Lanthanide hydroxide cluster complexes via ligand-controlled hydrolysis of the lanthanide ions

We survey in this chapter the lanthanide hydroxide cluster complexes since the publication of the comprehensive review on the same subject (Handbook of physics and chemistry of rare earths 40:109-240, 2010). Specifically, polynuclear complexes with carboxylate, diketonate, phosphate, sulfonate, and polyoxometalate (POM) ligands featuring polyhedral cluster-type lanthanidehydroxo (Ln-OH) core motifs are summarized. The synthetic procedures leading to the production of the cluster species and the unique cluster core motifs are the focus of the discussion. Within each ligand family, we organize the cluster complexes according to their nuclearity with the intention to demonstrate the formal assembly of higher-nuclearity complexes using smaller and recognizable motifs as secondary building units. It is clear that a number of such motifs are prevalent and are shared by cluster complexes with ligands that are structurally and functionally distinct. With the work reviewed previously and the rapidly increasing number of polynuclear lanthanide hydroxide complexes, we hope to validate that once a synthetic serendipity, the chemistry of lanthanide hydroxide complexes is now a legitimate new paradigm of lanthanide coordination chemistry that is of fundamental interest and potential useful applications.