CS 2 ) 2 . Another complex symmetrical pseudohalogen is dicobalt octacarbonyl , Co 2 (CO) 8 . This substance can be considered as a dimer of the hypothetical cobalt tetracarbonyl, Co(CO) 4 . Examples of non-symmetrical pseudohalogens ( Ps –X) are cyanogen halides ( ICN , ClCN , BrCN ),