Scandium bis(trimethylsilyl)methyl complexes revisited: extending the Sc NMR chemical shift range and a new structural motif of Li[CH(SiMe)].

Depending on the molar ratio employed, the reaction of ScCl(thf) with Li[CH(SiMe)] afforded the bis and tris(alkyl) ate complexes [Sc{CH(SiMe)}(μ-Cl)Li(thf)] and ScCH(SiMe)Li(thf), respectively, in moderate yields. Treatment of these mixed alkyl/chlorido complexes with MeLi gave the mixed alkyl complexes [Sc{CH(SiMe)}(μ-Me)Li(thf)] and ScCH(SiMe)Li(thf). Aiming at homoleptic {Sc[CH(SiMe)]} both of the mixed [CH(SiMe)]/Me complexes were treated with AlMe. Although LiAlMe separation occurred, aluminium complex Al[CH(SiMe)]Me(thf) was the only isolable crystalline complex. Ate complexes [Sc{CH(SiMe)}(μ-Me)Li(thf)] and [Sc(CHSiMe)][Li(thf)] revealed the maximum downfield Sc NMR chemical shifts of 888.0 and 933.4 ppm, respectively, reported to date. The synthesis of putative {Sc[CH(SiMe)]} was also attempted via the aryloxide route applying complexes Sc(OCHtBu-2,6-Me-4) and [Sc(OCHiPr-2,6)] along with Li[CH(SiMe)] but the outcome was inconclusive. Instead, a cyclic octamer was found for Li[CH(SiMe)] in the solid state.