Mesotomisation. of Diammine-dinitrc-oxalo-cobalt Compley. 5 



diamine-cobalt complex [CoeiiaCOa]' belong to the type of mole- 

 cular asymmetry I, while triethylene-diamine-cobalt complex 

 [Coeiis] " and trioxalo-chrominm complex [01(0204)3] " belong to 

 that of molecular asymmetry II. 



Now, it will be noticed that the optical activity of diammine- 

 dinitro-oxalo-cobalt complex is due not to the asymmetry of the 

 cobalt atom but to a molecular asymmetry, the central cobalt atom 

 in this complex ion which may be expressed by the general formula 

 [CoEsFoD^^]' being by no means asymmetric, as is the case with 

 [Coen.NOo-Cl]', [Coena-NHs-Br]" etc [compare A. Werner, Ber., 

 44, L'^S" and 2445, 1911]. This new type of molecular asjamnetry 

 to which attention has just been called is, therefore, to be in- 

 troduced into the stereocliemistry of inorganic complex compounds 

 and, in extension of Werner's classification, it may be called the 

 type of molecular asymmetry III. 



Experimental. 

 1) Preparation of Barium Diammine-dinitro-oxalo-coballiale. 



To start with, ammonium diamrnine-tetranitro-cabaltiate 

 [Co(NH3)-2(N02)4]NH4 was first of all prepared according to the 

 method described by Jörgensen \^Zeitsch. anorg. Chem., 17, 476, 

 1898], this substance having the advantage of being easily con- 

 verted into the l)arium salt and the barium salt being required in 

 later operations. 



The large yellowisli-brown coloured crystals of the ammonium 

 salt thus obtained were carefully purified by repeated recrystallisa- 

 tion, and subsequent!}" converted into ammonium diammine- 

 'dinitro-oxalo-cobaltiate [Co(NH3)2(N02)2C204]NH4 by the action 

 of oxalic acid upon a concentrated aqueous solution of the original 

 salt [Jörgensen, Zeitsch. anorg. Chem., 11, 440, 1896]. 



The oxalo-complex thus obtained was then dissolved in 

 wate]', and finely pulverised barium chloride was added in portions. 

 When one molecular proportion of barium chloride was added to 

 two molecular proportions of the complex, barium diammine- 

 dinitro-oxalo-cobaltiate began to crystallise out from the solution 



