Contiguration of Aquotri- and diammine Cobalt Couiplexes. 



13 



From thi^j. it seems to he a rule that the cohaltammine in 

 which the two clilorine atoms are coöidinated in tlie trans-position 

 is green in colour. 



When one of tlie water molecules is replaced hy a chlorine 

 atojn hy the direct action of concentrated hydrochloric acid upon 

 [Co CI (H.Ojg (NHg).] SO^, a green salt is produced which corresponds 

 to the formula [Co Cl^ (H.O)^ (NHg)^ CI. This salt is soluble in 

 water, thereby changing its colour to violet. Werner ^'^ supposed 

 this salt to be the isomer of the above [Co Cl^ (HsO)2 (NHg^] X (III). 

 If tluit be correct, we are inclined to the view that the two 

 chlorine atoms of the salt codrdinate in the cis-position as shown: 



H,0. 

 SOi + HCl 



r 



H.,0 



n.o 



NFL, 



H„0' 



CI 



CI 



In supporting this statement, this salt should be regarded 

 as one of the excejDtions to the general rule that the cobaltammines 

 in which the two chlorine atoms coordinate in th,e trans, are, as 

 already described, green coloured. But is it not mere prol)al)le 

 that this salt is identical with [Co CI, (H20),(NH3)JX sliown by (III) 

 and that the two chlorine atoms are situated in the trans-position ? 

 So I suggest that the formula of tlie salt may be : 



ci 



Up to this point, I liave determined tlie configurations of 

 the isomers of [Co (NHg}^ H,0 Cy X, [Co (NH.}, (K/))^ CI] X. and 

 [Co (NH3)3 (H^OM X3 respectively and [Co (NH,)., (H./J), CL,] X, 

 [Co (NHg)., (H.,0)3 CI] X, and [Co (NHs),, (NO^IJ, l)ut this is not sufficient 

 without an explanation of the study of tlie absoi'ption spectra. 



(1) Zeit, aaorg. Chein., 15, 172, 1897. 



