Trimethylscandium.

The hitherto unknown homoleptic tetramethylaluminate complex [Sc(AlMe)] could be obtained by reacting the ate complex [LiScMe(thf)] with AlMe in the cold. It cocrystallizes with AlMe as [Sc(AlMe)(AlMe)] and decomposes at ambient temperature in -pentane via multiple C-H bond activations to the mixed methyl/methylidene complex [Sc(μ-CH)(μ-CH)(AlMe)(AlMe)]. Donor-induced methylaluminate cleavage of [Sc(AlMe)(AlMe)] produced [ScMe] in good yield, which could be derivatized with trimethyltriazacyclononane (MeTACN) to form the structurally characterizable [(MeTACN)ScMe]. Additionally, half-sandwich complex [CpSc(AlMe)] and sandwich complex [CpSc(AlMe)] were accessible by salt metathesis reactions from [Sc(AlMe)(AlMe)] and KCp* (Cp* = CMe). Sc NMR spectroscopy was applied as a significant probe to evidence the existence of [ScMe]. Compounds [(MeTACN)ScMe] (+624.6 ppm) and [ScMe(thf)] (+601.7 ppm) gave large Sc NMR shifts, revealing the strong deshielding effect of the σ-bonded alkyl ligands on the scandium nuclei. Ultimately, cationized [Sc(AlMe)(AlMe)] was employed in isoprene polymerization, leading to polymers in high yields (>95%) and with high (>90%) -1,4-polyisoprene content.