Matrix-isolation studies on metal coordinated oxyanions. The shape of molecular MClO4, MClO3, MReO4, and EuWO4 systems

Alkali-metal perchlorates (MClO4), chlorates (MClO3), perrhenates (MReO4), and EuWO4 were investigated with the aid of matrix-isolation IR spectroscopy. The Raman spectra of the MClO4 and MReO4 molecules were also measured in inert matrices. 18O-substitution experiments were carried out on Li 35ClO4, K 35ClO4, Cs 35ClO3, KReO4, and EuWO4 in order to provide the assignment of the observed spectra and to establish the molecular structure of these molecules in the vapor phase. These experiments indicate a C2v bidentate structure for all the MXO4 molecules. The ClO−4 and ReO−4 anions are slightly distorted tetrahedrons with bond angles close to 109°. The WO=4 anion is a distorted tetrahedron with the OWO bond angles equal to 86° and 109°. Alkali chlorates MClO3 are species of C3v symmetry with the metal cation placed on the C3 axis of the ClO−3 pyramidal anion.