MULTIPLE BONDS BETWEEN MAIN GROUP ELEMENTS AND TRANSITION-METALS .94. PYRIDINE COMPLEXES OF ORGANIC OSMIUM OXIDES - SYNTHESIS, SPECTRA AND CRYSTAL-STRUCTURES OF R2OSO2.(L) AND R2OSO2.(L)2 COMPLEXES

Alkylosmium(VI) complexes of compositions R2OsO2.(L) and R2OsO2(L)2 are accessible from glycolate osmium(VI) complexes (R = CH3, CH2Si(CH3)3; L = pyridine). The equilibrium R2OsO2.(L)2 half-arrow-right-over-half-arrow-left R2OsO2.(L)+L is adjustable by vacuum (rght) and pyridine (left). The dimethyl complex (CH3)2OsO2.C5H5N, albeit monomeric in solution, has a trinuclear structure (Os3O3 core geometry) in the crystal, while the formally analogous derivative [(CH3)3SiCH2]2OsO2.C5H5N is monomeric, displaying a strongly distorted trigonal-bipyramidal geometry (O-Os-O' angle 141.3(4)degrees/141.7(4)degrees). All four complexes R2OsO2.(C5H5N)2 (R = CH3, 3a; CH2Si(CH3)3, 3b) and R2OsO2.(C5H5N) (R = CH3, 4a; CH2Si(CH3)3, 4b) were characterized by means of single-crystal X-ray diffraction techniques.