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-BMSE)(2)(ClO4)(2), and trans-Cu(rac-BMSE)(2)(ClO4)(2)

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 alpha (m.p. 139.0-139.9 degreesC) and beta (m.p. 107.0-107.6 degreesC) 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) Angstrom) are nearly parallel. In fact, the S --> O vectors form an angle of 2.3 degrees and the pseudo-torsion angle O-S . . .S-O is of 2.2 degrees. Crystals belong to the C2/c space group, with a = 32.285(11), b = 5.315(5), c = 15.232(7) Angstrom, beta = 109.98(3)degrees. 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) Angstrom, beta = 96.61(5)degrees for 2; space group P2(1)/c, a = 7.348(7), b = 17.892(4), c = 8.620(2) Angstrom, beta = 113.06(2)degrees for 3; space group P2(1)/a, a = 8.343(3), b = 12.337(6), c = 9.390(3) Angstrom, beta = 97.35(3)degrees 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 mu (2)-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) Angstrom, confirming the already observed increase in comparison to free sulfoxides. (C) 2001 Elsevier Science BN. All rights reserved.