Tetra­ethyl­ammonium dihydrogen­arsenate bis­(arsenic acid) and 1,4-­diazo­niabicyclo­[2.2.2]octane bis(dihydrogenarsenate) arsenic acid: hydrogen-bonded networks containing dihydrogenarsenate anions and neutral arsenic acid mol­ecules

The title compounds, (C₈H₂₀N)[H₂AsO₄][H₃AsO₄]₂, (I), and (C₆H₁₄N₂)[H₂AsO₄]₂[H₃AsO₄], (II), are unusual salts containing organic cations, dihydrogenarsenate anions and neutral arsenic acid mol­ecules. In (I), the dihydrogenarsenate anion lies across a twofold rotation axis in the space group C2/­c, while the cation is disordered across a centre of inversion. The [H₂AsO₄]⁻ and H₃AsO₄ species inter­act by way of O—H...O hydrogen bonds, leading to sheets and a three-dimensional network for (I) and (II), respectively.

S1. Comment

Only a handful of crystal structures containing the neutral arsenic acid (H₃AsO₄) molecule have been determined, including N,N,N-trimetlylglycine (beatine) arsenic acid (Schildkamp et al., 1984), tetraphenylphosphonium chloride arsenic acid (Ruhlandt-Senge et al., 1992), L-histininium dihydrogen arsenate arsenic acid (Ratajczak et al., 2000) and DL-threonine arsenic acid 1:1 (Wilkinson & Harrison, 2005). We present here the syntheses and structures of the title compounds, (C₈H₂₀N)[H₂AsO₄][H₃AsO₄]₂, (I), and (C₆H₁₄N₂)[H₂AsO₄]₂[H₃AsO₄], (II), which both contain organic cations, dihydrogenarsenate anions and neutral arsenic acid molecules.

The structure of (I) (Fig. 1) is built up from C₈H₂₀N⁺ tetraethylammonium (TEA) cations, [H₂AsO₄]^- dihydrogenarsenate anions and neutral H₃AsO₄ arsenic acid molecules in a 1:1:2 ratio. The N atom of the cation occupies a special position with site symmetry 1; thus the –CH₂CH₃ arms of the TEA species are disordered, as is often seen for this cation (Majumdar et al., 2006). The dihydrogenarsenate anion, containing As1, lies across a twofold rotation axis. The short and long As1—O bonds (Table 1) correspond to unprotonated As—O vertices with partial double bond character and to protonated AsOH groups, respectively. The neutral arsenic acid molecule in (I), containing As2, with a mean As—O distance of 1.678 (2) Å], contains one short, formal double bond (As2═O4) and three longer As—OH vertices, as seen in related structures (Wilkinson & Harrison, 2005).

As well as Coulombic and van der Waals forces, the component species in (I) interact by means of a network of O—H···O hydrogen bonds. All these bonds are short and near linear (Table 2). Pairs of arsenic acid molecules form inversion dimers via O6—H4···O4ⁱⁱⁱ + O6ⁱⁱⁱ—H4ⁱⁱⁱ···O4 links (see Table 2 for symmetry codes. Similar dimers built up from [H₂AsO₄]^- units have been seen in propane-1,2-diamminium hydrogenarsenate (Todd & Harrison, 2005). The As1-centred anion then serves to link the As2 dimers, by donating two O—H···O bonds and accepting two O—H···O bonds, into a sheet of tetrahedra propagating in (001) (Fig. 2). A number of unusual graph-set (Bernstein et al., 1995) loops occur within these arsenate sheets, including R²₃(10), R²₄(12) and R⁴₄(16) circuits, as well as the more familiar R²₂(8) inversion dimer arising from the As2 units.

The arsenate sheets sandwich the disordered organic cations in (I) (Fig. 3) to result in alternating inorganic and organic layers with respect to the c direction.

Compound (II) contains C₂H₁₄N₂²⁺ 1,4-diazoniabicyclo[2.2.2]octane dications accompanied by dihydrogenarsenate anions and arsenic acid molecules (Fig. 4), with all atoms occupying general crystallographic positions. Because the organic cation is divalent, a 1:2:1 ratio of C₂H₁₄N₂²⁺:H₂AsO₄^-:H₃AsO₄ arises in (II). As in (I), the individual arsenate As—O bond lengths correlate with their protonation state (Table 3). The mean As—O distances for the As1, As2 and As3 (arsenic acid) tetrahedra are 1.679 (2), 1.681 (2) and 1.674 (2) Å, respectively

In (II), the As2-centred dihydrogenarsenate groups form inversion dimers via O—H···O bonds, which contrasts with (I), where the arsenic acid molecules formed similar dimers. The dimers are fused by further O—H···O hydrogen bonds (Table 4) to form chains of alternating As1- and As3-centred units, to result in slabs of tetrahedra propagating in [100] (Fig. 5). The graph-set loops found within the arsenate slabs in (II) include R²₂(8) inversion dimers, and R²₃(12), R³₃(12) and large R⁶₆(24) circuits.

The [100] slabs are crosslinked by the key O10—H10···O4ⁱⁱⁱ bond (Table 4), to result in a three-dimensional hydorgen-bonded network encompassing [100] channels occupied by the organic cations. These very large channels can accommodate two organic cations side-by-side and are characterized by an R⁸₁₂(40) graph-set motif. In turn, the cations interact with the tetrahedral framework by way of N—H···O hydrogen bonds (Table 4). A related supramolecular hydrogen-bonded tetrahedral framework encapsulating organic cations was seen in 2-aminopyridinium dihydrogenphosphate (Czapla et al., 2003).

Related literature

For related literature, see: Bernstein et al. (1995); Czapla et al. (2003); Majumdar et al. (2006); Ratajczak et al. (2000); Ruhlandt-Senge, Bacher & Müller (1992); Schildkamp et al. (1984); Todd & Harrison (2005); Wilkinson & Harrison (2005).

S2. Experimental

For (I), 10 ml each of 0.5 mol dm^-3 aqueous solutions of tetraethylammonium hydroxide (TEAOH) and arsenic acid were mixed in a Petri dish, resulting in a clear solution. Colourless rods and bars of (I) grew over a few days, as the water evaporated. For (II), a 0.5 mol dm^-3 aqueous 1,4-diazabicyclo[2.2.2]octane solution (10 ml) replaced the TEAOH solution, and colourless blocks of (II) were formed using the same experimental procedure as for (I).

S3. Refinement

The methylene groups of the organic molecule in (I) are disordered over two conformations, required to have equal occupancies by symmetry. Their H atoms were geometrically placed (C—H = 0.97 Å) and refined as riding. The H atoms of the terminal methyl groups were placed in two orientations (C—H = 0.92–0.98 Å), to achieve reasonable C—C—H angles for both disorder components of the bridging methylene groups, and refined as riding. For (II), the C– and N-bound H atoms were geometrically placed (C—H = 0.97 Å, N—H = 0.91 Å) and refined as riding atoms. For both (I) and (II), the O-bound H atoms were located in difference maps and refined as riding atoms in the positions found from the difference maps, giving a range of O—H distances of 0.83–0.96 Å. For both (I) and (II), U_iso(H) values were set at 1.2U_eq(carrier) or 1.5U_eq(methyl C).

Computing details

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 (Shape Software, 2000); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. The molecular structure of (I) (50% probability displacement ellipsoids; H atoms are drawn as spheres of arbitrary radii). The intramolecular hydrogen bond is indicated by dashed lines. [Symmetry codes: (i) -x, y, 1/2 - z; (ii) 1/2 - x, 1/2 - y, -z.]
	Fig. 2. Part of a hydrogen-bonded sheet of tetrahedra in (I), shown in polyhedral representation, with the inter-tetrahedral hydrogen bonds shown as thin lines.
	Fig. 3. The packing in (I), viewed down [010], with the H atoms of the organic species omitted for clarity and hydrogen bonds indicated by thin lines.
	Fig. 4. The molecular structure of (II) (50% probability displacement ellipsoids; H atoms are drawn as spheres of arbitrary radii). Hydrogen bonds are indicated by dashed lines. Note the distinctive `three-ring' of tetrahedra, leading to an R^33(12) loop.
	Fig. 5. Part of a hydrogen-bonded [100] slab of tetrahedra in (II), shown in polyhedral representation, with the inter-tetrahedral O—H···O hydrogen bonds shown as thin lines.
	Fig. 6. The packing in (I), viewed down [100], with the H atoms of the organic species omitted for clarity.

(I) Tetraethylammonium dihydrogenarsenate bis(arsenic acid) and 1,4-diazoniabicyclo[2.2.2]octane bis(dihydrogenarsenate) arsenic acid. ?

Crystal data

(C8H20N)[H2AsO4][H3AsO4]2	F(000) = 1112
Mr = 555.08	Dx = 1.834 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 2724 reflections
a = 20.0518 (13) Å	θ = 2.3–29.6°
b = 7.3138 (4) Å	µ = 5.01 mm^−1
c = 15.251 (1) Å	T = 293 K
β = 115.969 (1)°	Rod, colourless
V = 2010.7 (2) Å^3	0.25 × 0.08 × 0.06 mm
Z = 4

Data collection

Bruker SMART 1000 CCD diffractometer	3610 independent reflections
Radiation source: fine-focus sealed tube	2301 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.032
ω scans	θmax = 32.5°, θmin = 2.3°
Absorption correction: multi-scan (SADABS; Bruker, 1999)	h = −30→30
Tmin = 0.360, Tmax = 0.739	k = −11→8
9940 measured reflections	l = −18→23

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.031	H-atom parameters constrained
wR(F^2) = 0.066	w = 1/[σ^2(Fo^2) + (0.0287P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 0.86	(Δ/σ)max = 0.001
3610 reflections	Δρmax = 0.65 e Å^−3
130 parameters	Δρmin = −0.43 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.00088 (8)

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
As1	0.0000	0.24048 (4)	0.2500	0.03836 (10)
O1	0.01538 (10)	0.1174 (2)	0.34778 (11)	0.0469 (4)
O2	0.07580 (11)	0.3764 (2)	0.28257 (12)	0.0637 (6)
H1	0.0750	0.4231	0.2308	0.076*
As2	0.055937 (13)	0.28268 (3)	0.583774 (16)	0.03564 (8)
O3	0.10288 (9)	0.2190 (2)	0.51990 (13)	0.0530 (5)
H2	0.0738	0.1825	0.4586	0.064*
O4	0.07940 (10)	0.4933 (2)	0.62311 (12)	0.0470 (4)
O5	0.07817 (10)	0.1406 (2)	0.67900 (12)	0.0625 (5)
H3	0.0422	0.0600	0.6622	0.075*
O6	−0.03622 (9)	0.2541 (2)	0.51201 (12)	0.0491 (4)
H4	−0.0491	0.3282	0.4577	0.059*
N1	0.2500	0.2500	0.0000	0.0402 (6)
C4	0.3162 (3)	0.3614 (7)	0.0706 (4)	0.0499 (13)	0.50
H4A	0.3484	0.3934	0.0406	0.060*	0.50
H4B	0.3446	0.2920	0.1295	0.060*	0.50
C5	0.2144 (3)	0.4283 (6)	0.0171 (4)	0.0497 (13)	0.50
H5A	0.1784	0.3985	0.0414	0.060*	0.50
H5B	0.1894	0.4956	−0.0435	0.060*	0.50
C6	0.2811 (2)	0.5485 (4)	0.0962 (3)	0.0843 (11)
H6A	0.3212	0.6229	0.1405	0.126*	0.50
H6B	0.2494	0.5156	0.1260	0.126*	0.50
H6C	0.2532	0.6158	0.0374	0.126*	0.50
H6D	0.2593	0.6540	0.1080	0.126*	0.50
H6E	0.3148	0.5706	0.0716	0.126*	0.50
H6F	0.3025	0.4737	0.1550	0.126*	0.50
C1	0.2001 (3)	0.1994 (7)	0.0470 (4)	0.0550 (14)	0.50
H1A	0.1621	0.1161	0.0045	0.066*	0.50
H1B	0.1757	0.3087	0.0545	0.066*	0.50
C2	0.2936 (3)	0.1534 (7)	0.0926 (4)	0.0576 (14)	0.50
H2A	0.3353	0.2288	0.1340	0.069*	0.50
H2B	0.3129	0.0406	0.0794	0.069*	0.50
C3	0.2437 (2)	0.1074 (5)	0.1491 (2)	0.0892 (11)
H3A	0.2100	0.0784	0.1764	0.134*	0.50
H3B	0.2810	0.1901	0.1918	0.134*	0.50
H3C	0.2669	−0.0026	0.1419	0.134*	0.50
H3D	0.2761	0.0438	0.2084	0.134*	0.50
H3E	0.2059	0.0279	0.1078	0.134*	0.50
H3F	0.2262	0.2157	0.1628	0.134*	0.50

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
As1	0.0547 (2)	0.03502 (18)	0.02475 (16)	0.000	0.01683 (15)	0.000
O1	0.0669 (12)	0.0438 (9)	0.0266 (8)	−0.0077 (8)	0.0173 (8)	0.0030 (7)
O2	0.0782 (15)	0.0663 (12)	0.0393 (10)	−0.0273 (10)	0.0190 (10)	0.0010 (8)
As2	0.03761 (13)	0.03770 (13)	0.02809 (12)	−0.00035 (10)	0.01113 (10)	0.00172 (9)
O3	0.0407 (10)	0.0749 (12)	0.0401 (10)	0.0053 (8)	0.0147 (8)	−0.0164 (8)
O4	0.0588 (12)	0.0369 (9)	0.0394 (9)	0.0004 (8)	0.0162 (8)	−0.0043 (7)
O5	0.0643 (13)	0.0636 (12)	0.0387 (10)	−0.0163 (10)	0.0031 (9)	0.0174 (8)
O6	0.0372 (10)	0.0630 (11)	0.0423 (10)	−0.0071 (8)	0.0131 (8)	0.0104 (7)
N1	0.0263 (13)	0.0474 (16)	0.0410 (16)	−0.0019 (11)	0.0094 (12)	0.0008 (11)
C4	0.038 (3)	0.060 (3)	0.043 (3)	−0.016 (2)	0.010 (2)	−0.002 (2)
C5	0.042 (3)	0.048 (3)	0.058 (3)	0.009 (2)	0.021 (3)	0.004 (2)
C6	0.111 (3)	0.0551 (19)	0.092 (3)	−0.0263 (19)	0.048 (2)	−0.0258 (17)
C1	0.034 (3)	0.062 (3)	0.074 (4)	−0.013 (2)	0.029 (3)	−0.008 (3)
C2	0.044 (3)	0.056 (3)	0.050 (3)	0.002 (2)	−0.001 (2)	0.008 (3)
C3	0.112 (3)	0.099 (3)	0.060 (2)	−0.020 (2)	0.040 (2)	0.0173 (18)

Geometric parameters (Å, º)

As1—O1^i	1.6510 (15)	C4—H4B	0.9700
As1—O1	1.6510 (15)	C5—C6	1.615 (6)
As1—O2	1.6982 (17)	C5—H5A	0.9700
As1—O2^i	1.6982 (17)	C5—H5B	0.9700
O2—H1	0.8534	C6—H6A	0.9600
As2—O4	1.6454 (15)	C6—H6B	0.9600
As2—O5	1.6797 (16)	C6—H6C	0.9600
As2—O3	1.6895 (17)	C6—H6D	0.9418
As2—O6	1.6985 (16)	C6—H6E	0.9195
O3—H2	0.8987	C6—H6F	0.9748
O5—H3	0.8780	C1—C3	1.565 (6)
O6—H4	0.9266	C1—H1A	0.9700
N1—C2^ii	1.475 (5)	C1—H1B	0.9700
N1—C2	1.475 (5)	C2—C3	1.615 (7)
N1—C1^ii	1.510 (5)	C2—H2A	0.9700
N1—C1	1.510 (5)	C2—H2B	0.9700
N1—C4	1.527 (4)	C3—H3A	0.9600
N1—C4^ii	1.527 (4)	C3—H3B	0.9600
N1—C5^ii	1.562 (5)	C3—H3C	0.9600
N1—C5	1.562 (5)	C3—H3D	0.9700
C4—C6	1.662 (6)	C3—H3E	0.9446
C4—H4A	0.9700	C3—H3F	0.9267
O1^i—As1—O1	113.94 (11)	H4B—C4—H6E	121.3
O1^i—As1—O2	111.87 (9)	N1—C5—C6	106.8 (3)
O1—As1—O2	105.40 (8)	N1—C5—H5A	110.4
O1^i—As1—O2^i	105.40 (8)	C6—C5—H5A	110.4
O1—As1—O2^i	111.87 (9)	N1—C5—H5B	110.4
O2—As1—O2^i	108.34 (14)	C6—C5—H5B	110.4
As1—O2—H1	108.2	H5A—C5—H5B	108.6
O4—As2—O5	109.81 (8)	N1—C5—H6C	123.3
O4—As2—O3	109.00 (9)	H5A—C5—H6C	121.2
O5—As2—O3	108.91 (10)	C5—C6—C4	70.9 (3)
O4—As2—O6	114.01 (8)	C5—C6—H6A	177.0
O5—As2—O6	106.43 (8)	C4—C6—H6A	108.8
O3—As2—O6	108.55 (8)	C4—C6—H6B	110.0
As2—O3—H2	114.2	H6A—C6—H6B	109.5
As2—O5—H3	106.9	C4—C6—H6C	109.6
As2—O6—H4	107.6	H6A—C6—H6C	109.5
C2^ii—N1—C2	180.0 (7)	H6B—C6—H6C	109.5
C2^ii—N1—C1^ii	70.5 (3)	C5—C6—H6D	106.7
C2—N1—C1^ii	109.5 (3)	C5—C6—H6E	107.9
C2^ii—N1—C1	109.5 (3)	H6D—C6—H6E	114.8
C2—N1—C1	70.5 (3)	C5—C6—H6F	105.6
C1^ii—N1—C1	180.0 (5)	H6D—C6—H6F	109.7
C2^ii—N1—C4	112.7 (3)	H6E—C6—H6F	111.7
C2—N1—C4	67.3 (3)	N1—C1—C3	112.4 (3)
C1^ii—N1—C4	69.6 (3)	N1—C1—H1A	109.1
C1—N1—C4	110.4 (3)	C3—C1—H1A	109.1
C2^ii—N1—C4^ii	67.3 (3)	N1—C1—H1B	109.1
C2—N1—C4^ii	112.7 (3)	C3—C1—H1B	109.1
C1^ii—N1—C4^ii	110.4 (3)	H1A—C1—H1B	107.9
C1—N1—C4^ii	69.6 (3)	N1—C1—H3E	126.7
C4—N1—C4^ii	180.0 (6)	H1B—C1—H3E	120.7
C2^ii—N1—C5^ii	111.2 (3)	N1—C2—C3	111.4 (4)
C2—N1—C5^ii	68.8 (3)	N1—C2—H2A	109.3
C1^ii—N1—C5^ii	71.3 (3)	C3—C2—H2A	109.3
C1—N1—C5^ii	108.7 (3)	N1—C2—H2B	109.3
C4—N1—C5^ii	104.1 (3)	C3—C2—H2B	109.3
C4^ii—N1—C5^ii	75.9 (3)	H2A—C2—H2B	108.0
C2^ii—N1—C5	68.8 (3)	N1—C2—H3C	128.2
C2—N1—C5	111.2 (3)	H2A—C2—H3C	118.4
C1^ii—N1—C5	108.7 (3)	C1—C3—H3A	109.5
C1—N1—C5	71.3 (3)	C1—C3—H3B	109.5
C4—N1—C5	75.9 (3)	H3A—C3—H3B	109.5
C4^ii—N1—C5	104.1 (3)	C1—C3—H3C	109.5
C5^ii—N1—C5	180.0 (5)	H3A—C3—H3C	109.5
N1—C4—C6	106.2 (3)	H3B—C3—H3C	109.5
N1—C4—H4A	110.5	C2—C3—H3D	106.2
C6—C4—H4A	110.5	C2—C3—H3E	106.0
N1—C4—H4B	110.5	H3D—C3—H3E	109.9
C6—C4—H4B	110.5	C2—C3—H3F	109.0
H4A—C4—H4B	108.7	H3D—C3—H3F	111.5
N1—C4—H6E	121.8	H3E—C3—H3F	113.8
C2^ii—N1—C4—C6	62.4 (4)	C2^ii—N1—C1—C3	−176.3 (4)
C2—N1—C4—C6	−117.6 (4)	C2—N1—C1—C3	3.7 (4)
C1^ii—N1—C4—C6	119.5 (4)	C4—N1—C1—C3	−51.6 (4)
C1—N1—C4—C6	−60.5 (4)	C4^ii—N1—C1—C3	128.4 (4)
C5^ii—N1—C4—C6	−177.0 (3)	C5^ii—N1—C1—C3	61.9 (4)
C5—N1—C4—C6	3.0 (3)	C5—N1—C1—C3	−118.1 (4)
C2^ii—N1—C5—C6	−124.8 (4)	C1^ii—N1—C2—C3	176.4 (3)
C2—N1—C5—C6	55.2 (4)	C1—N1—C2—C3	−3.6 (3)
C1^ii—N1—C5—C6	−65.5 (4)	C4—N1—C2—C3	119.7 (5)
C1—N1—C5—C6	114.5 (4)	C4^ii—N1—C2—C3	−60.3 (5)
C4—N1—C5—C6	−3.1 (3)	C5^ii—N1—C2—C3	−123.8 (4)
C4^ii—N1—C5—C6	176.9 (3)	C5—N1—C2—C3	56.2 (4)
N1—C5—C6—C4	3.0 (3)	N1—C1—C3—C2	−3.5 (3)
N1—C4—C6—C5	−3.0 (3)	N1—C2—C3—C1	3.6 (3)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H1···O4^iii	0.85	1.79	2.642 (2)	175
O3—H2···O1	0.90	1.65	2.547 (2)	176
O5—H3···O1^iv	0.88	1.70	2.564 (2)	168
O6—H4···O4^v	0.93	1.71	2.617 (2)	164

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

(II) 1,4-diazoniabicyclo[2.2.2]octane bis(dihydrogenarsenate) arsenic acid

Crystal data

(C6H14N2)[H2AsO4]2[H3AsO4]	F(000) = 1064
Mr = 538.01	Dx = 2.076 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 5683 reflections
a = 8.1285 (3) Å	θ = 2.8–32.1°
b = 22.2104 (9) Å	µ = 5.85 mm^−1
c = 10.0056 (4) Å	T = 293 K
β = 107.637 (1)°	Block, colourless
V = 1721.47 (12) Å^3	0.24 × 0.20 × 0.14 mm
Z = 4

Data collection

Bruker SMART 1000 CCD diffractometer	6212 independent reflections
Radiation source: fine-focus sealed tube	4321 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.032
ω scans	θmax = 32.6°, θmin = 1.8°
Absorption correction: multi-scan (SADABS; Bruker, 1999)	h = −12→11
Tmin = 0.297, Tmax = 0.441	k = −33→30
17889 measured reflections	l = −8→15

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.028	H-atom parameters constrained
wR(F^2) = 0.056	w = 1/[σ^2(Fo^2) + (0.0233P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 0.89	(Δ/σ)max = 0.002
6212 reflections	Δρmax = 0.64 e Å^−3
209 parameters	Δρmin = −0.45 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.00252 (11)

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq
As1	−0.20979 (3)	0.134143 (10)	0.23649 (3)	0.02638 (6)
O1	−0.4053 (2)	0.11193 (7)	0.12768 (18)	0.0397 (4)
H1	−0.4289	0.0815	0.1760	0.048*
O2	−0.0777 (2)	0.07695 (7)	0.29270 (19)	0.0400 (4)
O3	−0.2434 (2)	0.16451 (8)	0.38238 (18)	0.0507 (5)
H3	−0.3371	0.1821	0.3723	0.061*
O4	−0.1462 (2)	0.18726 (8)	0.1465 (2)	0.0467 (5)
As2	0.34076 (3)	0.024094 (10)	0.30675 (3)	0.02488 (6)
O5	0.1507 (2)	0.04422 (8)	0.19015 (18)	0.0395 (4)
H5	0.0865	0.0660	0.2326	0.047*
O6	0.48508 (19)	0.01777 (7)	0.22083 (18)	0.0316 (4)
O7	0.4021 (2)	0.07085 (7)	0.44236 (17)	0.0342 (4)
O8	0.2994 (2)	−0.04542 (7)	0.36429 (18)	0.0388 (4)
H8	0.3932	−0.0570	0.4345	0.047*
As3	0.29256 (3)	0.228100 (10)	0.33337 (3)	0.02591 (6)
O9	0.2756 (2)	0.17439 (7)	0.44770 (19)	0.0430 (4)
H9	0.3353	0.1396	0.4435	0.052*
O10	0.2095 (2)	0.29091 (7)	0.38400 (19)	0.0413 (4)
H10	0.2532	0.3018	0.4810	0.050*
O11	0.48942 (19)	0.23803 (7)	0.3267 (2)	0.0380 (4)
O12	0.1643 (2)	0.21237 (9)	0.17108 (18)	0.0463 (5)
H12	0.0587	0.2004	0.1686	0.056*
N1	0.6253 (2)	0.34281 (8)	0.3066 (2)	0.0303 (4)
H13	0.5696	0.3092	0.3221	0.036*
N2	0.7753 (2)	0.43453 (8)	0.2628 (2)	0.0267 (4)
H14	0.8311	0.4680	0.2471	0.032*
C1	0.8104 (3)	0.32797 (10)	0.3286 (3)	0.0403 (6)
H1A	0.8196	0.2933	0.2724	0.048*
H1B	0.8664	0.3184	0.4265	0.048*
C2	0.5431 (3)	0.36381 (12)	0.1600 (3)	0.0409 (6)
H2A	0.4197	0.3682	0.1425	0.049*
H2B	0.5622	0.3345	0.0944	0.049*
C3	0.6106 (4)	0.39077 (11)	0.4064 (3)	0.0437 (6)
H3A	0.6508	0.3757	0.5018	0.052*
H3B	0.4909	0.4028	0.3867	0.052*
C4	0.8970 (3)	0.38193 (9)	0.2861 (3)	0.0310 (5)
H4A	1.0030	0.3914	0.3592	0.037*
H4B	0.9253	0.3731	0.2007	0.037*
C5	0.6213 (3)	0.42404 (10)	0.1393 (2)	0.0333 (5)
H5A	0.6547	0.4233	0.0540	0.040*
H5B	0.5378	0.4561	0.1314	0.040*
C6	0.7194 (3)	0.44446 (9)	0.3905 (2)	0.0303 (5)
H6A	0.6522	0.4812	0.3805	0.036*
H6B	0.8195	0.4482	0.4727	0.036*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
As1	0.02053 (10)	0.02777 (11)	0.02869 (13)	0.00083 (8)	0.00423 (9)	0.00449 (10)
O1	0.0317 (9)	0.0438 (10)	0.0340 (10)	−0.0131 (7)	−0.0043 (8)	0.0091 (8)
O2	0.0351 (9)	0.0374 (9)	0.0506 (11)	0.0144 (7)	0.0178 (9)	0.0128 (8)
O3	0.0464 (11)	0.0636 (12)	0.0360 (11)	0.0239 (9)	0.0035 (9)	−0.0082 (9)
O4	0.0326 (9)	0.0498 (11)	0.0501 (11)	−0.0135 (8)	0.0012 (9)	0.0216 (9)
As2	0.02144 (10)	0.02655 (11)	0.02791 (13)	0.00271 (8)	0.00935 (9)	0.00314 (9)
O5	0.0296 (8)	0.0548 (11)	0.0324 (9)	0.0157 (8)	0.0068 (8)	0.0059 (8)
O6	0.0293 (8)	0.0318 (8)	0.0406 (10)	0.0035 (6)	0.0209 (8)	0.0024 (7)
O7	0.0367 (9)	0.0318 (8)	0.0316 (9)	0.0071 (7)	0.0066 (8)	−0.0032 (7)
O8	0.0325 (9)	0.0366 (9)	0.0437 (11)	−0.0069 (7)	0.0063 (8)	0.0102 (8)
As3	0.02443 (11)	0.02288 (10)	0.03107 (13)	−0.00267 (8)	0.00938 (10)	−0.00219 (9)
O9	0.0618 (12)	0.0296 (9)	0.0486 (11)	0.0054 (8)	0.0335 (10)	0.0056 (8)
O10	0.0443 (10)	0.0323 (9)	0.0428 (11)	0.0145 (7)	0.0062 (9)	−0.0052 (8)
O11	0.0243 (8)	0.0277 (8)	0.0639 (12)	−0.0024 (6)	0.0162 (8)	0.0016 (8)
O12	0.0356 (9)	0.0699 (13)	0.0317 (10)	−0.0152 (9)	0.0075 (8)	−0.0126 (9)
N1	0.0265 (9)	0.0253 (9)	0.0400 (12)	−0.0061 (7)	0.0113 (9)	0.0006 (9)
N2	0.0282 (9)	0.0260 (9)	0.0279 (10)	−0.0034 (7)	0.0116 (8)	0.0037 (8)
C1	0.0253 (11)	0.0292 (12)	0.0638 (19)	0.0033 (9)	0.0093 (12)	0.0074 (12)
C2	0.0294 (12)	0.0481 (15)	0.0370 (15)	−0.0045 (11)	−0.0024 (11)	−0.0062 (12)
C3	0.0641 (17)	0.0386 (13)	0.0392 (16)	−0.0110 (13)	0.0319 (14)	−0.0090 (12)
C4	0.0212 (10)	0.0326 (12)	0.0386 (14)	0.0020 (9)	0.0083 (10)	0.0024 (10)
C5	0.0320 (12)	0.0419 (13)	0.0237 (12)	0.0076 (10)	0.0053 (10)	0.0035 (10)
C6	0.0357 (12)	0.0279 (11)	0.0276 (12)	−0.0005 (9)	0.0100 (10)	−0.0050 (9)

Geometric parameters (Å, º)

As1—O2	1.6483 (15)	N1—C2	1.491 (3)
As1—O4	1.6585 (16)	N1—H13	0.9100
As1—O3	1.7037 (17)	N2—C5	1.486 (3)
As1—O1	1.7045 (15)	N2—C6	1.497 (3)
O1—H1	0.8857	N2—C4	1.502 (3)
O3—H3	0.8348	N2—H14	0.9100
As2—O6	1.6571 (14)	C1—C4	1.515 (3)
As2—O7	1.6608 (16)	C1—H1A	0.9700
As2—O5	1.6896 (16)	C1—H1B	0.9700
As2—O8	1.7163 (15)	C2—C5	1.522 (3)
O5—H5	0.9060	C2—H2A	0.9700
O8—H8	0.9032	C2—H2B	0.9700
As3—O11	1.6365 (14)	C3—C6	1.522 (3)
As3—O12	1.6793 (17)	C3—H3A	0.9700
As3—O9	1.6871 (16)	C3—H3B	0.9700
As3—O10	1.6928 (15)	C4—H4A	0.9700
O9—H9	0.9205	C4—H4B	0.9700
O10—H10	0.9578	C5—H5A	0.9700
O12—H12	0.8918	C5—H5B	0.9700
N1—C3	1.490 (3)	C6—H6A	0.9700
N1—C1	1.490 (3)	C6—H6B	0.9700
O2—As1—O4	117.10 (8)	N1—C1—C4	108.53 (17)
O2—As1—O3	105.65 (9)	N1—C1—H1A	110.0
O4—As1—O3	109.92 (10)	C4—C1—H1A	110.0
O2—As1—O1	112.31 (9)	N1—C1—H1B	110.0
O4—As1—O1	104.05 (8)	C4—C1—H1B	110.0
O3—As1—O1	107.54 (9)	H1A—C1—H1B	108.4
As1—O1—H1	100.8	N1—C2—C5	109.15 (19)
As1—O3—H3	117.4	N1—C2—H2A	109.9
O6—As2—O7	113.11 (8)	C5—C2—H2A	109.9
O6—As2—O5	107.88 (8)	N1—C2—H2B	109.9
O7—As2—O5	112.58 (8)	C5—C2—H2B	109.9
O6—As2—O8	109.83 (8)	H2A—C2—H2B	108.3
O7—As2—O8	109.22 (8)	N1—C3—C6	108.83 (18)
O5—As2—O8	103.80 (8)	N1—C3—H3A	109.9
As2—O5—H5	110.7	C6—C3—H3A	109.9
As2—O8—H8	108.1	N1—C3—H3B	109.9
O11—As3—O12	108.48 (9)	C6—C3—H3B	109.9
O11—As3—O9	113.86 (9)	H3A—C3—H3B	108.3
O12—As3—O9	110.75 (9)	N2—C4—C1	108.58 (16)
O11—As3—O10	112.62 (8)	N2—C4—H4A	110.0
O12—As3—O10	105.89 (9)	C1—C4—H4A	110.0
O9—As3—O10	104.95 (8)	N2—C4—H4B	110.0
As3—O9—H9	114.2	C1—C4—H4B	110.0
As3—O10—H10	116.8	H4A—C4—H4B	108.4
As3—O12—H12	113.5	N2—C5—C2	107.78 (18)
C3—N1—C1	110.0 (2)	N2—C5—H5A	110.1
C3—N1—C2	109.45 (19)	C2—C5—H5A	110.1
C1—N1—C2	110.3 (2)	N2—C5—H5B	110.1
C3—N1—H13	109.0	C2—C5—H5B	110.1
C1—N1—H13	109.0	H5A—C5—H5B	108.5
C2—N1—H13	109.0	N2—C6—C3	108.09 (18)
C5—N2—C6	109.63 (17)	N2—C6—H6A	110.1
C5—N2—C4	110.86 (17)	C3—C6—H6A	110.1
C6—N2—C4	109.76 (18)	N2—C6—H6B	110.1
C5—N2—H14	108.9	C3—C6—H6B	110.1
C6—N2—H14	108.9	H6A—C6—H6B	108.4
C4—N2—H14	108.9

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···O6^i	0.89	1.70	2.557 (2)	163
O3—H3···O11^i	0.83	1.83	2.638 (2)	163
O5—H5···O2	0.91	1.64	2.487 (2)	154
O8—H8···O7^ii	0.90	1.77	2.666 (2)	170
O9—H9···O7	0.92	1.62	2.526 (2)	167
O10—H10···O4^iii	0.96	1.63	2.578 (3)	171
O12—H12···O4	0.89	1.64	2.523 (2)	171
N1—H13···O11	0.91	1.72	2.610 (2)	167
N2—H14···O6^iv	0.91	1.81	2.655 (2)	154

Symmetry codes: (i) x−1, y, z; (ii) −x+1, −y, −z+1; (iii) x+1/2, −y+1/2, z+1/2; (iv) −x+3/2, y+1/2, −z+1/2.