Synthesis of <i>N</i>‑Aryloxy-β-diketiminate Ligands and Coordination to Zirconium, Ytterbium, Thorium, and Uranium

Two examples of <i>N</i>-aryloxy-β-diketiminate dianions (<b>11a</b>,<b>b</b>) have been synthesized on a multigram scale, in four steps, from commercially available chemicals. The synthetic scheme relies on the sequential addition of 2,6-diisopropylaniline and 2-amino-4-<i>tert</i>-butylphenol (<b>1a</b>) (or 2-amino-4,6-di-<i>tert</i>-butylphenol (<b>1b</b>)) to acetylacetone, using Et₃OBF₄ as an activation reagent. Both the nature of the activation reagent and the order of addition of the primary amines have a major impact on the outcome of the reaction, and acid catalysts (such as sulfuric acid or <i>p</i>-toluenesulfonic acid) lead to decomposition of the β-diketiminate backbone via formation of a benzoxazole derivative (<b>3a</b>,<b>b</b>). Using dianions <b>11a</b>,<b>b</b>, mono- and bis­(<i>N</i>-aryloxy-β-diketiminate) complexes of zirconium­(IV), ytterbium­(III), thorium­(IV), and uranium­(IV) have been synthesized (<b>12</b>–<b>18</b>), by salt metathesis reactions, and characterized by a combination of ¹H/¹³C NMR spectroscopy, elemental analysis, and X-ray crystallography. The two ligands differ in their steric bulk and exhibit different coordination behaviors, which were rationalized on the basis of geometric considerations

Bimetallic Cleavage of Aromatic C–H Bonds by Rare-Earth-Metal Complexes

A new type of C–H bond activation mediated by rare-earth metals under reducing conditions is reported. The synergy between reductants and rare-earth-metal complexes allows the cleavage of unactivated aromatic C–H bonds. The reaction between rare-earth-metal iodides supported by a 1,1′-ferrocenediamide ligand and potassium graphite in benzene leads to the formation of a 1:1 metal molar ratio of the corresponding metal hydride and metal phenyl complex. A proposed mechanism involving an inverse sandwich arene bimetallic intermediate is supported by experimental and computational studies