Ammino compounds

Ammino-salts of Cupric Halides.—When an aqueous solution of cupric chloride is treated with an aqueous solution of ammonia the hydroxide is precipitated, but if excess of ammonia be added the precipitate dissolves, forming a deep blue solution. The liquid contains the tetraminino-chloride and higher ammino compounds, depending on the concentration of the ammonia in solution and the temperature. 

Ammino-cupric Bromides.—Cupric bromide, like euprie chloride, absorbs ammonia gas, forming complex ammino-compounds. The following ammines of cupric bromide have been described Hexammino-cupric bromide, [Cu(NH3)6]Br2 pentammino-cupric bromide, [Cu(NH3)5]Br2 diammino-cupric bromide, [Cu(NTI3)2]Br2 and decammino-tricupric bromide, [Cu3(NH3)10]Br8. 

Ammino-cuprous Iodides.—Cuprous iodide, like the other halides of copper, absorbs ammonia gas, forming ammino-compounds. If the iodide be saturated with ammonia gas at 0° C. two ammines appear to be formed, hexammino-cuprous iodide, [Cu2(NII3)6]I2, and triammino-cuprous iodide, [Cu2(NII3)3]I2. These are the only compounds formed according to Lloyd s examination by measuring change of pressure with change of composition. 

It is suggested that in the ammines of higher co-ordination number two shells of ammonia may surround the central metallic atom, and in the case of stannous bromide the co-ordination numbers are assumed to be 3+2 or 3+6, thus giving an explanation of the ammino-compounds containing nine or five molecules of ammonia.1... 

Cr(XH3)s(XO.,)]R .—These salts were discovered by Christensen in 1SS1. It is still doubtful whether the salts are true nitrito-salts with the group O—NO in the nucleus, or whether they are nitro-compounds they are yellow in colour, which points to the possibility that they are nitro-eompounds. Only one series is known, whereas in the eobalt-ammino-compounds both nitro- and nitrito-salts have been isolated (see p. 144). 

The trinitro-triammine cobalt has practically no conductivity.3 Werner s theory is further supported by the fact that by the introduction of a fourth molecule of ammonia into the triacido-triammine compound the solution becomes once more conducting, as one (N02) group is displaced from the co-ordination complex. The eobalt-ammino-compounds, therefore, containing fewer than three ammino-radicles, contain non-ionisable acidic radicle, and those containing more than three contain ionisable acidic radicles. The generalisation made in connection with the triammino-eompounds led, therefore, to the establishment of the constitution of other ammino-derivatives, and also to the constitution of some of the ammino-salts of divalent and tetravalent metals. 

Nickel salts in aqueous solution are partially precipitated as basic salts on the addition of aqueous ammonia. The precipitate so formed, however, dissolves in excess of ammonia, yielding a blue liquid containing complex ammino-salts. In the dry state the salts rapidly absorb ammonia gas, with formation of ammino-compounds. 

Biltz and Fetkenheuer 1 report the existence of three ammino-compounds, namely, hexammino-nickel chloride, [Xi(NH3)6]Cl2, di ammino-nickel chloride, [Ni(NH3)2]Cl2, and monammino-nickel chloride, [Ni(NH3)]Cl2. Triammino-nickel chloride, [Ni(NH3)3]Cl2, is also described. 

The bromo-derivative, [Pd(C9H7N)2Br2], crystallises in small reddish brown leaflets, and when heated with aqueous ammonia till dissolved, and then treated with hydrochloric or hydrobromic add, the corresponding ammino-compounds are produced.4... 

A. Werner also includes the ammino-compounds or addition compounds of the halides with ammonia, and also compounds of the halides with water. Thus, the compounds PtCl4.2NH3 PtCl2.2NH3 and PtCl4.2H20 are respectively symbolized ... 

F. Ephraim showed that the vol. of the central metal of A. Werner s scheme for representing the constitution of the ammino-compounds, is related with the stability of the compound and A. Jahnsen gives in illustration the hexammino-chlorates M(C103)2.6NH3 ... 

The nature of the bonding forces in ammino compounds which has been discussed above may, in general, be applied to the hydrates. Here the ion-dipole forces occur in addition to the coordinate bond formed by the donation of a pair of electrons by the oxygen atom. We thus obtain structures of the type,... 

Ammonia was found by L. Troost i to unite with ammonium bromide, forming a series of ammino-compounds which are analogous with the corresponding ammino-compounds of ammonium chloride and they are formed in the same manner. Ammonium ammino-bromide, HBr.2NH3, is formed when pulverulent ammonium bromide is exposed to ammonia gas below 5°. The vapour tension is 90 mm. at —27° j 350 mm. at 0° 775 mm. at 14 8° and 1660 mm. at 31°. The absorption of ammonia may continue until a liquid ammonium triammino-bromide,... 

Somewhat similar to hydrolytic adsorption is splitting adsorption in which various complex compounds are disrupted by carbon which selectively adsorbs certain constituent parts. This behavior has been found with complex platinum, palladium, and osmium compounds, also with ammino compounds containing copper, cobalt, manganese, etc.—the metallic group being adsorbed. 

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