While studying about the Nomenclature of Coordination Compounds I came to know that

While writing formulae of Mononuclear Coordination entities polyatomic ligands are enclosed in parenthesis and also their abbreviations.

But while naming the entities should I follow the same rule?

Like for $\ce{[Ni(H2O)2(en)2]SO4}$ should it be named as

Di(aqua)bis(ethylene-1,2-diamine)nickel(II) suphate


Diaquabis(ethylene-1,2-diamine)nickel(II) sulphate

I Mean is there any rule that says you only need to close certain species of ligands like specifically bidentate (such as en) and polydented ligands (such as EDTA) and can keep the others as they are?


  • 1
    $\begingroup$ If you ask which ligand names have to be parenthesized then simply ask that. Right now the title is meaningless. $\endgroup$
    – Mithoron
    Commented Dec 27, 2020 at 19:31
  • $\begingroup$ Thanks for the help @Mithoron I'm really confused about only the polyatomic ligands. $\endgroup$
    – S RM
    Commented Dec 27, 2020 at 21:31

1 Answer 1


Greek prefixes are used to designate the number of each type of ligand in the complex ion, e.g. di-, tri- and tetra-. If the ligand already contains a Greek prefix (e.g. ethylenediamine) or if it is polydentate ligands (ie. can attach at more than one binding site) the prefixes bis-, tris-, tetrakis-, pentakis-, are used instead.

Bottom line - parenthesize only those ligands which already has a greek prefix in its name so that you can highlight the use of the alternative prefixes such as bis-,tris- etc.

Ps -Diaquabis(ethylene-1,2-diamine)nickel(II) sulphate is the correct naming but you can make it more appropriate by using ethane instead of ethylene


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