The
formula for a coordination complex has the symbol for
metal followed by formulae
for the
ligands coordinated to it.
The number of ligands is given by subscripts in the usual manner.
To avoid confusion polyatomic ligands are enclosed in brackets even if only one is present.
The order of the ligands in the formula is alphabetical according to the representation of the ligand being used.
PtCl2(NH3)2 is the formula for diamminedichloridoplatinum(II), a coordination complex that has no charge.
The example given above shows that
in the name for the complex the names of the
ligands precede the name of the
metalligands that are
anions have the
ide in their name replaced by
ido (
chlorido in the example above)**
ligands that are
molecules have the same name as the molecule
except that H2O is aqua and NH3 is ammine (double m as in ammonia) (see ammine in example above).
the
number of ligands are indicated by Greek prefixes
di (2), tri (3), tetra (4), penta (5), hexa (6)
the
ligands appear in
alphabetical order irrespective of the prefix.
Note that this means that the sequence of ligands in the formula and the name may be different as for the PtCl
2(NH
3)
2 shown above!!!
**The International Union of Pure and Applied chemistry now recommends use of -ido for anionic ligands that have -ide in their name (thus chloride would be designated as chlorido-). This is to distinguish the cases where the monatomic anion is the ligand from cases where organic compounds having a chloro in their name are ligands.