Class 12 Chemistry Coordination Compounds Nomenclature of coordination compounds

Nomenclature of coordination compounds

Like for ionic compounds the naming is done by writing first cation name and then naming anion.

For example: NaCl is ionic and written as sodium chloride that is in name first part is cationic and other is anionic.

In the same way coordination compounds consist of two parts:Cation and anion. While naming,the name of cationic part is written first followed by anionic part. There are certain set of rules that are followed while writing name of cation.

 

Naming for cationic species: in which coordination sphere is positively charged

  • Name of cation is written first

Let’s say the coordination sphere is cationic that is with positive charge for example [Co (NH3)6] Cl3 for the naming of coordination entity is done first and later the counter ion .so in given complex the name of [Co (NH3)6] is written first than the counter ion Cl

  • In case of coordination entity: the name of ligands is written first and then the central metal atom. Forexample, in this [Co (NH3)6]the name of NH3 is written first than for Co.
  • If the ligands are homoleptic than you can write in any manner but if they are heterodetic than the alphabetical order is followed

For example: in complex [Co (NH3)5CL] the name of ligands is written in alphabetical order that is for ammine firstand then chloro.

Rules for writing the name of the ligand:

  • If the ligand names end with ‘ate’ or ‘its‘than e is replaced by o

Like for oxalate it is written as oxalate, sulphite as sulphito

  • If ligand name end with’ ide ‘than ide is replaced by ‘o ‘

Example for chloride it becomes chlorido

  • Neutral ligands are name as such like for water it is aqua, for ammonia it is ammine
  • If more than one ligand is present than alphabetical order is followed and di,tri, tetra is prefixed before the name of ligand.

For example: in complex [Co (NH3)6] ligand name will be hexamine that is hexa for 6

  • For polydentate ligands they include numerical prefix –like di is replaced by bi, tri is replaced by tris, tetra is replaced bytetra is so on

For example: [CoCl2(en)2] Cl in this the ligands are dichlorobisethylenediamine

In case of Central metal atom:

Oxidation state of central metal atom is written in numeral after the name of central metal atom

For example: in complex [Co (NH3)6] Cl3 it is hexamine cobalt (III) that is cobalt (III) is central metal atom with its Oxidation state in numeral

  • if complex is cationic than normally the name is used: example is same as given above
  • if complex is anionic than metal atom name ends with ate

for example: in complex K3[fe(CN)6] in this the name is written as potassium hexacyanoferrate(III) that is in this example coordination entity is anionic complex and the name of central metal atom is written with ate followed by Oxidation state in numeral

  • if complex is neutral than the normal central metal atom name is used

some commonly used ligands:

  • bromo Br-
  • floro F-
  • oxo
  • hydroxo OH-
  • cyano CN-
  • carbonato CO32-
  • acetate CH3COO-
  • ammine NH3
  • aqua H2O
  • nitrosyl NO
  • carbonyl CO
  • dioxygen O2
  • dinitrogen N2
  • pyridine C5H5N
  • ethylene diamine H2NCH2CH2NH2

some examples of iupac naming:

  1. [Cr (NH3)(H2O)3]Cl3

Triaminetriaquachromium(III)chloride

  1. [Co(en)3]2(SO4)3

Trisethylenediaminecobalt(III)sulphate

  1. [Ag(NH3)2][Ag(CN)2]

Diamine argentum(i)dicyanoargentate(i)

  1. [Pt (NH3)2Cl (NO2)]

Diaminechloronitroplatinum(III)

  1. K3[Cr(C2O4)3]

Potassiumtrioxalatochromate(III)

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