Question

Pick the correct name of $\left[ {Co{{\left( {N{H_3}} \right)}_5}Cl} \right]C{l_2}$ ​
a) Chloropentammine cobalt (III)
b) Pentammine cobalt (III) chloride
c) Chloropentammine cobalt (III) chloride
d) Pentaamminechloridocobalt(III)dichloride

Answer 1

A complex is basically a substance in which a metal ion or atom is linked with either a group of neutral molecules or anions known as ligands. And coordination compounds are the neutral substances (means no charge) in which at least one ion is present in the form of a complex.

Complete step by step solution:
IUPAC provides consistency to the names of coordination or organic compounds. It enables every compound to possess a unique name, which otherwise is not plausible with the common names. Keep certain points in mind while naming the coordination compounds:
In order to assign a name to a coordination compound, always name cation before anion. It doesn’t matter whether the complex ion is cation or anion.
In order to assign a name to the complex ion, assign name to the ligands first in an alphabetical order, then metal ion or atom. It should be kept in mind that the metal ion or atom is always written before ligands in the chemical formula.
Greek prefixes are generally used to designate the number of ligands in the complex e.g. di-, tri- or tetra-. If the ligand already comprises of a Greek prefix or if it is a polydentate ligand (i.e. it can connect to more than one binding site) then, the prefixes like bis-, tris-, tetrakis- or pentakis-, are used.
The given compound i.e. $\left[ {Co{{\left( {N{H_3}} \right)}_5}Cl} \right]C{l_2}$ is a coordination complex as it forms a chloride salt.
In this coordination compound, there are five amine ligands i.e. $N{H_3}$ so we will use pentaammine in the name. $N{H_3}$ is a neutral molecule so the oxidation number will be zero. Apart from this, there is one anionic ligand i.e. chloride $C{l^ - }$ which is written as either chloro or chlorido. So, the name the ligands can be named as pentaamminechlorido or pentaamminechloro.
The central metal cation is cobalt with an oxidation state of 3 in the present case.
Thus, the IUPAC name of $\left[ {Co{{\left( {N{H_3}} \right)}_5}Cl} \right]C{l_2}$ becomes Pentaamminechloridocobalt(III)dichloride.
Hence, the correct answer is Option D.

Note:
IUPAC nomenclature creates a standardized method to name the chemical compounds. Common nomenclature employs the older names for organic compounds rather than using the prefixes for the carbon chain. IUPAC nomenclature even provides certain rules for the naming of ions as well.