HexaChloroiridate , ammonium

Insoluble iridium dioxide from the sodium peroxide fusion is dissolved in aqua regia, oxidized with nitric acid, and precipitated with ammonium chloride as impure ammonium hexachloroiridate(IV), To purify this salt, it is necessary to redissolve the compound and precipitate out the... 

The residue insoluble in H2S04 is fused with Na202 poured into thin slabs and cooled. Ir is oxidized in the fusion of IrC>2, which is insoluble in H2O, Ru and Os form soluble sodium salts and are separated from the Ir by filtration, The insoluble Ir02 is dissolved m aqua regia, and ammonium hexachloroiridate(lV) is precipitated by the addition of NH4CI. Calcining yields pure Ir sponge. 

Nitrosylpentaamminecobalt(II) chloride, synthesis 49 cts-Bromoamminebis (ethylenediamine) cobal t (111) bromide, CIS- and trans-aquoamminebis(ethylenediamine)cobalt(IIl) bromide, and cis- and triphenylphosphine)rhodium and chloro-carbonylbis(triphenylarsine)rhodium, synthesis 56 Sodium hexachlororhodate(III) 2-hydrate and potassium hexachlororhodate(III) 1-hydrate, synthesis 57 Ammonium hexachloroiridate(IV), synthesis 58 Resolution of the tris(l,10-phenanthroline)nickel(II) ion, synthesis 59... 

Ammonium hexachloroiridate(IV) can be prepared by the metathesis of sodium hexachloroiridate(IV) with ammonium chloride or by the addition of ammonium chloride to either a solution of iridium(IV) hydroxide in hydrochloric acid or of iridium(IV) chloride. Although many workers have prepared sodium hexachloroiridate(IV) by chlorinating mixtures of sodium chloride and iridium, few exact data are available concerning optimum temperatures, reaction times, and yields. 

Ammonium hexachloroiridate(IV) forms strongly refracting octahedra which vary from red-black to almost black depending on crystal size. Above 200° it decomposes to metallic iridium, nitrogen, ammonium chloride, and hydrogen chloride. 

Aqueous solutions of ammonium hexachloroiridate(IV) are readily reduced to hexachloroiridate(III) by a variety... 

In the present synthesis, the more readily available ammonium hexachloroiridate(IV) is substituted for iridium-(IV) chloride. An alternative synthesis involving preliminary reduction of ammonium hexachloroiridate(IV) to hexachloroiridate(III) with ammonium oxalate has been found to give substantially the same total yield of both isomers, but the amount of cis isomer obtained was about twice that of the trans isomer. ... 

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. 

A solution of 0.711 g. (0.005 mol) of ammonium oxalate 1-hydrate in 20 ml. of boiUng water is added in 1-ml. portions with continuous stirring to 4.42 g. (0.010 mol) of ammonium hexachloroiridate(IV)f contained in a 100-ml. round-bottomed flask Caution. Effervescence). The dark reddish brown solution is warmed on the steam bath for 10 minutes to ensure complete reduction. J After the solution has cooled to room temperature, 8.06 ml. (7.91 g. 0.100 mol) of pyridine (density, 0.892) dissolved in 3.33 ml. 

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