Open Access1: 2: 3—Triaminopropane and its complex metallic compounds
Author(s) -
Frederick G. Mann,
William Jackson Pope
Publication year - 1925
Publication title -
proceedings of the royal society of london. series a, containing papers of a mathematical and physical character
Language(s) - English
Resource type - Journals
eISSN - 2053-9150
pISSN - 0950-1207
DOI - 10.1098/rspa.1925.0006
Subject(s) - octahedron , chemistry , crystallography , chloride , group (periodic table) , stereochemistry , organic chemistry , crystal structure
The co-ordination theory of Werner (‘Ann.,’ vol. 322, p. 261 (1902)) has led to a great advance in our knowledge of complex metallic compounds; as applied to such compounds as hexamminocobaltic chloride [Co(NH3 )6 ]Cl3 , it involves the assumption that the six component ammonia groups are situate at the apices of a regular octahedron of which the cobalt atom occupies the centre, and that the complex so constituted—the co-ordinated group—acts as a tribasic ion which combines as a whole with three equivalents of an acidic radicle. For the purpose of discussing the possibilities of geometrical arrangement of the component parts of a co-ordinated group, it will be convenient to number the octahedron apices in the following manner. The outline of the plan of a regular octahedron on one of its triangular faces is bounded by a regular hexagon, each apex of which represents an angular point of the octahedron; let these latter points be numbered consecutively from one to six. On the basis of this nomenclature the isomeric praseo- and violeo-compounds of the composition, [Co(NH3 )4 Cl2 ]Cl, become, respectively, the 1 : 2 : 4 : 5- tetrammino-3 : 6-dichlorocobaltic chloride and the 1 : 2 : 3 : 5-tetrammino- 4 : 6-dichlorocobaltic chloride. Werner’s theory indicates the possibility of stereoisomerism, accompanied by optical activity, when certain of the six ammonia groups in hexamminocobaltic chloride are replaced by differently constituted radicles; in this respect a close correspondence has been observed between theoretical anticipation and experimental results. A similar concordance between prevision and realisation has been found among compounds in which pairs of ammonia groups in the hexamminocobaltic chloride are replaced each by one molecule of ethylenediamine; theory indicates that thetere thylenediaminecobaltic chloride, [Co(NH2 .CH2 .CH2 .NH2 )3 ]Cl3 , should be resolvable into enantiomorphously related components which contain the 1 : 2, 3 : 4, 5 : 6- and the 2 : 3, 4 : 5, 6 :1-tere thylenediaminecobaltic co-ordinated groups respectively, and salts of these two optically active radicles have been prepared.