Coordination compounds
The coordination compounds are very important in biological systems (like human, plant and animal's body), metallurgy, analytical chemistry, medicine etc. Chlorophyll, Hemoglobin, vitamin B12 etc. are coordination compounds of various metals. They are also called complex compounds and formed by two main entities, metal and ligands. Some ligands are Poly-dentate, like EDTA, which is used in the estimation of hardness of water with Ca2+ and Mg2+ ions. Gold and silver make [Au(CN)2]− and [Ag(CN)2]− type complex ions in aqueous solution during extraction of metals. In photography, developing film form a complex ion [Ag (S2O3)2]3−. A complex compound of platinum (Pt), cis-platin is used in the treatment of cancer. Some metals can be refined by making their complex compounds, like impure Nickel is converted to [Ni(CO)4] complex. All these coordination compounds may be colored or colorless, paramagnetic or diamagnetic, low spin or high spin, and arranged in particular geometry and hybridization. Isomerism is shown by these complexes due to different arrangement of ligands around the central metal atom.
What is IUPAC name of complex ion [Ag(CN)2]- ?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Dicyanidoargentate(I) ion
In IUPAC naming of a complex ion, the ligands are named first and then the metal. The anionic ligand \( \ce{CN^{-}} \) is named cyanido, with di- for two ligands. The oxidation state of the metal is shown in Roman numerals. In an anionic complex, the metal name ends in “-ate”, and silver takes its Latin name, argentate.
For the oxidation state of silver in \( \ce{[Ag(CN)2]^{-}} \):
\( \displaystyle x+2(-1)=-1\ \Rightarrow\ x=+1 \)
So the name is dicyanidoargentate(I) ion.
Why the other options are incorrect
Option (1) Dicyanosilverate (I) ion — Incorrect. In anionic complexes, silver is always named by its Latin name, argentate; “silverate” is never used. Also, the ligand must be named cyanido, not cyano.
Option (2) Dicyanosilverate(II) ion — Incorrect. Silver is in the +1 state, not +2, and the name must use argentate.
Option (4) Dicyanidoargentate(II) ion — Incorrect. The name is correct except the oxidation state: silver is +1 here, not +2.
NCERT (2026-27 edition):
Naming of Mononuclear Coordination Compounds – …
Naming of Mononuclear Coordination Compounds – “… 3. [Ag(NH3)2][Ag(CN)2] is named as: diamminesilver(I) dicyanidoargentate(I)”