A chloride of fourth group cation in qualitative analysis gives a green coloured complex [A] in acqueous solution which when treated with ethane-1, 2-diamine (en) gives pale yellow solution [B] which on subsequent addition of ethane-1, 2-diamine turns to blue/purple [C] and finally to violet [D]. Write the structures of complexes [A], [B], [C], and [D]

Explanation

In fourth group of qualitative analysis containing `Ni^(2+), Co^(2+), Zn^(2+)` and `Mn^(2+)`, the green coloured complex in aqueous solution is formed only by `Ni^(2+)`, i.e., A = `[Ni(H_(2)O)_(6)]^(2+)`
`[Niunderset(("A"))((H_(2)O)_(6))]^(2+)+enrarr[Niunderset(("B"))((H_(2)O)_(4))en]^(2+)overset(+en)rarr[Niunderset(("C"))((H_(2)O)_(2))(en)_(2)]^(2+)overset(+en)rarr[Niunderset(("D"))((en)_(3))]^(2+)`