylphenylimino)phenylato]cyclotriphosphazene was prepared by the reaction of hexakis[2-methoxy-4-formylphenoxy] cyclotriphosphazene and 3,4-dimethylaniline. The structure of new cyclotriphosphazene derivative was determined by elemental analysis, IR, 1H NMR, 13C NMR spectra, thermal analysis, and X-ray diffraction. Supplemental materials are available for this article. Go to the publishers online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. Taylor & Francis Group, LLC.

Full text of DOI:10.1080/10426501003692078

Phosphorus, Sulfur, and Silicon, 185:2449–2454, 2010
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426501003692078
PREPARATION AND CHARACTERIZATION OF
HEXAKIS[2-METHOXY-4-(2,3-DIMETHYLPHENYLIMINO)
PHENYLATO]CYCLOTRIPHOSPHAZENE
Yasemin Tu¨mer,1 C¸ ig˘dem Yu¨ksektepe,2 Hu¨meyra Batı,1
Nezihe C¸ alıs¸kan,2 and Orhan Bu¨yu¨kgu¨ngo¨r2
1Department of Chemistry, Faculty of Arts and Sciences, Ondokuz Mayıs
University, Kurupelit, Samsun, Turkey
2Department of Physics, Faculty of Arts and Sciences, Ondokuz Mayıs University,
Kurupelit, Samsun, Turkey
Hexakis[2-methoxy-4-(2,3-dimethylphenylimino)phenylato]cyclotriphosphazene was pre-
pared by the reaction of hexakis[2-methoxy-4-formylphenoxy]cyclotriphosphazene and 3,4-
dimethylaniline. The structure of new cyclotriphosphazene derivative was determined by
elemental analysis, IR, 1H NMR, 13C NMR spectra, thermal analysis, and X-ray diffraction.
Supplemental materials are available for this article. Go to the publisher’s online edition of
Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental
file.
KEYWORDS
Dendrimers; hexakis[2-methoxy-4-formylphenoxy]cyclotriphosphazene;
phosphazenes; Schiff bases; X-ray diffraction
INTRODUCTION
Cyclotriphosphazenes are an important class of inorganic ring systems for two main
reasons. The first reason is substitution of P-X bonds in [NPX2]n (X = Cl or F; n = 3,4)
by many nucleophilic reagents to synthesize a variety of organocyclophosphazenes. The
specific physical or chemical properties of these compounds are imposed by the structures
of different side groups. The second reason of interest in these compounds stems from the
close relationship that exists between these ring systems with the high molecular weight
polyphosphazenes, the largest family of inorganic polymers known.1
Reactions at the exocyclic group of a substituted cyclophosphazene have become a
major synthetic methodology for producing new phosphazene derivatives that have a bulky-
side group. In addition, the multifunctional nature of chlorocylophosphazenes allows these
compounds to be utilized as dendrimer cores. N3P3Cl6 offers six branching points, which
is significantly more than those available with conventional organic cores, permitting the
Received 20 December 2009; accepted 9 February 2010.
Address correspondence to Yasemin Tu¨mer, Department of Chemistry, Faculty of Arts and Sciences,
Ondokuz Mayls University, TR-55139, Kurupelit, Samsun, Turkey. E-mail: enderyasemin@gmail.com
2449

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Y. TUMER ET AL.
2450
ready accommodation of a larger number of peripheral units around the cyclophopshazene
framework.2
In this article, we report the synthesis of a Schiff base derivative of hexakis[2-
methoxy-4-formylphenoxy]cyclotriphosphazene (I), which can be described as a den-
drimeric core.2 Cyclophosphazenes such as I and its Schiff base derivative, hexakis[2-
methoxy-4-(2,3-dimethylphenylimino)phenylato]cyclotriphosphazene (II), have been used
as preliminary models for polyphosphazenes.3,4 The structure of II was determined by el-
emental analysis, IR, 1H NMR, 13C NMR spectra, thermal analysis, and X-ray diffraction.
The crystal structure of I has been published previously.5
RESULTS AND DISCUSSION
Synthesis of II
The synthesis of II is summarized in Scheme 1. In the preparation of compound II,
I was allowed to react with 3,4-dimethylaniline in butanol. The mixture was refluxed for 5
days. The product was purified by recrystallization.6,7
CH3O
O
CH3O
6 HO
O
C
O
C
N2 K2CO
3 P3N3
H
P3N3Cl6
H
+
6
Acetonitrile
I
CH3O
CH3
CH3
CH3
CH3
H
I
NH
O
6
P3N3
+
C N
2
Butanol
6
II
Scheme 1
Characterization of II
The characteristic IR absorption bands of I and II were determined using KBr disc.
When the IR spectra of I and II are compared, it is seen that the C O vibration at 1697cm−1
region disapperared, and a new band appeared at the 1629 cm−1 region of the spectrum
because of C N vibration. II has four characteristic absoption bands. These bands are
shown at 1191–1150 cm−1, 1285 cm−1, 1035 cm−1, and 962 cm−1 and are due to P N,
P N P(asym), P N P(sym), and P OAr, respectively.
1H NMR and 13C NMR spectra of II are taken in DMSO-d6. The 1H NMR spectrum
of II shows one singlet at 8.45 ppm corresponding to the hexa-equvalent imine protons
CH N (6H). The phenyl and methoxy protons were also observed in the 6.92–7.52 and
3.79 ppm regions, respectively.
In the 13C NMR spectra of II, the C N peak is in the 158.39 ppm region. The
methoxy and phenyl carbons were also observed in the 55.79 and 111.36–150.59 ppm
regions, respectively.4,8

PREPARATION OF CYCLOTRIPHOSPHAZENE DERIVATIVE
2451
X-Ray Analysis
Crystallography. The molecular structure of the title compound II is shown
Figure 1. The molecule comprises a cyclotriphosphazene core and six terminal 2-methoxy-
4-(2,3-dimethylphenylimino) phenylato groups. The crystal is monoclinic, space group
P21/c, with a = 27.0435(6) Å, b = 19.2212(4) Å, c = 17.8449(5) Å, α, γ = 90◦ and β =
108.15(2)◦, V = 8814.4(4) Å3, Z = 4 (shown in Table I). The phosphazene rings are not
planar, with a total puckering parameter of QT = 0.241(3) Å. Literature values for puckering
of the phosphazene ring are QT = 0.255(2) Å.5 The conformation of the phosphazene ring
is twisted-boat [q2 = 0.241(3) Å, q3 = −0.010(2) Å, ꢀ2 = 266.1(7)◦ and θ2 = 92.42(71)◦].
The principal mean square atomic displacements U of the some of atoms such as C31,
C91, C92, C93, and C96 are higher than the other atoms in the compound. According to
cif results, this means U values are admitted. The R1 and wR2 indices are obtained higher
than expected due to high U displacements of some atoms.
Selected geometric parameters are listed in Table S1 (Supplemental Materials, avail-
able online). In the phosphazene ring, for the angles nearest to the macrocycle, viz. the endo-
cyclic α (N1−P1−N3, N2−P2−N1, N2−P3−N3) [116.61(18)◦, 116.72(19)◦, 117.2(2)◦]
and exocyclic αꢁ (O11−P1−O9, O5−P2−O7, O3−P3−O1) [94.83(18)◦, 99.41(17)◦,
99.34(19)◦], respectively, these values deviate slightly from those found in the standard
compound N3P3Cl6 [α 118.3(2)◦ and αꢁ 101.2(1)◦].9,10
Figure 1 The molecular structure of II.

¨
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Y. TUMER ET AL.
Table I Crystallographic data for II
Empirical formula
Molecular weight
Temperature, T (K)
Wavelength (Å)
Crystal system
Crystal size (mm3)
Space group
a (Å)
P3N3(C16NO2H16
1660.8
)
6
296
0.71073
Monoclinic
0.62 × 0.40 × 0.09
P21/c
27.0435(6)
19.2212(4)
17.8449(5)
90
108.150(20)
90
b (Å)
c (Å)
α (◦)
β (◦)
γ (◦)
Volume, V (Å3)
Z
8814.40(608)
4
T
min, Tmaks
0.937, 0.988
1.25
1.3–25.7
Calculated density (Mg m−3
θ range (◦)
)
Index ranges
Measured reflections
Independent reflections
Observed reflections (I > 2σ)
Goodness-of-fit on F 2
R index (I > 2σ)
h = –32→32, k = –23→23, l = –21→21
44280
16413
6729
0.938
0.078
0.149
wR2 index (I > 2σ)
. . .
termolecular hydrogen bond forms a C(13) graph-set chain,11 viz. C7−H7A O10
The crystal structure of II is stabilized by C H O hydrogen bonding. This in-
. . .
C86 C81 O9 P1 N3 P3 O1 C1 C6 O2, running along the [010] direction with
1
2
1
2
screw axis symmetry (–x, +y, –z) (shown in Figures S1 and S2, Supplemental Materi-
als) and by translation (x, y+n, z) (n is integer) of the molecule at (x, y, z). On the other
hand, as can be seen from Table S2 (Supplemental Materials), the intramolecular hydrogen
. . .
. . .
bonding, C18−H18 O1/ O2 and C34−H34 O8, may affect crystal packing. Aside from
. . .
this, C H π and π−π interactions are also effective in the crystal packing.
Thermal Decomposition Studies
The thermal behavior of the cyclophosphazene derivative II was investigated by
employing thermoanalytical TG, DTG and DTA methods simultaneously in the temperature
range of 20–1000◦C in a static air atmosphere. As shown in Figure S3, the endothermic
peak at 167.49◦C in the DTA curve, without any weight loss, clearly represents a physical
process and is attributed to the melting of II. As shown in the TG curve of II, the weight loss
starts at 292◦C and continues to 979◦C. The stages of decomposition are associated with
decomposition of organic groups and an exothermic oxidation process in the temperature
range of 292–979◦C (DTG max: 319, 340, 450, 537, and 721◦C). The release of the
volatile products such as aliphatic and aromatic substituents and then oxidation in static
air atmosphere results in the polymerization of the compound. The final decomposition
product is a cross-linked structure of phosphorus and nitrogen.12,13

PREPARATION OF CYCLOTRIPHOSPHAZENE DERIVATIVE
2453
EXPERIMENTAL
Instrumentation
Melting points were recorded on electrothermal melting point apparatus. FT-IR spec-
tra were recorded on a Mattson 1000 FT-IR spectrometer calibrated with polystyrene film
1
using the KBr disc. The H NMR and 13C NMR spectra were taken on a Bruker AC
200 MHz spectrometer, referenced to tetramethylsilane as an internal standard. DT, DTG,
and DTA curves were recorded simultaneously on a thermal analyzer. The experiments
were performed in static air atmosphere with a heating rate of 10◦C/min−1 from room
temperature to 1000◦C in platinum crucibles. The samples weighed approximately 10 mg,
and highly sintered α-Al2O3 was used as a reference material. The DTG sensitivity was
0.05 mg s−1. Elemental analysis was recorded by the Tubitak Atal Research Center in
Ankara.
Crystallographic Analysis
The suitable crystals of compound II for X-ray analysis were obtained by recrystal-
lization from acetonitrile:n-hexane (1:1) mixtures. Data collection was performed on a Stoe
IPDSII image plate detector using Mo Kα radiation (λ = 0.71019 Å). Details of the crystal
structure are given in Table I. Other details are as follows: Data collection: Stoe X-AREA.16
Cell refinement: Stoe X-AREA.14 Data reduction: Stoe X-RED.15 The structure was solved
by direct methods using SHELXS-97,16 and anisotropic displacement parameters were ap-
plied to non-hydrogen atoms in a full-matrix least-squares refinement based on F2 using
SHELXL-97.16 Molecular drawing was done using ORTEP-III.18 In the title compound,
the hydrogen atoms on C were placed at calculated positions (C–H = 0.93 Å, 0.96 Å for
methyl groups) and were allowed to ride on the parent atom [Uiso(H) = 1.2U(C) for CH
groups and Uiso(H) = 1.5U(C) for methyl groups]. The maximum difference density of
0.74 eÅ−3 indicated the presence of a possible atom site.
Synthesis and Purification
A butanol solution of hexakis[2-methoxy-4-formylphenoxy]cyclotriphosphazene
(1.00 g, 0.096 mmol), which was prepared according to the published procedure,5 was
added dropwise to a solution of 3,4-dimethylaniline (0.697 g, 0.576 mmol) in dry acetoni-
trile (20 mL) over a period of 1 h, and then the mixture was refluxed for 5 d. The residue was
washed with acetonitrile and n-hexane twice. The white product was purified by recrys-
tallization from acetonitrile:n-hexane(1:1) mixtures, mp 165–167◦C, 1.23 g (72%) yield.
Anal. Calc. for C96H96N9P3O12: C 69.43, H 5.83, N 7.59; found: C 69.78, H 5.01, N 7.85.
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