Scandium─Group 13 Heterobimetallic Methylidene Clusters

A straightforward synthesis of Cp*₂Sc(AlMe₄) (Cp* = C₅Me₅) applying Cp*₂ScCl(thf) and LiAlMe₄/AlMe₃ is described. Donor-assisted trimethyltriel exchange gives access to Cp*₂Sc(EMe₄) (E = Ga, In), which represent the first scandium tetramethylgallate and tetramethylindate complexes. Thermal treatment of Cp*₂Sc(EMe₄) (E = Ga, In) in benzene leads to the isolation of methylidene clusters Cp*₆Sc₄E₈(CH₂)₁₂Me₆ (E = Ga, In). This methyl group deprotonation differs from the benzene activation previously observed for Cp*₂Y(EMe₄) (E = Al, Ga). Treatment of Cp*₂Sc(EMe₄) (E = Al, Ga) with excess GaMe₃ in benzene at elevated temperatures generated Ga₈(CH₂)₁₂, following the known reactivities of Cp*₂Ln(GaMe₄) (Ln = Y, Lu) with GaMe₃. Analogous reactions of scandocene complexes Cp*₂Sc(EMe₄) (E = Al, In) with excess InMe₃ at elevated temperatures did not yield the putative homoleptic indium methylidene. Instead, the methylidene cluster Cp*₄Sc₄In₈(CH₂)₁₂Me₈ was isolated, which features half-sandwich scandium fragments exclusively. A reaction of InMe₃ and HCp* at high temperatures yielded Me₂InCp*InMe₃, which might incorporate the missing Cp* ligands in the cluster formations. Rare-earth-metal compounds were analyzed by SC-XRD, ICP-OES and elemental analysis. Compounds Cp*₂Sc(EMe₄) (E = Ga, In) and [Cp*₂Sc(ClAlMe₃)]₂ were additionally analyzed by ¹H, ¹³C{¹H}, ⁴⁵Sc NMR as well as ¹H and ⁴⁵Sc variable temperature NMR studies.