Question

IUPAC name of ${\mathrm{K}}_3\left[\mathrm{Fe}{\left({\mathrm{C}}_2{\mathrm{O}}_4\right)}_3\right]$ is:

• A. Potassium dioxalatoferrate$\left(\mathrm{{\rm I}}\right)$
• B. Potassium dioxalatoferrate$\left(\mathrm{{\rm I}{\rm I}{\rm I}}\right)$
• C. Potassium trioxalatoferrate$\left(\mathrm{{\rm I}{\rm I}{\rm I}}\right)$
• D. Potassium trioxalatoferrate$\left(\mathrm{{\rm I}{\rm I}}\right)$

Answer 1

The correct option is C

Potassium trioxalatoferrate$\left(\mathrm{{\rm I}{\rm I}{\rm I}}\right)$

The explanation for the correct option:

Option(C): Potassium trioxalatoferrate$\left(\mathrm{{\rm I}{\rm I}{\rm I}}\right)$

• The name of the cation is given first, followed by the name of the complex ion in a coordination molecule. If an anion is present, its name is written last.
• The names of the ligands are put first, followed by the name of the central metal atom or metal ion when naming a complex ion.
• Ligands are named in alphabetical order of preference without regard for charge or prefixes such as di, tri, and so on.
• If there are numerous ligands of the same kind, numerical prefixes such as di, tri, tetra, Penta, and so on are used to indicate the number of ligands of that type.
• Positive and neutral complexes do not have a defined end. In these circumstances, ligands are named alphabetically, with no hyphen or separation. The name of the central metal is written first, followed by a Roman numeral indicating its oxidation state.
• When a ligand can coordinate through many atoms, the point of attachment is indicated by inserting the donor atom's symbol after the ligand's name, separated by a hyphen. Different names might also be used to identify the attachment.
• In ${\mathrm{K}}_3\left[\mathrm{Fe}{\left({\mathrm{C}}_2{\mathrm{O}}_4\right)}_3\right]$ the central atom or cation is Potassium, with three oxalate ligands and one anion Copper is present.
• Oxidation number of Iron in the compound be “x”. Oxalate carries a $-2$ charge and potassium carries a $+1$ charge.

$$\begin{gathered} +3+\left(\mathrm{x}\right)+(-2)3=0 \\ 3+\mathrm{x}-6=0 \\ \mathrm{x}=+3 \end{gathered}$$

• Therefore name for the compound is Potassium trioxalatoferrate$\left(\mathrm{{\rm I}{\rm I}{\rm I}}\right)$.
• Hence it is the correct option.

The explanation for incorrect option(s):

Option(A): Potassium dioxalatoferrate$\left(\mathrm{{\rm I}}\right)$

• The compound has three oxalate ligands so the prefix used will be “tri”.
• Also the oxidation number of iron is $+3$
• Hence it is an incorrect option.

Option(B): Potassium dioxalatoferrate$\left(\mathrm{{\rm I}{\rm I}{\rm I}}\right)$

• The prefix “di” is used when we have two same kinds of ligands but here we have three oxalate ligands.
• Hence, it is an incorrect option.

Option (D): Potassium dioxalatoferrate$\left(\mathrm{{\rm I}{\rm I}{\rm I}}\right)$

• The oxidation number of iron is $+3$
• Hence, it is an incorrect option.

Therefore, the IUPAC name for ${\mathrm{K}}_3\left[\mathrm{Fe}{\left({\mathrm{C}}_2{\mathrm{O}}_4\right)}_3\right]$ is Potassium trioxalatoferrate$\left(\mathrm{{\rm I}{\rm I}{\rm I}}\right)$.