Synthesis and derivatization of halflanthanidocene aryl(alk)oxide complexes

The reaction of halflanthanidocene aryloxides CpR′Ln(OArtBu,R)2 (Ln = Y, La, Lu; CpR′ = C5Me5, C4Me4H; R = H, Me) and halflanthanidocene alkoxides [(C5Me5)Ln(OCH2CMe3)2]2 (Ln = Y, Lu) with trimethylaluminum (TMA) was investigated. Monomeric CpR′Ln(OArtBu,R)2, derived from the ortho-tBu-substituted OC6H2tBu2-2,6-R-4 (R = H, Me) ligands, form mono(tetramethylaluminate) complexes CpR′Ln(OArtBu,R)(AlMe4) for the smaller lanthanide metal centers yttrium and lutetium. Such an [aryloxide] → [aluminate] ligand exchange was not observed at the larger lanthanum metal center. The mobility of the tetramethylaluminate ligands of complexes CpR′Ln(OArtBu,R)(AlMe4) (Ln = Y, Lu) was examined by variable-temperature (VT) 1H NMR spectroscopy, revealing two signals for bridging and terminal methyl groups at lower temperatures. The treatment of complexes CpR′Ln(OArtBu,R)(AlMe4) with donor solvent d8-THF gave CpR′Ln(OArtBu,R)(Me)(d8-THF)2 (Ln = Y, Lu) with terminal methyl groups, according to a donor-induced aluminate cleavage reaction. Dimeric [(C5Me5)Ln(OCH2CMe3)2]2 (Ln = Y, Lu) was synthesized from (C5Me5)Ln(NiPr2)2(THF) and reacted with two equivalents of TMA per Ln center to yield monomeric bis(TMA) adduct complexes (C5Me5)Ln(OCH2CMe3)2(AlMe3)2(Ln = Y, Lu). VT NMR spectroscopic studies confirmed a high mobility of the Ln(μ-OCH2CMe3)(μ-Me)AlMe2 moieties at an ambient temperature. Both bis(TMA) adduct complexes were characterized by X-ray structure analysis.

Graphical abstractHalflanthanidocene aryloxide and neopentoxide complexes CpR′Ln(OArtBu,R)2 and [(C5Me5)Ln(OCH2CMe3)2]2, respectively, reveal a distinct reaction behavior with trimethylaluminum. Depending on the size of the rare-earth metal center and the stereoelectronic features of the aryl(alk)oxide ligands heterobimetallic complexes with Ln(μ-Me)2AlMe2 and Ln(μ-OR)(μ-Me)AlMe2 moieties are obtained.Figure optionsDownload full-size imageDownload as PowerPoint slide