Elektronenspektren der Fluoro-Chloro-Osmate(IV), [OsFnCl6–n]2-,n = 0– 6

Abstract

The electronic absorption spectra of the solid tetraalkylammonium salts of [OsFnCl6-n]2-, n = 0 -6 , including the stereoisomers for n = 2, 3, 4, are measured at 10 K. The strong bands in the UV/VIS region are assigned to charge-transfer transitions from π(t1 u, t2 u) and σ (t1 u) Cl orbitals into the π (t2g 4) Os(IV) level. The observed splittings and shifts are interpreted by qualitative MO treatment according to point groups D 4h, C4v, C 3v and C 2v of the mixed complexes. The weak intraconfigurational transitions within the t2g 4 configuration of Os(IV) are splitted by spin orbit coupling and lowered symmetry into multiplets with up to five states, observed in the NIR regions 4700-7300, 10 700-13 200 and 17 000-21 600 cm -1. The O -O - transitions are deduced from vibrational fine structure; in some cases they are confirmed by electronic Raman bands with the same frequencies and by hot bands observed in the normal temperature spectra. Within the series of complexes all absorption bands are shifted systematically to higher energies with increasing number of F-ligands.