Page 165 - 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

Donor a toms of a p articular e lement may be distinguished by adding a r ight superscript
numerical locant to the italicized element symbol or, in simple cases ( such a s E xample 3
below), a prime or primes.
Superscript numerals, on the other hand, are based on an appropriate numbering of some
or all of the atoms of the ligand, such as numbering of the skeletal atoms in parent hydrides,
and allow the position of the bond(s) t o t he central atom to be specified even in quite

complex c ases. In the simple c ase of acetylacetonate, MeCOCHCOMe , m entioned above,
3
the ligand name 2,4-dioxopentan-3-ido-kC would imply ligation by the central carbon atom
in the pentane skeleton (see also Example 4 b elow).
In some cases, standard n omenclature procedures d o n ot provide locants for the donor
atoms in question. In such cases s imple ad hoc procedures may be applicable. F or example, for

the ligand (CF 3 COCHCOMe) , t he name 1,1,1-trifluoro-2,4-dioxopentan-3-ido-kO could be
used to refer to coordination, through oxygen, of the CF 3 CO portion of the molecule, while
0
coordination by MeCO would be identified by 1,1,1-trifluoro-2,4-dioxopentan-3-ido-kO . T he
prime indicates that the MeCO oxygen atom is associated with a h igher l ocant in the molecule
than the CF 3 CO oxygen atom. The oxygen atom of the CF 3 CO portion of the ligand is attached
to C2, while that of MeCO is attached to C4. Alternatively, the name c ould be modified to
1,1,1-trifluoro-2-(oxo-kO)-4-oxopentan-3-ido and 1,1,1-trifluoro-2-oxo-4-(oxo-kO)pentan-
3-ido, respectively, for the two binding modes a bove.
In cases w here two or more identical ligands (or parts of a p olydentate ligand) are
involved, a superscript is used on k to indicate the number of such ligations. A s m entioned
above, any multiplicative prefixes for complex e ntities a re presumed t o o perate on the k
symbol as well. T hus, one uses the partial name ‘. . .bis(2-amino-kN-ethyl). . . ’ a nd not
2
‘. . . bis(2-amino-k N-ethyl). . . ’ i n E xample 2 b elow. Examples 2 a nd 3 u se tridentate
chelation by the linear tetraamine ligand N,N -bis(2-aminoethyl)ethane-1,2-diamine to
0
illustrate these r ules.

Examples:
2. H C CH 2 +
2
H N NHCH CH 2
2
2
Pt NH
Cl NH CH CH 2
2
2
[N,N -bis(2-amino-kN-ethyl)ethane-1,2-diamine-kN]chloridoplatinum(II)
0

3. H C 2 C H 2 +
H N NH CH
2
Pt 2
CH
Cl NH 2
CH CH NH 2
2
2
[N-(2-amino-kN-ethyl)-N -(2-aminoethyl)ethane-1,2-
0
2
0
diamine-k N,N ] c hloridoplatinum(II)

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