Barium ruthenate

The reversibility of the [RuO ] - [RuO ] couple cf. 1.4.1.3) and the Raman spectrum of ruthenate in aqueous base suggest that it is tetrahedral, [RuO ] , in solution. Thus, unlike RuO and [RuO ] , ruthenate changes the structure of its anion from that of the trigonal bipyramidal fra 5-[Ru(0H)3(0)3] in the solid potassium and barium salts to tetrahedral [RuO ] in solution. There is evidence from electronic spectra of potassium ruthenate doped into K CrO and K SeO and of barium ruthenate doped into BaSO, BaCrO and BaSeO that, in that these enviromnents at least, the Ru is tetrahedrally coordinated [533]. 

Ruthenate is unusual in that it appears to undergo a change of stmcture from the solid state to aqueous solution as indicated above, RuO and [RnO ] retain their tetrahedral structures in the solid and solution states. Potassinm and barium ruthenates contain the franx-[Ru(OH)j03] anion, while Cs2[RuO ] is tetrahedral. 

Electronic spectra (Table 1.1, Fig. 1.2) have been measnred for the orange soln-tions of (RuO ] in aqueous base from 250-600 nm. [212-215, 222], and reproduced [215, 222]. There are two at 460 and 385 nm. [212, 213, 222] or three bands in the visible-UV region, at 460, 385 and 317 nm [214, 215]. These appear to be at the same positions as those for [RuO ] but the intensities and hence the general outline of the two spectra are very different. Woodhead and Fletcher reviewed the published molar extinction coefficients and their optimum values / dm (mol" cm" ) are 1710 for the 460 nm. band, 831 for the 385 nm. band and 301 for the 317 nm. band - the latter band was not observed by some workers [214]. The distinctive electronic spectrum of ruthenate in solution is useful for distinguishing between it, [RuO ]" and RuO [212, 222]. Measurements of the electronic spectra of potassium ruthenate doped in K CrO and K SeO and of barium ruthenate doped into BaSO, BaCrO, and BaSeO (in all cases the anions of these host materials are tetrahedral) indicate that in that these environments at least the Ru is tetrahedrally coordinated. Based on this evidence it has been suggested that [RuO ] in aqueous solution is tetrahedral [RuO ] rather than franx-[Ru(0H)3(0)3] [533, 535]. Potential modulated reflectance spectroscopy (PMRS) was used to identify [RuO ] and [RuO ] " in alkaline aqueous solutions during anodic oxidation of Ru electrodeposited on platinum from [Ru3(N)Clg(H30)3] [228]. 

Ruthenites.—Ruthenium dioxide unites with metallic oxides to yield ruthenites of general formula M"RuOs. The best-known salt is barium ruihenite, BaRuCL, which is obtained by heating barium ruthenate to 440° C. in vacuo, when oxygen is evolved and a bluish black residue of ruthenite remains, which is insoluble in water. Treatment with hydrochloric acid converts it into the trichloride.4... 

C2nH12BaN18O2 Ru2 9 H2O, Barium tris(dihydrogenviolurato)ruthenate nonahydrate, 46B, 1186... 

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