2-Methyl-4-thio­cyanato­aniline

Lange, E. de; Hosten, E.C.; Betz, R.

doi:10.1107/S2414314625002160

organic compounds

IUCrDATA

ISSN: 2414-3146

Volume 10| Part 3| March 2025| x250216

https://doi.org/10.1107/S2414314625002160

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2-Methyl-4-thiocyanatoaniline

Erik de Lange,^a Eric Cyriel Hosten ^a and Richard Betz ^a ^*

^aNelson Mandela University, Summerstrand Campus, Department of Chemistry, University Way, Summerstrand, PO Box 77000, Port Elizabeth, 6031, South Africa
^*Correspondence e-mail: richard.betz@mandela.ac.za

Edited by M. Bolte, Goethe-Universität Frankfurt, Germany (Received 6 March 2025; accepted 7 March 2025; online 14 March 2025)

The title compound, C₈H₈N₂S, is a rhodanided derivative of ortho-toluidine. Classical hydrogen bonds of the N—H⋯N type, as well as C—H⋯N contacts, connect molecules of the title compound into a three-dimensional network in the crystal structure.

Keywords: crystal structure; rhodanided derivative; hydrogen bonds.

CCDC reference: 2429624

Structure description

Aniline and its derivatives are valuable starting materials in synthetic organic chemistry and have found ample use in industrial processes, as is apparent in the historic establishment of the artificial dye and, subsequently, pharmaceutical industry (Griess, 1879 ; Bopp et al., 1891 ). As an activated aromatic system, a large number of reactions is available for further functionalization of the phenyl group as well as the ipso-substitution of the amine functionality itself (Becker et al., 2000 ; Sandmeyer, 1884 ), which allows for tailoring the physicochemical and spectroscopic properties of the target molecules over a seemingly endless range. One particularly intriguing substituent on a phenyl moiety is the rhodanide (thiocyanate) group as its cumulated double-bonding system allows for a number of fundamental follow-up reactions. In a continuation of our ongoing interest in structural aspects of aromatic amines such as halogenated anilines (Betz & Klüfers, 2008 ; Betz, 2015 ; Hosten & Betz, 2021a ,b ), anilines bearing protic (Betz & Gerber, 2011 ; Betz, Klüfers & Mayer, 2008 ; Betz et al., 2011a ) or sulfur-based (Betz et al., 2011b ) or organic substituents (Islor et al., 2013 ; Hosten & Betz, 2021c ), we set out to explore the influence of a rhodanide group attached to the aromatic core of an aniline derivative. Structural information about organic thiocyanates is still comparatively scant, however, the molecular and crystal structures have been published for derivatives bearing the SF₅ group (Okazaki et al., 2014 ), an acetyl substituent (Kalaramna & Goswami, 2021 ), azo functionalities (Kakati & Chaudhuri, 1968 ; Aldoshin et al., 1977 ; Sanjib et al., 2004 ) or several methoxy groups (Ghosh et al., 2019 ). Most intriguing in connection with our present study is structural information about two aniline derivatives bearing a thiocyanate group (See & Zhao, 2018 ; Isakov et al., 1977 ). Slightly more structural information is apparent for aromatic isothiocyanated compounds such as, e.g., the family of trifluoromethyl benzene derivatives (Hasija et al., 2023 ; Mandal et al., 2023 ).

The title compound is a derivative of ortho-toluidine bearing a rhodanide group in para-position to the amino group. The latter is bonded to the phenyl moiety via its sulfur atom. The thiocyanate group is tilted out of plane of the aromatic moiety to an almost perpendicular position with the pertaining C7—S1—C1—C2 torsion angle measuring 86.6 (2)°. The C—S bond length of 1.692 (3) Å is in good agreement with other pertaining bond lengths in aromatic thiocyanates whose molecular and crystal structure have been determined on grounds of diffraction studies on single crystals and whose metrical parameters have been deposited with the Cambridge Structural Database (Allen, 2002 ). Intracyclic C—C—C angles span a narrow range of only 118.4 (2)–121.6 (2)° with the smallest angle found on the carbon atom bearing the methyl group and the largest angle on the carbon atom in between the carbon atoms bearing the rhodanide and the methyl group, respectively (Fig. 1).

Figure 1
The molecular structure of the title compound, with atom labels and anisotropic displacement ellipsoids (drawn at the 50% probability level).

In the crystal, classical hydrogen bonds of the N—H⋯N type are observed next to C—H⋯N contacts (Table 1) whose range falls by more than 0.1 Å below the sum of van der Waals radii of the atoms participating in them. While the classical hydrogen bonds are established only by one of the two hydrogen atoms of the amino functionality as donor and the SCN group nitrogen atom as acceptor, the C—H⋯N contacts are supported by one of the hydrogen atoms of the methyl group as well as the hydrogen atom on the carbon atom next to the amino group. The acceptor nitrogen for the latter type of interactions is, invariably, the nitrogen atom of the rhodanide group, thus denoting the latter atom as a threefold acceptor. In terms of graph-set analysis (Etter et al., 1990 ; Bernstein et al., 1995 ), the descriptor for the classical hydrogen bonds is C₁¹(9) on the unary level while the C—H⋯N contacts necessitate a C₁¹(7) C₁¹(8) on the same level. Overall, these interactions connect the molecules to a three-dimensional network in the crystal structure. While π-stacking is not a prominent feature in the crystal structure of the title compound as the shortest distance between two centers of gravity was measured at 4.4380 (16) Å, it is worthwhile pointing out the short distance between the π systems as well as the sulfur atoms in neighbouring molecules as the S⋯C_g distance of only about 3.43 Å is comparable to the range that has been debated in the literature as an energetic minimum for the system benzene–hydrogen sulfide as well as in connection with pertaining metrical data obtained from the Protein Data Bank (Ringer et al., 2007 ) (Fig. 2).

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C8—H8A⋯N1ⁱ	0.98	2.61	3.482 (4)	148
C5—H5⋯N1ⁱⁱ	0.95	2.63	3.576 (3)	172
N2—H2B⋯N1ⁱⁱⁱ	0.85 (4)	2.38 (4)	3.185 (4)	157 (3)
Symmetry codes: (i) $[-x+{\script{1\over 2}}, -y+1, z-{\script{1\over 2}}]$ ; (ii) $[-x+1, y+{\script{1\over 2}}, -z+{\script{3\over 2}}]$ ; (iii) $[-x+{\script{3\over 2}}, -y+1, z-{\script{1\over 2}}]$ .

Figure 2
Intermolecular contacts, viewed approximately along [110].

Synthesis and crystallization

The compound was obtained following a standard procedure by reacting ortho-toluidine with KSCN and bromine in acetic acid (Becker et al., 2000). Crystals suitable for the diffraction study were obtained upon free evaporation of the reaction mixture after workup at room temperature.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2.

Table 2
Experimental details

Crystal data
Chemical formula	C₈H₈N₂S
M_r	164.22
Crystal system, space group	Orthorhombic, P2₁2₁2₁
Temperature (K)	200
a, b, c (Å)	4.4380 (2), 10.5115 (4), 17.3105 (6)
V (Å³)	807.54 (6)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	0.33
Crystal size (mm)	0.52 × 0.20 × 0.20

Data collection
Diffractometer	Bruker APEXII CCD
Absorption correction	Multi-scan (SADABS; Krause et al., 2015 )
T_min, T_max	0.673, 0.746
No. of measured, independent and observed [I > 2σ(I)] reflections	26844, 1996, 1757
R_int	0.062
(sin θ/λ)_max (Å⁻¹)	0.667

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.043, 0.075, 1.16
No. of reflections	1996
No. of parameters	109
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.26, −0.23
Absolute structure	Flack x determined using 628 quotients [(I⁺)−(I⁻)]/[(I⁺)+(I⁻)] (Parsons et al., 2013 )
Absolute structure parameter	0.00 (4)
Computer programs: APEX2 and SAINT (Bruker, 2014 ), SHELXS97 (Sheldrick 2008 ), ORTEP-3 (Farrugia, 2012 ), Mercury (Macrae et al., 2020 ), SHELXL2019/3 (Sheldrick, 2015 ) and PLATON (Spek, 2020 ).

Structural data

CCDC reference: 2429624

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2414314625002160/bt4165sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314625002160/bt4165Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2414314625002160/bt4165Isup3.cml

checkCIF report

Computing details top

2-Methyl-4-thiocyanatoaniline top

Crystal data top

C₈H₈N₂S	D_x = 1.351 Mg m⁻³
M_r = 164.22	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, P2₁2₁2₁	Cell parameters from 9369 reflections
a = 4.4380 (2) Å	θ = 2.3–28.2°
b = 10.5115 (4) Å	µ = 0.33 mm⁻¹
c = 17.3105 (6) Å	T = 200 K
V = 807.54 (6) Å³	Rod, brown
Z = 4	0.52 × 0.20 × 0.20 mm
F(000) = 344

Data collection top

Bruker APEXII CCD diffractometer	1757 reflections with I > 2σ(I)
φ and ω scans	R_int = 0.062
Absorption correction: multi-scan (SADABS; Krause et al., 2015)	θ_max = 28.3°, θ_min = 2.3°
T_min = 0.673, T_max = 0.746	h = −5→5
26844 measured reflections	k = −12→14
1996 independent reflections	l = −23→21

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: mixed
R[F² > 2σ(F²)] = 0.043	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.075	w = 1/[σ²(F_o²) + (0.0132P)² + 0.3653P] where P = (F_o² + 2F_c²)/3
S = 1.16	(Δ/σ)_max < 0.001
1996 reflections	Δρ_max = 0.26 e Å⁻³
109 parameters	Δρ_min = −0.22 e Å⁻³
0 restraints	Absolute structure: Flack x determined using 628 quotients [(I⁺)-(I^-)]/[(I⁺)+(I^-)] (Parsons et al., 2013)
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.00 (4)

Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Refinement. The carbon-bound aromatic H atoms were placed in calculated positions (C–H 0.95 Å) and were included in the refinement in the riding model approximation, with U(H) set to 1.2U_eq(C).

The H atoms of the methyl group were allowed to rotate with a fixed angle around the C–C bond to best fit the experimental electron density [HFIX 137 in the SHELX program suite (Sheldrick, 2015)], with U(H) set to 1.5U_eq(C).

Both nitrogen-bound H atoms were located on a difference Fourier map and refined freely.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
S1	−0.06454 (16)	0.57399 (7)	0.80755 (4)	0.0388 (2)
N1	0.3355 (6)	0.5337 (2)	0.93268 (14)	0.0486 (7)
N2	0.7653 (6)	0.6435 (3)	0.54134 (14)	0.0391 (6)
C1	0.1997 (6)	0.5930 (3)	0.73078 (13)	0.0286 (6)
C2	0.3097 (5)	0.4881 (2)	0.69152 (15)	0.0282 (5)
H2	0.250656	0.405369	0.707623	0.034*
C3	0.5039 (6)	0.5008 (2)	0.62927 (13)	0.0274 (6)
C4	0.5861 (6)	0.6245 (2)	0.60565 (13)	0.0286 (5)
C5	0.4736 (7)	0.7295 (2)	0.64576 (15)	0.0336 (6)
H5	0.530092	0.812751	0.630098	0.040*
C6	0.2820 (6)	0.7142 (2)	0.70775 (15)	0.0317 (6)
H6	0.206848	0.786480	0.734497	0.038*
C7	0.1766 (7)	0.5506 (3)	0.88190 (15)	0.0325 (6)
C8	0.6234 (7)	0.3849 (2)	0.58817 (15)	0.0379 (7)
H8A	0.557026	0.386128	0.534182	0.057*
H8B	0.546710	0.308023	0.613493	0.057*
H8C	0.844074	0.385071	0.590133	0.057*
H2A	0.863 (7)	0.717 (3)	0.5391 (15)	0.035 (8)*
H2B	0.871 (8)	0.582 (3)	0.5241 (18)	0.056 (11)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
S1	0.0252 (3)	0.0540 (4)	0.0371 (3)	−0.0004 (4)	0.0033 (3)	0.0012 (3)
N1	0.0567 (18)	0.0541 (17)	0.0351 (13)	0.0112 (13)	0.0007 (13)	0.0003 (12)
N2	0.0423 (16)	0.0395 (15)	0.0354 (13)	−0.0051 (14)	0.0050 (12)	0.0018 (12)
C1	0.0215 (12)	0.0395 (15)	0.0248 (11)	0.0005 (12)	−0.0015 (10)	0.0024 (11)
C2	0.0255 (12)	0.0279 (12)	0.0312 (12)	−0.0029 (10)	−0.0081 (12)	0.0039 (11)
C3	0.0271 (15)	0.0290 (13)	0.0260 (12)	0.0010 (11)	−0.0064 (10)	0.0010 (10)
C4	0.0266 (13)	0.0355 (13)	0.0237 (11)	−0.0002 (12)	−0.0063 (11)	0.0038 (10)
C5	0.0386 (17)	0.0264 (13)	0.0359 (14)	−0.0046 (12)	−0.0050 (13)	0.0048 (11)
C6	0.0316 (14)	0.0302 (13)	0.0334 (14)	0.0045 (12)	−0.0046 (12)	−0.0018 (11)
C7	0.0358 (15)	0.0305 (14)	0.0312 (13)	0.0041 (12)	0.0092 (12)	−0.0012 (11)
C8	0.0453 (18)	0.0353 (15)	0.0331 (14)	0.0059 (13)	−0.0039 (13)	−0.0021 (11)

Geometric parameters (Å, º) top

S1—C7	1.692 (3)	C3—C4	1.411 (3)
S1—C1	1.784 (3)	C3—C8	1.508 (4)
N1—C7	1.141 (4)	C4—C5	1.396 (4)
N2—C4	1.383 (3)	C5—C6	1.379 (4)
N2—H2A	0.89 (3)	C5—H5	0.9500
N2—H2B	0.85 (4)	C6—H6	0.9500
C1—C6	1.384 (4)	C8—H8A	0.9800
C1—C2	1.384 (4)	C8—H8B	0.9800
C2—C3	1.387 (4)	C8—H8C	0.9800
C2—H2	0.9500

C7—S1—C1	99.62 (12)	C5—C4—C3	119.5 (2)
C4—N2—H2A	116.2 (18)	C6—C5—C4	121.0 (2)
C4—N2—H2B	119 (2)	C6—C5—H5	119.5
H2A—N2—H2B	112 (3)	C4—C5—H5	119.5
C6—C1—C2	119.9 (2)	C5—C6—C1	119.6 (2)
C6—C1—S1	119.4 (2)	C5—C6—H6	120.2
C2—C1—S1	120.6 (2)	C1—C6—H6	120.2
C1—C2—C3	121.6 (2)	N1—C7—S1	178.8 (3)
C1—C2—H2	119.2	C3—C8—H8A	109.5
C3—C2—H2	119.2	C3—C8—H8B	109.5
C2—C3—C4	118.4 (2)	H8A—C8—H8B	109.5
C2—C3—C8	120.5 (2)	C3—C8—H8C	109.5
C4—C3—C8	121.2 (2)	H8A—C8—H8C	109.5
N2—C4—C5	119.5 (2)	H8B—C8—H8C	109.5
N2—C4—C3	121.0 (2)

C7—S1—C1—C6	−96.9 (2)	C2—C3—C4—C5	0.8 (4)
C7—S1—C1—C2	86.6 (2)	C8—C3—C4—C5	−179.2 (2)
C6—C1—C2—C3	0.4 (4)	N2—C4—C5—C6	176.7 (3)
S1—C1—C2—C3	176.84 (18)	C3—C4—C5—C6	−0.4 (4)
C1—C2—C3—C4	−0.8 (4)	C4—C5—C6—C1	0.1 (4)
C1—C2—C3—C8	179.2 (2)	C2—C1—C6—C5	−0.1 (4)
C2—C3—C4—N2	−176.3 (2)	S1—C1—C6—C5	−176.5 (2)
C8—C3—C4—N2	3.7 (4)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C8—H8A···N1ⁱ	0.98	2.61	3.482 (4)	148
C5—H5···N1ⁱⁱ	0.95	2.63	3.576 (3)	172
N2—H2B···N1ⁱⁱⁱ	0.85 (4)	2.38 (4)	3.185 (4)	157 (3)

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

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