Question

When a coordination compound $PtC{l_4}.6N{H_3}$ is mixed with $AgN{O_3}$ , 4 moles of AgCl are precipitated per mole of the compound. Write
(a) Structural formula of the complex.
(b) IUPAC name of the complex.

Answer 1

Coordination compound consists of the central metal atom which is usually transition metal and ligands around it. Ligands can be positively charged, negatively charged or neutral molecules. Also, the ligands should have a pair of electrons to donate and form a coordinate bond. The number of moles of AgCl precipitated is equal to the number of chlorines attached through ionic bonds to the complex.

Complete Step by step solution:
Werner postulated Werner's theory which describes the structure and the formation of the coordination compounds. Coordination compounds are also called complex compounds. According to this theory, the central metal atom in the coordination compound has two types of valencies. The two types of the valencies are primary valency and the secondary valency. Primary valency is related to the oxidation state and the secondary valency is related to the coordination number. The number of the secondary valency for every metal atom is fixed. Hence the coordination number for metal atoms is fixed. Primary valency can be satisfied by negative ion and secondary valency is satisfied by either negative ion or neutral molecules.
When the coordination compound given in the question is mixed with silver nitrate, 4 moles of silver chloride are formed. Hence, four molecules of chlorine atoms are present as primary valency. The $N{H_3}$ molecules hence satisfy the secondary valency while chlorine atoms satisfy the primary valency.
The structural formula of the given coordination compound is $\left[ {Pt{{\left( {N{H_3}} \right)}_6}} \right]C{l_4}$ .
Here, $N{H_3}$ molecules are present within the square bracket as they act as ligands satisfying the secondary valency whereas chlorine atoms are present outside the square bracket as they satisfy the primary valency.
IUPAC name of the complex is hexammine platinum(IV) chloride.
Oxidation state of platinum is 4 as four chlorine atoms are present outside the square bracket.

Note:
Coordination compounds find a major application in the homogeneous catalysis for the production of organic substances. Homogenous catalysis refers to reactions where the catalyst is in the same phase as the reactants. Coordination compounds are formed when ligands donate an electron pair to the central atom to form coordinate bonds.