Structural parameters of dimethyl sulfoxide, DMSO, at 100 K, based on a redetermination by use of high-quality single-crystal X-ray data

The title compound, C2H6OS, is a high melting, polar and aprotic solvent widely used in organic and inorganic chemistry. It serves as a H-atom acceptor in hydrogen bonding and is used as an ambidentate ligand in coordination chemistry. The evaluation of the influence of inter-molecular inter-actions on the inter-nal structural parameters of the chemically bonded DMSO mol-ecules affords precise structural data of the free mol-ecule as a point of reference. So far, valid data have been obtained only by use of neutron powder diffraction [Ibberson (2005 ▸). Acta Cryst. C61, o571-o573]. In the present redetermination, structural data have been obtained from a single-crystal X-ray diffraction experiment at 100 K, revealing a better comparison with DMSO mol-ecules in other crystal structures. In the solid state, the pyramidal mol-ecule exhibits a nearly perfect Cs symmetry [including H atoms, which are eclipsed with respect to the C⋯C axis], with a C-S-C bond angle of 97.73 (7)° and an S-O bond length of 1.5040 (10) Å, corresponding very well with an S=O double bond, and with almost equal S-C bond lengths [mean value = 1.783 (4) Å] and O-S-C bond angles [mean value = 106.57 (4)°]. The crystal packing is influenced by C-H⋯O inter-actions (2.42-2.47 Å) between all three H atoms of only one methyl group with the O atoms of three neighbouring DMSO mol-ecules. The inter-actions of the O atom with H atoms (or Lewis acids, or hydrogen-donor groups) of adjacent mol-ecules in relation to the orientation of the complete DMSO mol-ecule are described in terms of the angle ω and the distance dnorm; ω is the angle between the pseudo-mirror plane of the mol-ecule and the plane defined through the S=O bond and the inter-acting atom, and dnorm is the distance of the inter-acting atom from the plane perpendicular to the S=O bond.