Cluster lanthanide aryloxides clusters

The use of unsubstituted or 4-methyl phenols resulted in the formation of cluster compounds [58]. However, 2,6-di(fcrt-butyl) substituted aryloxide ligands allowed the isolation of mononuclear 3-coordinate homoleptie complexes of the lanthanide elements, the coordination mode of which was first demonstrated with the N(SiMe3)2 ligand [59], The 2,6-substitution pattern is very effective because the alkyl groups are directed towards the metal center and impose a steric coordination number onto the metal which is comparable to the Cp ligand (Cp 2.49 OC6H3rBu2-2,6 2.41) [60],... 

Clusters of lanthanide alkoxides, aryloxides, and macrocyclic polyaryloxides... 

It is clear from the chemistry of lanthanide clusters based on aryloxide ligands that lanthanide coordination chemistry can be further developed by having recourse to other fimctionalized aryloxide ligands. In this context, the use of constrained, macrocyclic polyaryloxide ligands such as calixarenes or their sulfur-containing analogues appears intriguing. 

It is also common that mixed metal derivatives of the lanthanides and group 1 metals are the products of synthesis. This can occur for small aryloxides leading to clusters, e.g. [La2Na3(/r4-OAr)3(/z2-OAr)6(dioxane)5] (OAr = OQH4Me-4), as well as in the generation of more discrete species with bulkier aryloxides, e.g. [(thf)Li(/i2-OAr)2La(OAr)2(THF)] (OAr = OC6H3Pr -2,6). In some situations the alkali metal interacts with the aryloxide jr-nucleus, e.g. [Cs( 7r-Ar-0)2La(OAr)2] (OAr = OC6H3P1I-... 

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