Synthesis and derivatization of halflanthanidocene aryl(alk)oxide complexes

Abstract

The reaction of halflanthanidocene aryloxides Cp R′Ln(OAr tBu,R ) 2 (Ln = Y, La, Lu; Cp R′ = C 5Me 5, C 4Me 4H; R = H, Me) and halflanthanidocene alkoxides [(C 5Me 5)Ln(OCH 2CMe 3) 2] 2 (Ln = Y, Lu) with trimethylaluminum (TMA) was investigated. Monomeric Cp R′Ln(OAr tBu,R ) 2, derived from the ortho- tBu-substituted OC 6H 2 tBu 2-2,6-R-4 (R = H, Me) ligands, form mono(tetramethylaluminate) complexes Cp R′Ln(OAr tBu,R )(AlMe 4) 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 Cp R′Ln(OAr tBu,R )(AlMe 4) (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 Cp R′Ln(OAr tBu,R )(AlMe 4) with donor solvent d 8-THF gave Cp R′Ln(OAr tBu,R )(Me)( d 8-THF) 2 (Ln = Y, Lu) with terminal methyl groups, according to a donor-induced aluminate cleavage reaction. Dimeric [(C 5Me 5)Ln(OCH 2CMe 3) 2] 2 (Ln = Y, Lu) was synthesized from (C 5Me 5)Ln(N iPr 2) 2(THF) and reacted with two equivalents of TMA per Ln center to yield monomeric bis(TMA) adduct complexes (C 5Me 5)Ln(OCH 2CMe 3) 2(AlMe 3) 2(Ln = Y, Lu). VT NMR spectroscopic studies confirmed a high mobility of the Ln(μ-OCH 2CMe 3)(μ-Me)AlMe 2 moieties at an ambient temperature. Both bis(TMA) adduct complexes were characterized by X-ray structure analysis.