A 1:1 adduct of dl-threonine and arsenic acid

Wilkinson, H.S.; Harrison, W.T.A.

doi:10.1107/S0108270105012291

metal-organic compounds

STRUCTURAL
CHEMISTRY

ISSN: 2053-2296

Volume 61| Part 6| June 2005| Pages m253-m255

doi:10.1107/S0108270105012291

A 1:1 adduct of DL-threonine and arsenic acid

Hazel S. Wilkinson ^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 15 April 2005; accepted 19 April 2005; online 13 May 2005)

The title compound, DL-threonine–arsenic acid (1/1), C₄H₉NO₃·H₃AsO₄, is an unusual adduct containing zwitterionic threonine and neutral arsenic acid molecules. The component species interact by way of N—H⋯O and O—H⋯O hydrogen bonds, leading to parallel [001] chains of threonine and arsenic acid molecules which are crosslinked by further O—H⋯O and N—H⋯O bonds, resulting in a three-dimensional network.

Comment

Only a handful of crystal structures conaining the neutral arsenic acid (H₃AsO₄) moiety have been determined, including N,N,N-trimethylglycine (beatine) arsenic acid (Schildkamp et al., 1984 ), tetraphenylphosphonium chloride arsenic acid (Ruhlandt-Senge et al., 1992 ) and L-histininium dihydrogen arsenate arsenic acid (Ratajczak et al., 2000 ). We present here the synthesis and structure of the title compound, C₄H₉NO₃·H₃AsO₄, (I) (Fig. 1), an unusual 1:1 adduct of neutral DL-threonine (threo-α-amino-β-hydroxy-n-butyric acid) and arsenic acid moieties.

The H₃AsO₄ arsenic acid molecule in (I) shows its normal tetrahedral geometry about As [mean As—O = 1.680 (2) Å], with the unprotonated formal As1=O4 double bond showing its expected (Lee & Harrison, 2003a ) shortening relative to the three As—OH vertices (Table 1).

Each threonine molecule is chiral (the arbitrarily chosen asymmetric unit molecule has an S conformation at C2 and an R conformation at C3), but space-group symmetry generates a 50:50 mix of enantiomers, which is consistent with the racemic starting material. The DL-threonine entity is zwitterionic (i.e. nominal H-atom transfer from O1 or O2 to N1) and the C1—O1 and C1—O2 bond lengths of the delocalized carboxyl group are almost identical (Table 1). It is perhaps surprising that the threonine is not protonated (overall positive charge) under the low pH reaction conditions.

For ease of comparison with other structures, we refer to atoms C2, C3 and C4 as Cα, Cβ and Cγ, respectively, and atom O3 as Oγ. In (I), with respect to N1 and the Cα—Cβ bond, both Cγ and Oγ are gauche [torsion angles = −61.4 (3) and 61.5 (3)°, respectively], as are the two H atoms attached to Cα and Cβ (H—Cα—Cβ—H = −62.4°). A similar so-called gauche-I/gauche-II molecular conformation was seen in DL-threoninium hydrogen phosphate (Ravikumar et al., 2002 ), with equivalent torsion angles of N1—Cα—Cβ—Cγ = −64.1 (3)°, N1—Cα—Cβ—Oγ = 59.5 (2)° and H—Cα—Cβ—H = −64.4°. By way of contrast, L-threonine (Janczak et al., 1997 ) has a quite different trans(Cγ)/gauche(Oγ) conformation about the Cα—Cβ bond, with equivalent angles of N1—Cα—Cβ—Cγ = −174.82 (9)°, N1—Cα—Cβ—Oγ = −54.6 (1)° and H—Cα—Cβ—H = −179.3°. The `backbone' O2—C1—Cα—N1 (ψ¹) torsion angle in (I) is −12.3 (3)°, which compares well with the value of −7.8 (3)° seen in DL-threoninium hydrogen phosphate (Ravikumar et al., 2002). In L-threonine itself, the carboxyl group is somewhat more twisted about the Cα—C1 bond, yielding (using our atom-numbering scheme) a O2—C1—Cα—N1 torsion angle of −25.3 (2)°. The gauche/gauche threonine geometry in (I) could be reinforced by the intramolecular N1—H1B⋯O3 and N1—H1C⋯O2 hydrogen bonds (Fig. 1 and Table 2).

As well as van der Waals forces, the component species in (I) interact by means of a network of N—H⋯O and O—H⋯O hydrogen bonds (Table 2). It is notable that atom H1B is involved in a bifurcated N—H⋯(O,O) hydrogen bond (angle sum about H1B = 360°) and atom H1C makes a trifurcated N—H⋯(O,O,O) link (average angle about H1C = 108°). The H₃AsO₄ units are linked into polymeric chains of single tetrahedra propagating along [001] (Fig. 2) by way of the O5—H5⋯O4^vi bond (see Table 2 for symmetry code). Adjacent tetrahedra in the chain are thus related by c-glide symmetry. The As⋯As^vi separation is 4.5516 (5) Å. The other two As—OH vertices (atoms O6 and O7) act as hydrogen-bond donors to carboxyl acceptor O atoms on nearby threonine molecules. The organic species of (I) also forms c-glide symmetry-generated chains, via N1—H1B⋯O1ⁱⁱ (Fig. 3). Adjacent threonine molecules in the [001] chain therefore have opposite chiralities. Finally, the other N—H moieties (N1—H1B and N1—H1C) and the O3—H3 hydroxyl group make hydrogen bonds to nearby arsenic acid molecules (Table 2), complementing the arsenic acid-to-threonine hydrogen bonds involving atoms H6 and H7 (Fig. 4). All of the O atoms in the structure accept at least one hydrogen bond.

The structure of (I) is quite distinct from those of salt-like ammonium hydrogenarsenates (Lee & Harrison, 2003a,b ,c ), where H-atom transfer from arsenic acid to amine occurs.

Figure 1
The asymmetric unit of (I)

, showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii. Hydrogen bonds are indicated by dashed lines.

Figure 2
Detail of a hydrogen-bonded arsenic acid chain in (I)

. [Symmetry codes are as in Table 2

, with the addition of (vii) x, $[{1\over 2}]$ − y, z + $[{1\over 2}]$ ; (viii) x, y, 1 + z.]

Figure 3
Detail of a hydrogen-bonded DL-threonine chain in (I)

. Methyl H atoms have been omitted for clarity. [Symmetry codes are as in Table 2

, with the addition of (ix) x, $[{3\over 2}]$ − y, z − $[{1\over 2}]$ ; (x) x, y, z − 1.]

Figure 4
The unit-cell packing in (I)

projected down [001], showing the cross-linked stacks of DL-threonine and arsenic acid moieties.

Experimental

Aqueous DL-threonine solution (0.5 M, 10 ml) was added to an aqueous H₃AsO₄ solution (0.5 M, 10 ml), giving a clear solution. A mass of needles of (I) grew as the water evaporated from the increasingly viscous liquor over the course of a few days.

Crystal data

C₄H₉NO₃·H₃AsO₄
M_r = 261.07
Monoclinic, P 2₁ /c
a = 10.1195 (6) Å
b = 9.8062 (6) Å
c = 8.9643 (6) Å
β = 99.098 (1)°
V = 878.37 (10) Å³
Z = 4
D_x = 1.974 Mg m⁻³
Mo Kα radiation
Cell parameters from 2540 reflections
θ = 2.9–32.2°
μ = 3.88 mm⁻¹
T = 293 (2) K
Needle, colourless
0.45 × 0.03 × 0.01 mm

Data collection

Bruker SMART 1000 CCD area-detector diffractometer
ω scans
Absorption correction: multi-scan(SADABS; Bruker, 1999 )T_min = 0.274, T_max = 0.962
7588 measured reflections
3122 independent reflections
2165 reflections with I > 2σ(I)
R_int = 0.049
θ_max = 32.5°
h = −14 → 15
k = −14 → 14
l = −9 → 13

Refinement

Refinement on F²
R[F² > 2σ(F²)] = 0.037
wR(F²) = 0.087
S = 0.94
3122 reflections
120 parameters
H-atom parameters constrained
w = 1/[σ²(F_o²) + (0.0417P)²] where P = (F_o² + 2F_c²)/3
(Δ/σ)_max < 0.001
Δρ_max = 0.80 e Å⁻³
Δρ_min = −0.74 e Å⁻³

Table 1
Selected geometric parameters (Å, °)

C1—O2	1.263 (3)
C1—O1	1.264 (3)
As1—O4	1.639 (2)
As1—O6	1.6769 (19)
As1—O7	1.699 (2)
As1—O5	1.704 (2)

O2—C1—C2—N1	−12.3 (3)
O1—C1—C2—N1	165.4 (2)
O2—C1—C2—C3	109.0 (3)
O1—C1—C2—C3	−73.2 (3)
N1—C2—C3—O3	61.5 (3)
C1—C2—C3—O3	−59.3 (3)
N1—C2—C3—C4	−61.4 (3)
C1—C2—C3—C4	177.7 (2)
H2—C2—C3—H3A	−62.4

Table 2
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1A⋯O4ⁱ	0.89	1.92	2.800 (3)	170
N1—H1B⋯O1ⁱⁱ	0.89	2.15	2.903 (3)	143
N1—H1B⋯O3	0.89	2.38	2.810 (3)	110
N1—H1C⋯O7ⁱⁱⁱ	0.89	2.30	3.069 (3)	145
N1—H1C⋯O2	0.89	2.33	2.646 (3)	101
N1—H1C⋯O6^iv	0.89	2.35	2.890 (3)	119
O3—H3⋯O5^v	0.82	2.14	2.906 (3)	156
O5—H5⋯O4^vi	0.79	1.79	2.580 (3)	179
O6—H6⋯O2^vi	0.77	1.76	2.514 (3)	169
O7—H7⋯O1	0.84	1.73	2.569 (3)	179
Symmetry codes: (i) x, y+1, z; (ii) $[x, -y+{\script{3\over 2}}, z+{\script{1\over 2}}]$ ; (iii) $[-x, y+{\script{1\over 2}}, -z+{\script{3\over 2}}]$ ; (iv) -x, -y+1, -z+1; (v) $[-x+1, y+{\script{1\over 2}}, -z+{\script{3\over 2}}]$ ; (vi) $[x, -y+{\script{1\over 2}}, z-{\script{1\over 2}}]$ .

The hydroxy H atoms were found in difference maps and refined as riding on their parent O atoms in their as-found relative positions. H atoms bonded to C and N atoms were placed in idealized positions, with C—H = 0.96–0.98 Å and N—H = 0.89 Å, and refined as riding, with the rigid NH₃ or CH₃ groups allowed to rotate freely about the bond joining the atoms in question to C1. The constraint U_iso(H) = 1.2U_eq(carrier) or 1.5U_eq(methyl carrier) was applied as appropriate.

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 ); software used to prepare material for publication: SHELXL97.

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S0108270105012291/fg1837sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S0108270105012291/fg1837Isup2.hkl

Comment top

Only a handful of crystal structures conaining the neutral arsenic acid (H₃AsO₄) moiety have been determined, including N,N,N-trimethyl glycine (beatine) arsenic acid (Schildkamp et al., 1984), tetraphenylphosphonium chloride arsenic acid (Ruhlandt-Senge et al., 1992) and L-histininium dihydrogen arsenate arsenic acid (Ratajczak et al., 2000). Here, we present the synthesis and structure of the title compound, C₄H₉NO₃·H₃AsO₄, (I) (Fig. 1), an unusual 1:1 adduct of neutral DL-threonine (threo-α-amino-β-hydroxy-n-butyric acid) and arsenic acid moieties.

The H₃AsO₄ arsenic acid molecule in (I) shows its normal tetrahedral geometry about As [mean As—O 1.680 (2) Å], with the unprotonated formal double As1═O4 bond showing its expected (Lee & Harrison, 2003a) shortening relative to the three As—OH vertices (Table 1).

Each threonine molecule is chiral (the arbitrarily chosen asymmetric unit molecule has an S conformation at C2 and an R conformation at C3) but space-group symmetry generates a 50:50 mix of enantiomers, which is consistent with the racemic starting material. The C₄H₉NO₃ entitly is zwitterionic (i.e. nominal H-atom transfer from O1 or O2 to N1) and the C1—O1 and C1—O2 bond lengths of the delocalized carboxyl group are almost identical (Table 1). It is perhaps surprising that the threonine is not protonated (overall positive charge) under the low-pH reaction conditions.

For ease of comparison with other structures, we refer to atoms C2, C3 and C4 as Cα, Cβ and Cγ, respectively, and atom O3 as Oγ. In (I), with respect to N1 and the Cα—Cβ bond, both Cγ and Oγ are gauche [torsion angles −61.4 (3) and 61.5 (3)°, respectively], as are the two H atoms attached to Cα and Cβ (H—Cα—Cβ—H = −62.4°). A similar so-called gauche-I/gauche-II molecular conformation is seen in DL-threoninium hydrogen phosphate (Ravikumar et al., 2002), with equivalent torsion angles of N1—Cα—Cβ—Cg = −64.1 (3)°, N1—Cα—Cβ—Oγ = 59.5 (2)° and H—Cα—Cβ—H = −64.4°. By way of contrast, L-threonine (Janczak et al., 1997) has a quite different trans(Cγ)/gauche(Oγ) conformation about the Cα—Cβ bond, with equivalent angles of N1—Cα—Cβ—Cg = −174.82 (9)°, N1—Cα—Cβ—Oγ = −54.6 (1)° and H—Cα—Cβ—H = −179.3°. The `backbone' O2—C1—Cα—N1 ψ¹ torsion angle in (I) is −12.3 (3)°, which compares well with the value of −7.8 (3)° seen in DL-threoninium hydrogen phosphate (Ravikumar et al., 2002). In L-threonine itself, the carboxyl group is somewhat more twisted about the Cα—C1 bond, yielding (using our atom-numbering scheme) O2—C1—Cα—N1 = −25.3 (2)°. The gauche/gauche threonine geometry in (I) could be reinforced by the intramolecular N1—H1B···O3 and N1—H1C···O2 hydrogen bonds (Fig.1 and Table 2).

As well as van der Waals' forces, the component species in (I) interact by means of a network of N—H···O and O—H···O hydrogen bonds (Table 2). It is notable that atom H1B is involved in a bifurcated N—H···(O,O) hydrogen bond (angle sum about H1B = 360°) and atom H1C makes a trifurcated N—H···(O,O,O) link (average angle about H1C = 108°). The H₃AsO₄ units are linked into polymeric chains of single tetrahedra propagating along [001] (Fig. 2) by way of the O5—H5···O4^vi bond (see Table 2 for symmetry code). Adjacent tetrahedra in the chain are thus related by c-glide symmetry. The As···As^vi separation is 4.5516 (5) Å. The other two As—OH vertices (atoms O6 and O7) act as hydrogen-bond donors to carboxyl acceptor O atoms on nearby threonine molecules. The organic species of (I) also forms c-glide symmetry-generated chains, via N1—H1B···O1ⁱⁱ (Fig. 3). Adjacent threonine molecules in the [001] chain therefore have opposite chiralities. Finally, the other N—H moieties (N1—H1B and N1—H1C) and the O3—H3 hydroxyl group make hydrogen bonds to nearby arsenic acid molecules (Table 2), to complement the arsenic acid-to-threonine hydrogen bonds involving atoms H6 and H7 (Fig. 4). All of the O atoms in the structure accept at least one hydrogen bond.

The structure of (I) is quite distinct from those of salt-like ammonium hydrogenarsenates (Lee & Harrison, 2003a,b,c), where H-atom transfer from arsenic acid to amine occurs.

Experimental top

Aqueous DL-threonine solution (0.5 M, 10 ml) was added to an H₃AsO₄ solution (0.5 M, 10 ml), giving a clear solution. A mass of needles of (I) grew as the water evaporated from the increasingly viscous liquor over the course of a few days.

Computing details top

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); software used to prepare material for publication: SHELXL97.

Figures top

	Fig. 1. The asymmetric unit of (I), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii. Hydrogen bonds are indicated by dashed lines.
	Fig. 2. Detail of a hydrogen-bonded arsenic acid chain in (I). [Symmetry codes as in Table 2; additionally: (vii) x, 1/2 − y, z + 1/2; (viii) x, y, 1 + z.]
	Fig. 3. Detail of a hydrogen-bonded DL-threonine chain in (I). Methyl H atoms have been omitted for clarity. [Symmetry codes as in Table 2; additionally: (ix) x, 3/2 − y, z − 1/2; (x) x, y, z − 1.]
	Fig. 4. The unit-cell packing in (I) projected down [001], showing the cross-linked stacks of DL-threonine and arsenic acid moieties.

DL-threonine–arsenic acid (1/1) top

Crystal data top

C₄H₉NO₃·H₃AsO₄	F(000) = 528
M_r = 261.07	D_x = 1.974 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 2540 reflections
a = 10.1195 (6) Å	θ = 2.9–32.2°
b = 9.8062 (6) Å	µ = 3.88 mm⁻¹
c = 8.9643 (6) Å	T = 293 K
β = 99.098 (1)°	Needle, colourless
V = 878.37 (10) Å³	0.45 × 0.03 × 0.01 mm
Z = 4

Data collection top

Bruker SMART 1000 CCD area-detector diffractometer	3122 independent reflections
Radiation source: fine-focus sealed tube	2165 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.049
ω scans	θ_max = 32.5°, θ_min = 2.9°
Absorption correction: multi-scan (SADABS; Bruker, 1999)	h = −14→15
T_min = 0.274, T_max = 0.962	k = −14→14
7588 measured reflections	l = −9→13

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.037	Hydrogen site location: difmap (O-H) and geom (C-H, N-H)
wR(F²) = 0.087	H-atom parameters constrained
S = 0.94	w = 1/[σ²(F_o²) + (0.0417P)²] where P = (F_o² + 2F_c²)/3
3122 reflections	(Δ/σ)_max < 0.001
120 parameters	Δρ_max = 0.80 e Å⁻³
0 restraints	Δρ_min = −0.74 e Å⁻³

Crystal data top

C₄H₉NO₃·H₃AsO₄	V = 878.37 (10) Å³
M_r = 261.07	Z = 4
Monoclinic, P2₁/c	Mo Kα radiation
a = 10.1195 (6) Å	µ = 3.88 mm⁻¹
b = 9.8062 (6) Å	T = 293 K
c = 8.9643 (6) Å	0.45 × 0.03 × 0.01 mm
β = 99.098 (1)°

Data collection top

Bruker SMART 1000 CCD area-detector diffractometer	3122 independent reflections
Absorption correction: multi-scan (SADABS; Bruker, 1999)	2165 reflections with I > 2σ(I)
T_min = 0.274, T_max = 0.962	R_int = 0.049
7588 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.037	0 restraints
wR(F²) = 0.087	H-atom parameters constrained
S = 0.94	Δρ_max = 0.80 e Å⁻³
3122 reflections	Δρ_min = −0.74 e Å⁻³
120 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
C1	0.1951 (3)	0.6430 (3)	0.7378 (3)	0.0194 (5)
C2	0.2502 (3)	0.7846 (3)	0.7235 (3)	0.0202 (5)
H2	0.2299	0.8138	0.6178	0.024*
C3	0.4023 (3)	0.7827 (3)	0.7723 (3)	0.0253 (5)
H3A	0.4409	0.7158	0.7103	0.030*
C4	0.4678 (3)	0.9195 (4)	0.7561 (4)	0.0404 (8)
H4A	0.5632	0.9084	0.7704	0.061*
H4B	0.4444	0.9814	0.8307	0.061*
H4C	0.4374	0.9556	0.6571	0.061*
N1	0.1864 (2)	0.8810 (2)	0.8190 (3)	0.0246 (5)
H1A	0.1879	0.9649	0.7813	0.037*
H1B	0.2312	0.8799	0.9128	0.037*
H1C	0.1020	0.8559	0.8199	0.037*
O1	0.2186 (2)	0.5576 (2)	0.6395 (2)	0.0280 (4)
O2	0.1269 (2)	0.6198 (2)	0.8414 (3)	0.0315 (5)
O3	0.4228 (2)	0.7367 (3)	0.9236 (3)	0.0386 (6)
H3	0.4995	0.7157	0.9589	0.046*
As1	0.15993 (3)	0.20962 (3)	0.52512 (3)	0.01895 (8)
O4	0.2169 (2)	0.1352 (2)	0.6862 (2)	0.0274 (4)
O5	0.2961 (2)	0.2523 (2)	0.4450 (2)	0.0305 (5)
H5	0.2726	0.2877	0.3667	0.037*
O6	0.0552 (2)	0.1168 (2)	0.4012 (2)	0.0266 (4)
H6	0.0853	0.0493	0.3787	0.032*
O7	0.0704 (2)	0.35389 (19)	0.5414 (3)	0.0286 (5)
H7	0.1187	0.4197	0.5745	0.034*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C1	0.0229 (13)	0.0142 (11)	0.0202 (12)	0.0040 (10)	0.0009 (10)	0.0029 (9)
C2	0.0220 (12)	0.0173 (11)	0.0209 (11)	−0.0011 (11)	0.0023 (9)	0.0001 (11)
C3	0.0221 (13)	0.0250 (13)	0.0287 (13)	−0.0024 (12)	0.0036 (10)	−0.0028 (12)
C4	0.0246 (17)	0.0317 (16)	0.064 (2)	−0.0073 (14)	0.0039 (16)	0.0012 (16)
N1	0.0235 (12)	0.0214 (11)	0.0286 (12)	−0.0002 (10)	0.0028 (9)	0.0018 (10)
O1	0.0302 (11)	0.0207 (9)	0.0330 (11)	−0.0036 (9)	0.0043 (9)	−0.0066 (9)
O2	0.0401 (13)	0.0206 (9)	0.0364 (12)	−0.0053 (9)	0.0142 (10)	0.0026 (9)
O3	0.0244 (11)	0.0606 (15)	0.0287 (11)	0.0050 (11)	−0.0023 (9)	0.0101 (11)
As1	0.01933 (13)	0.01707 (12)	0.01934 (12)	0.00126 (12)	−0.00037 (8)	0.00114 (12)
O4	0.0362 (12)	0.0231 (10)	0.0206 (9)	0.0023 (9)	−0.0029 (8)	0.0041 (8)
O5	0.0210 (10)	0.0467 (12)	0.0229 (10)	−0.0013 (9)	0.0003 (8)	0.0072 (9)
O6	0.0275 (11)	0.0215 (9)	0.0275 (10)	0.0002 (8)	−0.0056 (8)	−0.0069 (8)
O7	0.0246 (11)	0.0163 (9)	0.0443 (13)	0.0015 (8)	0.0038 (9)	−0.0025 (9)

Geometric parameters (Å, º) top

C1—O2	1.263 (3)	N1—H1A	0.89
C1—O1	1.264 (3)	N1—H1B	0.89
C1—C2	1.509 (4)	N1—H1C	0.89
C2—N1	1.489 (3)	O3—H3	0.82
C2—C3	1.532 (4)	As1—O4	1.639 (2)
C2—H2	0.98	As1—O6	1.6769 (19)
C3—O3	1.414 (4)	As1—O7	1.699 (2)
C3—C4	1.514 (4)	As1—O5	1.704 (2)
C3—H3A	0.98	O5—H5	0.79
C4—H4A	0.96	O6—H6	0.77
C4—H4B	0.96	O7—H7	0.84
C4—H4C	0.96

O2—C1—O1	125.3 (3)	H4A—C4—H4C	109.5
O2—C1—C2	118.7 (2)	H4B—C4—H4C	109.5
O1—C1—C2	116.0 (2)	C2—N1—H1A	109.5
N1—C2—C1	109.7 (2)	C2—N1—H1B	109.5
N1—C2—C3	110.5 (2)	H1A—N1—H1B	109.5
C1—C2—C3	109.4 (2)	C2—N1—H1C	109.5
N1—C2—H2	109.1	H1A—N1—H1C	109.5
C1—C2—H2	109.1	H1B—N1—H1C	109.5
C3—C2—H2	109.1	C3—O3—H3	116.0
O3—C3—C4	112.0 (3)	O4—As1—O6	116.04 (10)
O3—C3—C2	105.4 (2)	O4—As1—O7	114.42 (11)
C4—C3—C2	113.4 (3)	O6—As1—O7	102.63 (10)
O3—C3—H3A	108.6	O4—As1—O5	106.60 (11)
C4—C3—H3A	108.6	O6—As1—O5	108.81 (11)
C2—C3—H3A	108.6	O7—As1—O5	108.05 (11)
C3—C4—H4A	109.5	As1—O5—H5	109.5
C3—C4—H4B	109.5	As1—O6—H6	114.0
H4A—C4—H4B	109.5	As1—O7—H7	112.5
C3—C4—H4C	109.5

O2—C1—C2—N1	−12.3 (3)	C1—C2—C3—O3	−59.3 (3)
O1—C1—C2—N1	165.4 (2)	N1—C2—C3—C4	−61.4 (3)
O2—C1—C2—C3	109.0 (3)	C1—C2—C3—C4	177.7 (2)
O1—C1—C2—C3	−73.2 (3)	H2—C2—C3—H3A	−62.4
N1—C2—C3—O3	61.5 (3)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···O4ⁱ	0.89	1.92	2.800 (3)	170
N1—H1B···O1ⁱⁱ	0.89	2.15	2.903 (3)	143
N1—H1B···O3	0.89	2.38	2.810 (3)	110
N1—H1C···O7ⁱⁱⁱ	0.89	2.30	3.069 (3)	145
N1—H1C···O2	0.89	2.33	2.646 (3)	101
N1—H1C···O6^iv	0.89	2.35	2.890 (3)	119
O3—H3···O5^v	0.82	2.14	2.906 (3)	156
O5—H5···O4^vi	0.79	1.79	2.580 (3)	179
O6—H6···O2^vi	0.77	1.76	2.514 (3)	169
O7—H7···O1	0.84	1.73	2.569 (3)	179

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

Experimental details

Crystal data
Chemical formula	C₄H₉NO₃·H₃AsO₄
M_r	261.07
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	293
a, b, c (Å)	10.1195 (6), 9.8062 (6), 8.9643 (6)
β (°)	99.098 (1)
V (Å³)	878.37 (10)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	3.88
Crystal size (mm)	0.45 × 0.03 × 0.01

Data collection
Diffractometer	Bruker SMART 1000 CCD area-detector diffractometer
Absorption correction	Multi-scan (SADABS; Bruker, 1999)
T_min, T_max	0.274, 0.962
No. of measured, independent and observed [I > 2σ(I)] reflections	7588, 3122, 2165
R_int	0.049
(sin θ/λ)_max (Å⁻¹)	0.756

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.037, 0.087, 0.94
No. of reflections	3122
No. of parameters	120
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.80, −0.74

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

Selected geometric parameters (Å, º) top

C1—O2	1.263 (3)	As1—O6	1.6769 (19)
C1—O1	1.264 (3)	As1—O7	1.699 (2)
As1—O4	1.639 (2)	As1—O5	1.704 (2)

O2—C1—C2—N1	−12.3 (3)	C1—C2—C3—O3	−59.3 (3)
O1—C1—C2—N1	165.4 (2)	N1—C2—C3—C4	−61.4 (3)
O2—C1—C2—C3	109.0 (3)	C1—C2—C3—C4	177.7 (2)
O1—C1—C2—C3	−73.2 (3)	H2—C2—C3—H3A	−62.4
N1—C2—C3—O3	61.5 (3)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···O4ⁱ	0.89	1.92	2.800 (3)	170
N1—H1B···O1ⁱⁱ	0.89	2.15	2.903 (3)	143
N1—H1B···O3	0.89	2.38	2.810 (3)	110
N1—H1C···O7ⁱⁱⁱ	0.89	2.30	3.069 (3)	145
N1—H1C···O2	0.89	2.33	2.646 (3)	101
N1—H1C···O6^iv	0.89	2.35	2.890 (3)	119
O3—H3···O5^v	0.82	2.14	2.906 (3)	156
O5—H5···O4^vi	0.79	1.79	2.580 (3)	179
O6—H6···O2^vi	0.77	1.76	2.514 (3)	169
O7—H7···O1	0.84	1.73	2.569 (3)	179

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

Acknowledgements

HSW thanks the Carnegie Trust for the Universities of Scotland for an undergraduate vacation studentship.

References

Bruker (1999). SMART (Version 5.624), SAINT (Version 6.02a) and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565. CrossRef IUCr Journals Google Scholar
Janczak, J., Zobel, D. & Luger, P. (1997). Acta Cryst. C53, 1901–1904. Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
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ISSN: 2053-2296

Volume 61| Part 6| June 2005| Pages m253-m255

doi:10.1107/S0108270105012291

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

A 1:1 adduct of DL-threonine and arsenic acid

Comment

Experimental

Crystal data

Data collection

Refinement

Supporting information

Acknowledgements

References

metal-organic compounds