The hexahydrate and the anhydrous salt are weak Lewis acids.  The adducts are usually either octahedral or tetrahedral. It forms an octahedral complex with pyridine ():
With triphenylphosphine (), a tetrahedral complex results:
Salts of the anionic complex CoCl can be prepared using tetraethylammonium chloride:
: + 2 [(CH)N]Cl → [(CH)N)][CoCl]
The tetrachlorocobaltate ion [CoCl] is the blue ion that forms upon addition of hydrochloric acid to aqueous solutions of hydrated cobalt chloride, which are pink.