Editing Cobalt(II) chloride (section)

===Complexed chlorides===
The hexahydrate and the anhydrous salt are weak [[Lewis acid]]s.  The [[adduct]]s are usually either [[octahedral]] or [[tetrahedral]]. It forms an [[metal-pyridine complex|octahedral complex with pyridine]] ({{chem|C|5|H|5|N}}):<ref name=Long>{{cite journal |doi=10.1021/ic50184a002|title=Crystal and Molecular Structures of ''trans''-Tetrakis(pyridine)dichloroiron(II), -Nickel(II), and -Cobalt(II) and ''trans''-Tetrakis(pyridine)dichloroiron(II) Monohydrate|year=1978|last1=Long|first1=Gary J.|last2=Clarke|first2=Peter J.|journal=Inorganic Chemistry|volume=17|issue=6|pages=1394–1401}}</ref>
:{{chem|CoCl|2}}·6{{chem|H|2|O}} + 4 {{chem|C|5|H|5|N}}  →  {{chem|CoCl|2|(|C|5|H|5|N|)|4}} + 6 {{chem|H|2|O}}
With [[triphenylphosphine]] ({{chem|P(C|6|H|5|)|3}}), a tetrahedral complex results:
:{{chem|CoCl|2}}·6{{chem|H|2|O}} + 2 {{chem|P(C|6|H|5|)|3}} → {{chem|CoCl|2|[P(C|6|H|5|)|3|]|2}} + 6 {{chem|H|2|O}}

Salts of the anionic complex CoCl<sub>4</sub><sup>2−</sup> can be prepared using tetraethylammonium chloride:<ref>{{cite book|author = Gill, N. S.|author2 = Taylor, F. B.| title=[[Inorg. Synth.|Inorganic Syntheses]] | chapter=Tetrahalo Complexes of Dipositive Metals in the First Transition Series |name-list-style = amp|year = 1967|volume = 9|pages = 136–142|doi = 10.1002/9780470132401.ch37|isbn = 9780470132401}}</ref>
:{{chem|CoCl|2}} + 2 [(C<sub>2</sub>H<sub>5</sub>)<sub>4</sub>N]Cl → [(C<sub>2</sub>H<sub>5</sub>)<sub>4</sub>N)]<sub>2</sub>[CoCl<sub>4</sub>]
The tetrachlorocobaltate ion [CoCl<sub>4</sub>]<sup>2−</sup> is the blue ion that forms upon addition of [[hydrochloric acid]] to aqueous solutions of hydrated cobalt chloride, which are pink.