Synthesis of a New Class of Compounds Containing a Ln−O−Al Arrangement and Their Reactions and Catalytic Properties

Synthesis of a new class of compounds containing a Ln−O−Al moiety has been accomplished by the reaction of LAlOH(Me) (L = HC(CMeNAr)<sub>2</sub>, Ar = 2,6-<i>i</i>Pr<sub>2</sub>C<sub>6</sub>H<sub>3</sub>) with a series of Cp<sub>3</sub>Ln compounds. The terminal Al−OH group shows selective reactivity, and the complexes Cp<sub>2</sub>Ln(THF)−O−AlL(Me) (Ln = Yb, <b>1</b>; Er, <b>2</b>; Dy, <b>3</b>), Cp<sub>2</sub>Yb−O−AlL(Me) (<b>4</b>), and Cp<sub>3</sub>Ln(μ-OH)AlL(Me) (Ln = Er, <b>5</b>; Dy, <b>6</b>; Sm, <b>7</b>) were obtained. This allows further insight into the proton exchange process, and two different mechanisms, intermolecular and intramolecular elimination of CpH, are proposed under different conditions. Complexes <b>1</b>−<b>4</b>, <b>6</b>, and <b>7</b> have been characterized by X-ray structural analyses which reveals a Ln−O−Al or Ln(μ-OH)Al core in these complexes. The obtuse Ln−O−Al angles fall in the range 151.9−169.8°. The reaction of <b>1</b> or <b>4</b> with Me<sub>3</sub>SnF in toluene under refluxing conditions unexpectedly yielded the compounds [Cp<sub>2</sub>Yb(μ-OSnMe<sub>3</sub>)]<sub>2</sub> (<b>8</b>) and LAl(Me)F (<b>9</b>). Reactions of LAlOH(Me) with the mono- and dicyclopentadienyl complexes LYbCp(Cl) (<b>10</b>) and LYbCp<sub>2</sub> (<b>11</b>) supported by the bulky <i>β</i>-diketiminate ligand were unsuccessful. However, the reaction of LAl(OH)Me with LYbN(SiMe<sub>3</sub>)<sub>2</sub>Cl (<b>12</b>) containing a labile Yb−N bond leads to the formation of LYbCl−O−AlL(Me) (<b>13</b>) under elimination of HN(SiMe<sub>3</sub>)<sub>2</sub>. Furthermore, complexes<b> 1</b>, <b>3</b>, <b>4</b>, and <b>6</b> exhibit good catalytic activity for the polymerization of <i>ε</i>-caprolactone.