The hitherto unknown homoleptic tetramethylaluminate complex [Sc(AlMe4)(3)] could be obtained by reacting the ate complex [Li3ScMe6(thf)(1.2)] with AlMe3 in the cold. It cocrystallizes with AlMe3 as [Sc-(AlMe4)(3)(Al2Me6)(0.5)] and decomposes at ambient temperature in n-pentane via multiple C-H bond activations to the mixed methyl/methylidene complex [Sc-3(mu(3)-CH2)(2)(mu(2)-CH3)(3)(AlMe4)(2) (AlMe3)(2)]. Donor-induced methylaluminate cleavage of [Sc(AlMe4)(3)(Al2Me6)(0.5)] produced [ScMe3](n) in good yield, which could be derivatized with trimethyltriazacyclononane (Me(3)TACN) to form the structurally characterizable [(Me(3)TACN)ScMe3]. Additionally, half-sandwich complex [Cp*Sc(AlMe4)(2)] and sandwich complex [Cp-2*Sc(AlMe4)] were accessible by salt metathesis reactions from [Sc-(AlMe4)(3)(Al2Me6)(0.5)] and KCp* (Cp* = C5Me5). Sc-45 NMR spectroscopy was applied as a significant probe to evidence the existence of [ScMe3](n). Compounds [(Me(3)TACN)ScMe3] (+624.6 ppm) and [ScMe3(thf)(x)] (+601.7 ppm) gave large Sc-45 NMR shifts, revealing the strong deshielding effect of the sigma-bonded alkyl ligands on the scandium nuclei. Ultimately, cationized [Sc(AlMe4)(3)(Al2Me6)(0.5)] was employed in isoprene polymerization, leading to polymers in high yields (>95%) and with high (>90%) cis-1,4-polyisoprene content.
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