Rules for
Nomenclature of Complexes
1. Split the complex molecule into its cation
and anion.
2. In complex,
cation is named first, followed (after a space) by the name of the anion
(regardless of which is the complex ion)
3. In complex
ion (whether cation or anion) or in neutral complex, all ligands are named
first [which are listed together as one word without any separation by hyphens]
followed by the name of the central atom with its oxidation state in roman numerals
in parenthesis. The suffix –ate is used in name of central atom (can use the Latin root) in case of –ive
complex ion before the oxidation state. [The
name of central atom is unchanged in case of cationic complex or neutral
complex]. e.g.
4. All ligands
are listed in alphabetic order. If there are two or more ligands of the same
type (say negative), these are listed in alphabetic order (disregarding the
prefixes).
(a) Names of negative ligands are written as
ending in –O. If the name of the
compound ligands ends with –ide, –ite or –ate, it is changed respectively to
–ido, –ito or –ato. [For some simple ligand, the ending –ide is changed simply
to –O e.g. F– – Fluoro, OH¯ – Hydroxo].
Ligands or Co-ordinating Groups and its Types
Ambidentate Ligand
The ligands that can legate through two different
atoms present in its molecule to central atom or ion are called Ambidentate
Ligand. Some ambidentate ligands are NO2–, SCN–
or NCS– etc.
1. The
ligand NO2– can
attach itself through N (as – NO2–) as well as through O (as ONO–). The – NO2– is named as nitro and ONO– is named as nitrito.
2. The
ligand CNS– may get attached through S (as – SCN–)
or through N (as – NCS–). The ligand – SCN– is
named as thiocyanato or thiocyanato–S and the ligand – NCS– is
named as isothiocyanato or thiocyanatio–N.
Classification
of Ligands According to Charge
According
to charge, ligands are of three types namely anionic, neutral and cationic
ligands. The name of anionic ligands end in –O while cationic ligand have suffix –ium.
1. Anionic Ligands or Negative Ligands
2. Neutral Ligands or Molecular Ligands
3. Cationic Ligands or Positive Ligands
Anionic
Ligands or Negative Ligands
The ligands which carry negative charge on them are called
anionic ligands. Anionic ligands generally form anionic complex ions. If the
name of the ligands end –ide, –ite, or –ate , it is changed respectively to
–ido, –ito, or –ato. For some simple ligands, the ending –ide is changed simply
to –O. e.g.
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