Elektronenspektren der Fluoro-Chloro-Osmate(V), [OsF_nCl_6–n]^–, n = 0 — 6

Abstract

The electronic absorption spectra of the solid tetraethylammonium salts of [OsF"C16_"]-are measured at 10 K. The strong bands in the UV/YIS region are assigned to charge transfer transi tions from 7r (t ] u, t2") andCl orbitals into the 7r(t2g) Os(V) level. The weak intraconfigurational excitations within the t2g manifold of Os(V) are split by spin-orbit coupling and lowered symmetry into Kramers doublets, observed in the range 5500-18000 cm-1. The 0 -0-transitions are deduced from vibrational fine structure; for the centrosymmetric complexes they are con firmed by hot bands recorded in the normal temperature spectra. There is a systematical shift of all absorption bands to higher energy with increasing Einleitung

Preparation and Spectroscopic Investigations of Mixed Octahedral Complexes and Clusters

“…Vibrational spectroscopy has proven, by virtue of the trans influence, that the bond to Cl in an asymmetric F • -M-Cl′ axis is stronger than in the symmetric Cl-M-Cl axis (see section II.B). This can bee seen qualitatively by the splitting and broadening of respective bands in the LMCT spectra of the In addition to the complete series, [OsF n Cl 6-n ] 2-, n ) 0-6, with the central metal ion in the d 4 configuration, LMCT spectra from the corresponding d 3 complexes of Os(V) 153 and d 5 complexes of Ir(IV), 154 and even some species from the d 4 Ir(V) system have been recorded. 60 Spectra of analogous complexes from the different series are essentially similar, although resolution is of a different quality, and there are no vibronic fine structures in the spectra within the Os(IV) and Os(V) series.…”

“…In addition to the complete series, [OsF n Cl 6 - n ] 2- , n = 0−6, with the central metal ion in the d 4 configuration, LMCT spectra from the corresponding d 3 complexes of Os(V) and d 5 complexes of Ir(IV), and even some species from the d 4 Ir(V) system have been recorded . Spectra of analogous complexes from the different series are essentially similar, although resolution is of a different quality, and there are no vibronic fine structures in the spectra within the Os(IV) and Os(V) series.…”

“…By comparison of LMCT bands of the isostructural species from the d 3 , d 4 , and d 5 systems characteristic shifts have been correlated to the optical electronegativity and the oxidation state of the central ions. According to the strongly oxidizing power of the pentavalent metals, which facilitates charge transfer from the ligands, bathochromic shifts of ∼8000 cm -1 between Ir(V) and Ir(IV), 7000 cm -1 between Os(V) and Os(IV) and 15 000 cm -1 between corresponding d 4 species of the fluorochloroiridates(V) and -osmates(IV) have been observed. ,,, …”

“…This allows the assignment of the very weak 0−0 transitions by the symmetrical appearance of vibrational bands at higher and lower frequencies. In the same manner, the intraconfigurational transitions of the individual species within the series, [OsF n Cl 6 - n ] - , [OsCl n Br 6 - n ] 2- , [IrF n Cl 6 - n ] 2- , [IrF n Cl 6 - n ] - , and [RuCl n Br 6 - n ] 2- , have been measured and assigned.…”

“…According to the strongly oxidizing power of the pentavalent metals, which facilitates charge transfer from the ligands, bathochromic shifts of ∼8000 cm -1 between Ir(V) and Ir(IV), 7000 cm -1 between Os(V) and Os(IV) and 15 000 cm -1 between corresponding d 4 species of the fluorochloroiridates(V) and -osmates-(IV) have been observed. 60,151,153,154 The minor differences of the electronegativities between the heavier halides, Cl, Br, and I, make the assignments of LMCT transitions to the respective ligands in mixed coordination spheres impossible. Nevertheless, for the sake of an overall spectroscopic characterization, the spectra have been measured in solution and at low temperature in solid state for the following series: [ReCl n Br 6-n ] 2-, 157 [ReCl n I 6-n ] 2-, 148 [OsCl n Br 6-n ] 2-, 158 [IrCl n Br 6-n ] 2-, 158 [OsCl n I 6-n ] 2-, 159 and [RuCl n Br 6-n ] 2-.…”