Q. Explain about Extraction of metals?

Extraction of metals is very often done by complex formation. For example, the cyanide process for the extraction of silver and gold is well known. Purification of metals is often accomplished by solvent extraction of neutral complexes. Commonly encountered ligands for such purposes are oxine, acac, dmg, salicylaldoxime or salicyldineimines. The role of complexes as catalysts in the production of organic chemicals is yet another field of importance. For example various complexes of copper, silver, mercury, ruthenium, cobalt etc. are known to be good catalysts for hydrogenation process [RhCI (PPh₃)₃], tris (tripheny1phoshine) chlororhodium(1) is one of the best known and thoroughly  investigated compounds. Similarly, oxidation, polymerisation, hydroformylation of olefins all involve the formation of complexes as intermediates. However, quite often they are not simple complexes rather they are organometallic compounds.