# ScandiumGroup 13 Heterobimetallic Methylidene Clusters

## TL;DR

Scientists synthesized new scandium-based clusters with unique structures using chemical reactions involving methyl groups and metal complexes.

## Contribution

The first synthesis of scandium tetramethylgallate and tetramethylindate complexes and novel methylidene clusters with unique structural features.

## Key findings

- Cp*2Sc(EMe4) complexes (E = Ga, In) were synthesized and characterized as first-of-their-kind scandium derivatives.
- Thermal treatment of Cp*2Sc(EMe4) in benzene produced methylidene clusters Cp*6Sc4E8(CH2)12Me6 (E = Ga, In).
- Reactions with InMe3 led to a methylidene cluster with exclusive half-sandwich scandium fragments.

## Abstract

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.