Question

Describe briefly the isomerism shown by [Cr(H₂O)₅(NCS)]²⁺.

Answer 1

1. The complex [Cr(H₂O)₅(NCS)]²⁺ shows linkage isomerism.
2. The complex [Cr(H₂O)₅(NCS)]²⁺ exhibits linkage isomerism due to the ability of the NCS⁻ ligand to bind through either N or S atom.
3. This is because the NCS⁻ ligand is ambidentate, meaning it can attach to the metal ion through two different atoms:
   • N-bonded isomer: The thiocyanate ligand binds through its nitrogen atom, forming the thiocyanato-N isomer [Cr(H₂O)₅(NCS)]²⁺.
   • S-bonded isomer: The thiocyanate ligand binds through its sulfur atom, forming [Cr(H₂O)₅(SCN)]²⁺.

Thus, these two isomers have the same overall chemical formula but differ in the specific atom of the ligand that is attached to the central chromium ion.