Synthesis of Rare-Earth-Metal Iminopyrrolyl Complexes
from Alkyl Precursors: Ln→Al N‑Ancillary Ligand Transfer
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Abstract
Protonolysis
of [YMe<sub>3</sub>]<sub><i>n</i></sub> with
2-{(N-2,6-dialkylphenyl)iminomethyl)}pyrroles (alkyl = <i>i</i>Pr (L<sup>1</sup>), Me (L<sup>2</sup>)) gave homoleptic iminopyrrolyl
complexes YL<sup>1</sup><sub>3</sub> and YL<sup>2</sup><sub>3</sub> as well as the complex [L<sup>2</sup>YL<sup>2,Me</sup>]<sub>2</sub> containing a dianionic pyrrolaldiminato ligand, formed via methylation
of the imino backbone. Treatment of the half-sandwich complex [(C<sub>5</sub>Me<sub>5</sub>)YMe<sub>2</sub>]<sub>3</sub> and yttrocene
(C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>YMe(THF) with either 2 or
1 equiv of HL afforded the monomeric complexes (C<sub>5</sub>Me<sub>5</sub>)YL<sub>2</sub> and (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>YL,<b> </b>respectively. The complex (C<sub>5</sub>Me<sub>5</sub>)YL<sup>2</sup><sub>2</sub> readily underwent Ln→Al iminopyrrolyl
ligand transfer in the presence of trimethylaluminum, producing the
known (C<sub>5</sub>Me<sub>5</sub>)Y(AlMe<sub>4</sub>)<sub>2</sub>. Salt metatheses of homoleptic Ln(AlMe<sub>4</sub>)<sub>3</sub> (Ln
= Y, La) with KL gave complicated reaction mixtures from which the
η<sup>5</sup>/η<sup>1</sup>:κ<sup>1</sup> pyrrolaldiminato-bridged
complex [L<sup>1,Me</sup>La(AlMe<sub>4</sub>)]<sub>2</sub> and bis(tetramethylaluminate)
complex L<sup>2</sup>Y(AlMe<sub>4</sub>)<sub>2</sub> could be isolated
and crystallographically characterized. Moreover, the solid-state
structures of YL<sup>2</sup><sub>3</sub>, [L<sup>2</sup>YL<sup>2,Me</sup>]<sub>2</sub>, (C<sub>5</sub>Me<sub>5</sub>)YL<sup>1</sup><sub>2</sub>, (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>YL<sup>1</sup>, and L<sup>2</sup>AlMe<sub>2</sub> are presented
