来源：ACS Publications
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.
We have recently launched a study on how the type of group 13 metal might affect the formation of Lewis-acid stabilized rare-earth-metal complexes with multiply bonded main group fragments/ligands. For example, homoleptic gallates Ln(GaMe4)3 (Ln = Ce, Nd, Sm) gave access to terminal imides while the respective aluminates afforded Lewis acid stabilized imides exclusively. In this work, we report on the synthesis of the first scandium tetramethylgallate and tetramethylindate complexes Cp*2Sc(EMe4) (E = Ga, In) using a donor-assisted tetramethylaluminate/tetramethyltrielate exchange protocol. Such transformations driven by Pearsoǹs HSAB concept routinely suffer from incomplete exchange, which means that the products Cp*2Sc(EMe4) (E = Ga, In) still contained residual aluminum. Pursuing the above-mentioned C–H-bond activation chemistry, established previously for larger rare-earth metals, we found that thermal treatment of Cp*2Sc(EMe4) (E = Al, Ga, In) led favorably to internal methyl ligand deprotonation rather than external benzene activation. From these reactions, methylidene clusters of the type Cp*6Sc4E8(CH2)12Me6 (E = Ga, In) could be isolated.