Schwingungsspektren und Normalkoordinatenanalyse der Bromo-Iodo-Osmate(IV), [OsBrnI6-n]2-, n = 0-6 / Vibrational Spectra and Normal Coordinate Analysis of Bromo-Iodo-Osmates(IV), [OsBrnI6-n]2-, n = 0-6

Abstract

The IR and Raman spectra of the ten bromo-iodo-osmates(IV) [OsBrnI6-n]2-, n = 0-6, including the geometrical isomers for n = 2, 3, 4, have been recorded at low temperature. The vibrational spectra are completely assigned according to point groups Oh, D4h, C4v, C3v, and C2v, as supported by normal coordinate analyses based on a general valence force field. Due to the different trans-influences Br<I in asymmetric axes Br′–Os–I′, the Os–I′ bonds are strengthened and the Os–Br′ bonds are weakened, as indicated by valence force constants, for Os–I′ on average 4% higher and for Os–Br′ 4% lower, as compared with the values calculated for symmetric I–Os–I and Br–Os–Br axes, respectively.