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

Lee, C.; Harrison, W.T.A.

doi:10.1107/S0108270104007450

metal-organic compounds

STRUCTURAL
CHEMISTRY

ISSN: 2053-2296

Volume 60| Part 5| May 2004| Pages m215-m218

doi:10.1107/S0108270104007450

The catena-arsenite chain anion, [AsO₂]_nⁿ⁻: (H₃NCH₂CH₂NH₃)_0.5[AsO₂] and NaAsO₂ (revisited)

Clare Lee ^a and William T. A. Harrison ^a ^*

^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 As^III 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 ). 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 As^III species, with an electron configuration of [core]4s²4p¹. This geometry is quite distinct from the tetrahedral coordination invariably displayed by the [As^VO₄]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 ), 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 ).

We describe here 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).

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 Å⁻³) 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—O_T bond in (I) [1.705 (3) Å] is distinctly shorter than the average of the bridging bonds [mean As—O_B = 1.812 (2) Å]. The O_B—As—O_B bond angle is significantly smaller than the O_B—As—O_T 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, O_T accepts three hydrogen bonds and O_B 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. Interchain linking along [001] is via the backbone of the organic moiety. The intrachain As⋯Asⁱ separation in (I) is 3.1991 (4) Å [symmetry code: (i) 1 − x, y − $[{1 \over 2}]$ , $[{1 \over 2}]$ − 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—O_T = 1.684 (4) Å and mean As—O_B = 1.822 (3) Å] are similar to those found for (I). As in (I), the O_B—As—O_B bond angle is significantly smaller than the O_B—As—O_T bond angles (Table 3). By comparison, Menary's (1958) results (As—O_T = 1.600 Å, and As—O_B = 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) $[{1 \over 2}]$ − 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 As^III 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), 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—O_B bond lengths are clustered in the narrow range of 1.806 (2)–1.829 (3) Å. The As—O_T bond lengths show somewhat greater variability, which might be due to the different bonding situations of the O atoms in question: the O_T atom in (I) [1.705 (3) Å] only accepts hydrogen bonds, whereas the O_T atom in CuAs₂O₄ (1.765 Å) is also bonded to two Cu atoms. However, there are also some significant differences. For example, the O_B—As—O_B bond angle of 100.3° in CuAs₂O₄ is significantly larger than the O_B—As—O_T bond angle (95.9°), which is the reverse of the situation for (I), (II) and ZnAs₂O₄ (Ghose et al., 1987).

Figure 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) $[{1 \over 2}]$ − x, y, 1 − z; (ii) 1 − x, y − $[{1 \over 2}]$ , $[{1 \over 2}]$ − z; (iii) x, y − 1, z.]

Figure 2
The unit-cell packing in (I

), projected on to (010) (normal to the catena-arsenite chain direction). Hydrogen bonds are indicated by dashed lines.

Figure 3
A view of a fragment of (II

), drawn with 50% probability displacement ellipsoids. Note that atoms O1, O2 and O2^v represent a face shared between the AsO₃ and NaO₇ polyhedra. [Symmetry codes are as in Table 3

; additionally: (vii) $[{1 \over 2}]$ − x, y + $[{1 \over 2}]$ , z.]

Figure 4
A polyhedral representation of the unit-cell packing in (II

), 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), 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) 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.

Compound (I)

Crystal data

(C₂H₁₀N₂)_0.5[AsO₂]
M_r = 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
D_x = 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 ) T_min = 0.131, T_max = 0.850
3520 measured reflections
1430 independent reflections
1181 reflections with I > 2σ(I)
R_int = 0.037
θ_max = 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(F_o²) + (0.0792P)² + 0.139P] where P = (F_o² + 2F_c²)/3
(Δ/σ)_max < 0.001
Δρ_max = 1.11 e Å⁻³
Δρ_min = −1.68 e Å⁻³
Extinction correction: SHELXL97 (Sheldrick, 1997 )
Extinction coefficient: 0.0032 (8)

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

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)

D—H⋯A	D—H	H⋯A	D⋯A	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)

Crystal data

Na[AsO₂]
M_r = 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
D_x = 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) T_min = 0.120, T_max = 0.336
5152 measured reflections
894 independent reflections
639 reflections with I > 2σ(I)
R_int = 0.048
θ_max = 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(F_o²) + (0.0661P)²] where P = (F_o² + 2F_c²)/3
(Δ/σ)_max < 0.001
Δρ_max = 2.97 e Å⁻³
Δρ_min = −1.05 e Å⁻³

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

Na—O1ⁱ	2.285 (4)
Na—O1	2.397 (5)
Na—O2ⁱⁱ	2.413 (4)
Na—O1ⁱⁱⁱ	2.420 (4)
Na—O1^iv	2.785 (4)
Na—O2	2.996 (4)
Na—O2^v	3.063 (4)
As—O1	1.684 (4)
As—O2^v	1.815 (3)
As—O2	1.829 (3)

O1—As—O2^v	95.42 (16)
O1—As—O2	99.07 (17)
O2^v—As—O2	92.93 (11)
As^vi—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), 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 U_iso(H) = 1.2U_eq(attached atom) was applied in all cases. For (II), the maximum difference peak was 0.82 Å from As.

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 for Windows (Farrugia, 1997 ) and ATOMS (Dowty, 1999 ); software used to prepare material for publication: SHELXL97.

Supporting information

Crystal structure: contains datablocks I, II, global. DOI: 10.1107/S0108270104007450/bc1044sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S0108270104007450/bc1044Isup2.hkl

Structure factors: contains datablock II. DOI: 10.1107/S0108270104007450/bc1044IIsup3.hkl

Comment top

The [AsO₃]³⁻ arsenite group shows a distinctive pyramidal geometry, due to the stereochemically active lone pair of electrons on the As^III species, with an electron configuration of [core]4 s²4p¹. This geometry is quite distinct from the tetrahedral coordination invariably displayed by the [As^VO₄]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]_n^n-), 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—O_T bond in (I) [1.705 (3) Å] is distinctly shorter than the average of the bridging bonds [mean As—O_B 1.812 (2) Å]. The O_B—As—O_B bond angle is significantly smaller than the O_B—As—O_T 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, O_T accepts three H bonds and O_B 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—O_T 1.684 (4) Å and mean As—O_B 1.822 (3) Å] are similar to those found for (I). As in (I), the O_B—As—O_B bond angle is significantly smaller than the O_B—As—O_T bond angles (Table 3). By comparison, Menary's (1958) results (As—O_T 1.600 Å, and As—O_B 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 As^III 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.

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.

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

	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.]
	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.
	Fig. 3. A view of a fragment of (II), drawn with 50% probability displacement ellipsoids. Note that atoms O1, O2 and O2^v 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.]
	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
M_r = 137.98	D_x = 2.306 Mg m⁻³
Monoclinic, I2/a	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -I 2ya	Cell parameters from 2219 reflections
a = 12.7854 (8) Å	θ = 3.1–32.5°
b = 4.6647 (3) Å	µ = 8.37 mm⁻¹
c = 13.3343 (9) Å	T = 293 K
β = 91.738 (1)°	Plate, colourless
V = 794.89 (9) Å³	0.31 × 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 tube	1181 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.037
ω scans	θ_max = 32.5°, θ_min = 3.1°
Absorption correction: multi-scan (SADABS; Bruker, 1999)	h = −16→19
T_min = 0.131, T_max = 0.850	k = −7→5
3520 measured reflections	l = −19→20

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.039	H-atom parameters constrained
wR(F²) = 0.115	w = 1/[σ²(F_o²) + (0.0792P)² + 0.139P] where P = (F_o² + 2F_c²)/3
S = 1.05	(Δ/σ)_max < 0.001
1430 reflections	Δρ_max = 1.11 e Å⁻³
48 parameters	Δρ_min = −1.68 e Å⁻³
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 1997), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0032 (8)

Crystal data top

(C₂H₁₀N₂)_0.5[AsO₂]	V = 794.89 (9) Å³
M_r = 137.98	Z = 8
Monoclinic, I2/a	Mo Kα radiation
a = 12.7854 (8) Å	µ = 8.37 mm⁻¹
b = 4.6647 (3) Å	T = 293 K
c = 13.3343 (9) Å	0.31 × 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)
T_min = 0.131, T_max = 0.850	R_int = 0.037
3520 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.039	0 restraints
wR(F²) = 0.115	H-atom parameters constrained
S = 1.05	Δρ_max = 1.11 e Å⁻³
1430 reflections	Δρ_min = −1.68 e Å⁻³
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

	x	y	z	U_iso*/U_eq
N	0.2497 (2)	0.0011 (4)	0.3599 (2)	0.0275 (5)
H1	0.1979	0.0032	0.3138	0.041*
H2	0.2883	−0.1557	0.3522	0.041*
H3	0.2896	0.1558	0.3528	0.041*
C	0.2058 (2)	0.0010 (5)	0.4606 (2)	0.0280 (6)
H4	0.1624	−0.1675	0.4688	0.034*
H5	0.1624	0.1695	0.4688	0.034*
As	0.48708 (2)	0.51719 (5)	0.33079 (2)	0.02731 (15)
O1	0.3543 (2)	0.4989 (3)	0.3369 (2)	0.0352 (5)
O2	0.49976 (18)	0.8904 (5)	0.29703 (19)	0.0446 (6)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
N	0.0311 (12)	0.0232 (11)	0.0283 (11)	−0.0023 (6)	0.0027 (9)	0.0009 (6)
C	0.0241 (12)	0.0331 (15)	0.0269 (12)	0.0000 (7)	0.0034 (9)	0.0002 (8)
As	0.0255 (2)	0.01769 (18)	0.0387 (2)	−0.00149 (7)	0.00033 (13)	0.00244 (8)
O1	0.0280 (11)	0.0219 (10)	0.0565 (16)	−0.0018 (5)	0.0131 (10)	−0.0007 (7)
O2	0.0637 (14)	0.0166 (9)	0.0549 (14)	−0.0066 (8)	0.0222 (11)	−0.0019 (9)

Geometric parameters (Å, º) top

N—C	1.472 (4)	C—H5	0.9700
N—H1	0.8900	As—O1	1.705 (3)
N—H2	0.8900	As—O2	1.806 (2)
N—H3	0.8900	As—O2ⁱⁱ	1.817 (3)
C—Cⁱ	1.520 (7)	O2—Asⁱⁱⁱ	1.817 (3)
C—H4	0.9700

C—N—H1	109.5	Cⁱ—C—H4	109.8
C—N—H2	109.5	N—C—H5	109.8
H1—N—H2	109.5	Cⁱ—C—H5	109.8
C—N—H3	109.5	H4—C—H5	108.2
H1—N—H3	109.5	O1—As—O2	99.04 (10)
H2—N—H3	109.5	O1—As—O2ⁱⁱ	98.57 (13)
N—C—Cⁱ	109.5 (3)	O2—As—O2ⁱⁱ	93.93 (7)
N—C—H4	109.8	As—O2—Asⁱⁱⁱ	123.99 (13)

O1—As—O2—Asⁱⁱⁱ	−96.58 (18)	N—C—Cⁱ—Nⁱ	180.0 (3)
O2ⁱⁱ—As—O2—Asⁱⁱⁱ	2.76 (7)

Symmetry codes: (i) −x+1/2, y, −z+1; (ii) −x+1, y−1/2, −z+1/2; (iii) −x+1, y+1/2, −z+1/2.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N—H1···O1^iv	0.89	2.10	2.905 (4)	150
N—H1···O2^v	0.89	2.58	3.318 (4)	140
N—H2···O1^vi	0.89	1.83	2.719 (3)	174
N—H3···O1	0.89	1.82	2.701 (3)	172

Symmetry codes: (iv) −x+1/2, −y+1/2, −z+1/2; (v) x−1/2, −y+1, z; (vi) x, y−1, z.

(II) sodium catena-arsenite top

Crystal data top

Na[AsO₂]	F(000) = 480
M_r = 129.91	D_x = 3.497 Mg m⁻³
Orthorhombic, Pbca	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2ab	Cell parameters from 1514 reflections
a = 6.7762 (5) Å	θ = 2.9–31.8°
b = 5.0901 (4) Å	µ = 13.62 mm⁻¹
c = 14.3098 (11) Å	T = 293 K
V = 493.57 (7) Å³	Rod, colourless
Z = 8	0.23 × 0.08 × 0.08 mm

Data collection top

Bruker SMART 1000 CCD area-detector diffractometer	894 independent reflections
Radiation source: fine-focus sealed tube	639 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.048
ω scans	θ_max = 32.5°, θ_min = 2.9°
Absorption correction: multi-scan (SADABS; Bruker, 1999)	h = −10→10
T_min = 0.120, T_max = 0.336	k = −7→6
5152 measured reflections	l = −21→18

Refinement top

Refinement on F²	0 restraints
Least-squares matrix: full	Primary atom site location: structure-invariant direct methods
R[F² > 2σ(F²)] = 0.040	Secondary atom site location: difference Fourier map
wR(F²) = 0.109	w = 1/[σ²(F_o²) + (0.0661P)²] where P = (F_o² + 2F_c²)/3
S = 1.01	(Δ/σ)_max < 0.001
894 reflections	Δρ_max = 2.97 e Å⁻³
37 parameters	Δρ_min = −1.05 e Å⁻³

Crystal data top

Na[AsO₂]	V = 493.57 (7) Å³
M_r = 129.91	Z = 8
Orthorhombic, Pbca	Mo Kα radiation
a = 6.7762 (5) Å	µ = 13.62 mm⁻¹
b = 5.0901 (4) Å	T = 293 K
c = 14.3098 (11) Å	0.23 × 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)
T_min = 0.120, T_max = 0.336	R_int = 0.048
5152 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.040	37 parameters
wR(F²) = 0.109	0 restraints
S = 1.01	Δρ_max = 2.97 e Å⁻³
894 reflections	Δρ_min = −1.05 e Å⁻³

Special details top

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Na	0.3991 (3)	0.7528 (4)	0.55533 (19)	0.0267 (5)
As	0.39472 (7)	0.73348 (8)	0.32861 (3)	0.01611 (17)
O1	0.5713 (5)	0.7839 (7)	0.4095 (3)	0.0247 (8)
O2	0.1975 (5)	0.9316 (6)	0.3802 (2)	0.0215 (7)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Na	0.0154 (10)	0.0268 (12)	0.0378 (12)	0.0011 (8)	0.0046 (8)	0.0028 (8)
As	0.0130 (2)	0.0133 (2)	0.0219 (3)	−0.00103 (15)	0.00058 (16)	0.00031 (15)
O1	0.0142 (15)	0.0276 (18)	0.032 (2)	−0.0015 (13)	−0.0046 (13)	−0.0013 (13)
O2	0.0149 (15)	0.0140 (14)	0.036 (2)	0.0041 (12)	0.0021 (14)	0.0030 (12)

Geometric parameters (Å, º) top

Na—O1ⁱ	2.285 (4)	As—O2^v	1.815 (3)
Na—O1	2.397 (5)	As—O2	1.829 (3)
Na—O2ⁱⁱ	2.413 (4)	O1—Naⁱⁱ	2.285 (4)
Na—O1ⁱⁱⁱ	2.420 (4)	O1—Naⁱⁱⁱ	2.420 (4)
Na—O1^iv	2.785 (4)	O1—Na^iv	2.785 (4)
Na—O2	2.996 (4)	O2—As^vi	1.815 (3)
Na—O2^v	3.063 (4)	O2—Naⁱ	2.413 (4)
As—O1	1.684 (4)	O2—Na^vi	3.063 (4)

O1ⁱ—Na—O1	132.12 (15)	O1—As—O2	99.07 (17)
O1ⁱ—Na—O2ⁱⁱ	134.31 (15)	O2^v—As—O2	92.93 (11)
O1—Na—O2ⁱⁱ	87.18 (14)	As—O1—Naⁱⁱ	146.0 (2)
O1ⁱ—Na—O1ⁱⁱⁱ	96.58 (15)	As—O1—Na	104.02 (17)
O1—Na—O1ⁱⁱⁱ	94.38 (13)	Naⁱⁱ—O1—Na	106.02 (15)
O2ⁱⁱ—Na—O1ⁱⁱⁱ	103.29 (14)	As—O1—Naⁱⁱⁱ	110.52 (18)
O1ⁱ—Na—O1^iv	87.13 (14)	Naⁱⁱ—O1—Naⁱⁱⁱ	87.31 (14)
O1—Na—O1^iv	100.80 (12)	Na—O1—Naⁱⁱⁱ	85.62 (13)
O2ⁱⁱ—Na—O1^iv	59.26 (11)	As—O1—Na^iv	91.48 (15)
O1ⁱⁱⁱ—Na—O1^iv	155.83 (19)	Naⁱⁱ—O1—Na^iv	79.04 (13)
O1ⁱ—Na—O2	76.48 (12)	Na—O1—Na^iv	79.20 (12)
O1—Na—O2	58.21 (12)	Naⁱⁱⁱ—O1—Na^iv	155.83 (19)
O2ⁱⁱ—Na—O2	145.10 (14)	As^vi—O2—As	123.66 (19)
O1ⁱⁱⁱ—Na—O2	85.17 (12)	As^vi—O2—Naⁱ	101.30 (15)
O1^iv—Na—O2	118.83 (12)	As—O2—Naⁱ	123.50 (15)
O1ⁱ—Na—O2^v	85.93 (13)	As^vi—O2—Na	138.95 (16)
O1—Na—O2^v	55.03 (12)	As—O2—Na	80.62 (12)
O2ⁱⁱ—Na—O2^v	106.53 (11)	Naⁱ—O2—Na	86.78 (11)
O1ⁱⁱⁱ—Na—O2^v	135.08 (14)	As^vi—O2—Na^vi	78.89 (11)
O1^iv—Na—O2^v	68.90 (10)	As—O2—Na^vi	141.29 (17)
O2—Na—O2^v	51.70 (7)	Naⁱ—O2—Na^vi	73.47 (11)
O1—As—O2^v	95.42 (16)	Na—O2—Na^vi	64.85 (9)

Symmetry codes: (i) x−1/2, −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, y−1/2, z; (vi) −x+1/2, y+1/2, z.

Experimental details

	(I)	(II)
Crystal data
Chemical formula	(C₂H₁₀N₂)_0.5[AsO₂]	Na[AsO₂]
M_r	137.98	129.91
Crystal system, space group	Monoclinic, I2/a	Orthorhombic, Pbca
Temperature (K)	293	293
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), 90	90, 90, 90
V (Å³)	794.89 (9)	493.57 (7)
Z	8	8
Radiation type	Mo Kα	Mo Kα
µ (mm⁻¹)	8.37	13.62
Crystal size (mm)	0.31 × 0.29 × 0.02	0.23 × 0.08 × 0.08

Data collection
Diffractometer	Bruker SMART 1000 CCD area-detector diffractometer	Bruker SMART 1000 CCD area-detector diffractometer
Absorption correction	Multi-scan (SADABS; Bruker, 1999)	Multi-scan (SADABS; Bruker, 1999)
T_min, T_max	0.131, 0.850	0.120, 0.336
No. of measured, independent and observed [I > 2σ(I)] reflections	3520, 1430, 1181	5152, 894, 639
R_int	0.037	0.048
(sin θ/λ)_max (Å⁻¹)	0.757	0.757

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.039, 0.115, 1.05	0.040, 0.109, 1.01
No. of reflections	1430	894
No. of parameters	48	37
H-atom treatment	H-atom parameters constrained	–
Δρ_max, Δρ_min (e Å⁻³)	1.11, −1.68	2.97, −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—O1	1.705 (3)	As—O2ⁱ	1.817 (3)
As—O2	1.806 (2)

O1—As—O2	99.04 (10)	O2—As—O2ⁱ	93.93 (7)
O1—As—O2ⁱ	98.57 (13)	As—O2—Asⁱⁱ	123.99 (13)

Symmetry codes: (i) −x+1, y−1/2, −z+1/2; (ii) −x+1, y+1/2, −z+1/2.

Hydrogen-bond geometry (Å, º) for (I) top

D—H···A	D—H	H···A	D···A	D—H···A
N—H1···O1ⁱⁱⁱ	0.89	2.10	2.905 (4)	150
N—H1···O2^iv	0.89	2.58	3.318 (4)	140
N—H2···O1^v	0.89	1.83	2.719 (3)	174
N—H3···O1	0.89	1.82	2.701 (3)	172

Symmetry codes: (iii) −x+1/2, −y+1/2, −z+1/2; (iv) x−1/2, −y+1, z; (v) x, y−1, z.

Selected geometric parameters (Å, º) for (II) top

Na—O1ⁱ	2.285 (4)	Na—O2	2.996 (4)
Na—O1	2.397 (5)	Na—O2^v	3.063 (4)
Na—O2ⁱⁱ	2.413 (4)	As—O1	1.684 (4)
Na—O1ⁱⁱⁱ	2.420 (4)	As—O2^v	1.815 (3)
Na—O1^iv	2.785 (4)	As—O2	1.829 (3)

O1—As—O2^v	95.42 (16)	O2^v—As—O2	92.93 (11)
O1—As—O2	99.07 (17)	As^vi—O2—As	123.66 (19)

Symmetry codes: (i) x−1/2, −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, y−1/2, z; (vi) −x+1/2, y+1/2, z.

References

Araki, T., Moore, P. B. & Brunton, G. D. (1980). Am. Mineral. 65, 340–345. CAS Google Scholar
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ISSN: 2053-2296

Volume 60| Part 5| May 2004| Pages m215-m218

doi:10.1107/S0108270104007450

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