# Transition metal and complexation

When can we say that such metal forms a complex?

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

• Yes, they are. Most so called salts are actually polymeric complexes. – Mithoron Oct 4 '15 at 0:26

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.
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.