Complex Ions

Complex ions generally contain transition metals like iron, cobalt, nickel, copper, zinc, and silver. If you see these metals as a reactant, there is a good chance you will have a complex ion being formed. Complex ions need an excess of concentrated substance containing the ligand (the non-metal in the ion).

How to write… 1.Write the reactants 2.On the product side, open a set of brackets [] 3.Put the metal ion in the brackets first, then add parenthesis [ M ion ()] 4.Next put a subscript on the parenthesis that is twice the charge on the metal. For a +2 metal the subscript is 4. [M² ()].

How to write cont. 5. Finally, place the ligand inside the parentheses and do the math to get the charge. -If the ligand is ammonia or water, the ligand is neutral, so the example ion has an overall charge of +2. [M²()]². -If the ligand is a hydroxide or a halide (neg 1 charge), the example ion will be [M²()]².

Common Metals and Ligands Common complex ion metals (Lewis acids): – Fe, Co, Ni, Cr, Cu, Zn, Ag, and Al Common complex ligands (Lewis bases): – NH, CO², CN, HO, OH, Cl, SCN

Naming Complex Ions Add an o to anion when ligand – Cyanide becomes cyano, oxalate becomes oxalato, chloride becomes chlorido If overall complex ion is negative, use the –ate ending on the name – [Fe(CO)] tetraoxalatoferrate (II) Anything after the ion is named as normal – [Zn(NH)]Cl tetraamminezinc chloride

A couple of examples An excess of concentrated ammonia solution is added to freshly precipitated copper(II) hydroxide. – NH + Cu(OH) [Cu(NH)]² + OH A solution of diamminesilver chloride is treated with dilute nitric acid. – [Ag(NH)] + Cl + H AgCl + NH