Synthesis of Rare-Earth-Metal Iminopyrrolyl Complexes from Alkyl Precursors: Ln→Al N‑Ancillary Ligand Transfer

Protonolysis of [YMe3]n with 2-{(N-2,6-dialkylphenyl)­iminomethyl)}­pyrroles (alkyl = iPr (L1), Me (L2)) gave homoleptic iminopyrrolyl complexes YL13 and YL23 as well as the complex [L2YL2,Me]2 containing a dianionic pyrrolaldiminato ligand, formed via methylation of the imino backbone. Treatment of the half-sandwich complex [(C5Me5)­YMe2]3 and yttrocene (C5Me5)2YMe­(THF) with either 2 or 1 equiv of HL afforded the monomeric complexes (C5Me5)­YL2 and (C5Me5)2YL, respectively. The complex (C5Me5)­YL22 readily underwent Ln→Al iminopyrrolyl ligand transfer in the presence of trimethylaluminum, producing the known (C5Me5)­Y­(AlMe4)2. Salt metatheses of homoleptic Ln­(AlMe4)3 (Ln = Y, La) with KL gave complicated reaction mixtures from which the η5/η1:κ1 pyrrolaldiminato-bridged complex [L1,MeLa­(AlMe4)]2 and bis­(tetramethylaluminate) complex L2Y­(AlMe4)2 could be isolated and crystallographically characterized. Moreover, the solid-state structures of YL23, [L2YL2,Me]2, (C5Me5)­YL12, (C5Me5)2YL1, and L2AlMe2 are presented.