Page 159 - Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005)

C O O R D I N A T I O N C O M P O U N D S IR-9.2

The flowchart shown i n F igure IR-9.1 illustrates a g eneral procedure for producing a
name for a c oordination compound. Sections containing the detailed rules, guidelines and
examples relevant t o e ach stage of the procedure are indicated.
The name o f a c ompound can, however, be rather long and its use may be inconvenient.
In such circumstances a f ormula provides a s horthand m ethod of representing the compound.
Rules are provided in order to make t he use of formulae more s traightforward. It should be
noted that, because of their abbreviated form, it is often not possible to provide as much
information about the structure of a c ompound in its formula a s c an be provided by its name.

IR-9.2.2 Names of coordination compounds

The systematic names of coordination entities are derived by following the principles of
additive n omenclature, as outlined in Chapter I R-7. Thus, the groups that surround the central
atom or structure must b e i dentified in the name. They are listed as prefixes t o t he name of the
central atom (see Section IR-9.2.2.1) along with any appropriate multipliers (see Section IR-
9.2.2.2). T hese prefixes a re usually derived in a s imple way from the ligand names (see Section
IR-9.2.2.3). Names of anionic coordination entities are furthermore given the ending ‘ate’.

IR-9.2.2.1 Sequences of ligands and central atoms within names
The following general rules are used when naming coordination compounds:

(i) ligand names are listed before the name(s) o f t he central atom(s),
(ii) no spaces a re left between parts of the name that refer to the same coordination entity,
(iii) ligand names are listed in alphabetical order (multiplicative prefixes i ndicating the
number of ligands are not considered in determining that order),
(iv) the use of abbreviations in names is discouraged.

Examples:

1. [CoCl(NH 3 ) 5 ]Cl 2
pentaamminechloridocobalt(2þ) c hloride
2. [AuXe 4 ] 2þ
tetraxenonidogold(2þ)

Additional rules which apply to polynuclear compounds are dealt with in Section IR-9.2.5.

IR-9.2.2.2 Number o f l igands in a c oordination entity
Two kinds of multiplicative p refix are available for indicating the number of each type of
ligand within the name o f t he coordination entity ( see Table IV).

(i) Prefixes d i, tri, etc. a re generally used with the names of simple l igands. E nclosing
marks are not required.
(ii) Prefixes b is, tris, tetrakis, etc. a re used with complex ligand names and in order to
avoid ambiguity. Enclosing marks (the n esting order of which is described in Section
IR-2.2) m ust be placed around the multiplicand.

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