Comparative interpretation of absorption spectra of technetium (iv) and rhenium (iv) hexahalides

Abstract

Absorption spectra of aqueous solutions of TcX6 and ReX6 (X=F, Cl, Br, I) are measured between 8 000 and ~50 000 cm -1 and theoretically discussed. The electron transfer spectra indicate the optical electronegativity xopt=2.25 for Tc(IV) and 2.05 for the less oxidizing Re (IV). The spectrochemical parameter A is determined to 28 400 cm -1 in TcF6 and 32 800 cm -1 in ReF6-. The nephelauxetic effect is evaluated from the spin-forbidden intra-sub-shell transitions in all eight species, and from the two spin-allowed bands of TcF6 - The vibrational structure of the narrow absorption bands and the possible weak distortion from octahedral symmetry of Tc(IV) hexahalides are discussed. © 1965, IEEE. All rights reserved.