MULTIPLE BONDS BETWEEN MAIN GROUP ELEMENTS AND TRANSITION-METALS .101. STEREOSELECTIVE SYNTHESIS OF MIXED ALKYLATED OSMIUM OXIDES

Two-step alkylation of osmium(VI) glycolate complexes yields mixed-alkyl oxoosmium complexes of formula (R1)2(R2)2Os = O along two different routes. Due to the chelate ligands present in the starting compounds, square-pyramidal alkyl complexes of cis-geometry (R1/R1 and R2/R2 respectively) are obtained in stereoselective reactions. The crystal and molecular structure of dimethyl(2,3-dimethylbutane-2,3-diolato)oxoosmium(VI) (4a) has been determined by X-ray diffraction, again revealing a square-pyramidal core geometry with the oxo ligand at the apex position [d(OsO) = 162.1(4) pm].