Page 49 - Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005)

G R A M M A R I R-2.15

(j) To indicate stereochemistry at particular atoms in structures where arabic numerals have
been used for numbering those a toms.

Example:
12.
1 2 3 4 5
ClSiH SiHClSiHClSiH SiH 3
2
2
(2R,3S)-1,2,3-trichloropentasilane
IR-2.14.3 Letter locants
Italicized upper case letters are used as locants in certain s ubstitutive names. (See, for
example, Section IR-6.2.4.1.)
Lower c ase letters are used in polyoxometallate n omenclature to designate t he vertices of the
coordination polyhedra around the central atoms. They are attached to the number of the central
atom to which a p articular vertex refers. A detailed treatment is given in Chapter II-1 of Ref. 2.

IR-2.15 O R D E R I N G P R I N C I P L E S

IR-2.15.1 Introduction
Chemical n omenclature deals with names of elements and their combinations. Whereas
writing the symbol or the name o f a n e lement is straightforward, a c hoice of which element to
write first in the formula and in the name h as to be made a s s oon as an element is associated
with one or more o ther elements to form, for example, a b inary compound. The o rder of
citation o f e lements in formulae and names is based upon the methods outlined below.
Furthermore, groups of atoms, such as ions, ligands in coordination compounds and substituent
groups in derivatives of parent hydrides, a re ordered according to specified rules.

IR-2.15.2 Alphabetical order
Alphabetical order is used in formulae as follows.

(a) Within t he group of cations and within the group of anions, respectively, in formulae of
salts and double salts. Deviations from this rule m ay be acceptable if it is desired to convey
specific structural i nformation, as in Example 5 b elow.

Examples:

1. BiClO (anions Cl and O )
2

2. NaOCl (the anion is OCl , cf. S ection IR-4.4.3.1)
3. KNa 4 Cl(SO 4 ) 2
4. CaTiO 3 (perovskite type)
5. SrFeO 3 (perovskite type)

(b) In formulae of coordination compounds and species formally treated as coordination
compounds, ligands are cited in alphabetical order of their formulae or abbreviations

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