What do we mean by the term Complexes?

What do we mean by the term Complexes?

Grade:Upto college level

1 Answers

askIITIians Expert
21 Points
15 years ago



The transition elements have an unparalleled tendency to form coordination compounds and with Lewis bases, that is with a group which are able to donate an electron pair.




Thus, coordination compound or a complex compound is a result of the combination of different compounds or specie and it retains its own identity in the solid, as well as in the dissolved state. It is a compound containing a complex ion, in which the constitutent atoms or group (i.e. the central metal ion and the ligand in the complex ion) do not retain their own properties due to stable bonds between the central ion and the ligands. The compound is called coordination compound on account of coordinate bond involved in the complex ion. For example KCN reacts with Fe(CN)2 gives the complex compound, K4[Fe(CN)6] (potassium ferrocyanide) This complex does not answer the usual tests for ferrous ion and cyanide ion. In this important respect, the complex salt differs from a double salt, thus Mohr’s salt i.e., FeSO4(NH4)2SO4.6H2O, obtained by mixing saturated solutions of FeSO4 and (NH4)2SO4, answer for Fe2+, NH4+ and So42– ions.




Coordination compound, thus, consists of either


(i)         a simple cation and a complex anion such as K4[FeCN)6]


(ii)        a complex cation and a simple anion such as [Cu(NH3)4SO4.


(iii)       a complex cation and a complex anion such as [Co(NH3)6][Cr(C2O4)3]


(iv)       a neutral molecule such as Ni(CO)4, Ni(DMG)2 etc.

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