Preparation of cis - and trans -[OsCl 2 (Me 2 SO) 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 P -1, with a 8·193(2), b 8·941(3), c 13·837(3) Å, a 79·77(2), ß 79·91(2), ? 65·03(2)°, Z 2, 4152 unique reflections (173 parameters), converging at R 0·021 and Rw 0·018.