Page 121 - Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005)

A D D I T I V E N O M E N C L A T U R E IR-7.1

Note that in some c ases, a c ompound named additively may alternatively and equally
systematically be named substitutively on the basis of a s uitably chosen parent structure
(Chapter IR-6). I t i s i mportant to note, h owever, that additive names for parent hydrides
cannot be used as parent n ames in substitutive nomenclature.

IR-7.1.2 Choosing a c entral atom or atoms, or a c hain or ring structure
Making a c hoice of central atom or atoms is a k ey step in the process of naming a c ompound
using additive nomenclature. If there are (one or more) metal atoms in the compound, these
should be chosen a s t he central atom(s). Such atom(s) should also be relatively central in the
structure and, where possible, should be chosen to make u se of molecular symmetry (thereby
shortening the name). Usually hydrogen atoms are disregarded when choosing central atoms.
For some c ompounds, a c hoice of central atom or atoms will remain. The atom(s) that
occur(s) latest when f ollowing the arrow in Table VI should be chosen a s t he central
atom(s).
If there is more t han one central atom in a s tructure according to the above criteria then
the compound can be named as a d inuclear or polynuclear compound.
As an alternative to the procedure above, a g roup of atoms forming a c hain or ring
sub-structure within a c ompound may be chosen in order to give the compound an additive
name using the chains and rings nomenclature outlined in Section IR-7.4.

IR-7.1.3 Representing ligands in additive names
Additive names are constructed by placing (sometimes modified) ligand names as prefixes
to the name o f t he central atom. For anionic ligands, t he anion endings ‘ide’, ‘ate’ and ‘ite’
(see Section IR-5.3.3) are changed to ‘ido’, ‘ato’ and ‘ito’, r espectively, when generating
these prefixes. Names of neutral and cationic ligands are used unchanged, except i n a few
special cases, most n otably water (prefix ‘ aqua’), a mmonia (prefix ‘ammine’), carbon
monoxide bound through carbon (prefix ‘carbonyl’), a nd nitrogen m onoxide bound through
nitrogen ( prefix ‘nitrosyl’) (cf. S ection IR-9.2.4.1).
In principle, i t i s a matter of convention whether a l igand is considered to be anionic,
neutral or cationic. The d efault is to consider ligands as anionic, s o t hat OH is ‘hydroxido’,
Cl ‘chlorido’, S O ‘sulfato’, etc. Some ligands are conventionally regarded as neutral,
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e.g. amines and phosphanes and ligands derived from hydrocarbons by removal of a
hydrogen atom, such as methyl, benzyl, etc.
Appropriate prefixes t o r epresent many s imple ligands within names are given in
Table IX. For further details, see Section IR-9.2.2.3.

IR-7.1.4 Ions and radicals

Anionic s pecies take the ending ‘ate’ in additive nomenclature, whereas no distinguishing
termination is used for cationic or neutral species. A dditive names of ions end with the
charge number (see Section IR-5.4.2.2). In additive names of radicals, the radical character
of the compound may be indicated by a r adical dot, •, a dded in parentheses and centred, a fter
the name of the compound. Polyradicals are indicated by the appropriate n umeral placed
before the dot. For example, a d iradical is indicated by ‘(2•)’.

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