Question

The formula of \[potassium\text{ }dicyanobis~\left( oxalato \right)\text{ }nickelate\left( II \right)\]is
A. ${{K}_{4}}[Ni{{(CN)}_{2}}{{(ox)}_{2}}]$
B. ${{K}_{3}}[N{{i}_{2}}({{[N{{i}_{2}}CN)}_{2}}{{(ox)}_{2}}]$
C. $K[Ni(CN){{(ox)}_{2}}]$
D. ${{K}_{2}}[Ni{{(CN)}_{2}}{{(ox)}_{2}}]$

Answer 1

Hint: The given question is related to the IUPAC nomenclature of coordination compounds. Since the attacking element is a metal, we know that in the compound, a complex is forming the anionic part. So, accordingly we’ll use the rules to write the formula.

Complete Step by Step Solution:
A coordination complex is made up of a core atom or ion, known as the coordination centre, which is typically metallic, and an array of attached molecules or ions that are known as ligands or complexing agents. It can be of two types, one in which the attacking group acts as an anionic part and the complex is acting as the cationic part or the other one in which the attacking group acts as a cation and complex acts as an anion.
The nomenclature rules are as follows:
In the nomenclature of complicated coordination complexes, the ligands are always written before the main metal ion.
The alphabetical order of the ligand names when the coordination centre is bound to many ligands is unaffected by the numerical prefixes that must be applied to the ligands.
Prefixes of the type di-, tri-, tetra-, and so on provide information about the number of ligands when there are numerous monodentate ligands present in the coordination molecule.
The prefixes are of the type bis-, tris-, and so forth when the core metal ion has several polydentate ligands linked to it.
The letter "o," which typically takes the place of the letter "e," must terminate the names of the anions that are present in a coordination complex. The chloride anion must be expressed as "chlorido," and the sulphate anion must be written as "sulfato."
In coordination compounds, the neutral ligands $N{{H}_{3}}$ (ammine), ${{H}_{2}}O$ (aqua or aquo), CO (carbonyl), and NO are given special names (nitrosyl).
The name of the principal metal atom is written after the ligands have been identified. The prefix "-ate" is added if the complex carries an anionic charge.
Priority is given to the Latin name of the metal when writing the name of the central metallic atom in an anionic complex, if one exists (with the exception of mercury).
Roman numerals contained in a set of parenthesis must be used to indicate the oxidation state of the central metal atom/ion.
The cationic entity must be written before the anionic entity if the coordination molecule is accompanied by a counter ion.
After adhering to the rules of nomenclature we can conclude that the formula for \[potassium\text{ }dicyanobis~\left( oxalato \right)\text{ }nickelate\left( II \right)\] is ${{K}_{4}}[Ni{{(CN)}_{2}}{{(ox)}_{2}}]$
Hence, the correct option is A. ${{K}_{4}}[Ni{{(CN)}_{2}}{{(ox)}_{2}}]$

Note: The most important thing to note here are the nomenclature rules of coordination complexes. Don’t forget to find out the correct oxidation state of the central metal atom which is to be written in roman.