tert-Butyl­ammonium di­hydrogenarsenate

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

doi:10.1107/S1600536804020963

metal-organic compounds

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 60| Part 10| October 2004| Pages m1359-m1361

https://doi.org/10.1107/S1600536804020963

tert-Butylammonium dihydrogenarsenate

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 28 July 2004; accepted 25 August 2004; online 4 September 2004)

The title compound, (C₄H₁₂N)[H₂AsO₄], contains a network of tert-butylammonium cations and dihydrogenarsenate anions [d_av(As—O) = 1.682 (2) Å]. The crystal packing involves N—H⋯O [d_av(H⋯O) = 1.96 Å, θ_av(N—H⋯O) = 169° and d_av(N⋯O) = 2.837 (3) Å] and O—H⋯O [d_av(H⋯O) = 1.68 Å, θ_av(O—H⋯O) = 169° and d_av(O⋯O) = 2.626 (2) Å] hydrogen bonds, resulting in a layered structure.

Comment

The title compound, (I) (Fig. 1), was prepared as part of our ongoing structural studies of hydrogen-bonding interactions in protonated amine (di)hydrogen arsenates (Lee & Harrison, 2003a ,b ,c ).

The [H₂AsO₄]⁻ dihydrogenarsenate group in (I) shows its normal tetrahedral geometry [d_av(As—O) = 1.682 (2) Å], with the protonated As1—O3 and As1—O4 vertices showing their expected lengthening relative to the unprotonated As—O bonds, which have formal partial double-bond character (Table 1). The tert-butylammonium cation shows no unusual geometrical features.

As well as electrostatic attractions, the component species in (I) interact by means of a network of cation-to-anion N—H⋯O and anion-to-anion O—H⋯O hydrogen bonds (Table 2). The [H₂AsO₄]⁻ units are linked into polymeric chains propagating along [010] by way of inversion-generated pairs of O—H⋯O bonds, alternately involving O3—H1⋯O1 and O4—H2⋯O1 links (Fig. 2). This results in every [H₂AsO₄]⁻ tetrahedron in the chain making one hydrogen bond to each of its neighbours and accepting one hydrogen bond from each neighbour. The As⋯Asⁱ (via O3—H1⋯O1ⁱ) and As⋯Asⁱⁱ (via O4—H2⋯O1ⁱⁱ) separations are 4.3002 (4) and 4.2662 (3) Å, respectively (see Table 2 for symmetry codes). Similar hydrogen-bonded chains of [H₂AsO₄]⁻ anions have been seen in piperidinum dihydrogenarsenate, (C₅H₁₂N)[H₂AsO₄] (Lee & Harrison, 2003b), although in this case they are generated by a 2₁ screw axis.

As shown in Table 2, the organic species interacts with the dihydrogenarsenate chains by way of three N—H⋯O hydrogen bonds [d_av(H⋯O) = 1.96 Å, θ_av(N—H⋯O) = 169° and d_av(N⋯O) = 2.837 (3) Å], such that each tert-butylammonium cation cross-links a dihydrogenarsenate chain to its neighbour by forming two hydrogen bonds to one chain, and one to the other. This results in neutral (101) layers (Fig. 3) of stoichiometry (C₄H₁₂N)[H₂AsO₄], which interact with each other by van der Waals forces.

Figure 1
The asymmetric unit of (I

) (50% displacement ellipsoids). H atoms are drawn as small spheres of arbitrary radius and the hydrogen bond is indicated by a dashed line. C—H H atoms have been omitted for clarity.

Figure 2
Detail of a hydrogen-bonded dihydrogenarsenate/tert-butylammonium sheet in (I

). Colour key: [H₂AsO₄]⁻ tetrahedra green, O atoms red, H atoms grey, C atoms blue, N atoms green (all radii arbitrary). The H⋯O portions of the O—H⋯O and N—H⋯O hydrogen bonds are highlighted in yellow and orange, respectively. Symmetry codes as in Table 2

; additionally, (v) x,y − 1,z; (vi) x, 1 + y, z.

Figure 3
Projection of (I

) onto (010). The colour key is as in Fig. 2

Experimental

An aqueous tert-butylamine solution (10 ml of 0.5 M) was added to a H₃AsO₄ solution (10 ml of 0.5 M), resulting in a clear solution. A mass of plate-shaped and rod-like crystals of (I) grew as the water evaporated over the course of a few days.

Crystal data

(C₄H₁₂N)[H₂AsO₄]
M_r = 215.08
Monoclinic, P2₁/n
a = 9.7364 (5) Å
b = 6.3254 (3) Å
c = 14.2606 (8) Å
β = 94.864 (1)°
V = 875.10 (8) Å³
Z = 4
D_x = 1.633 Mg m⁻³
Mo Kα radiation
Cell parameters from 3025 reflections
θ = 2.4–32.4°
μ = 3.85 mm⁻¹
T = 293 (2) K
Bar, colourless
0.55 × 0.15 × 0.05 mm

Data collection

Bruker SMART1000 CCD diffractometer
ω scans
Absorption correction: multi-scan (SADABS; Bruker, 1999 ) T_min = 0.226, T_max = 0.831
8742 measured reflections
3165 independent reflections
1807 reflections with I > 2σ(I)
R_int = 0.023
θ_max = 32.5°
h = −10 → 14
k = −7 → 9
l = −21 → 21

Refinement

Refinement on F²
R[F² > 2σ(F²)] = 0.024
wR(F²) = 0.064
S = 0.88
3165 reflections
95 parameters
H-atom parameters constrained
w = 1/[σ²(F_o²) + (0.0332P)²] where P = (F_o² + 2F_c²)/3
(Δ/σ)_max = 0.001
Δρ_max = 0.47 e Å⁻³
Δρ_min = −0.51 e Å⁻³

Table 1
Selected bond distances (Å)

As1—O2	1.6412 (13)
As1—O1	1.6687 (13)
As1—O3	1.7061 (13)
As1—O4	1.7101 (14)

Table 2
Hydrogen-bonding geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O3—H1⋯O1ⁱ	0.97	1.62	2.5752 (19)	166
O4—H2⋯O1ⁱⁱ	0.94	1.74	2.6763 (19)	172
N1—H3⋯O2	0.89	1.92	2.801 (2)	168
N1—H4⋯O2ⁱⁱⁱ	0.89	1.88	2.765 (2)	173
N1—H5⋯O3^iv	0.89	2.07	2.944 (2)	166
Symmetry codes: (i) -x,-y,1-z; (ii) -x,1-y,1-z; (iii) $[{\script{1\over 2}}-x,y-{\script{1\over 2}},{\script{1\over 2}}-z]$ ; (iv) $[{\script{1\over 2}}-x,{\script{1\over 2}}+y,{\script{1\over 2}}-z]$ .

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

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

Supporting information

Crystal structure: contains datablocks I, hw35. DOI: https://doi.org/10.1107/S1600536804020963/hg6081sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536804020963/hg6081Isup2.hkl

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; molecular graphics: ORTEP-3 (Farrugia, 1997) and ATOMS (Shape Software, 1999); software used to prepare material for publication: SHELXL97.

tert-Butylammonium dihydrogenarsenate top

Crystal data top

(C₄H₁₂N)[H₂AsO₄]	F(000) = 440
M_r = 215.08	D_x = 1.633 Mg m⁻³
Monoclinic, P2₁/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 3025 reflections
a = 9.7364 (5) Å	θ = 2.4–32.4°
b = 6.3254 (3) Å	µ = 3.85 mm⁻¹
c = 14.2606 (8) Å	T = 293 K
β = 94.864 (1)°	Bar, colourless
V = 875.10 (8) Å³	0.55 × 0.15 × 0.05 mm
Z = 4

Data collection top

Bruker SMART1000 CCD diffractometer	3165 independent reflections
Radiation source: fine-focus sealed tube	1807 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.023
ω scans	θ_max = 32.5°, θ_min = 2.4°
Absorption correction: multi-scan (SADABS; Bruker, 1999)	h = −10→14
T_min = 0.226, T_max = 0.831	k = −7→9
8742 measured reflections	l = −21→21

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)] = 0.024	Hydrogen site location: difmap (O-H) and geom (C-H and N-H)
wR(F²) = 0.064	H-atom parameters constrained
S = 0.88	w = 1/[σ²(F_o²) + (0.0332P)²] where P = (F_o² + 2F_c²)/3
3165 reflections	(Δ/σ)_max = 0.001
95 parameters	Δρ_max = 0.47 e Å⁻³
0 restraints	Δρ_min = −0.51 e Å⁻³

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
As1	0.096480 (18)	0.25182 (3)	0.428460 (11)	0.02877 (6)
O1	−0.07070 (14)	0.2606 (2)	0.44605 (10)	0.0360 (3)
O2	0.13620 (15)	0.3528 (2)	0.32825 (9)	0.0424 (4)
O3	0.15368 (15)	−0.0032 (2)	0.43072 (9)	0.0402 (3)
H1	0.1102	−0.0863	0.4773	0.048*
O4	0.18923 (15)	0.3676 (3)	0.52194 (10)	0.0482 (4)
H2	0.1545	0.5006	0.5378	0.058*
N1	0.38027 (16)	0.2563 (2)	0.24651 (10)	0.0334 (3)
H3	0.3062	0.2725	0.2783	0.040*
H4	0.3824	0.1249	0.2243	0.040*
H5	0.3766	0.3474	0.1988	0.040*
C1	0.5091 (2)	0.2971 (3)	0.31140 (15)	0.0380 (5)
C2	0.4956 (3)	0.5164 (4)	0.35241 (18)	0.0608 (7)
H6	0.4147	0.5224	0.3865	0.091*
H7	0.4880	0.6185	0.3024	0.091*
H8	0.5755	0.5471	0.3943	0.091*
C3	0.5148 (3)	0.1313 (4)	0.38747 (18)	0.0643 (7)
H9	0.5211	−0.0062	0.3597	0.097*
H10	0.4328	0.1392	0.4203	0.097*
H11	0.5940	0.1553	0.4309	0.097*
C4	0.6306 (3)	0.2805 (4)	0.2525 (2)	0.0677 (8)
H12	0.6329	0.1418	0.2254	0.102*
H13	0.7143	0.3051	0.2916	0.102*
H14	0.6217	0.3842	0.2032	0.102*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
As1	0.03246 (9)	0.02705 (9)	0.02761 (8)	0.00106 (11)	0.00722 (6)	−0.00055 (9)
O1	0.0324 (6)	0.0318 (7)	0.0448 (7)	0.0000 (7)	0.0090 (5)	0.0018 (7)
O2	0.0539 (10)	0.0385 (9)	0.0368 (8)	0.0031 (7)	0.0162 (7)	0.0104 (6)
O3	0.0507 (9)	0.0294 (7)	0.0433 (8)	0.0085 (7)	0.0196 (6)	0.0027 (6)
O4	0.0452 (9)	0.0500 (10)	0.0474 (9)	0.0071 (8)	−0.0072 (7)	−0.0177 (7)
N1	0.0389 (8)	0.0304 (7)	0.0312 (7)	0.0000 (9)	0.0053 (6)	0.0001 (8)
C1	0.0392 (11)	0.0367 (12)	0.0371 (10)	−0.0018 (8)	−0.0017 (8)	0.0006 (7)
C2	0.0685 (18)	0.0454 (14)	0.0640 (16)	−0.0033 (13)	−0.0198 (13)	−0.0125 (12)
C3	0.0716 (19)	0.0592 (17)	0.0592 (16)	−0.0032 (15)	−0.0123 (13)	0.0228 (14)
C4	0.0391 (12)	0.099 (2)	0.0653 (16)	−0.0058 (14)	0.0064 (11)	−0.0033 (15)

Geometric parameters (Å, º) top

As1—O2	1.6412 (13)	C1—C4	1.511 (3)
As1—O1	1.6687 (13)	C1—C2	1.515 (3)
As1—O3	1.7061 (13)	C2—H6	0.9600
As1—O4	1.7101 (14)	C2—H7	0.9600
O3—H1	0.9710	C2—H8	0.9600
O4—H2	0.9415	C3—H9	0.9600
N1—C1	1.516 (3)	C3—H10	0.9600
N1—H3	0.8900	C3—H11	0.9600
N1—H4	0.8900	C4—H12	0.9600
N1—H5	0.8900	C4—H13	0.9600
C1—C3	1.506 (3)	C4—H14	0.9600

O2—As1—O1	115.01 (7)	C2—C1—N1	107.28 (18)
O2—As1—O3	106.49 (7)	C1—C2—H6	109.5
O1—As1—O3	110.46 (7)	C1—C2—H7	109.5
O2—As1—O4	111.36 (8)	H6—C2—H7	109.5
O1—As1—O4	109.03 (7)	C1—C2—H8	109.5
O3—As1—O4	103.90 (7)	H6—C2—H8	109.5
As1—O3—H1	111.3	H7—C2—H8	109.5
As1—O4—H2	113.1	C1—C3—H9	109.5
C1—N1—H3	109.5	C1—C3—H10	109.5
C1—N1—H4	109.5	H9—C3—H10	109.5
H3—N1—H4	109.5	C1—C3—H11	109.5
C1—N1—H5	109.5	H9—C3—H11	109.5
H3—N1—H5	109.5	H10—C3—H11	109.5
H4—N1—H5	109.5	C1—C4—H12	109.5
C3—C1—C4	111.7 (2)	C1—C4—H13	109.5
C3—C1—C2	111.0 (2)	H12—C4—H13	109.5
C4—C1—C2	112.1 (2)	C1—C4—H14	109.5
C3—C1—N1	107.39 (18)	H12—C4—H14	109.5
C4—C1—N1	107.17 (18)	H13—C4—H14	109.5

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O3—H1···O1ⁱ	0.97	1.62	2.5752 (19)	166
O4—H2···O1ⁱⁱ	0.94	1.74	2.6763 (19)	172
N1—H3···O2	0.89	1.92	2.801 (2)	168
N1—H4···O2ⁱⁱⁱ	0.89	1.88	2.765 (2)	173
N1—H5···O3^iv	0.89	2.07	2.944 (2)	166

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

Acknowledgements

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

References

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