Rare-earth-metal trimethylsilylmethyl ate complexes

Abstract

En route to putative rare-earth-metal alkylidene complex Li[Lu(CH₂SiMe₃)₂(CHSiMe₃)], according to Schumann's original protocol, the reaction of YCl₃ with LiCH₂SiMe₃ in a mixture of diethyl ether and n-pentane afforded a neosilyl ate complex of composition Li₃Y(CH₂SiMe₃)₆. Tetrametallic complex Li₃Y(CH₂SiMe₃)₆ shows an unprecedented structural motif in the solid state and was further characterized by heteronuclear ¹H/¹³C/⁷Li/²⁹Si/⁸⁹Y, as well as VT NMR and DRIFT spectroscopies. Analysis of the thermolysis product via heteronuclear NMR spectroscopy and its reactivity towards benzophenone gave strong evidence for an alkylidene formation upon decomposition. Application of a similar protocol for the smallest rare-earth-metal scandium led to the isolation of ate complex [Li(thf)₄][LiSc₂(CH₂SiMe₃)₈] as the preferred crystallized product. Here, the reaction of adduct ScCl₃(thf)₃ and LiCH₂SiMe₃ was performed in Et₂O/n-hexane, in the absence of additional THF. The reaction of LaCl₃(thf) with 3 equiv. of LiCH₂SiMe₃ in THF/Et₂O at −40 °C yielded the ate complex [Li(thf)₄][La(CH₂SiMe₃)₄(thf)], which is the first of its kind.