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 3 (thf) 3 with Li[CH(SiMe 3 ) 2 ] afforded the bis and tris(alkyl) ate complexes [Sc{CH(SiMe 3 ) 2 } 2 (μ-Cl) 2 Li(thf) 2 ] 2 and Sc[CH(SiMe 3 ) 2 ] 3 (μ-Cl)Li(thf) 3 , respectively, in moderate yields. Treatment of these mixed alkyl/chlorido complexes with MeLi gave the mixed alkyl complexes [Sc{CH(SiMe 3 ) 2 } 2 (μ-Me) 2 Li(thf) 2 ] 2 and Sc[CH(SiMe 3 ) 2 ] 3 (μ-Me)Li(thf) 3 . Aiming at homoleptic {Sc[CH(SiMe 3 ) 2 ] 3 } both of the mixed [CH(SiMe 3 ) 2 ]/Me complexes were treated with AlMe 3 . Although LiAlMe 4 separation occurred, aluminium complex Al[CH(SiMe 3 ) 2 ]Me 2 (thf) was the only isolable crystalline complex. Ate complexes [Sc{CH(SiMe 3 ) 2 } 2 (μ-Me) 2 Li(thf) 2 ] 2 and [Sc(CH 2 SiMe 3 ) 4 ][Li(thf) 4 ] revealed the maximum downfield 45 Sc NMR chemical shifts of 888.0 and 933.4 ppm, respectively, reported to date. The synthesis of putative {Sc[CH(SiMe 3 ) 2 ] 3 } was also attempted via the aryloxide route applying complexes Sc(OC 6 H 2 t Bu 2 -2,6-Me-4) 3 and [Sc(OC 6 H 3 i Pr 2 -2,6) 3 ] 2 along with Li[CH(SiMe 3 ) 2 ] but the outcome was inconclusive. Instead, a cyclic octamer was found for Li[CH(SiMe 3 ) 2 ] in the solid state. Scandium mixed alkyls form readily via subsequent treatment of ScCl 3 with Li[CH(SiMe 3 ) 2 ] and LiMe, as probed by 45 Sc NMR spectroscopy.