Enclosing marks nesting order

The name of the polymer is simply the name of the preferred CRU enclosed in curves, square brackets or braces and prefixed by poly. The nesting order of enclosing marks is curves, square brackets, braces, then curves, square brackets, braces, etc., i-6- [( [( )] )] This is well illustrated in Examples 21 and 31 in Section 9. 

Of the two kinds of numerical prefix (see Table 4.2), the simple di-, tri-, tetra-, etc. are generally recommended. The prefixes bis-, tris-, tetrakis-, etc. are to be used only with more complex expressions and to avoid ambiguity. They normally require parentheses around the name they qualify. The nesting order of enclosing marks is as cited on p. 13. There is normally no elision in instances such as tetraammine and the two adjacent letters a are pronounced separately. 

In formulae, these enclosing marks are used in the following nesting order [],[()],[ () ], [( () )], [ ( () ) ], etc. Square brackets are normally used only to enclose entire formulae parentheses and braces are then used alternately (see also Sections IR-4.2.3 and IR-9.2.3.2). There are, however, some specific uses of square brackets in formulae, cf. Section IR-2.2.2.1. 

The formula for the entire coordination entity, whether charged or not, is enclosed in square brackets. When ligands are polyatomic, their formulae are enclosed in parentheses. Ligand abbreviations are also usually enclosed in parentheses. The nesting order of enclosing marks is as given in Sections IR-2.2 and IR-4.2.3. Square brackets are used only to enclose coordination entities, and parentheses and braces are nested alternately. 

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