Heavy Metal Complexes - Research Paper Example

In coordination chemistry, a complex or a coordination compound consists of a central metal ion with surplus atoms or ions attached (Gharpure) for electrovalent or covalent binding (Gilreath 225). This complex results from the union of an electron-deficient metal with an electron donor (Gilreath 225). The uncharged molecule coordinated to the central metal ion is called a ligand. It is a Lewis base where the atom with which it is directly bonded with is called the donor atom (Gharpure).

Electronegative atoms such as carbon, oxygen, nitrogen, sulfur, and halogens (fluorine, chlorine, bromine, and iodine) are donor atoms (Gilreath 238). To elaborate, in the compound Ag (NH3)2, the two molecules of NH3 are ligands with nitrogen as the donor atom to silver (Ebbing and Gammon 715). Carbon forms cyanide and carbonyl complexes; nitrogen forms ammine, nitroso, nitrito complexes; oxygen forms aquo, hydroxide, oxalate, carhonato complexes; sulfur forms thiocyanate, thiosulfate, sulfide complexes; and halogens form fluoride, chloride, bromide, or iodide complexes. Organic molecules could have at least two coordination positions (Gilreath 239).  When one ammonia molecule coordinates with a proton, it results in an ammonium ion NH4.

In a complex formation of ammonia and copper (II) sulfate, an ammonium atom combines with a water molecule and results in an aqueous solution with hydroxide ion (OH-) and an ammonium ion (NH4 +) while precipitating forms when an hexaaquacopper (II) ions ([Cu(H2O)6]2) combines with two hydroxide ions (2OH-). The protons of the water ligands are removed. When the copper (II) hydroxide precipitate reacts with ammonia molecules, a ligand exchange happens to result in tetraamminediaquacopper(II) ions ([Cu(H2O)6]2++ 4NH3 ⇌ [Cu(NH3)4(H2O)2)]2+ + 4H2O) (“An Equilibrium”).

Only a few ammoniums and hydroxide ions are created by ammonia because it is by nature a weak base. Hydroxide ions may initiate the first reaction with the cation because of the low ammonia concentrations. With higher concentrations of ammonia, on the other hand, precipitates dissolve (Gilreath 241).