Triammine Series

Two grams of triamminechromium (IV) oxide (No. 137) are covered with 30ml of cold glacial acetic acid and the stirred mixture is cooled in ice until it partly freezes. Then 20ml of ice-cold concentrated hydrochloric acid are stirred in and the sluny is cooled for 10-15 minutes in ice with occasional stirring. The blue-violet solid is filtered off, washed with 95% alcohol and with ether, and then dried for 15-30 minutes at 60°C. 

A small quantity of chiorodiaquotriamminechromium (III) chloride may be isolated from the mother liquor by the addition of 95% alcohol and ether. This may be converted into No. 136 by drying at 100°C. 

Five grams of dichloroaquoethylenediaimneamimnecobalt (III) chloride (No. 139) are quickly dissolved in 25-30ml of water at 0-5°C and filtered into an equal volume of 48% hydrobromic acid cooled in ice. The olive-green product separates rapidly and, after standing in the cold for about 15 minutes, it is filtered off and dried in vacuo over solid alkali. 

The material has the greatest known number of different coordinated groups around the central cobalt atom. 

This compound is prepared similarly to No. 138, using 5.0g of dichloroaquotriamminecobalt (III) chloride (No. 139) and 35ml of water. 

---

A simple route to Cr(III) tridentate monoamines was reported earlier this year (10), based on Werner s early work with Cr04-(NH3)3 or [Cr(NH3)3(02)2] in the triammine series (47, 50),... 

Biltz 4 carried out a series of investigations on the vapour pressures of solutions of silver chloride and ammonia, and came to the conclusion that silver chloride forms the triammine, [Ag(NH3)3]Cl, at atmospheric pressure below 20° ., and the sesquiammine, 2AgCl(NH3)3, at temperatures between 20° and 60° C. Above 00° C. silver chloride does not unite with ammonia. 

Many examples of the triacido-triammine cobalt series are known, and isomerism occurs in the group. 

Trinitro-triammino-cobalt, [Co(NH3)3(N02)3], was the first member of the series prepared. It is best prepared by treating a solution of eobaltous chloride with an ammoniacal solution of sodium nitrite and oxidising the mixture by means of air. The liquid after oxidation is allowed to stand for some days, when crystals separate these are filtered and washed with cold water to free them from chloride, and dissolved in hot water containing a little acetic acid. On cooling the acid liquid trinitro-triammine cobalt separates out, and later, from the same solution, the double salt, [Co(NH3)4(N02)2][Cb(NH3)2(N02)4], separates.1... 

---