Ln Alkoxide complexes

These examples show how the size of the ligand influences the structure of the complex.

Click on the links to display the structures

[La3(m3-OBut)2(m2-OBut)3(OBut)4(Bu2OH)2]

The -OBut ligand is not sufficiently sterically demanding to stabilise a monomeric [La(OBut)3] complex. Higher coordination numbers are achieved by formation of a tri-nuclear complex with terminal, doubly- and triply-bridging alkoxide ligands.

Note that there are no La-La bonds, although Jmol may show some.


[La3(mu-3-OBut)2(mu-2(OBut)3(OBut)4(ButOH)2]

[Ce(O-2,6-But2-C4H3)3]

The substituents in the 2,6 positions of this aryloxide make it very sterically demanding, and 3-coordinate monomeric complexes with all Ln(III) are known
[Ce(O-2,6-But2-C4H3)3]

Aryloxides of Eu(II) and Yb(II)

OAr_structures

Eu(II) and Yb(II) are larger than their corresponding Ln(III) ions. This makes it more of a challenge to achieve coordinative saturation, especially given the reduced charge and therefore the reduced number of uni-negative ligands that are required for a neutral complex.

[Eu3(OAr)6(thf)6] achieves a c.n of 6 through bridging OAr ligands and coordination of thf.

Yb(II) is smaller than Eu(II) and a c.n. of 3 is achieved in [Yb2(OAr')4] (note that Ar' has But substituents)

 


[Eu3(OAr)6(thf)6]
[Yb2(OAr')4]

 [Ce2(OiPr)4(iPrOH)2]

Ce is the only lanthanide that has a +4 oxidation stte accessible in solution. The radius of Ce(IV) is smaller than that of Ce(III). Ce(IV) has a c.n. of 6 in [Ce2(OiPr)4(iPrOH)2]

 


[Ce2(OiPr)4(iPrOH)2]

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