Structural Chemistry of Lanthanide Alkoxide Complexes

Although it is reasonable to assume that higher-nuclearity complexes generally correspond to the use of less sterically encumbered ligands, the specific structure of a particular complex is uniquely dependent on the nature of its ligand. Thus readers are cautioned that each 

Using carefully chosen literature examples, specific features of the lanthanide coordination chemistry using aliphatic alkoxido, aryloxido, and macrocyclic polyaryloxido ligands are discussed below. For each ligand type, those bearing simple, spectator-like non-coordinating substituents and those functionalized with donor groups capable of metal coordination will be treated separately. 

1 Complexes of Alkoxido Ligands with Non-coordinating Substituents 

Increasing the ligand steric bulk has significant effects on the complex structure, for example, a trinuclear complex formulated as [Y3(p3-OBu0(P3-Cl)(p-OBu03(OBu03Cl(THE)2] 

The coordination of solvent molecules may reflect a compromise between the propensity of the metal to satisfy its coordinative saturation requirement and the inadequate room for the accommodation of an additional alkoxido ligand that is sizably bulkier than a solvent molecule. That is, the relatively small solvent molecules serve to fulfill the metal s high-coordination need but without interrupting, as a bulkier alkoxido ligand would, the overall structure of the resulting complex. 

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