Question

Write the IUPAC names of the following coordination compounds:
i) \([Pt(NH_3)_2ClNO_2]\)
ii) \([Co(NH_3)_5(CO_3)]Cl\)
iii) \([Ni(CO)_4]\)
iv) \([Co(NH_3)_5ONO]^{2+}\) (1+1+1+1)

Hint:

Name ligands alphabetically then the metal with its oxidation state; remember \(NO_2\) bonded through N is nitrito-N (nitro) while ONO bonded through O is nitrito-O.

Answer 1

Rule used: In a coordination compound the ligands are named first in alphabetical order (by ligand name, ignoring the multiplying prefixes di, tri, tetra), then the central metal, followed by its oxidation state in Roman numerals in brackets. For a cationic complex the counter-anion is written after the complex ion.

i) \([Pt(NH_3)_2ClNO_2]\): Ligands are 2 ammine (\(NH_3\), neutral), 1 chlorido (\(Cl^-\)), 1 nitrito-N (\(NO_2^-\), bonded through N).
Charge balance: complex is neutral, so \(x + 0 + (-1) + (-1) = 0 \Rightarrow x = +2\).
Alphabetical ligand order: ammine, chlorido, nitrito.
Name: Diamminechloridonitrito-N-platinum(II).

ii) \([Co(NH_3)_5(CO_3)]Cl\): Ligands are 5 ammine (neutral) and 1 carbonato (\(CO_3^{2-}\)); \(Cl^-\) is the counter-ion.
Complex ion charge \(= +1\) (to balance one \(Cl^-\)); so \(x + 0 + (-2) = +1 \Rightarrow x = +3\).
Alphabetical order: ammine, carbonato.
Name: Pentaamminecarbonatocobalt(III) chloride.

iii) \([Ni(CO)_4]\): Four carbonyl ligands (CO, neutral); complex is neutral, so oxidation state of Ni \(= 0\).
Name: Tetracarbonylnickel(0).

iv) \([Co(NH_3)_5ONO]^{2+}\): Ligands are 5 ammine (neutral) and 1 nitrito-O (ONO, bonded through O, \(-1\)).
Charge balance: \(x + 0 + (-1) = +2 \Rightarrow x = +3\).
Name: Pentaamminenitrito-O-cobalt(III) ion.