Stereochemical features of the disulfoxides 1,3-bis(n-propylsulfinyl)propane (BPSP) and 1,2-bis(methylsulfinyl)ethane (BMSE), and their copper(II) complexes. Crystal and molecular structure of meso-BPSP, [trans-Cu(meso-BPSP)2(H2O)2](ClO4)2, trans-Cu(meso-

Diastereomeric meso and rac forms of 1,3-bis(n-propylsulfinyl)propane (BPSP) and 1,2-bis(methylsulfinyl)ethane (BMSE) have been separated and treated with Cu(ClO4)2 to obtain [trans-Cu(meso-BPSP)2(H2O)2](ClO4)2 (2) trans-Cu(meso-BMSE)2(ClO4)2 (3) and trans-Cu(rac-BMSE)2(ClO4)2 (4). The configurational assignment to BPSP has been performed by single crystal X-ray analysis, showing that the α (m.p. 139.0–139.9 °C) and β (m.p. 107.0–107.6 °C) forms correspond to the meso and rac isomers, respectively. Enthalpies of fusion, determined by differential scanning calorimetry techniques, are 34.3 (meso-BMSE), 22.2 (rac-BMSE), 40.6 (meso-BPSP), and 35.1 kJ mol−1 (rac-BPSP). Single crystals, acceptable for X-ray diffraction studies, were grown by the hanging-drop method of vapor diffusion and micro-seeding techniques. The crystal structure of meso-BPSP (1) is characterized by an anti conformation of the propane bridge. The two sulfinyl bonds (av. SO bond distance, 1.487(4) Å) are nearly parallel. In fact, the S→O vectors form an angle of 2.3° and the pseudo-torsion angle OS⋯SO is of 2.2°. Crystals belong to the C2/c space group, with a=32.285(11), b=5.315(5), c=15.232(7) Å, β=109.98(3)°. The structure was refined to R=0.092. Crystal data for the copper complexes are space group P2/n, a=13.914(7), b=7.834(4), c=14.805(11) Å, β=96.61(5)° for 2; space group P21/c, a=7.348(7), b=17.892(4), c=8.620(2) Å, β=113.06(2)° for 3; space group P21/a, a=8.343(3), b=12.337(6), c=9.390(3) Å, β=97.35(3)° for 4. The structures were refined to R=0.066, 0.062, and 0.097 for 2, 3, and 4, respectively. The crystal structures of the meso Cu(II) complexes 2 and 3 are characterized by linear chains of copper atoms, bridged by two disulfoxide molecules acting as bis-monodentate O-ligands. In the rac complex 4, BMSE acts again as a μ2-O,O ligand, but forms layers with a net structure containing four copper atoms per mesh, and each layer contains sulfur atoms with both R and S chirality. In the copper complexes the mean SO bond length is of 1.520(3) Å, confirming the already observed increase in comparison to free sulfoxides.