Unidentate: When the ligands can donate the pair of electrons from one atom, it is called unidentate ligands, e.g., NH3, H2O, CN– etc.
Didentate : When the ligand can donate the pair of electrons through two atoms of the ligand, it is called didentate ligand.
Ambidendate: It is that unidentate ligand which can ligate through two different atoms present in it to central atom/ion giving two different coordination entity. Examples are NO2– and SCN– ions. NO2– can ligate through either N or O atom and SCN can ligate through S or N atom to central atom/ion of coordination entity. This results into formation of linkage isomers.
For example : NO2– group can do coordination to metal ion through or atom forming nitro complex or through oxygen atom forming nitrito complex.
[Co(NH3)5(–NO2)]2+ and [Co(NH3)5(–ONO)]2+.
A solution of [Ni (H2O)6]2+ is green but a solution of [Ni(CN)4]2– is colourless. Explain.
What will be the correct order for the wavelength of absorption in the visible region for the following:
[Ni (NO2)6]4–, [Ni(NH3)6]2+, [Ni(H2O)6]2+?
Out of the following two coordination entities which is chiral (optically active)?
(a) cis-[CrCl2(ox)2]3+
(b) [trans-[CrCl2 (ox)2]3–
