Molecular Examples
- Page ID
- 520
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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
[Cu(CN)3]2-
[Cu(PPh3)2Br]
To help view more easily, the H atoms are turned off.
Trigonal pyramid
T-shaped
[Rh(PPh3)3]+
To help view more easily, the H atoms are turned off.
Coordination Number 4
Tetrahedral
Copyr2Cl2
Square Planar
cisplatin - cis-Pt(NH3)2Cl2
The cis- isomer is a powerful anti-cancer drug whereas the trans- is inactive.
Coordination Number 5
Square pyramid
Trigonal Bipyramid
[Ni(CN)5]3-
Coordination Number 6
Hexagonal planar
Trigonal prism
tris(cis-1,2-diphenylethene-1,2-dithiolato)rhenium
The ReS6 geometry is perfectly trigonal prismatic.
Octahedral
Hexol
The first 'truly' inorganic complex to be resolved into its optical isomers.
[Co(en)3]Cl3

The classic example of optical isomerism in octahedral coordination complexes (H atoms not shown).
[Co(NH3)5CO3]+
Coordination Number 7
Capped octahedron (C3v)
K3[NbOF6]
Capped trigonal prism (C2v)
[V(III)(Hedta)(H2O)]H2O
Pentagonal Bipyramid (D5h)
bis-(tert-butylacac)2(DMSO)di-oxoUranium
The UO7 geometry fits a pentagonal bipyramid.
Coordination Number 8
Dodecahedron (D2d)
Zr(acac)2(NO3)2
[Zr(C2O4)4]4- is reported to have this shape as well.
Cube (Oh)
Square antiprism (D4d)
U(acac)4
Hexagonal bipyramid (D6h)
UO2(OAc)3
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
Contributors and Attributions
- Prof. Robert J. Lancashire (The Department of Chemistry, University of the West Indies)