Complex Ions

1. Complex Ions

2. 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).

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

4. 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. [M⁺²()₄]⁺². -If the ligand is a hydroxide or a halide (neg 1 charge), the example ion will be [M⁺²()₄]⁻².

5. Common Metals and Ligands • Common complex ion metals (Lewis acids): • Fe, Co, Ni, Cr, Cu, Zn, Ag, and Al • Common complex ligands (Lewis bases): • NH₃, C₂O₄²⁻, CN⁻, H₂O, OH⁻, Cl⁻, SCN⁻

6. 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(C₂O₄)₄]⁶⁻ tetraoxalatoferrate (II) • Anything after the ion is named as normal • [Zn(NH₃)₄]Cl₂ tetraamminezinc chloride

7. A couple of examples • An excess of concentrated ammonia solution is added to freshly precipitated copper(II) hydroxide. • NH₃ + Cu(OH)₂  [Cu(NH₃)₄]²⁺ + OH⁻ • A solution of diamminesilverchloride is treated with dilute nitric acid. • [Ag(NH₃)₂]⁺ + Cl⁻ + H⁺  AgCl + NH₄⁺