N,N′-(Ethane-1,2-diyl)bis(methanesulfonamide)

The molecular structure of the title compound, C4H12N2O4S2, has crystallographic inversion symmetry. The central N—C—C—N moiety was refined as disordered over two sets of sites with an approximate occupancy ratio of 3:1 [0.742 (15):0.258 (15). In the crystal, N—H⋯O hydrogen bonds link adjacent molecules into a thick sheet structure parallel to the b-axis direction.


Comment
Sulfonamides have long been utilised as bacteriostatic agents in both human and veterinary medicine, and their derivatives have a wide range of pharmacological applications (Alyar et el., 2011(Alyar et el., , 2012. In recent years, concentrated effort has been made on the effectiveness of the disulfonamide compounds as antimicrobial agents, and reported here is the solid state structure of a related disulfonamide intended for further studies: N,N′-ethane-1,2-diyl-bis(methanesulfonamide) ( Figure 1). The asymmetric unit of the title consists of half of the molecule, as the central C-C bond sits on top of an inversion centre. This structure is directly analogous to several previously reported structures (e.g. Al-Dajani et al., 2011a,b;entries AYONOS and AYORUC in the Cambridge Structural Database (version 5.34, Allen (2002))), which all contains aryl sulfonamide moieties. Unlike these reported structures, the methyl group does not exert significant steric pressure on the neighbouring sulfur atom. While the bond angle surrounding the sulfonamide S atom ranges between 106.80 (11)° and 117.60 (13)°, the overall geometry does not significantly deviate from an ideal tetrahedral configuration (average bond angle = 109.4°). The molecule is also slightly twisted at the N atom (C1-S1-N1-C2 torsion angle = -56.19°). An extended network is formed through intramolecular hydrogen bonding. Any one molecule is hydrogenbonded to four different neighbouring molecules ( Figure 2, Table 1).

Experimental
THF solution of 1,2-diaminoethane was added dropwise to the tetrahydrofuran (THF) solution of methyl sufonyl chloride in equimolar fashion, with the temperature maintained between -5 and -10°C. The reaction mixture was allowed to warm and stirred for 24 h at room temperature. Upon completion of the reaction, the solvent was removed under vacuum, and the solid residue was purified by column chromatography. The product was identified with 1 H-NMR. To recrystallize, the product was disolved in minimum amount of hot dichloromethane (DCM), and colourless, plate-like crystals formed upon gradual cooling of the solution.
Please note that a polymorph (deposited with the Cambridge Crystallographic Data centre as CCDC 958590) of the title compound was obtained initially. Crystals of this polymorph were obtained at elevated temperature, in a complexation reaction using the title compound as a ligand. Unfortunately, the crystallization condition cannot be accurately identified, and independent crystallization using the condition stated gave the structure reported in this manuscript.

Refinement
Minor rotational disorder was modelled and the refined occupancy ratio is 0.742:0.258 (15). The SHELXL constraint RIGU was used for the disordered carbon of the minor component, and SADI to restrain the refinements of S-N′ and N′-C′ bond lengths. All protons were refined using suitable riding models.

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 F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger. A disorder of the N-C-C-N chain in the molecule is observed. The occupancies were allowed to be refined freely. SADI restrains were used on the bond lengths of the S-N bond and the N-C bond. Furthermore, the hard constrain RIGU was placed on the displacement parameters of C2′. ISOR did not significantly improve the refinement.