Preparation of cis- and trans-[OsCl2(Me2SO)4], and X-ray crystal structures of the all-S-bound isomers

Efficient syntheses of the cis and trans isomers of [OsCl2(Me2SO)(4)] are reported. While a structural study of the trans isomer confirms the spectroscopically assigned all-S-bound Me2SO configuration, a crystallographic determination of the cis isomer reveals a previously unheralded all-S-bound Me2SO geometry, in contrast to the spectroscopically inferred configuration predominant in solution which has one O-bound ligand. For trans-[OsCl2(Me2SO)(4)], crystals are tetragonal, space group I 4/m, with a 9.092(2), c 11.212(3) Angstrom, Z 2, 566 unique reflections (34 parameters), converging at R 0.026 and R-w 0.032. For cis-[OsCl2(Me2SO)(4)], crystals are triclinic, space group P (1) over bar, with a 8.193(2), b 8.941(3), c 13.837(3) Angstrom, alpha 79.77(2), beta 79.91(2), gamma 65.03(2)degrees, Z 2, 4152 unique reflections (173 parameters), converging at R 0.021 and R-w 0.018.