Bis(tert-butyl­sulfonyl)ethyne and 1-tert-butyl­sulfinyl-2-tert-butyl­sulfonyl­ethyne

The title compounds are electron-poor ethynes. The structure determination of bis­(tert-butyl­sulfonyl)ethyne, C₁₀H₁₈O₄S₂, (I), is the first of a bis-sulfonyl-substituted ethyne. The mol­ecule is situated on a crystallographic inversion centre. The S-Csp bond [1.737 (2) Å] is the longest of this type reported to date. 1-tert-Butyl­sulfinyl-2-tert-butylsulfonyl­ethyne, C₁₀H₁₈O₃S₂, (II), which is basically the same as (I) minus one O atom, crystallizes isomorphous with (I). This results in a nearly equal distribution of the three O atoms over the four possible positions.

S1. Comment

The high reactivity of bis(tert-butylsulfonyl)ethyne, (I), as a dienophile in Diels–Alder reactions has been demonstrated in several reports (Riera et al., 1990; Virgili et al., 1991; Gleiter & Ohlbach, 1994; Gleiter et al., 1996). Compound (I) is the only known stable ethyne substituted by two sulfonyl groups, whereas bis(arylsulfonyl)ethynes are reported as unstable at room temperature (Pasquato et al., 1991).

Compound (I) forms colourless polyhedral crystals and crystallizes in the monoclinic space group P2₁/c. Crystallographically imposed inversion symmetry was found in the structure of (I). Thus, there is only half a molecule in the asymmetric unit. This structure determination is the first to be reported of an uncomplexed bis-sulfonyl-substituted ethyne. Structures of mono-sulfonyl-substituted ethynes are also very rare (Hu et al., 2004; Tykwinski et al., 1993), so there is very little knowledge of the geometric parameters of such compounds. The C≡C triple bond is rather short (1.194 Å), whereas the sulfonyl SO₂—Csp bond is the longest of this type reported to date.

It is interesting to note that all sulfonyl SO₂—Csp bonds known in the literature [1.707 Å (Hu et al., 2004), 1.711 Å (Tykwinski et al., 1993) and 1.737 Å (present work)] are significantly longer than reported sulfide S—Csp bonds (mean 1.681 Å, SE standard error? = 0.001, standard deviation = 0.013; Cambridge Structural Database, Version?; Allen, 2002). This observation was confirmed by the determination and investigation of the structure of a mixed sulfonyl–thio compound, tert-butylsulfonyl-tert-butylthioethyne, (III) (Werz et al., 2006), which continues the series of (I) and (II), with another O atom absent at the same site. In that compound, the SO₂—Csp bond is also longer than the S—Csp bond [1.697 (2) and 1.684 (3) Å, respectively]. In the case of saturated sp³ C atoms, this is not the case: in contrast, the sulfonyl SO₂—Csp³ bonds have a mean length of 1.788 Å (standard error? = 0.001, standard deviation = 0.024), which is significantly shorter than the sulfide S—Csp³ bonds, with a mean length of 1.812 Å (standard error? = 0.001, standard deviation = 0.024) (Allen, 2002).

The bond angles at the S atom of (I) are as expected. The smallest angle is Csp³—S—Csp (Value?) and the largest is O═S═ O (Value?). The O═S—C angles are within this range, with the O═S—Csp angles being smaller than the O═S—Csp³ angles.

Due to the symmetry of the molecule of (I), the torsion angle tert-butyl—SO₂—SO₂—tert-butyl is exactly 180°. In contrast, in the mixed compound (III) (Werz et al., 2006), the torsion tert-butyl—SO₂—S—tert-butyl is nearly perfectly orthogonal (91.5°). We assume electronic rather than steric reasons. Further examinations are in progress.

The sulfonyl–sulfinyl compound 1-tert-butylsulfonyl-2-tert-butylsulfinylethyne, (II), with its three O atoms, is in the middle of the series between compounds (I) and (III). It crystallizes isomorphous with (I), which results in a nearly equal distribution of the three O atoms over the four possible positions. From an analytical point of view (chromatography, NMR, FAB mass spectrometry; see Experimental), it is already inherently clear that there can only be three O atoms, which means that in the asymmetric unit the sum of the occupancies of the two oxygen atoms must add to 1.5. The disorder of the O atoms leads to a somewhat restricted quality of the structure compared with (I) and thus prevents a detailed quantitative discussion of the results. Because of the disorder, the torsion angle tert-butyl—SO₂—SO—tert-butyl is exactly 180°, and thus compound (II) is much more similar to (I) than to (III) (Werz et al., 2006).

S2. Experimental

Compound (I) was obtained from bis(tert-butylthio)ethyne by oxidation with chloroperbenzoic acid (Riera et al., 1990). It was recrystallized from what solvent? The preparation of (II) was carried out as follows. tert-Butylsulfonyl-tert-butylthioethyne, (III) (Werz et al., 2006) (1.0 equivalent) was dissolved in chloroform and petroleum ether (4:1, v/v). The mixture was cooled to 273 K and a solution of m-CPBA (0.9 equivalents) in chloroform was added slowly. The mixture was stirred for 2 d while warming to room temperature. After 2 d, the mixture was cooled to 273 K and filtered. The filtrate was washed three times with Na₂S₂O₃ solution and then three times with NaHCO₃ solution. The organic phase was dried over Na₂SO₄ and concentrated. Silica-gel column chromatography yielded the desired compound in pure form as the major product (64%), with compound (I) as a by-product. The two compounds could be easily distinguished by thin-layer chromatography. The structure of (II) was assigned unequivocally by NMR and mass spectrometric analyses: ¹H NMR (500 MHz, CDCl₃, δ, p.p.m.): 1.45 (s, 9H), 1.49 (s, 9H); ¹³C NMR (125 MHz, CHCl₃, δ, p.p.m.): 22.9 (CH₃), 23.3 (CH₃), 60.9 (C), 61.9(C), 89.2 (Csp), 92.1 (Csp); MS (FAB+), calculated: 250.3781; found: 250.3785.

S3. Refinement

For compound (I), all H atoms could be located in a difference Fourier map and were refined isotropically; the resulting C—H distances range from 0.91 (3) to 0.99 (2) Å. For compound (II), the H atoms were taken into account using appropriate riding models, with C—H = 0.98 Å and with U_iso(H) = 1.5U_eq(C). [Please check added text] The occupancy values of the two disordered O atoms were restrained using the SHELXL SUMP command to add to 1.5.

Computing details

Data collection: SMART (Bruker, 2001) for (I). Cell refinement: SAINT-Plus (Bruker, 2001) for (I). Data reduction: SAINT-Plus for (I). Program(s) used to solve structure: SHELXS97 (Sheldrick, 1997) for (I). Program(s) used to refine structure: SHELXL97 (Sheldrick, 1997) for (I). Molecular graphics: XP (Sheldrick, 1998) for (I). Software used to prepare material for publication: SHELXL97 for (I).

Figures

Fig. 1. A view of (I), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii. Unlabelled atoms are related to labelled atoms by the symmetry operator (1 - x,1 - y,-z). The plot for the isomorphous compound (II) is identical to that for (I) except that the occupancies of O1 and O2 are 0.655 (6) and 0.845 (6) respectively.

(I) Bis(tert-butylsulfonyl)ethyne

Crystal data

C10H18O4S2	F(000) = 284
Mr = 266.36	Dx = 1.368 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 3981 reflections
a = 5.7037 (7) Å	θ = 5.4–56.4°
b = 10.7251 (14) Å	µ = 0.41 mm^−1
c = 10.5678 (14) Å	T = 100 K
β = 90.267 (2)°	Polyhedron, colourless
V = 646.45 (14) Å^3	0.39 × 0.21 × 0.09 mm
Z = 2

Data collection

Bruker APEX diffractometer	1599 independent reflections
Radiation source: fine-focus sealed tube	1559 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.022
ω scans	θmax = 28.3°, θmin = 2.7°
Absorption correction: multi-scan (Blessing, 1995)	h = −7→7
Tmin = 0.854, Tmax = 0.960	k = −14→14
6615 measured reflections	l = −13→14

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) = 0.084	All H-atom parameters refined
S = 1.28	w = 1/[σ^2(Fo^2) + (0.0158P)^2 + 0.7261P] where P = (Fo^2 + 2Fc^2)/3
1599 reflections	(Δ/σ)max < 0.001
109 parameters	Δρmax = 0.40 e Å^−3
0 restraints	Δρmin = −0.35 e Å^−3

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	0.22664 (7)	0.39214 (4)	0.12201 (4)	0.01359 (13)
O1	0.0492 (2)	0.48056 (13)	0.15527 (13)	0.0201 (3)
O2	0.1607 (2)	0.28301 (12)	0.05177 (12)	0.0206 (3)
C1	0.4308 (3)	0.47174 (17)	0.03109 (16)	0.0160 (3)
C2	0.3928 (3)	0.34710 (16)	0.26033 (16)	0.0143 (3)
C3	0.2114 (3)	0.28751 (19)	0.34855 (18)	0.0200 (4)
H3A	0.093 (4)	0.348 (2)	0.374 (2)	0.020 (6)*
H3B	0.292 (4)	0.260 (2)	0.421 (2)	0.031 (7)*
H3C	0.129 (5)	0.218 (3)	0.307 (3)	0.036 (7)*
C4	0.5020 (4)	0.46317 (18)	0.32022 (18)	0.0200 (4)
H4A	0.383 (4)	0.525 (2)	0.345 (2)	0.022 (6)*
H4B	0.616 (5)	0.502 (2)	0.263 (3)	0.033 (7)*
H4C	0.578 (5)	0.440 (2)	0.393 (3)	0.031 (7)*
C5	0.5795 (3)	0.25378 (18)	0.21940 (18)	0.0186 (4)
H5A	0.660 (4)	0.229 (2)	0.294 (2)	0.020 (6)*
H5B	0.508 (4)	0.180 (2)	0.178 (2)	0.022 (6)*
H5C	0.686 (4)	0.291 (2)	0.166 (2)	0.026 (6)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
S1	0.0137 (2)	0.0154 (2)	0.0117 (2)	−0.00155 (15)	−0.00001 (14)	0.00180 (15)
O1	0.0166 (6)	0.0229 (7)	0.0208 (6)	0.0034 (5)	0.0022 (5)	0.0032 (5)
O2	0.0235 (7)	0.0207 (7)	0.0177 (6)	−0.0058 (5)	−0.0036 (5)	−0.0010 (5)
C1	0.0173 (8)	0.0168 (8)	0.0138 (8)	0.0009 (6)	−0.0002 (6)	0.0014 (6)
C2	0.0138 (7)	0.0173 (8)	0.0119 (7)	−0.0005 (6)	−0.0003 (6)	0.0028 (6)
C3	0.0173 (8)	0.0260 (10)	0.0168 (9)	−0.0007 (7)	0.0024 (7)	0.0071 (7)
C4	0.0225 (9)	0.0219 (9)	0.0155 (9)	−0.0027 (7)	−0.0032 (7)	−0.0024 (7)
C5	0.0152 (8)	0.0201 (9)	0.0205 (9)	0.0026 (7)	0.0008 (7)	0.0027 (7)

Geometric parameters (Å, º)

S1—O1	1.4321 (14)	C3—H3B	0.94 (3)
S1—O2	1.4351 (13)	C3—H3C	0.98 (3)
S1—C1	1.7374 (18)	C4—H4A	0.98 (2)
S1—C2	1.8044 (17)	C4—H4B	0.98 (3)
C1—C1^i	1.195 (4)	C4—H4C	0.91 (3)
C2—C5	1.526 (2)	C5—H5A	0.95 (2)
C2—C4	1.528 (2)	C5—H5B	0.99 (2)
C2—C3	1.535 (2)	C5—H5C	0.92 (3)
C3—H3A	0.98 (2)
O1—S1—O2	118.90 (8)	C2—C3—H3C	111.4 (16)
O1—S1—C1	106.66 (8)	H3A—C3—H3C	107 (2)
O2—S1—C1	106.82 (8)	H3B—C3—H3C	111 (2)
O1—S1—C2	110.35 (8)	C2—C4—H4A	112.2 (14)
O2—S1—C2	109.63 (8)	C2—C4—H4B	110.9 (15)
C1—S1—C2	103.22 (8)	H4A—C4—H4B	110 (2)
C1^i—C1—S1	178.9 (2)	C2—C4—H4C	108.2 (16)
C5—C2—C4	111.61 (15)	H4A—C4—H4C	107 (2)
C5—C2—C3	111.87 (15)	H4B—C4—H4C	108 (2)
C4—C2—C3	111.23 (15)	C2—C5—H5A	106.5 (14)
C5—C2—S1	108.10 (12)	C2—C5—H5B	111.3 (14)
C4—C2—S1	109.21 (12)	H5A—C5—H5B	110.0 (19)
C3—C2—S1	104.50 (12)	C2—C5—H5C	110.5 (15)
C2—C3—H3A	110.9 (13)	H5A—C5—H5C	108 (2)
C2—C3—H3B	107.3 (16)	H5B—C5—H5C	111 (2)
H3A—C3—H3B	109 (2)

Symmetry code: (i) −x+1, −y+1, −z.

(II) 1-tert-Butylsulfonyl-2-tert-butylsulfinylethyne

Crystal data

C10H18O3S2	Z = 2
Mr = 250.36	F(000) = 268
Monoclinic, P21/n	Dx = 1.281 Mg m^−3
Hall symbol: -P 2yn	Cell parameters from 1857 reflections
a = 5.7463 (4) Å	µ = 0.40 mm^−1
b = 10.7328 (8) Å	T = 200 K
c = 10.5299 (7) Å	Polyhedron, colourless
β = 92.109 (1)°	0.56 × 0.10 × 0.08 mm
V = 648.98 (8) Å^3

Data collection

Absorption correction: multi-scan (Blessing, 1995)

Tmin = 0.73, Tmax = 0.97

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)] = 0.062	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.147	H-atom parameters constrained
S = 1.05	w = 1/[σ^2(Fo^2) + (0.0379P)^2 + 1.6512P] where P = (Fo^2 + 2Fc^2)/3
1326 reflections	(Δ/σ)max < 0.001
78 parameters	Δρmax = 0.95 e Å^−3
1 restraint	Δρmin = −0.80 e Å^−3

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.

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

	x	y	z	Uiso*/Ueq	Occ. (<1)
S1	0.22683 (16)	0.40575 (11)	0.12677 (9)	0.0460 (3)
O1	0.0685 (8)	0.4894 (4)	0.1539 (4)	0.0518 (14)	0.655 (6)
O2	0.1454 (7)	0.2938 (4)	0.0639 (3)	0.0721 (15)	0.845 (6)
C1	0.4347 (6)	0.4747 (4)	0.0335 (3)	0.0403 (9)
C2	0.4053 (6)	0.3611 (3)	0.2654 (3)	0.0317 (7)
C3	0.2277 (6)	0.3112 (4)	0.3583 (3)	0.0452 (10)
H3A	0.1236	0.3789	0.3824	0.068*
H3B	0.3099	0.2786	0.4344	0.068*
H3C	0.1361	0.2444	0.3173	0.068*
C4	0.5320 (7)	0.4748 (4)	0.3191 (3)	0.0447 (9)
H4A	0.4186	0.5402	0.3368	0.067*
H4B	0.6415	0.5056	0.2572	0.067*
H4C	0.6175	0.4521	0.3980	0.067*
C5	0.5740 (7)	0.2610 (4)	0.2263 (4)	0.0485 (10)
H5A	0.6604	0.2297	0.3017	0.073*
H5B	0.6834	0.2961	0.1667	0.073*
H5C	0.4875	0.1924	0.1852	0.073*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
S1	0.0359 (5)	0.0718 (7)	0.0301 (5)	−0.0125 (5)	−0.0010 (3)	0.0149 (5)
O1	0.057 (3)	0.053 (3)	0.046 (2)	0.006 (2)	0.004 (2)	0.014 (2)
O2	0.079 (3)	0.097 (3)	0.0392 (19)	−0.056 (2)	−0.0132 (17)	0.0001 (19)
C1	0.0385 (19)	0.054 (2)	0.0281 (17)	0.0000 (17)	0.0003 (13)	0.0103 (16)
C2	0.0299 (16)	0.0409 (19)	0.0244 (15)	−0.0005 (14)	0.0018 (12)	0.0056 (14)
C3	0.037 (2)	0.062 (3)	0.037 (2)	0.0005 (18)	0.0083 (16)	0.0188 (18)
C4	0.048 (2)	0.055 (2)	0.0304 (18)	−0.0058 (19)	−0.0028 (16)	−0.0042 (17)
C5	0.044 (2)	0.045 (2)	0.058 (2)	0.0036 (18)	0.0127 (18)	0.0033 (19)

Geometric parameters (Å, º)

S1—O1	1.317 (4)	C3—H3B	0.9800
S1—O2	1.441 (4)	C3—H3C	0.9800
S1—C1	1.739 (4)	C4—H4A	0.9800
S1—C2	1.818 (3)	C4—H4B	0.9800
C1—C1^i	1.182 (7)	C4—H4C	0.9800
C2—C5	1.514 (5)	C5—H5A	0.9800
C2—C4	1.520 (5)	C5—H5B	0.9800
C2—C3	1.535 (4)	C5—H5C	0.9800
C3—H3A	0.9800
O1—S1—O2	116.9 (3)	C2—C3—H3C	109.5
O1—S1—C1	109.1 (2)	H3A—C3—H3C	109.5
O2—S1—C1	108.2 (2)	H3B—C3—H3C	109.5
O1—S1—C2	112.3 (2)	C2—C4—H4A	109.5
O2—S1—C2	108.3 (2)	C2—C4—H4B	109.5
C1—S1—C2	100.77 (16)	H4A—C4—H4B	109.5
C1^i—C1—S1	176.0 (5)	C2—C4—H4C	109.5
C5—C2—C4	111.6 (3)	H4A—C4—H4C	109.5
C5—C2—C3	111.9 (3)	H4B—C4—H4C	109.5
C4—C2—C3	111.3 (3)	C2—C5—H5A	109.5
C5—C2—S1	108.5 (3)	C2—C5—H5B	109.5
C4—C2—S1	109.6 (2)	H5A—C5—H5B	109.5
C3—C2—S1	103.6 (2)	C2—C5—H5C	109.5
C2—C3—H3A	109.5	H5A—C5—H5C	109.5
C2—C3—H3B	109.5	H5B—C5—H5C	109.5
H3A—C3—H3B	109.5

Symmetry code: (i) −x+1, −y+1, −z.