Square brackets with coordination entities

Square brackets may be used to enclose the whole coordination entity whether charged or not. Established practice is always to use square brackets for coordination entities with a transition metal as the central atom cf. Sections IR-2.2.2 and IR-9.2.3.2). 

Ionic charges und oxidation numbers. If the formula of a chaigcd coordination entity is to be written wilhoul that of the countenon, the churge is indicated outside the square bracket as n right superscript, with the number before the sign. The oxidation number of a central atom may be represented by a roman numeral used as a right superscript or the element symbol. 

Note from the examples above that in order to stress the distinctions discussed, the square brackets are sometimes used in the Table to enclose formulae for molecular entities that are otherwise often written with no enclosing marks. When a formula with square brackets is shown, there will also be a coordination-type additive name. 

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