Page 68 - Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005)

IR-4.4 F O R M U L A E

Examples:

1. NH 3
2. H 2 S

3. OF 2
4. O 2 Cl

5. OCl
þ
6. PH 4
4
7. P 2 O 7
8. [SiAs 4 ] 8
9. RbBr
10. [Re 2 Cl 9 ]

11. HO or OH
12. Rb 15 Hg 16
13. Cu 5 Zn 8 and Cu 5 Cd 8

Note that the formula f or the hydroxide ion should b e H O to be consistent with the above

convention.
Ordering by electronegativity could, in principle, be applied to ternary, quaternary, etc.
species. F or most species consisting of more t han two elements, however, o ther criteria for
ordering t he element symbols in the formula are more often used (see Sections IR-4.4.3.2 to
IR-4.4.3.4).

IR-4.4.3.2 Formal treatment as coordination compounds
The nomenclature of coordination compounds is described in detail in Chapter I R-9. A b rief
summary of the construction of formulae of coordination compounds is given h ere. M any
polyatomic c ompounds may conveniently be treated as coordination compounds for the
purpose o f c onstructing a f ormula.
In the formula of a c oordination e ntity, t he symbol of the central atom(s) is/are placed
first, followed by the symbols or formulae of the ligands, unless additional structural
information can be presented by changing the order (see, for example, Section IR-4.4.3.3).
The order of citation of central atoms is based on electronegativity as described in
Section IR-4.4.2.1. Ligands are cited alphabetically (Section IR-4.4.2.2) a ccording to the
first symbol of the ligand formula or ligand abbreviation (see Section IR-4.4.4) as written.
Where possible, the ligand formula s hould b e w ritten in such a w ay that a/the donor atom
symbol is closest to the symbol of the central atom to which it is attached.
Square brackets m ay be used to enclose the whole c oordination entity w hether c harged
or not. Established practice is always to use square b rackets for coordination entities w ith
a t ransition metal as the central atom (cf. S ections IR-2.2.2 and IR-9.2.3.2).

Examples:

1. PBrCl 2
2. SbCl 2 F o r [ SbCl 2 F]

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