Vibrational spectra of matrix-isolated rhenium trifluoride dioxide and rhenium fluoride trioxide: the molecular shape of ReF3O2

Abstract

The vibrational spectrum of monomeric ReF₃O₂ isolated in inert-gas matrices has been studied using i.r. and Raman techniques. From a total of six possible structural models based on trigonal-bipyramidal or square-pyramidal geometries, only one structure [a trigonal bipyramid with equatorial oxygen atoms (C_2v symmetry)] satisfies the observed spectra in terms of selection rules and relative band intensities. A new synthesis of ReF₃O₂ has been utilised in the preparatron of isotopically enriched ¹⁸O material, the spectra of which confirm that ReF₃O₂ contains two equivalent oxygen atoms. This C_2v structure is thus analogous to that proposed for ClF₃O₂. The vibrational spectrum of ReFO₃ produced as a by-product during these studies is also discussed in detail.