Priming convention

Not only are some inorganic compounds named using the kappa convention, others augment this kappa convention with a "priming" convention [49], All of these are, similarly, made obsolete by the proposed system. For example, the ion illustrated in Figure 25, which IUPAC names as aqua[(l,2-ethanediyldinitrilo-K2N,N ) (tetraacetato-K30,0",0 " )]cobaltate (1-) would be named as ... 

Fig. 26 An Ion that Needs Both the Kappa and the Priming Conventions in IUPAC Nomenclature...

As well as the spherical name being much shorter, by virtue of the priming convention introduced above, no locant numbers above 40 are required. 

Priming convention. The configuration index is especially useful for bis(tridentate) complexes and for more complicated cases. Bis(tridentate) complexes exist in three di-astereoisomeric forms which serve to illustrate the utility of a priming convention. These isomers are represented below, along with their site symmetry symbols and configuration indexes. For Examples I, 2, and 3, the two ligands are identical and the ligating-atom priority numbers are indicated. 

The presence of polydentate ligands may require the use of primes on some of the numbers in the configuration index. The primes are used to indicate either that donor atoms are not part of the same polydentate ligand as those that have unprimed priority numbers, or that the donor atoms belong to different parts of a polydentate ligand that are related by symmetry. A primed priority number means that that donor atom has lower priority than the same kind of donor atom without a prime on the priority number. More detail on the priming convention can be found in Section IR-9.3.5.3. 

The C/A assignment for polydentate ligands is illustrated by Example 6 which uses the priming convention developed in Section IR-9.3.5. Note that priority number 2 has higher priority than 2/. 

The following sections outline the method used to arrive at the priority numbers for a given set of donor atoms, and the ways that the basic mles have to be modified in order to describe adequately systems that include polydentate ligands. These modifications, which are collectively referred to as the priming convention, make use of primes on the priority numbers to indicate which donor atoms are grouped together within a particular polydentate ligand. 

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