Coordination Number 2

The linear [Ag(NH3)2]+ ion

Although [Ag(en)]ClO4 involves a normally bidentate ligand, in this case the structure is polymeric and the silver ion still retains a CN=2 with the N atoms (from different ligands) at ~180 degrees to each other.

Coordination Number 3

Trigonal planar - D3h


[CuBr(PNP)] where PNP= (2,6-bis[(di-tert-butylphosphino)methyl]pyridine)

To help view more easily, the H atoms are turned off.

Trigonal pyramid


[Cu(PNP)]SbF6 where PNP= (2,6-bis[(di-tert-butylphosphino)methyl]pyridine)

To help view more easily, the H atoms are turned off.

Coordination Number 4



Square Planar

cisplatin - cis-PtCl2(NH3)2

The cis- isomer is a powerful anti-cancer drug whereas the trans- is inactive.

Coordination Number 5

Square pyramid

Trigonal Bipyramid


Coordination Number 6

Hexagonal planar

Trigonal prism


The ReS6 geometry is perfectly trigonal prismatic.



The first 'truly' inorganic complex to be resolved into its optical isomers.


mirror images

The classic example of optical isomerism in octahedral coordination complexes (H atoms not shown).
D isomer
L isomer


Coordination Number 7

Capped octahedron (C3v)


Capped trigonal prism (C2v)


Pentagonal Bipyramid (D5h)


The UO7 geometry fits a pentagonal bipyramid.

Coordination Number 8

Dodecahedron (D2d)


[Zr(C2O4)4]4- is reported to have this shape as well.

Cube (Oh)

Square antiprism (D4d)


Hexagonal bipyramid (D6h)


Coordination Number 9

Three-face centred trigonal prism (D3h)

Hydrated salts of the lanthanide elements eg Eu(H2O)9]3+

Coordination Number 10

Bicapped square antiprism (D4d)

Tetrakis(nitrato-O,O')-bis(triphenylphosphine oxide) cerium(IV)

Another example is [Ce(NO3)5]2-

Coordination Number 11

All-faced capped trigonal prism (D3h)

This is not a common stereochemistry.
In aqua-(12-crown-4)-tris(nitrato-O,O')-cerium(III) (12-crown-4) solvate and (15-crown-5)-tris(nitrato-O,O')-cerium(III) the Cerium ion is 11 coordinate.

Coordination Number 12

cuboctahedron (Oh)

Ceric ammonium nitrate -(NH4)2Ce(NO3)6

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Copyright © 1996-2014 by Robert John Lancashire, all rights reserved.

Created and maintained by Prof. Robert J. Lancashire,
The Department of Chemistry, University of the West Indies,
Mona Campus, Kingston 7, Jamaica.
Created March 1996. Links checked and/or last modified 15th January 2014.