The alkali hypophosphites KH2PO2, RbH 2PO4 and CsH2PO2

Article abstract of DOI:10.1107/S0108270104002409

The structures of the hypophosphites KH₂PO₂ (potassium hypophosphite), RbH₂PO₂ (rubidium hypophosphite) and CsH₂PO₂ (caesium hypophosphite) have been determined by single-crystal X-ray diff

Full text of DOI:10.1107/S0108270104002409

inorganic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
Previous crystal-structure investigations of anhydrous
hypophosphites include Ca(H2PO2)2 (Goedkoop & Loopstra,
1959), CaNa(H2PO2)3 (Matsuzaki & Iitaka, 1969), Cu(H2-
PO2)2 (Naumov et al., 2002), Zn(H2PO2)2 (Weakley, 1979;
Tanner et al., 1997), GeCl(H2PO2) (Catti, 1979) and SnCl-
(H2PO2) (Weakley & Watt, 1979), La(H2PO2)3 (Tanner et al.,
1999), Er(H2PO2)3 (Aslanov et al., 1975), and U(H2PO2)4
(Tanner et al., 1992). The limited number of studies is probably
due to the dif®culty of preparation of these compounds,
resulting from their highly hygroscopic nature and their low
stability. The title compounds are rather easy to synthesize but
crystals are dif®cult to grow.
ISSN 0108-2701
The alkali hypophosphites KH2PO2,
RbH2PO2 and CsH2PO2
Marina I. Naumova, Natalia V. Kuratieva, Nina V.
Podberezskaya and Dmitry Yu. Naumov*
The present crystal structure determinations show that the
unit cell of KH2PO2 differs in size and symmetry from those of
the isomorphous Rb and Cs analogues. The monoclinic unit
cell of KH2PO2 is related to the orthorhombic unit cell of the
Rb and Cs hypophosphites by the matrix (12 1 0 / 21 1 0 / 0 0 1).
Institute of Inorganic Chemistry, SB Russian Academy of Sciences, Academician
Lavrentiev Avenue 3, Novosibirsk 90, 630090 Russia
Correspondence e-mail: d.y.naumov@ngs.ru
Received 5 January 2004
Accepted 29 January 2004
Online 9 April 2004
The structures of the hypophosphites KH2PO2 (potassium
hypophosphite), RbH2PO2 (rubidium hypophosphite) and
CsH2PO2 (caesium hypophosphite) have been determined by
single-crystal X-ray diffraction. The structures consist of layers
of alkali cations and hypophosphite anions, with the latter
bridging four cations within the same layer. The Rb and Cs
hypophosphites are isomorphous.
Comment
The hypophosphite H2PO2 anion is a distorted tetrahedron,
with the P atom at the centre and two O and two H atoms at
the vertices. This anion may coordinate a metal cation via the
O atoms in different ways, viz. as a mono- or bidentate ligand,
or as a bridging ligand between two cations. The goal of the
present work was to investigate further the functional role of
the hypophosphite anion in the crystals of the title compounds.
Figure 2
The (001) layer in RbH2PO2. Displacement ellipsoids are plotted at the
50% probability level and H atoms are drawn as small spheres of
arbitrary radii.
Figure 1
The (010) layer in KH2PO2. Displacement ellipsoids are plotted at the
50% probability level and H atoms are drawn as small spheres of
arbitrary radii.
Figure 3
The coordination environment of the K+ cation in KH2PO2 [symmetry
codes: (i) + x, 12 y, 21 + z; (ii) 21 x, y
,
z; (iii) 1 + x, y, z].
1
1 1
2 2
2
Acta Cryst. (2004). C60, i53±i55
DOI: 10.1107/S0108270104002409
# 2004 International Union of Crystallography i53

inorganic compounds
Compound (I)
Crystal data
KH2PO2
Mr = 104.09
Monoclinic, C2=c
Mo Kꢁ radiation
Cell parameters from 22
re¯ections
ꢂ = 9.0±14.7ꢁ
Ê
a = 7.3131 (10) A
1
Ê
b = 7.2952 (8) A
ꢃ = 1.78 mm
T = 296 (2) K
Ê
c = 7.1814 (10) A
ꢀ = 116.205 (10)ꢁ
Plate, colourless
0.59 Â 0.46 Â 0.06 mm
3
Ê
V = 343.75 (8) A
Z = 4
Dx = 2.011 Mg m
3
Data collection
Figure 4
Enraf±Nonius CAD-4
diffractometer
2ꢂ/ꢂ scans
Absorption correction: empirical
(CADDAT; Enraf±Nonius, 1989)
Tmin = 0.421, Tmax = 0.903
606 measured re¯ections
500 independent re¯ections
458 re¯ections with I > 2ꢄ(I)
Rint = 0.020
ꢂmax = 29.9ꢁ
The coordination environment of the Rb+ cation in RbH2PO2 [symmetry
1
1
1
1
1
3
codes: (i) x
,
y, 12 z; (ii)
x, y
,
+ z; (iii) x,
2
y z].
2
2
2
2
2
h = 0 ! 10
k = 1 ! 10
l = 10 ! 9
3 standard re¯ections
frequency: 60 min
intensity decay: none
All three compounds adopt layer structures, in which the
metal cations are coordinated by hypophosphite anions (Figs. 1
and 2). The packing of the cations and P atoms is identical in
all three compounds, and the cations and P-atom positions are
nearly coplanar, forming a layer similar to a (100) NaCl layer.
The full coordination environments of the K+ and Rb+
cations are shown in Figs. 3 and 4, respectively. The Rb and Cs
environments are identical to those found in KF2PO2,
RbF2PO2 and CsF2PO2 (Harrison et al., 1966; Granier et al.,
1975; Trotter & Withlow, 1967). The H-atom positions in the
present hypophosphites correspond to the F-atom positions in
the di¯uorophosphates.
Re®nement
Re®nement on F2
R[F2 > 2ꢄ(F2)] = 0.031
wR(F2) = 0.079
S = 1.14
500 re¯ections
w = 1/[ꢄ2(Fo2) + (0.0549P)2]
where P = (Fo2 + 2Fc2)/3
(Á/ꢄ)max < 0.001
3
Ê
Áꢅmax = 0.50 e A
3
Ê
0.59 e A
Áꢅmin
=
25 parameters
All H-atom parameters re®ned
Extinction correction: SHELXL97
(Sheldrick, 1997)
Extinction coef®cient: 0.075 (8)
Experimental
Compound (II)
It was established during crystal-growth experiments that the
preparation of anhydrous hypophosphites of K, Rb and Cs from
aqueous solutions depends on the precursor and on the presence of
impurities in that precursor at levels of less than 3±5%. Crystals of the
title K, Rb and Cs hypophosphites were grown from aqueous solu-
tions prepared by the reaction of hypophosphorous acid with the
corresponding alkali carbonates. Crystal growth was carried out at
313 K in a dry-box under dry nitrogen. Crystal growth is not possible
at room temperature in air because of the strong hygroscopic
nature of the hypophosphites and the tendency of the crystals to
dissolve as a result of the fast absorption of water vapour from the
atmosphere (increasing in the order K ! Rb ! Cs). The crystals
were protected from moisture by coating them with epoxy resin.
Powder diffraction analysis shows agreement between the bulk
products and the single crystals. However, in the case of the
rubidium hypophosphite, the presence of additional peaks in the
powder pattern shows the presence of an additional phase similar
to potassium hypophosphite.
Crystal data
RbH2PO2
Mr = 150.46
Mo Kꢁ radiation
Cell parameters from 24
re¯ections
Orthorhombic, Pnma
Ê
a = 7.9835 (9) A
ꢂ = 9.9±14.2ꢁ
1
Ê
b = 6.3678 (7) A
ꢃ = 13.06 mm
T = 298 (2) K
Ê
c = 7.5755 (11) A
Ê
V = 385.12 (8) A
Z = 4
Dx = 2.595 Mg m
3
Plate, colourless
0.32 Â 0.16 Â 0.04 mm
3
Data collection
Enraf±Nonius CAD-4
diffractometer
2ꢂ/ꢂ scans
Absorption correction: empirical
(CADDAT; Enraf±Nonius, 1989)
Tmin = 0.095, Tmax = 0.593
732 measured re¯ections
366 independent re¯ections
289 re¯ections with I > 2ꢄ(I)
Rint = 0.032
ꢂmax = 24.9ꢁ
h = 9 ! 9
k = 0 ! 7
l = 0 ! 9
3 standard re¯ections
frequency: 60 min
intensity decay: none
Table 1
Selected geometric parameters (A, ) for (I).
ꢁ
Ê
Re®nement
KÐO
KÐOi
KÐOii
2.7747 (14)
2.7368 (13)
2.9220 (15)
PÐO
PÐH
1.4914 (12)
1.28 (3)
Re®nement on F2
R[F2 > 2ꢄ(F2)] = 0.023
wR(F2) = 0.057
S = 0.96
All H-atom parameters re®ned
w = 1/[ꢄ2(Fo2) + (0.026P)2]
where P = (Fo2 + 2Fc2)/3
(Á/ꢄ)max < 0.001
OÐPÐOiii
OÐPÐH
118.04 (11)
108.3 (10)
OiiiÐPÐH
HÐPÐHiii
109.8 (11)
101.(2)
3
Ê
366 re¯ections
27 parameters
Áꢅmax = 0.58 e A
3
1
2
x; 12 y; z; (ii) 21 ‡ x; y 21; z; (iii) x; y; 12 z.
Ê
0.58 e A
Áꢅmin
=
Symmetry codes: (i)
ꢀ
i54 Marina I. Naumova et al.
KH2PO2, RbH2PO2 and CsH2PO2
Acta Cryst. (2004). C60, i53±i55

inorganic compounds
Table 2
Selected geometric parameters (A, ) for (II).
Table 3
Selected geometric parameters (A, ) for (III).
ꢁ
ꢁ
Ê
Ê
RbÐO
RbÐOi
RbÐOii
2.859 (3)
2.932 (3)
3.063 (3)
PÐO
PÐH1
PÐH2
1.478 (3)
1.18 (7)
1.33 (7)
CsÐO
CsÐOi
CsÐOii
3.026 (5)
3.094 (5)
3.221 (7)
PÐO
PÐH1
PÐH2
1.487 (6)
1.37 (11)
1.48 (12)
OÐPÐOiii
OÐPÐH1
118.7 (3)
111.9 (13)
OÐPÐH2
H1ÐPÐH2
107.4 (13)
97.(4)
OÐPÐOiii
OÐPÐH1
118.1 (5)
107.(2)
OÐPÐH2
H1ÐPÐH2
108.(2)
108.(7)
1
2
1
2
1
2
1
2
Symmetry codes: (i) ‡ x; 12 y; 21 z; (ii) 1 x; y
;
z; (iii) x; 32 y; z.
Symmetry codes: (i) ‡ x; 12 y; 21 z; (ii) 1 x; y
;
z; (iii) x; 32 y; z.
Compound (III)
The authors are grateful to Dr A. V. Virovets for helpful
comments. An initial report (Naumova et al., 2004) on the
synthesis, growth conditions and crystal chemistry analysis of
the three title compounds was presented at the National
Conference on Crystal Growth (NCCG-2002, Moscow).
Crystal data
CsH2PO2
Mr = 197.90
Mo Kꢁ radiation
Cell parameters from 24
re¯ections
Orthorhombic, Pnma
Ê
a = 8.3776 (9) A
ꢂ = 9.5±13.7ꢁ
1
Ê
b = 6.6271 (6) A
ꢃ = 8.61 mm
T = 298 (2) K
Ê
c = 7.9165 (10) A
Ê
V = 439.52 (8) A
Z = 4
Dx = 2.991 Mg m
3
Plate, colourless
0.45 Â 0.30 Â 0.11 mm
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: BC1035). Services for accessing these data are
described at the back of the journal.
3
Data collection
Enraf±Nonius CAD-4
diffractometer
2ꢂ/ꢂ scans
Absorption correction: empirical
(CADDAT; Enraf±Nonius, 1989)
Tmin = 0.056, Tmax = 0.388
769 measured re¯ections
687 independent re¯ections
554 re¯ections with I > 2ꢄ(I)
Rint = 0.058
ꢂ
max = 29.9ꢁ
References
h = 1 ! 11
k = 0 ! 9
Aslanov, L. A., Ionov, V. M., Poray-Koshits, M. A., Lebedev, V. G., Kulikovskij,
B. N., Gilyarov, O. N. & Novoderzhkina, T. L. (1975). Neorg. Mater. 11, 117±
119. (In Russian.)
Burnett, M. N. & Johnson, C. K. (1996). ORTEPIII. Report ORNL-6895. Oak
Ridge National Laboratory, Tennessee, USA.
Catti, M. (1979). Acta Cryst. B35, 1041±1046.
l = 0 ! 11
3 standard re¯ections
frequency: 60 min
intensity decay: none
Enraf±Nonius (1989). CD4CA0 (Version 5.0) and CADDAT (Version 5.1).
Enraf±Nonius, Delft, The Netherlands.
Goedkoop, J. A. & Loopstra, L. H. (1959). Ned. Tijdschr. Natuurkd. 25, 29±41.
Granier, W., Durand, J., le Cot, L. & Galigne, J. L. (1975). Acta Cryst. B31,
2506±2507.
Re®nement
Re®nement on F2
R[F2 > 2ꢄ(F2)] = 0.037
wR(F2) = 0.114
S = 1.04
687 re¯ections
w = 1/[ꢄ2(Fo2) + (0.07P)2]
where P = (Fo2 + 2Fc2)/3
(Á/ꢄ)max < 0.001
3
Ê
Harrison, R. W., Thompson, R. C. & Trotter, J. (1966). J. Chem. Soc. A, pp.
1775±1780.
Áꢅmax = 1.41 e A
3
Ê
1.06 e A
Áꢅmin
=
Matsuzaki, T. & Iitaka, Y. (1969). Acta Cryst. B25, 1932±1938.
Naumov, D. Y., Naumova, M. I., Kuratieva, N. V., Boldyreva, E. V. & Howard,
J. A. K. (2002). Acta Cryst. C58, i55±i60.
27 parameters
All H-atom parameters re®ned
Extinction correction: SHELXL97
(Sheldrick, 1997)
Extinction coef®cient: 0.050 (4)
Naumova, M. I., Kuratieva, N. V., Naumov, D. Yu. & Podberezskaya, N. V.
(2004). Crystallogr. Rep. 46, 282±287.
Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of
The H atoms were located from difference electron-density maps
and their positions were re®ned without any constraint.
For all compounds, data collection: CD4CA0 (Enraf±Nonius,
1989); cell re®nement: CD4CA0; data reduction: CADDAT (Enraf±
Nonius, 1989); program(s) used to solve structure: SHELXS97
(Sheldrick, 1997); program(s) used to re®ne structure: SHELXL97
(Sheldrick, 1997); molecular graphics: ORTEPIII (Burnett &
Johnson, 1996); software used to prepare material for publication:
SHELXL97.
È
Gottingen, Germany.
Tanner, P. A., Faucher, M. D. & Mak, T. C. W. (1999). Inorg. Chem. 38, 6008±
6023.
Tanner, P. A., Sze, T. H., Mak, T. C. W. & Yip, W. H. (1992). J. Crystallogr.
Spectrosc. Res. 22, 25±30.
Tanner, P. A., Yu-Long, L. & Mak, T. C. W. (1997). Polyhedron, 16, 495±505.
Trotter, J. & Withlow, S. H. (1967). J. Chem. Soc. A, pp. 1383±1386.
Weakley, T. J. R. (1979). Acta Cryst. B35, 42±45.
Weakley, T. J. R. & Watt, W. W. L. (1979). Acta Cryst. B35, 3023±3024.
ꢀ
Acta Cryst. (2004). C60, i53±i55
Marina I. Naumova et al.
KH2PO2, RbH2PO2 and CsH2PO2 i55