Page 164 - Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005)

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

The following sections detail the means by which donor atoms are specified. The k appa
(k) c onvention, introduced in Section IR-9.2.4.2, is general and can be used for systems o f
great complexity. In some c ases it may be simplified to the use of just the donor atom
symbol (see Section IR-9.2.4.4).
These systems may be used in names, but they are not always suitable for use in
formulae. The use of donor atom symbols is possible i n t he formulae of simple systems (see
Section IR-9.2.3.4), but care must be taken to avoid a mbiguity. The k appa convention is
not generally compatible with the use of ligand abbreviations.
These methods are normally used only for specifying bonding between the central atom
and isolated donor atoms. The eta (Z) c onvention is used for any cases where the central
atom is bonded to contiguous donor atoms within one ligand (see IR-10.2.5.1). Most
examples of this latter kind are organometallic compounds (Chapter IR-10) but t he example
below shows i ts use for a c oordination compound.

Example:

1. +
CMe 2
Me C NH 2
2
H N O
2
Co
O
H N
2
NH
Me C 2
2
CMe 2
2
bis(2,3-dimethylbutane-2,3-diamine)(Z -peroxido)cobalt(1þ)
IR-9.2.4.2 The kappa convention
Single ligating atoms are indicated by the italicized e lement symbol preceded by a G reek
kappa, k. T hese symbols are placed after the portion of the ligand name that represents the
ring, chain or substituent g roup in which the ligating atom is found.

Example:
1. [NiBr 2 (Me 2 PCH 2 CH 2 PMe 2 )]
dibromido[ethane-1,2-diylbis(dimethylphosphane-kP)]nickel(II)

Multiplicative prefixes which apply to a l igand or portions o f a ligand also apply to the
donor atom symbols. In some c ases this may require the use o f a n a lternative ligand
name, e.g. where multiplicative prefixes can no longer be used because the ligation of
otherwise equivalent portions of the ligand is different. Several examples of this are given
below.
Simple examples are thiocyanato-kN for nitrogen-bonded NCS and thiocyanato-kS for
sulfur-bonded NCS. Nitrogen-bonded nitrite is named nitrito-kN and oxygen-bonded nitrite
is named nitrito-kO, a s i n p entaamminenitrito-kO-cobalt(III).
For ligands with several ligating atoms linearly arranged along a c hain, the order of k
symbols should be successive, starting at one end. The choice of end is based upon
alphabetical order if the ligating atoms are different, e.g. cysteinato-kN,kS; c ysteinato-kN,kO.

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