Bis(N,N-di­methyl­thio­carbamoyl­thio)­acetic acid

Bis(N,N-di­methyl­thio­carbamoyl­thio)­acetic acid, [(CH₃)₂NC(=S)S]₂CHC(=O)OH or C₈H₁₄N₂O₂S₄, exists as a centrosymmetric hydrogen-bonded dimer [O...O 2.661 (3) Å].

S1. Comment

The thiocarbamoylthioacetic acids, R₂NC(S)SCH₂C(O)OH, are plant growth-regulating compounds (Fawcett et al., 1956; van der Kerk et al., 1955) that are readily synthesized by diplacing the chloride of chloroacetic acid by the dithiocarbamato nucleophile (Nachmias, 1952). Their acid dissociation constants (Janssen, 1963) are been explained in terms of extensive mesomeric electron displacements of the thiocarbonyl group; the R₂NC(S)S portion also exerts an appreciable electron-withdrawing effect (Janssen, 1993). The analogous [(R₂NC(S)S]₂CHC(O)OH acid is known only for the R = CH₃ homolog as other homologs cannot be synthesized by the reaction of the dithiocarbamate ion with dichloroacetic acid (Pluijgers, 1959). The title compound, (I), crystallizes as a centrosymmetric dimer that is held together by a short hydrogen bond [O···O 2.664 (3) Å]. Bond dimensions in the acid are similar to those found in the dicyclohexylammonium (Ng, 1996) and tetramethylammonium (Ng, 1997) salts. The tetramethylammonium salt crystallizes with a molecule of the acid, and the carboxylate and acid moieties are linked across a center of inversion by the acid hydrogen atom [O···O 2.486 (3) Å].

An examination of the bond dimensions found in [(CH₃)₂NC(S)S]₂CHC(O)OH acid does not suggest any particularly abnormal values. The bond dimensions that are calculated by the GAUSSIAN suite (Frisch et al., 1995) compare well with those found experimentally. Similar calculations were also performed on [(C₂H₅)₂NC(S)S]₂CHC(O)OH to ascertain why this and other homologs could not be isolated. The calculations, which used the same model chemistry (HF/3–21 G), gave insignificant differences, other than for somewhat longer carbon-sulfur double-bonds, i.e. this acid should be thermodynamically stable.

S2. Experimental

The title acid was synthesized from dimethylamine, carbon disulfide and dichloroacetic acid (Nachmias, 1952; Pluijgers & van der Kerk, 1961), and crystals were obtained upon recrystallization of the compound from ethanol.

Computing details

Data collection: SMART (Siemens, 1996); cell refinement: SAINT (Siemens, 1996); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); software used to prepare material for publication: SHELXL97.

Bis(N,N-dimethylthiocarbamoylthio)acetic acid

Crystal data

C8H14N2O2S4	Z = 2
Mr = 298.45	F(000) = 312
Triclinic, P1	Dx = 1.422 Mg m^−3
a = 7.3275 (1) Å	Mo Kα radiation, λ = 0.71073 Å
b = 7.6321 (2) Å	Cell parameters from 3176 reflections
c = 12.6379 (4) Å	θ = 2.8–28.3°
α = 95.809 (2)°	µ = 0.67 mm^−1
β = 96.991 (1)°	T = 293 K
γ = 92.244 (2)°	Block, faint tan
V = 696.96 (3) Å^3	0.38 × 0.30 × 0.16 mm

Data collection

Siemens CCD area-detector diffractometer	3349 independent reflections
Radiation source: fine-focus sealed tube	2292 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.037
w scans	θmax = 28.3°, θmin = 2.8°
Absorption correction: empirical (using intensity measurements) (SADABS; Sheldrick, 1996)	h = −9→9
Tmin = 0.785, Tmax = 0.900	k = −10→10
5032 measured reflections	l = −16→9

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)] = 0.053	H-atom parameters constrained
wR(F^2) = 0.139	w = 1/[σ^2(Fo^2) + (0.0705P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 0.95	(Δ/σ)max = 0.001
3349 reflections	Δρmax = 0.38 e Å^−3
151 parameters	Δρmin = −0.39 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.030 (5)

Special details

Refinement. The methyl hydrogen atoms of the C4 and C8 atoms are ordered whereas those of the C5 and C7 atoms are disordered. The ordered methyl H-atoms were generated by the HFIX 137 instruction in SHELXL97 whereas the disordered methyl H-atoms were generated by the HFIX 127 instruction.

H atoms: Riding, U(H) = 1.5U_eq(C,O).

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
S1	−0.0060 (1)	0.2538 (1)	0.3109 (1)	0.0517 (2)
S2	0.3044 (1)	0.1845 (1)	0.4813 (1)	0.0636 (3)
S3	0.2905 (1)	0.4414 (1)	0.2313 (1)	0.0544 (2)
S4	0.5407 (1)	0.1898 (1)	0.1304 (1)	0.0597 (2)
O1	0.1057 (3)	−0.0461 (3)	0.1337 (2)	0.0634 (6)
O2	0.0615 (3)	0.2001 (2)	0.0532 (2)	0.0523 (5)
N1	−0.0383 (3)	0.2527 (3)	0.5128 (2)	0.0500 (5)
N2	0.5852 (3)	0.5398 (3)	0.1519 (2)	0.0507 (5)
C1	0.1159 (4)	0.1255 (3)	0.1306 (2)	0.0485 (6)
C2	0.1925 (4)	0.2240 (4)	0.2395 (2)	0.0483 (6)
C3	0.0881 (3)	0.2305 (3)	0.4459 (2)	0.0427 (5)
C4	0.0113 (5)	0.2351 (5)	0.6271 (2)	0.0657 (8)
C5	−0.2290 (4)	0.2925 (5)	0.4792 (3)	0.0635 (8)
C6	0.4895 (3)	0.3954 (3)	0.1670 (2)	0.0446 (6)
C7	0.7504 (4)	0.5278 (4)	0.0974 (3)	0.0649 (8)
C8	0.5317 (5)	0.7183 (4)	0.1834 (3)	0.0715 (9)
H1	0.0568	−0.0942	0.0757	0.095*
H2	0.2822	0.1538	0.2781	0.073*
H4a	0.0857	0.1353	0.6349	0.099*
H4b	−0.0986	0.2185	0.6600	0.099*
H4c	0.0794	0.3400	0.6612	0.099*
H5a	−0.2969	0.2960	0.5397	0.095*	0.50
H5b	−0.2840	0.2027	0.4247	0.095*	0.50
H5c	−0.2314	0.4048	0.4512	0.095*	0.50
H5d	−0.2446	0.3063	0.4041	0.095*	0.50
H5e	−0.2575	0.3996	0.5191	0.095*	0.50
H5f	−0.3101	0.1975	0.4926	0.095*	0.50
H7a	0.7724	0.6358	0.0670	0.097*	0.50
H7b	0.7328	0.4316	0.0414	0.097*	0.50
H7c	0.8542	0.5080	0.1481	0.097*	0.50
H7d	0.8006	0.4145	0.1040	0.097*	0.50
H7e	0.8401	0.6187	0.1296	0.097*	0.50
H7f	0.7187	0.5422	0.0229	0.097*	0.50
H8a	0.4165	0.7388	0.1428	0.107*
H8b	0.6246	0.8023	0.1698	0.107*
H8c	0.5188	0.7309	0.2585	0.107*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
S1	0.0398 (3)	0.0707 (5)	0.0457 (4)	0.0024 (3)	0.0047 (3)	0.0136 (3)
S2	0.0401 (4)	0.0909 (6)	0.0591 (5)	0.0045 (3)	−0.0016 (3)	0.0133 (4)
S3	0.0554 (4)	0.0492 (4)	0.0588 (5)	−0.0050 (3)	0.0178 (3)	−0.0036 (3)
S4	0.0541 (4)	0.0528 (4)	0.0739 (5)	0.0055 (3)	0.0150 (4)	0.0059 (4)
O1	0.087 (2)	0.046 (1)	0.054 (1)	−0.010 (1)	−0.001 (1)	0.010 (1)
O2	0.061 (1)	0.048 (1)	0.048 (1)	−0.005 (1)	0.004 (1)	0.010 (1)
N1	0.047 (1)	0.057 (1)	0.047 (1)	−0.001 (1)	0.011 (1)	0.006 (1)
N2	0.049 (1)	0.050 (1)	0.054 (1)	−0.005 (1)	0.004 (1)	0.014 (1)
C1	0.052 (2)	0.046 (1)	0.049 (2)	−0.006 (1)	0.011 (1)	0.008 (1)
C2	0.048 (1)	0.051 (1)	0.046 (1)	−0.004 (1)	0.011 (1)	0.006 (1)
C3	0.041 (1)	0.044 (1)	0.041 (1)	−0.005 (1)	0.002 (1)	0.005 (1)
C4	0.081 (2)	0.071 (2)	0.046 (2)	0.000 (2)	0.015 (2)	0.006 (2)
C5	0.045 (2)	0.078 (2)	0.071 (2)	0.006 (1)	0.019 (1)	0.008 (2)
C6	0.043 (1)	0.050 (1)	0.040 (1)	−0.002 (1)	0.001 (1)	0.008 (1)
C7	0.052 (2)	0.082 (2)	0.065 (2)	−0.007 (2)	0.009 (2)	0.027 (2)
C8	0.074 (2)	0.053 (2)	0.086 (3)	−0.008 (2)	0.007 (2)	0.012 (2)

Geometric parameters (Å, º)

S1—C3	1.790 (3)	C4—H4b	0.9600
S1—C2	1.812 (3)	C4—H4c	0.9600
S2—C3	1.655 (3)	C5—H5a	0.9600
S3—C6	1.783 (3)	C5—H5b	0.9600
S3—C2	1.799 (3)	C5—H5c	0.9600
S4—C6	1.661 (3)	C5—H5d	0.9600
O1—C1	1.313 (3)	C5—H5e	0.9600
O2—C1	1.214 (3)	C5—H5f	0.9600
N1—C3	1.332 (3)	C7—H7a	0.9600
N1—C5	1.463 (4)	C7—H7b	0.9600
N1—C4	1.467 (4)	C7—H7c	0.9600
N2—C6	1.326 (3)	C7—H7d	0.9600
N2—C8	1.462 (4)	C7—H7e	0.9600
N2—C7	1.465 (3)	C7—H7f	0.9600
C1—C2	1.531 (4)	C8—H8a	0.9600
O1—H1	0.8200	C8—H8b	0.9600
C2—H2	0.9800	C8—H8c	0.9600
C4—H4a	0.9600
C3—S1—C2	102.2 (1)	N1—C5—H5b	109.5
C6—S3—C2	102.4 (1)	H5a—C5—H5b	109.5
C3—N1—C5	123.8 (2)	N1—C5—H5c	109.5
C3—N1—C4	119.7 (2)	H5a—C5—H5c	109.5
C5—N1—C4	116.5 (2)	H5b—C5—H5c	109.5
C6—N2—C8	123.4 (2)	N1—C5—H5d	109.5
C6—N2—C7	120.7 (2)	H5a—C5—H5d	141.1
C8—N2—C7	115.8 (2)	N1—C5—H5e	109.5
O2—C1—O1	124.9 (3)	H5d—C5—H5e	109.5
O2—C1—C2	123.0 (2)	N1—C5—H5f	109.5
O1—C1—C2	112.0 (2)	H5d—C5—H5f	109.5
C1—C2—S3	113.9 (2)	H5e—C5—H5f	109.5
C1—C2—S1	105.0 (2)	N2—C7—H7a	109.5
S3—C2—S1	106.4 (1)	N2—C7—H7b	109.5
N1—C3—S2	124.9 (2)	H7a—C7—H7b	109.5
N1—C3—S1	111.4 (2)	N2—C7—H7c	109.5
S2—C3—S1	123.7 (2)	H7a—C7—H7c	109.5
N2—C6—S4	125.6 (2)	H7b—C7—H7c	109.5
N2—C6—S3	113.0 (2)	N2—C7—H7d	109.5
S4—C6—S3	121.4 (1)	N2—C7—H7e	109.5
C1—C2—H2	110.5	H7d—C7—H7e	109.5
S3—C2—H2	110.5	N2—C7—H7f	109.5
S1—C2—H2	110.5	H7d—C7—H7f	109.5
C1—O1—H1	109.5	H7e—C7—H7f	109.5
N1—C4—H4a	109.5	N2—C8—H8a	109.5
N1—C4—H4b	109.5	N2—C8—H8b	109.5
H4a—C4—H4b	109.5	H8a—C8—H8b	109.5
N1—C4—H4c	109.5	N2—C8—H8c	109.5
H4a—C4—H4c	109.5	H8a—C8—H8c	109.5
H4b—C4—H4c	109.5	H8b—C8—H8c	109.5
N1—C5—H5a	109.5
O2—C1—C2—S3	−26.4 (3)	C5—N1—C3—S1	−0.5 (3)
O1—C1—C2—S3	157.7 (2)	C4—N1—C3—S1	178.8 (2)
O2—C1—C2—S1	89.6 (3)	C2—S1—C3—N1	178.5 (2)
O1—C1—C2—S1	−86.3 (2)	C2—S1—C3—S2	−2.3 (2)
C6—S3—C2—C1	−68.0 (2)	C8—N2—C6—S4	178.5 (2)
C6—S3—C2—S1	176.9 (1)	C7—N2—C6—S4	0.9 (4)
C3—S1—C2—C1	144.2 (2)	C8—N2—C6—S3	−0.7 (4)
C3—S1—C2—S3	−94.8 (2)	C7—N2—C6—S3	−178.3 (2)
C5—N1—C3—S2	−179.7 (2)	C2—S3—C6—N2	179.7 (2)
C4—N1—C3—S2	−0.4 (4)	C2—S3—C6—S4	0.5 (2)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···O2^i	0.82	1.84	2.661 (3)	178

Symmetry code: (i) −x, −y, −z.