2002 AIPMT Coordination CompoundsWriting Formulas from IUPAC Names Easy Question 94 of 104 in Coordination Compounds

The hypothetical complex chlorodiaquatriamminecobalt (III) chloride can be represented as : -

A $[CoCl(NH_3)_3(H_2O)_2]Cl_2$
B $[Co(NH_3)_3(H_2O)Cl_3]$
C $[Co(NH_2)_3(H_2O)_2Cl]$
D $[Co(NH_3)_3(H_2O)_3]Cl_3$

The answer is A.

Solution

Ligands in the name: chloro (one $Cl^-$), diaqua (two $H_2O$), triammine (three $NH_3$). Total coordination number $= 1 + 2 + 3 = 6$.
Co is in the +3 state. Charge on the complex ion $= +3 + (-1) + 0 + 0 = +2$.
So two $Cl^-$ ions are needed outside the coordination sphere to balance the charge (the word 'chloride' at the end).
Formula: $[CoCl(NH_3)_3(H_2O)_2]Cl_2$

Concept Formula from name

Coordination Compounds in past papers

104 questions from this chapter have appeared across 27 exam years.