Bis(N-methyl-N-phenyl­carbamo­yl)disulfane

The title compound, C₁₆H₁₆N₂O₂S₂, has been synthesized by several different high-yield routes, and has been encountered as a co-product in a number of reaction pathways, ever since it became of inter­est to our research program over 30 years ago. We now confirm the proposed mol­ecular structure in which the mol­ecule exhibits a twofold axis of symmetry through the mid-point of the S—S bond and the two planes defined by the (carbamo­yl)sulfenyl moieties are essentially perpendicular to each other [dihedral angle = 81.55 (14)°].

Key indicators

• Single-crystal X-ray study
• T = 296 K
• Mean [sigma](C-C) = 0.004 Å
• R factor = 0.037
• wR factor = 0.110
• Data-to-parameter ratio = 14.5

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S1. Comment

Bis(N-methyl-N-phenylcarbamoyl)disulfane (C₁₆H₁₆N₂O₂S₂) was first reported by Kobayashi et al. (1973). The compound became of interest to our research program over thirty years ago (Barany et al., 1983; Schroll and Barany, 1986) and has been synthesized by several different high-yield routes, as well as encountered as a co-product in a number of reaction pathways (Barany et al., 1983; Schroll and Barany, 1986; Schrader et al., 2011). We now confirm the molecular structure of the title compound by single-crystal X-ray analysis. The disulfane reported herein is the flagship of the homologous series of bis(N-methyl-N-phenylcarbamoyl)polysulfanes, C₁₆H₁₆N₂O₂S_n , which have been prepared and structurally characterized for n = 1–6.

The title compound exhibits a twofold axis of symmetry through the center of the S–S bond, and all bond distances and angles are within expected ranges. The N–C bond distance is 1.35 Å, consistent with ~60% double bond character, with the consequence that the (carbamoyl)sulfenyl atoms (S1,C1,O1,N1,C2,C3) are in a plane. The aromatic ring is nearly perpendicular to the (carbamoyl)sulfenyl plane, with a torsion angle of 92.5° (C2–N1–C3–C4). The S–S bond length of 2.03 Å is slightly shorter than the 2.07 Å reported for the S–S bond length in elemental sulfur (S₈), suggesting that some partial double bond character extends through the S–S bond due to its adjacency to carbonyl groups on both sides. Several other reference compounds also have an S–S bond length of 2.01–2.03 Å (Bereman et al., 1983; Rout et al., 1983; Paul and Srikrishnan, 2004; Fun et al., 2001; Raya et al., 2005; Li et al., 2006; Singh et al., 2011). The most noteworthy feature of the title compound is the torsion angle about the disulfane, which is 81.6° and as such is somewhat smaller than the theoretical optimum of 90.0° (Pauling, 1949; Torrico-Vallejos et al., 2010) that has been explained as allowing for minimal mutual repulsion of pπ orbital electron lone pairs in sulfur. A comparable deviation from theory was reported for dibenzoyl disulfide (Rout et al., 1983; Paul & Srikrishnan, 2004), where the torsion angle is 80.8°. Bis(N-methyl-N-phenylthiocarbamoyl)disulfane, which only differs from the title compound by two thiocarbonyls in place of two carbonyls, has a torsion angle about the disulfane of 89.8° and shows a conformation that is not completely superimposable on the title compound (Fun et al., 2001).

Note regarding nomenclature: The title compound is named in a manner that is consistent with our prior publications. The closely related C₁₆H₁₆N₂S₄ was named bis(N-methyl-N-phenylthiocarbamoyl) disulfide by Fun et al. (2001), but we have chosen the "disulfane" revised name for consistency.

Table 1 Selected geometric parameters (Å, °)

N1–C1 1.345 (3)

N1–C2 1.461 (3)

N1–C3 1.442 (2)

C1–O1 1.209 (2)

C1–S1 1.825 (2)

S1–S1 2.0262 (11)

C2–N1–C3–C4 92.5 (3)

C1–S1–S1–C1 81.55 (14)

Symmetry operator (a): -x + 1, y, -z + 1/2

Related literature

For the preparation of the title compound, and of very closely related chemical structures, see: Kobayashi et al. (1973); Barany et al. (1983); Schroll & Barany (1986); Schrader et al. (2011). For related structures, see: CSD refcodes BOWGAV (Bereman et al., 1983), DBZOSS01&03 (Rout et al., 1983; Paul & Srikrishnan, 2004), METHUS03 (Wang & Liao, 1989), NELTUT (Fun et al., 2001), JAXPOO (Raya et al., 2005), UDALER (Li et al., 2006) and EMASIV (Singh et al., 2011). For the theoretical optimum torsion angle about the disulfane, see: Pauling (1949); Torrico-Vallejos et al. (2010) and references cited therein. For values in dibenzoyl disulfide, see: Rout et al. (1983); Paul & Srikrishnan (2004).

S2. Experimental

The title compound was prepared in high yield from the reaction of N-methylaniline with bis(chlorocarbonyl)disulfane, and recrystallized from hot carbon tetrachloride/chloroform (3:2) in 60–85% recovery or from hot acetone in 75% recovery (Barany et al., 1983).

S3. Refinement

H atoms were positioned geometrically and refined using a riding model with C—H = 0.93 Å (aromatic) or 0.96 Å (methyl), and U_iso(H) = 1.2U_eq(C) for aromatic and 1.5U_eq(C) for methyl H atoms.

Computing details

Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT (Bruker, 2001); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures

Fig. 1. Crystallographic structure of the title compound showing 50% probability displacement ellipsoids and with all non-hydrogen atoms labelled and numbered.

Bis(N-methyl-N-phenylcarbamoyl)disulfane

Crystal data

C16H16N2O2S2	F(000) = 696
Mr = 332.43	Dx = 1.334 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
a = 15.286 (3) Å	Cell parameters from 1966 reflections
b = 9.7849 (18) Å	θ = 2.5–24.4°
c = 11.597 (2) Å	µ = 0.33 mm^−1
β = 107.433 (3)°	T = 296 K
V = 1654.9 (5) Å^3	Needle, colorless
Z = 4	0.40 × 0.16 × 0.13 mm

Data collection

Bruker SMART CCD diffractometer	1468 independent reflections
Radiation source: sealed tube	1140 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.031
φ and ω scans	θmax = 25.1°, θmin = 2.5°
Absorption correction: multi-scan (SADABS; Bruker, 2010)	h = −18→17
Tmin = 0.880, Tmax = 0.958	k = 0→11
5726 measured reflections	l = 0→13

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.037	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.110	H-atom parameters constrained
S = 1.05	w = 1/[σ^2(Fo^2) + (0.0553P)^2 + 1.0043P] where P = (Fo^2 + 2Fc^2)/3
1468 reflections	(Δ/σ)max = 0.001
101 parameters	Δρmax = 0.21 e Å^−3
0 restraints	Δρmin = −0.18 e Å^−3

Special details

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 > 2σ(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	0.56058 (4)	0.49722 (6)	0.73116 (5)	0.0567 (2)
O1	0.47025 (9)	0.69997 (17)	0.58995 (15)	0.0626 (5)
N1	0.61329 (11)	0.65722 (19)	0.57979 (17)	0.0514 (5)
C1	0.54116 (13)	0.6361 (2)	0.62131 (19)	0.0481 (5)
C2	0.60771 (17)	0.7649 (3)	0.4905 (2)	0.0697 (7)
H2A	0.5446	0.7887	0.4530	0.105*
H2B	0.6341	0.7328	0.4301	0.105*
H2C	0.6407	0.8438	0.5298	0.105*
C3	0.69962 (13)	0.5872 (2)	0.62742 (19)	0.0466 (5)
C4	0.76230 (16)	0.6332 (3)	0.7319 (2)	0.0681 (7)
H4A	0.7486	0.7071	0.7739	0.082*
C5	0.84668 (17)	0.5672 (4)	0.7739 (3)	0.0852 (9)
H5A	0.8893	0.5962	0.8451	0.102*
C6	0.86714 (18)	0.4597 (3)	0.7107 (3)	0.0806 (9)
H6A	0.9235	0.4159	0.7393	0.097*
C7	0.80540 (18)	0.4168 (3)	0.6063 (3)	0.0716 (7)
H7A	0.8202	0.3449	0.5631	0.086*
C8	0.72070 (16)	0.4796 (2)	0.5640 (2)	0.0562 (6)
H8A	0.6782	0.4493	0.4932	0.067*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
S1	0.0465 (3)	0.0663 (4)	0.0681 (4)	0.0096 (3)	0.0337 (3)	0.0104 (3)
O1	0.0407 (8)	0.0691 (10)	0.0836 (12)	0.0153 (7)	0.0269 (8)	0.0072 (8)
N1	0.0395 (9)	0.0581 (11)	0.0632 (11)	0.0094 (8)	0.0255 (8)	0.0135 (9)
C1	0.0387 (11)	0.0530 (12)	0.0566 (13)	0.0036 (9)	0.0205 (9)	−0.0051 (10)
C2	0.0644 (15)	0.0712 (16)	0.0834 (18)	0.0110 (13)	0.0370 (14)	0.0239 (14)
C3	0.0349 (10)	0.0546 (12)	0.0573 (13)	0.0039 (9)	0.0244 (9)	0.0078 (10)
C4	0.0496 (13)	0.0865 (18)	0.0723 (16)	0.0010 (13)	0.0244 (12)	−0.0099 (14)
C5	0.0468 (14)	0.120 (3)	0.0796 (19)	−0.0082 (16)	0.0043 (13)	0.0141 (19)
C6	0.0438 (14)	0.092 (2)	0.114 (2)	0.0204 (14)	0.0361 (16)	0.0376 (19)
C7	0.0624 (15)	0.0610 (15)	0.105 (2)	0.0186 (13)	0.0467 (16)	0.0171 (15)
C8	0.0508 (13)	0.0567 (14)	0.0675 (14)	0.0032 (10)	0.0274 (11)	0.0033 (11)

Geometric parameters (Å, º)

S1—O1^i	3.0078 (18)	C3—C8	1.377 (3)
S1—C1	1.825 (2)	C4—C5	1.393 (4)
S1—S1^i	2.0262 (11)	C4—H4A	0.9300
O1—C1	1.209 (2)	C5—C6	1.371 (4)
N1—C1	1.345 (3)	C5—H5A	0.9300
N1—C3	1.442 (2)	C6—C7	1.359 (4)
N1—C2	1.461 (3)	C6—H6A	0.9300
C2—H2A	0.9600	C7—C8	1.384 (3)
C2—H2B	0.9600	C7—H7A	0.9300
C2—H2C	0.9600	C8—H8A	0.9300
C3—C4	1.376 (3)
C1—S1—S1^i	100.51 (7)	C3—C4—C5	118.9 (3)
C1—N1—C3	122.98 (17)	C3—C4—H4A	120.5
C1—N1—C2	118.97 (17)	C5—C4—H4A	120.5
C3—N1—C2	117.79 (17)	C6—C5—C4	120.3 (3)
O1—C1—N1	124.8 (2)	C6—C5—H5A	119.8
O1—C1—S1	122.58 (16)	C4—C5—H5A	119.8
N1—C1—S1	112.64 (14)	C7—C6—C5	120.3 (2)
N1—C2—H2A	109.5	C7—C6—H6A	119.8
N1—C2—H2B	109.5	C5—C6—H6A	119.8
H2A—C2—H2B	109.5	C6—C7—C8	120.3 (3)
N1—C2—H2C	109.5	C6—C7—H7A	119.8
H2A—C2—H2C	109.5	C8—C7—H7A	119.8
H2B—C2—H2C	109.5	C3—C8—C7	119.6 (2)
C4—C3—C8	120.5 (2)	C3—C8—H8A	120.2
C4—C3—N1	119.9 (2)	C7—C8—H8A	120.2
C8—C3—N1	119.5 (2)
C3—N1—C1—O1	174.2 (2)	C8—C3—C4—C5	−1.3 (4)
C2—N1—C1—O1	0.2 (3)	N1—C3—C4—C5	−177.6 (2)
C3—N1—C1—S1	−6.4 (3)	C3—C4—C5—C6	1.0 (4)
C2—N1—C1—S1	179.66 (17)	C4—C5—C6—C7	0.2 (4)
S1^i—S1—C1—O1	−0.1 (2)	C5—C6—C7—C8	−1.2 (4)
S1^i—S1—C1—N1	−179.48 (15)	C4—C3—C8—C7	0.4 (3)
C1—N1—C3—C4	−81.5 (3)	N1—C3—C8—C7	176.7 (2)
C2—N1—C3—C4	92.5 (3)	C6—C7—C8—C3	0.9 (4)
C1—N1—C3—C8	102.2 (3)	C1—S1—S1^i—C1^i	−81.55 (14)
C2—N1—C3—C8	−83.8 (3)

Symmetry code: (i) −x+1, y, −z+3/2.