Question

Why is bis (ethylene diammine) zinc (ii) ion is more stable than tetrammine zinc(ii) ion

Answer 1

One significantly elongated Zn and O bond of 2.43 A is being observed in the case of the cis - isomer for one of the H2O ligand located in the trans - position to an NH3 ligand. In the trans isomer , the Zn and O bond length that is observed is 2.23 A, but in the bis ( ethylene diammine )zinc(II) complex, two significant Zn and O bonds, would be 2.12 A for the ligand in the trigonal plane and 2.26 A for axial H2O molecules. As octahedral isomers are transformed into the penta co-ordinated structure, they will be represented as "metastable intermediates", while the bis ( ethylene diammine )zinc(II) complex is the most stable species of the zinc(II)-tetraamine complex in aqueous solution.