Beta-diketonate complexes of the early lanthanides (La-Sm) can have high and variable coordination numbers (8 to 10) that can make characterization and evaluating reactivity challenging. Since bonding in lanthanide complexes is dominated by electrostatic contributions, they are also quite labile and prone to decomposition over time-particularly in solution. Because of their high hydration enthalpies, in air, coordinatively unsaturated lanthanide complexes will tend to pick up water. However, these hydrate complexes are not suitable for reaction with moisture sensitive ligands, may exhibit lower than expected solubility in organic solvents and have reduced reactivity. Using mechanochemistry and solution chemistry to synthesize complexes of the form Ln(hfac)3(H2O)x, (x=2,3, hfac = 1,1,1,5,5,5-hexafluoroacetylacetonato), we discovered differences in reactivity based on the method used to prepare Ln(hfac)3(H2O)x. Lanthanide complexes containing bidentate oxygen donor ligands in lieu of water were also prepared. The complexes containing bidentate oxygen ligands tend to be mononuclear and easier to purify and characterize. We evaluated these complexes reactivity with polypyridyl ligands using mechanochemical methods and compared them to the hydrates.The reactions were followed using infrared spectroscopy (IR), powder X-ray diffraction (PXRD). Purity was determined using differential scanning calorimetry (DSC) and stability in solution was determined by 1H, 19F and 13C NMR spectroscopy.

Reactivity of lanthanide complexes: Evaluating starting materials

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