COMPLEX HALIDES OF TRANSITION METALS .6. ELECTRON TRANSFER SPECTRA OF HEXAHALOTUNGSTATES(4) AND (V) AND HEXACHLOROMOLYBDATE(V) ANION

The electronic absorption spectra of the hexahalo anions MoCl-6, WCl-6, WBr-6, WCl2-6 and WBr2-6 have been measured. Assignments are made in the light of current theories on the electron transfer spectra of species of the type MXn-6. In all cases the halogen(π) → metal (γ5g or γ3g) transitions have been located and these results compared with the related d0 and d1 systems of the titanium and vanadium subgroups, already recorded in the literature. For the MoCl-6 anion two possible assignments are suggested. Jørgensen's optical electronegativity parameter χopt has been calculated for Mo (V), W (IV) and W (V) using the present spectral data. The diffuse reflectance spectrum of [(CH3)4N]TaBr6 has also been recorded and compared to that of the WBr-6 anion. The solid state spectrum of WCl6 is reported for the first time. © 1968.