CRYSTAL AND MOLECULAR STRUCTURE OF THE COMPLEX SALTS
DIETHYLAMMONIUM AND MORPHOLINIUM OF 5-NITROPYRIDINE SULFONATE

Iván Brito*¹, Danitza Vargas¹, Alejandro Cárdenas¹, Matías López-Rodriguez² and Oscar Wittke³

¹Facultad de Ciencias Básicas, Universidad de Antofagasta, Antofagasta, Chile. E-mail: ibrito@uantof.cl
²Centro de Productos Naturales Orgánicos "Antonio González", Instituto Universitario de Bio-Orgánica. Universidad de La Laguna, Astrofísico Francisco Sánchez Nº 2, La Laguna, Tenerife, Spain.
³Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Santiago, Chile.
(Received: September 1, 2003 - Accepted: November 18, 2003)

SUMMARY

The two title salts, (CH₂-CH₃)₂NH₂⁺ C₅NH₃NO₂SO₃^- and C₄H₈ONH₂⁺ C₅NH₃NO₂SO₃^-, crystallize in space group P2₁/n and P2₁/a respectively, with one ion pair in the asymmetric unit. In both structures, conventional hydrogen bonds link anions and cations in chains running along directions [1 0 1] and [0 1 0] for the first and second salts respectively.

KEY WORDS: Organic Salts, 5-nitropyridine sulfonate anion

INTRODUCTION

It was planned to synthesize diethylammine 5-nitropyridinesulfenamide, (CH₃-CH₂)₂NSC₅NH₃-5-NO₂ and morpholine 5-nitropyridinesulfenamide, C₄H₈ONSC₅NH₃-5-NO₂, by reaction of diethylammine and morpholine with 2,2 dithiobis(5-nitropyridine) respectively. But due to traces of water, both title compounds were formed instead of the expected one. The present X-ray work was undertaken to elucidate the structures of the obtained compounds. One thinks it is worthy of publication as a search in the Cambridge Structural Database7) (Version 5.24, update July 2003) revealed that the 5-nitropyridine sulfonate anion has been reported. Also, this ion may be of interest in the study of amino acids, because sulfonate salts have been used as cocrystallizing agents to purify amino acids and peptides and to form brightly-colored X-ray quality salt crystals^1-2).

EXPERIMENTAL

Synthesis was carried out by reaction of 1.1x10^-3 mol of (NO₂-C₅NH₃S)₂ and 4.5x10^-3 mol of the respective amines in methanol for 12h at -18ºC, using the metal-assisted technique³). Both compounds were crystallized by slow evaporation from diethyl ether solution. Pale-yellow crystals appeared after about a week, melting point 175 and 243ºC for the diethylammonium (1) and morpholinium (2) of 5-nitropyridine sulfonate salts, respectively. Both salts decomposed readily in air. For the X-ray study they were protected with a coating of cellulose adhesive Durofix. In spite of this, both compounds give poor, sparse data which only refined to R= 0.098 and R=0.096 for (1) and (2) respectively. In both compounds, though all H atoms were located from a difference Fourier map, due to the low ratio of reflections to parameters they were fixed and treated isotropically [U= 0.05]. Geometrical calculations were made with PARST⁴). The diffraction data were recorded in the Instituto Universitario de Bio-Orgánica "Antonio González", Tenerife, Spain.

RESULTS AND DISCUSSION

The asymmetric units of both salts have the formula (CH₂-CH₃)₂NH₂⁺ ·C₅NH₃NO₂SO₃^- (1) and C₄H₈ONH₂⁺ C₅NH₃NO₂SO₃- (2) respectively. Tables I and II shows structure determination summary. The molecular structure including the atom labelling scheme for (1) and (2) are illustrated in Fig. 1 and Fig. 2. The packing for (1) and (2) in the unit cell viewed down the c axis, showing the hydrogen-bonding interactions as broken lines are illustrated in Fig. 3 and Fig 4 . Table III gives for (1) and (2) the atomic coordinates and equivalent isotropic displacement parameters for all non-H atoms. Table IV shows for (1) and (2) selected geometric parameters. Table V shows for (1) and (2) hydrogen-bonding geometry. In both structures the aromatic ring in the 5-nitropyridine sulfonate anion is planar. The maximum atomic deviation from the least-squares plane is 0.027 and 0.0024 Å for (1) and (2) respectively. The distances and angles for this anion are essentially identical in the range 1.338(13)-1.436(13), mean 1.377(13); 1.367(10)-1.388(10), mean 1.377(10) and 116.4(11)-122.5(12), mean 120.1(11); and 117.3(7)-123.6(7), mean 120.0(7) for (1) and (2) respectively. In both structures the sulfonate S-O geometries compare well with those found in other sulfonate structures. As expected, p-nitro group is slightly rotated out of their respective aromatic plane, 5.0 (8) and 5.6 (8) º for (1) and (2) respectively. In (2), one sulfonate oxygen is almost coplanar with the aromatic ring. For (1) and (2) the average N-O bond length are in usual range (Table IV) for aromatic NO₂ groups in accord with similar structures reported in Cambridge Structural Database ⁷) . The C-S bond distances 1.772(11) and 1.783(7) Å for (1) and (2) are comparable with the 1.770Å value reported for 5-nitro -2-(2 pyridinylthio)pyridine⁸) and slightly longer than 1.766(2) value reported for N-(-p-toluenesulfonyl)azacyclotridecane ⁹⁾. The morpholine cation adopts a chair conformation with atoms N2 and O6 displaced -0.1354 (7) and 0.1375 (7) Å on the either side from the best least-squares plane through atoms C6, C7, C8 and C9. This is also confirmed by the Cremer & Pople¹⁰) puckering parameters q2= 0.026(7)Å, q₃=-0.566(7)Å, j ₂=28(2)º Q_T=0.567(7) Å, q ₂=177.4(7) º. The average distances values are C-C 1.503(12), C-O 1.417(10) and C-N 1.491(10 ) Å. The valence angles have mean values of 110.4(7). In the diethylamine cation the distances and angles bond are normal.

Table I. Structure determination summary for diethylammonium 5-nitropyridine sulfonate

Data collection

Empirical formula=(CH2-CH3)2NH2+·C5H3NNO2SO3- Mr = 277.30 Dalton Crystal system = monoclinic Space group = P21/n a = 6.967(3) Å b = 23.499(7) Å c = 8.494(3) Å b = 109.34º (3) V = 1312.1 (8) Å3 Enraf- Nonius CAD-4 Diffractometer w / 2q scans 4169measured reflections 3940 independent reflections 459 reflections with I>2s (I) R int = 0.4709 q max = 30.4º h = -9 ® 9 k = -33 ® 0 l = 0 ® 12 3 Standard reflections frecuency 120 min intensity decay : none	Z = 4 DX = 1.404 mg m-3 Mo Ka radiation Cell parameters from 30 reflections q = 4.05 - 30.40 0 m = 0.264 mm- 1
Solution and Refinement System used: SHELX 93- SHELXS 86 5-6) Solution: Direct method. Refinement Methods: Full- Matrix Least- Squares Refinement on F2 R (F) = 0.0984 WR(F2) = 0.0954 S = 0.825 3940 reflection 164 parameters

Table II. Structure determination summary for morpholinium 5-nitropyridine sulfonate

Data collection

Empirical formula= C4H8ONH2+· C5 NH3NO2SO3- Mr = 291.28 Dalton Crystal system = monoclinic Space group = P21/a a = 12.858(3) Å b = 7.242 (1) Å c = 13.816(3) Å b = 103.25º(2) Å V = 1252.3(4) Å3 Enraf- Nonius CAD-4 Diffractometer w / 2q scans measured reflections 3907 independent reflections 3771 819 reflections with I>2s (I) R int = 0.1070 q max = 30.4º h = -17® 18 k = -10 ® 0 l = -19 ® 0 3 Standard reflections frecuency 120 min intensity decay : none	Z = 4 DX = 1.545 mg ∙ m-3 Mo Ka radiation Cell parameters from 30 reflections q = 3.03 - 30.390 m = 0.287 mm- 1 T = 293(2) K Crystal size= 0.50x0.40x0.20 mm
Solution and Refinement System used: SHELX 93- SHELXS 86 5- 6) Solution: Direct method. Refinement Methods: Full- Matrix Least- Squares Refinement on F2 R (F) = 0.0960 WR(F2) = 0.2305 S = 0.852 3771 reflection 174 parameters

Table III. Atomic coordinates (Åx10⁴) and equivalent isotropic displacement parameters (Ųx10³). U_eq=(1/3)å iåjUijai*aj*aiaj for:

Diethylammonium 5-nitropyridine sulfonate

Atom	x	y	z	U(eq)
S(1)	7391(6)	1559(2)	5372(5)	51(1)
O(1)	7392(9)	1666(3)	3695(8)	67(3)
O(2)	5514(12)	1383(3)	5535(10)	90(3)
O(3)	8368(10)	2026(3)	6488(9)	63(3)
O(4)	14968(14)	-305(5)	7711(16)	112(5)
O(5)	13122(15)	-619(4)	9104(12)	100(4)
N(1)	13480(20)	-303(6)	8102(17)	78(4)
N(2)	8694(17)	582(5)	7143(13)	88(4)
N(3)	4319(16)	1891(4)	650(11)	58(3)
C(1)	9127(17)	990(5)	6090(14)	46(3)
C(2)	10852(18)	963(5)	5671(13)	47(3)
C(3)	12239(16)	530(6)	6279(15)	52(4)
C(4)	11943(18)	153(5)	7357(15)	46(4)
C(5)	10190(20)	146(5)	7788(14)	54(4)
C(6)	7140(20)	2363(7)	-85(18)	114(6)
C(7)	5360(20)	1968(6)	-636(16)	82(5)
C(8)	2440(20)	1537(6)	141(16)	82(5)
C(9)	1645(19)	1457(6)	1523(19)	98(6)
Morpholinium 5-nitropyridine sulfonate
Atom	x	y	z	U(eq)
S(1)	8502(2)	1442(3)	7409(2)	52(1)
N(1)	6834(7)	1425(11)	11109(6)	60(2)
N(2)	8858(5)	6591(9)	6496(4)	43(2)
N(3)	6932(6)	1590(12)	8442(6)	77(2)
O(1)	9606(5)	1186(15)	7681(5)	129(4)
O(2)	8149(8)	3195(9)	6930(5)	107(3)
O(3)	7944(5)	-46(8)	6814(4)	62(2)
O(4)	7486(6)	1435(10)	11921(5)	79(2)
O(5)	5889(6)	1399(12)	11032(5)	88(2)
O(6)	10183(5)	7564(9)	5183(5)	65(2)
C(1)	8023(6)	1437(11)	8522(5)	36(2)
C(2)	8708(6)	1301(12)	9436(6)	51(2)
C(3)	8338(6)	1266(12)	10291(6)	48(2)
C(4)	7251(7)	1401(11)	10193(6)	44(2)
C(5)	6535(6)	1558(12)	9295(6)	54(2)
C(6)	8470(6)	6485(12)	5378(5)	51(2)
C(7)	9070(8)	7864(12)	4916(6)	57(2)
C(8)	10561(7)	7756(15)	6229(7)	73(3)
C(9)	10024(7)	6384(13)	6784(6)	57(2)

Table IV. Selected geometric parameters (Å, º) for:

Diethylammonium 5-nitropyridine sulfonate

S(1)-O(2)	1.422(8)	S(1)-O(1)	1.446(6)
S(1)-O(3)	1.462(7)	S(1)-C(1)	1.772(11)
N(1)-C(4)	1.499(16)	N(2)-C(1)	1.411(12)
N(2)-C(5)	1.436(13)	N(3)-C(8)	1.487(15)
N(3)-C(7)	1.507(14)	O(2)-S(1)-C(1)	107.0(6)
O(2)-S(1)-O(1)	116.5(5)	O(2)-S(1)-O(3)	113.6(5)
O(1)-S(1)-O(3)	110.9(5)	O(3)-S(1)-C(1)	103.0(5)
O(1)-S(1)-C(1)	104.3(5)	O(4)-N(1)-C(4)	116.9(14)
O(4)-N(1)-O(5)	126.4(17)	C(1)-N(2)-C(5)	116.4(11)

Morpholinium 5-nitropyridine sulfonate
S(1)-O(1)	1.395(7)	S(1)-O(3)	1.442(6)
S(1)-O(2)	1.455(8)	S(1)-C(1)	1.782(7)
N(1)-C(4)	1.483(10)	N(2)-C(9)	1.468(10)
N(2)-C(6)	1.513(9)	N(3)-C(1)	1.387(10)
N(3)-C(5)	1.388(10)	O(6)-C(7)	1.411(10)
O(6)-C(8)	1.422(10)	O(1)-S(1)-O(2)	115.5(6)
O(1)-S(1)-O(3)	113.4(5)	O(1)-S(1)-C(1)	107.3(4)
O(3)-S(1)-O(2)	109.3(4)	O(2)-S(1)-C(1)	105.1(4)
O(3)-S(1)-C(1)	105.4(4)	O(5)-N(1)-C(4)	118.9(8)
O(5)-N(1)-O(4)	122.9(8)	C(9)-N(2)-C(6)	110.4(6)
O(4)-N(1)-C(4)	118.2(8)	C(1)-N(3)-C(5)	119.6(7)
C(7)-O(6)-C(8)	109.9(7)	N(3)-C(1)-S(1)	118.3(6)
C(2)-C(1)-S(1)	121.4(6)	C(3)-C(4)-N(1)	118.3(7)

The dominant feature of the crystal packing is the presence of conventional hydrogen bonds. In (1) three normal intermolecular hydrogen bonds are detected, two between sulfonate and diethylammonium ions and one hydrogen bond of type C-H...O between a methyl group and a nitro group with the anions and cations linked in a chain running along [1 0 1]. The following intramolecular hydrogen bond geometry was found: H3A... O1 1.93, N3...O1 2.80 Å and N3-H3A...O1 158.8º; H3B...O3 1.87, N3...O3 2.78Å and N3-H3B...O3 173.6º ; H6A....O3 2.48 Å, C6...O3 3.40 Å, C6-H6A...O3 157.5º (Table V). In (2) three normal intermolecular hydrogen bonds are detected, two between sulfonate and morpholinammoniun ions and one between morpholinammoniun ions and a nitro group, with the anions and cations linked in a chain running along [0 1 0]. The N2 atom acts as a donor towards two O atoms, O2 and O4. The following intramolecular hydrogen bond geometry was found: H2A... O3 1.90, N2...O3 2.78 Å and N2-H2A...O3 162.1 º; H2B...O2 1.93, N2...O2 2.74Å, N2-H2B...O2 147.3 º; H2B... O4 2.47, N2...O4 3.08 Å and N2-H2B...O4 125.6 º. (Table V)

Table V. Hydrogen-Bonding geometry (Å, º) for:

Diethylammonium 5-nitropyridine sulfonate

D-H...A	D-H	H...A	D...A	D-H..A
N3-H3A..O1i	0.92	1.93	2.80	158.8
N3-H3B..O3ii	0.91	1.87	2.78	173.6
C6-H6A..O3iii	0.96	2.48	3.39	157.5
Symmetry codes. (i) 1+x,y,z ; (ii)1/2+x,1/2-y, -1/2 +z ; (iii) 1+x,y,-1+z
Morpholinium 5-nitropyridine sulfonate
D-H...A	D-H	H...A	D...A	D-H...A
N2-H2A...O3 i	0.92	1.90	2.78	162.1
N2-H2B...O2	0.91	1.93	2.74	147.3
N2-H2B...O4 ii	0.91	2.47	3.08	125.6
Symmetry codes. (i) x,-1+y,z ; (ii) 1/2- x,-1/2+y,-z

ACKNOWLEDGMENTS

This work was supported by grants from Fondecyt (1030052) and Universidad de Antofagasta (PRO-1345-02).

We thank the Spanish Research Council (CSIC) for providing us with a free-of-charge license to the CSD system.

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