Tetrachloro dipyridine iridium IV

Both isomers of tetrachloro(dipyridine)iridium(IV) are nonelectrolytes, which are insoluble in water, ethanol, and ethyl ether but slightly soluble in chloroform, yielding violet solutions. Both are deep violet, the cis compound being somewhat darker than the trans compound. 

Since 6-coordinated iridium has an octahedral configuration, tetrachloro (dipyridine) iridates (III) occur in two isomeric forms—cis (orange) and trans (red). The sparingly soluble pyridinium salts are readily isolated and hence are convenient starting materials for the synthesis of other members of the series. Because of their widely differing solubilities in water, the cis and trans pyridinium salts are easily separated. The procedure given below, which is modified from Delepine s original preparation, employs readily available ammonium hexachloroiridate(IV), which is converted to hexachloroiridate(III) by reduction with ammonium oxalate. 

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