(N/A) Industrial processes: Coordination compounds are used as catalysts for many industrial processes. For example,the Wilkinson catalyst,$[(Ph_{3}P)_{3}RhCl]$,is used for the hydrogenation of alkenes.
Biological systems:
$1$. Chlorophyll,the green pigment responsible for photosynthesis,is a coordination compound of magnesium.
$2$. Haemoglobin,the red pigment of blood that acts as an oxygen carrier,is a coordination compound of iron.
$3$. Vitamin $B_{12}$ (cyanocobalamin),the anti-pernicious anaemia factor,is a coordination compound of cobalt.
$4$. Carboxypeptidase-$A$ and carbonic anhydrase are essential metalloenzymes of zinc that act as catalysts in biological systems.