Question

Write the formula for the following coordination compound:
Dichlorodobis(ethane-1,2-diamine) platinum (IV) nitrate.

Answer 1

Hint: Coordination compounds are neutral substances having a metal with one or more ligands. The ligands may be anionic, cationic or neutral. The charge must be balanced on the complex. There are certain rules provided by IUPAC for their naming.

Complete step by step answer:
-As per the IUPAC nomenclature rule, for naming a coordination compound, ligands are first numbered and then mention the metal name with the oxidation state in brackets. For ligands naming such as ionic ligands: chloride is chloride, sulphate is sulphate, nitrate is nitrato, etc. whereas for neutral ligands like water is aqua, carbon monoxide is carbonyl, ammonia is ammine, etc.
-Next is to mention the number and for it, numerical prefixes are used i.e. 1 for mono, 2 for di, 3 for tri, 4 for tetra, 5 for Penta, 6 for hexa and so on. If the overall complex is negatively charged then the metal’s name ends with ‘ate’. For example, iron as ferrate, copper as cuprate, platinum as platinate, gold as aurate, etc. but in case of neutral or positively charged complexes, the metal’s name remains as it is. Such as cobalt will be cobalt in tris(ethane-1,2-diamine) cobalt (III) sulphate where the oxidation state of copper is +3.
-If in the complex, the ligand name has some prefix like di, tri, tetra, then to mention their number prefixes, we use bis for two, tris for three, terakis for four, etc.
-The coordination compound provided to us is Dichlorodobis(ethane-1,2-diamine) platinum (IV) nitrate. From this we can see that there are two ligands directly attached to the central atom platinum. Platinum here has +4 charge. Since it is written the same as its name because it is a positively charged metal.
-The two ligands are chloride and ethane-1,2-diamine and dichorido means two chlorine atoms are present. Bis(ethane-1,2-diamine) clearly states that two atoms of an are present. Since nitrate is written as nitrate only, it is a neutral ligand and must be written outside the big bracket. Also, the charge on the big bracket is +4 so to make it a neutral compound, charge on nitrate must be -4. Since a single nitrate molecule carries -2 charge, taking two molecules of it will make the compound neutral.
-Therefore, the formula of the coordination compound Dichlorodobis(ethane-1,2-diamine) platinum (IV) nitrate is \[[PtC{l_2}{(en)_2}]{(N{O_3})_2}\].

Note:
 There are more rules for nomenclature such as for bridging ligands, \[\mu \] is used as a prefix. The directly attached ligands are always placed before the metal ion. If more than one ligand is present, then they are named in alphabetical order.