Question

Using IUPAC norms, write the systematic names of the following: (i) [Co(NH$_3$)$_6$]Cl$_3$
(ii) K$_3$[Cr(C$_2$O$_4$)$_3$]
(iii) [Pt(NH$_3$)$_2$Cl$_2$]
(iv) [Ni(CO)$_4$]

Hint:

Always name ligands before the central atom, use alphabetical order for multiple ligands, and indicate the oxidation state of the central metal in Roman numerals.

Answer 1

(i) [Co(NH$_3$)$_6$]Cl$_3$:
Ligand: NH$_3$ = ammine (neutral)
Central atom: Cobalt
Oxidation state of Co: \(x + 0 = +3 \implies x = +3\)
Name:
Hexaamminecobalt(III) chloride (ii) K$_3$[Cr(C$_2$O$_4$)$_3$]:
Ligand: C$_2$O$_4^{2-}$ = oxalato (bidentate)
Central atom: Chromium
Oxidation state of Cr: \(x + 3(-2) = -3 \implies x = +3\)
Name:
Potassium trioxalatochromate(III) (iii) [Pt(NH$_3$)$_2$Cl$_2$]:
Ligands: NH$_3$ = ammine (neutral), Cl$^-$ = chloro
Central atom: Platinum
Oxidation state of Pt: \(x + 0 + (-1)\times 2 = 0 \implies x = +2\)
Name:
Diamminedichloroplatinum(II) (iv) [Ni(CO)$_4$]:
Ligand: CO = carbonyl (neutral)
Central atom: Nickel
Oxidation state of Ni: \(x + 0 = 0 \implies x = 0\)
Name:
Tetracarbonylnickel(0) Conclusion:
The names of coordination compounds are given by mentioning ligands first (in alphabetical order), followed by the central metal with its oxidation state in Roman numerals.