Class 12 Chapter 9 Coordination compounds

 INTRODUCTION

We know that transition metals form a large number of complex compounds in which the metal atoms are bound to a number of anions or neutral molecules by sharing electrons. These compounds are also called coordination compounds because they contain coordinate bonds. The chemistry of coordination compounds is an important and challenging area of modern inorganic chemistry. New concepts of chemical bonding and molecular structure have provided insights into the functioning of these compounds as vital components of biological systems. Chlorophyll, haemoglobin and vitamin B12 are naturally occurring coordination compounds of magnesium, iron and cobalt respectively. Coordination compounds are used in a variety of metallurgical processes, as industrial catalysts and analytical reagents. Coordination compounds also find many applications in electroplating, textile dyeing and medicinal chemistry.

The Swiss chemist Alfred Werner (1866-1919), was the first to formulate his ideas about the structures of coordination compounds. He synthesized and characterised a large number of coordination compounds and studied their physical and chemical behaviour by simple experimental techniques. Werner proposed the concept of a primary valence and a secondary valence for a metal ion. Binary compounds like CrCl₃, CoCl₂ or PdCl₂ have a primary valences of 3, 2 and 2 respectively. In a series of compounds of cobalt (III) chloride with ammonia, it was found that some of the chloride ions could be precipitated as AgCl by adding excess silver nitrate solution in cold but some remained in solution.

CONTENT

Werner’s Theory of Coordination Compounds

Definitions of Some Important Terms Pertaining to Coordination Compounds

Nomenclature of Coordination Compounds

Isomerism in Coordination Compounds

Bonding in Coordination Compounds

Bonding in Metal Carbonyls

Importance and Applications of Coordination Compounds