Electron Transfer Spectra of the Hexachloro- and Hexabromoniobate(V) and Tantalate(V) Anions

The electron transfer spectra of the hexachloro- and hexabromoniobate (V), and-tantalate(V) anions are investigated with particular care to avoid hydrolysis products. New interpretations are given, and the optical electronegativities χ of Nb(V) and Ta(V) are recalculated. The difference between both χ values is 0.2, in better agreement with the differences observed for metals of the second and third transition series.