Rare-Earth\nDialkyls Supported by Silaimine-Cp Ligand:\nSynthesis, Reactivity, and Catalytic Addition of Alkynes and Amines\nto Carbodiimides

Rare-earth metal dialkyls have attracted considerable\nattention\nin a variety of chemical transformations, such as hydroelementation\nof unsaturated substrates and olefin polymerization. However, stable\nrare-earth dialkyls are still very limited in number because of their\npoor thermal stability. In this paper, silaimine-functionalized cyclopentadienyl\nligands C<sub>5</sub>Me<sub>4</sub>H–Si(L)NR (L = PhC(N<i>t</i>Bu)<sub>2</sub> and R = 2,6-<i>i</i>Pr<sub>2</sub>C<sub>6</sub>H<sub>3</sub> for <b>1</b> and SiMe<sub>3</sub> for <b>2</b>) were applied for the synthesis of yttrium and\nscandium dialkyls (<b>3–5</b>). σ-Bond metathesis\nreactions of silaimine-Cp yttrium dialkyl <b>3</b> with aniline\nand 2,6-dimethylpyridine yielded the yttrium diamide complex (<b>6</b>) and the C(sp<sup>3</sup>)–H bond-activated yttrium\ndibenzyl complex (<b>7</b>), respectively. The yttrium diamidinate\ncomplex (<b>8</b>) was generated from the reaction of <b>3</b> with <i>N</i>,<i>N</i>′-diisopropylcarbodiimide.\nThe yttrium and scandium dialkyls <b>3</b> and <b>5</b> and the reaction products <b>6-thf</b>, <b>7</b>, and <b>8</b> have been structurally characterized by X-ray diffraction\nanalysis. Notably, silaimine-Cp yttrium dialkyl <b>4</b> displayed\nhigh activity and excellent functional group tolerance in the catalytic\naddition of terminal alkynes and amines to carbodiimides.