According to IUPAC Gold Book, the definition of "complex" is preferably called "coordination entity" which is stated that:

An assembly consisting of a central atom (usually metallic) to which is attached a surrounding array of other groups of atoms (ligands).

So, it is not forbidden for a non-metal to be called "coordination entity" which in fact, lots of them exhibit this term like [PCl6]-, [SiF6]2-,... The problem that I have is that of ammonium cation, it is an adduct.

So, is ammonium a coordination compound?

  • $\begingroup$ Nobody calls it as such - that's the important thing. $\endgroup$
    – Mithoron
    Mar 26 at 17:00
  • $\begingroup$ You mean nobody calls ammonium a coordination compound? $\endgroup$
    – Seiji
    Mar 26 at 17:06
  • $\begingroup$ There is a key point to coordination compound. Here the metal atom accepts electrons from ligands (neutral species like H2O, NH3), forming coordination bond, hence the name. The whole species can be charged and that can be considered a complex ion, for e.g. $\ce{[Co(NH3)6]^3+}$. Ammonium ion on the other hand is two atoms covalently bonded and the species is charged, hence it is a polyatomic ion. $\endgroup$ Mar 26 at 17:17
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    $\begingroup$ I want to be a little specific: a) There is a coordination bond in NH4+ which is H3N-->H. Is it compulsory for a coordination compound to be fully coordination bond and no covalent bond involved? b) According to coordination complex of wikipedia: en.wikipedia.org/wiki/Coordination_complex. I could say [PCl6]- a coordination compound. Is it wrong? $\endgroup$
    – Seiji
    Mar 26 at 17:37
  • $\begingroup$ There's no "coordination bond", it's dative, or coordinate, bond. This is an arbitrary distinction, as all bonds in ammonium are exactly the same and dative bonds are no different from "non-dative" ones. $\endgroup$
    – Mithoron
    Mar 26 at 20:45


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