Question

Two complexes with empirical formula `Co(NH_(3))_(3)(H_(2)O)_(2) Br_(2)CI` exists in two isomeric forms `(A)` and `(B)` Form A gives two moles of AgBr On treatment with `AgNO_(3)` solution whereas form `B` gives only one mole of AgBr Give the structural formula of both these isomers What are these isomer called .

Answer 1

(A) `Co (NH_(3))_(3)(H_(2)O)_(2)Br_(2)CI` gives two moles of AgBr on treatment with `AgNO_(3)` solution hence two `Br^(Θ)` ions are present as counter ion outside the coordination sphere Hence A is `[Co(NH_(3)_(3)(H_(2)O))_(2)CI]Br_(2)`
`Co(NH_(3))_(3)(H_(2)O)_(2)CI]Br_(2)rarr[Co(NH_(3))_(3)(H_(2)O)_(2)CI]^(2+) + 2Br^(Θ)` is present as counter ion i .e `B` is
`[Co(NH_(3)_(3)(H_(2)O))BrC1]Br.H_(2)O`
1 mole of `H_(2)O` will be present outside the coordination sphere as coordination number of `Co^(3+)` ion is 6
`[Co(NH_(3))_(3)(H_(2)O)BrC]Br.H_(2)O`
`rarr[Co(NH_(3))_(3)(H_(2)O)BrCI]^(o+) + Br^(Θ) + H_(2)O`
`Br^(Θ) + AgNo_(3)rarrAgBrdarr+ NO_(3)`
This isomers are (A) `[Co(NH_(3)_(3)(H_(2)O)_(2)CI]Br_(2)` and (B)`[Co(NH_(3))_(3)(H_(2)O)BrCI]BrH_(2)O` .