What are Coordination Compounds

Properties of Coordination Complexes

Some techniques of verifying the existence of complex ions contain studying its chemical behavior. This could be achieved by observing the compounds' solubility, color, magnetic properties, absorption spectrum, and so on. The properties of coordination compounds are separate from the properties of the individual atoms.


Based on the Lewis base theory, ligands tend to be Lewis bases because they can donate electrons to the main metal atom. The metals, in turn, are Lewis acids because they take electrons. Coordination complexes contain a metal center cation and a ligand. The entire charge can be negative, positive or neutral. Coordination compounds are complex or contain complex ions, for instance:

Complex Anion: [CoCl4(NH3)2]-

Complex Cation: [CO(NH3)6]3+

Coordination Compound: K4[Fe(CN)6]

Neutral Complex: [CoCl3(NH3)3]

A ligand can be a neutral or an anion molecule which donates an electron set to the complex. Ex: NH3, H2O, Cl-. The number of ligands which attach to a metal depends on whether the ligand is bidentate, polydentate or monodentate.

How to Name Coordination Compounds

Naming Coordination Complexes

Given Formula → Write Name

To start naming coordination complexes, here are a few things to remember. 

Ligands are named first in alphabetical order.

The name of the metal comes next.

The oxidation state of the metal follows, noted through a Roman numeral in parentheses (II, IV).            

Rules for Naming the Ligands

1. Ligands that work as anions that end in -ide are changed with an ending -o (e.g., Chloride → Chloro).

Anions finishing with -ate and -ite are changed with endings -ato and -ito respectively (e.g., Nitrite → Nitrito, Nitrate → Nitrato).

2. Many neutral molecules which are ligands have their normal name. The few exceptions are the very first four on the chart: aqua, ammine, nitrosyl and carbonyl.

Coordination Compounds Examples

A compound containing a number of coordinate bonds that is a link between a set of electrons where both electrons are contributed by one of the atoms.

Coordination Compounds Examples:

[Co(NH3)6]Cl3                   hexaamminecobalt (III) chloride      

K[AuCl4]                            Potassium tetrachloroaurate(III)              

Cu2[Fe(CN)6]                    copper(II) hexacyanoferrate(II)       

[Pt(NH3)6]Cl4                    hexaammineplatinum(IV) chloride

[Cu(NH3)4(H2O)2]Cl2       tetraamminediaquacopper(II) chloride

Cr(CO)6                              hexacarbonylchromium (0)        

K3[CoF6]                           potassium hexafluorocobaltate(III)        

[Pt(en)2]CO3                      bis(ethylenediamine)platinum(II) carbonate              

[Ni(H2O)6]Cl2                   hexaaquanickel(II) chloride                

[Zn(en)F2]                         (ethylenediamine)difluorozinc  

[Cr(NH3)5(NO2)]2+         pentaamminenitritochromium(III) ion   

Ba[FeBr4]2                        barium tetrabromoferrate(III)  

[Co(en)2Br2]2SO4           dibromobis(ethylenediamine)cobalt(III) sulfate               

[Ag(NH3)2]Cl                  diamminesilver chloride       

[Cu(CN)4]3-                    tetracyanocuprate(I) ion     

K[Pt(NH3)Cl5]                 potassium amminepentachloroplatinate (IV)

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