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.

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.

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