Redetermination of bis­(S-methyl­thiuronium) sulfate

The single-crystal structure determination of the title compound, 2C₂H₇N₂S⁺·SO₄²⁻, confirms the previous structure determination [Stam (1962). Acta Cryst. 15, 317–322]. The present study includes the determination of the H-atom parameters, which revealed several inter­ionic N—H...O hydrogen bonds. The S atom of the sulfate anion is situated on a crystallographic twofold rotation axis.

Key indicators

• Single-crystal X-ray study
• T = 295 K
• Mean [sigma](S-O) = 0.002 Å
• R factor = 0.033
• wR factor = 0.092
• Data-to-parameter ratio = 13.5

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S1. Comment

The S-Methyl-thiuronium cation exhibits an almost planar thiourea-unit (r.m.s. deviation for N1,N2,C1,S1 = 0.0004 Å), the methyl-group differs from planarity to a considerable degree (C2—S1—C1—N2 - 18.4 (2)°). In the sulfate anion the coordination of the sulfur atom by the four oxygen atoms can be considered as slightly distorted tetrahedral, with O—S—O bond angles in the range 108.79 (13)–110.64 (13)° (Fig.1).

In the crystal structure, each C₂H₇N₂S⁺ cation is linked to two SO₄^- anions by four N—H···O hydrogen-bonds (Fig.2) with relatively short donor-acceptor distances (Tab.2).

Related literature

For an alternative method of preparation, see: Arndt (1921).

S2. Experimental

S-Methylisothiourea sulfate was synthesized in a modified literature procedure (Arndt 1921). Dimethylsulfate Me₂SO₄ (6.30 g, 49.95 mmol) was slowly added to a slurry of thiourea (NH₂)₂CS (7.60 g, 99.84 mmol) in 150 ml of water. The reaction mixture was stirred for 5 min at room temperature and then heated first to 30°C for 1.5 h and afterwards to 100°C under reflux. The solvent was destilled off. The colourless crystalline residue was washed with twice the volume of the crystalline residue of a mixture consisting of ethanole and water (10:1). The mixture was stirred for 5 min, filtrated and the crystalline solid dried in vacuo. Yield: 12.35 g (44.36 mmol, 44.5%). Anal. calc. (found) for C₄H₁₄N₄O₄S₃: C 17.26 (17.14), H 5.07 (5.20), N 20.13 (20.02), S 34.56 (33.52)%. ¹H-NMR (CDCl₃, 25°C): δ = 2.41 (s, 3H, CH₃), 4.63 (s, 4 H, H₂NCNH₂). ¹³C{¹H}-NMR: δ = 172.89 (s, H₂NCNH₂), 12.96 (s, CH₃). ¹⁴N-NMR: δ = - 280.22. IR (KBr, cm^-1): ν = 3989 w, 3903 w, 3840 w, 3799 w, 3748 w, 3736 w, 3673 w, 3650 w, 3211 versus, 3030 versus, 2802 s, 2367 ms, 2291 m, 2103 w, 2052 w, 1682 versus (n_sym C=N), 1564 s, 1438 s, 1419 s, 1321 m, 1150 s, 1127 s, 1078 s, 982 s, 732 s, 698 s, 602 s, 482 s, 429 m. Raman (200 mW, 25°C, cm^-1): ν = 3029 (11), 3009 (11), 2944 (33), 1678 (5) (n_sym C=N), 1436 (19), 1423 (16), 1326 (6), 1148 (40), 1133 (24), 1117 (31), 1075 (17), 976 (100), 733 (12), 702 (67), 603 (12), 485 (42), 431 (73), 268 (14), 146 (58). MS (FAB, 70 eV, NBA-Matrix, >5%); m/z: 359 (8), 91 (20) [M⁺], 89 (16) [(M - 2 H)⁺]. Crystallization from a saturated ethanole/water (10:1) solution at ambient temperature gave colourless X-ray quality crystals.

S3. Refinement

H atoms bonded to N atoms were located in a difference map and refined freely. Other H atoms were positioned geometrically and refined using a riding model (including free rotation about the S1—C2 bond), with C—H = 0.96 Å and with U_iso(H) = 1.5 times U_eq(C).

Computing details

Data collection: CAD-4 Software (Enraf–Nonius, 1994); cell refinement: CAD-4 Software (Enraf–Nonius, 1994); data reduction: OpenMolEN (Enraf–Nonius, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPIII (Burnett & Johnson, 1996) and DIAMOND (Brandenburg, 2005); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997.

Figures

	Fig. 1. Molecular structure of the title compound, showing the atomic numbering scheme and displacement ellipsoids drawn at the 50% probability level. Symmetry code: (i) -x + 1, y, -z + 1/2.
	Fig. 2. Part of the packing diagram of (I). Unique N—H···O interactions represented by dashed lines are shown for one molecule of (I). Symmetry codes: (ii) -x + 1, -y + 2, -z + 1; (iii) x, -y + 2, z + 1/2; (iv) x + 1/2, -y + 3/2, -z + 1.

bis(S-methylthiuronium) sulfate

Crystal data

2C2H7N2S^+·SO4^2^−	F(000) = 584
Mr = 278.37	Dx = 1.544 Mg m^−3
Orthorhombic, Pbcn	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2n 2ab	Cell parameters from 25 reflections
a = 11.3250 (19) Å	θ = 9–18°
b = 8.3903 (18) Å	µ = 0.62 mm^−1
c = 12.6041 (17) Å	T = 295 K
V = 1197.6 (4) Å^3	Block, colourless
Z = 4	0.57 × 0.53 × 0.47 mm

Data collection

Nonius MACH3 diffractometer	1098 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.006
Graphite monochromator	θmax = 26.0°, θmin = 3.0°
ο–2T–scan	h = −13→0
Absorption correction: ψ scan (North et al., 1968)	k = −10→0
Tmin = 0.717, Tmax = 0.749	l = 0→15
1175 measured reflections	3 standard reflections every 7200 min
1173 independent reflections	intensity decay: −0.7%

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)] = 0.033	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.092	w = 1/[σ^2(Fo^2) + (0.0501P)^2 + 0.8658P] where P = (Fo^2 + 2Fc^2)/3
S = 1.08	(Δ/σ)max < 0.001
1173 reflections	Δρmax = 0.61 e Å^−3
87 parameters	Δρmin = −0.36 e Å^−3
0 restraints	Extinction correction: SHELXL, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.065 (4)

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
S1	0.73533 (5)	0.62211 (8)	0.47370 (5)	0.0500 (3)
N1	0.69384 (17)	0.7584 (3)	0.65367 (14)	0.0402 (5)
H1	0.660 (2)	0.820 (3)	0.694 (2)	0.043 (7)*
H2	0.760 (3)	0.722 (3)	0.666 (2)	0.049 (7)*
N2	0.54254 (16)	0.7861 (2)	0.53413 (15)	0.0341 (4)
H3	0.507 (2)	0.840 (3)	0.577 (2)	0.045 (7)*
H4	0.518 (3)	0.783 (3)	0.469 (2)	0.051 (8)*
C1	0.64701 (17)	0.7327 (2)	0.56010 (15)	0.0312 (4)
C2	0.6354 (2)	0.5513 (3)	0.37475 (19)	0.0451 (6)
H5	0.6748	0.4749	0.3305	0.054*
H6	0.6088	0.6391	0.3322	0.054*
H7	0.5688	0.5018	0.4084	0.054*
S2	0.5000	0.92901 (8)	0.2500	0.0240 (2)
O1	0.58511 (12)	1.03141 (18)	0.30668 (11)	0.0384 (4)
O2	0.43656 (12)	0.82932 (19)	0.32713 (10)	0.0358 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
S1	0.0339 (4)	0.0703 (5)	0.0460 (4)	0.0141 (3)	0.0011 (2)	−0.0210 (3)
N1	0.0311 (9)	0.0572 (12)	0.0322 (9)	0.0152 (9)	−0.0035 (8)	−0.0054 (8)
N2	0.0295 (9)	0.0469 (10)	0.0259 (9)	0.0075 (8)	0.0003 (7)	−0.0028 (7)
C1	0.0275 (9)	0.0376 (10)	0.0285 (9)	0.0024 (7)	0.0036 (7)	0.0017 (8)
C2	0.0492 (13)	0.0477 (12)	0.0385 (11)	0.0041 (10)	0.0003 (10)	−0.0080 (9)
S2	0.0186 (3)	0.0364 (4)	0.0170 (3)	0.000	0.0003 (2)	0.000
O1	0.0327 (7)	0.0537 (9)	0.0289 (7)	−0.0127 (7)	−0.0031 (6)	−0.0053 (6)
O2	0.0283 (7)	0.0522 (8)	0.0270 (7)	−0.0070 (6)	0.0040 (5)	0.0072 (6)

Geometric parameters (Å, º)

S1—C1	1.7459 (19)	C2—H5	0.9600
S1—C2	1.786 (2)	C2—H6	0.9600
N1—C1	1.311 (3)	C2—H7	0.9600
N1—H1	0.82 (3)	S2—O2^i	1.4699 (13)
N1—H2	0.82 (3)	S2—O2	1.4699 (13)
N2—C1	1.307 (3)	S2—O1	1.4756 (14)
N2—H3	0.81 (3)	S2—O1^i	1.4756 (14)
N2—H4	0.86 (3)
C1—S1—C2	104.44 (10)	S1—C2—H6	109.5
C1—N1—H1	118.3 (18)	H5—C2—H6	109.5
C1—N1—H2	118.7 (19)	S1—C2—H7	109.5
H1—N1—H2	122 (3)	H5—C2—H7	109.5
C1—N2—H3	118.5 (19)	H6—C2—H7	109.5
C1—N2—H4	121.1 (19)	O2^i—S2—O2	110.64 (13)
H3—N2—H4	119 (3)	O2^i—S2—O1	109.40 (8)
N2—C1—N1	122.37 (19)	O2—S2—O1	109.29 (8)
N2—C1—S1	123.00 (16)	O2^i—S2—O1^i	109.29 (8)
N1—C1—S1	114.63 (15)	O2—S2—O1^i	109.40 (8)
S1—C2—H5	109.5	O1—S2—O1^i	108.79 (13)
C2—S1—C1—N2	−18.4 (2)	N1—N2—C1—S1	−180.0 (3)
C2—S1—C1—N1	161.61 (17)

Symmetry code: (i) −x+1, y, −z+1/2.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N2—H4···O2	0.86 (3)	2.05 (3)	2.895 (2)	165 (3)
N2—H3···O1^ii	0.81 (3)	2.10 (3)	2.908 (2)	177 (3)
N1—H1···O1^iii	0.82 (3)	2.08 (3)	2.889 (2)	175 (2)
N1—H2···O2^iv	0.82 (3)	2.05 (3)	2.856 (2)	167 (3)

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