organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
130 K, R > 0.06),noted a smooth lengthening of the OÐH
distances of the donors with a shortening of the OÁ Á ÁO
distance. Although their data set contained no instances of
hydrogen bonds across symmetry elements, they found a
ISSN 0108-2701
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minimum OÁ Á ÁO distance of ca 2.39 A, with equal OÐH and
HÁ Á ÁO distances at that distance. Thus, the symmetric
hydrogen bonds observed in (I) are in accordance with their
®ndings. In (I), the P1ÐO3 and P2ÐO5 distances (Table 1) to
O atoms involved in the symmetric hydrogen bonds are
Symmetric hydrogen bonding in
dimethylammonium hydrogen
diphenyldiphosphonate
intermediate in length between the
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P
O
distance
[1.506 (2) A] and the PÐOH distances [1.536 (2) and
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1.554 (2) A] in benzenephosphonic acid (Mahmoudkhani &
Langer, 2002).
Brandy H. Courtney, Booker W. O. Juma, Steven F.
Watkins,* Frank R. Fronczek and George G. Stanley
The four remaining O atoms, viz. O2, O4 and their
symmetry equivalents, accept hydrogen bonds from two
cations on either side of the plane. The P O distances are
typical of double bonds (Corbridge, 1974).
Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803-1804,
USA
Correspondence e-mail: swatkins@lsu.edu
The structure of the same dimerized anion has been
reported at 213 K, with a complex palladium cation (Kingsley
et al., 2001), but with asymmetric ordered hydrogen bonds
Received 8 February 2006
Accepted 14 March 2006
Online 13 April 2006
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[OÁ Á ÁO = 2.424 (3) A]. That dimer lies on an inversion center
In the title compound, C2H8N+ÁC12H11O5P2 , pairs of
hydrogen diphenyldiphosphonate anions form dimers across
a twofold axis, with two symmetric OÁ Á ÁHÁ Á ÁO hydrogen
rather than a twofold axis, so that symmetry does not require
either disorder of the H-atom positions or a symmetric
hydrogen bond. In the presence of palladium, uncertainties in
H-atom positions are rather large; the reported OÐH distance
is 1.02 (6) A and the HÁ Á ÁO distance is 1.43 (6) A. Thus, the
deviation of the H-atom position from the OÁ Á ÁO mid-point is
of marginal statistical signi®cance, and that hydrogen bond
may approach the apparently symmetric one observed in the
title compound.
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bonds [OÁ Á ÁO = 2.406 (3) and 2.418 (3) A]. The 12-membered
ring thus formed has crystallographic 2 and quasi-222
symmetry. Cations on either side of the ring form NÐHÁ Á ÁO
hydrogen bonds to the four extraannular O atoms, with NÁ Á ÁO
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distances of 2.765 (2) and 2.748 (3) A.
Comment
As part of our interest in preparing and characterizing brid-
ging methylene±phosphine complexes, the title compound, (I),
was isolated during the synthesis of Ph(H)PCH2P(H)Ph by
Stelzer's reaction (Langhans & Stelzer, 1987), during which
the order of addition of dimethylformamide and water was
reversed.
The chemically signi®cant species, [(CH3)2NH2]2[(C6H5)2-
P2O5H]2, consists of two hydrogen diphenyldiphosphonate
anions fused into a P4O6H2 ring by two short hydrogen bonds
(Fig. 1 and Table 2), both apparently symmetric, with their H
atoms centrally located on a twofold axis. While we cannot
rule out the possibility that these hydrogen bonds involve
disordered H atoms, with half-occupied sites slightly off the
twofold axis, difference maps (see Fig. 2) show no elongation
of the density along the OÁ Á ÁO lines. The OÐH distances are
Figure 1
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quite long, approximately 1.2 A. Steiner & Saenger (1994), by
The structure of (I), showing the atomic numbering scheme and
displacement ellipsoids at the 50% probability level. Dashed lines
indicate hydrogen bonds.
examining OÐHÁ Á ÁO hydrogen-bonded structures deter-
mined from low-temperature neutron-diffraction data (T <
o268 # 2006 International Union of Crystallography
DOI: 10.1107/S0108270106009528
Acta Cryst. (2006). C62, o268±o270
Courtney, Brandy H.
