Syntheses, structure and intercalation properties of low-dimensional phenylphosphonates, A(HO3PC6H5)(H 2O3PC6H5) (A = alkali metal, NH 4 and TI)

Article abstract of DOI:10.1002/ejic.200500714

Seven new low-dimensional phenylphosphonates, A(H-O₃PC ₆H₅)(H₂O₃PC₆H ₅) [A = Li (1), Na (2), K (3), Rb (4), Cs (5), NH₄ (6) and T1 (7)], have been synthesized and characterized by X-ray diffraction, spectroscopic and thermal studies. They crystallize in triclinic unit cells with two formula units and have approximately planar arrangement of A⁺ ions, coordinated to oxygen atoms of phenylphosphonates, on both sides. Compounds 1 and 6 are one-dimensional, whereas others are two-dimensional. All of them undergo room-temperature intercalation reactions with primary n-alk-ylamines and ammonia. Single crystal X-ray structures of compounds 1, 2 and 6 have been determined. Wiley-VCH Verlag GmbH & Co. KGaA, 2005.

Full text of DOI:10.1002/ejic.200500714

FULL PAPER
DOI: 10.1002/ejic.200500714
Syntheses, Structure and Intercalation Properties of Low-Dimensional
Phenylphosphonates, A(HO3PC6H5)(H2O3PC6H5) (A = Alkali Metal, NH4
and Tl)
Koya Prabhakara Rao[a] and Kanamaluru Vidyasagar*[a]
Keywords: Phenylphosphonates / Organic-inorganic hybrid composites / X-ray diffraction / Layered compounds / Intercal-
ation
Seven new low-dimensional phenylphosphonates, A(H-
O3PC6H5)(H2O3PC6H5) [A = Li (1), Na (2), K (3), Rb (4), Cs
(5), NH4 (6) and Tl (7)], have been synthesized and charac-
terized by X-ray diffraction, spectroscopic and thermal stud-
ies. They crystallize in triclinic unit cells with two formula
units and have approximately planar arrangement of A+ ions,
coordinated to oxygen atoms of phenylphosphonates, on
both sides. Compounds 1 and 6 are one-dimensional,
whereas others are two-dimensional. All of them undergo
room-temperature intercalation reactions with primary n-alk-
ylamines and ammonia. Single crystal X-ray structures of
compounds 1, 2 and 6 have been determined.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2005)
Zn(O3PPh)·H2O, α- and β- forms of Al(HO3PPh)(O3PPh)·
H2O, Al(HO3PPh)3·H2O, Al2(O3PPh)3·2H2O, Mn(HO3P-
Ph)(O3PPh), Fe(HO3PPh)(O3PPh)·H2O, HFe(HO3PPh)4,
Introduction
Metal organophosphonates are a class of organic-inor-
ganic hybrid materials, in which the organophosphonate
groups are covalently bonded to the metal inorganic back-
bone. In the recent past, there has been a renewed interest
and activity in the research arena of metal organophos-
phonates,[1–6] mainly due to their varied compositions,
structural diversity and potential applications[7–11] like sor-
bents, ion-exchangers, sensors, and catalysts. The expan-
sion[1–6,12,13] of metal organophosphonate chemistry in-
cludes phosphonates and diphosphonates of s-, p-, d- and f-
block metals. The structures reported for these compounds
could be broadly classified into two categories, namely,
zero-dimensional types[14] such as mononuclear and com-
plex molecular clusters and extended framework types[15]
of one-, two- and three-dimensional networks. Mostly low-
dimensional, namely chain and layered, structures are ob-
served for the compounds of second type, due to the segre-
gation of hydrophobic regions of organic moieties from the
rest of the framework.
La(HO3PPh)(O3PPh),
Zr(O3PPh)2,
Th(O3PPh)2,
[VO(O3PPh)]·2H2O, [MoO2(O3PPh)]·H2O, [UO2(O3PPh)]·
0.7H2O, [UO2(HO3PPh)2(H2O)]2·8H2O, [(UO2)3(HO3PPh)2-
(O3PPh)2]·H2O. These examples illustrate the structural di-
versity and the compositional variations with different ra-
tios of metal to phenylphosphonates, mono- and di-anionic
forms of phenylphosphonic acid and inclusion of O2– and/
or H2O in the coordination sphere of metals. One note-
worthy feature of all reported phenylphosphonates is their
insolubility in water that enabled their isolation as precipi-
tates from aqueous solutions. Most of these compounds,
especially those with 1:1 and 1:2 ratios of metal to phenyl-
phosphonic acid content, are lamellar phases. They contain
layers of metal atoms coordinated to oxygen atoms of phos-
phonate groups and, in a few cases, additionally to O2– and/
or H2O as well. The hydrophobic phenyl groups of phos-
phonates protrude into the interlayer region, on both sides
of the inorganic metal layer.
Intercalation of metal phenylphosphonates is well
studied[16b,17b–17f] and important from the point of view of
sensors.[9] For example, the lamellar 1:1 divalent metal
phenylphosphonates, such as Zn(O3PPh)·H2O, are known
to intercalate ammonia and amines, which occupy the inter-
layer region and coordinate to the metal. This intercalation
involves Lewis acid–base reaction that brings a change in
the coordination sphere of the metal. The dependence of
interlayer distance of intercalates on the chain length of the
intercalated n-alkyl primary amine, structural elucidation of
intercalates and stereo selectivity towards primary amines
for intercalation have been reported.[17b–17f]
The solid-state chemistry of phenylphosphonates consti-
tutes a significant portion of this research area. Reported
are many investigations about the synthesis, structures and
properties of di-, tri-, tetra-, penta-, and hexavalent metal
phenylphosphonates[16–21] with extended frameworks, such
as Ca(HO3PPh)2, Ca(HO3PPh)2·2H2O, Pb(HO3PPh)2,
[a] Department of Chemistry,
Indian Institute of Technology Madras,
Chennai, 600036, India
E-mail: kvsagar@iitm.ac.in
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Intercalation Properties of Low-Dimensional Phenylphosphonates
FULL PAPER
All 1:2 tri- and divalent metal phenylphosphonates, such
as La(HO3PPh)(O3PPh)[18c] and Ca(HO3PPh)2·2H2O,[16b]
have similar lamellar structure of Zr(O3PPh)2,[19b] with dif-
ferent coordinations for metals. Lewis acid-base intercal-
ation of primary amines has been reported for only one
compound, Ca(HO3PPh)2·2H2O. These compounds con-
tain mono (HO3PPh)– anions and are, therefore, potential
solid Brönsted acids. The acid-strength would be higher for
lower-valent metal phases, and the potentiality of these
compounds as Brönsted-acid hosts, for intercalation of
bases such as ammonia and amines, has not been investi-
gated so far. This Brönsted acidity is distinctly different
from the one reported[22] as due to functional SO3H group
of the phenyl moiety.
It is in this context that 1:2 phenylphosphonates of
monovalent metals, A(HO3PPh)(H2O3PPh) are envisaged
to be strong solid Brönsted acids that can undergo intercal-
ation with bases. It is surprising that no structurally charac-
terized monovalent metal phenylphosphonate has been re-
ported so far. Na2(O3PPh) and Na(HO3PPh) are the only
two compounds of this family realized by Corbridge and
Tromans,[23] who reported the powder X-ray data without
any crystallographic information. In view of these observa-
tions, we undertook a study of 1:2 phenylphosphonates of
alkali and thallium metals and ammonium. We report here
the successful synthesis, characterization and intercalation
chemistry of seven new phenylphosphonates, A(HO3-
PC6H5)(H2O3PC6H5) [A = Li (1), Na (2), K (3), Rb (4), Cs
(5), NH4 (6) and Tl (7)].
Figure 1. Powder X-ray diffraction patterns of A(HO3PC6H5)-
(H2O3PC6H5) [A = Li (1), Na (2), K (3), Rb (4), Cs (5), NH4 (6)
and Tl (7)] compounds.
pounds 3 and 4 have the structure type of 5. The structural
and crystallographic similarities, as deduced from XRD
Results and Discussion
X-Ray Diffraction and Crystal Structures: The powder X- study, of the seven phosphonates, 1–7 are as follows: Two
ray diffraction (XRD) patterns (Figure 1) of all the seven formula units are present in their centrosymmetric triclinic
A(HO3PC6H5)(H2O3PC6H5) compounds are, in general, unit cells. A+ ions are confined approximately to ab plane
similar to one another, corroborating the similarity of the and coordinated to oxygen atoms of phosphonates on both
values of their triclinic unit cell parameters. The 001 reflec- sides. The phenyl groups are oriented, without interdigi-
tion, with the 2θ value of about 5°, is the most intense and tation and π-π stacking, in approximately perpendicular
the observed main reflections arise from a family of {00l} fashion to the ab planes. Thus hydrophobic regions of
planes. The values of unit cell volumes of 2–7 vary in ac- phenyl groups separate the inorganic ab planes. The ob-
cordance with the relative sizes of A ions and lithium com- served values of bond lengths and angles of these phos-
pound 1, however, has slightly bigger unit cell volume than phonates compare well with those reported16–21 in the lit-
sodium compound 2. For the four structurally charac- erature. The labeling Scheme followed is such that P(1) is
terized compounds 1, 2, 5 and 6, the observed powder XRD bonded to O(1)–O(3) oxygen atoms and C(1) carbon atom
patterns agree with those simulated, using the LAZY-PUL- of phenyl ring C(1)–C(6), whereas P(2) is similarly bonded
VERIX program,[24] on the basis of single-crystal X-ray to O(4)–O(6) and C(7) of phenyl ring C(7)–C(12).
structures. However, the observed relative intensities of
Lithium compound (1) is, as shown in Figure 2, one-di-
some of the 00l reflections are more than those calculated, mensional in nature. O(3) and O(6) form short P–O bonds
due to the preferential orientation of the crystallites. The of ca. 1.49 Å length. Lithium is tetrahedrally bonded to
XRD powder pattern of 2 is different from those of Na2- these two oxygen atoms of four [two P(1)O4 and two P(2)
(O3PPh) and Na(HO3PPh).[23]
O4] phosphonate moieties. Each LiO4 tetrahedron is con-
The values of the triclinic unit cell parameters of com- nected to two such tetrahedra, through O(3)–O(6) edges,
pounds 1–7, though similar, show that they have five types and also to phosphonate moieties, to form one dimensional
of structures. The single-crystal X-ray data sets of com- chains of Li(HO3PC6H5)(H2O3PC6H5), along a-axis. These
pounds 1, 2, 5 and 6 have enabled the identification of the chains are apart by 8.50 Å within the ab plane and 14.99 Å
four types, whereas the fifth type, namely the structure of between such planes. The other four oxygen atoms form
the thallium compound (7), could not be ascertained. Com- longer P–O bonds of 1.53–1.56 Å length and have acidic
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hydrogen atoms.[18d] The hydrogen bonding between these of ca. 1.56 Å length and have two acidic hydrogen atoms,
four oxygen atoms hold the chains along b-axis.
H(13) and H(14), that are hydrogen-bonded to O(5) and
O(2), respectively. Furthermore, O(4)–H(15) is strongly hy-
drogen-bonded to O(1).
The positional parameters of cesium (5) and ammonium
(6) compounds are similar. However, cesium compound is
two-dimensional and cesium is nine-coordinate, with the
maximum value of Cs–O bond length being 3.52(2) Å. The
layered framework of 5 is due to higher coordination
number of cesium, which bonds additionally to oxygen
atoms of those corresponding neighbouring chains in one-
dimensional 6. Compounds 3 and 4 are isostructural with
the layered 5, and potassium and rubidium are computed
to be eight-coordinate. It could only be inferred that the
structure type of thallium compound 7 has a similar ar-
rangement of phosphonate moieties, which bond differently
to thallium atoms in the inorganic ab plane. Thus the differ-
ences between the above five structure types stem from the
different types of coordination of A+ ions.
The reported 1:2 tetra-, tri- and divalent metal phenyl-
phosphonates, with no additional O2–/H2O, have similar
structural features of compounds 1–7. Zr(O3PPh)2,[19b] La-
(HO3PPh)(O3PPh),[18d] Mn(HO3PPh)(O3PPh),[18b] A(H-
O3PPh)2 (A = Ca, Sr, Ba, Pb)[16a–16e] and the compounds
1–7 are the only 1:2 metal phenylphosphonates, for which
Figure 2. Unit cell of A(HO3PC6H5)(H2O3PC6H5) [A = Li (1)
(left), Na (2) (middle) and NH4 (6) (right)], viewed along the a axis
(top: ball-stick representation) and the c axis (bottom: polyhedral
representation).
Sodium compound (2) is a two-dimensional phosphonate the unit cell parameters have been determined from either
(Figure 2). The layered framework could be conceived as single-crystal X-ray data or structural elucidation. Similar
being built from centrosymmetric Na2O6(O3P–C6H5)4 unit cell lengths of (5.36–6.16) Å×(7.65–10.215) Å are due
blocks, each of which consists of an edge-shared bioctahe- to analogous planar arrangement of A atoms. The different
dral Na2O10 unit, corner-connected to four phosphonates. types of coordination of A atoms and stacking of planes of
Only five of the crystallographically distinct oxygen atoms, A atoms are responsible for the variations in the third axis
O(1)–O(5), are involved in octahedral coordination of so- length and unit cell angles.
dium. Two NaO6 octahedra share an edge, O(5)–O(5)Ј to
Spectroscopic and Thermogravimetric Data: Infrared
form a Na2O10 unit, which links, at the O(5) and O(3) spectra of compounds 2 and 6 are presented in Figure 3.
atoms, to four phosphonate moieties. These building blocks The C–H stretching vibrations of the phenyl ring in the re-
are linked to one another such that the phosphonates of gion 3090–3000 cm–1, the aromatic C=C stretching vi-
one block are corner-connected to Na2O10 units of another, brations at 1438 cm–1, the peaks at 692 and 745 cm–1 repre-
resulting in the layered framework. Sodium atom is coordi- senting the out-of-plane bending of the mono substituted
nated to oxygen atoms of six phosphonate groups, whereas phenyl ring, the peak at 2376 cm–1, characteristic of
the phosphonates of P(1) and P(2) are coordinated to three PhPO3H group, the peak at 1594 cm–1 due to phenyl group
and two sodium atoms respectively. These Na(HO3PC6H5)- stretching, the P–O stretching vibrations in the region
(H2O3PC6H5) layers are stacked along c-axis, with an inter- 1200–1000 cm–1 and the O–P–O bending vibrations in the
layer distance of 15.59 Å. The three oxygen atoms, O(1), region 540–410 cm–1, are the common features[18a,21a] ob-
O(2) and O(4), form longer P–O bonds of 1.54–1.58 Å served in the infrared spectra of the seven compounds, 1–7.
length and have acidic hydrogen atoms. The hydrogen The infrared spectrum of ammonium compound (6), shows
bonding exists between these oxygen atoms as well as O(6). two additional peaks at 3240 and 1401 cm–1 corresponding
NH4(HO3PC6H5)(H2O3PC6H5) (6) is one-dimensional to the stretching and bending vibrations of the ammonium
compound (Figure 2). With the cut-off distance of 3.0 Å for ion.[25] All these compounds, as illustrated in the solid-state
bonding, the nitrogen atom is found to be hydrogen- 13C and 31P spectra (Figure 4) of 2, show four 13C sig-
bonded, in an irregular tetrahedral fashion, to four oxygen nals[16b] between 140.0–120.0 ppm, corroborating the pres-
atoms, O(1), O(2), O(3) and O(5), of four phenylphos- ence of aromatic carbon atoms and three 31P signals[18a] be-
phonate moieties. This arrangement leads to ladder-like tween –1.2 and 7.8 ppm. Thermogravimetric analysis re-
chains, parallel to a-axis. The layered framework is not feas- vealed, as illustrated with the case of 2 in the Figure 5, that
ible, because the nitrogen atoms are not hydrogen-bonded all compounds 1–7 are stable up to about 200 °C and then
to oxygen atoms of neighbouring chain in the ab plane, even undergo weight losses of 51.5%, 48.5%, 46.0%, 42.0%,
with the higher cut-off value of 3.6 Å for bonding. These 37.0%, 71.1% and 32.50%, respectively, in the temperature
chains are apart by 7.66 Å within the plane and 16.34 Å range 200–700 °C in four or five steps. These values agree
between the planes. O(3) and O(6) form longer P–O bonds with those calculated for AP2O5.5 as the products of decom-
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Intercalation Properties of Low-Dimensional Phenylphosphonates
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position for alkali and thallium metal compounds. All of
them undergo further decomposition above 700 °C.
Figure 5. Thermogravimetric curves of (a) sodium (2) compound
and its intercalates, (b) 2·(NH3)1.2, (c) 2·(C8H17NH2)1.5 and (d)
2·(C8H17NH2)4.1
.
reactions with ammonia and primary n-alkylamines,
CH3(CH2)n–1NH2 (n = 4–9, 12, 16, 18). These reactions,
as determined from chemical analysis and powder XRD,
spectroscopic and thermal studies, turned out to be success-
ful.
The optimum conditions, given in experimental section,
for the first method of intercalation processes have been
realized from the results of several trials, under different
conditions, of intercalation reaction of sodium compound
with n-octylamine. A variation of molar ratio of n-oc-
Figure 3. Infrared spectra of (a) sodium (2) and (b) ammonium (6) tylamine and sodium phosphonate 2, from 2:1 to 3:1 to 4:1,
compounds and the intercalates of sodium compound, (c) 2·
led to intercalates, 2·(C8H17NH2)x with the corresponding
(NH3)1.2 and (d) 2·(C8H17NH2)1.5
.
x values of 0.9, 1.5 and 1.5, showing that the maximum
intercalation at room temperature could be achieved with
the reactant molar ratio of 4:1. There was no significant
increase in the values of x, when similar reactions were car-
ried out under reflux conditions at 70–80 °C. Similar
attempts under solvothermal conditions, by heating reac-
tant mixtures with 4 mL of n-hexane solvent, at 170 °C over
a period of 2 days, resulted in only polycrystalline interca-
lates without any increase in the values of x. The second
method involving neat liquid amines at room temperature
is confined to CH3(CH2)n–1NH2 (n = 4–9,12) only.
The relevant data of the intercalates, 2·[CH3(CH2)n–1
-
NH2]x and 1–7·(C8H17NH2)x obtained by the first method,
are presented in Table 1. The values of x range from 0.5 to
4.0 and do not seem to show any systematic trend with
either n or A. The powder XRD patterns of 2·[CH3-
(CH2)n–1NH2]x intercalates, as shown for a few selected
cases in Figure 6, contain moderate to prominent reflec-
tions at low 2θ values of 2–5° and no significant reflections
with 2θ of Ͼ40°. The first reflection is found to be doubled
in a few cases such as 2·[CH3(CH2)11NH2]x. It is note-
worthy that the powder XRD patterns of these intercalates,
do not undergo any change, even when the samples were
heated in open air at 40–50 °C for 12 h. The d value of the
first reflection is considered to be associated with the dis-
Figure 4. Solid-state 13C (left) and 31P (right) NMR spectra of so-
dium (2) compound (bottom) and it’s intercalate 2·(C8H17NH2)1.5
(top).
Intercalation Reactions: These seven phosphonates, 1–7 tance between the ab planes. This is found to be higher than
are solid Brönsted acids with a porous region between the that observed for the parent phase 2, due to incorporation
inorganic ab planes. Therefore, they have been investigated of the amine in the porous region, perpendicularly to the
from the point of view of Brönsted acid–base intercalation inorganic ab planes, with the alkyl chains aligned out of the
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K. P. Rao, K. Vidyasagar
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perpendicular. These intercalates, unlike the parent 2, do
not show higher order 00l reflections prominently. The d
value increases with n except in the case of nonylamine in-
tercalate. The values of d do not show any systematic in-
crease with n, probably due to the presence of gauche and
trans conformations of the alkyl chains of the amines in
different proportions. In general, these powder XRD pat-
terns confirm the crystalline nature of intercalates and the
topotactic intercalation of the amines. The powder XRD
patterns of 1–7·(C8H17NH2)x intercalates also contain mod-
erate to prominent reflections at low 2θ values of 2–5° and
the values of d are higher than those in the parent phases.
However, the increase in the d values is not systematic with
respect to both A and x. Structural elucidation of these
intercalates would reveal the placement of the intercalated
amines and probably explain this lack of systematic varia-
tion of d with n, x and A. There are no structurally charac-
terized Brönsted acid–base intercalates of this type re-
ported, for a comparison. However, structurally charac-
terized Lewis acid–base intercalates, Zn(O3PPh)(RNH2) (R
= C3H9, C4H11, C5H13), were reported[17b] to exhibit similar
nonsystematic behavior, due to coordination of the interca-
lated amine to the metal.
Table 1. Interplanar distance (d), number (x) of mol of amine in-
tercalated of the 2·[CH3(CH2)n–1NH2]x (top) and 1–7·(C8H17-
NH2)x (bottom) intercalates.
n
–
4
5
6
7
8
9
12
16
18
Figure 6. Powder X-ray diffraction patterns of sodium (2) com-
pound and its intercalates, 2·[CH3(CH2)n–1NH2]x (n = 8, 9, 12, 16
and 18).
x
0.0 0.5 0.9 1.2 1.7 1.5 1.5 2.0 1.7 1.9
d [Å] 15.6 17.7 19.0 19.6 20.9 21.2 20.3 25.8 27.8 28.5
A
Li Na
K
Rb Cs
Tl NH4
compared to parent phases. Thermogravimetric analysis of
a few selected intercalates revealed that they undergo more
percentage of decomposition than the parent phases. For
example, the total decomposition of 84% for 2·(C8H17-
x
2.7 1.5 2.1 1.6 1.9 2.9 4.0
d [Å] 18.7 21.2 21.0 21.3 18.8 19.2 19.2
The infrared spectra (Figure 3) of intercalates contain, in NH2)x (Figure 5) starts at 70 °C and is completed by
addition to all the features of the infrared spectrum of par- 600 °C. The first two stages of weight loss of 36% in the
ent phase 2, peaks in the region 3100–2700 cm–1 attributed 70–200 °C range are attributable to the loss of intercalated
to N–H and C–H stretching vibrations[16b] of the amine amine, 1.5 mol of C8H17NH2. The spectral and thermal fea-
molecules. The CH2 bending bands observed around tures of other intercalates are similar to those of the sodium
1437 cm–1 and 1470 cm–1 are ascribed[26] to gauche and compound.
trans conformations of alkyl chains of amines, respectively.
The second method of intercalation is compared with the
The relative intensities of these two bands indicate that the first one, in terms of the compositions, the powder XRD
alkyl chains, in the intercalates containing C4–C8 and C9– patterns and spectral features of the corresponding interca-
C18 amines, are predominantly in gauche and trans confor- lates. The x values of 2·[CH3(CH2)n–1NH2]x are 1.5, 2.1, 2.0,
mations, respectively. The shift of N–H stretching vi- 1.4, 4.1, 2.4, 2.5 for n = 4–9 and 12, respectively. Similarly
brations towards lower frequencies suggests that the amine the x values of 1–7·(C8H17NH2)x are 2.8, 4.1, 2.7, 5.0, 5.0,
molecules are protonated[25] and electrostatically bonded to 3.2, 4.3, respectively. In general, the extent of intercalation,
oxygen atoms of phosphonate moieties. The solid-state 13C as corroborated by thermogavimetric study (Figure 5), is
NMR spectra (Figure 4) of the intercalates show signals be- larger in the second method. The powder XRD patterns
tween 140.0–125.0 ppm and also multiple signals in the re- revealed no increase in the d values with increase in x val-
gion 45.0–15.0 ppm, indicating the presence of both aro- ues. There are no significant changes in their infrared and
matic carbon atoms of the phenyl group and the aliphatic solid-state NMR spectra. The maximum amount of inter-
carbon atoms of the amines, respectively. The 13C signals of calation of primary amines reported is about two molecules
alkyl carbon atoms, though not fully resolved, are in order per formula unit of Ca(HO3PPh)2·2H2O[16b] and 1:1 phen-
of C1, C2, C3,...Cn. The 31P NMR spectra consist of three ylphosphonates.[17b–17f] Contrastingly, the extent of intercal-
signals between –0.83 and –9.37 ppm, with up-field shift ation in the present 1:2 phenylphosphonates 1–7 is as high
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Intercalation Properties of Low-Dimensional Phenylphosphonates
FULL PAPER
phonic acid, C6H5PO3H2 (Fluka) and primary n-alkylamines,
CH3(CH2)n–1NH2 (n = 4–9,12,16,18) (Fluka) were used, as pur-
chased, for the synthesis.
as five molecules of amine per formula unit. This could be
attributed to the Brönsted acidity of the compounds and
thus intercalates with x Ͼ 3 and x Յ 3 values could be
represented as CH3(CH2)n–1NH3]3[CH3(CH2)n–1NH2]x–3
[A(O3PC6H5)2] and [CH3(CH2)n–1NH3]x[AH3–x(O3PC6H5)2],
-
A(HO3PC6H5)(H2O3PC6H5) [A = Li (1), Na (2), K (3), Rb (4), Cs
(5), NH4 (6) and Tl (7)] compounds were synthesized, on the scale
of 1–2 grams, by evaporating aqueous solutions of stoichiometric
reactant mixtures of phenylphosphonic acid and appropriate
A2CO3 carbonate. Slow evaporation, at room temperature, led to
the formation of compounds as colourless flaky crystals. However,
evaporation on a steam bath yielded products in polycrystalline
form. In all the cases, the yields were almost quantitative. These
seven compounds were ascertained to be pure from the analysis of
their CHN content, using elemental analyzer, Perkin–Elmer series
11 Model. C12H13LiO6P2 (1) (322.10): calcd. C 44.75, H 4.07; found
C 44.29, H 4.11. C12H13NaO6P2 (2) (338.15): calcd. C 42.62, H
3.88; found C 42.75, H 4.04. KP2O6C12H13(3) (354.26): calcd. C
40.70, H 3.70; found C 40.59, H 3.77. C12H13O6P2Rb (4) (400.63):
calcd. C 36.00, H 3.27; found C 36.23, H 3.21. C12H13CsO6P2 (5)
respectively. Thus the amine upto the value of x = 3 is pres-
+
ent as RNH3 ions, whereas the amine in excess of x = 3 is
present as RNH2, held together by van der Waals forces in
the lattice.
The success and extent of ammonia intercalation in the
intercalates, 1–7·(NH3)x have been determined from infra-
red spectra and the analysis of carbon and nitrogen con-
tents. The infrared spectra contain two peaks at 3240 and
1450 cm–1 corresponding to the stretching and bending vi-
brations of the ammonium ion.[17e] The x values of 1–
7·(NH3)x are 2.0, 1.2, 1.1, 1.5, 1.7, 2.3 and 2.3, respectively,
and indicate no systematic variation with A. Thus these in-
(448.06): calcd.
C 32.17, H 2.90; found C 32.47, H 2.97.
tercalates could be represented as [NH4]x[AH3–x
-
C12H17NO6P2 (6) (333.21): calcd. C 43.20, H 5.14, N 4.20; found
C 43.70, H 4.89, N 4.50. C12H13O6P2Tl (7) (519.56): calcd. C 27.74,
H 2.52; found C 27.45, H 2.46.
(O3PC6H5)2]. Some of the reflections in the powder XRD
patterns of ammonia intercalates are more intense than
those in the parent phases. 2·(NH3)1.2, unlike the parent
phase 2, decomposes even below 200 °C and shows higher
weight loss (Figure 5). The total decomposition of 59% oc-
curs in the 160–700 °C range and the weight loss below
200 °C is probably due to the loss of intercalated ammonia.
The 2·(NH3)1.2 intercalate undergoes deintercalation, on
heating. The success of deintercalation is proved by CHN
Intercalation Reactions: Intercalation reactions of n-alkylamines
with the water-soluble phosphonates, 1–7 were carried out under
nonaqueous conditions by two methods at room temperature. In
the first method, a 4:1 molar reactant mixture of n-alkylamine and
phosphonate (1–7), along with 15 mL of n-hexane, was stirred for
1.5 days. The solid products were in the form of waxy material. In
the second method, the phosphonate (1–7) was added to excess of
liquid n-alkylamine (Ϸ 1:10 molar ratio) and the solid immediately
+
analysis and absence of vibrational frequencies of NH4 in
the infrared spectrum of deintercalate. Moreover, its pow- swelled, with the evolution of heat. The reaction mixture was left
undisturbed for 7 days. The waxy solid products, in both methods
of intercalation reactions, turned out to be dry powders after fil-
tration, washing with n-hexane and then air drying. Intercalation
of ammonia was achieved by passing ammonia gas for 2 h, over
solid phosphonates (1–7). In summary, all these trials pertain to
intercalation of nine amines, CH3(CH2)n–1NH2 (n = 4–9, 12, 16,
18), into sodium compound (2), intercalation of n-octylamine into
other six phosphonates and intercalation of ammonia into all seven
phosphonates. The amount of intercalated amine/ammonia was de-
termined from the analysis of the carbon and nitrogen contents of
der pattern is the same as that of parent phenylphosphonate
2, showing that the process of intercalation and deintercal-
ation is reversible and topotactic. This process of deintercal-
ation is probably true for other ammonia intercalates of this
study.
Zn(O3PPh) and [UO2(HO3PPh)2(H2O)]2·8H2O have
been reported[9,21c] to be sensors and proton conductors,
due to their intercalation and Brönsted acidic properties,
respectively. All the seven title compounds 1–7 exhibit both
these properties and could be potentially useful as sensors the solid intercalates, 2·[CH3(CH2)n–1NH2]x, 1–7·(C8H17NH2)x,
and 1–7·(NH3)x.
and proton conductors. A similar study of phenylarsonate
analogues has revealed interesting structural variations,
which we would report elsewhere.
Ammonia Deintercalation: Ammonia deintercalation of sodium
compound intercalate, 2·(NH3)1.2 was carried out by heating the
sample in air-oven at 170 °C over a period of 12 h.
Concluding Remarks
X-Ray Diffraction and Crystal Structure: The powder X-ray diffrac-
tion (XRD) patterns of the compounds 1–7 and their intercalation
products were recorded on XD-D1 X-ray diffractometer, Shim-
adzu, using Cu-Kα (λ = 1.5406 Å) radiation. Thin plate-like single
crystals, suitable for X-ray diffraction, were selected and mounted
with glue, on thin glass fibers in the case of compounds 2 and 4
and in glass capillaries along with the mother liquor, for other five
compounds. The X-ray data were gathered successfully from the
crystals of only four compounds, 1, 2, 5 and 6, at 25 °C, on an
ENRAF-NONIUS CAD4 automated four-circle diffractometer, by
the standard procedures involving ω-2θ scan techniques. There was
no decay of crystals during X-ray data collection. Empirical ab-
sorption corrections, based on psi-scans, were applied to the data
sets of 1 and 2 only. In the case of 5 and 6, these corrections were
not applied because of abnormal shape and bigger size of the crys-
tals employed. These data sets were reduced by routine computa-
A series of seven, new low-dimensional phenylphos-
phonates, A(HO3PC6H5)(H2O3PC6H5) (A = alkali metal,
NH4 and Tl) have been synthesized and characterized by
X-ray diffraction and spectroscopic studies. Lithium and
ammonium compounds are one-dimensional in nature,
whereas others are layered compounds. These compounds
are solid Brönsted acids and undergo room-temperature in-
tercalation reactions with primary n-alkylamines and am-
monia. The deintercalation of ammonia occurs on heating.
Experimental Section
Synthesis: The high-purity chemicals, A2CO3 [A = Li, Na, K, NH4
(SD Fine, India), Rb, Cs and Tl (Aldrich)] carbonates, phenylphos-
Eur. J. Inorg. Chem. 2005, 4936–4943
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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4941

K. P. Rao, K. Vidyasagar
Table 2. Pertinent crystallographic data for A(HO3PC6H5)(H2O3PC6H5) [A = Li (1), Na (2), NH4 (6)] compounds.
FULL PAPER
Compound
1
2
6
Formula
Formula weight
C12H13LiO6P2
322.10
C12H13NaO6P2
338.15
C12H17NO6P2
333.21
Crystal system
a [Å]
b [Å]
c [Å]
α [°]
β [°]
triclinic
triclinic
5.754(1)
7.904(2)
16.173(3)
103.41(1)
95.848(9)
97.03(1)
triclinic
6.036(9)
7.732(9)
16.61(1)
96.43(8)
97.63(8)
93.4(1)
5.4561(8)
8.638(1)
15.235(3)
100.26(2)
91.18(2)
89.90(1)
706.4(2)
γ [°]
V [Å3]
703.6(3)
761.3(2)
¯
¯
¯
Space group (no.)
Z
P1 (2)
P1 (2)
P1 (2)
2
2
2
ρcalcd. [g/cm3]
λ [Å]
1.514
1.54180
3.023
2885
2590
0.0446
0.1255
1.596
0.71073
0.363
2754
2481
0.0564
0.1378
1.454
0.71073
0.311
2947
2662
0.0618
0.1243
µ [mm–1]
Total reflections
Independent reflections
R[a]
[b]
Rw
[a] R = Σ||Fo| – |Fc||/Σ|Fo|. [b] Rw = [Σw(|Fo|2 – |Fc|2)2/Σw(|Fo|2)2]1/2
.
tional procedures. The structure solution and refinements were car-
ried out by the program[27] SHELXL-97 and the graphic pro-
gram[28] DIAMOND was used to draw the structures. The structure
solutions were obtained by direct method and all the non-hydrogen
atoms were refined anisotropically. The non-hydrogen atom content
in the asymmetric unit does not account for charge neutrality and
thus indicates the presence of three acidic protons of two phenyl-
phosphonic acid moieties. These acidic hydrogen atoms were lo-
cated in the difference Fourier maps and refined with riding model
restraints. The phenyl hydrogen atoms were introduced in the calcu-
lated positions and refined isotropically. The ammonium hydrogen
atoms of compound 6 were similarly located in the difference Fou-
rier map and refined with riding model restraints. The structure
refinement proceeded smoothly for 1 and 2. In the case of 6, the
final difference Fourier map showed no residual peak with electron
density of Ͼ 1 e/Å3 and the final R value was ca. 12%. Absorption
correction, based on the isotropically refined model, was applied
to the X-ray data using the program DIFABS[29] and R value had
come down to ca. 6.2%. Similar absorption correction was applied
to the X-ray data of cesium compound 5. The ten peaks with elec-
tron density of Ͼ 1 e/Å3 found in the final difference Fourier map,
were ghosts. The final R value was ca. 8.6% and the crystal struc-
ture of 5 is, nevertheless, qualitatively correct. The pertinent crys-
tallographic data of 1, 2 and 6 are presented in Table 2. CCDC-
276185 (for 1), CCDC-276186 (for 2) and CCDC-276187 (for 6)
contain the supplementary crystallographic data for this paper.
These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_
request/cif.
5: a = 6.16(1), b = 7.650(7), c = 16.96(2) Å, α = 97.38(7), β =
97.7(1), γ = 93.9(1)°, V = 775.5(6) Å3.
7: a = 5.946(9), b = 7.999(3), c = 17.11(6) Å, α = 90.1(5), β =
107.6(2), γ = 99.9(2)°, V = 763(4) Å3.
Spectroscopic Data: The infrared spectra in the range 400 to
4000 cm–1, were measured with a Bruker IFS 66V FT-IR spectrom-
eter. The samples were ground with dry KBr and pressed into
transparent discs for infrared spectroscopic study. Solid-state nu-
clear magnetic resonance (NMR) experiments were performed with
magic angle spinning (MAS) with Bruker DSX 300 and Avance
400 series spectrometers with the spinning frequency of 7.0 kHz
and recycle delay times of 2 and 5 s for 31P and 13C, respectively.
The first instrument operated at resonance frequencies of 121.5 and
75.5 MHz with the pulse lengths of 4.75 and 3.0 µs for 31P and 13C,
respectively. Similarly resonance frequencies of 162 and 100.5 MHz
with the pulse lengths of 5.0 and 5.0 µs for 31P and 13C, respectively,
were employed in the second one. Chemical shifts were referenced
to an external standard of 85% H3PO4 for 31P and glycine for 13C.
Thermal Analysis: Thermogravimetric analytical data were col-
lected with a Netzsch STA 409C instrument. The samples were
heated to 1000 °C at a rate of 10 °C per minute under a stream of
nitrogen gas.
Acknowledgments
We gratefully acknowledge the financial support (Project No: 98/
37/29/BRNS) received from the Board of Research in Nuclear Sci-
ences, Government of India. We thank the Sophisticated Analytical
Instrumentation Facility of our institute for single-crystal X-ray
data and Sophisticated Instrument Facility of Indian Institute of
Science, Bangalore for solid-state NMR spectroscopic data. We
acknowledge the help of Mr. Y. Ram Sai in the isolation and struc-
tural characterization of Na(HO3PC6H5)(H2O3PC6H5).
For lithium compound 1, an alternate triclinic unit cell, with a =
5.4561(8), b = 10.209(2), c = 15.235(3) Å, α = 98.03(2), β =
91.17(2), γ = 122.2(2) ° and V = 706.4(2) Å3, is possible. However,
our choice was based on the least deviation of unit cell angles from
the value of 90°. The crystals of the remaining four compounds
were good enough for only the determination of their triclinic unit
cell parameters, listed below.
[1] R. C. Finn, J. Zubieta, R. C. Haushalter, Prog. Inorg. Chem.
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3: a = 5.861(3), b = 7.865(3), c = 16.45(1) Å, α = 96.77(4), β =
97.57(9), γ = 94.82(5)°, V = 742.7(8) Å3.
[2] A. Clearfield, Z. Wang, J. Chem. Soc., Dalton Trans. 2002,
4: a = 5.9183(5), b = 7.9212(9), c = 16.860(2) Å, α = 96.948(5), β
= 93.352(2), γ = 94.519(9)°, V = 771.0(2) Å3.
2937–2947.
[3] A. Clearfield, Prog. Inorg. Chem. 1998, 47, 371–510.
4942
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Eur. J. Inorg. Chem. 2005, 4936–4943

Intercalation Properties of Low-Dimensional Phenylphosphonates
FULL PAPER
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Received: August 10, 2005
Published Online: November 2, 2005
Eur. J. Inorg. Chem. 2005, 4936–4943
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
4943