Darstellung und Schwingungsspektren von Fluoro-Chloro-Osmaten(IV) einschließlich der Stereoisomeren/ Preparation and Vibrational Spectra of Fluoro-Chloro-Osmates(IV) Including Stereoisomers

Abstract

Abstract The stepwise replacement of ligands in [OsCl6]2- by oxidation with BrF3 generates the mixed complexes [OsFnCl6-n]2-, n = 1 - 5, of which the species with n = 2,3,4 are cw-configurated. Due to the stronger trans-effect of Cl compared to F on treatment of [OsF5Cl]2- and cis-[OsF4Cl2]2- with Cl- the trans-isomers are formed stereospecifically. The pure fluoro-chloro-osmates(IV) are separated by ion exchange chromatography on diethylaminoethylcellulose. From the pairs of stereoisomers the cis-compounds are always first eluted, whereas the trans-complexes are moving faster in an electric field by 3 to 5% . The vibrational spectra of octahedral mixed ligand complexes are generally discussed according to point groups Oh, D4h, C4v, C3v and C2v. For the fluoro-chloroosmates(IV) all stretching and deformation bands are assigned. They are observed in the characteristic regions; ν(OsF): 625-490 > ν(OsCl): 360-300 > δ (FOsF): 275-210 > δ (FOsCl) > δ (ClOsCl): 190-150 > νL: < 100 cm -1.