metal-organic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

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ISSN: 2053-2296

The catena-arsenite chain anion, [AsO2]nn: (H3NCH2CH2NH3)0.5[AsO2] and NaAsO2 (revisited)

aDepartment of Chemistry, University of Aberdeen, Meston Walk, Aberdeen AB24 3UE, Scotland
*Correspondence e-mail: w.harrison@abdn.ac.uk

(Received 17 March 2004; accepted 29 March 2004; online 30 April 2004)

The title compounds contain the catena-arsenite [AsO2]nn unit, in which the AsIII atom is pyramidally coordinated to one terminal and two bridging O atoms, resulting in an infinite anionic chain. Ethylenediammonium catena-arsenite, (C2H10N2)0.5[AsO2], is the first example of this anion in the company of an organic cation. The ethyl­enedi­ammonium species interact with the [AsO2] chains by way of N—H⋯O hydrogen bonds. The structure of sodium catena-arsenite, Na[AsO2] [Menary (1958[Menary, J. W. (1958). Acta Cryst. 11, 742-743.]). Acta Cryst. 11, 742–743], has been redetermined to yield more reliable geometrical parameters. The As—O distances are normal and the Na+ cation is seven-­coordinate [Na—O = 2.285 (4)–3.063 (4) Å] in a distorted capped trigonal prismatic geometry.

Comment

The [AsO3]3− arsenite group shows a distinctive pyramidal geometry, due to the stereochemically active lone pair of electrons on the AsIII species, with an electron configuration of [core]4s24p1. This geometry is quite distinct from the tetrahedral coordination invariably displayed by the [AsVO4]3− arsenate group. A number of minerals and synthetic compounds containing isolated pyramidal [AsO3]3− ions are known, examples being reinerite, Zn3(AsO3)2 (Ghose et al., 1977[Ghose, S., Boving, P., Lachapelle, W. A. & Wan, C. (1977). Am. Mineral. 62, 1129-1134.]), and the unusual arsenite–chloride finnemanite, Pb5(AsO3)3Cl (Effenberger & Pertlik, 1979[Effenberger, H. & Pertlik, F. (1979). Tschermaks Mineral. Petrogr. Mitt. 26, 95-107.]).

Arsenite groups may polymerize (or condense) via vertices into extended units, the simplest example of this being the [As2O5]4− diarsenite group, which is found in paulmooreite, Pb2As2O5 (Araki et al., 1980[Araki, T., Moore, P. B. & Brunton, G. D. (1980). Am. Mineral. 65, 340-345.]). In ludlockite, PbFe4(As5O11)2 (Cooper & Hawthorne, 1996[Cooper, M. A. & Hawthorne, F. C. (1996). Can. Mineral. 34, 79-89.]), as many as five AsO3 units are fused together into [As5O11]7− units. The polymerization of arsenite groups results in the catena-arsenite chain anion, [AsO2] (or [AsO2]nn), which was first definitively characterized by Zemann (1951[Zemann, J. (1951). Tschermaks Mineral. Petrogr. Mitt. 2, 417-423.]) in the mineral trippkeite, CuAs2O4. A few years later, the same anion was found in the synthetic compound NaAsO2 by Menary (1958[Menary, J. W. (1958). Acta Cryst. 11, 742-743.]). The trippkeite structure was redetermined to improved precision by Pertlik (1975[Pertlik, F. (1975). Tschermaks Mineral. Petrogr. Mitt. 22, 211-217.]), who also showed that the two synthetic lead catena-arsenite chlorides Pb(AsO2)Cl and Pb2(AsO2)3Cl contain the same chain anion (Pertlik, 1988[Pertlik, F. (1988). Z. Kristallogr. 184, 191-201.]), as does the mineral leiteite, ZnAs2O4 (Ghose et al., 1987[Ghose, S., Sen Gupta, P. K. & Schlemper, E. O. (1987). Am. Mineral. 72, 629-632.]).

[Scheme 1]

We describe here the structure of ethyl­enedi­ammonium catena-arsenite, (H3NCH2CH2NH3)0.5[AsO2], (I[link]), which is the first example of a catena-arsenite chain accompanied by organic cations. We also describe the redetermined structure of NaAsO2, (II[link]).

Compound (I[link]) (Fig. 1[link]) shows (H3NCH2CH2NH3)2+ cations and anionic [AsO2] chains. The geometrical parameters for the complete ethyl­enedi­ammonium cation, which is generated by twofold symmetry from the unique atoms, are normal. The catena-arsenite chain is built up from three distinct atoms, with atom O1 forming the terminal As—O bond and atom O2 acting as the bridging atom. As expected, the geometry around As is pyramidal, with the As atom displaced from the least-squares plane of the basal O atoms by 0.886 (2) Å. Interestingly, the most prominent peak (1.11 e Å−3) in the final difference Fourier map for (I[link]) is 0.74 Å from As, approximately where the lone pair of electrons is presumed to be located, and could thus correspond to a real chemical feature. As found in other well determined catena-arsenites (Pertlik, 1975[Pertlik, F. (1975). Tschermaks Mineral. Petrogr. Mitt. 22, 211-217.]; Ghose et al., 1987[Ghose, S., Sen Gupta, P. K. & Schlemper, E. O. (1987). Am. Mineral. 72, 629-632.]), the terminal As—OT bond in (I[link]) [1.705 (3) Å] is distinctly shorter than the average of the bridging bonds [mean As—OB = 1.812 (2) Å]. The OB—As—OB bond angle is significantly smaller than the OB—As—OT bond angles (Table 1[link]).

As well as van der Waals and electrostatic forces, the organic cations and the chain anion in (I[link]) interact by way of N—H⋯O hydrogen bonds (Table 2[link]). Two of the three H—N moieties make short near-linear hydrogen bonds to arsenite O-atom acceptors, whilst the third N—H group is bifurcated to two arsenite O acceptor atoms (sum of D—H⋯A bond angles about atom H1 = 359°). Overall, OT accepts three hydrogen bonds and OB accepts one. These interactions help to define a structure (Fig. 2[link]) in which the catena-arsenite chains propagate along [010] (generated by the 21 screw axis), crosslinked along [100] by O⋯H—N—H⋯O bonds. Interchain linking along [001] is via the backbone of the organic moiety. The intrachain As⋯Asi separation in (I[link]) is 3.1991 (4) Å [symmetry code: (i) 1 − x, y − [{1 \over 2}], [{1 \over 2}] − z].

The structure of (II[link]) (Fig. 3[link]) is more or less the same as that determined by Menary (1958[Menary, J. W. (1958). Acta Cryst. 11, 742-743.]) using film methods, but with improved standard uncertainties. The Na+ cation is coordinated to seven O atoms (mean Na—O = 2.623 Å), all of which are parts of neighbouring anionic [AsO2] chains. The resulting NaO7 polyhedron approximates to a distorted capped trigonal prism. The Na bond valence sum (BVS) of 1.00 (Brown, 1996[Brown, I. D. (1996). J. Appl. Cryst. 29, 479-480.]) is exactly in agreement with the expected value. The As geometry is again pyramidal, with the As atom displaced from the least-squares plane of the basal O atoms by 0.912 (3) Å. The As—O distances [As—OT = 1.684 (4) Å and mean As—OB = 1.822 (3) Å] are similar to those found for (I[link]). As in (I[link]), the OB—As—OB bond angle is significantly smaller than the OB—As—OT bond angles (Table 3[link]). By comparison, Menary's (1958[Menary, J. W. (1958). Acta Cryst. 11, 742-743.]) results (As—OT = 1.600 Å, and As—OB = 1.810 and 1.947 Å) indicated a much greater degree of distortion about As.

In the unit-cell packing in (II[link]) (Fig. 4[link]), the catena-arsenite chains propagate along [010], as generated by b-glide symmetry, resulting in an intrachain As⋯Asii separation of 3.2121 (7) Å [symmetry code: (ii) [{1 \over 2}] − x, [{1 \over 2}] + y, z]. The face- and edge-sharing NaO7 groups are sandwiched between the [AsO2] chains and crosslink them in the a direction, resulting in neutral (001) slabs of stoichiometry NaAsO2. The AsIII lone-pair electrons appear to be directed into the inter-slab region. The shortest interblock As⋯O and As⋯As contacts are 3.762 (3) and 3.6844 (7) Å, respectively. This is quite reminiscent of the situation in ludlockite (Cooper & Hawthorne, 1996[Cooper, M. A. & Hawthorne, F. C. (1996). Can. Mineral. 34, 79-89.]), in which the [As5O11]7− units face each other.

The geometrical parameters for the [AsO2] units in (I[link]) and (II[link]) are broadly consistent with the equivalent data for CuAs2O4 and ZnAs2O4. In particular, the As—OB bond lengths are clustered in the narrow range of 1.806 (2)–1.829 (3) Å. The As—OT bond lengths show somewhat greater variability, which might be due to the different bonding situations of the O atoms in question: the OT atom in (I[link]) [1.705 (3) Å] only accepts hydrogen bonds, whereas the OT atom in CuAs2O4 (1.765 Å) is also bonded to two Cu atoms. However, there are also some significant differences. For example, the OB—As—OB bond angle of 100.3° in CuAs2O4 is significantly larger than the OB—As—OT bond angle (95.9°), which is the reverse of the situation for (I[link]), (II[link]) and ZnAs2O4 (Ghose et al., 1987[Ghose, S., Sen Gupta, P. K. & Schlemper, E. O. (1987). Am. Mineral. 72, 629-632.]).

[Figure 1]
Figure 1
A view of a fragment of (I[link]), drawn with 50% probability displacement ellipsoids. H atoms are drawn as small spheres of arbitrary radii and hydrogen bonds are indicated by dashed lines. [Symmetry codes: (i) [{1 \over 2}] − x, y, 1 − z; (ii) 1 − x, y − [{1 \over 2}], [{1 \over 2}] − z; (iii) x, y − 1, z.]
[Figure 2]
Figure 2
The unit-cell packing in (I[link]), projected on to (010) (normal to the catena-arsenite chain direction). Hydrogen bonds are indicated by dashed lines.
[Figure 3]
Figure 3
A view of a fragment of (II[link]), drawn with 50% probability displacement ellipsoids. Note that atoms O1, O2 and O2v represent a face shared between the AsO3 and NaO7 polyhedra. [Symmetry codes are as in Table 3[link]; additionally: (vii) [{1 \over 2}] − x, y + [{1 \over 2}], z.]
[Figure 4]
Figure 4
A polyhedral representation of the unit-cell packing in (II[link]), projected on to (010). The NaO7 polyhedra are shown with light shading and the AsO3 groups are represented by AsO3E tetrahedra (dark shading), where the dummy atom E (very dark shading), placed 1.0 Å from As, represents the lone pair of electrons. The catena-arsenite chains propagate towards the viewer.

Experimental

For (I[link]), a mixture of As2O3 (1 g), ethyl­enedi­amine (0.5 g) and water (10 ml) was heated to 353 K in a plastic bottle for 48 h. Upon cooling, the resultant solids were filtered off, yielding some plate-shaped crystals of (I[link]) accompanied by substantial amounts of undissolved or recrystallized As2O3. We have not yet succeeded in making (I[link]) in purer form. For (II[link]), a commercial sample (Sigma Chemical Co.) of NaAsO2 was recrystallized from methanol, in which it is sparingly soluble. The resulting crystal quality is poor.

Compound (I)[link]

Crystal data
  • (C2H10N2)0.5[AsO2]

  • Mr = 137.98

  • Monoclinic, I2/a

  • a = 12.7854 (8) Å

  • b = 4.6647 (3) Å

  • c = 13.3343 (9) Å

  • β = 91.7380 (10)°

  • V = 794.89 (9) Å3

  • Z = 8

  • Dx = 2.306 Mg m−3

  • Mo Kα radiation

  • Cell parameters from 2219 reflections

  • θ = 3.1–32.5°

  • μ = 8.37 mm−1

  • T = 293 (2) K

  • Plate, colourless

  • 0.31 × 0.29 × 0.02 mm

Data collection
  • Bruker SMART 1000 CCD area-detector diffractometer

  • ω scans

  • Absorption correction: multi-scan (SADABS; Bruker, 1999[Bruker (1999). SMART (Version 5.624), SAINT (Version 6.02a) and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]) Tmin = 0.131, Tmax = 0.850

  • 3520 measured reflections

  • 1430 independent reflections

  • 1181 reflections with I > 2σ(I)

  • Rint = 0.037

  • θmax = 32.5°

  • h = −16 → 19

  • k = −7 → 5

  • l = −19 → 20

Refinement
  • Refinement on F2

  • R[F2 > 2σ(F2)] = 0.039

  • wR(F2) = 0.115

  • S = 1.05

  • 1430 reflections

  • 48 parameters

  • H-atom parameters constrained

  • w = 1/[σ2(Fo2) + (0.0792P)2 + 0.139P] where P = (Fo2 + 2Fc2)/3

  • (Δ/σ)max < 0.001

  • Δρmax = 1.11 e Å−3

  • Δρmin = −1.68 e Å−3

  • Extinction correction: SHELXL97 (Sheldrick, 1997[Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany.])

  • Extinction coefficient: 0.0032 (8)

Table 1
Selected geometric parameters (Å, °) for (I)[link]

As—O1 1.705 (3) 
As—O2 1.806 (2)
As—O2i 1.817 (3)
O1—As—O2 99.04 (10)
O1—As—O2i 98.57 (13)
O2—As—O2i 93.93 (7)
As—O2—Asii 123.99 (13)
Symmetry codes: (i) [1-x,y-{\script{1\over 2}},{\script{1\over 2}}-z]; (ii) [1-x,{\script{1\over 2}}+y,{\script{1\over 2}}-z].

Table 2
Hydrogen-bonding geometry (Å, °) for (I)[link]

D—H⋯A D—H H⋯A DA D—H⋯A
N—H1⋯O1i 0.89 2.10 2.905 (4) 150
N—H1⋯O2ii 0.89 2.58 3.318 (4) 140
N—H2⋯O1iii 0.89 1.83 2.719 (3) 174
N—H3⋯O1 0.89 1.82 2.701 (3) 172
Symmetry codes: (i) [{\script{1\over 2}}-x,{\script{1\over 2}}-y,{\script{1\over 2}}-z]; (ii) [x-{\script{1\over 2}},1-y,z]; (iii) x,y-1,z.

Compound (II)[link]

Crystal data
  • Na[AsO2]

  • Mr = 129.91

  • Orthorhombic, Pbca

  • a = 6.7762 (5) Å

  • b = 5.0901 (4) Å

  • c = 14.3098 (11) Å

  • V = 493.57 (7) Å3

  • Z = 8

  • Dx = 3.497 Mg m−3

  • Mo Kα radiation

  • Cell parameters from 1514 reflections

  • θ = 2.9–31.8°

  • μ = 13.62 mm−1

  • T = 293 (2) K

  • Rod, colourless

  • 0.23 × 0.08 × 0.08 mm

Data collection
  • Bruker SMART 1000 CCD area-detector diffractometer

  • ω scans

  • Absorption correction: multi-scan (SADABS; Bruker, 1999[Bruker (1999). SMART (Version 5.624), SAINT (Version 6.02a) and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]) Tmin = 0.120, Tmax = 0.336

  • 5152 measured reflections

  • 894 independent reflections

  • 639 reflections with I > 2σ(I)

  • Rint = 0.048

  • θmax = 32.5°

  • h = −10 → 10

  • k = −7 → 6

  • l = −21 → 18

Refinement
  • Refinement on F2

  • R[F2 > 2σ(F2)] = 0.040

  • wR(F2) = 0.109

  • S = 1.01

  • 894 reflections

  • 37 parameters

  • w = 1/[σ2(Fo2) + (0.0661P)2] where P = (Fo2 + 2Fc2)/3

  • (Δ/σ)max < 0.001

  • Δρmax = 2.97 e Å−3

  • Δρmin = −1.05 e Å−3

Table 3
Selected geometric parameters (Å, °) for (II)[link]

Na—O1i 2.285 (4) 
Na—O1 2.397 (5)
Na—O2ii 2.413 (4)
Na—O1iii 2.420 (4)
Na—O1iv 2.785 (4)
Na—O2 2.996 (4)
Na—O2v 3.063 (4)
As—O1 1.684 (4)
As—O2v 1.815 (3)
As—O2 1.829 (3)
O1—As—O2v 95.42 (16)
O1—As—O2 99.07 (17)
O2v—As—O2 92.93 (11)
Asvi—O2—As 123.66 (19)
Symmetry codes: (i) [x-{\script{1\over 2}},{\script{3\over 2}}-y,1-z]; (ii) [{\script{1\over 2}}+x,{\script{3\over 2}}-y,1-z]; (iii) 1-x,2-y,1-z; (iv) 1-x,1-y,1-z; (v) [{\script{1\over 2}}-x,y-{\script{1\over 2}},z]; (vi) [{\script{1\over 2}}-x,{\script{1\over 2}}+y,z].

For (I[link]), the H atoms were placed in calculated positions (C—H distances in the range 0.96–0.98 Å and N—H distances of 0.89 Å) and refined by riding, allowing for free rotation of the rigid NH3 group about the C—N bond. The constraint Uiso(H) = 1.2Ueq(attached atom) was applied in all cases. For (II[link]), the maximum difference peak was 0.82 Å from As.

For both compounds, data collection: SMART (Bruker, 1999[Bruker (1999). SMART (Version 5.624), SAINT (Version 6.02a) and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT (Bruker, 1999[Bruker (1999). SMART (Version 5.624), SAINT (Version 6.02a) and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997[Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997[Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany.]); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997[Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565.]) and ATOMS (Dowty, 1999[Dowty, E. (1999). ATOMS. Version 5.0.7 for Windows and Macintosh. Shape Software, 521 Hidden Valley Road, Kingsport, TN 37663, USA.]); software used to prepare material for publication: SHELXL97.

Supporting information


Comment top

The [AsO3]3− arsenite group shows a distinctive pyramidal geometry, due to the stereochemically active lone pair of electrons on the AsIII species, with an electron configuration of [core]4 s24p1. This geometry is quite distinct from the tetrahedral coordination invariably displayed by the [AsVO4]3− arsenate group. A number of minerals and synthetic compounds containing isolated pyramidal [AsO3]3− ions are known, such as reinerite, Zn3(AsO3)2 (Ghose et al., 1977), and the unusual arsenite-chloride finnemanite, Pb5(AsO3)3Cl (Effenberger & Pertlik, 1979).

Arsenite groups may polymerize (or condense) via vertices into extended units, the simplest example of this being the [As2O5]4− diarsenite group, which is found in paulmooreite, Pb2As2O5 (Araki et al., 1980). In ludlockite, PbFe4(As5O11)2 (Cooper & Hawthorne, 1996), as many as five AsO3 units are fused together into [As5O11]7− units. The polymerization of arsenite groups results in the catena-arsenite chain-anion, [AsO2] (or [AsO2]nn-), which was first definitively characterized by Zemann (1951) in the mineral trippkeite, CuAs2O4. A few years later, the same anion was found in the synthetic compound NaAsO2 by Menary (1958). The trippkeite structure was redetermined to improved precision by Pertlik (1975), who also showed that the two synthetic lead catena-arsenite chlorides, Pb(AsO2)Cl and Pb2(AsO2)3Cl, contain the same chain anion (Pertlik, 1988), as does the mineral leiteite, ZnAs2O4 (Ghose et al., 1987).

Here, we describe the structure of ethylenediammonium catena-arsenite, (H3NCH2CH2NH3)0.5·AsO2, (I), which is the first example of a catena-arsenite chain accompanied by organic cations. We also describe the redetermined structure of NaAsO2, (II). \sch

Compound (I) (Fig. 1) shows (H3NCH2CH2NH3)2+ cations and anionic [AsO2] chains. The geometrical parameters for the complete ethylenediammonium cation, which is generated by twofold symmetry from the unique atoms, are normal. The catena-arsenite chain is built up from three distinct atoms, with atom O1 forming the terminal As—O bond and atom O2 acting as the bridging atom. As expected, the geometry around As is pyramidal, with the As atom displaced from the least-squares plane of the basal O atoms by 0.886 (2) Å. Interestingly, the most prominent peak (1.11 e/Å3) in the final difference Fourier map for (I) is 0.74 Å from As, approximately where the lone pair of electrons is presumed to be located, and could thus correspond to a real chemical feature. As found in other well determined catena-arsenites (Pertlik, 1975; Ghose et al., 1987), the terminal As—OT bond in (I) [1.705 (3) Å] is distinctly shorter than the average of the bridging bonds [mean As—OB 1.812 (2) Å]. The OB—As—OB bond angle is significantly smaller than the OB—As—OT bond angles (Table 1).

As well as van der Waals and electrostatic forces, the organic cations and the chain anion in (I) interact by way of N—H···O hydrogen bonds (Table 2). Two of the three H—N moieties make short near-linear hydrogen bonds to arsenite O-atom acceptors, whilst the third N—H group is bifurcated to two arsenite O acceptor atoms (sum of D—H···A bond angles about atom H1 = 359°). Overall, OT accepts three H bonds and OB accepts one. These interactions help to define a structure (Fig. 2) in which the catena-arsenite chains propagate along [010] (generated by the 21 screw axis), crosslinked along [100] by O···H—N—H···O bonds. Inter-chain linking along [001] is via the backbone of the organic moiety. The intra-chain As···Asi separation in (I) is 3.1991 (4) Å [symmetry code: (i) 1 − x, y − 1/2, 1/2 − z].

The structure of (II) (Fig. 3) is more or less the same as that determined by Menary (1958) using film methods, but with improved standard uncertainties. The Na+ cation is coordinated to seven O atoms (mean Na—O 2.623 Å), all of which are parts of neighbouring anionic [AsO2] chains. The resulting NaO7 polyhedron approximates to a distorted capped trigonal prism. The Na bond valence sum (BVS) of 1.00 (Brown, 1996) is exactly in agreement with the expected value. The As geometry is again pyramidal, with the As atom displaced from the least-squares plane of the basal O atoms by 0.912 (3) Å. The As—O distances [As—OT 1.684 (4) Å and mean As—OB 1.822 (3) Å] are similar to those found for (I). As in (I), the OB—As—OB bond angle is significantly smaller than the OB—As—OT bond angles (Table 3). By comparison, Menary's (1958) results (As—OT 1.600 Å, and As—OB 1.810 and 1.947 Å) indicated a much greater degree of distortion about As.

In the unit-cell packing in (II) (Fig. 4), the catena-arsenite chains propagate along [010] as generated by b-glide symmetry, resulting in an intrachain As···Asii separation of 3.2121 (7) Å [symmetry code: (ii) 1/2 − x, 1/2 + y, z]. The face- and edge-sharing NaO7 groups are sandwiched between the [AsO2] chains and crosslink them in the a direction, resulting in neutral (001) slabs of stoichiometry NaAsO2. The AsIII lone-pair electrons appear to be directed into the inter-slab region. The shortest inter-block As···O and As···As contacts are 3.762 (3) and 3.6844 (7) Å, respectively. This is quite reminiscent of the situation in ludlockite (Cooper & Hawthorne, 1996), in which the [As5O11]7− units face each other.

The geometrical parameters for the [AsO2] units in (I) and (II) are broadly consistent with the equivalent data for CuAs2O4 and ZnAs2O4. In particular, the As—OB bond lengths are clustered in the narrow range of 1.806 (2)–1.829 (3) Å. The As—OT bond lengths show somewhat greater variability, which might be due to the different bonding situations of the O atoms in question: the OT atom in (I) [1.705 (3) Å] only accepts hydrogen bonds, whereas the OT atom in CuAs2O4 (1.765 Å) is also bonded to two Cu atoms. However, there are also some significant differences. For example, the OB—As—OB bond angle of 100.3° in CuAs2O4 is significantly larger than the OB—As—OT bond angle (95.9°), which is the reverse of the situation for (I), (II) and ZnAs2O4 (Ghose et al., 1987).

Experimental top

For (I), a mixture of As2O3 (1 g), ethylenediamine (0.5 g) and water (10 ml) were heated to 353 K in a plastic bottle for 48 h. Upon cooling, the resultant solids were filtered off, yielding some plates of (I) accompanied by substantial amounts of undissolved or recrystallized As2O3. We have not yet succeeded in making (I) in purer form. For (II), a commercial sample (Sigma Chemical Co.) of NaAsO2 was recrystallized from methanol, in which it is sparingly soluble. The resulting crystal quality is poor.

Refinement top

For (I), the H atoms were placed in calculated positions (C—H distances in the range 0.96–0.98 Å and N—H distances of 0.89 Å) and refined by riding, allowing for free rotation of the rigid NH3 group about the C—N bond. The constraint Uiso(H) = 1.2Ueq(attached atom) was applied in all cases. For (II), the maximum difference peak is 0.82 Å from As.

Computing details top

For both compounds, data collection: SMART (Bruker, 1999); cell refinement: SAINT (Bruker, 1999); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997) and ATOMS (Dowty, 1999); software used to prepare material for publication: SHELXL97.

Figures top
[Figure 1] Fig. 1. A view of a fragment of (I), drawn with 50% probability displacement ellipsoids. H atoms are drawn as small spheres of arbitrary radii and hydrogen bonds are indicated by dashed lines. [Symmetry codes: (i) 1/2 − x, y, 1 − z; (ii) 1 − x, y − 1/2, 1/2 − z; (iii) x, y − 1, z.]
[Figure 2] Fig. 2. The unit-cell packing in (I), projected onto (010) (normal to the catena-arsenite chain direction). Hydrogen bonds are indicated by dashed lines.
[Figure 3] Fig. 3. A view of a fragment of (II), drawn with 50% probability displacement ellipsoids. Note that atoms O1, O2 and O2v represent a face shared between the AsO3 and NaO7 polyhedra. [Symmetry codes are as in Table 3; additionally: (vii) 1/2 − x, y + 1/2, z.]
[Figure 4] Fig. 4. A polyhedral representation of the unit-cell packing in (II), projected onto (010). The NaO7 polyhedra are shown with light shading and the AsO3 groups are represented by AsO3E tetrahedra (dark shading), where the dummy atom E (very dark shading), placed 1.0 Å from As, represents the lone pair of electrons. The catena-arsenite chains propagate towards the viewer.
(I) ethylenediammonium catena-arsenite top
Crystal data top
(C2H10N2)0.5[AsO2]F(000) = 536
Mr = 137.98Dx = 2.306 Mg m3
Monoclinic, I2/aMo Kα radiation, λ = 0.71073 Å
Hall symbol: -I 2yaCell parameters from 2219 reflections
a = 12.7854 (8) Åθ = 3.1–32.5°
b = 4.6647 (3) ŵ = 8.37 mm1
c = 13.3343 (9) ÅT = 293 K
β = 91.738 (1)°Plate, colourless
V = 794.89 (9) Å30.31 × 0.29 × 0.02 mm
Z = 8
Data collection top
Bruker SMART 1000 CCD area-detector
diffractometer
1430 independent reflections
Radiation source: fine-focus sealed tube1181 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.037
ω scansθmax = 32.5°, θmin = 3.1°
Absorption correction: multi-scan
(SADABS; Bruker, 1999)
h = 1619
Tmin = 0.131, Tmax = 0.850k = 75
3520 measured reflectionsl = 1920
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.039H-atom parameters constrained
wR(F2) = 0.115 w = 1/[σ2(Fo2) + (0.0792P)2 + 0.139P]
where P = (Fo2 + 2Fc2)/3
S = 1.05(Δ/σ)max < 0.001
1430 reflectionsΔρmax = 1.11 e Å3
48 parametersΔρmin = 1.68 e Å3
0 restraintsExtinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.0032 (8)
Crystal data top
(C2H10N2)0.5[AsO2]V = 794.89 (9) Å3
Mr = 137.98Z = 8
Monoclinic, I2/aMo Kα radiation
a = 12.7854 (8) ŵ = 8.37 mm1
b = 4.6647 (3) ÅT = 293 K
c = 13.3343 (9) Å0.31 × 0.29 × 0.02 mm
β = 91.738 (1)°
Data collection top
Bruker SMART 1000 CCD area-detector
diffractometer
1430 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 1999)
1181 reflections with I > 2σ(I)
Tmin = 0.131, Tmax = 0.850Rint = 0.037
3520 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0390 restraints
wR(F2) = 0.115H-atom parameters constrained
S = 1.05Δρmax = 1.11 e Å3
1430 reflectionsΔρmin = 1.68 e Å3
48 parameters
Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
N0.2497 (2)0.0011 (4)0.3599 (2)0.0275 (5)
H10.19790.00320.31380.041*
H20.28830.15570.35220.041*
H30.28960.15580.35280.041*
C0.2058 (2)0.0010 (5)0.4606 (2)0.0280 (6)
H40.16240.16750.46880.034*
H50.16240.16950.46880.034*
As0.48708 (2)0.51719 (5)0.33079 (2)0.02731 (15)
O10.3543 (2)0.4989 (3)0.3369 (2)0.0352 (5)
O20.49976 (18)0.8904 (5)0.29703 (19)0.0446 (6)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N0.0311 (12)0.0232 (11)0.0283 (11)0.0023 (6)0.0027 (9)0.0009 (6)
C0.0241 (12)0.0331 (15)0.0269 (12)0.0000 (7)0.0034 (9)0.0002 (8)
As0.0255 (2)0.01769 (18)0.0387 (2)0.00149 (7)0.00033 (13)0.00244 (8)
O10.0280 (11)0.0219 (10)0.0565 (16)0.0018 (5)0.0131 (10)0.0007 (7)
O20.0637 (14)0.0166 (9)0.0549 (14)0.0066 (8)0.0222 (11)0.0019 (9)
Geometric parameters (Å, º) top
N—C1.472 (4)C—H50.9700
N—H10.8900As—O11.705 (3)
N—H20.8900As—O21.806 (2)
N—H30.8900As—O2ii1.817 (3)
C—Ci1.520 (7)O2—Asiii1.817 (3)
C—H40.9700
C—N—H1109.5Ci—C—H4109.8
C—N—H2109.5N—C—H5109.8
H1—N—H2109.5Ci—C—H5109.8
C—N—H3109.5H4—C—H5108.2
H1—N—H3109.5O1—As—O299.04 (10)
H2—N—H3109.5O1—As—O2ii98.57 (13)
N—C—Ci109.5 (3)O2—As—O2ii93.93 (7)
N—C—H4109.8As—O2—Asiii123.99 (13)
O1—As—O2—Asiii96.58 (18)N—C—Ci—Ni180.0 (3)
O2ii—As—O2—Asiii2.76 (7)
Symmetry codes: (i) x+1/2, y, z+1; (ii) x+1, y1/2, z+1/2; (iii) x+1, y+1/2, z+1/2.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N—H1···O1iv0.892.102.905 (4)150
N—H1···O2v0.892.583.318 (4)140
N—H2···O1vi0.891.832.719 (3)174
N—H3···O10.891.822.701 (3)172
Symmetry codes: (iv) x+1/2, y+1/2, z+1/2; (v) x1/2, y+1, z; (vi) x, y1, z.
(II) sodium catena-arsenite top
Crystal data top
Na[AsO2]F(000) = 480
Mr = 129.91Dx = 3.497 Mg m3
Orthorhombic, PbcaMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2abCell parameters from 1514 reflections
a = 6.7762 (5) Åθ = 2.9–31.8°
b = 5.0901 (4) ŵ = 13.62 mm1
c = 14.3098 (11) ÅT = 293 K
V = 493.57 (7) Å3Rod, colourless
Z = 80.23 × 0.08 × 0.08 mm
Data collection top
Bruker SMART 1000 CCD area-detector
diffractometer
894 independent reflections
Radiation source: fine-focus sealed tube639 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.048
ω scansθmax = 32.5°, θmin = 2.9°
Absorption correction: multi-scan
(SADABS; Bruker, 1999)
h = 1010
Tmin = 0.120, Tmax = 0.336k = 76
5152 measured reflectionsl = 2118
Refinement top
Refinement on F20 restraints
Least-squares matrix: fullPrimary atom site location: structure-invariant direct methods
R[F2 > 2σ(F2)] = 0.040Secondary atom site location: difference Fourier map
wR(F2) = 0.109 w = 1/[σ2(Fo2) + (0.0661P)2]
where P = (Fo2 + 2Fc2)/3
S = 1.01(Δ/σ)max < 0.001
894 reflectionsΔρmax = 2.97 e Å3
37 parametersΔρmin = 1.05 e Å3
Crystal data top
Na[AsO2]V = 493.57 (7) Å3
Mr = 129.91Z = 8
Orthorhombic, PbcaMo Kα radiation
a = 6.7762 (5) ŵ = 13.62 mm1
b = 5.0901 (4) ÅT = 293 K
c = 14.3098 (11) Å0.23 × 0.08 × 0.08 mm
Data collection top
Bruker SMART 1000 CCD area-detector
diffractometer
894 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 1999)
639 reflections with I > 2σ(I)
Tmin = 0.120, Tmax = 0.336Rint = 0.048
5152 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.04037 parameters
wR(F2) = 0.1090 restraints
S = 1.01Δρmax = 2.97 e Å3
894 reflectionsΔρmin = 1.05 e Å3
Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Na0.3991 (3)0.7528 (4)0.55533 (19)0.0267 (5)
As0.39472 (7)0.73348 (8)0.32861 (3)0.01611 (17)
O10.5713 (5)0.7839 (7)0.4095 (3)0.0247 (8)
O20.1975 (5)0.9316 (6)0.3802 (2)0.0215 (7)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Na0.0154 (10)0.0268 (12)0.0378 (12)0.0011 (8)0.0046 (8)0.0028 (8)
As0.0130 (2)0.0133 (2)0.0219 (3)0.00103 (15)0.00058 (16)0.00031 (15)
O10.0142 (15)0.0276 (18)0.032 (2)0.0015 (13)0.0046 (13)0.0013 (13)
O20.0149 (15)0.0140 (14)0.036 (2)0.0041 (12)0.0021 (14)0.0030 (12)
Geometric parameters (Å, º) top
Na—O1i2.285 (4)As—O2v1.815 (3)
Na—O12.397 (5)As—O21.829 (3)
Na—O2ii2.413 (4)O1—Naii2.285 (4)
Na—O1iii2.420 (4)O1—Naiii2.420 (4)
Na—O1iv2.785 (4)O1—Naiv2.785 (4)
Na—O22.996 (4)O2—Asvi1.815 (3)
Na—O2v3.063 (4)O2—Nai2.413 (4)
As—O11.684 (4)O2—Navi3.063 (4)
O1i—Na—O1132.12 (15)O1—As—O299.07 (17)
O1i—Na—O2ii134.31 (15)O2v—As—O292.93 (11)
O1—Na—O2ii87.18 (14)As—O1—Naii146.0 (2)
O1i—Na—O1iii96.58 (15)As—O1—Na104.02 (17)
O1—Na—O1iii94.38 (13)Naii—O1—Na106.02 (15)
O2ii—Na—O1iii103.29 (14)As—O1—Naiii110.52 (18)
O1i—Na—O1iv87.13 (14)Naii—O1—Naiii87.31 (14)
O1—Na—O1iv100.80 (12)Na—O1—Naiii85.62 (13)
O2ii—Na—O1iv59.26 (11)As—O1—Naiv91.48 (15)
O1iii—Na—O1iv155.83 (19)Naii—O1—Naiv79.04 (13)
O1i—Na—O276.48 (12)Na—O1—Naiv79.20 (12)
O1—Na—O258.21 (12)Naiii—O1—Naiv155.83 (19)
O2ii—Na—O2145.10 (14)Asvi—O2—As123.66 (19)
O1iii—Na—O285.17 (12)Asvi—O2—Nai101.30 (15)
O1iv—Na—O2118.83 (12)As—O2—Nai123.50 (15)
O1i—Na—O2v85.93 (13)Asvi—O2—Na138.95 (16)
O1—Na—O2v55.03 (12)As—O2—Na80.62 (12)
O2ii—Na—O2v106.53 (11)Nai—O2—Na86.78 (11)
O1iii—Na—O2v135.08 (14)Asvi—O2—Navi78.89 (11)
O1iv—Na—O2v68.90 (10)As—O2—Navi141.29 (17)
O2—Na—O2v51.70 (7)Nai—O2—Navi73.47 (11)
O1—As—O2v95.42 (16)Na—O2—Navi64.85 (9)
Symmetry codes: (i) x1/2, y+3/2, z+1; (ii) x+1/2, y+3/2, z+1; (iii) x+1, y+2, z+1; (iv) x+1, y+1, z+1; (v) x+1/2, y1/2, z; (vi) x+1/2, y+1/2, z.

Experimental details

(I)(II)
Crystal data
Chemical formula(C2H10N2)0.5[AsO2]Na[AsO2]
Mr137.98129.91
Crystal system, space groupMonoclinic, I2/aOrthorhombic, Pbca
Temperature (K)293293
a, b, c (Å)12.7854 (8), 4.6647 (3), 13.3343 (9)6.7762 (5), 5.0901 (4), 14.3098 (11)
α, β, γ (°)90, 91.738 (1), 9090, 90, 90
V3)794.89 (9)493.57 (7)
Z88
Radiation typeMo KαMo Kα
µ (mm1)8.3713.62
Crystal size (mm)0.31 × 0.29 × 0.020.23 × 0.08 × 0.08
Data collection
DiffractometerBruker SMART 1000 CCD area-detector
diffractometer
Bruker SMART 1000 CCD area-detector
diffractometer
Absorption correctionMulti-scan
(SADABS; Bruker, 1999)
Multi-scan
(SADABS; Bruker, 1999)
Tmin, Tmax0.131, 0.8500.120, 0.336
No. of measured, independent and
observed [I > 2σ(I)] reflections
3520, 1430, 1181 5152, 894, 639
Rint0.0370.048
(sin θ/λ)max1)0.7570.757
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.039, 0.115, 1.05 0.040, 0.109, 1.01
No. of reflections1430894
No. of parameters4837
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)1.11, 1.682.97, 1.05

Computer programs: SMART (Bruker, 1999), SAINT (Bruker, 1999), SAINT, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ORTEP-3 (Farrugia, 1997) and ATOMS (Dowty, 1999), SHELXL97.

Selected geometric parameters (Å, º) for (I) top
As—O11.705 (3)As—O2i1.817 (3)
As—O21.806 (2)
O1—As—O299.04 (10)O2—As—O2i93.93 (7)
O1—As—O2i98.57 (13)As—O2—Asii123.99 (13)
Symmetry codes: (i) x+1, y1/2, z+1/2; (ii) x+1, y+1/2, z+1/2.
Hydrogen-bond geometry (Å, º) for (I) top
D—H···AD—HH···AD···AD—H···A
N—H1···O1iii0.892.102.905 (4)150
N—H1···O2iv0.892.583.318 (4)140
N—H2···O1v0.891.832.719 (3)174
N—H3···O10.891.822.701 (3)172
Symmetry codes: (iii) x+1/2, y+1/2, z+1/2; (iv) x1/2, y+1, z; (v) x, y1, z.
Selected geometric parameters (Å, º) for (II) top
Na—O1i2.285 (4)Na—O22.996 (4)
Na—O12.397 (5)Na—O2v3.063 (4)
Na—O2ii2.413 (4)As—O11.684 (4)
Na—O1iii2.420 (4)As—O2v1.815 (3)
Na—O1iv2.785 (4)As—O21.829 (3)
O1—As—O2v95.42 (16)O2v—As—O292.93 (11)
O1—As—O299.07 (17)Asvi—O2—As123.66 (19)
Symmetry codes: (i) x1/2, y+3/2, z+1; (ii) x+1/2, y+3/2, z+1; (iii) x+1, y+2, z+1; (iv) x+1, y+1, z+1; (v) x+1/2, y1/2, z; (vi) x+1/2, y+1/2, z.
 

References

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