Chalconide ions

The formula is converted into dimensionless units by defining a dimensionless distance based on a characteristic spacing for each compound. It is noted that the closest interionic distance can be specified as the sum of two ionic radii, d = r + r+. Using the well established anionic radii for halide and chalconide ions [75], a conversion factor R = /r 1 r is calculated in each case, and used to define the dimensionless distance d = d/R, such that the Madelung energy,... 

The stability of chalconide (ionic) compounds decreases from oxygen to tellurium treatment with water produces XH- with X = O or S (hydroxyl and thiol radicals, respectively), but XH2 with X = Se or Te. On warming, aqueous solutions of HS evolve hydrogen sulfide, evidencing that the hydrosulfide ion is much less stable than hydroxide. 

The electrochemical preparation of metal chalcogenide compounds has been demonstrated by numerous research groups and reviewed in a number of publications [ 1-3]. For the most part, the methods that have been used comprise (a) cathodic co-reduction of the metal ion and a chalcogen oxoanion in aqueous solution onto an inert substrate (b) cathodic deposition from a solvent containing metal ions and the chalcogen in elemental form (the chalcogens are not soluble in water under normal conditions, so these reactions are carried out in non-aqueous solvents) (c) anodic oxidation of the parent metal in a chalconide-containing aqueous electrolyte. 

We saw in Chapter 4 that from the geometrical standpoint the structures of many inorganic compounds, particularly halides and chalconides, may be regarded as assemblies of close-packed non-metal atoms (ions) in which the metal atoms occupy... 

Here, IF5 serves both as the fluorinating agent and the solvent. In these complexes there is considerable interionic electron spin coupling which makes them antiferromagnetic (Neel temperatures of the order of 100— 150°K). These couplings must take place by overlap of orbitals of the fluoride ions of adjacent [MF6] units in the crystals, that is, by a superexchange process similar in principle to that in halides and chalconides of some divalent metals of the first transition series. Such an explanation, of course, requires the assumption of significant overlap of metal r/rc (t23) orbitals with fluoride ion pn orbitals. 

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