Ethane-1,2-diphosphonic acid as a building block in supramolecular chemistry; a pillared-layer framework and framework-encapsulated cations

Article abstract of DOI:10.1107/S0108768100014841

The 1:1 adduct of piperazine and ethane-1,2-diphosphonic acid is a salt [C₄H₁₂N₂]²⁺ ·[C₂H₆O₆P₂]^2-, in which both ions lie across centres of inversion in space group P2₁/c. The anions are linked by a single type of O - H...O hydrogen bond [O...O, 2.562 (3) A; H...O, 1.73 A, O - H...O, 169°] into (6, 3) nets built from a single type of R⁴₄(22) ring. The cations lie between these nets, linked to them by two types of N - H...O hydrogen bond [N...O, 2.635 (3) and 2.735 (3) A; H...O 1.72 and 1.82 A. N - H...O, 175 and 177°] such that the cations link adjacent sheets, thus forming a pillared-layer framework. The aquated adduct formed between trimethylenedipiperidine and ethane-1,2-diphosphonic acid is also a salt [C₁₃H₂₈N₂]²⁺·[C ₂H₆O₆P₂] ^2-·2.8[H₂O], in which there are 12 different types of hydrogen bond, eight O - H...O and four N - H...O. The anions are linked into chains by pairs of O -H...O hydrogen bonds and these chains are linked by the water molecules into a continuous three-dimensional framework. Within the anion/water framework are large voids which contain pairs of cations, linked to the framework by N - H...O hydrogen bonds.

Full text of DOI:10.1107/S0108768100014841

research papers
Acta Crystallographica Section B
Structural
Science
Ethane-1,2-diphosphonic acid as a building block in
supramolecular chemistry; a pillared-layer frame-
work and framework-encapsulated cations
ISSN 0108-7681
Paul S. Wheatley,a Alan J.
Lough,b George Ferguson,c
Colin J. Burchella and
The 1:1 adduct of piperazine and ethane-1,2-diphosphonic
acid is a salt [C4H12N2]2+Á[C2H6O6P2]2 , in which both ions lie
Received 6 October 2000
Accepted 23 October 2000
across centres of inversion in space group P21/c. The anions
are linked by a single type of OÐHÁ Á ÁO hydrogen bond
Christopher Glidewella*
ꢁ
Ê
Ê
[OÁ Á ÁO, 2.562 (3) A; HÁ Á ÁO, 1.73 A, OÐHÁ Á ÁO, 169 ] into (6,
3) nets built from a single type of R44ꢂ22† ring. The cations lie
between these nets, linked to them by two types of NÐHÁ Á ÁO
aSchool of Chemistry, University of St Andrews,
St Andrews, Fife KY16 9ST, Scotland, bLash
Miller Chemical Laboratories, University of
Toronto, Toronto, Ontario, Canada M5S 3H6,
and cDepartment of Chemistry and Biochem-
istry, University of Guelph, Guelph, Ontario,
Canada N1G 2W1
Ê
hydrogen bond [NÁ Á ÁO, 2.635 (3) and 2.735 (3) A; HÁ Á ÁO 1.72
ꢁ
Ê
and 1.82 A, NÐHÁ Á ÁO, 175 and 177 ] such that the cations link
adjacent sheets, thus forming a pillared-layer framework. The
aquated adduct formed between trimethylenedipiperidine and
ethane-1,2-diphosphonic
acid
is
also
a
salt
[C13H28N2]2+Á[C2H6O6P2]2 Á2.8[H2O], in which there are 12
different types of hydrogen bond, eight OÐHÁ Á ÁO and four
NÐHÁ Á ÁO. The anions are linked into chains by pairs of OÐ
HÁ Á ÁO hydrogen bonds and these chains are linked by the
water molecules into a continuous three-dimensional frame-
work. Within the anion/water framework are large voids which
contain pairs of cations, linked to the framework by NÐHÁ Á ÁO
hydrogen bonds.
Correspondence e-mail: cg@st-andrews.ac.uk
1. Introduction
The crystal structure of phenylphosphonic acid,
PhP(O)(OH)2, is built from continuous hydrogen-bonded
sheets in which it is possible to identify both centrosymmetric
R[ÐPO(OH)]2 dimer motifs and continuous C(4) [Á Á ÁO PÐ
OÐHÁ Á Á]n motifs (Weakley, 1976). In both methylenedipho-
sphonic acid CH2[P(O)(OH)2]2 and ethane-1,2-diphosphonic
acid (HO)2P(O)CH2CH2P(O)(OH)2 (Peterson et al., 1977) the
molecules are linked by hydrogen bonds into three-dimen-
sional frameworks in which C(4) chains are again a dominant
motif.
Phenylphosphonic acid forms hydrogen-bonded adducts
with a range of diamines, in which the supramolecular archi-
tecture can be one-, two- or three-dimensional (Ferguson et
al., 1998). A common feature of these adducts is the transfer of
protons from the acid to the amine, thus forming the anion
[PhP(O)2(OH)] : the combination of ion formation, on the
one hand, and on the other the ability of this anion to act as
both hydrogen-bond donor and hydrogen-bond acceptor,
leads to the formation of a rich diversity of strong, ionic
hydrogen bonds.
Developing this theme we have now embarked on a study of
ethane-1,2-diphosphonic acid (I), see scheme below, where at
least as rich a structural variety may be expected as that
previously observed in the adducts formed by phenyl phos-
phonic acid. We have already reported the structure of the
hydrated 1:1 adduct formed by ethane-1,2-diphosphonic acid
# 2001 International Union of Crystallography
Printed in Great Britain ± all rights reserved
ꢀ
Acta Cryst. (2001). B57, 95±102
Wheatley et al. Ethane-1,2-diphosphonic acid 95

research papers
with 4,40-bipyridyl (Glidewell et al., 2000). In this paper we
report the synthesis of adducts with three further diamines: a
6.1%; C15H34N2O6P2Á2.8H2O requires C 40.0, H 8.9, N 6.2%:
(3) found C 33.3, H 5.9, N 4.4%; C17H30N2O12P4ÁMeOHÁ2H2O
requires C 33.4, H 5.9, N 4.3%. Crystals of (1) and (2) suitable
for single-crystal X-ray diffraction were selected directly from
the analytical samples: no suitable crystals of (3) have yet been
obtained.
non-solvated
1:1
adduct
with
piperazine
(II)
[C4H10N2]Á[(HO)2P(O)CH2CH2P(O)(OH)2] (1), and solvated
adducts formed with two chain-extended diamines;
(2)
[C13H26N2]Á[(HO)2P(O)CH2CH2P(O)(OH)2]Á2.8H2O
formed with the extended piperazine analogue 4,4-trimethyl-
enedipiperidine (III) and [C13H14N2]Á[(HO)2P(O)CH2CH2-
P(O)(OH)2]Á[CH4O]ÁH2O (3) formed with the corresponding
extended 4,4-bipyridyl analogue 4,4-trimethylenedipyridine
(IV). We report here the structures of (1) and (2), which prove
to be the salts [C4H12N2]2+Á[C2H6O6P2]2 and [C13H28-
N2]2+Á[C2H6O6P2]2 Á2.8H2O, respectively.
2.2. Data collection, structure solution and refinement
Diffraction data for (1) and (2) were collected at 100 (2) K
using a Nonius Kappa-CCD diffractometer, using graphite-
Ê
monochromated Mo Kꢁ radiation (ꢂ = 0.71073 A). Other
details of cell data, data collection and re®nement are
summarized in Table 1, together with details of the software
employed (Ferguson, 1999; Gabe et al., 1989; Johnson, 1976;
Nonius, 1997; Otwinowski & Minor, 1997; Sheldrick, 1997a,b;
Spek, 2000). For both compounds the space group P21/c was
uniquely determined from the systematic absences. The
structures were solved by direct methods and re®ned with all
data on F2. A weighting scheme based upon P ˆ ‰Fo2 ‡ 2Fc2Š=3
was employed in order to reduce statistical bias (Wilson,
1976). All H atoms in the organic components were located
from difference maps and all were included in the re®nements
as riding atoms with OÐH 0.84, NÐH 0.92, CÐH 0.99 (CH2)
Ê
and 1.00 A (CH). It was apparent at an early stage in the
re®nements that two H atoms had been transferred from the
acid units to the diamine units. In (2) three sites were located
for O atoms of water molecules: of these, one, O3, is both fully
occupied and fully ordered and the associated H atoms were
located without dif®culty. The O atom of a second water
molecule was split over two closely adjacent sites and inde-
pendent re®nement of the two site-occupation factors led to
values of 0.866 (11) and 0.134 (11), respectively, indicating that
this pair of sites, taken together, accommodates a complete
water molecule: the H atoms associated with the major site,
designated O4, were located but those associated with the
minor site, designated O41, could not be found. The O atom of
the third water molecule was also found to be split over two
closely adjacent sites for which the site occupation factors
re®ned to 0.584 (10) and 0.209 (10): hence, this pair of sites
accommodates signi®cantly less than one complete water
molecule. The H atoms associated with the major site O5 were
located, but not those associated with the minor site, O51. All
H atoms, including those on O3, O4 and O5 were fully
2. Experimental
2.1. Synthesis
2.1.1. Ethane-1,2-diphosphonic acid. Triisopropyl phos-
phite (83.3 g, 0.40 mol) was added dropwise, over a period of
45 min, to 1,2-dibromoethane (18.8 g, 0.10 mol) heated to
423 K: the mixture was held at this temperature until evolu-
tion of 2-bromopropane ceased. Tetraisopropyl ethane-1,2-
diphosphonate was isolated by fractional distillation. NMR
(CDCl3): ꢀ(H) 1.33 (24H, d, J = 6.6 Hz, 8 Â CH3), 1.92 (4H, m,
2 Â CH2), 4.70 (4H, m, 4 Â CH); ꢀ(C) 21.0 (JPC = 130 Hz,
CH2), 24.6 (CH3), 712.0 (CH); ꢀ(P) 28.2. This ester was then
re¯uxed for 4 h with an excess of concentrated aqueous
hydrochloric acid: the mixture was then cooled and evapo-
rated to dryness. The solid residue was recrystallized from
water to give ethane-1,2-diphosphonic acid (I) in almost
quantitative yield. Analysis: found C 12.8, H 4.1%; C2H8O6P2
requires C 12.6, H 4.2%. NMR (CDCl3): ꢀ(H) 1.93 (4H, m, 2 Â
CH2), 3.30 (4H, br, 4 Â OH); ꢀ(C) 22.0 (JPC = 125 Hz, CH2);
ꢀ(P) 28.0.
2.1.2. Compounds (1)±(3). For each adduct, equimolar
quantities of the acid (I) and the appropriate diamine, (II)±
(IV), were separately dissolved in methanol: the solutions
were mixed and set aside to crystallize, exposed to the
laboratory atmosphere, producing (1)±(3), respectively.
Analyses: (1) found C 26.0, H 6.6, N 9.9%; C6H18N2O6P2
requires C 26.1, H 6.6, N 10.2%; (2) found C 40.3, H 9.3, N
Ê
ordered. The OÐH distances were initially re®ned, to 0.85 A,
using a common free variable: in the ®nal re®nement cycles
Ê
these distances were set to 0.85 (3) A by use of a DFIX
command.
The diagrams were prepared with the aid of PLATON
(Spek, 2000). Hydrogen-bond dimensions are presented in
Table 2 and other selected dimensions in Table 3.1 Figs. 1 and 2
show the molecular components, with the atom-labelling
schemes. Figs. 3±7 illustrate aspects of the supramolecular
structures.
1 Supplementary data for this paper are available from the IUCr electronic
archives (Reference: NA0111). Services for accessing these data are described
at the back of the journal.
ꢀ
96 Wheatley et al. Ethane-1,2-diphosphonic acid
Acta Cryst. (2001). B57, 95±102

research papers
measured at 300 MHz, can be analysed as a second-order
spectrum of the type [AX2]2 (Harris, 1964), in which
3. Results and discussion
3.1. Syntheses and molecular constitutions
3
|2JHP + JHP| is 9.2 Hz. This spectrum is consistent with an
Ethane-1,2-diphosphonic acid (I) was prepared by hydro-
lysis of the corresponding isopropyl ester, which itself had
been prepared by reaction of 1,2-dibromoethane with triiso-
propyl phosphite.
antiperiplanar, effectively centrosymmetric conformation in
solution, exhibiting no free rotation about the central CÐC
bond. It is interesting to note that in the solid state the
molecules of this acid lie across centres of inversion (Peterson
et al., 1977), while molecular modelling of isolated molecules
using the HyperChem package (Hypercube Inc., 1999) also led
to the centrosymmetric form as the most stable conformer. A
BrCH2CH2Br ‡ 2PꢂOiPr†
3
i
! ꢂ PrO†2PꢂO†CH2CH2PꢂO†ꢂOiPr† ‡ 2iPrBr ꢂ1†
2
1
i
ꢂ PrO†2PꢂO†CH2CH2PꢂO†ꢂOiPr† ‡ 4H2O
precisely similar pattern occurs in the H spectrum of the
3
2
isopropyl ester intermediate, where |2JHP + JHP| is 9.3 Hz,
! ꢂHO†2PꢂO†CH2CH2PꢂO†ꢂOH† ‡ 4iPrOH
ꢂ2†
2
again indicating a rigid and effectively centrosymmetric
conformation.
It was found necessary to use triisopropyl phosphite rather
than the simpler and more obvious trimethyl phosphite. When
P(OMe)3 was employed in the ®rst step, the sole product
isolated was the rearrangement product MeP(O)(OMe)2,
formed by the very rapid reaction of the ester with the initial
by-product MeBr. Since secondary bromoalkanes react with
P(OR)3 much more slowly than primary bromoalkanes, the
use of the isopropyl ester effectively prevents this side reac-
tion. Consistent with these observations, it has previously been
reported (Moedritzer & Irani, 1961) that using the primary
alkyl ester P(OEt)3 in reactions analogous to equation (1)
gave only poor yields of (EtO)2P(O)(CH2)nP(O)(OEt)2 when
n = 1 or 2.
Compounds (1) and (2), produced by co-crystallization of
the acid (I) with the aliphatic diamines (II) and (III),
respectively, are both 1:1 salts. However, while (1),
[C4H12N2]2+Á[C2H6O6P2]2 , contains no solvent molecules, (2)
on the other hand crystallizes as an aquated salt,
[C13H28N2]2+Á[C2H6O6P2]2 Á2.8H2O. Microanalysis was unable
to distinguish between 2.5 and 3.0 molecules of water per ion
pair, but the structure analysis (see x3.2.2) showed that there
were ca 2.8 molecules of water per ion pair (see also x2.2), all
of which are intimately bound into the supramolecular struc-
ture. In (3) the ratio of acid-to-diamine is 2:1 and the addi-
tional crystals contain one molecule of methanol and two of
water per diamine: if the diamine is doubly protonated and the
methanol and water molecules are unprotonated, then each
acid has transferred only one proton rather than the two
The acid (I) was identi®ed by microanalysis and by NMR
spectroscopy. The 1H resonance of the PCH2CH2P unit,
Figure 1
The molecular components of (1) showing the atom-labelling scheme.
Displacement ellipsoids are drawn at the 30% probability level. Atoms
marked with a star (*) or hash (#) are at the symmetry positions
(2 x; 1 y; z) and (1 x; 1 y; 1 z), respectively.
Figure 3
Part of the crystal structure of (1) showing formation of a (6, 3) net of
Figure 2
The asymmetric unit of (2), showing the atom-labelling scheme.
Displacement ellipsoids are drawn at the 30% probability level. H atoms
associated with the minor occupancy sites O41 and O51 could not be
located (see text).
anions, lying parallel to (100) and built from R44ꢂ22† rings. For the sake of
clarity H atoms bonded to C are omitted. Atoms marked with a star (*) or
hash (#) are at the symmetry positions
x; 1 y; z, respectively.
1
2
2
x;
‡ y; 12
z and
2
ꢀ
Acta Cryst. (2001). B57, 95±102
Wheatley et al. Ethane-1,2-diphosphonic acid 97

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Table 1
Experimental details.
a double donor in OÐHÁ Á ÁO
hydrogen bonds and hence acts
as
(1)
(2)
a
sixfold acceptor of
hydrogen bonds. Each cation is
linked to four different anions:
each anion is linked to four
cations and four other anions.
The overall structure of (1) is
most simply described in terms
of the substructure formed by
the anions alone, two-dimen-
sional nets and then in terms of
the linking of these nets by the
cations to form a three-dimen-
sional framework. The anions
are linked by OÐHÁ Á ÁO
hydrogen bonds into sheets
lying parallel to (100). Atom O3
at (x, y, z), which is a component
Crystal data
Chemical formula
Chemical formula weight
Cell setting, space group
Ê
a, b, c (A)
C4H12N2ÁC2H6O6P2
276.16
Monoclinic, P21=c
7.3914 (6), 9.3343 (7),
9.3590 (6)
90, 107.291 (4), 90
616.53 (8)
2
1.488
C13H28N2ÁC2H6O6P2Á2.8H2O
450.01
Monoclinic, P21=c
6.1218 (2), 20.6215 (7),
18.1831 (7)
90, 99.942 (2), 90
2260.98 (14)
4
1.332
Mo Kꢁ
13 672
ꢁ, ꢃ, ꢄ ꢂꢁ†
3
Ê
V (A )
Z
Dx (Mg m
3
)
Radiation type
Mo Kꢁ
3237
No. of re¯ections for
cell parameters
ꢅ range (ꢁ)
2.89±27.40
0.368
150 (1)
Needle, colourless
0.20 Â 0.06 Â 0.02
3.01±30.05
0.237
120 (1)
Block, colourless
0.30 Â 0.12 Â 0.12
1
ꢆ (mm
)
Temperature (K)
Crystal form, colour
Crystal size (mm)
Data collection
Diffractometer
Data collection method
Kappa±CCD
' and ! scans
with ꢇ offsets
Multi-scan (Otwinowski &
Minor, 1997)
0.9300
Kappa±CCD
' and ! scans
with ꢇ offsets
Multi-scan (Otwinowski &
Minor, 1997)
0.9318
1
of the anion centred at (1, , 0),
acts as a hydrogen-bond donor
2
Absorption correction
1
2
to O2 at (2 x;
a
‡ y; 12 z),
component of the anion
Tmin
Tmax
centred at (1, 0, 12). O3 at
0.9927
3237, 1401, 947
0.9719
13 672, 6599, 4617
No. of measured, independent and
observed parameters
Criterion for observed
re¯ections
Rint
ꢅmax (ꢁ)
Range of h, k, l
1
2
(2 x;
‡ y; 12 z) in this
same anion in turn acts as a
donor to O2 at (x; 1 ‡ y; z),
thus producing a C(4) chain
parallel to [010]. Each anion is,
however, centrosymmetric and
the propagation of the C(4)
motif by the successive centres
of inversion leads to the forma-
tion of a (6, 3) net (Batten &
Robson, 1998) built from a
single type of R44ꢂ22† ring (Fig.
3). Within this net, the rings are
centrosymmetric and the ring
centres generate an A-face
centring pattern. One net passes
through each unit cell and the
perpendicular distance between
I > 2ꢈ(I)
I > 2ꢈ(I)
0.057
27.40
0 ! h ! 9
0 ! k ! 12
12 ! l ! 11
0.033
30.05
0 ! h ! 8
29 ! k ! 0
25 ! l ! 24
Re®nement
Re®nement on
R‰F2>2ꢈꢂF2†Š, wRꢂF2†, S
No. of re¯ections and parameters
used in re®nement
H-atom treatment
F2
F2
0.0591, 0.1231, 1.038
1401, 74
0.0506, 0.1139, 1.022
6599, 284
H-atom parameters
constrained
w = 1/[ꢈ2(F2o) + (0.0312P)2
+ 0.6688P], where
P = (F2o + 2F2c)/3
0.000
H-atom parameters
constrained
w = 1/[ꢈ2(F2o) + (0.0333P)2
+ 1.1810P], where
P = (F2o + 2F2c)/3
0.001
Weighting scheme
ꢂÁ=ꢈ†
max
3
Ê
Áꢉmax, Áꢉmin (e A
)
0.372, 0.429
0.399, 0.388
Ê
adjacent nets, asin ꢃ, is ca 7 A.
transferred in (1) and (2). In the absence of structural data,
further speculation on the constitution of this material is
unlikely to be fruitful.
The space between the van der Waals surfaces of adjacent nets
is occupied by the cations, so that the overall supramolecular
architecture is that of a pillared-layer structure (Fig. 4). The
reference cation centred at (12, 21, 12) forms NÐHÁ Á ÁO hydrogen
bonds (Table 2) to the anions centred at (1, 12, 0), (1, 21, 1), (0, 21,
1) and (0, 12, 0): of these anions, the ®rst two are components of
one layer, at x = 1, and the latter two are components of the
adjacent layer, at x = 0. In this manner, all of the stacked layers
are linked into a continuous framework, but there are no
residual solvent-accessible voids in the structure. There are in
addition two CÐHÁ Á ÁO hydrogen bonds involving one of the
CH2 groups adjacent to the charged N in the cation (Table 2).
Of these, the C2ÐH2BÁ Á ÁO3iv [(iv) = 1 ‡ x; y; z] interaction
serves to reinforce the linking of the (100) sheets.
3.2. Supramolecular structures
3.2.1. Compound (1). In (1) the component ions
[H2N(CH2CH2)2NH2]2+ and [(HO)(O)2PCH2CH2P(O)2-
(OH)]2 both lie across centres of inversion and, for the sake
of convenience, the reference cation was centred at (12, 21, 21). In
the asymmetric unit selected (Fig. 1) the reference anion is
thus centred at (1, 12, 0). There are only three types of hydrogen
bond in the structure, but each cation acts as a fourfold donor
in NÐHÁ Á ÁO hydrogen bonds (Table 2) and each anion acts as
ꢀ
98 Wheatley et al. Ethane-1,2-diphosphonic acid
Acta Cryst. (2001). B57, 95±102

research papers
Table 2
Hydrogen-bond geometry (A, ).
support of this: ®rst, the H atoms associated with the low
occupancy O41 and O51 sites could not be located, secondly,
the DÁ Á ÁA distances involving O41 and O51 are, in general,
very similar to the corresponding distances involving O4 and
O5, respectively (Table 2). The sole signi®cant difference
arises in the O3Á Á ÁO4 and O3Á Á ÁO41 distances: these three
sites are almost co-linear with O41 on the side of O4 remote
from O3. Overall, the hydrogen-bonding behaviour of the low-
occupancy water molecules can be expected with reasonable
con®dence to mimic that of the major components.
Subject to this constraint there are 12 distinct hydrogen
bonds within the structure of either OÐHÁ Á ÁO or NÐHÁ Á ÁO
types. Each cation acts as a fourfold donor in NÐHÁ Á ÁO
hydrogen bonds; each anion acts as a twofold donor in OÐ
HÁ Á ÁO hydrogen bonds, as a twofold acceptor in NÐHÁ Á ÁO
hydrogen bonds and as a sixfold acceptor in OÐHÁ Á ÁO
hydrogen bonds. The water molecules containing O3 and O4
are both double donors and double acceptors of hydrogen
bonds: that containing O5 is a double donor, but it is not an
acceptor of signi®cant hydrogen-bonding interactions.
As with (1), the substructure approach (Gregson et al.,
2000) provides the most straightforward route to an under-
standing of the structure. The anions are linked by paired OÐ
HÁ Á ÁO hydrogen bonds into a single-component chain; these
chains are linked by the water molecules into a continuous
three-dimensional two-component framework, which contains
large voids, and these voids contain pairs of cations which
themselves are linked to the water/anion framework by means
of NÐHÁ Á ÁO hydrogen bonds. Each of these structural
features will be described in turn.
ꢁ
Ê
D
H
A
HÁ Á ÁA
DÁ Á ÁA
DÐHÁ Á ÁA
(1)
O3
N1
N1
C2
C2
H3
O2i
O2ii
O1
1.73
1.82
1.72
2.37
2.36
2.562 (3)
2.735 (3)
2.635 (3)
3.166 (4)
3.285 (5)
169
177
175
136
155
H1C
H1D
H2A
H2B
O1iii
O3iv
(2)
O13
O23
O3
H13
H23
H31
O22iv
O12v
O4
1.74
1.76
1.98 (2)
2.568 (2)
2.598 (2)
2.816 (3)
3.50 (2)
2.740 (2)
2.756 (3)
2.65 (2)
2.665 (2)
2.61 (2)
2.813 (4)
2.956 (9)
2.802 (4)
2.86 (2)
170
173
168 (2)
O3
O3
O4
O41
O4
O41
O5
O41
O11
H32
H41
1.91 (2)
1.91 (2)
167 (2)
174 (2)
O11iv
O11iv
O21vi
O21vi
O3
H42
H51
H52
1.82 (2)
2.09 (4)
1.97 (3)
172 (3)
143 (3)
168 (3)
O51
O5
O3
O11vii
O11vii
O12
O51
N11
N11
N11
N21
N21
H11A
H11B
1.77
1.83
2.691 (2)
2.740 (3)
2.73 (2)
2.732 (2)
2.800 (2)
177
172
O4
O41
H21A
H21B
O21ii
O3viii
1.82
1.89
172
169
1
2
Symmetry codes: (i) 2 x;
‡ y; 12 z; (ii) 2 x; 1 y; 1 z; (iii) x; 21 y; 12 ‡ z; (iv)
1 ‡ x; y; z; (v) 1 ‡ x; y; z; (vi)
1 ‡ x; 12 y; 12 ‡ z; (vii)
1
x; y; 1 z; (viii)
2
x; 12 ‡ y; 32 z.
3.2.2. Compound (2). In (2) all the components, both the
ions [H2NC5H9(CH2)3C5H9NH2]2+ and [(HO)(O)2PCH2-
CH2P(O)2(OH)]2 , as well as the neutral water molecules
(Fig. 2) lie in general positions. The supramolecular structure
analysis and description is complicated somewhat by the
disorder and partial occupancy of some of the water sites (see
x2.2). For the sake of simplicity, the structural description will
consider only those water molecules containing O3, O4 and
O5: the low occupancy O41 and O51 (adjacent to O4 and O5,
respectively) will be ignored. Two reasons may be adduced in
In the formation of the anion chains O13 at (x; y; z) acts as a
donor to O22 at ( 1 ‡ x; y; z) and O23 at ( 1 ‡ x; y; z) acts
Figure 5
Part of the crystal structure of (2), showing the combination of
Cꢂ7†‰R22ꢂ8†Š anion chains parallel to [100] and C22ꢂ9† anion/water chains
parallel to [001] forming a (010) sheet built from R66ꢂ26† rings. For the
sake of clarity H atoms bonded to C are omitted. Atoms marked with a
star (*) or hash (#) are at the symmetry positions 1 ‡ x; y; z and
1 ‡ x; 12 y; 12 ‡ z, respectively.
Figure 4
Part of the crystal structure of (1), showing the cation pillars connecting
adjacent anionic layers. For the sake of clarity H atoms bonded to C are
omitted. Atoms marked with a star (*) are at the symmetry position
1
x; 1 y; 1 z.
ꢀ
Acta Cryst. (2001). B57, 95±102
Wheatley et al. Ethane-1,2-diphosphonic acid 99

research papers
Table 3
Selected geometric parameters (A, ).
a
hydrogen bond from O4 at
ꢁ
Ê
(1 x; 12 y; 12 ‡ z), as does O21 in the
anion at (x; y; 1 ‡ z). These hydrogen
bonds give rise to a C22ꢂ9† chain, gener-
ated by the action of the glide plane and
running parallel to the [001] direction
(Fig. 5). The combination of the [100]
anion chains and the anion/water chains
along [001] produces sheets parallel to
(010) built from a single type of R66ꢂ12†
ring (Fig. 5): two of these sheets pass
through each unit cell, one in the domain
(a) Cation geometries
(1)
N1ÐC2
C2ÐC3i
1.487 (4)
1.510 (5)
N1ÐC3
1.482 (4)
(2)
N11ÐC12
N11ÐC16
C12ÐC13ÐC14ÐC17
C13ÐC14ÐC17ÐC18
C14ÐC17ÐC18ÐC19
C15ÐC14ÐC17ÐC18
1.491 (2)
1.494 (2)
178.9 (2)
171.7 (2)
175.6 (2)
66.4 (2)
N21ÐC22
N21ÐC26
C17ÐC18ÐC19ÐC24
C18ÐC19ÐC24ÐC25
C19ÐC24ÐC25ÐC26
C18ÐC19ÐC24ÐC23
1.495 (2)
1.486 (2)
177.0 (2)
177.8 (2)
174.6 (2)
60.2 (2)
1
2
0 < y < and the other in the domain
12 < y < 1.0.
Neighbouring sheets are linked by a
very simple cyclic motif involving the O3
and O5 water molecules. Within the
(b) Anion geometries
(1)
(2)
P1ÐO1
P1ÐO2
P1ÐO3
P1ÐC1
C1ÐC1ii
1.504 (2)
1.514 (2)
1.575 (2)
1.802 (3)
1.531 (6)
P1ÐO11
P1ÐO12
P1ÐO13
P1ÐC1
1.508 (2)
1.519 (2)
1.571 (2)
1.809 (2)
1.529 (3)
P2ÐO21
P2ÐO22
P2ÐO23
P2ÐC2
1.511 (2)
1.507 (2)
1.586 (2)
1.806 (2)
asymmetric unit (Fig. 2) O5 is
a
hydrogen-bond donor, via H51, to O3,
which is itself a donor, via H32 to O11:
O5 at (x; y; z) is also a donor, via H52, to
O11 at (1 x; y; 1 z), thus produ-
cing an R46ꢂ12† ring (Fig. 6) which is
centrosymmetric and almost planar. The
anion at (x; y; z) is a component of the
C1ÐC2
C1ÐP1ÐO1
C1ÐP1ÐO2
C1ÐP1ÐO3
O1ÐP1ÐO2
O2ÐP1ÐO3
O3ÐP1ÐO1
C1iiÐC1ÐP1
109.0 (2)
108.3 (2)
105.4 (2)
115.8 (2)
106.4 (2)
111.4 (2)
113.7 (3)
C1ÐP1ÐO11
C1ÐP1ÐO12
C1ÐP1ÐO13
O11ÐP1ÐO12
O12ÐP1ÐO13
O13ÐP1ÐO11
C2ÐC1ÐP1
108.62 (8)
107.92 (8)
105.87 (8)
114.59 (8)
110.17 (7)
109.30 (8)
111.4 (2)
C2ÐP2ÐO21
C2ÐP2ÐO22
C2ÐP2ÐO23
O21ÐP2ÐO22
O22ÐP2ÐO23
O23ÐP2ÐO21
C1ÐC2ÐP2
106.51 (8)
110.12 (8)
105.50 (8)
116.20 (8)
110.58 (7)
107.33 (8)
116.2 (2)
C1iiÐC1ÐP1ÐO1 178.9 (3)
C1iiÐC1ÐP1ÐO2 52.1 (4)
C2ÐC1ÐP1ÐO11
C2ÐC1ÐP1ÐO12
177.7 (2) C1ÐC2ÐP2ÐO21 179.6 (2)
52.9 (2) C1ÐC2ÐP2ÐO22 52.8 (2)
C1ÐC2ÐP2ÐO23 66.5 (2)
1
2
sheet in the domain 0 < y < and the
C1iiÐC1ÐP1ÐO3
61.4 (4) C2ÐC1ÐP1ÐO13 65.0 (2)
P1ÐC1ÐC2ÐP2 179.5 (2)
anion at (1 x; y; 1 z) is a com-
ponent of the sheet in the domain
12 < y < 0. Hence, these R46ꢂ12† rings link
Symmetry codes: (i) 1 x; 1 y; 1 z; (ii) 2 x; 1 y; z.
adjacent sheets, thus producing
a
continuous three-dimensional frame-
work. An alternative view of the frame-
12
as a donor to O12 at (x; y; z) (Table 2). In this manner a
Cꢂ7†‰R22(8)] chain of rings running parallel to [100] is gener-
ated by translation (Fig. 5). The conformation of the anion
(Table 3, Fig. 2) is almost centrosymmetric, with the reference
anion centred at approximately (0.75, 0.25, 0.30), and the R22ꢂ8†
rings are similarly almost centrosymmetric about (n + 0.25,
0.25, 0.30) (n = zero or an integer). However, a search for
possible additional symmetry showed that none was present
and, indeed, the disposition of the water molecules alongside
the anion chains effectively precludes this (Fig. 5). Four such
chains run through each unit cell along the approximate lines
(x, 0.25, 0.30), (x, 0.25, 0.80), (x, 0.75, 0.20) and (x, 0.75, 0.70),
and the chains are linked into a single continuum by means of
the water molecules. In total, six different OÐHÁ Á ÁO
hydrogen bonds are involved in these links, utilizing all the
donor capacity of the three independent water molecules.
The linking of the chains can itself be considered in two
steps: the water molecules containing O4 link the [100] chains
into (010) sheets, and the water molecules containing O3 and
O5 then together link the sheets into a three-dimensional
framework. Atom O11 in the anion at (x, y, z) is an acceptor of
an OÐHÁ Á ÁO hydrogen bond, via H41, from O4 at
(1 ‡ x; y; z): at the same time, O21 in the anion at
(x; 12 y; 12 ‡ z) accepts a hydrogen bond from the same water
molecule, via H42. O11 in the anion at (x; 12 y; 21 ‡ z) accepts
work is in terms of centrosymmetric R ꢂ48† rings (Fig. 7)
14
linked by R46ꢂ12† rings into (100) sheets and by [100] chains.
The anion/water framework encapsulates large cavities,
centred at the origin and at the A-face centres, which together
represent ca 58% of the unit-cell volume: for comparison, the
framework contains only half of the non-H atoms in the cell
and less than 40% of all the atoms. These cavities are occupied
by pairs of cations, each linked to the framework by four NÐ
HÁ Á ÁO hydrogen bonds and related to one another by centres
of inversion: these cations thus serve to cross-brace the anion/
water framework. Overall the structure contains no additional
solvent-accessible void space.
3.2.3. General comments on the supramolecular struc-
tures. The substructure approach which has proven so fruitful
in the descriptive analysis of other multicomponent structures
(Gregson et al., 2000; Glidewell et al., 2000) has demonstrated
the occurrence of a pillared-layer framework in (1). While this
architecture is reasonably familiar in inorganic systems such as
synthetic aluminosilicates, it is less common in organic mate-
rials. Nonetheless, several examples have recently been
reported: for example, in piperazine±squaric acid±water
(1/1/2), the squarate anions [C4O4]2 and the water molecules
form hydrogen-bonded sheets built from R68ꢂ24† rings, and
these sheets are linked by [H2N(CH2CH2)2NH2]2+ cations
(MacLean et al., 1999). Similarly in meso-5,5,7,12,12,14-
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100 Wheatley et al. Ethane-1,2-diphosphonic acid
Acta Cryst. (2001). B57, 95±102

research papers
Ê
hexamethyl-1,4,8,11-tetraazacyclotetradecane±3,5-dihydroxy-
benzoic acid (1/2) the dihydroxybenzoate anions
[(HO)2C6H3COO] are linked into sheets containing alter-
nating R22ꢂ14† and R46ꢂ30† rings, which are then linked by
[C16H38N4]2+ cations, while in meso-5,5,7,12,12,14-hexamethyl-
1,4,8,11-tetraazacyclotetradecane±4,40-biphenol (1/3), neutral
and anionic biphenol units form sheets, this time built from
R86ꢂ70† rings, again linked by [C16H38N4]2+cations (Gregson et
al., 2000).
In (2) the apparent complexity of the three-dimensional
hydrogen bonding, involving no fewer than 12 distinct inter-
actions (Table 2), can again be rather easily resolved using the
substructure approach with the initial identi®cation of a one-
dimensional motif comprising a single molecular component,
and building from this in steps towards the overall archi-
tecture. Some particularly elegant inorganic examples of the
use of such an approach have recently been reported (Haile &
Wuensch, 2000a,b). The two framework structures observed
for (1) and (2) are radically different, not only from one
another, but also from the framework structure found in the
related adduct ethane-1,2-diphosphonic acid±4,40-bipyridyl±
water (1/1/2). In this compound each of the individual
2.813 (4) and 2.816 (3) A. It is noteworthy that the ranges of
these three types do not overlap. The NÐHÁ Á ÁO hydrogen
bonds, likewise, can be divided into two categories. The
cationÁ Á Áanion interactions where both components are
charged all have very short NÁ Á ÁO distances, 2.635 (3)±
Ê
Ê
2.735 (3) A with mean 2.698 A, while the cationÁ Á Áwater
hydrogen bonds have NÁ Á ÁO distances 2.740 (3) and
Ê
2.800 (2) A; again these types are separable in terms of their
NÁ Á ÁO ranges. The pattern of the DÁ Á ÁA distances in both the
OÐHÁ Á ÁO and the NÐHÁ Á ÁO hydrogen bonds nicely
È
conforms to the expectation (Aakeroy & Seddon, 1993; Gilli et
al., 1994) that charged components will give short strong
hydrogen bonds. With the exception of the outlier O5Ð
H51Á Á ÁO3 interaction in (2), the pattern of the DÁ Á ÁA
distances closely follows that of the HÁ Á ÁA distances, re¯ecting
the near-linearity of the hydrogen bonds.
3.4. Molecular conformations and dimensions
The cations in (1) are centrosymmetric and thus are
constrained to adopt the chair conformation (Fig. 1). The rings
in the cation of (2) also adopt chair conformations with the
Ð(CH2)3Ð spacer unit occupying an equatorial site in each
ring: this spacer unit has the usual extended-chain confor-
mation. Indeed, there is a long sequence of CÐCÐCÐC
torsional angles of ca 180ꢁ de®ning a chain-extended sequence
from C12 to C26 (Fig. 2; Table 3). The torsional angles
C15ÐC14ÐC17ÐC18 and C18ÐC19ÐC24ÐC23, which
de®ne the location of the rings relative to this extended chain,
have similar magnitudes and the same sign, so that the cation
has approximately C2 symmetry.
components forms
a
one-component, one-dimensional
substructure and there are also two distinct two-component,
two-dimensional substructures, which together all build the
overall three-component, three-dimensional structure
(Glidewell et al., 2000).
3.3. Hydrogen-bond dimensions
In all of the hydrogen bonds (Table 2), the acceptor is O: all
have DÁ Á ÁA distances which are short for their types: in
addition, with the sole exception of the O5ÐH51Á Á ÁO3
hydrogen bond in (2), all of the DÐHÁ Á ÁA angles are greater
than 165ꢁ.
The anions in (1) are also centrosymmetric with the
PÐO(H) bond synclinal to CÐC: precisely the same centro-
The OÐHÁ Á ÁO hydrogen bonds can be divided into three
distinct categories. The anionÁ Á Áanion hydrogen bonds have
Ê
Ê
OÁ Á ÁO distances in the range 2.562 (3) A in (1) to 2.598 (2) A
Ê
in (2), with a mean value of 2.576 A; in the waterÁ Á Áanion
hydrogen bonds in (2), the OÁ Á ÁO distances range from
Ê
2.665 (2) to 2.802 (4) A with mean value 2.741 A; the two
Ê
waterÁ Á Áwater hydrogen bonds in (2) have OÁ Á ÁO distances
Figure 7
12
14
Part of the crystal structure of (2), showing one of the R ꢂ48† rings
Figure 6
bounding the cavities in the anion/water framework. For the sake of
clarity H atoms bonded to C are omitted. Atoms marked with a star (*),
hash (#), dollar ($), at (@) or ampersand (&) signs are at the symmetry
Part of the crystal structure of (2), showing one of the R46ꢂ12† rings linking
adjacent (010) sheets. For the sake of clarity H atoms bonded to C are
omitted. Atoms marked with a star (*) are at the symmetry position
positions 1 ‡ x; y; z; x; 12 y; 21 ‡ z;
1
x; 12 ‡ y; 23 z; 1 ‡ x; 12 y,
1
2
1
x; y; 1 z.
‡ z; x; 12 ‡ y; 32 z, respectively.
ꢀ
Acta Cryst. (2001). B57, 95±102
Wheatley et al. Ethane-1,2-diphosphonic acid 101

research papers
symmetric conformation was observed in the salt formed with
4,40-bipyridyl (Glidewell et al., 2000). Although the anions in
(2) lie in general positions, their conformation is close to
centrosymmetric (Table 3). In particular, the PÐCÐCÐP
torsional angle is close to 180ꢁ, and the two independent
PÐO(H) bonds are synclinal to CÐC and trans to one
another: the corresponding CÐCÐPÐO torsional angles for
the two phosphonate groups have similar magnitudes, but
opposite signs.
X-ray data were collected at the University of Toronto using
a Nonius Kappa-CCD diffractometer purchased with funds
from NSERC Canada.
References
È
Aakeroy, C. B. & Seddon, K. R. (1993). Chem. Soc. Rev. 22, 397±407.
Batten, S. R. & Robson, R. (1998). Angew. Chem. Int. Ed. 37,
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Acta Cryst. B54, 129±138.
The PÐO distances fall into two groups according to if the
O does or does not carry a proton: the values observed here
(Table 1) are comparable with those found in the salt formed
0
Ê
with 4,4 -bipyridyl, PÐO(H), 1.573 (2) A and PO2 , 1.509 (2)
Ê
and 1.522 (2) A. In the neutral acid (Peterson et al., 1977) the
Ê
PÐO(H) distances are 1.543 (2) and 1.533 (2) A, and the
Gabe, E. J., Le Page, Y., Charland, J.-P., Lee, F. L. & White. P. S.
(1989). J. Appl. Cryst. 22, 384±387.
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Gregson, R. M., Glidewell, C., Ferguson, G. & Lough, A. J. (2000).
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O distance is 1.501 (2) A. Very similar values are found
P
both in methylenediphosphonic acid (Peterson et al., 1977)
and in propane-1,3-diphosphonic acid (Gebert et al., 1977). All
of the PÐO bonds in the ethane-1,2-diphosphonate anion are
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diphosphonic acid.
Haile, S. M. & Wuensch, B. J. (2000a). Acta Cryst. B56, 335±348.
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4. Concluding comments
The three framework structures formed by ethane-1,2-diphos-
phonic acid with the two bis-secondary amines reported here,
and with 4,40-bipyridyl, reported earlier, are all dominated
by the hydrogen-bonding properties of the anion
[(HO)P(O)2CH2CH2P(O)2(OH)]2 , which is either strictly or
approximately centrosymmetric in all these compounds. This
suggests that rather different supramolecular architectures
must be expected in the corresponding adducts formed by
these amines with either methanediphosphonic acid or
propane-1,3-diphosphonic acid, since on both acids the
tetrahedral geometry at the central C atom necessarily
imposes a different molecular shape. Moreover, the structural
versatility of the diphosphonate anion manifested in the
present series of compounds indicates that further novel
structure types are to be expected in organic salts formed
from tri- and tetraphosphonic acids.
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& Peppard, D. F. (1977). J. Phys. Chem. 81, 466±471.
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102 Wheatley et al. Ethane-1,2-diphosphonic acid
Acta Cryst. (2001). B57, 95±102