When can we say that such metal forms a complex?

Are $\ce{Pd(OAc)2}$ and $\ce{Pd(PPh3)2Cl2}$ complexes?

  • 1
    $\begingroup$ Yes, they are. Most so called salts are actually polymeric complexes. $\endgroup$
    – Mithoron
    Oct 4, 2015 at 0:26

1 Answer 1


Both of these compounds are coordination complexes. The label complex is preferred by many chemists because despite the appearance of some of these compounds as simple ionic compounds, they often display much more complex bonding motifs.

For example in $\ce{Pd(PPh3)2Cl2}$, there are two neutral ligands, $\ce{PPh3}$ that interact with the metal center through dative bonds. There is also evidence that the $\ce{Pd-Cl}$ bond is more covalent than ionic, since palladium forms a complex ion $\ce{PdCl4^-}$ with chlorine.

Palladium acetate man seem like a more clear cut case until you look at the crystal structure. Each acetate anion bridges two palladium, centers in a polymeric chain:

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It is worth noting that IUPAC does not recommend using the term complex to describe these compounds given that complex can refer to a number of other, more loosely bound, species. IUPAC prefers coordination entity, though I have never heard a practicing chemist or seen a textbook use that phrase.


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