Question

Write IUPAC name of the following coordination compound $\left[ {{\text{Co}}{{\left( {{\text{N}}{{\text{H}}_3}} \right)}_5}{\text{Cl}}} \right]{\text{C}}{{\text{l}}_2}$.

Answer 1

To answer this question, you should recall the rules of IUPAC naming of coordination compounds. Coordination compounds are chemical compounds that consist of an array of anions or neutral molecules that are bound to a central atom via coordinate covalent bonds.

Complete Step by step solution:
- Coordination compounds are molecules that possess one or multiple metal centers that are bound to ligands. These complexes can be neutral or charged. When the complex is charged, it is stabilized by neighboring counter-ions.
- A complex ion has a metal ion at its center with a number of other molecules or ions surrounding it. These can be considered to be attached to the central ion by coordinate bonds and in some cases, the bonding is actually more complicated than that. The molecules or ions surrounding the central metal ion are called ligands. The standard rules that must be followed in the nomenclature of coordination compounds are described below:
- The ligands are always written before the central metal ion in the naming of complex coordination complexes.
- The names of the anions present in a coordination compound must end with the letter ‘o’, which generally replaces the letter ‘e’. Therefore, the sulfate anion must be written as ‘sulfato’ and the chloride anion must be written as ‘chlorido’.
- After the ligands are named, the name of the central metal atom is written. If the complex has an anionic charge associated with it, the suffix ‘-ate’ is applied.
- The oxidation state of the central metal atom/ion must be specified with the help of roman numerals that are enclosed in a set of parentheses. If the coordination compound is accompanied by a counter ion, the cationic entity must be written before the anionic entity. Using the above rules the IUPAC name of the above compound can be written as:

Pentaammine chloro cobalt (III) chloride.

Additional information:
The coordination compounds formed by the transition elements are coloured due to the presence of unpaired electrons that absorb light in their electronic transitions. For example, the complexes containing iron (II) can exhibit green and pale green colours, but the coordination compounds containing iron (III) have a brown or yellowish-brown colour. When the coordination centre is a metal, the corresponding coordination complexes have a magnetic nature due to the presence of unpaired electrons. Coordination compounds exhibit a variety of chemical reactivity. They can be a part of inner-sphere electron transfer reactions as well as outer-sphere electron transfers. Complex compounds with certain ligands have the ability to aid in the transformation of molecules in a catalytic or a stoichiometric manner.

Note: You should know the surrounding atoms, ions and molecules around the central transition metal ion are known as Ligands. They act as Lewis base and donate electron pairs to transition metal ions, thus a dative bond is formed between ligands and the transition metal ion. Hence these compounds are coordination complexes.