POLYHALIDES When the halide ions combine with the halogen molecules or interhalogens,univalent ions are obtained .these are known as polyhalide ions and the compounds of these are known as polyhalides . Polyhalide ions: IBr2-, ICl2-, ClBr2-,BrCl2- Polyhalide compounds : kICl4,NaIBr4,NH4IBr2,KI3

Classification I)Simple Polyhalide I2 + I------------- I3- II)Mixed Polyhalide 2F2 + Cl--------- ClF4- Polyhalides with more than two types of halogens are rare. Eg: CsFIBr3,CsFICl,RbFICl3,KClIBr

Preparation: i)The simple polyhalides are prepared by the action of halogens on metallic halides. KI + I2----------- KI3 KI + 2Cl2-------- KICl4 NH4I + 2I2--------- NH4I5

ii) The mixed polyhalide are prepared by the action of halogens or interhalogens on a solid metallic halide CsCl + 2F2-------- CsClF4 NaBr + IBr-------- NaIBr2 KCl + ICl------------ KICl2 iii) Polyhalides may also be obtained by the displacement of halogen with another CsBr3 + I2-------CsIBr2 + IBr KIBr2 + Cl2-------- KICl2 + Br2

Properties: They are coloured compounds having low Melting Points They are generally soluble in H2O,acetone ,alcohol They are ionic compounds and tend to decompose on heating CsI3 -------- CsI+I2 RbIcl2 -------- RbCl + ICl

iv) Replacement properities A halogen in the polyhalide may be replaced by a more E.N. atom,but the central halogen is not replaceable IBr2- + Cl2--------- ICl2- + Br2 v) Action of halogen The halogen may be directly added to the polyhalide ICl2- + Cl2--------- ICl4-