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) Å, 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 P1̄, with a 8·193(2), b 8·941(3), c 13·837(3) Å, α 79·77(2), β 79·91(2), γ 65·03(2)°, Z 2, 4152 unique reflections (173 parameters), converging at R 0·021 and R_w 0·018.