The trimetaphosphimate anion (PO2NH)33- in trisodium cyclo-tri--imidotriphosphate monohydrate, Na3(PO2NH)3.H2O, exhibits a chair conformation. Two trimetaphosphimate rings are linked to each other by six N-HO hydrogen bonds forming pairs. These units are interconnected by O-HO hydrogen bonds through water molecules forming columns

Schnick, Wolfgang

Stock, Norbert

English

Open Access LMU

532 /~-BaTbF6 References Enraf-Nonius (1989). CAD-4 Software. Version 5.0. Enraf-Nonius, Delft, The Netherlands. Fair, C. K. (1990). MolEN. An Interactive Intelligent System for Crystal Structure Analysis. Enraf-Nonius, Delft, The Netherlands. Feldner, K. & Hoppe, R. (1983). Rev. Chim. Miner. 20, 351-367. Gibson, J. K. & Haire, R. G. (1988). J. SolidState Chem. 73, 524-530. Hoppe, R. (1985). High Oxidation States in Fluorine Chemistry. InInorganic Solid Fluorides, Chemistry and Physics, edited by P. Hagenmuller. San Diego: Academic Press. Johnson, C. K. (1965). ORTEP. Report ORNL-3794. Oak Ridge National Laboratory, Tennessee, USA. Mehlhorn, B. & Hoppe, R. (1976). Z. Anorg. Allg. Chem. 425, 180- 188. North, A. C. T., Phillips, D. C. & Mathews, F. S. (1968). Acta Cryst. A24, 351-359. Shannon, R. D. & Prewitt, C. T. (1969). Acta Cryst. B25, 925-946. Stout, G. H. & Jensen, L. H. (1968). X-ray Structure Determination: A Practical Guide, p. 412. New York: Macmillan. Acta Cryst. (1997). C53, 532-534 Trisodium Trimetaphosphimate Mono- hydrate NORBERT STOCK AND WOLFGANG SCHNICK Laboratorium fiir Anorganische Chemie der Universitiit, Universitiitsstrasse 30, D-95440 Bayreuth, Germany. E-mail: wolfgang.schnick@ uni-bayreuth.de (Received 10 October 1996; accepted 10 December 1996) Abstract The trimetaphosphimate nion (PO2NH)~- in trisodium cyclo-td-#-imido-triphosphate monohydrate, Na3(PO2- NH)3.H20, exhibits a chair conformation. Two trimeta- phosphimate ings are linked to one another by six N--  H.-.O hydrogen bonds forming pairs. These units are interconnected by O---H...O hydrogen bonds through water molecules forming columns. Comment In contrast to the well known structural chemistry of tfimetaphosphates (Durif, 1995), only very few structural details about trimetaphosphimates are known despite the fact that many salts of trimetaphos- phimic acid were known more than 100 years ago (Stokes, 1895). These compounds have been mainly characterized by IR spectroscopy (Pustinger, Cave & Nielsen, 1959) and powder diffraction (Herzog & Nielsen, 1958). In contrast o H3(PO2NH)3.2H20 and (NH4)H2(PO2NH)3.CH3OH , where the P-N rings show a distorted boat conformation (Olthof, Migchelsen & Vos, 1965), the title compound, (I) (Fig. 1), © 1997 International Union of Crystallography Printed in Great Britain - all rights reserved Na3(PO2NH)3.4H20 and (NHn)3(PO2NH)3.H20 exhibit distorted chair conformations (Attig & Mootz, 1976; Stock & Schnick, 1996). H 0,. /N '~_ jO  o "e P '~o 3Na + I -J" HN p./NH o'o (1) 73- .H20 As may be seen from the bond lengths and valence angles, the phosphimate ring in Na3(PO2NH)3.H20 exhibits approximate 3m symmetry. Whereas in (NH4)3(PO2NH)3.H20 and Na3(PO2NH)3.4H20, three- dimensional networks of (PO2NH)~- anions and water molecules are formed by NmH..-O and O---H...O hydrogen bonds, in Na3(PO2NH)3.H20, rings are linked pairwise to one another by six NmH.. .O bonds [N.-.O 2.964(2), 3.053(2) and 3.121 (2),A]. These units are 028 O3B ® N~ Na4 Fig. I. The structure of (I) showing 50% probability displacement ellipsoids. H atoms are drawn as small circles of arbitrary size. Fig. 2. View along [001] of the crystal packing of the trimetaphos- phimate rings and water molecules illustrating the hydrogen bonds. The sodium ions have been omitted for clarity. Acta C~.stallographica Section C ISSN 0108-2701 © 1997 NORBERT STOCK AND WOLFGANG SCHNICK 533 interconnected by water molecules through O- -H . - -O  o hydrogen bonds [O . . .O  2 .689(2)  and 2 .720(2)A] ,  thereby forming co lumns (Fig. 2). The sodium ions are approximately octahedraUy coordinated by six O atoms f rom the phosphimate groups and from the water mol-  ecules [Na-. -O 2.282 (2) -2.984 (2) ,~]. PI P2 P3 Nal Exper imenta l  Na2 Na3 The starting material, Na3(PO2NH)3.4H20, was obtained Na4 according to Nielsen & Morrow (1960) by reaction (12h, OIA 323 K) of 3 g Na(OOCCH3).3H20 in 48 ml water with 6 g OlB (PNC12)3 in 24ml dioxane. Whereas the authors claim the O2A 02B synthesis of (I) under these conditions, Na3(PO2NH)3.4H20 O3A is formed. Sodium trimetaphosphimate monohydrate was 03B prepared by a method similar to that of Stokes (1896); single O4A crystals of (I) of up to 5 mm in length were grown by vapour 04B NI diffusion of CH3CH2OH at 363 K into a 3 × 10-4M aque- N2 ous solution of Na3(PO2NH)3.4H20. These crystals are stable N3 in air under ambient conditions. According to DSC mea- surements, decomposition starts at approximately 450 K with evolution of NH3 and H20. Crystal data Na3(PO2NH)3.H20 Mo/Ca radiation Mr = 320.95 A = 0.71073 A Monoclinic Cell parameters from 69 C2 reflections a = 9.8797 (7) ~, 0 = 5.41-17.43 ° b = 12.2119 (8)oA # = 0.836 nun -~ c = 7.6464 (6) A T = 173 (2) K /3 = 104.394 (6) ° Column V = 893.58 (11)/~3 0.26 x 0.08 x 0.06 mm Z = 4 Colourless Dx = 2.386 Mg m -3 Dm not measured Data collection Siemens P4 diffractometer o) scans  Absorption correction: empirical via ~b scans using XSCANS (Siemens, 1994) and SHELXTL-PIus (Sheldrick, 1994) Tmin = 0.866, Tma~ = 0.951 5209 measured reflections 2616 independent reflections 2259 reflections with I > 20-(/) Rint = 0.0367 0max = 30 ° h- - -13- -~ 13 k=-17- -+ 17 l=- lO- -~ 10 3 standard reflections every 97 reflections intensity decay: 5.24% Refinement Refinement on F 2 R(F) = 0.0311 wR(F 2) = 0.0663 S = 1.031 2616 reflections 152 parameters H atoms were refined using a riding model, starting from Fourier coordinates w = 1/[0.2(Fo 2) + (0.0311P) 2] where P = (Fo 2 + 2F~)/3 (A/0. )max = 0.001 Apmax = 0.40 e ,~-3 Apmin = -0 .32 e ,~-3 Extinction correction: none Scattering factors from International Tables for Crystallography (Vol. C) Absolute configuration: Flack (1983) Flack parameter = 0.34 (12) Table 1. Fractional atomic coordinates and equivalent isotropic displacement parameters (1~ 2) Ueq = (1/3)~i~jUiJa~ a~ai.aj. x y z Ueq 0.77111 (6) 0.61560 (8) 0.15493 (8) 0.00777 (12) 0.64506 (9) 0.74470 (6) -0.17148 (10) 0.0075 (2) 0.63899 (9) 0.50337 (6) -0.19318 (I1) 0.0082 (2) 0.87932 (10) 0.62554 (14) 0.61559 (13) 0.0119 (2) 1 0.7710 (2) 0 0.0142 (4) 1 0.4687 (2) 0 0.0175 (5) 0.72100 (14) 0.41584 (10) -0.5720 (2) 0.0186 (3) 0.9208 (2) 0.6179 (2) 0.1454 (2) 0.0103 (3) 0.7368 (2) 0.6037 (2) 0.3330 (2) 0.0120 (4) 0.7745 (3) 0.7624 (2) -0.2368 (3) 0.0117 (5) 0.5343 (3) 0.8306 (2) -0.2080 (3) 0.0125 (5) 0.7623 (3) 0.4839 (2) -0.2697 (3) 0.0132 (5) 0.5215 (3) 0.4204 (2) -0.2342 (3) 0.0118 (5) 1 0.7685 (3) i/2 0.0154 (7) 1 0.4603 (3) I/2 0.0188 (8) 0.6920 (3) 0.7271 (2) 0.0529 (3) 0.0088 (5) 0.5710 (2) 0.6269 (3) -0.2573 (3) 0.0086 (4) 0.6928 (3) 0.5092 (2) 0.0300 (3) 0.0098 (5) Table 2. Selected geometric parameters (A, o) Pi---O1B 1.490 (2) P2--N2 1.673 (3) PI---OIA 1.499 (2) P2--NI 1.676 (3) PI--N1 1.665 (3) P3--O3A 1.496 (3) PI--N3 1.682 (3) P3~3B 1.514 (2) P2---O2B 1.492 (3) P3--N3 1.658 (3) P2---O2A 1.499 (3) P3--N2 1.674 (3) OIB--PI--4)IA 119.83 (I0) N2--P2--NI 105.92 (13) OIB--PI--NI 108.76 (13) O3A--P3---O3B 117.99 (14) OIA--PI--N! 108.38 (15) O3A--P3--N3 109.0 (2) OIB--PI--N3 105.46 (14) O3B--P3--N3 105.98 (14) OIA--PI--N3 107.9 (2) O3A--P3--N2 109.61 (12) NI--PI--N3 105.63 (10) O3B--P3--N2 108.12 (14) O2B--P2--O2A 118.87 (14) N3--P3--N2 105.38 (13) O2B--P2--N2 107.60 (14) PI--N1--P2 124.3 (2) O2A--P2--N2 108.64 (12) P2--N2--P3 123.72 (12) O2B--P2--N i 106.59 (14) P3--N3--PI 127.0 (2) O2A--P2--N 1 108.49 (14) Since the title compound crystallizes in a polar space group, polar axis restraints were applied according to the method of Flack & Schwarzenbach (1988) and the absolute structure of the crystal used for the investigation was established as described by Flack (1983). Linear decay was observed uring the data collection and a correction was included in the data reduction procedure using SHELXTL-PIus (Sheldrick, 1994). All H atoms were unambiguously located after the anisotropic refinement of all non-H atoms. The w-scan width was 1.2 °, with an w-scan rate of 3.0 ° min -I . The background to signal ratio was 0.5. Data collection: XSCANS (Siemens, 1994). Cell refinement: XSCANS. Data reduction: SHELXTL-PIus. Program(s) used to solve structure: SHELXS86 (Sheldrick, 1990). Program(s) used to refine structure: SHELXL93 (Sheldrick, 1993). Molecular graphics: SHELXTL-PIus. Software used to prepare material for publication: SHELXTL-PIus. Financial  support by the Deutsche Forschungsgemein-  schaft (project SCHN 377/6-1 and the Gottfr ied Wi lhe lm Leibniz program) and the Fonds der Chemischen Indus- trie is gratefully acknowledged.  534 Na3 0aO2NH)3.H20 Lists of atomic oordinates, displacement parameters, tructure factors and complete geometry have been deposited with the IUCr (Reference: BMIll9). Copies may be obtained through The Managing Editor, International Union of Crystallography, 5 Abbey Square, Chester CH 1 2HU, England. References Attig, R. & Mootz, D. (1976). Z. Anorg. Allg. Chem. 419, 139-156. Durif, A. (1995). In Crystal Chemistry of Condensed Phosphates. New York: Plenum Press. Flack, H. D. (1983). Acta Cryst. A39, 876-881. Flack, H. D. & Schwarzenbach, D. (1988). Acta Cryst. A44, 499-506. Herzog, A. H. & Nielsen, M. L. (1958). Anal. Chem. 30, 1490-1496. Nielsen, M. L. & Morrow, T. J. (1960). lnorg. Synth. 6, 99. Olthof, R., Migchelsen, T. & Vos, A. (1965). Acta Cryst. 19, 596-603. Pustinger, J. V., Cave, W. T. & Nielsen, M. L. (1959). Spectrochim. Acta, 11, 909-925. Sheldrick, G. M. (1990). Acta Cryst. A46, 467--473. Sheldrick, G. M. (1993). SHELXL93. Program for the Refinement of Crystal Structures. University of Gtttingen, Germany. Sheldrick, G. M. (1994). SHELXTL-Plus. Release 5.03. Siemens Analytical X-ray Instruments Inc., Madison, Wisconsin, USA. Siemens (1994). XSCANS Users Manual. Version 2.1. Siemens Analytical X-ray Instruments Inc., Madison, Wisconsin, USA. Stock, N. & Schnick, W. (1996). Acta Cryst. C52, 2645-2647. Stokes, H. N. (1895). Ber. Dtsch Chem. Ges. 28, 437. Stokes, H. N. (1896). Am. Chem. J. 18, 629-663. Acta Cryst. (1997). C53, 534-536 Strontium Metasilicate, SrSiO3 FtJMrro NISH1 Saitama Institute of Technology, Fusaiji 1690, Okabe, Ohsato-gun, Saitama 369-02, Japan. E-mail: nishi@sit. ac.jp (Received 11 September 1996; accepted 11 December 1996) Abstract Strontium silicon trioxide has been synthesized for the first time and its structure solved. It is isostructural with the germanium analogue SrGeO3 reported by Hilmer [Soy. Phys. Crystallogr. (1963), 7, 573-576], but the true symmetry is monoclinic, rather than hexagonal as reported earlier. The structure has alternate layers of ternary rings of SiO4 groups and close-packed Sr atoms stacked along [001]. Viewed as a polytype, this compound has a six-layer structure and the calcium analogue a-CaSiO3 [Yamanaka & Mori (1981). Acta Cryst. B37, 1010-1017] has a four-layer structure. Comment The title compound has been synthesized for the first time. Dornberger-Schiff (1962) discussed the symmetry © 1997 International Union of Crystallography Printed in Great Britain - all fights reserved of the analogous germanium compound SrGeO3. Hilmer (1963) studied the structure of SrGeO3 using a Weis- senberg camera. He obtained the hexagonal lattice pa- rameters a - 7.29, c = 31.64,~ and showed that the structure contained ternary rings of GeO4 groups. In addition, he concluded that the structure was composed of alternating layers of [Ge309] 6-  r ings and layers of Sr atoms. Nadezhina, Pobedimskaya, Ilyukhin & Belov (1981a,b) also studied SrGeO3 and obtained the triclinic lattice parameters a = 8.699, b = 9.935, c -- 11.148,~,, a = 106.04,/3 = 89.97, 3' = 102.11 °. This structure also contained rings of GeO4 groups. The configurations of the rings, however, were somewhat different from those in the study by Hilmer, and Nadezhina et al. stated that the different ypes of ternary rings in the two modifica- tions of strontium metagermanate w re undoubtedly the result of a difference in the structures of the cation lay- ers. In addition, they called the form they had studied the low-temperature form (a'-SrGeO3) and the form studied by Hilmer the high-temperature form (a-SrGeO3). Ito (1950) and Buerger & Prewitt (1961) discussed the analogous calcium compound CaSiO3 (the high- pressure form). Trojer (1969) obtained the triclinic lattice parameters a - 6.695, b = 9.257, c = 6.666,~, = 86.5, /3 = 76.13, 3' = 70.38 ° and solved its structure. He concluded that the basic features of this structure were irregular layers of Ca atoms, which were interconnected by pairs of Ca atoms, and Si309 rings, which were located in the remaining space between the layers. Yamanaka & Mori (1981) studied the structure of a-CaSiO3 (pseudowollastonite) from the viewpoint of polytypism. In their definition, a layer comprises one layer of the ternary rings plus one layer of CaO8 polyhedra. They concluded that c~-CaSiO3 has a four- layer structure and the form of SrGeO3 studied by Hilmer has a six-layer structure. The symmetry of the title compound, SrSiO3, was found to be different not only to that of the form of SrGeO3 studied by Hilmer but also to that of the form of SrGeO3 studied by Nadezhina et al. SrSiO3, however, is almost isostructural with the form of SrGeO3 studied by Hilmer for two reasons. Firstly, SrSiO3 has a pseudo- hexagonal cell which corresponds to the cell given by Hilmer. Secondly, all of the reflections observed by Hilmer can be indexed on the basis of the present monoclinic cell. On the contrary, the structure of SrGeO3 reported by Nadezhina et al. is different. It can be concluded that there are two forms of SrGeO3, but only one form of SrSiO3 is known so far. The arrangement of the ternary rings of SiO4 groups and SrO8 polyhedra is shown in Fig. 1. The polyhedron around Sr(1) is very irregular, but that around Sr(2) can be regarded as a distorted hexagonal bipyramid, with O(1) on either side of the hexagon. The SrO8 polyhedra form a close-packed layer like the olivine structure. The layers of the ternary rings of SiO4 groups and the layers of SrO8 polyhedra re shown in Fig. 2. They are stacked Acta Crystallographica Section C ISSN 0108-2701 © 1997 

Trisodium Trimetaphosphimate Monohydrate

Universität München: Elektronischen Publikationen

532 /~-BaTbF6 
References 
Enraf-Nonius (1989). CAD-4 Software. Version 5.0. Enraf-Nonius, 
Delft, The Netherlands. 
Fair, C. K. (1990). MolEN. An Interactive Intelligent System for 
Crystal Structure Analysis. Enraf-Nonius, Delft, The Netherlands. 
Feldner, K. & Hoppe, R. (1983). Rev. Chim. Miner. 20, 351-367. 
Gibson, J. K. & Haire, R. G. (1988). J. SolidState Chem. 73, 524-530. 
Hoppe, R. (1985). High Oxidation States in Fluorine Chemistry. In 
Inorganic Solid Fluorides, Chemistry and Physics, edited by P. 
Hagenmuller. San Diego: Academic Press. 
Johnson, C. K. (1965). ORTEP. Report ORNL-3794. Oak Ridge 
National Laboratory, Tennessee, USA. 
Mehlhorn, B. & Hoppe, R. (1976). Z. Anorg. Allg. Chem. 425, 180- 
188. 
North, A. C. T., Phillips, D. C. & Mathews, F. S. (1968). Acta Cryst. 
A24, 351-359. 
Shannon, R. D. & Prewitt, C. T. (1969). Acta Cryst. B25, 925-946. 
Stout, G. H. & Jensen, L. H. (1968). X-ray Structure Determination: 
A Practical Guide, p. 412. New York: Macmillan. 
Acta Cryst. (1997). C53, 532-534 
Trisodium Trimetaphosphimate Mono- 
hydrate 
NORBERT STOCK AND WOLFGANG SCHNICK 
Laboratorium fiir Anorganische Chemie der Universitiit, 
Universitiitsstrasse 30, D-95440 Bayreuth, Germany. E-mail: 
wolfgang.schnick@ uni-bayreuth.de 
(Received 10 October 1996; accepted 10 December 1996) 
Abstract 
The trimetaphosphimate anion (PO2NH)~- in trisodium 
cyclo-td-#-imido-triphosphate monohydrate, Na3(PO2- 
NH)3.H20, exhibits a chair conformation. Two trimeta- 
phosphimate tings are linked to one another by six N- -  
H.-.O hydrogen bonds forming pairs. These units are 
interconnected by O---H...O hydrogen bonds through 
water molecules forming columns. 
Comment 
In contrast to the well known structural chemistry 
of tfimetaphosphates (Durif, 1995), only very few 
structural details about trimetaphosphimates are known 
despite the fact that many salts of trimetaphos- 
phimic acid were known more than 100 years ago 
(Stokes, 1895). These compounds have been mainly 
characterized by IR spectroscopy (Pustinger, Cave 
& Nielsen, 1959) and powder diffraction (Herzog 
& Nielsen, 1958). In contrast to H3(PO2NH)3.2H20 
and (NH4)H2(PO2NH)3.CH3OH , where the P-N rings 
show a distorted boat conformation (Olthof, Migchelsen 
& Vos, 1965), the title compound, (I) (Fig. 1), 
© 1997 International Union of Crystallography 
Printed in Great Britain - all rights reserved 
Na3(PO2NH)3.4H20 and (NHn)3(PO2NH)3.H20 exhibit 
distorted chair conformations (Attig & Mootz, 1976; 
Stock & Schnick, 1996). 
H 
0,. /N'~_jO 
o "e P ' ~ o  
3Na + I -J" 
HN p./NH 
o'o 
(1) 
73- 
.H20 
As may be seen from the bond lengths and valence 
angles, the phosphimate ring in Na3(PO2NH)3.H20 
exhibits approximate 3m symmetry. Whereas in 
(NH4)3(PO2NH)3.H20 and Na3(PO2NH)3.4H20, three- 
dimensional networks of (PO2NH)~- anions and water 
molecules are formed by NmH. . -O and O---H...O 
hydrogen bonds, in Na3(PO2NH)3.H20, rings are linked 
pairwise to one another by six NmH. . .O  bonds [N.-.O 
2.964(2), 3.053(2) and 3.121 (2),A]. These units are 
028 O3B 
® 
N~ 
Na4 
Fig. I. The structure of (I) showing 50% probability displacement 
ellipsoids. H atoms are drawn as small circles of arbitrary size. 
Fig. 2. View along [001] of the crystal packing of the trimetaphos- 
phimate rings and water molecules illustrating the hydrogen bonds. 
The sodium ions have been omitted for clarity. 
Acta C~.stallographica Section C 
ISSN 0108-2701 © 1997 
N O R B E R T  S T O C K  A N D  W O L F G A N G  S C H N I C K  533 
in te rconnec ted  by  wa te r  mo lecu l e s  th rough  O - - H . - - O  
o 
h y d r o g e n  bonds  [ O . . . O  2 . 6 8 9 ( 2 )  and  2 . 7 2 0 ( 2 ) A ] ,  
the reby  fo rming  c o l u m n s  (Fig. 2). The  sod ium ions are 
approx imate ly  oc tahedraUy coord ina ted  by six O a toms  
f r o m  the p h o s p h i m a t e  groups  and  f rom the wate r  mol -  
ecules  [Na-.  -O 2.282 (2 ) -2 .984  (2) ,~]. 
PI 
P2 
P3 
Nal 
E x p e r i m e n t a l  Na2 
Na3 
The starting material, Na3(PO2NH)3.4H20, was obtained Na4 
according to Nielsen & Morrow (1960) by reaction (12h, OIA 
323 K) of 3 g Na(OOCCH3).3H20 in 48 ml water with 6 g OlB 
(PNC12)3 in 24ml  dioxane. Whereas the authors claim the O2A 
02B 
synthesis of (I) under these conditions, Na3(PO2NH)3.4H20 O3A 
is formed. Sodium trimetaphosphimate monohydrate was 03B 
prepared by a method similar to that of Stokes (1896); single O4A 
crystals of (I) of up to 5 mm in length were grown by vapour 04B 
NI 
diffusion of CH3CH2OH at 363 K into a 3 × 1 0 - 4 M  aque- N2 
ous solution of Na3(PO2NH)3.4H20. These crystals are stable N3 
in air under ambient conditions. According to DSC mea- 
surements, decomposition starts at approximately 450 K with 
evolution of NH3 and H20. 
Crystal data 
Na3(PO2NH)3.H20 Mo/Ca  radiation 
Mr = 320.95 A = 0.71073 A 
Monoclinic Cell parameters from 69 
C2 reflections 
a = 9.8797 (7) ~, 0 = 5.41-17.43 ° 
b = 12.2119 (8)oA # = 0.836 nun -~ 
c = 7.6464 (6) A T = 173 (2) K 
/3 = 104.394 (6) ° Column 
V = 893.58 (11)/~3 0.26 x 0.08 x 0.06 mm 
Z = 4 Colourless 
Dx = 2.386 Mg m -3 
Dm not measured 
Data collection 
Siemens P4 diffractometer 
o) s c a n s  
Absorption correction: 
empirical via ~b scans 
using XSCANS (Siemens, 
1994) and SHELXTL-PIus 
(Sheldrick, 1994) 
Tmin = 0.866, Tma~ = 0.951 
5209 measured reflections 
2616 independent reflections 
2259 reflections with 
I > 20-(/) 
Rint = 0.0367 
0max = 30  ° 
h - - - 1 3 - - ~  13 
k = - 1 7 - - +  17 
l = - l O - - ~  10 
3 standard reflections 
every 97 reflections 
intensity decay: 5.24% 
Refinement 
Refinement on F 2 
R(F) = 0.0311 
wR(F 2) = 0.0663 
S = 1.031 
2616 reflections 
152 parameters 
H atoms were refined using 
a riding model, starting 
from Fourier coordinates 
w = 1/[0.2(Fo 2) + (0.0311P) 2] 
where P = (Fo 2 + 2F~)/3 
( A / 0 . ) m a x  = 0 .001  
Apmax = 0.40 e ,~-3 
Apmin = -0 .32  e ,~-3 
Extinction correction: none 
Scattering factors from 
International Tables for 
Crystallography (Vol. C) 
Absolute configuration: 
Flack (1983) 
Flack parameter = 0.34 (12) 
Table 1. Fractional atomic coordinates and equivalent 
isotropic displacement parameters (1~ 2 ) 
Ueq = (1/3)~i~jUiJa~ a~ai.aj. 
x y z Ueq 
0.77111 (6) 0.61560 (8) 0.15493 (8) 0.00777 (12) 
0.64506 (9) 0.74470 (6) -0.17148 (10) 0.0075 (2) 
0.63899 (9) 0.50337 (6) -0 .19318 (I1) 0.0082 (2) 
0.87932 (10) 0.62554 (14) 0.61559 (13) 0.0119 (2) 
1 0.7710 (2) 0 0.0142 (4) 
1 0.4687 (2) 0 0.0175 (5) 
0.72100 (14) 0.41584 (10) -0 .5720 (2) 0.0186 (3) 
0.9208 (2) 0.6179 (2) 0.1454 (2) 0.0103 (3) 
0.7368 (2) 0.6037 (2) 0.3330 (2) 0.0120 (4) 
0.7745 (3) 0.7624 (2) -0 .2368 (3) 0.0117 (5) 
0.5343 (3) 0.8306 (2) -0 .2080 (3) 0.0125 (5) 
0.7623 (3) 0.4839 (2) -0 .2697 (3) 0.0132 (5) 
0.5215 (3) 0.4204 (2) -0 .2342 (3) 0.0118 (5) 
1 0.7685 (3) i/2 0.0154 (7) 
1 0.4603 (3) I/2 0.0188 (8) 
0.6920 (3) 0.7271 (2) 0.0529 (3) 0.0088 (5) 
0.5710 (2) 0.6269 (3) -0 .2573 (3) 0.0086 (4) 
0.6928 (3) 0.5092 (2) 0.0300 (3) 0.0098 (5) 
Table 2. Selected geometric parameters (A, o) 
Pi---O1B 1.490 (2) P2--N2 1.673 (3) 
PI---OIA 1.499 (2) P2--NI 1.676 (3) 
PI--N1 1.665 (3) P3--O3A 1.496 (3) 
PI--N3 1.682 (3) P3~3B 1.514 (2) 
P2---O2B 1.492 (3) P3--N3 1.658 (3) 
P2---O2A 1.499 (3) P3--N2 1.674 (3) 
OIB--PI--4)IA 119.83 (I0) N2--P2--NI 105.92 (13) 
OIB--PI--NI 108.76 (13) O3A--P3---O3B 117.99 (14) 
OIA--PI--N! 108.38 (15) O3A--P3--N3 109.0 (2) 
OIB--PI--N3 105.46 (14) O3B--P3--N3 105.98 (14) 
OIA--PI--N3 107.9 (2) O3A--P3--N2 109.61 (12) 
NI--PI--N3 105.63 (10) O3B--P3--N2 108.12 (14) 
O2B--P2--O2A 118.87 (14) N3--P3--N2 105.38 (13) 
O2B--P2--N2 107.60 (14) PI--N1--P2 124.3 (2) 
O2A--P2--N2 108.64 (12) P2--N2--P3 123.72 (12) 
O2B--P2--N i 106.59 (14) P3--N3--PI 127.0 (2) 
O2A--P2--N 1 108.49 (14) 
Since the title compound crystallizes in a polar space group, 
polar axis restraints were applied according to the method 
of Flack & Schwarzenbach (1988) and the absolute structure 
of the crystal used for the investigation was established as 
described by Flack (1983). Linear decay was observed during 
the data collection and a correction was included in the data 
reduction procedure using SHELXTL-PIus (Sheldrick, 1994). 
All H atoms were unambiguously located after the anisotropic 
refinement of all non-H atoms. The w-scan width was 1.2 °, 
with an w-scan rate of 3.0 ° min -I  . The background to signal 
ratio was 0.5. 
Data collection: XSCANS (Siemens, 1994). Cell refinement: 
XSCANS. Data reduction: SHELXTL-PIus. Program(s) used to 
solve structure: SHELXS86 (Sheldrick, 1990). Program(s) used 
to refine structure: SHELXL93 (Sheldrick, 1993). Molecular 
graphics: SHELXTL-PIus. Software used to prepare material 
for publication: SHELXTL-PIus. 
Financia l  support  by  the  Deu t sche  F o r s c h u n g s g e m e i n -  
schaft  (project  S C H N  377/6-1 and the Got t f r ied  W i l h e l m  
Le ibn iz  p rogram)  and the Fonds  der  C h e m i s c h e n  Indus-  
trie is grateful ly  a c k n o w l e d g e d .  
534 Na3 0aO2NH)3.H20 
Lists of atomic coordinates, displacement parameters, structure factors 
and complete geometry have been deposited with the IUCr (Reference: 
BMIll9). Copies may be obtained through The Managing Editor, 
International Union of Crystallography, 5 Abbey Square, Chester CH 1 
2HU, England. 
References 
Attig, R. & Mootz, D. (1976). Z. Anorg. Allg. Chem. 419, 139-156. 
Durif, A. (1995). In Crystal Chemistry of Condensed Phosphates. New 
York: Plenum Press. 
Flack, H. D. (1983). Acta Cryst. A39, 876-881. 
Flack, H. D. & Schwarzenbach, D. (1988). Acta Cryst. A44, 499-506. 
Herzog, A. H. & Nielsen, M. L. (1958). Anal. Chem. 30, 1490-1496. 
Nielsen, M. L. & Morrow, T. J. (1960). lnorg. Synth. 6, 99. 
Olthof, R., Migchelsen, T. & Vos, A. (1965). Acta Cryst. 19, 596-603. 
Pustinger, J. V., Cave, W. T. & Nielsen, M. L. (1959). Spectrochim. 
Acta, 11, 909-925. 
Sheldrick, G. M. (1990). Acta Cryst. A46, 467--473. 
Sheldrick, G. M. (1993). SHELXL93. Program for the Refinement of 
Crystal Structures. University of Gtttingen, Germany. 
Sheldrick, G. M. (1994). SHELXTL-Plus. Release 5.03. Siemens 
Analytical X-ray Instruments Inc., Madison, Wisconsin, USA. 
Siemens (1994). XSCANS Users Manual. Version 2.1. Siemens 
Analytical X-ray Instruments Inc., Madison, Wisconsin, USA. 
Stock, N. & Schnick, W. (1996). Acta Cryst. C52, 2645-2647. 
Stokes, H. N. (1895). Ber. Dtsch Chem. Ges. 28, 437. 
Stokes, H. N. (1896). Am. Chem. J. 18, 629-663. 
Acta Cryst. (1997). C53, 534-536 
Strontium Metasilicate, SrSiO3 
FtJMrro NISH1 
Saitama Institute of Technology, Fusaiji 1690, Okabe, 
Ohsato-gun, Saitama 369-02, Japan. E-mail: nishi@sit. 
ac.jp 
(Received 11 September 1996; accepted 11 December 1996) 
Abstract 
Strontium silicon trioxide has been synthesized for the 
first time and its structure solved. It is isostructural with 
the germanium analogue SrGeO3 reported by Hilmer 
[Soy. Phys. Crystallogr. (1963), 7, 573-576], but the 
true symmetry is monoclinic, rather than hexagonal 
as reported earlier. The structure has alternate layers 
of ternary rings of SiO4 groups and close-packed Sr 
atoms stacked along [001]. Viewed as a polytype, this 
compound has a six-layer structure and the calcium 
analogue a-CaSiO3 [Yamanaka & Mori (1981). Acta 
Cryst. B37, 1010-1017] has a four-layer structure. 
Comment  
The title compound has been synthesized for the first 
time. Dornberger-Schiff (1962) discussed the symmetry 
© 1997 International Union of Crystallography 
Printed in Great Britain - all fights reserved 
of the analogous germanium compound SrGeO3. Hilmer 
(1963) studied the structure of SrGeO3 using a Weis- 
senberg camera. He obtained the hexagonal lattice pa- 
rameters a - 7.29, c = 31.64,~ and showed that the 
structure contained ternary rings of GeO4 groups. In 
addition, he concluded that the structure was composed 
of alternating layers of [Ge309]  6 -  r ings  and layers of 
Sr atoms. Nadezhina, Pobedimskaya, Ilyukhin & Belov 
(1981a,b) also studied SrGeO3 and obtained the triclinic 
lattice parameters a = 8.699, b = 9.935, c -- 11.148,~,, 
a = 106.04,/3 = 89.97, 3' = 102.11 °. This structure also 
contained rings of GeO4 groups. The configurations of 
the rings, however, were somewhat different from those 
in the study by Hilmer, and Nadezhina et al. stated that 
the different types of ternary rings in the two modifica- 
tions of strontium metagermanate were undoubtedly the 
result of a difference in the structures of the cation lay- 
ers. In addition, they called the form they had studied the 
low-temperature form (a'-SrGeO3) and the form studied 
by Hilmer the high-temperature form (a-SrGeO3). 
Ito (1950) and Buerger & Prewitt (1961) discussed 
the analogous calcium compound CaSiO3 (the high- 
pressure form). Trojer (1969) obtained the triclinic 
lattice parameters a - 6.695, b = 9.257, c = 6.666,~, 
= 86.5, /3 = 76.13, 3' = 70.38 ° and solved its 
structure. He concluded that the basic features of this 
structure were irregular layers of Ca atoms, which were 
interconnected by pairs of Ca atoms, and Si309 rings, 
which were located in the remaining space between the 
layers. Yamanaka & Mori (1981) studied the structure 
of a-CaSiO3 (pseudowollastonite) from the viewpoint 
of polytypism. In their definition, a layer comprises 
one layer of the ternary rings plus one layer of CaO8 
polyhedra. They concluded that c~-CaSiO3 has a four- 
layer structure and the form of SrGeO3 studied by 
Hilmer has a six-layer structure. 
The symmetry of the title compound, SrSiO3, was 
found to be different not only to that of the form of 
SrGeO3 studied by Hilmer but also to that of the form 
of SrGeO3 studied by Nadezhina et al. SrSiO3, however, 
is almost isostructural with the form of SrGeO3 studied 
by Hilmer for two reasons. Firstly, SrSiO3 has a pseudo- 
hexagonal cell which corresponds to the cell given by 
Hilmer. Secondly, all of the reflections observed by 
Hilmer can be indexed on the basis of the present 
monoclinic cell. On the contrary, the structure of 
SrGeO3 reported by Nadezhina et al. is different. It can 
be concluded that there are two forms of SrGeO3, but 
only one form of SrSiO3 is known so far. 
The arrangement of the ternary rings of SiO4 groups 
and SrO8 polyhedra is shown in Fig. 1. The polyhedron 
around Sr(1) is very irregular, but that around Sr(2) can 
be regarded as a distorted hexagonal bipyramid, with 
O(1) on either side of the hexagon. The SrO8 polyhedra 
form a close-packed layer like the olivine structure. The 
layers of the ternary rings of SiO4 groups and the layers 
of SrO8 polyhedra are shown in Fig. 2. They are stacked 
Acta Crystallographica Section C 
ISSN 0108-2701 © 1997 


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